Effect of elemental sulfur supplementation on rumen environment parameters and utilization efficiency of fresh cassava foliage and cassava hay in dairy cattle.
|Abstract:||Effect of sulfur (S) on utilization efficiency of fresh cassava foliage and cassava hay in dairy cows was evaluated using thirty-two 1st-2nd lactation Holstein-Friesian crossbred dairy cows. The experimental treatment was a 2x2 factorial arrangement in a randomized complete block design (RCBD) using two roughages (rice straw+fresh cassava foliage (FCF) and rice straw+cassava hay (CH)) and two elemental sulfur (S) levels (0.15 and 0.4% S of dry matter (DM)), respectively. Four dietary treatments (FCF+0.15, FCF+0.4, CH+0.15 and CH+0.4) were offered ad libitum in the form of a total mixed ration (TMR) with concentrate to roughage (chopped rice straw+chopped cassava foliage) ratio at 60:40. Fresh cassava foliage or cassava hay resulted in similar dry mater intake, rumen ecology parameters, total tract digestibility, blood chemistry, milk production and composition. However, HCN intake, blood and milk thiocyanate concentration were significantly higher (p<0.01) in cows fed fresh cassava foliage with no sign of potential toxicity. Dry matter intake, body weight changes, molar percentage of propionate in rumen, neutral detergent fiber (NDF) digestibility and nitrogen (N) retention of cows tended to be increased while DM digestibility (65.6, 72.7, 68.6 and 72.1% of total DM intake for the respective treatments), rumen bacteria population (1.4, 1.7, 1.6 and 1.7x [10.sup.11] cell/ml for respective treatments), fungal zoospore population (0.4, 0.6, 0.4 and 0.5x [10.sup.6] cell/ml for respective treatments), urinary allantoin (25.3, 28.0, 26.3 and 27.6 g/d for respective treatments), microbial N yield (136.0, 154.6, 142.8 and 151.3 g N/d for respective treatments) and milk protein content (3.4, 3.5, 3.2 and 3.5% for respective treatments) were significantly (p<0.05) higher in cows fed on supplemented sulfur at 0.4% of DM in comparison with 0.15% S-supplemented diets. Based on these results, it is concluded that cassava foliage could be used as a portion of roughage for dairy cows and supplementation of S would be nutritionally beneficial. (Key Words: Fresh Cassava Foliage, Sulfur, Cassava Hay, Hydrogen Cyanide, Dairy Cow)|
(Food and nutrition)
Feed utilization efficiency (Methods)
Medicated feeds (Research)
Sulfates (Dosage and administration)
|Publication:||Name: Asian - Australasian Journal of Animal Sciences Publisher: Asian - Australasian Association of Animal Production Societies Audience: Academic Format: Magazine/Journal Subject: Agricultural industry; Biological sciences Copyright: COPYRIGHT 2009 Asian - Australasian Association of Animal Production Societies ISSN: 1011-2367|
|Issue:||Date: Oct, 2009 Source Volume: 22 Source Issue: 10|
|Topic:||Event Code: 310 Science & research|
|Product:||Product Code: 0240100 Dairy Cattle; 0240110 Dairy Cows; 0134300 Cassava NAICS Code: 11212 Dairy Cattle and Milk Production; 111998 All Other Miscellaneous Crop Farming SIC Code: 0241 Dairy farms; 0139 Field crops, except cash grains, not elsewhere classified; 2819 Industrial inorganic chemicals, not elsewhere classified|
|Geographic:||Geographic Scope: Thailand Geographic Code: 9THAI Thailand|
Feeding of dairy cattle in the tropics is often difficult because of deficiencies in feed supply, in both quality and quantity (Wanapat and Devendra, 1992). The use of rice straw as a feed in the dry season, in spite of its low nutritive value, has been a common feeding system, generally practiced by dairy farmers in the tropics when green forages are often scarce (Leng and Preston, 1983; Wanapat, 1994). Chemical treatment of rice straw to improve its quality has been reported (Wanapat et al., 1990). The development and utilization of cassava hay (cassava whole crop at a young growth stage, 3-4 months, harvested about 30-45 cm above ground, and sun-dried for 1-2 days until having a final dry matter of at least 85%, Wanapat, 1999; 2003) as an on-farm feed has been recommended as a possible solution to the lack of good-quality roughages during the dry season in the tropics (Wanapat et al., 1997). The cassava hay contains high protein, 20-27% CP, and condensed tannins, 1.5-4%. The use of cassava hay at 0.56 to 1.70 kg/head/d or about 0.1 to 0.5% BW was proved to be an excellent ruminant protein feed (Wanapat, 1999; 2003; Promkot et al., 2007). The use of cassava hay has been successfully implemented in several ways by either direct feeding or as a protein source in concentrate mixtures (Wanapat et al., 2000abc; Hong et al., 2003; Kiyothong and Wanapat, 2004; Wanapat et al., 2007; Chantaprasarn and Wanapat, 2008), in combination as a pellet of cassava hay, soybean meal and urea (Wanapat et al., 2006) or inclusion in a high quality feed block (Wanapat and Khampa, 2006).
However, there was a lack of information on feeding fresh cassava foliage as a supplement to ruminants, especially for dairy cows. During the rainy season, it is difficult to make cassava hay, therefore feeding fresh cassava foliage to ruminants could be a possible alternative method. However, cassava foliage, especially fresh cassava, contains cyanogenic glucosides, linamarin and lotaustralin. After tissue damage, these are hydrolyzed by the endogenous enzyme linamarase to cyanohydrins. Further hydrolysis to HCN is responsible for chronic toxicity. In ruminants, HCN can be rapidly detoxified by rhodanase and [beta]-mercaptopyruvate sulfurtransferase (Martensson and Sorbo, 1978; Frankenberg, 1980) by rumen microbes (Majak and Cheng, 1984) and animal tissue (rumen wall, liver, kidney and red blood cell) (Aminlari and Gilapour, 1991; Aminlari et al., 1989). Rhodanase is a sulfur transferase that catalyses the formation of thiocyanate from cyanide and thiosulphate or other suitable sulfur donor, and then the less toxic thiocyanate is excreted in the urine.
The main sources of sulfur for HCN detoxification are the sulfur amino acids, cystein and methionine, or elemental sulfur (Oke, 1978). Detoxification of cyanide into SCN causes an increased demand for sulfur-containing amino acids (Maner and Gomez, 1973). NRC (2001) also mentions that the sulfur requirement of dairy cattle consuming cyanogenic plants (such as cassava or sorghum) may be increased because of the need for sulfur in the detoxification of cyanogenic glucosides. Hence, the hypothesis behind this study was that feeding fresh cassava foliage or cassava hay (10% in total ration) combined with adequate sulfur could provide good sources of protein for milk production in dairy cattle with no toxic effects from cyanide. Therefore, the objective of this study was to evaluate the effect of sulfur on utilization efficiency of fresh cassava foliage and cassava hay in milking dairy cows, on i) rumen pH, ammonia nitrogen, total volatile fatty acids, cyanide concentration and microflora population and microbial protein synthesis ii) nutrient digestibility iii) serum concentration of urea nitrogen, thiocyanate, thyroid gland hormones and liver enzymes and iv) milk production and composition.
MATERIALS AND METHODS
Thirty-two, 1st-2nd lactation Holstein-Friesian crossbred dairy cows, ranging from 100-150 days-in-milk (DIM) with 12-15 kg/d milk yield, from the dairy farm of the Faculty of Natural Resources, Rajamangala University of Technology Isan, Sakon Nakhon Campus were used in a randomized complete block design (RCBD) to determine the effects of sulfur on utilization efficiency of fresh cassava foliage and cassava hay. The experiment was arranged in two periods (30 days each) using 16 cows for each period. Treatments were total mixed rations with two levels of sulfur and supplemented with a similar amount (10% dry matter in the diet) of two roughages (fresh cassava foliage and cassava hay). Treatments were as follows: T1: 0.15% S, 10% FCF; T2: 0.40% S, 10% FCF; T3: 0.15% S, 10% CH; and T4: 0.40% S, 10% CH. Summary of treatment feeds (total mixed rations, TMR) and animals in the experiment are shown in Table 1.
Feeds and cows management
Feed ingredient compositions of concentrate and cassava foliage are shown in Table 2. Whole fresh cassava foliage crop (variety Rayong 72, bitter variety) was harvested about 30-45 cm above ground (at the point where the woody stem changes to the green stem) at a young growth stage, 3-4 months, at the university farm once a day in the morning (07:00 am) throughout the experimental period and kept in the cool room (4[degrees]C) for fresh cassava foliage until total mixed rations (TMR) were provided. The cassava foliage crop (variety Ryong 72) was also harvested for making cassava hay according to the method of Wanapat et al. (1997, 2000ab). In brief, cassava foliage was chopped and sun-dried for 1-2 days until having final dry matter of at least 85%. Concentrate and roughage (30% chopped rice straw and 10% chopped FCF or CH) feeds were provided every day (09:00 am and 15:00 pm) in the form of a total mixed ration (TMR) with concentrate:roughage at 60:40 by using a mixing machine, and water was added to obtain TMR moisture at an average 45-50%.
The TMR diets were formulated for two levels of S and two supplemental roughages (FCF and CH), and made isocaloric (TDN) and iso-N for crude protein (CP). The composition of the TMR diets is shown in Table 3. Cows were housed individually for each treatment and had ad libitum access to a TMR (TMR was offered three times a day), fresh water and mineral block. Cows were milked twice daily by milking machine. The cows were adjusted for the first two weeks, and actual intake and measurements were taken subsequently during the experimental 30 days of milk collection.
Feed, feces, rumen fluid and blood samplings
Feed intakes were recorded daily. Feed, feces and urine were collected during the last 5 days of each period. Feed (fresh feed offered and feed residues) was randomly collected (250 g) once a day in the morning before new fresh feed was offered and was kept in a refrigerator until analysis.
Four cows from each treatment in each period were randomly selected for metabolism crates for total collection of feces to measure nutrient digestibility and volume of urine excretion. Feces and urine were collected daily before the morning feeding and were weighed to determine output; a 1% subsample of urine and a 3% subsample of feces were collected, composited by period and stored at -20[degrees]C until later analysis. Urine was collected into a plastic container with a suitable amount of 50% [H.sub.2]S[O.sub.4] to reduce pH to <2.5. An additional urine subsample was collected daily, immediately diluted, and stored at -20[degrees]C for analysis of purine derivatives (PD), a marker of ruminal bacteria production.
Rumen fluid and blood samples were collected at 0 and 4 h-post feeding on the last day of each period. About 100 ml of whole rumen fluid was collected by stomach tube from individual cows and pH was determined immediately after collection using a glass electrode pH meter. Ruminal fluid samples were then filtered through four layers of cheesecloth and were centrifuged (3,000xg, 4[degrees]C for 15 min) immediately and the supernatant was divided into two parts. The first 50 ml rumen fluid portion was kept in a plastic bottle to which 5 ml of 1 M [H.sub.2]S[O.sub.4] was added and stored at -20[degrees]C to be used later for N[H.sub.3]-N and VFA analysis. The second portion of 1 ml rumen fluid was kept in a plastic bottle to which 9 ml of 10% formalin solution was added and stored at 4[degrees]C to be used later for total direct count of bacteria, protozoa and fungal zoospores. Blood samples were taken from a coccygeal vessel into heparinized Vacutainer tubes and centrifuged immediately to separate plasma that was stored at -20[degrees]C before analysis. Milk yields of each cow were recorded daily. Milk samples of 60 ml (in a ratio of morning milk samples:afternoon milk samples of 60:40) were collected twice daily during milking (05.00 and 17.00 h) on the last five days of each period for later chemical analysis.
Feed (both fresh feed offered and feed residues) and fecal samples were analyzed for DM, ash, CP (AOAC, 1990), NDF and ADF (Goering and Van Soest, 1970). Hydrogen cyanide content of feed and cassava foliage was determined spectrophotometrically (SpectroSC, LaboMed, inc. USA) with 2, 4-quinolinediol-pyridine reagent (Lambert et al., 1975). In brief, feed (TMR, CH, FCF) was extracted with 0.1 M phosphoric acid and the acid extract (feed material was removed by filtration) hydrolyzed in 2 M [H.sub.2]SO4 at 100[degrees]C for 50 minutes (Bradbury et al., 1991). To 4.0 ml of the acid solution was added 5 ml of 3.6 M NaOH, after which the solution was filtered. After five minutes, a 1 ml aliquot was taken for colorimetric determination of cyanide by modified Konig reactions (Lambert et al., 1975).
Rumen fluid samples were analyzed for N[H.sub.3]-N using the procedure of AOAC (1990), and for VFA using high performance liquid chromatography (HPLC; Model Water 600; UV detector, Millipore Crop) according to the method of Samuel et al. (1997). Total direct counts of bacteria, protozoa and fungal zoospores content of rumen fluid were done according to the method of Galyean (1989).
Plasma samples were analyzed for urea-nitrogen composition (BUN), alanine aminotransferase (ALT), aspartate aminotransferase (AST), triiodothyronine (T3), and thyroxine ([T.sub.4]) using automated clinical chemistry analyzers (Vitallab Flexor E). Thiocyanate was analysed using the method of Lambert et al. (1975). Plasma samples (1 ml) were added to 3 ml 15% w/v trichloroacetic acid and centrifuged for 15 min at 1,000 g. One milliliter of supernatant was used for the colorimetric procedure with 2, 4-quinolinediol-pyridine as the coupling reagent (Lambert et al., 1975). Milk samples were analyzed for fat, protein, lactose and solids-not-fat using infared apparatus (Milkoscan 104, Foss Electric, Denmark). A sub-sample of the composite was analyzed for milk urea nitrogen according to the method of Roseler et al. (1993), using a Sigma diagnostics kit #535 reading at 540 nm using a spectrophotometer (Spectonic 20, Milton Roy company, USA), and milk thiocyanate was analysed using the method of Lambert et al. (1975). One milliliter of milk sample was added to 3 ml 15% w/v trichloroacetic acid and centrifuged for 15 min at 1,000 g. One milliliter of supernatant was used for the colorimetric procedure with 2, 4-quinolinediolpyridine as the coupling reagent (Lambert et al., 1975).
Urinary ammonia N was measured using the procedure of AOAC (1990). Purine derivatives were measured in urine by HPLC (Waters Model 600; UV detector, Millipore Corp) according to the method of Chen et al. (1993).
Data were analyzed using the GLM Procedure (SAS, 1996). The following models were used to determine treatment mean differences using Duncan's New Multiple Range Test.
RESULTS AND DISCUSSION
Chemical composition of feed
The values for composition of feed ingredients are shown in Table 2 and 3. The chemical compositions of cassava hay and fresh cassava foliage were in the range reported in the literature (Wanapat et al., 2000a; Man and Wiktorsson, 2001; Wiktorsson and Man, 2002; Wanapat, 2003; Kiyothong and Wanapat, 2004; Wiktorsson and Khang, 2004; Wanapat et al., 2006). These values would be expected to support normal performance of these lactating cows.
Dry matter intake, digestibility and body weight change
Daily DM intake did not differ significantly among treatments but there was an increasing trend when sulfur was supplemented in the diet (p = 0.065) (Table 4). These results could be due to significant increase (p<0.05) in dry matter digestibility, especially in the fresh cassava foliage fed group when sulfur was supplemented. Hydrocyanic acid (HCN) intake was highly significant (p<0.01) in cows fed fresh cassava foliage (but no toxic signs were evident) than in cassava hay due to a higher level of HCN in the former, similar to the findings of Ravindran et al. (1987) and Promkot et al. (2007).
Cassava foliage (fresh or hay) and interaction of cassava foliage and sulfur did not affect nutrient digestibility (Table 4) with the exception of DM digestibility which was higher (p<0.05) in animals fed 0.4% S than in those fed 0.15% S. Moreover, ADF digestibility tended to be higher in cows fed fresh cassava foliage with 0.4% S as compared to other treatments. This result could be attributed to increased numbers of rumen bacteria and fungal zoospores in animals fed with supplemental sulfur at 0.4% DM as compared with 0.15% S diets, leading to increased fiber digestibility. The cows fed cassava foliage with high content of HCN might require increased sulfur supplement, in order to facilitate S for detoxification into thiocyanate (NRC, 2001). Therefore it is possible that the ration of 0.15% S might be deficient in sulfur content especially for the diet with fresh cassava foliage. Therefore, sulfur supplementation to a ruminant ration deficient in sulfur could increase numbers of cellulolytic bacteria (Slyter et al., 1986) which could increase fiber digestibility (Bull, 1984), digestibility of cellulose and lignocellulose (Barton et al., 1971), feed intake (Bouchard and Conrad, 1973) or feed utilization (Garrigus et al., cited by Goodrich et al., 1978).
The negative effect of the cassava foliage with 0.15% S diet on body weight condition in the present study may have been due to reduction in muscular development as a result of depletion of the sulfur-containing amino acids necessary for formation of S amino acids as well as for cyanide detoxification (Onwuka et al., 1992). Similar results were reported by Onwuka et al. (1992) who indicated that goats on a low sulfur cassava-based diet had the greatest weight losses as compared to S-supplemented groups. They proposed that a dietary level of 0.5% elemental S ensured adequate cassava cyanide detoxification in sheep and goats.
Cassava foliage, supplementation of sulfur and their interactions did not affect rumen ecology, namely rumen pH, ammonia nitrogen, and total volatile fatty acids. Similar findings were reported by deOliveira et al. (1996) that moderately high percentages of sulfur (0.4 to 0.6%) in the diet generally had no effects on ruminal VFA and ammonia-nitrogen concentrations. Qi et al. (1993) indicated that ruminal fluid ammonia nitrogen was not affected by added sulfur. Similar findings were also reported by Wora-anu et al. (2004; 2007) that cattle fed cassava hay or fresh cassava foliage had no effects on ruminal pH, VFA and ammonia-nitrogen concentrations.
The molar percentage of propionate exhibited an increasing trend when sulfur was supplemented in the diet (p = 0.081) (Table 5). This finding is supported by Thompson et al. (1972) and Zinn et al. (1997) who reported increased ruminal propionate in feedlot cattle or Holstein steers when dietary sulfur was increased from 0.12 to 0.37 and 0.15 to 0.25%, respectively. Low rumen propionate concentration can occur when ruminants are fed sulfur-deficient diets (Goodrich et al., 1978), because little lactate is converted to propionate via the acrylate pathway (Goodrich et al., 1978). It is hypothesized that in cattle fed with cassava foliage, rumen microbes might need more sulfur for hydrogen cyanide detoxification (Onwuka et al., 1992; Promkot et al., 2007) leading to sulfur-deficiency in cattle fed a low sulfur diet that might result in low rumen propionate concentration.
Rumen bacteria were significantly (p<0.05) higher in animals fed with supplemental sulfur at 0.4% of DM in comparison with 0.15% S diets. Similar results were reported by by dePaiva (2007) that a dose of 0.31% sulfur could increase the rumen microorganisms (including protozoa) in heifers. Slyter et al. (1986) reported that there were reduced numbers of cellulolytic bacteria in sulfur-deficient sheep (0.04% S) in comparison to sulfur-supplemented sheep (0.34% S). Sulfur is one of many important factors for microbial growth (Leng and Preston, 1983). Low levels of sulfur supplementation in the diet containing cassava foliage could reduce microbial biomass in the rumen (Promkot et al., 2007).
Fungal zoospore population was significantly (p<0.05) higher in animals fed with supplemental sulfur at 0.4% of DM in comparison with 0.15% S diets. Cassava foliage (hay or fresh) and interaction of cassava foliage and sulfur did not affect the population of rumen microbes; however, there was a trend (p = 0.085) for higher fungal zooospores in animals fed fresh cassava foliage with 0.4% S in the diet. Ruminal fungi concentrations and activity may be increased by supplementation with a variety of sulfur sources (Morrison et al., 1990; Gutierrez et al., 1996). In Australia, sulfur-fertilized grass (Akin et al., 1983) and a methionine-supplemented diet (Gordon et al., cited by Akin and Borneman, 1990) resulted in increased fungal populations. Under this study it was also found that there were higher fungal zoospore populations in animals fed a 0.4% S diet as compared with 0.15% S. In addition, similar work conducted by Orpin and Greenwood (1986) reported that N. patriciarum required a reduced form of sulfur.
Blood metabolites and hormones
Cassava foliage (hay or fresh) and sulfur supplementation had no effect on blood chemistry, namely BUN, T3, T4, ALT, and AST (Table 7). BUN concentration is positively correlated with ruminal ammonia nitrogen (Hammond, 1983; Promkot and Wanapat, 2005). This study also found that treatment with higher ruminal ammonia nitrogen resulted in higher BUN. Thyroid hormones and liver enzymes were in normal physiological ranges (Table 6) which indicated that feeding fresh cassava foliage or cassava hay at 10% of the diet did not damage the liver and thyroid gland. Similar findings have been reported by Khang and Wiktorsson (2004) that 11% of total DMI as fresh cassava foliage did not affect liver enzymes and triiodothyronine and thyroxine concentrations of the thyroid gland in local yellow cattle. Soto-Blanco et al. (2001) also found that the level of thyroid hormones was unaffected when lactating goats were orally dosed with 3 mg/kg/d KCN for 90 days.
The concentrations of SCN in plasma were significantly greater (p<0.01) in cows given fresh cassava foliage diets than in cows on the cassava hay diet (p<0.01) (Table 7). The increased levels of thiocyanate in plasma of cows fed fresh cassava foliage in this study were due to a relative increase of HCN consumption which was furthered detoxified to thiocyanate (Martensson and Sorbo, 1978; Frankenberg, 1980). Within the fresh cassava foliage and cassava hay diets, the overall concentrations of SCN in plasma were much higher (p<0.01) when cows were fed with 0.4% S than when fed with 0.15% S, especially in cows fed with fresh cassava foliage. However, there was an interaction (p<0.05) effect between cassava foliage and S treatments on plasma SCN concentrations and the highest plasma SCN concentrations were found in animals fed 0.4% S and fresh cassava foliage. This finding indicated that sulfur supplementation could increase HCN detoxification (thiocyanate is a metabolic product of cyanide detoxification) in dairy cows fed with cassava foliage. Similar findings were reported by Promkot et al. (2007) who reported that sulfur can stimulate the rate of HCN detoxification by rumen microbes. Onwuka et al. (1992) also similarly found that percentage of S in the diet was correlated with serum SCN when sheep were fed a dried cassava-based diet.
In ruminants, HCN can be rapidly detoxified by rhodanase and [beta]-mercaptopyruvate sulfurtransferase (Martensson and Sorbo, 1978; Frankenberg, 1980) by rumen microbes (Majak and Cheng, 1984; Promkot et al., 2007) and animal tissues (rumen wall, liver, kidney and red blood cell) (Aminlari and Gilapour, 1991; Aminlari et al., 1989). Rhodanase is a sulfur transferase that catalyses the deformation of cyanide and thiosulphate, or other suitable sulfur donor, to less toxic thiocyanate which is secreted into the blood steam and futher excreted in the milk and urine. The main source of sulfur for HCN detoxification is sulfur amino acid, cysteine and methionine, or elemental sulfur (Oke, 1978). Therefore, adding sulfur to feeds containing
HCN is essential for HCN detoxification.
Nitrogen metabolism data are summarized in Table 8. Nitrogen intake and fecal N output were not different across the treatment diets and urinary N output tended to be increased (p = 0.068) as a result of supplemental S. Nitrogen retention (g/d and as a percentage of intake) was numerically higher (p = 0.080) for S-supplemented cows. Nitrogen retained as a percentage of N intake suggests that N utilization was lower for animals fed 0.15% S, whereas those supplemented with S tended to utilize their N more efficiently. This finding may be due to cows fed cassava foliage with low sulfur supplement (0.15% S) providing low sulfur for microbial growth leading to a high ratio of N: S in the rumen. Qi et al. (1992) suggested that if a diet contains an unsuitable ratio of N to S, especially high N and low S, the animals will adjust to this ratio by wasting N by increasing N excretion. Therefore, a decrease in efficiency of feed protein utilization is the principal effect of a S deficiency. Moreover, Fron et al. (1990) suggested that all three forms of supplemental S (elemental S, sodium sulfate and DL-methionine) increase the efficiency of N utilization (retention) for cattle consuming a fescue hay-based diet. Johnson et al. (1971) also mention that elemental sulfur is less available than methionine and other sulfur sources. However, when elemental S was added to a cassava diet it improved protein utilization efficiency by pigs. Presumably, the added S improved N utilization.
The excretion of allantoin in urine was greater (p<0.05) for cows fed the 0.4% S diet than for those fed 0.15% S. Allantoin excretion in urine reflected significant differences (p<0.05) in microbial N for the 0.4% S diet as compared with 0.15% S. Purine derivatives in the urine (uric acid, allantoin, xanthine, and hypoxanthine) have been related quantitatively to the post-ruminal microbial protein supply in cattle (Chen and Gomes, 1992). It is therefore obvious that 0.4% S-supplemented cassava foliage supported higher rumen microbial protein synthesis. Recently, an in vitro study by Promkot et al. (2007) found that sulfur supplementation (0.5% substrate) increased microbial biomass especially with a substrate of fresh cassava foliage. Stimulation of microbial protein synthesis by S addition has been observed in vivo with semi-purified diets containing a high proportion of urea (Elliott and Armstrong, 1982) and with natural diets in 23 reports as summarized by Durand and Komisarczuk (1988). Increased microbial protein synthesis in cows fed a 0.4% S diet in this study might be due to decreased rumen retention time, due to significantly increased DM digestibility, and an increasing trend of DM intake that may result in higher rate of passage than in cows fed with 0.15% S diet. As reported by Faichney (1993), it has often been observed that mean retention time of consumed feeds decreased with increased intake.
Milk yield and milk production
Milk production and composition did not differ significantly among treatments, except for protein content which was higher in the sulfur-supplemented group (Table 9). The higher milk protein production for the 0.4% S diet in our study may be related to improved nutrient digestibility and nitrogen utilization since there was an increased digestibility of DM, increased ADF and NDF digestibility and N retention for cows fed the 0.4% S diet, as compared with those fed 0.15% S. Similar results have been reported by Stobbs and Wheeler (1977) that milk yield and protein content of cows were increased following S supplementation.
The concentrations of SCN in milk were significantly greater (p<0.01) in cows given fresh cassava foliage diets than in those on cassava hay (p<0.05) (Table 9). This result could be due to higher HCN intake leading to higher levels of HCN metabolite (thiocyanate) in blood serum and milk. Sulfur treatments had no influence on the concentration of SCN in milk, while SCN in plasma was much higher (p<0.01) when cows fed with 0.4% S than in those fed 0.15% S. This finding might be due to passage of SCN from the blood stream into milk being apparently slow. Grun et al. (1995) reported that in lactating cows with healthy udders the SCN content of blood plasma was higher than in milk (on average twice). Jose (2004) stressed that the mammary gland barrier reduces the passage of SCN from maternal serum to milk.
CONCLUSIONS AND RECOMMENDATIONS
Based on these results, the conclusion can be made that sulfur supplementation at 0.4% (DM) in the ration was beneficial to cows consuming fresh cassava foliage or cassava hay (10% diet) and improved utilization of fresh cassava foliage or cassava hay in terms of dry matter intake, concentration of propionate in the rumen, dry matter and NDF digestibility, nitrogen retention, rumen microbial protein synthesis and high milk protein content. Supplementation of 0.4% elemental S to cassava foliage-based diets also ensured adequate detoxification of cassava cyanide in dairy cattle in this trial.
The senior author would like to express his most sincere gratitude and appreciation to the Thailand Research Fund through the Royal Golden Jubilee Ph.D. Program (Grant No.PHD/0145/2546) for research grant support, and to the Faculty of Natural Resources, Rajamangala University of Technology Isan, Skon Nakhon Campus, Tropical Feed Resources Research and Development Center (TROFREC), Khon Kaen University (KKU), Thailand for providing experimental animals and research facilities.
Akin, D. E. and W. S. Borneman. 1990. Role of rumen fungi in fiber degradation. J. Dairy Sci. 73:3023-3032.
Aminlari, M. and H. Gilanpour. 1991. Comparative studies on the distribution of rhodanese in different tissues of domestic animals. Comp. Biochem. Physiol. 99:673-677.
Aminlari, M., H. Gilanpour, H. Taghavianpour and T. Veseghi. 1989. Comparative studies on the distribution of rhodanese and beta-mercaptopyruvate sulfurtransferase in different organs of sheep (Ovis aries) and cattle (Bos taurus). Comp. Biochem. Physiol. 92:259-262.
AOAC. 1990. Official methods of analysis. 15th edn. Association of Official Analytical Chemists, Arlington, Virginia.
Barton, J. S., L. S. Bull and R. W. Hemken. 1971. Effects of various levels of sulfur upon cellulose digestion in purified diets and lignocellulose digestion in corn fodder pellets in vitro. J. Anim. Sci. 33:682-685.
Bouchard, R. and H. R. Conrad. 1973. Sulfur requirement of lactating dairy cows. II. Utilization of sulfates, molasses, and lignin-sulfonate. J. Dairy Sci. 56:1429-1434.
Bradbury, J. H., S. V. Egan and M. J. Lynch. 1991. Analysis of cyanide in cassava using acid hydrolysis of cyanogenic glucosides. J. Sci. Food Agric. 55:277-290.
Bull, L. S. 1984. Sulfur in ruminant rations. In: Proceedings of 5th Western Nutrition Conference, Calgary, Alberta, Canada. p. 33.
Chantaprasarn, N. and M. Wanapat. 2008. Effects of sunflower oil supplementation in cassava hay based-diets for lactating dairy cows. Asian-Aust. J. Anim. Sci. 21:42-50.
Chen, X. B. and M. J. Gomes. 1992. Estimation of microbial protein supply to sheep and cattle based on urinary excretion of purine derivatives-an overview of the technical details. International Feed Resources Unit, Rowett, Research Institute, Aberdeen.
Chen, X. B., D. J. Kyle and E. R. 0rskov. 1993. Measurement of allantoin in urine and plasma by high performance liquid chromatography with pre-column derivatization. J. Chromatogr. 617:241-247.
de Oliveira, L. A., C. Jean-Balin, V. D. Corso, V. Benard, A. Durix and S. Komisarczuk-Bony. 1996. Effect of a high sulfur diet on rumen microbial activity and rumen thiamine status in sheep receiving a semi-synthetic, thiamine-free diet. Reprod. Nutr. Dev. 36:31-42.
de Paiva, A. P. C. 2007. Effect of different doses of sulfur on voluntary intake of low-quality elephant grass and estimates of ruminal protozoa populations in crossbred heifers. Cienc. Agrotecnol. 31:218-222.
Durand, M. and S. Komisarczuck. 1988. Major minerals and rumen microbiota. J. Nutr. 118:249-260. Elliott, R. and D. G. Armstrong. 1982. The effect of urea and urea plus sodium sulphate on microbial protein production in the rumens of sheep given diets high in alkali-treated barley straw. J. Agric. Sci. 99:51-60.
Faichney, G. 1993. Digesta flow. Page 53 in Quantitative Aspects of Ruminant Digestion and Metabolism (Ed. J. Forbes and J. France). CAB International, Wallingford, UK.
Frankenberg, L. 1980. Enzyme therapy in cyanide poisoning: Effect of rhodanese and sulfur compounds. Arch. Toxical. 45:315-323.
Fron, M. J., J. A. Boling, L. P. Bush and K. A. Dawson. 1990. Sulfur and nitrogen metabolism in the bovine fed different forms of supplemental sulfur. J. Anim. Sci. 68:543-552.
Galyean, M. 1989. Laboratory procedure in animal nutrition research. Department of Animal and Range Sciences, New Mexico State University, USA.
Goering, H. K. and P. J. Van Soest. 1970. Forage fiber analysis, agriculture. Handbook No.379. United State Department of Agriculture, Washington, DC.
Goodrich, R. D., T. S. Kahlon, D. E. Pamp and D. P. Cooper. 1978. Sulfur in ruminant nutrition. National Feed Ingredient Association, West Des Moines, LA.
Grun, E., B. Fiirll, A. Kramer, B. Thiirkow, W. Weuffen and H. Paetzelt. 1995. Thiocyanate content in blood plasma, udder lymph and milk from healthy cows and cows with mastitis. Berl. Munch. Tierarztl Wochenschr. 108:93-97.
Gutierrez, C. L., L. D. Contreras, C. J. T.Ramirez, F. Sanchez and C. H. Gonzalez. 1996. Sulfur supplementation improves rumen activity. Feed Mix 4:18-19.
Hammond, A. C. 1983. Effect of dietary protein level, ruminal protein solubility and time after feeding on plasma urea nitrogen and the relationship of plasma urea nitrogen to other ruminal and plasma parameters. J. Anim. Sci. 57(Suppl. 1):435 (Abstr.).
Hong, N. T. T., M. Wanapat, C. Wachirapakorn, P. Pakdee and P. Rowlinson. 2003. Effects of timing of initial cutting and subsequent cutting on yields and chemical compositions of cassava hay and its supplementation on lactating dairy cows. Asian-Aust. J. Anim. Sci. 16:1763-1769.
Johnson, W. H., R. D. Goodrich and J. C. Meiske. 1971. Metabolism of radioactive sulfur from elemental sulfur, sodium sulfate and methionine by lambs. J. Anim. Sci. 32:778-783.
Jose, G. 2004. Maternal thiocyanate and thyroid status during breast-feeding. J. Am. Coll. Nutr. 23:97-101.
Khang, D. N. and H. Wiktorsson. 2004. Effects of fresh cassava tops on rumen environment parameters, thyroid gland hormones and liver enzymes of local yellow cattle fed urea-treated fresh rice straw. Trop. Anim. Health Prod. 36:751-762.
Kiyothong, K. and M. Wanapat. 2004. Growth, hay yield and chemical composition of cassava and stylo 184 grown under intercropping. Asian-Aust. J. Anim. Sci. 17:799-807.
Lambert, J. L., J. Ramasamy and J. F. Paukstelis. 1975. Stable reagents for the colorimetric determination of cyanide by modified Konig reactions. Anal. Chem. 47:916-918.
Leng, R. A. and T. R. Preston. 1983. Nutritional stratergies for the utilization and technologies to the small farmer in Asia. In: Proceeding of 5th World Conference on Animal Production, Tokyo. pp. 310-318.
Majak, W. and K. J. Cheng. 1984. Cyanogenesis in bovine rumen fluid and pure cultures of rumen bacteria. J. Anim. Sci. 59:784790.
Majak, W. and K. J. Cheng. 1987. Hydrolysis of the cyanogenic glycosides amygdalin, prunasin and linamarin by ruminal microorganisms. Can. J. Anim. Sci. 67:1133-1137.
Man, N. V. and H. Wiktorsson. 2001. Cassava tops ensiled with or without molasses as additive effects on quality, feed intake and digestibility by heifers. Asian-Aust. J. Anim. Sci. 14:624-630.
Manner, J. H. and G. Gomez. 1973. Implications of cyanide toxicity in animal feeding studies using high cassava rations. In: Proceedings of an International Workshop, Chronic cassava toxicity, Development and Research Center, Ottawa, London. pp. 113-120.
Martensson, J. and B. Sorbo. 1978. Human P-mercaptopyruvate sulfurtransferase: distribution in cellular compartments of blood and activity in erythrocytes from patients with haernathological disorders. Clin. Chem. Acta. 87:11-15.
Morrison, M., R. M. Murray and A. N. Boniface. 1990. Nutrient metabolism and rumen micro-organisms in sheep fed a poorquality tropical grass hay supplemented with sulphate. J. Agric. Sci. 115:269-275.
National Research Council. 2001. Nutrient requirements of dairy cattle. 7th Ed. National Academic Press, Washington DC.
Oke, O. L. 1978. Problems in the use of cassava as animal feed.
Anim. Feed Sci. Technol. 3:345-380.
Onwuka, C. F. I., A. O. Akinsoyinu and O. O. Tewe. 1992. Role of sulfur in cyanide detoxification in ruminants. Small Rumin. Res. 8: 277-284.
Orpin, C., G. and Y. Greenwood. 1986. Nutritional and germination requirements of the rumen chytridiomycete Neocallimastix patriciarum. Trans. Br. Mycol. Soc. 86:103109.
Promkot, C. and M. Wanapat. 2005. Effect of level of crude protein and use of cottonseed meal in diets containing cassava chips and rice straw for lactating dairy cows. Asian-Aust. J. Anim. Sci. 18:502-511.
Promkot, C., M. Wanapat and P. Rowlinson. 2007 Estimation of ruminal degradation and intestinal digestion of tropical protein resources using the nylon bag technique and the three-step in vitro procedure in dairy cattle on rice straw diets. Asian-Aust. J. Anim. Sci. 20:1849-1852.
Promkot, C., M. Wanapat, C. Wachirapakorn and C. Navanukraw. 2007. Influence of sulfur on fresh cassava foliage and cassava hay incubated in rumen fluid of beef cattle. Asian-Aust. J. Anim. Sci. 20:1424-1432.
Qi, K., C. D. Lu and F. N. Owens. 1992. Sulfate supplementation to Alpine goats: Effects on milk yield and composition, metabolites, nutrient digestibilities, and acid-base balance. J. Anim. Sci. 70:3541-3550.
Qi, K., C. D. Lu and F. N. Owens. 1993. Sulfate supplementation of growing goats: Effects on performance, acid-base balance, and nutrient digestibilities. J. Anim. Sci. 71:1579-1587.
Ravindran, V., E. T. Kornegay and A. S. B. Rajaguru. 1987. Influence of processing methods and storage time on the cyanide potential of cassava leaf meal. Anim. Feed. Sci. Thechnol. 17:227-234.
Roseler, D. K., J. D. Ferguson, C. J. Sniffen and J. Herrema. 1993. Dietary protein degradability effects on plasma and milk urea nitrogen and milk non-protein in holstein cows. J. Dairy. Sci. 76:525-534.
Samuel, M., S. Sagathewan, J. Thomas and G. Mathen. 1997. An HPLC method for estimation of volatile fatty acids of ruminal fluid. Indain J. Anim. Sci. 67:805-807.
SAS Institute. Inc. 1996. SAS/STAT User's Guide: Version 6. 12. 4th ed. Cary, North Carolina.
Slyter, L. L, W. Chalupa, R. R. Oltjen and J. M. Weaver. 1986. Sulfur influences on rumen microorganisms in vitro and in sheep and calves. J. Anim. Sci. 63:1949-1959.
Soto-Blanco, B., S. L. Gorniak and E. T. Kimura. 2001. Physiopathological effects of the administration of chronic cyanide to growing goats-a model for ingestion of cyanogenic plants. Vet. Res. Commun. 25:379-389.
Stobbs, T. H. and J. L. Wheeler. 1977. Response by lactating cows grazing sorghum to sulfur supplementation. Trop. Agric. 54:229-234.
Thompson, L. H., M. B. Wise, R. W. Harvey and E. R. Barrick. 1972. Starea, urea and sulfur in beef cattle rations. J. Anim. Sci. 35:474-480.
Wanapat, M. 1994. Supplementation of straw-based diets for ruminants in Thailand. In: Proceedings of Sustainable Animal Production and the Environment, The 7th AAAP Animal Science Congress. Bali, Indonesia. pp. 25-38.
Wanapat, M. 1999. Feeding of ruminants in the tropics based on local feed resources. Khon Kaen Publ. Comp. Ltd., Khon Kaen, Thailand.
Wanapat, M. 2003. Manipulation of cassava cultivation and utilization to improve protein to energy biomass for livestock feeding in the tropics. Asian-Aust. J. Anim. Sci. 16:463-472.
Wanapat, M. and C. Devendra. 1992. Feeding and nutrition of dairy cattle and buffaloes in Asia. Sustainable Animal Production. In: Proceedings 6th AAAP Animal Science Congress. Bangkok, Thailand. pp. 177-194.
Wanapat, M. and S. Khampa. 2006. Effect of cassava hay in high-quality feed block as anthelmintics in steers grazing on ruzi grass. Asian-Aust. J. Anim. Sci. 19:695-198.
Wanapat, M., A. Petlum and O. Pimpa. 2000a. Supplementation of cassava hay to replace concentrate use in lactating Holstein Friesian crossbreds. Asian-Aust. J. Anim. Sci. 13:600-604.
Wanapat, M., C. Promkot and S. Wanapat. 2006. Effect of cassoyurea pellet as a protein source in concentrate on ruminal fementation and digestibility in cattle. Asian-Aust. J. Anim. Sci. 19:1004-1009.
Wanapat, M., C. Promkot, S. Wanapat and P. Rowlinson. 2007. Cassava hay as a protein replacement for soybean meal in concentrate supplement for dairy cows. Indain J. Anim. Sic. 77(12):1312-1315.
Wanapat, M., O. Pimpa, A. Petlum and U. Boontao. 1997. Cassava hay: A new strategic feed for ruminants during the dry season. Livest. Res. Rural Dev. 9: http://www.cipav.org.co/LRRD/ lrrd9/2/metha92.htm
Wanapat, M., O. Pimpa, A. Petlum, C. Wachirapakorn and C. Yuangklang. 2000b. Participation scheme of smallholder dairy farmers in the NE, Thailand on improving feeding systems. Asian-Aust. J. Anim. Sci. 13:830-836.
Wanapat, M., T. Puramongkon and W. Siphuak. 2000c. Feeding of cassava hay for lactating dairy cows. Asian-Aust. J. Anim. Sci. 13:478-482.
Wanapat, M., T. Varvikko and A. Vanhatalo. 1990. The influence of selected chemical treatments on the ruminal degradation and subsequent intestinal digestion of cereal straw Asian-Aust. J. Anim. Sci. 3:75-83.
Wiktorsson, H. and D. N. Khang. 2004. Effects of ensiled cassava tops on rumen environment parameters, thyroid gland hormones and liver enzymes of cows fed urea-treated fresh rice straw. Asian-Aust. J. Anim. Sci. 17:936-941.
Wiktorsson, H. and N. V. Man. 2002. Effect of molasses on nutritional quality of cassava and gliricidia tops silage. AsianAust. J. Anim. Sci. 15:1294-1299.
Wora-anu, S., M. Wanapat, C. Wachirapakorn and N. Nontaso. 2004. Effect of different tropical feed resources on rumen ecology of beef cattle. In: Proceedings 11th AAAP Animal Science Congress, Kualar Lumpur. Vol. II. pp. 348-351.
Wora-anu, S., M. Wanapat, C. Wachirapakorn and N. Nontaso. 2007. Effect of roughage sources on cellulolytic bacteria and rumen ecology of beef cattle. Asian-Aust. J. Anim. Sci. 20: 1705-1712.
Zinn, R. A., E. Alvarez, M. Mendez, M. Montano, E. Ramirez and Y. Shen. 1997. Influence of dietary sulfur level on growth performance and digestive function in feedlot cattle. J. Anim. Sci. 75:1723-1728.
C. Promkot and M. Wanapat *
Animal Science, Faculty of Natural resources, Rajamangala University of Technology Isan, Skon Nakhon Campus, Skon Nakhon, 47160, Thailand
* Corresponding Author: Metha Wanapat. Tropical Feed Resources Research and Development Center, Department of Animal Science, Faculty of Agriculture, Khon Kaen University, PO Box 40002, Khon Kaen, Thailand. Tel: +66-043-202368, Fax: +66-043-202368, E-mail: email@example.com
Received February 28, 2009; Accepted May 6, 2009
Table 1 Summary of experimental feeds (total mixed rations, TMR) and animals Treatments Item FCF S0.15 (a) S0.4b Roughages (% DM in TMR) Rice straw (R) 30 30 Fresh cassava foliage (FCF) 10 10 Cassava hay (CH) -- -- Concentrates (% DM in TMR) 0.2% S (c) 60 -- 0.6% S (d) -- 60 Roughage:concentrate 40:60 40:60 Experimental period (days) 30 30 Number of animals 8 8 Lactation 1-2 1-2 Range of initial LW (kg) 450-550 450-550 Range of initial milk yield 12-16 12-16 Range of day-in-milk 100-150 100-150 Treatments Item CH S0.15 S0.4 Roughages (% DM in TMR) Rice straw (R) 30 30 Fresh cassava foliage (FCF) -- -- Cassava hay (CH) 10 10 Concentrates (% DM in TMR) 0.2% S (c) 60 -- 0.6% S (d) -- 60 Roughage:concentrate 40:60 40:60 Experimental period (days) 30 30 Number of animals 8 8 Lactation 1-2 1-2 Range of initial LW (kg) 450-550 450-550 Range of initial milk yield 12-16 12-16 Range of day-in-milk 100-150 100-150 (a) S0.15 = TMR containing sulfur at 0.15% DM. (b) S0.4 = TMR containing sulfur at 0.4% DM. (c) 0.2% S = the concentrate feed consisting of sulfur 0.2% DM. (d) 0.6% S = the concentrate feed consisting of sulfur 0.6% DM. Table 2. Ingredients and chemical composition of experimental concentrates, fresh cassava foliage (FCF) and cassava hay (CH) Ingredient Sulfur concentration FCF CH (% dry matter) 0.2 0.6 Cassava chip 52.2 52.0 Dried tomato pomace 7.2 7.1 Dried brewer's grain 23.0 23.0 Palm seed meal 7.6 7.6 Molasses 5.2 5.1 Urea 3.4 3.4 Sulfur 0.2 0.6 Dicalcium (a) 0.4 0.4 Salt 0.4 0.4 Mineral mix (b) 0.4 0.4 Dry matter (%) 94.5 95.1 26.8 95.8 % dry matter Organic matter (%) 95.7 94.6 92.5 92.1 Crude protein (%) 19.8 19.5 21.3 20.7 Neutral detergent fiber 25.3 25.7 48.8 50.6 Acid detergent fiber 15.0 15.2 32.5 35.3 Ash 4.4 5.3 7.5 8.2 (a) Dicalcium (each kg contains): Calcium 300 g; Phosphorus 140 g. (b) Mineral mix (Dailymin[R]) (each kg contains): Iron 2.14 g; Iodin 0.15 g; sulfur 11.82 g; Copper 0.23 g; Magnesium 0.96 g; Sodium 2.68 g; Manganese 7.21 g; Cobalt 0.03 g; Phosphorus 19.60 g; Selenium 0.003 g; Zing 0.16; Calcium 204.03 g. Table 3. Chemical composition (% of dry matter) of four total mixed rations (TMR) fed to dairy cows Cassava foliage FCF (a) CH (b) Ingredient (% S) S0.15 (c) S0.4 (d) S0.15 S0.4 DM 50.2 50.7 56.1 57.6 OM 92.8 92.1 92.8 92.1 CP 15.2 15.0 15.2 15.0 NDF 46.9 47.1 47.1 47.3 ADF 28.8 28.9 29.1 29.2 Ash 7.3 7.8 7.3 7.9 S 0.15 0.40 0.15 0.40 (a) FCF = Fresh cassava foliage. (b) CH = Cassava hay. (c) S0.15 = Sulfur in ration at 0.15% dry matter. (d) S0.4 = Sulfur in ration at 0.4% dry matter. Table 4. Effect of fresh cassava foliage (FCF), cassava hay (CH) and different concentrations of S in total mixed rations on daily intakes, HCN intake, total-tract digestibility, live weight and weight change of dairy cows Cassava foliage FCF CH Item (% S) 0.15 0.40 0.15 0.40 Daily intake kg 11.6 12.4 11.0 11.8 % BW 2.5 2.6 2.3 2.6 HCN intake (mg/hd/d) 1180.4 1256.4 99.4 107.1 Apparent total-tract digestibility DM 65.6 72.7 68.6 72.1 OM 73.3 77.0 73.5 75.3 CP 72.5 76.8 73.8 75.3 NDF 59.3 71.3 64.1 65.8 ADF 53.19 60.2 56.3 56.4 BW (kg) Initial 472.8 472.4 472.8 450.9 Final 463.5 474.4 471.8 457.2 ADG (kg/hd/d) -0.48 0.10 -0.06 0.33 Cassava foliage SEM Contrast Item (% S) Cassava S Interaction Daily intake kg 0.40 NS 0.065 NS % BW 0.10 NS 0.057 NS HCN intake (mg/hd/d) 41.2 *** NS NS Apparent total-tract digestibility DM 2.14 NS * NS OM 3.60 NS NS NS CP 3.50 NS NS NS NDF 3.15 NS 0.052 NS ADF 2.09 NS 0.114 0.131 BW (kg) Initial 18.29 NS NS NS Final 16.62 NS NS NS ADG (kg/hd/d) 0.24 NS 0.058 NS NS = Non-significant, * p<0.05, ** p<0.01. Table 5. Effect of fresh cassava foliage (FCF), cassava hay (CH) and different concentrations of S in total mixed rations on rumen ecology in dairy cows Cassava foliage FCF CH Item (S %) 0.15 0.40 0.15 0.40 Rumen ecology pH 0 h, post-feeding 7.0 7.1 7.1 7.1 4 h 6.8 6.8 6.7 6.7 Mean 7.0 7.0 6.9 6.9 N[H.sub.3]-N (mg %) 0 h, post-feeding 11.8 13.8 12.4 10.9 4 h 15.3 13.9 11.2 13.7 Mean 14.2 13.61 11.9 12.3 Total VFA (mM/ml) VFA (mol/100 mol) 106.3 109.9 104.4 107.7 Acetate (C2) 67.5 67.5 68.6 67.2 Propionate (C3) 17.2 19.5 18.0 20.2 Butyrate (C4) 14.0 13.9 13.1 13.7 C2: C3 3.9 3.5 3.9 3.4 Cassava foliage SEM Contrast Item (S %) Cassava S Interaction Rumen ecology pH 0 h, post-feeding 0.10 NS NS NS 4 h 0.08 NS NS NS Mean 0.07 NS NS NS N[H.sub.3]-N (mg %) 0 h, post-feeding 2.11 NS NS NS 4 h 1.97 NS NS NS Mean 2.24 NS NS NS Total VFA (mM/ml) NS NS NS VFA (mol/100 mol) 6.57 NS NS NS Acetate (C2) 6.82 NS NS NS Propionate (C3) 1.16 NS 0.081 NS Butyrate (C4) 0.72 NS NS NS C2: C3 0.26 NS NS NS VFA = Volatile fatty acid. NS = Non-significant. * p<0.05, ** p<0.01. Table 6. Effect of fresh cassava foliage (FCF), cassava hay (CH) and different concentrations of S in total mixed rations on rumen microorganisms in dairy cows Cassava foliage FCF CH SEM Item (S %) 0.15 0.4 0.15 0.4 Total direct counts Bacteria (x[10.sup.11] 1.4 1.7 1.6 1.7 0.09 cell/ml) Protozoa (x[10.sup.6] 0.6 0.7 0.8 0.7 0.07 cell/ml) Fungal zoospores 0.4 0.6 0.4 0.5 0.05 (x [10.sup.6] cell/ml) Cassava foliage Contrast Item (S %) Cassava Contrast Interaction Total direct counts Bacteria (x[10.sup.11] NS * 0.162 cell/ml) Protozoa (x[10.sup.6] NS NS NS cell/ml) Fungal zoospores NS ** 0.085 (x [10.sup.6] cell/ml) NS = Non-significant, * p<0.05, ** p<0.01. Table 7. Effect of fresh cassava foliage (FCF), cassava hay (CH) and different concentrations of S in total mixed rations on rumen, serum and milk thiocyanate (SCN), blood urea nitrogen (BUN), thyroid hormones and liver enzymes Cassava foliage FCF CH SEM Item (S %) 0.15 0.40 0.15 0.40 Serum SCN (ppm) 18.5 21.4 15.7 17.0 0.37 Milk SCN (ppm) 15.4 16.0 14.5 14.7 0.43 BUN (mg %) 15.5 14.8 16.3 17.5 1.21 MUN (mg %) 16.7 15.56 17.03 16.26 0.50 T3 (nmol/L) 1.8 1.7 1.7 1.6 0.21 T4 (nmol/ml) 7.3 6.9 7.3 4.9 1.14 ALT (units/L) 58 62.3 55.3 50.7 5.09 AST (units/L) 24.8 27.8 27.5 25.9 3.87 Cassava foliage Contrast Item (S %) Cassava S Interaction Serum SCN (ppm) ** ** * Milk SCN (ppm) * NS NS BUN (mg %) NS NS NS MUN (mg %) NS 0.069 NS T3 (nmol/L) NS NS NS T4 (nmol/ml) NS NS NS ALT (units/L) 0.150 NS NS AST (units/L) NS NS NS T3 = Triiodothyronine, T4 = Thyroxine, ALT = Alanine aminotransferase, AST = Aspartate aminotransferase. NS = Non-significant, * p<0.05, ** p<0.01. Table 8. Nitrogen balance (g/d), excretion of allantoin and microbial nitrogen supply in dairy cows fed cassava foliage supplemented with sulfur Cassava foliage FCF CH Item (S %) 0.15 0.40 0.15 0.40 Nitrogen balance (g/d) 280.9 286.3 280.3 279.3 Fecal N (% of intake) 30.2 26.2 28.7 28.3 Urinary N (% of intake) 39.9 36.4 39.3 33.6 Milk N (% of intake) 25.1 24.8 21.6 25.5 N Retention (% of intake) 4.7 12.6 10.4 12.6 Urinary Allantoin (g/d) 25.3 28.0 26.3 27.6 Microbial N yield (g N/d) (1) 136.0 154.6 142.8 151.3 Cassava foliage SEM Contrast Item (S %) Cassava S Interaction Nitrogen balance (g/d) 18.1 NS NS NS Fecal N (% of intake) 2.2 NS NS NS Urinary N (% of intake) 2.3 NS 0.068 NS Milk N (% of intake) 3.1 NS NS NS N Retention (% of intake) 2.6 NS 0.080 NS Urinary Allantoin (g/d) 0.8 NS * NS Microbial N yield (g N/d) (1) 5.4 NS * NS (1) Microbial N yield (g N-d) = (urinary allantoin (mmol-d)x 1.043)- (0.329xBW0.75) (Chen and Gomes, 1992), based on 82% of purine derivatives as allantoin and 18% as uric acid in this study. NS = Non-significant, * p<0.05, ** p<0.01. Table 9. Effect of fresh cassava foliage (FCF), cassava hay (CH) and different concentrations of S in total mixed rations on milk yield and composition in dairy cows Cassava foliage FCF CH SEM Item (S %) 0.15 0.40 0.15 0.40 Milk yield (kg/d) 12.2 12.8 12.1 12.0 0.54 3.5% FCM (kg) 12.2 13.0 12.7 12.5 0.56 Milk composition (%) Fat 4.0 4.1 4.5 4.2 0.33 Protein 3.4 3.5 3.2 3.5 0.08 Lactose 4.4 4.1 4.4 4.3 0.17 Solid-not-fat 8.6 8.4 8.3 8.6 0.16 Total solids 12.6 12.5 12.8 12.9 0.37 Cassava foliage Contrast Item (S %) Cassava S Interaction Milk yield (kg/d) NS NS NS 3.5% FCM (kg) NS NS NS Milk composition (%) Fat NS NS NS Protein NS * NS Lactose NS NS NS Solid-not-fat NS NS NS Total solids NS NS NS NS = Non-significant, * p<0.05, ** p<0.01.
|Gale Copyright:||Copyright 2009 Gale, Cengage Learning. All rights reserved.|