Document Detail

Metabolizable protein supply while grazing dormant winter forage during heifer development alters pregnancy and subsequent in-herd retention rate.
MedLine Citation:
PMID:  23296826     Owner:  NLM     Status:  Publisher    
Two studies were conducted to evaluate the effects of post-weaning management of British crossbred heifers on growth and reproduction. In Exp. 1, 239 spring-born, crossbred heifers were stratified by weaning BW (234 ± 1 kg) and allotted randomly to 1 of 2 treatments. Treatments were fed at a rate equivalent to 1.14 kg/d while grazing dormant forage (6.5% CP and 80% NDF; DM basis) and were: (1) 36% CP containing 36% RUP (36RUP), or (2) 36% CP containing 50% RUP (50RUP). Supplementation was initiated in February (1995 and 1996) or November (1997 and 1998) and terminated at the onset of breeding season (mid-May). Heifers were weighed monthly up to breeding and again at time of palpation. After timed AI, heifers were exposed to breeding bulls for 42 ± 8 d. In Exp. 2, 191 spring-born, crossbred heifers were stratified by weaning BW to treatments. Heifer development treatments were: (1) pasture developed and fed 0.9 kg/d of a 36% CP supplement containing 36% RUP (36RUP); (2) pasture developed and fed 0.9 kg/d of a 36% CP supplement containing 50% RUP (50RUP); (3) corn silage based growing diet in a drylot (DRYLOT). Heifers receiving 36RUP and 50RUP treatments were developed on dormant forage. Treatments started in February and ended at the onset of a 45-d breeding season in May. Heifer BW and hip height were taken monthly from initiation of supplementation until breeding and at pregnancy diagnosis. In Exp. 1, BW was not different (P ≥ 0.27) for among treatments at all measurement times. However, 50RUP heifers had greater (P = 0.02; 80 and 67%) pregnancy rates than 36RUP heifers. In Exp. 2, DRYLOT heifers had greater (P < 0.01) BW at breeding than 36RUP or 50RUP developed heifers. However, BW at pregnancy diagnosis was not different (P = 0.24) for between treatments. Pregnancy rates tended to be greater (P = 0.10) for 50RUP heifers than 36RUP and DRYLOT. Net return per heifer was $99.71 and $87.18 greater for 50RUP and 36RUP heifers, respectively compared to DRYLOT heifers due to differences in pregnancy and development costs. Retention rate after breeding yr 3 and 4 was greatest (P ≤ 0.01) for 50RUP heifers. Thus, increasing the supply of metabolizable protein by increasing the proportion of RUP in supplements fed to heifers on dormant forage before breeding increased pregnancy rates, cow herd retention and net return compared to heifers fed in drylot.
J T Mulliniks; D E Hawkins; K K Kane; S H Cox; L A Torell; E J Scholljegerdes; M K Petersen
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-7
Journal Detail:
Title:  Journal of animal science     Volume:  -     ISSN:  1525-3163     ISO Abbreviation:  J. Anim. Sci.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8003002     Medline TA:  J Anim Sci     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Department of Animal and Range Sciences.
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