Influence of Post-Partum Energy Level on Reproductive Performance of Hereford Cows Restricted in Energy Intake Prior to Calving

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Abstract
Sixty-nine Hereford cows receiving 4.7 lb. of TDN daily for approximately 140 days prior to calving were allotted to the following ration treatments after calving: 1, 12.5 lb. of TDN; II, 16.5 lb. of TDN; III, 25.0 lb. of TDN; IV, 8.5 lb. of TDN for 28 days, then 16.5 lb. of TDN thereafter; V, 8.5 lb. of TDN for 28 days, then 25.0 lb. of TDN thereafter. The cows weighed 1,111 lb. and scored 6.8 in body condition at the beginning of the experiment. At 24 hr. post-calving, weight had decreased to 862 lb. and body condition score to 3.7, Eighty-four days after calving, average weights were 852,895,1,133, 883, and 1,033 lb., and body condition scores averaged 4.4, 5.0, 7,3, 4.5, and 5.8 for cows in groups I through V, respectively. The interval from calving to first estrus ranged from 49 days for group II to 82 days for group V (P<.01). Groups III and V had larger follicles and greater ovarian volume (P<.01) than the other groups. Conception rate at first service was 54, 31, 83, 46, and 87%, and percent of cows diagnosed pregnant was 71, 78, 92, 69, and 100 for groups I through V, respectively.

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