Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/29/2000
Publication Date: 4/1/2001
Citation: Freetly, H.C., Ferrell, C.L., Jenkins, T.G. 2001. Production performance of beef cows raised on three different nutritionally controlled heifer development programs. Journal of Animal Science. 79:819-826. Interpretive Summary: A fraction of the heifer calves born must be retained for use as replacements in order to sustain the cow herd. The proportion retained is dependent on culling strategies, but typically 15 to 20% of the bred females are replaced annually, which requires 35 to 55% of the weaned females to be retained as replacements. Since the single largest production cost in raising heifers is feed, reducing feed associated with heifer development may offer a potential management strategy to reduce heifer development cost. The findings from this study imply that as long as replacement heifers grow to meet a minimal body weight before mating, patterns of growth may be altered in the postweaning period without a reduction in the ability of the heifer to conceive or a reduction in her calf's growth potential. However, limit feeding heifers may reduce first- calf survival. These alterations in postweaning gain through monitoring the amount of feed offered can be used to optimize feed resources.
Technical Abstract: The objective of this study was to determine primiparous cow performance following three different heifer development strategies that were the result of timed nutrient limitation. Two-hundred and eighty-two spring born MARC III heifers were weaned at 203 +/- 21 d of age and 205 +/- 21 kg BW. Treatments consisted of different amounts of the same ration being offered for a 205-d period. Heifers in the High treatment were offered 26 kcal ME/kg**0.75 daily. Heifers in the Medium treatment were offered 238 kcal ME/kg**0.75 daily. Heifers in the Low-High treatment were was offered 157 kcal ME/kg**0.75 daily the first 83 d and 277 kcal ME/kg**0.75 daily for the remainder of the 205 d. Treatments differed in total ME intake (P < 0.001) with the High treatment consuming 3,072 +/- 118 Mcal/hd, the Medium treatment consuming 2,853 +/- 42 Mcal/hd, and the Low-High treatment consuming 2,653 +/- 39 Mcal/hd. The percentage of cows that calved expressed as a fraction of the cows exposed, did not differ among treatments. The age of cow at parturition did not differ among treatments. Birth weight of cows's calves and the calves's weaning weight did not differ among the treatments. Calf survival rate on the Low-High treatment was lower than that on the Moderate treatment but did not differ from that of the High treatment. These findings imply that as long as heifers are growing and meet a minimal BW before mating, patterns of growth may be altered in the postweaning period without a reduction in the ability of the heifer to conceive or a reduction in calf growth potential. However, limit feeding heifers may reduce first-calf survival. These alterations in postweaning gain through monitoring the amount of feed offered can be used to optimize feed resources.