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Leptin and insulin-like growth factor-I as metabolic indicators of reproductive performance in Brahman and Brahman-influenced cattle
xiii, 112 leaves : illustrations ; 28 cm.
Forty-one purebred Brahman cows were blocked to control (C; n = 20) or lasalocid (L; n = 21) treatments. Cow ADG was increased (P < 0.01) in L cows prepartum and tended (P < 0.11) to be increased from calving to d 56 after calving in L cows. Postpartum interval (PPI) was unaffected by treatment; however, a greater percentage (P < .05) of L cows conceived by 90 d after calving (43% L vs 15% C). First service conception rate tended (P < .08) to be greater in L than C (68% L vs 40% C), and pregnancy rate was numerically greater (P < .12) in L (86% L vs 65% C). There was a negative correlation between leptin and PPI (r = -0.27; P < 0.0001) and a positive correlation between leptin and body condition score (BCS; r = 0.29; P < 0.06). Feeding an ionophore prior to calving and throughout the postpartum period increased the number of cows that rebreed to calve at a yearly interval. Cows with higher concentrations of leptin postpartum exhibited shorter PPI. Twenty crossbred heifers were blocked to C (n = 11) and L (n = 9) treatments. There was a significant treatment effect on age at puberty (P < 0.03), with L heifers being older at puberty. There was a significant treatment by time (P < 0.0001) interaction influencing serum concentrations of IGF-I. There was a positive correlation (r = 0.59; P < 0.006) between IGF-I and age at puberty. Ingestion of lasalocid did not alter concentrations of IGF-I and increased age at puberty. Fifty-seven crossbred heifers were utilized to determine the effects of the fibrolytic enzyme preparation Cattle-Ase ̃on heifer performance. Cattle-Ase[TM] did not improve ADG when fed with molasses-lick tanks to heifers grazing coastal bermudagrass pasture, but did increase ADG (P < 0.04) when fed with a grain carrier to heifers consuming coastal bermudagrass hay. Cattle-Ase[TM] increased (P < 0.04) the percentage of heifers estrous cycling prior to the start of the breeding season. Ingestion of Cattle-Ase[TM] when provided in a suitable carrier and with suitable forage improves heifer performance.
"Major Subject: Physiology of Reproduction".
Issued also on microfiche from University Microfilm Inc.
Includes bibliographical references (leaves 98-111).