Flores R, Looper M L, Rorie R W, Hallford D M, Rosenkrans C F
Department of Animal Science, University of Arkansas, Fayetteville 72701, USA.
J Anim Sci. 2008 Jun;86(6):1335-44. doi: 10.2527/jas.2007-0574. Epub 2008 Feb 13.
Multiparous beef (1/4 to 3/8 Bos indicus; n = 99) cows were managed to achieve low (BCS = 4.3 +/- 0.1; n = 50) or moderate (BCS = 6.1 +/- 0.1; n = 49) body condition (BC) to determine the influence of bovine (b) ST on the number of follicles, diameter of largest follicle, and serum concentrations of IGF-I, triiodothy-ronine (T3), thyroxine (T4), and prolactin. Beginning 32 d postpartum, cows within each BC were assigned randomly to treatment with or without bST. Non-bST-treated cows received no treatment, and treated cows were administered bST (Posilac, 500 mg, s.c.) on d 32, 46, and 60 postpartum. On d 60, all cows received a controlled internal drug-releasing (CIDR) device for 7 d and PGF(2alpha) at CIDR removal (CIDR-PGF(2alpha)). Blood samples (7 mL) were collected at each bST treatment and d 39 and 67 postpartum. Ultrasound was performed 1 d after CIDR-PGF(2alpha) to determine the number of small (2 to 9 mm) and large (>/=10 mm) follicles and the diameter of largest follicle. Cows treated with bST in low BC had increased (P < 0.05) IGF-I vs. low-BC non-bST-treated cows on d 39, 46, 60, and 67 postpartum. Prolactin and T3 were greater (P < 0.05) in moderate-BC than in low-BC cows on all sample dates. Thyroxine was greater (P < 0.001) in moderate-BC cows on d 46, 60, and 67 compared with low-BC cows. On d 67, bST-treated cows had greater (P < 0.05) T4 compared with non-bST-treated cows. Diameter of the largest follicle 1 d after CIDR-PGF(2alpha) was greater (P < 0.01) in anestrous cows treated with bST than for non-bST-treated anestrous cows. Diameter of the largest follicle was correlated with concentrations of IGF-I (r >/= 0.18; P </= 0.08), T3 (r >/= 0.17; P </= 0.10), and prolactin (r >/= 0.20; P </= 0.06). Treatment with bST increased IGF-I in low-BC cows, and IGF-I was correlated with the diameter of the largest follicle 1 d after CIDR-PGF(2alpha). Undernutrition of cattle may be communicated to the hypothalamic-pituitary-ovarian axis via metabolic hormones including IGF-I, thyroid hormones, or prolactin.
多胎肉牛（印度瘤牛占1/4至3/8；n = 99）被饲养以达到低（体况评分[BCS]=4.3±0.1；n = 50）或中等（BCS = 6.1±0.1；n = 49）体况，以确定牛生长激素（bST）对卵泡数量、最大卵泡直径以及胰岛素样生长因子-I（IGF-I）、三碘甲状腺原氨酸（T3）、甲状腺素（T4）和催乳素血清浓度的影响。产后32天开始，将每个体况组内的母牛随机分配接受bST处理或不接受bST处理。未接受bST处理的母牛不进行处理，接受处理的母牛在产后第32、46和60天皮下注射bST（重组牛生长激素，500 mg）。在第60天，所有母牛放置一个缓释阴道孕酮装置（CIDR）7天，并在取出CIDR时注射前列腺素F2α（CIDR-PGF2α）。在每次bST处理时以及产后第39天和67天采集血样（7 mL）。在CIDR-PGF2α处理后1天进行超声检查，以确定小卵泡（2至9 mm）和大卵泡（≥10 mm）的数量以及最大卵泡的直径。与产后第39、46、60和67天未接受bST处理的低体况母牛相比，低体况下接受bST处理的母牛IGF-I水平升高（P < 0.05）。在所有采样日期，中等体况母牛的催乳素和T3水平均高于低体况母牛（P < 0.05）。与低体况母牛相比，中等体况母牛在第46、60和67天的甲状腺素水平更高（P < 0.001）。在第67天，接受bST处理的母牛T4水平高于未接受bST处理的母牛（P < 0.05）。CIDR-PGF2α处理后1天，接受bST处理的乏情母牛的最大卵泡直径大于未接受bST处理的乏情母牛（P < 0.01）。最大卵泡直径与IGF-I浓度（r≥0.18；P≤0.08）、T3浓度（r≥0.17；P≤0.10）和催乳素浓度（r≥0.20；P≤0.06）相关。bST处理可提高低体况母牛的IGF-I水平，且IGF-I与CIDR-PGF2α处理后1天的最大卵泡直径相关。牛的营养不足可能通过包括IGF-I、甲状腺激素或催乳素在内的代谢激素传递至下丘脑-垂体-卵巢轴。
