体况对放牧普通狗尾草或内生真菌感染高羊茅的肉牛肌肉内和臀部脂肪、内分泌因素和产犊率的影响。
Effects of body condition on measures of intramuscular and rump fat, endocrine factors, and calving rate of beef cows grazing common bermudagrass or endophyte-infected tall fescue.
机构信息
USDA-ARS, Dale Bumpers Small Farms Research Center, Booneville, AR 72927, USA.
出版信息
J Anim Sci. 2010 Dec;88(12):4133-41. doi: 10.2527/jas.2010-3192. Epub 2010 Sep 3.
Multiparous beef cows were managed to achieve marginal (BCS = 4.7 ± 0.07; n = 106) or good (BCS = 6.6 ± 0.06; n = 121) body condition (BC) to determine the influence of forage environment on BW and BC changes, intramuscular fat percentage (IMF), rump fat (RF), and serum hormones during 2 yr. Cows within each BC were randomly assigned to graze either common bermudagrass (CB; n = 3 pastures/yr) or toxic endophyte-infected tall fescue (EI; n = 3 pastures/yr) during a 60-d breeding season. Blood samples were collected at d 0, 30, and 60 of the breeding season, and serum concentrations of prolactin (PRL), IGF-I, and cortisol (CORT) were quantified; PRL and progesterone (P(4)) also were quantified 10 d before the breeding season (d -10). Body weight and BCS were recorded during the breeding season (d 0, 30, and 60). Cow IMF and RF were measured via ultrasonography at the start and end of the breeding season. Cows with increased (>1 ng/mL) P(4) at the beginning of the breeding season (cyclic) had greater (P < 0.02) concentrations of PRL on d 30 and 60 compared with anestrous cows. A forage environment × BC interaction tended (P = 0.07) to influence PRL. Cows grazing CB independent of BC had increased PRL compared with cows grazing EI. Prolactin was decreased in good-BC cows grazing EI compared with cows grazing CB, and cows in marginal BC grazing EI had the least concentrations of PRL. Concentrations of IGF-I were similar (P > 0.10) among good- and marginal-BC cows grazing CB, as well as good-BC cows grazing EI; however, marginal-BC cows grazing EI had reduced (P < 0.04) concentrations of IGF-I compared with all other groups. Cows in marginal BC grazing CB gained (P = 0.02) the most BW during the breeding season, whereas good-BC cows grazing EI gained the least amount of BW. Marginal-BC cows grazing CB tended (P = 0.06) to increase BC during the breeding season, whereas good-BC cows grazing either CB or EI lost BC. Rump fat tended (P = 0.07) to increase during the breeding season in marginal-BC cows compared with cows in good BC. Calving rates were similar (P > 0.10) among good- (82%) and marginal- (84%) BC cows grazing CB, and good-BC cows grazing EI (79%); however, marginal-BC cows grazing EI had a reduced (P = 0.04) calving rate (61%). Cattle grazing EI during the breeding season lost BC. That reduction in BC may be communicated to the pituitary via hormones that include IGF-I or PRL or both, resulting in decreased calving rates.
多胎奶牛的体况（BC）被管理到边际（BCS=4.7±0.07；n=106）或良好（BCS=6.6±0.06；n=121）水平，以确定饲草环境对 BW 和 BC 变化、肌肉内脂肪百分比（IMF）、臀部脂肪（RF）和血清激素的影响，在 2 年内。每个 BC 内的奶牛在 60 天的繁殖季节内随机分配到普通百慕大草（CB；n=3 个牧场/年）或有毒内生真菌感染的高羊茅（EI；n=3 个牧场/年）中放牧。在繁殖季节的第 0、30 和 60 天采集血样，并定量检测催乳素（PRL）、胰岛素样生长因子-I（IGF-I）和皮质醇（CORT）的血清浓度；繁殖季节前 10 天（d-10）还定量检测了 PRL 和孕酮（P4）。繁殖季节（d0、30 和 60）期间记录牛的体重和 BCS。繁殖季节开始和结束时通过超声测量牛的 IMF 和 RF。在繁殖季节开始时（循环）P4 增加（>1ng/mL）的奶牛与不发情的奶牛相比，在第 30 和 60 天的 PRL 浓度更高（P <0.02）。饲草环境×BC 相互作用（P=0.07）可能会影响 PRL。无论 BC 如何，在 CB 放牧的奶牛的 PRL 都高于在 EI 放牧的奶牛。与在 CB 放牧的良好 BC 奶牛相比，在 EI 放牧的良好 BC 奶牛的 PRL 降低，而在 EI 放牧的边际 BC 奶牛的 PRL 最低。在 CB 放牧的良好和边际 BC 奶牛以及 EI 放牧的良好 BC 奶牛中，IGF-I 的浓度相似（P >0.10）；然而，与其他所有组相比，在 EI 放牧的边际 BC 奶牛的 IGF-I 浓度降低（P <0.04）。在 CB 放牧的边际 BC 奶牛在繁殖季节体重增加（P=0.02）最多，而 EI 放牧的良好 BC 奶牛体重增加最少。在 CB 放牧的边际 BC 奶牛在繁殖季节的 BCS 呈增加趋势（P=0.06），而 EI 放牧的良好 BC 奶牛的 BCS 则减少。与良好 BC 奶牛相比，在 CB 放牧的边际 BC 奶牛的臀部脂肪（RF）在繁殖季节呈增加趋势（P=0.07）。繁殖季节在 CB 放牧的良好（82%）和边际（84%）BC 奶牛以及 EI 放牧的良好 BC 奶牛（79%）之间的产犊率相似（P >0.10）；然而，在 EI 放牧的边际 BC 奶牛的产犊率降低（P=0.04）（61%）。在繁殖季节在 EI 放牧的牛失去了 BC。BC 的这种减少可能通过包括 IGF-I 或 PRL 或两者在内的激素传递给垂体，导致产犊率降低。
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