Richards M W, Wettemann R P, Spicer L J, Morgan G L
Department of Animal Science, Oklahoma State University, Stillwater 74078.
Biol Reprod. 1991 Jun;44(6):961-6. doi: 10.1095/biolreprod44.6.961.
The objectives of this experiment were to determine if a postcastration increase in concentrations of LH occurs in nutritionally anestrous beef cows and to examine the relationship between body energy reserves and secretion of LH and insulin-like growth factor-I (IGF-I). Nonpregnant, nonlactating, Hereford cows were fed to maintain (M) body weight (BW), body condition score (BCS), and normal estrous cycles (n = 5) or were fed a restricted (R) diet for 26 wk to lose BW and BCS and to become anestrus (n = 10). At 5-7 wk after the initiation of anestrus, R cows were randomly allotted to be ovariectomized (OVX) via flank incision (n = 5) or to remain intact (INT, n = 5). OVX was performed when R cows became anestrous. All M cows were OVX. Serum was collected frequently the day before and during the first 10 days after OVX, and concentrations of progesterone, estradiol, LH and IGF-I were quantified. On Day 10 after OVX, 1 mg of estradiol was injected into 3 cows from each group and serum was collected for 30 h. After OVX, there was a treatment-by-day effect for mean serum LH and IGF-I concentrations. Concentrations of LH increased (p less than 0.01) and concentrations of IGF-I decreased (p less than 0.05) in M-OVX cows when compared with R-OVX and R-INT cows. Concentrations of LH and IGF-I were similar for R-OVX and R-INT cows. The number of LH pulses was similar for M and R cows.(ABSTRACT TRUNCATED AT 250 WORDS)
本实验的目的是确定营养性乏情肉牛去势后促黄体生成素（LH）浓度是否升高，并研究机体能量储备与LH和胰岛素样生长因子-I（IGF-I）分泌之间的关系。非妊娠、非泌乳的赫里福德母牛，一组按维持体重（BW）、体况评分（BCS）和正常发情周期进行饲养（M组，n = 5），另一组限制饲养（R组，n = 10）26周，使其体重和BCS下降并进入乏情期。在乏情期开始5 - 7周后，R组母牛随机分配，通过侧腹切口进行卵巢切除（OVX，n = 5）或保持完整（INT，n = 5）。当R组母牛进入乏情期时进行卵巢切除。所有M组母牛都进行了卵巢切除。在卵巢切除前一天及术后前10天频繁采集血清，测定孕酮、雌二醇、LH和IGF-I的浓度。卵巢切除后第10天，给每组3头母牛注射1 mg雌二醇，并采集血清30小时。卵巢切除后，平均血清LH和IGF-I浓度存在处理与时间的交互作用。与R-OVX和R-INT组母牛相比，M-OVX组母牛的LH浓度升高（p < 0.01），IGF-I浓度降低（p < 0.05）。R-OVX组和R-INT组母牛的LH和IGF-I浓度相似。M组和R组母牛的LH脉冲次数相似。（摘要截断于250字）
