Richards M W, Wettemann R P, Schoenemann H M
Oklahoma Agricultural Experiment Station, Stillwater 74078-0425.
J Anim Sci. 1989 Sep;67(9):2354-62. doi: 10.2527/jas1989.6792354x.
Twenty-two nonlactating Hereford cows exhibiting normal estrous cycles were fed either maintenance (M) or restricted (R) diets until most of the R cows became anestrus; R cows then were fed 160% of the M diet until estrous cycles resumed. Concentrations of progesterone, glucose, insulin and nonesterified fatty acids (NEFA) were determined in weekly blood samples. Blood also was collected frequently, before and after i.v. infusion of 300 ml of a 40% glucose solution, to evaluate responses in blood concentrations of glucose and insulin when cows were exhibiting normal estrous cycles, when R cows were initiating anestrus, during anestrus, and at the reinitiation of estrous cycles. Losses in BW and body condition score in R cows were associated with reduced (P less than .01) concentrations of glucose and insulin and greater (P less than .01) concentrations of NEFA in blood plasma compared with those of M cows. During normal estrous cycles, disappearance of infused glucose from plasma and concentrations of insulin in serum were similar for R and M cows. Glucose disappearance from plasma was retarded and serum concentrations of insulin remained increased for a longer time after glucose infusion in R at the start of anestrus compared with M cows (P less than .01). Similarly, during anestrus, the rate of glucose disappearance was slower for R cows (P less than .01). During refeeding of R cows, disappearance of infused glucose was similar for R and M cows. In conclusion, reduced concentrations of glucose and insulin and increased concentrations of NEFA in blood were associated with nutritional anestrus and the glucoregulatory effects of insulin were compromised during nutritional anestrus.
选取22头具有正常发情周期的非泌乳期赫里福德奶牛，分别给予维持（M）日粮或限饲（R）日粮，直至大多数R组奶牛进入乏情期；随后给R组奶牛饲喂M组日粮160%的量，直至发情周期恢复。每周采集血样，测定孕酮、葡萄糖、胰岛素和非酯化脂肪酸（NEFA）的浓度。在静脉输注300 ml 40%葡萄糖溶液前后，还频繁采集血液，以评估奶牛处于正常发情周期、R组奶牛开始进入乏情期、乏情期以及发情周期重新开始时，血糖和胰岛素血浓度的反应。与M组奶牛相比，R组奶牛体重和体况评分的下降与血浆中葡萄糖和胰岛素浓度降低（P<0.01）以及NEFA浓度升高（P<0.01）有关。在正常发情周期期间，R组和M组奶牛血浆中输注葡萄糖的消失情况以及血清中胰岛素浓度相似。与M组奶牛相比，在乏情期开始时，R组奶牛静脉输注葡萄糖后，血浆中葡萄糖的消失延迟，血清胰岛素浓度在较长时间内持续升高（P<0.01）。同样，在乏情期，R组奶牛的葡萄糖消失速率较慢（P<0.01）。在R组奶牛重新饲喂期间，R组和M组奶牛输注葡萄糖的消失情况相似。总之，血液中葡萄糖和胰岛素浓度降低以及NEFA浓度升高与营养性乏情有关，并且在营养性乏情期间胰岛素的糖调节作用受到损害。
