饲粮钙磷水平对伊犁马初乳成分、乳脂脂肪酸组成、产后血液钙磷及激素的影响

旨在研究妊娠后期饲喂不同钙磷水平饲粮对产后伊犁马初乳成分、乳脂脂肪酸组成、血液钙磷及钙磷代谢激素、繁殖及生长代谢激素等生理生化指标的影响，为明确伊犁马在妊娠后期对钙磷的适宜需要量提供参考。本试验选取健康、无亲缘关系、12~13周岁、体重为（380±32）kg、胎次为4~5胎、处于第10妊娠月左右的伊犁马25匹，随机分为5组，每组5个重复。各组饲粮钙饲喂水平分别为36.00、39.00、42.00、45.00和48.00 g·d^-1，磷饲喂水平分别为26.30、28.30、30.30、32.30和34.30 g·d^-1。试验预试期10 d，正试期从第11天至母马分娩后第2天结束。母马分娩后12 h内采集初乳用于测定乳成分和乳脂脂肪酸含量，空腹血液用于测定Ca、P、甲状旁腺素（PTH）、降钙素（CT）、骨钙素（OC）、胎盘催乳素（PL）、垂体催乳素（PRL）、雌酮（E₁）、雌二醇（E₂）、血清孕酮（PROG）、甲状腺素（T₄）、三碘甲状腺原氨酸（T₃）、生长激素（GH）、胰岛素样生长因子-Ⅰ（IGF-1）等激素浓度。结果表明：1）饲粮钙磷水平对初乳中钙、磷、乳脂率、乳糖率均无显著影响，组间乳蛋白率、总固形物、体细胞数、乳脂中饱和脂肪酸（SFA）和不饱和脂肪酸（UFA）比例存在显著差异（P<0.05）。随着饲粮钙、磷水平的增加，乳磷浓度、乳蛋白率和UFA比例呈显著线性增加（P<0.05），总固形物呈显著二次增加（P<0.05），而乳糖率、SFA及肉豆蔻酸比例呈显著线性降低（P<0.05）。2）饲粮钙磷水平显著影响血液中OC和PROG浓度（P<0.05），随着饲粮钙磷水平的增加，血液中离子钙、CT和OC浓度呈显著的线性降低（P<0.05），而PTH和PROG水平呈显著的线性升高（P<0.05）。饲粮钙、磷水平对PL、PRL、E₁、E₂等生殖激素以及T₃、T₄、GH和IGF-1等生长代谢激素浓度均无显著影响。由此可见，在本试验条件下，饲粮钙磷通过提高初乳中乳蛋白率和总固形物来改变乳脂中饱和脂肪酸含量和不饱和脂肪酸比例影响初乳成分；通过降低血液中OC浓度影响钙磷代谢；通过提高血液中PROG浓度影响繁殖状况。

Effects of Dietary Calcium and Phosphorus Levels on Colostrum Components,Milk Fatty Acids Composition,and Postpartum Plasma Calcium,Phosphorus and Hormones of Yili Mares

The purpose of this experiment was to study the effects of diets with different calcium (Ca) and phosphorus (P) levels on colostrum composition, fatty acid composition of colostrum fat, the plasma physiological and biochemical indexes including plasma Ca and P and hormones related with Ca and P metabolism, growth and reproduction in Yili mares after delivery, and to provide reference for defining the appropriate Ca and P requirement of Yili mares during the late gestation period. Twenty-five healthy Yili mares without kinship, and with the age of 12-13 years old, body weight of (380±32) kg, parity of 4-5 births and about in the 10 th gestational month were selected and randomly divided into 5 groups with 5 replicates in each group. Ca feeding levels of the 5 groups were 36.00, 39.00, 42.00, 45.00 and 48.00 g·d^-1, respectively and P feeding levels were 26.30, 28.30, 30.30, 32.30 and 34.30 g·d^-1, respectively. The pre-test period was 10 days, and the experimental period lasted from the 11th day of the trial to the 2nd day after delivery. Samples of colostrum and fasting blood were collected within 12 hours after delivery to determine the milk composition, fatty acids content in milk fat, and plasma concentration of Ca, P, parathyroid hormone (PTH), calcitonin (CT), osteocalcin (OC), placental prolactin (PL), pituitary prolactin (PRL), estrone (E₁), estradiol (E₂), progesterone (PROG), thyroxine (T₄), triiodothyronine (T₃), growth hormone (GH), and insulin-like growth factor-Ⅰ (IGF-1). The results showed that:1) Dietary Ca and P levels had no significant effect on the Ca, P, milk fat percentage and lactose percentage in colostrum, but there were significant differences in milk protein percentage, total solids, somatic cell counts, total saturated fatty acids (SFA) and unsaturated fatty acids (UFA) percentages in milk fat among groups (P<0.05). With the increase of dietary Ca and P levels, the concentration of P, milk protein percentage and UFA percentage in colostrum significantly increased linearly (P<0.05), total solids significantly increased quadraticly (P<0.05), and lactose, SFA and myristic acid percentage significantly decreased linearly (P<0.05). 2) Plasma concentrations of OC and PROG were significantly affected by dietary Ca and P levels (P<0.05). With the increase of dietary Ca and P levels, the concentration of plasma ionic Ca, CT and OC significantly decreased linearly (P<0.05), while the concentration of PTH and PROG significantly increased linearly (P<0.05). Dietary Ca and P levels had no significant effect on the concentration of reproduction hormones such as PL, PRL, E₁, E₂, and growth and metabolism hormones such as T₃, T₄, GH and IGF-1. In this experiment, it can be concluded that dietary Ca and P levels affect colostrum compositions by increasing the milk protein percentage and total solids content, changing the saturated fatty acid and unsaturated fatty acid content in milk fat, affect Ca and P metabolism by reducing OC concentration, and affect fertility status by increasing PROG concentration.