不同饲粮对泌乳奶牛乳脂前体物的摄取和利用的影响

本试验旨在研究不同饲粮条件下泌乳奶牛对乳脂前体物的摄取和利用规律。选取体重为(617±21)kg、泌乳天数为(120±20)d的9头健康泌乳荷斯坦奶牛为试验动物,采用3重复3×3拉丁方设计,随机分为3组,其中2组饲粮的精饲料配方不同,粗饲料相同均为秸秆,精粗比均为6∶4(分别称之为CSA和CSB组),余下1组以羊草、苜蓿干草、全株玉米青贮为混合粗饲料,精粗比为4∶6(MF组),每组3头;试验期84 d,分为3期,每期28 d,包括21 d的预试期及7 d的正试期。结果表明:1)各组产奶量及乳成分差异不显著(P0.05),但MF组的泌乳效率显著高于CSA和CSB组(P0.05)。2)各组饲粮C16∶0和C18∶0摄取量差异不显著(P0.05);MF组饲粮C18∶1 c9摄取量显著低于CSA和CSB组(P0.05)。3)MF组动脉血浆中长链脂肪酸和总脂肪酸含量均高于CSA和CSB组,特别是C18∶3 n3含量显著高于CSA和CSB组(P0.05)。4)MF和CSB组乳腺C18∶3 n3摄取量(日平均值)显著高于CSA组(P0.05);各组乳腺对其他长链脂肪酸的摄取量差异不显著(P0.05)。5)最终体现在乳中,表现为MF组的C18∶3 n3产量较CSA和CSB组有升高的趋势(0.05≤P0.10),而原本乳腺摄取量无显著差异的C18∶2 n6(P0.05),在乳中产量显著低于CSA和CSB组(P0.05)。由此可见,相同粗饲料、不同精饲料饲粮对泌乳奶牛生产性能无显著影响,而优质的粗饲料即使在精饲料比例降低的前提下,对乳中脂肪酸的组成及产量仍可以产生影响,使其更倾向于有利人体健康。

Effects of Different Diets on Uptake and Utilization of Milk Fat Precursor of Lactating Dairy Cows

The objective of this study was to determine uptake and utilization of milk fat precursor of lactating dairy cows under different diets conditions. Nine healthy Holstein cows with body weight of ( 617 ± 21 ) kg, lactation days of (120±20) d were selected as experimental animals. Cows were divided into 3 groups with 3 cows per group using a 3 repeated 3 × 3 Latin square design. Two groups was designed with different concen-trates, but the same roughage of corn straw, and the concentrate to roughage ratio was 6:4 ( named CSA and CSB groups, respectively); the rest group used Chinese wildrye, alfalfa hay and corn silage as mixing rough-age ( MF group) , and the concentrate to roughage ratio was 4:6. The experiment lasted for 84 d consisting of 3 periods with 28 d per period, and each period consisted of 21 d for pretest and 7 d for test. The results showed as follows: 1 ) no significant differences in milk yield and milk composition were observed among groups ( P>0.05) , MF group had significantly higher dairy efficiency compared with CSA and CSB groups ( P<0.05) . 2) Dietary C16:0 and C18:0 intakes were not significantly different among groups ( P>0.05);di-etary C18:1 c9 intake in MF group was significantly lower than that in CSA and CSB groups (P<0.05). 3) The intake of long chain fatty acids and total fatty acids contents in arterial and venous plasma in MF group were higher than those in CSA and CSB groups, especially C18:3 n3 content was significantly higher than that in CSA and CSB group (P<0.05). 4) C18:3 n3 intake of mammary gland (daily mean) in MF and CSB groups were significantly higher than that in CSA group;intakes of the other long chain fatty acids of mammary gland were not significantly different among groups (P>0.05). 5) Ultimately reflected in milk, C18:3 n3 yield in MF group tended to be higher than that in CSA and CSB groups (0.05≤P<0.10), and C18:2 n6 yield in MF group was significantly lower than that in CSA and CSB group ( P<0.05) , mammary gland intake of which was formerly had no significant difference (P>0.05). In conclusion, diet with different roughages and the same concentrate has no significant effects on performance of lactating dairy cows, while even under the condition of decreased concentrate proportion, high quality roughages can affect milk fatty acid composition and yield, and adjusts it to be better for human health.