添喂色氨酸、过瘤胃色氨酸对奶牛泌乳性能、血浆指标和乳中褪黑素含量的影响

Effects of Tryptophan and Rumen-Protected Tryptophan Supplementations on Lactation Performance,Plasma Indexes and Milk Melatonin Content of Dairy Cows

本研究旨在探究在饲粮中添喂色氨酸(Trp)、过瘤胃色氨酸(RPTrp)对奶牛泌乳性能、血浆指标和乳中褪黑素(MLT)含量的影响。选取30头3~5岁、2~3胎次、泌乳天数为(180±46)d的健康荷斯坦奶牛,随机分为3组,分别为对照组、试验Ⅰ组和试验Ⅱ组,每组10头。对照组饲喂全混合日粮,试验Ⅰ、Ⅱ组在对照组基础上分别添喂100 g/(d·头)色氨酸和220 g/(d·头)过瘤胃色氨酸(L-色氨酸含量≥45%)。预试期7 d,正试期60 d。结果表明:1)试验Ⅰ、Ⅱ组产奶量相比于对照组分别提高了11.78%(P<0.05)和17.19%(P<0.01);试验Ⅰ、Ⅱ组乳糖产量极显著高于对照组(P<0.01)。2)试验Ⅰ、Ⅱ组在14:00和22:00血浆中生长激素(GH)含量极显著高于对照组(P<0.01);14:00时,试验Ⅱ组血浆色氨酸含量极显著高于对照组(P<0.01),各组血浆褪黑素含量无显著差异(P>0.05);22:00时试验Ⅱ组血浆色氨酸含量极显著高于对照组(P<0.01),试验Ⅱ组血浆褪黑素含量显著高于对照组(P<0.05);试验Ⅰ组在14:00和22:00血浆色氨酸、5-羟色胺(5-HT)和褪黑素的含量与对照组均无显著差异(P>0.05)。3)05:00时试验Ⅱ组乳中褪黑素含量极显著高于对照组(P<0.01);18:00时各组乳中褪黑素含量无显著差异(P>0.05)。4)试验Ⅰ组血浆总抗氧化能力(T-AOC)极显著高于对照组(P<0.01);试验Ⅱ组血浆谷胱甘肽过氧化物酶(GSH-Px)活性极显著高于对照组(P<0.01);试验Ⅰ、Ⅱ组血浆超氧化物歧化酶(SOD)活性极显著高于对照组(P<0.01);试验Ⅱ组血浆丙二醛(MDA)含量极显著低于对照组(P<0.01)。结果提示,添喂色氨酸[100 g/(d·头)]、过瘤胃色氨酸[220 g/(d·头)]能够提高泌乳期奶牛产奶量、血浆GH含量及抗氧化能力,其中以添喂过瘤胃色氨酸效果较好;添喂过瘤胃色氨酸[220 g/(d·头)]可提高血浆色氨酸含量及夜间血浆褪黑素含量,从而提高夜间奶牛乳中褪黑素含量。

This study w as conducted to investigate the effects of tryptophan（ Trp） and rumen-protected tryptophan（ RPTrp） supplementations in diet on lactation performance,plasma indexes and milk melatonin（ MLT）content of dairy cow s. Thirty healthy Holstein dairy cow s at 3 to 5 years of age,2 to 3 parities,（ 180 ± 46） d of lactation days w ere selected and randomly divided into 3 groups,w hich w ere control group,trial groups Ⅰand Ⅱ. Cow s in control group w as fed a total mixed ration（ TMR）,and trial groups Ⅰ and Ⅱ w ere supplemented w ith 100 g/（ d·head） Trp and 220 g/（ d·head） RPTrp [L-tryptophan content w as over 45%]based on control group,respectively. The pre-trial lasted for 7 days,and the trial lasted for 60 days. The results show ed as follow s： 1） Compared w ith control group,milk yield in trial groups Ⅰ and Ⅱ w as increased by11.78%（ P〈0.05） and 17.19%（ P〈0.01）,respectively; lactose yield in trial groups Ⅰ and Ⅱ w as significantly increased（ P〈0. 01）. 2） Compared w ith control group,plasma grow th hormone（ GH） content at14： 00 and 22： 00 in trial groups Ⅰ and Ⅱ w as significantly increased（ P〈0.01）; at 14： 00,plasma Trp content in trial group Ⅱ w as significantly increased（ P〈0.01）,but there w as no significantly difference of plasma MLT content among groups（ P〈0.05）; at 22： 00,plasma Trp（ P〈0.01） and MLT contents（ P〈0.05） in trial group Ⅱ w ere significantly increased; in trial group Ⅰ,plasma Trp,5-hydroxytryptamine（ 5-HT） and MLT contents w ere not significantly changed both at 14： 00 and 22： 00（ P〈0.05）. 3） Compared w ith control group,at 05： 00,milk MLT content in trial group Ⅱ w as significantly increased（ P〈0.01）; at 18： 00,there w as no significant difference of milk MLT content among groups（ P〈0.05）. 4） Compared w ith control group,plasma total antioxidant capacity（ T-AOC） in trial group Ⅰ w as significantly increased（ P〈0. 05）; plasma glutathione peroxidase（ GSH-Px） activity in trial group Ⅱ w as significantly increased（ P〈0. 01）; plasma superoxide dismutase（ SOD） activity in trial groups Ⅰ and Ⅱ w as significantly increased（ P〈0. 01）; plasma malondialdehyde（ MDA） in trial group Ⅱ w as significantly reduced（ P〈0.01）. In conclusion,supplementation of Trp [100 g/（ d·head） ] and RPTrp [220 g/（ d· head）,] increases milk yield,plasma GH content and antioxidant capacity of Holstein dairy cow s, and RPTrp show s better effect; supplement of RPTrp[220 g/（ d·head） ]elevated plasma Trp content and plasma MLT contents at night of dairy cows,and hence increase MLT content in milk at the night.