奶牛乳中T_4和T_3浓度变化及其与日产奶量关系的研究

Study on the Relationship of T 4 and T 3 Concentrations in Milk of Dairy Cow and Daily Yield

采用放射免疫法，测定了中国荷斯坦牛泌乳盛、中、末期乳中Ｔ４和Ｔ３浓度。结果表明：奶牛泌乳盛期乳中Ｔ４和Ｔ３浓度（１．３９１和０．４７３ｎｍｏｌ／Ｌ）均明显高于中期（０．８７６和０．２８９ｎｍｏｌ／Ｌ）和末期（０．８３７和０．２２７ｎｍｏｌ／Ｌ），中期与末期之间无显著变化。奶牛在三个泌乳时期中的日产奶量与乳中Ｔ４所占比率的灰色关联度（０．９６２、０．９６７和０．８１９）最大，表明Ｔ４浓度变化对日产奶量的影响较Ｔ３大。

T 4 and T 3 concentration in milk of Holstein cows at peak,midand late stages of lactation were tested with radioimmunoassay(RIA) in the study.The results showed that the concentrations of T 4 and T 3 in milk of dairy cow at peak of lactation(1.391 and 0.473 nmol/L)wassignificantly higher than at mid(0.876 and 0.289 nmol/L) or late stageof lactation(0.837 and 0.227 nmol/L),respectirly.Concentration ofthyroid hormone was insignificant between mid and late stages oflactation.Grey-correlation degrees of T 4 cocentration ratio and dailyyield were the highest among the three stages of lactation,and theirgrey-correlation degree were 0.962,0.967 and 0.819,respectirely.Thechange of T 4 concentration on the effect of daily yeild was higher than T 3.