Stelwagen K, Grieve D G
Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
J Dairy Sci. 1990 Sep;73(9):2333-41. doi: 10.3168/jds.S0022-0302(90)78915-1.
Forty-one Holstein and 6 Holstein crossbred heifers, 6 to 8 mo of age, were used to determine the effect of plane of nutrition on growth and mammogenesis prior to and during puberty. Animals were fed to gain 611 g (low), 737 g (medium), and 903 g (high) by a diet of cracked corn and chopped alfalfa-grass hay. Mammary biopsies were carried out in vivo to determine if they provide acceptable information on mammary composition (based upon morphometric evaluation) in comparison with dissected glands. Results indicated that NRC (1978) recommendations for average daily gain of Holstein heifers between 6 and 16 mo may be too generous. At puberty (first estrus), age and wither height decreased linearly with increasing plane of nutrition, whereas body weight and hip height were not affected by plane of nutrition. Five heifers were slaughtered at the beginning and 18 at the conclusion of the trial. Increasing plane of nutrition resulted in fatter mammary glands with decreased concentration of DNA, whereas total mammary DNA did not differ among treatment groups. In this study, morphometric evaluation of mammary tissue obtained through biopsies did not yield useful information in comparison to chemical analysis of dissected glands.
选用41头荷斯坦小母牛和6头荷斯坦杂交小母牛，年龄在6至8月龄，用于确定青春期前和青春期期间营养水平对生长和乳腺发育的影响。给动物喂食碎玉米和切碎的苜蓿干草日粮，使其日增重分别达到611克（低）、737克（中）和903克（高）。对乳腺进行活体组织检查，以确定与解剖后的腺体相比，活检是否能提供有关乳腺组成（基于形态计量学评估）的可接受信息。结果表明，美国国家研究委员会（1978年）对6至16月龄荷斯坦小母牛平均日增重的建议可能过于宽松。在青春期（首次发情）时，年龄和鬐甲高度随营养水平的提高呈线性下降，而体重和臀高不受营养水平的影响。试验开始时屠宰了5头小母牛，试验结束时屠宰了18头。营养水平的提高导致乳腺脂肪增多，DNA浓度降低，而各处理组的乳腺总DNA无差异。在本研究中，与解剖腺体的化学分析相比，通过活检获得的乳腺组织形态计量学评估未产生有用信息。
