Mammary Growth Pattern in Goats during Pregnancy and Lactation

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Abstract
Nine groups of 5 dairy goats from 4 breeds, with each breed represented at least once in each group, were in an experiment to measure mammary gland growth. Groups were virgins, days 90-100 pregnancy, 5 days prepartum (145 days pregnancy), 1 or 2 days prepartum, and 1 or 2, 5, 10, 15 and 30 days in lactation. Virgins were 19 mo. old while all others had 1 pregnancy and lactation prior to experiment. Indices of mammary growth included untrimmed and trimmed wet weights of udders dried fat-free tissue weights, DNA and RNA contents. Each index was in a regression equation best to describe the pattern of mammary growth. These included linear, quadratic, cubic and exponential model Y = AebX in which Y was the index of mammary growth and X was the day of pregnancy. Total DNA was the best index of mammary growth with a correlation of .95 in the exponential model. The predictive equation for total DNA in milligram was Y = 167e.019X on a daily basis, and the rate of growth on a monthly basis was .57. Mammary growth in goats continued into early lactation, peaking at day 5. RNA doubled on the day after parturition, which reflected the rapid increase in protein synthesis at this time.