Milk-secretion studies with Corriedale ewes. 1. On the milk yield of ewes with special reference to its relation to the growth of suckling lambs.

This work was undertaken to study the milk yield of Corriedale ewes and the liveweight of lambs produced from those ewes with special reference to the relation of the milk yield to the growth from birth to weaning of suckling lambs. The animals used were 7 Corriedale ewes of 3 years of age and 9 Iambs (singles 5, twins 4) born from those ewes in the spring, 1957 at the Chugoku Stock Breeding Farm of the Department of Agriculture and Forestry. The milk yield of ewes was estimated from the difference of the liveweight of lambs weighed before and after suckling and the records of the milk yeild of ewes and of the liveweight of lambs were taken at 10 days intervals after birth. The results obtained were as follows : (1) It was found that the milk yield of ewes was highest during the period from 10 to 20 days after lambing and then gradually declined. (2) It seems that the ewes of higher milk yield during the first one month after lambing are greater on the average daily milk production during each 10 days period after lambing and on the total milk production during three months, as compared with those of lower milk yield. (3) Significant correlations were not found between the total milk yield of ewes during three months after lambing and their liveweight on the lambing day and between the former and the liveweight of lambs on the day of lambing. (4) Average total milk yield during three months from birth to weaning was 83.3 kg and the average daily weight gain per single lamb 240 g. (5) There were a few significant correlations between the milk yield of ewes during each one month period and during three months period and the liveweight gains of lambs after birth and was generally a increasing tendency of the correlation coefficient values, as lambs grew older. It seems that those tendencies need further investigation. (6) However, a significent correlation (r=+0.91) was found between the total milk yield of ewes and the average daily weight gain of lambs during three months period from lambing to weaning. (7) It was found that the correlations between the average daily liveweight gain of lambs during three months period and the liveweight of ewes on the lambing day and between the former and the birth weight of lambs were not significant.