The effect of rapid growth with fattening upon lactation in cattle and rats

A number of investigations have been made concerning the plane of nutrition just prior to parturition and during lactation and its effect on milk production, but very little work has been done to determine the effect of rapid growth with fattening on milk production in subsequent lactations. Such information is particularly pertinent for determining the most economical means of raising dairy heifers. Fattening or very rapid growth of dairy cattle would be a wasteful practice unless it resulted in lactation benefits. Common observation of dairy husbandmen has been that fat heifers seldom develop into high milk producers. This failure to milk well has often been blamed on inheritance rather than environmentor rearing intensity. It was considered important to determine the relative Importance of environment (feeding intensity) and heredity (inherent milking potential) as they affect fattening during growth and lactation development. Identical twin heifers were selected for experimental animals because of their identical inheritance, Littermate white rats were also used to determine the effect of rapid growth and fattening from weaning to parturition upon lactation in a second animal species.