Further Comparisons of Alfalfa Hay and Alfalfa Silage for Growing Dairy Heifers

Abstract

Summary Three different types of trials were performed in which body weight gain, dry matter (D. M.) intake, and their ratio were compared when growing dairy heifers were fed hay or silage. Alfalfa hay and wilted silage simultaneously harvested from the same fields were fed in a continuous (14 mo.) and a reversal trial (7 mo. each) to dairy heifers from 5 to 19 mo. of age. Growth rates, D.M. intake, and efficiency of gain were lower for the heifers fed silage. After 19 mo. of age, all heifers were fed a normal ration of hay, corn silage, and grain, and the growth rate was increased for most heifers. Body weight at 2 yr. of age for heifers that had been fed hay during the 14-mo. experimental period was much greater than that of heifers that had been fed silage during this period. Body weight at 2 yr. for heifers fed silage for either of the 7-mo. periods was somewhat less than that of hay-fed heifers. These data indicate that silage may provide the major source of feed for dairy heifers for as long as 7 mo., either before or after a year of age, provided more adequate rations are supplied following these intervals without seriously reducing their size at calving time. Alfalfa harvested simultaneously from the same field as hay, wilted silage (43–46% dry matter), or as direct-cut silage during two different crop years was fed for 2 to 3 mo. to growing dairy heifers when 7 to 19 mo. of age. For each crop year there was little difference in rates of gain or dry matter intake or in efficiency of gain for heifers fed hay or wilted silage (43–46% dry matter). Heifers fed direct-cut silage had lower rates of gain, intake, and efficiency. However, in one crop year the difference between hay and direct-cut silage was small and not significant. It is suggested that the dry matter content of the forage when ensiled, and differences in the resulting fermentation, are major factors in determining the acceptability of silages by heifers and their resulting performance. Dry matter from hay produced larger gains than an equal amount of dry matter from wilted or D.C. silage when heifers were pair-fed the two forages. This suggests that there may be a difference in the nutritive value of hay and silage dry matter, as well as differences in their acceptability by dairy heifers.