The effect of level and frequency of concentrate feeding on the performance of dairy cows of different yield potential

Abstract

An experiment has been made using adult lactating cows in a randomized block design to study the effectiveness of basing feeding during the first 20 weeks of lactation on yield predicted from that obtained during the 8–12th days of lactation. Cows were classified as high yielding (HY) or low yielding (LY). The levels of feeding were identical within each yield group during the first 8 weeks of lactation but during the 9th to the 20th week two different levels of concentrate feed (HP and LP) were used. Over the 20-week period concentrates were offered in two or five daily feeds. Thus the effect of two levels and two frequencies of feeding on feed intake, milk yield and composition, and on live-weight change were studied.Cows in the HY group achieved a mean daily peak yield 2·6 kg higher than predicted while those in the LY group achieved the predicted mean peak daily yield. There was no significant effect of level of feeding on the 20-week milk yield but there was a significant effect on the yield of the LYLP class in weeks 9–20. Frequency of feeding had no significant effect on yield in either high-low-yielding cows. There was no significant effect of level of feeding on milk composition but low-yielding cows gave milk with a higher fat percentage than high-yielding cows. Five-times-a-day feeding also produced milk with a higher fat percentage than twice-a-day feeding.Live-weight changes were small and the largest variation was recorded in highyielding cows.The number of days from calving to first service was not significantly different for the two yield groups but there was a significant effect of level of feeding.