THE PERFORMANCE OF LACTATING COWS FED UREA-TREATED CORN SILAGE IN COMBINATION WITH SOYBEAN OR FISHMEAL CONTAINING CONCENTRATES

Abstract

A total of 41 multiparous Holstein cows were randomly allocated, prepartum, to one of five diets. Diets were (1) a negative control consisting of 15.5% soybean meal (SBM) concentrate plus control corn silage (CS) (12.6% crude protein, (CP)); (2) 33.5% SMB concentrate plus CS (15.6% CP); (3) 15.5% SMB concentrate plus urea-treated corn silage (UCS) (15.1% CP); (4) 12% fishmeal (FM) concentrate plus UCS (15.4% CP); and (5) 26% FM concentrate plus CS (16.2% CP). Concentrates and CS or UCS were mixed (40:60, dry matter) daily and fed ad lib for a 305-day lactation period. An increase in dietary CP from 12.6% in the negative control to 15.4% by the inclusion of FM and UCS significantly (P < 0.05) increased 305-day milk production while a similar increase in CP by inclusion of SBM and UCS did not. Milk fat content (%) was higher (P < 0.05) for cows fed diets 2 and 3 than for those fed diets 1 and 5. Fat production (g/day) during weeks 13–16 of lactation was greater for cows receiving diets 2, 3 and 4 than for those on diets 1 and 5. Body weight gain during the lactation was significantly (P < 0.05) greater for animals on diet 5 than those on the other four diets. Compared to the negative control, rumen ammonia concentration was significantly (P < 0.05) elevated when soybean meal was fed alone or in combination with UCS but not when when FM was similarly fed. The results suggest that NPN was effectively utilized when used to increase total dietary CP from approximately 12 to 15%. Key words: Fishmeal, soybean meal, urea-treated silage, dairy cattle