EFFECTS OF FEEDING PEAS TO HIGH-PRODUCING DAIRY-COWS

The effect of substituting peas for soybean and canola meals as a prot ein source in a high-producing dairy herd was studied in 66 Holstein c ows, divided into two groups based on stage of lactation, parity, leve l of milk production and days in milk. Two 18.5% crude protein grain c oncentrate diets were formulated based on the nutrient analyses of the forages available. The control grain mix contained standard protein s ources, principally soybean and canola meal (SBM\CM) while the test gr ain mix was formulated to contain approximately 25% field peas as the major source of protein. Both grain rations were formulated to the sam e nutrient specifications and balanced for undegradable protein. The d uration of the trial was 6 mo during which grain feeding levels were a djusted monthly based on milk yield. For cows in early lactation, 4% f at-corrected milk yield was higher (P < 0.05) for cows fed pea based c oncentrates (31.3 kg d(-1)) than for cows fed SBM/CM supplement (29.7 kg d(-1)). Fat-corrected milk yield was not affected by source of prot ein in mid- and late-lactation cows. Fat-corrected milk production was not different (P > 0.05) for cows fed SBM/CM compared with cows fed t he pea supplement when cows across all stages of lactation were includ ed in the analyses. Milk fat percent was significantly higher (P < 0.0 5) for early- and mid-lactation cows fed the pea supplement. The resul ts suggest that peas can be substituted for SBM\CM as a protein source for high-producing dairy cows.