Effects of maize and alfalfa genotypes on dairy cow performances

Abstract

In this trial, we attempted to evaluate the effects of alfalfa and maize genotypes fed to dairy cows. These genotypes were chosen from records of previous trials with sheep for either their high or low digestibility. Thirty-two cows were fed a diet based on maize silage ad libitum (M+ or M- genotype) and alfalfa (A+ or A-) pellets (4.35 kg/day) in a 2 × 2 factorial experiment. Silage intake, milk yield and composition, body weight and body condition scores were recorded during the 15-week experiment. The maize genotype of high digestibility (M+) tended to be ingested in larger quantities (14.4 vs 14.0 kg/cow/d) than the other genotype (M-), although showing a lower dry matter content (29.5 vs 31.2%). With this improved genotype, the milk yield was significantly higher (28.1 vs 26.9 kg/cow/day; P = 0.01) without decreasing effects in the fat and protein content of the milk, but with the cows increasing their body reserves (28.1 kg, P < 0.01). No differences were observed in the body condition scores. The alfalfa effects were not so acute, but the distribution of the improved genotype (A+) improved the daily milk yield (28.0 vs 27.0 kg/day, P = 0.03) and the body condition scores (P = 0.04). These principal effects appeared to be additive. The diet built with the best genotypes (M+ A+ diet) provided 2.2 kg milk/cow/day more than with the inferior ones (M- A- diet), displaying a higher body weight gain and better body conditions, without showing any negative effects on the fat and protein contents. Thus, the choice of a given genotype (maize or alfalfa in this case) may have strong effect on cow performances. In the European Union, where each farmer has a milk quota, the choice of an improved maize or alfalfa genotype could be essential in limiting production costs.