Effect of ensiling alfalfa at low and high dry matter on production of milk used to make Grana cheese

The effect of alfalfa ensiled in bunker silos at high moisture [HM, 34% dry matter (DM)] and low moisture (LM, 56% DM) content on milk production and Grana Padano cheese quality was studied. Forty Italian Friesian lactating cows were allotted to two groups and fed, in a crossover design experiment, two corn silage-based diets containing 27% of the total DM as HM or LM. Each of the two periods included 10 d of adaptation and 3 experimental weeks. Forage was cut in the mid-vegetative stage with, on average, 34% neutral detergent fiber and 19% crude protein (DM basis). The two alfalfa silages showed a different fermentation pattern with 4.04 and 1.25% of lactic acid, 1.95 and 0.42% of acetic acid, 9.1 and 4.8% of total N ammonia-N for HM and LM, respectively. No butyric acid was found. Clostridial spores and yeast showed no growth in both silages except in the first 2 wk of the experiment where slight aerobic deterioration occurred. The HM treatment resulted in slightly lower DM intake (19.3 vs. 19.9 kg/d) and milk protein content (3.33 vs. 3.38%), higher milk fat content (3.56 vs. 3.37%), and 4% fat-corrected milk (25.7 vs. 24.4 kg/d). Totally, 38 cheeses obtained from over 19 tons of milk with an average yield efficiency of 6.8%, were produced. The milk renneting and microbiological properties and the cheese quality were not significantly different between treatments. However, both treatments had on average 40% of low quality (butyric fermentation) cheeses observed mainly in the first 2 wk of the experiment, when the number of clostridial spores found in alfalfa silages was significantly higher than in the subsequent weeks. The data obtained suggest that the microbial quality of milk depends more on careful management and monitoring all of the steps in milk production, from silage harvest through to cheese making, than on the moisture level of alfalfa silage, provided that the latter is in a range of 35 to 55% DM.