Fermentation characteristics and nutritional value of stored and fresh dairy cattle waste ensiled with crop residues

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Virginia Polytechnic Institute and State University


A small silo study was conducted to determine the optimum combination of slurry and fresh dairy waste and crop residues to achieve good ensiling. Slurry waste that had been accumulated in slurry storage tanks and dairy waste scraped from the barn were ensiled with ground corn stover, with and without the addition of 5% molasses, to achieve two dry matter levels of 30 and 35%.

Fermentation, as measured by pH, lactic acid and disappearance of soluble carbohydrates, occurred in all silage mixtures. Lactic acid levels indicated that a more desirable fermentation had occurred in the waste silages containing molasses. Total and fecal coliforms and salmonella, shigella and proteus organisms were either destroyed or essentially eliminated following ensiling.

A large silo study was conducted with the mixtures containing molasses. The fresh waste was diluted with water to achieve the same dry matter levels as the slurry waste. The mixtures for the 30 and 40% dry matter levels were 71:39 and 64:36 cattle waste to wheat straw, wet basis.

Active fermentation occurred in all silages and pH was lower and lactic acid levels were much higher than they were in the small silo.

In a metabolism trial conducted with lambs, the following diets were fed: 1) 50% orchardgrass hay, 38.3% ground corn, 11.4% soybean meal and .3% limestone (basal diet); 2) 50% basal and 50% ground wheat straw ensiled at 50% dry matter (negative control); 3) 50% basal and 50% 71:29 slurry-wheat straw silage; 4) 50% basal and 50% 64:36 slurry-wheat straw silage; 5) 50% basal and 50% 71:29 fresh waste-wheat straw silage and 50% basal and 50% 64:36 fresh waste-wheat straw silage (proportions of basal and silages were on a dry basis).

Apparent dry matter digestibility was higher (P < .01) for the basal diet than for the silage diets and was higher for the waste containing silages (P < .05) than for the wheat straw silage diet. Dry matter digestibility of the waste-containing silages, calculated by difference, was not different, but was higher (P < .01) than for the ensiled wheat straw alone. Nitrogen digestibility was higher (P < .05) for the waste containing silages, compared to the wheat straw silage but lower (P < .05) than the basal ration.

All lambs were in positive nitrogen balance, with the lambs fed the 71:39 slurry waste silage slightly higher than for those fed the other diets. The lambs fed the basal and wheat straw silages had similar nitrogen retention.

Ruminal ammonia levels were highest (P < .05) for the lambs fed the basal and lowest for those fed the wheat straw silage diet. There were no significant differences (P < .05) among the waste-containing silages.

The palatability trial with lambs was conducted using 50% basal and 50% of the silages, dry basis. Dry matter intake was highest (P < .05) for the basal diet. Dry matter intake among the silage diets was lowest (P < .05) for the slurry waste silage diets. Among the waste-containing silage diets, dry matter intake tended to be higher for the fresh waste silages, compared to the slurry waste silages of similar dry matter.