Feeding equivalent concentrations of forage neutral detergent fiber from alfalfa hay, grass hay, wheat straw, and whole cottonseed in corn silage based diets to lactating cows

Diets with similar concentrations of equivalent forage neutral detergent fiber (FNDF) and nonfiber carbohydrates in corn-silage based diets could result in similar responses in ruminal function and animal performance. Four ruminally cannulated multiparous Holstein cows in late lactation were fed corn silage based total mixed rations with equivalent FNDF provided from alfalfa hay, grass hay, straw, or whole linted cottonseed (WCS). Formulated diets consisted of corn silage providing about 130g/kg FNDF with either alfalfa hay, grass hay or wheat straw that provided about 40g/kg FNDF. The fourth diet was formulated to consist of about 130g of FNDF/kg of dietary dry matter (DM) from corn silage and 52g of neutral detergent fiber (NDF)/kg of dietary DM from WCS, which is equivalent to 174g of FNDF/kg of DM in the diet if NDF from WCS is 0.84 as forage-like as alfalfa NDF. Treatment periods consisted of 21d. The FaNDF was about 20-30g/kg higher than anticipated at the onset of the study, primarily because the aNDF in corn silage was higher than expected. However, FaNDF was similar among the alfalfa hay, grass hay and straw diets, and about 40g/kg lower, as desired, for the cottonseed diet. The DM intake was similar among treatments, averaging 24.7kg/d. Milk yield was higher (P<0.05) for the cottonseed and grass hay diets than for the straw diet. However, because of numerical differences in milk fat and protein concentrations, milk energy output was similar among diets. Ruminal pH and total volatile fatty acid concentrations also were similar among diets. The WCS diet resulted in the lowest proportion of acetate and highest proportion of propionate, resulting in the lowest acetate:propionate ratio (P<0.05). Measures of ruminal mat consistency were similar among diets. Organic matter digestibilities among diets were similar, but the straw diet resulted in the highest (P<0.05) digestibility of aNDF and N. Feeding these diets to cows in late lactation provided evidence that alfalfa hay, grass hay, straw (low inclusion level) and WCS can be added on an equivalent FNDF basis to corn-silage based diets.