CORN SILAGE is an excellent forage source, but silages are often inadequate for Alabama dairy farms. Therefore, dairy producers must find alternative forage sources that are economical, easy to mix in total rations, and support satisfactory milk production. AAES research indicates that cottonseed hulls may provide an economical and effective alternative for dairy producers.

Typical forage sources used by dairy producers include alfalfa and grass hat. The availability of alfalfa hay, however, is limited, expensive to import, and it must be chopped if used in total mixed rations (TMR). Grass hay quality often is low, the supply may be limited, and it also must be chopped if used in TMR. Cottonseed hulls, byproducts of the region's thriving cotton industry, are often an economical source of roughage and mix well in TMR.

Protein sources also are of interest because milk yield may increase if cows are fed certain feed combinations. Best results are often obtained with protein sources that are partially digested in the rumen with the remainder undigested in the rumen (UIP) but digested in the lower gastrointestinal tract. To get such digestion, a mixture of protein sources such as soybean meal and various byproduct protein supplements are considered advantageous. However, forage sources may affect the protein digested in the rumen, and therefore affects the value of protein sources.

To learn more about the value of cottonseed hulls in dairy cattle diets and their effects on protein sources, two studies were conducted at the E. V. Smith Research Center Dairy Unit in Shorter. In the first study, 72 early-lactation Holstein cows were fed diets (1) corn silage as the only forage, or diets in which (2) cottonseed hulls, (3) coastal bermudagrass hay, or (4) alfalfa hay replaced 10% of the corn silage on the dry matter (OM) basis. All diets were equal in crude protein (16.5%), net energy for lactation (NEL, 0.74 Mcal per pound), and mineral contents.

For each forage source, nine cows were fed either soybean meal as a low UIP supplement or a soybean, feather, and blood meal combination as a high UIP supplement. Milk, milk composition, feed intake, body weights, and metabolic compound data were collected for 10 weeks.

Forage and protein sources had little if any effect on body weight and rumen pH indicating that the rumen function of cows fed these diets was normal. Effects of dietary treatments on milk production and feed intake are presented in Table 1. Cows on the low UIP diets ate more feed than cows on the high UIP diets regardless of the forage source.

Cows on the cottonseed hull diets ate more feed than those fed diets containing all com silage, 10% alfalfa hay, or 10% bermudagrass hay. Cows consuming cottonseed hull diets produced more milk when they were fed high UIP than low UIP sources. This did not occur for other forage sources. Although there were some variations, neither forage nor protein supplement had a clear effect on butterfat content. The high UIP sources caused a depression of milk protein when cows were fed diets with 10% hay or cottonseed hulls.

Because the addition of 10% cottonseed hulls with the high UIP diet enhanced feed intake and milk production, a second study using 54 mid-lactation cows was conducted to evaluate the effect of higher levels of cottonseed hull with low or high UIP sources. Dietary treatments were (1) 10% cottonseed hull and 36-38% corn silage, (2) 20% cottonseed hull and 16-19% com silage, and (3) 30% cottonseed hull and no corn silage. All diets were equal in crude protein (16.0%), energy (NEL, 0.74 Mcal per pound), and mineral contents. As in body weight or rumen pH; however, they did affect dry matter intake, milk yield, milk composition, and blood urea nitrogen (Table 2). As the amount of cottonseed hulls in the diet increased, dry matter intake increased, but there was no increase in milk production. Cows on high UIP diets consumed less feed than those on the low UIP diets, yet they produced more milk than those fed low UIP sources. Cows on high UIP sources produced milk with lower butterfat content and depressed milk protein when cows were fed diets with 30% cottonseed hulls. The lower blood urea nitrogen values for the cows on high UIP diets may indicate better utilization of the protein fed.

Based on these results, it appears that cottonseed hulls provide several advantages for dairy producers. Data indicate that cows may produce as well when receiving cottonseed hulls as corn silage if the diets are well balanced. Feeding high UIP sources, such as feather or blood meal, with cottonseed hulls produced more milk than only soybean meal when fed with cottonseed hulls. Therefore, producers should consider feeding some cottonseed hulls with higher amounts of UIP.

Gu is a Graduate Research Assistant, Moss is a Professor and Lin is a Research Associate of Animal and Dairy Sciences.