Effect of method of feeding protein and protein insolubility on milk production by Jersey cows

Each of two feeding trials used 32 first and second lactation Jersey cows to evaluate four methods of protein supplementation of corn silage: A) 20% crude protein grain mixture, B) 1.36 kg of soybean meal replaced an equal amount of grain mixture, C) 2.27 kg of alfalfa-orchardgrass hay daily and 16% crude protein grain mixture, and D) 2.72 kg of soybean meal mixed with the silage daily. Concentrates were fed at 1 to 4 kg fat-corrected milk for treatments A, B, and C. All cows received 1.18 kg of 16% crude protein concentrate mixture daily in the milking parlor. Protein contents, as percents of dry matter intake, for respective treatments were 12.9, 15.0, 12.7, and 17.2. Treatments did not differ significantly for milk production, fat-corrected milk, and change of body weight; however, percents milk fat for 1.36 and 2.72 kg soybean meal were higher. In trial 2, protein insolubility of ration components was determined by four extracting methods: A) autoclaved rumen fluid, B) sodium chloride solution, C) Burroughs' solution, and D) boiling water. Insoluble protein intake determined by autoclaved rumen fluid and hot water methods accounted for more of the variance of milk and fat-corrected milk production than total protein intake.