SmallRuminant Research, 3 (1990) 425-434 425 Elsevier Science Publishers B.V., Amsterdam Performance of dairy goats fed isonitrogenous diets containing soybean meal or hydrolyzed feather meal during early lactation C.D. Lu, M.J. Potchoiba, T. Sahlu and J.M. Fernandez American Institute for Goat Research, Langston University, Langston, OK 73050, US.A. (Accepted 26 May 1989) ABSTRACT Lu, C.D., Potchoiba, M.J., Sahlu, T. and Fernandez, J.M., 1990. Performance of dairy goats fed iso- nitrogenous diets containingsoybean meal or hydrolyzed feather meal during early lactation. Small Rumin. Res., 3: 425-434. Lactating dairy goats were utilized in a 105-day continuous feeding experiment to compare hydro- lyzed feather meal with soybean meal as a protein supplement for milk production. Treatments were isonitrogenous and isoenergetic diets containing soybean meal or hydrolyzed feather meal. Fifty per- cent of total dietary nitrogen was provided by test proteins. Ruminal ammonia nitrogen ( 16. l vs. 4,7 mg/dl) and total volatile fatty acids (79.5 vs. 69.6 mM) were lower in goats fed hydrolyzed feather meal. Dry matter intake (2.90 vs. 2.52 kg/day), live body weight (48.1 vs. 47.7 kg) and milk yield (3.20 vs. 3.16 kg/day) were similar between treatments. Milk protein content and yield, true protein N, and casein N were lower in goats fed hydrolyzed feather meal. Serum total protein and urea N were lower in goats fed hydrolyzed feather meal while plasma glucose was similar between treatments. Feed efficiency (kg 4% fat-corrected milk/kg dry matter) was slightly higher in goats fed hydrolyzed feather meal and no differences were observed in energy and protein efficiencies. Limitation in microbial protein synthesis due to suboptimal NH3-N concentration in the tureen and quality of protein avail- able for intestinal absorption may be important in the utilization of hydrolyzed feather meal for milk production. INTRODUCTION Feather meal, a keratin protein, is a high potential protein source for ru- minants (88% CP, DM basis) and is relatively insoluble in the rumen (Thomas and Beeson, 1977 ). Hydrolyzed feather meal (HFM), a product resulting from high temperature autoclaving, was reported to be highly diges- tible in rats (McCasland and Richardson, 1966). However, HFM was found to be limiting in methionine, lysine and tryptophan in poultry (Morand et al., 1966). This was thought to be less critical in ruminants due to microbial pro- tein degradation and synthesis in the rumen. Utilization of feather meal by sheep and cattle has been reported (Huston and Shelton, 1971; Wray et al., 0921-4488/90/$03.50 © 1990 -- Elsevier Science Publishers B.V.