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Digestion and Nutrient Flow in the Gastrointestinal Tract of Sheep Fed Alfalfa Protein Concentrate Prepared by Various Methods^1,2,

University of Wisconsin, Madison 53706

Abstract

Mature wethers fitted with duodenal and ileal T-type cannulae were used to study effects of temperature at coagulation, anaerobic fermentation and dehydration on the utilization of alfalfa protein concentrate. Alfalfa protein concentrates (APC) were heat-coagulated at 80 C without drying (APC-80), heat-coagulated at 80 C and spray-dried (APC-80-SD), coagulated by anaerobic fermentation and spray-dried (APC-Ferment-SD) or heat-coagulated at 100 C and spray-dried (APC-100-SD). Isonitrogenous and isoenergetic diets containing APC were fed. Organic matter (OM) flow to the duodenum as a percentage of OM intake was 56.8, 57.8, 50.2 and 54.3 for diets containing APC-80, APC-80-SD, APC-Ferment-SD and APC-100-SD, respectively. Ruminal NH₃-N concentration was lowest (P<.05) in sheep fed APC-80-SD, while total VFA concentration was highest (P<.05) in sheep fed APC-Ferment-SD. Ruminal turnover rate, turnover rate in the hindgut, total mean retention time and transit time through the hindgut were not different among treatments. Total nanammonia N reaching the duodenum was 27.6, 34.1, 27.3 and 26.4 g/d in sheep fed diets containing APC-80, APC-80-SD, APC-Ferment-SD and APC-100-SD, respectively. Bacterial N reaching the duodenum averaged 15.6 g/d and was similar among treatments. Natural fermentation resulted in APC with the highest nonprotein N content and less resistance to ruminal degradation. APC prepared by heat coagulation at 100 C did not increase resistance to ruminal degradation or adversely affect digestion in the small intestine.

¹ Research supported by the College of Agricultural and Life Sciences, Univ. of Wisconsin, Madison; Hatch project 6003.

² Authors gratefully acknowledge Dr. R. J. Early, for his assistance in surgical preparation, Ms. K. B. Smith, for technical assistance in chemical analysis, and Dr. C. H. Amundson, for drying of alfalfa protein concentrate.

³ Dept. of Dairy Sci.

⁴ Dept. of Meat and Anim. Sci.

⁵ Dept. of Agr. Eng.