Duodenal Flow of Microbial and Feed Nitrogen In Sheep Fed Normal Soybean Meal or Soybean Meal Treated with Modified Zein

¹ Centre for Food and Animal Research, Agriculture and Agri-Food Canada, Ottawa, ON, Canada K1A 0C6

The effect of protecting soybean meal from microbial degradation in the rumen on duodenal flow of microbial N and feed N was studied with sheep. The soybean meal was protected with chemically modified zein. Two groups of four wethers, each equipped with a ruminal cannula and a duodenal reentrant cannula, were fed a diet based on corn silage (1 kg of DM/d) that contained either a normal or protected soybean meal supplement. The results showed no appreciable differences between the two supplements in ruminal fluid pH, total N, and NAN concentrations; however, the concentration of total VFA was lower for protected soybean meal than for normal soybean meal. Although the flow of NAN into the duodenum was not affected, bacterial N flow was 18% lower, and feed N flow was 195% higher, for protected soybean meal than for normal soybean meal. The digestibilities of OM, ADF, and N in the digestive tract were not affected by the type of supplement. The treatment of soybean meal decreased the degradability of total feed N in the stomach by 22 percentage points, but the increased supply of feed N into the small intestine because of the treatment was at the expense of decreased bacterial synthesis of protein in the rumen, probably because of a shortage of RDP in the diet.

Key Words: soybean meal • nitrogen • sheep

Submitted on December 29, 1994
Accepted on September 12, 1995

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