Two experiments were carried out with sheep that originated from a fauna-free flock and were fed a soybean meal-corn silage diet with or without a bentonite supplement. One-half of the sheep fed each diet in each experiment were faunated with a mixed population of ruminal protozoa, whereas the other half of the sheep remained fauna-free until the end of both experiments. Wool growth and daily gain were measured in Exp. 1. (eight rams per treatment), which lasted 110 d, and the metabolic effects in the rumen and intestinal tract of protozoa and dietary bentonite supplement were tested with cannulated wethers (four wethers per treatment) in Exp. 2. The results of Exp. 1 showed decreased wool growth (P less than .05) due to the presence of protozoa in the rumen. Dietary supplementation with bentonite partly offset the decreased wool growth in sheep with protozoa, but there were no effects of dietary bentonite and no protozoa x bentonite interaction (P greater than .05). Daily gain was decreased by the dietary bentonite (P less than .05) supplement but was not affected (P greater than .05) by the ruminal presence of protozoa. In Exp. 2, protozoa increased (P less than .01) the ruminal concentrations of ammonia and decreased (P less than .05) the acetic:propionic acid molar ratio. Fractionation of N in the duodenal digesta flowing from the stomach to the small intestine showed that protozoa decreased (P less than .05) the flow of nonammonia N and bacterial N, and there was a protozoa x bentonite interaction for these effects (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Forty-eight rams, originating from a fauna-free flock, were divided into three groups of 16 and fed a corn silage-based diet that was unsupplemented (control) or included bentonite or monensin supplements. Eight rams in each group were inoculated with a mixed population of ruminal protozoa; the other rams remained free of protozoa throughout the 110-d experiment. The rams had free access to drinking water and assigned diet. All rams were killed at the end of the experiment, and ruminal and abomasal contents and livers were removed and sampled. Protozoal numbers in ruminal fluid of faunated rams were lower for groups fed bentonite or monensin supplements than for the control group. Bentonite decreased and monensin increased ruminal pH. The ruminal solubilities of Cu, Zn, and Mg were decreased by the presence of ruminal protozoa, but those of Fe, Mn, and Ca were not affected. Bentonite supplement decreased, and monensin supplement increased, the ruminal solubilities of Cu, Zn, and Mg. Protozoa increased the abomasal solubilities of Fe, but the other elements were not affected. Liver concentrations of Cu were decreased by bentonite and increased by monensin, but protozoa decreased the liver concentrations of both Cu and Mg. Liver concentration of Zn was affected by a monensin x protozoa interaction and that of Mg by a bentonite x protozoa interaction. It was concluded that chronic Cu poisoning could be accelerated by dietary supplements of monensin in sheep without ruminal microfauna, and the dietary Cu bioavailability could be decreased by dietary supplements of bentonite in sheep with a normal population of protozoa in the rumen.

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.

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Eighteen male crossbred sheep were assigned to three groups and fed corn silage (CS), corn silage and dicalcium phosphate (CS-DP) or corn silage and rock phosphate (CS-RP). The rock phosphate originated from an igneous deposit located in Cargill Township in Northern Ontario. The endogenous fecal loss of phosphorus (P) was estimated by the isotope dilution method using 32P as a tracer. The total fecal P and total fecal endogenous P increased with increasing P intake. However, the percentage of endogenous fecal P was in the order: CS > CS-DP > CS-RP. The true absorption of P was 75.1, 67.3 and 48.1% for CS, CS-DP and CS-RP, respectively. The availability of P from rock phosphate supplement is much lower than that from dicalcium phosphate supplement. Key words: Sheep, phosphorus, true absorption, corn silage, dicalcium phosphate, rock phosphate