Four rumen-fistulated steers, averaging 315 kg during two experimental periods were used in a replicated 2 X 2 Latin square study designed to determine the effects of monensin supplementation on rumen volatile fatty acid (VFA) production, pH and liquid volume. A 72% steam-flaked, sorghum grain diet was fed twice daily at 0700 and 1700 h at 2.0% of live body weight. Production rates were determined at 11 times during a 24-h feeding cycle by short-term in vitro incubations of whole rumen contents. Monensin increased moles/100 mol (P less than .05) and production rate (mumoles X liter-1 X min-1; P greater than .01) of propionate and depressed moles/100 mol (P less than .01) and production rate (P less than .05) of butyrate. Moles of acetate/100 mol were not affected (P greater than .05) by monensin. Daily propionate production (moles) was increased (P less than .01) by 37% by monensin. Monensin increased total production of acetate (11%) and total VFA production (16%), both nonsignificantly. Both rumen pH and liquid volumes were increased nonsignificantly by monensin.

Fourteen crossbred lambs with an average weight of 29.4 kg were utilized to determine the influence of the nature and amount of dietary lipid intake on the qualitative and quantitative composition of the plasma lipid, carcass depot fats and plasma insulin levels. Formaldehyde treated casein-cottonseed oil (PCO) was supplemented at the rate of 8% (three lambs) and 12% (three lambs). Two groups of four lamb each were assigned to diets containing no added fat (control) and 8% unprotected cottonseed oil (8% CO).Dietary lipid supplementation was effective in elevating (P<.05) the lipid levels of the blood. No difference (P>.05) in plasma insulin levels were detected between the four diets. Oil supplementation increased (P<.05) the concentration of linoleic acid in the four plasma lipid fractions: cholesterol esters, phospholipids, free fatty acids and triglycerides. Although not always statistically significant, the content of total unsaturates tended to increase (P<.05) in all plasma fractions.Subcutaneous fat biopsies obtained from the tailhead region at 0, 14, 42 and 84 days on feed revealed that the type of dietary fat fed was effective in altering the type of fatty acids deposited subcutaneously. Feeding cottonseed oil protected from rumen fermentation elevated the linoleic acid levels of subcutaneous fat, but the total unsaturated fatty acid levels were not different between diets. (

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