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Alfalfa saponins isolated by ethanol extraction and partial acid hydrolysis were intraruminally administered to sheep to investigate the biological activities and nutritional implications in ruminants. Mature wethers fitted with ruminal, duodenal and ileal cannulas were fed a concentrate or roughage diet formulated to be isonitrogenous and isoenergetic. Microbial fermentation and nutrient degradation in the rumen were reduced by saponins. Total protozoal count in the rumen was reduced 34 and 66% by saponins at levels of 2 and 4% dietary dry matter, respectively. Bacterial nitrogen flow to the duodenum was reduced 20 and 30% in the same sequence. Apparent digestion coefficients of organic matter, hemicellulose and cellulose in the total digestive tract were increased by saponins in sheep fed concentrate diets. Fractional digestion coefficients of organic matter, hemicellulose, cellulose and nitrogen were reduced in the stomach while they were increased in the small intestine by saponins in both diets. Saponins inhibited microbial fermentation and synthesis in the rumen and altered the sites of nutrient digestion in sheep.

Two trials were conducted to determine particle size of masticates, ruminal digesta, and feces of dairy cows. In Trial 1, three Holstein cows with ruminal cannulae were fed prebloom alfalfa hay in long, chopped, or pelleted form in a Latin square design (21-d periods) conducted in early lactation (wk 3 to 11) and again during the dry period to attain high (3.75) and low (1.95% of BW) feed consumption. In trial 2, prebloom, midbloom, and full bloom alfalfa hay, mature bromegrass hay, and corn silage were fed to early lactation (wk 5 to 15) Holsteins in a 5 X 5 Latin square design (15-d periods). All diets (Trials 1 and 2) were formulated to 17% CP and contained forage:grain in a 60:40 ratio (DM basis). Similar particle distributions of digesta from long and chopped hay diets suggest little influence of chopping forage on particle size reduction when high quality forage is fed. The large proportion of DM in the small particle (less than .6 mm) pool in the rumen in both trials suggests that rate of escape of small particles from the rumen is an important factor influencing ruminal retention time. Increased proportion of coarse (greater than or equal to 2.36-mm screen) fecal particles at high intake and with fine grinding appears related to a reduction in chewing per unit feed consumed. Soluble DM and particulate matter passing a .063-mm screen made up a significant portion (30 to 50%) of the total DM sieved from all sampling sites in both trials.

The pH optimum of pancreatic alpha-amylase from grain-fed steers was determined to be 6.9, while that of intestinal maltase was established at 5.8. Both assays were found to be linear up to 1 hr of incubation. The V max of pancreatic amylase was determined to be pancreatic amylase was determined to be 1.15 mg of maltose monohydrate produced/hr. Activities of pancreatic and intestinal maltase were not reduced (P greater than .05) during the interval from sample collection from the animal until analysis 4 hr later when tissues were kept on ice. Twenty-four yearling Holstein steers fed either alfalfa hay at a maintenance level of metabolizable energy (ME) intake or corn at one, two or three times the maintenance ME intake level were slaughtered after being fed 106 days. The pancreas was removed alone with sections of the intestine. Specific activity of pancreatic amylase for steers fed the high level of corn was 129% of that for steers fed the alfalfa diet (P greater than .05). Intestinal maltase activity was highest in the jejunum and decreased toward the ileum. Increasing dietary starch intake resulted in no response (P greater than .05) in maltase activity at 10, 30, 50, 70, or 90% of the small intestine length. The effect of dietary starch level on dieesta pH was dependent on sampling location within the small intestine. There were no dietary effects (P greater than .05) on digesta pH for the first 10% segment of intestine distal to the pylorus. However, in all subsequent sections, digesta pH was higher steers fed the alfalfa diet than for those fed the two higher levels of grain. A calculation for estimating th amount of pancreatic amylase needed to hydrolyze starch presented to small intestine is discussed.

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Two trials were conducted to study the effects of forage intake and physical form on lactating cow performance. In trial 1, four cows in a 4 X 4 Latin square were fed long alfalfa hay at 28, 36, 45, and 53% of total dry matter plus concentrate. Total dry matter intake was not affected by forage percent. Total chewing time and milk fat percentage increased linearly with increasing forage consumption. Maximum 4% fat-corrected milk production occurred when diets contained 27% neutral detergent fiber and 18% acid detergent fiber. In trial 2, four cows in a 4 X 4 Latin square were fed diets of chopped alfalfa hay and concentrate in proportions to supply 27.4% total ration neutral detergent fiber. Mean particle length measured with an oscillating screen particle separator of the chopped hay was .26, .46, .64, and .90 cm. Total dry matter and forage dry matter intakes and total chewing were not influenced by forage mean particle length. Mean particle length did not affect actual milk or 4% fat-corrected milk production. Depression of milk fat percentage was prevented when forage mean particle length was greater than or equal .64 cm. Apparent digestibility of dietary constituents and rate of passage of hay and concentrate was not influenced by forage intake or physical form.

The milk from cows fed normal levels of vitamin D has been found to contain approximately 40 IU per liter of vitamin D activity. A 14-fold increase in dietary vitamin D intake causes only a doubling of the amount of vitamin D in milk. This was determined by measuring stimulation of intestinal calcium transport in the vitamin D-deficient rat. Four vitamin D compounds were then isolated from cow's milk using a combination of conventional chromatography on Sephadex LH-20 and Lipidex 5000 followed by high-performance liquid chromatography. 24,25-Dihydroxycholecalciferol and 1,25-dihydroxycholecalciferol were measured using binding protein assays. One liter of milk contained 27 ng and 4.9 ng, respectively, of these two metabolites. Together these account for about 15% of the vitamin D activity. Cholecalciferol was found to be present at a concentration of 281 ng/liter or 11 IU/liter of biological activity. The milk contained 145 ng/liter 25-hydroxycholecalciferol or 29 IU/liter of activity. Therefore the known vitamin D compounds fully account for the biological activity observed in milk. It is therefore clear that no evidence could be found for the existence of a highly active water-soluble form of vitamin D in milk.

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