In one of two experiments, six 4-mo-old wethers fitted with ileal and cecal cannulas were fed three levels of concentrate (0, 40 or 80% corn) with forage in a replicated 3 X 3 Latin square design. Chromic oxide was fed as a marker. Quantities of starch recovered at the ileum and digested in the large intestine increased (P less than .05) with increased starch intake. Quantities of acid detergent fiber (ADF) recovered at the ileum increased with increased ADF intake; however; ADF digestion (grams) in the large intestine was highest (P less than .05) when the 80% corn diet was fed. Cecal total VFA concentrations, butyrate molar proportions and lactic acid concentrations were highest (P less than .05), and cecal acetate to propionate (C2:C3) ratios and pH values were lowest, in lambs fed 80% corn. In Exp. 2, 14 wethers (4-mo-old) were fed a forage (alfalfa hay) or a concentrate (80% corn) diet containing chromic oxide as a marker. Digesta grab samples were obtained by surgical procedure. The amounts of starch recovered at the abomasum and ileum and the amounts digested in the rumen, small intestine and large intestine were greater (P less than .05) when lambs were fed the concentrate. Large intestinal total VFA concentrations and butyrate molar proportions were higher (P less than .01) when the concentrate diet was fed; pH values were lower (P less than .01). Lambs fed the concentrate diet had lower (P less than .01) large intestinal and ruminal C2:C3 ratios of VFA.
Sixteen male Holstein calves were fed milk replacer (14% solids) containing 23% crude protein from: 100% milk protein; or 66% soybean protein concentrate plus 34% milk protein as the only nutrients at 8, 9, 10, 11, 12, 12, and 12% body weight from 1 to 7 wk of age, respectively. Eight calves were sensitized to soybean by feeding 66% soybean protein concentrate plus 34% milk protein for 21 d and eight were not sensitized by feeding 100% milk protein. Afterward, each calf received one of the diets for 10 d followed by the other diet for an additional 10 d. During the 2nd wk of the initial period each calf was surgically fitted with a duodenal cannula for biopsy of intestinal mucosa. Biopsies were taken at surgery and on the last day of each period. Feeding 66% soybean protein concentrate plus 34% milk protein resulted in lower body weight gain, decreased feed efficiency, higher rectal temperatures, increased diarrhea, and villus atrophy. Diminished villi size supports other studies reporting allergic reaction to soybean protein and was associated with the poor performance observed in calves fed soybean protein.
An in situ ovine liver perfusion technique was developed and used to study glucagon effects on utilization of simultaneously infused propionic acid and amino acids. Physiological amounts of propionic acid and amino acids (hydrolyzed casein) were infused into livers along with carbon-14 propionic acid or carbon-14 threonine with and without glucagon. Glucagon (5 mg) caused a 75% increase of glucose synthesis and a 19% increase of labeled carbon dioxide production from carbon-14 propionic acid. There also was a decrease of perfusate urea nitrogen when glucagon was present. Glucagon caused a 76% decrease of carbon-14 threonine utilization by ovine livers, and labeled carbon dioxide production from carbon-14 threonine was only 38% of control when glucagon was infused. From these results, glucagon caused an increase of use of propionic acid and a decrease of use of threonine for energetic pathways in sheep liver. Therefore, glucagon directly or indirectly may mediate amino acid sparing by ruminant liver.
Eight ewes weighing about 52 kg were used in a 2 X 2 factorial arrangement of treatments replicated with temperature reversal to determine the effect of cold exposure on plasma Mg, Ca, free fatty acids (FFA), glucose and insulin concentrations and on renal clearance of Mg and Ca. Closely sheared ewes were fed a complete mixed diet at either 1.5% of body weight with no pretreatment fast or fed ad libitum followed by fasting 3 days before initiation of temperature treatments. Fasting superimposed on cold exposure reduced (P less than 0.01) plasma Mg at 1 hour after exposure to cold, and this effect continued during the cold treatment period, whereas Mg concentration was not significantly affected in fed sheep. Plasma FFA measured across temperature treatments was increased (P less than 0.01) by fasting. FFA measured across dietary treatments was only slightly increased by cold exposure. Plasma glucose levels of fasting sheep were lower (P less than 0.05) than those of fed sheep; however, levels rose (P less than 0.05) after exposure to cold. A tendency for plasma insulin to increase after cold stress was observed. Renal clearances of Mg and Ca were markedly reduced (P less than 0.01) by fasting, but clearance was not changed by cold stress. These results suggest that exposure to cold (2-5 degrees) and a deficient dietary intake synergistically reduce plasma Mg in sheep.
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