Effects of decreased availability of glucose for dairy cows.

After a preliminary trial to establish dose responses to phlorizin, five Holstein cows at 6 wk postpartum were used to test the response of cows in negative energy balance to a sudden decrease in availability of glucose caused by phlorizin. Cows were fed equal amounts of feed twice daily to supply 100% of NRC recommendations for protein and 90% of NRC recommendations for NEL and were in negative energy balance throughout the experiment. Phlorizin at 0, 2, and 4 g/d was injected subcutaneously in equal amounts every 6 h for 48 h and caused excretion of 0, 225, and 337 g/d of glucose in urine.

Effect of adipose tissue site, animal size, and fasting on lipolysis in bovine adipose tissue in vitro.

1. Lipolytic rates expressed as mumol glycerol released per mg protein increased with body weight in Holstein steers. 2.

Metabolism of propionate, glucose, and carbon dioxide as affected by exogenous glucose in dairy cows at energy equilibrium.

In vivo kinetic techniques were used to quantify changes in metabolism of propionate, glucose, and blood CO2 when glucose was infused intravenously at 0, 342, or 737 g/d into four lactating cows. Neither production of milk or milk fat nor composition of milk was changed. Production of milk protein increased for the high glucose treatment.

Cholesterol transport and uptake in miniature swine fed vegetable and animal fats and proteins. 2. LDL uptake and cholesterol distribution in tissues.

In a 2 X 2 factorial arrangement, miniature pigs were fed four diets containing vegetable protein/fat (soybean) and animal protein (egg white)/fat (beef tallow) to demonstrate the effects of protein and fat source on tissue cholesterol concentrations, uptake of intact low density lipoproteins (LDL) and free cholesterol exchange from LDL to tissues. Soybean oil feeding, compared with beef tallow feeding, resulted in greater concentrations of cholesterol in aorta, heart, and large and small intestines. Similar trends were seen in liver, adipose tissue and skeletal muscle.

Cholesterol transport and uptake in miniature swine fed vegetable and animal fats and proteins. 1. Plasma lipoproteins and LDL clearance.

In a 2 X 2 factorial arrangement, miniature pigs were fed four diets containing vegetable protein/fat (soybean) and animal protein (egg white)/fat (beef tallow) to demonstrate the effects of protein and fat source on total plasma cholesterol, lipoprotein distribution, low density lipoprotein (LDL) composition, and plasma clearance of LDL-cholesterol and protein. Beef tallow consumption resulted in greater plasma cholesterol concentration, decreased LDL-cholesterol concentration, and a lower LDL-cholesterol to LDL-protein ratio than did consumption of soybean oil. High density lipoprotein (HDL)-cholesterol concentration was increased by beef tallow consumption.

Cholesterol transport in mesenteric lymph of the preruminant calf: contribution of cholesterol transposition from blood to lymph.

Eight preruminant male calves were prepared surgically with lymphatico-venous shunts and re-entrant gallbladder to proximal duodenum shunts. Liquid diets were formulated to contain 12.5% dried skim milk (SM) or 10.

Quantitation of fat and cholesterol transport in the mesenteric lymph and bile of the preruminant calf.

Nine preruminant male calves were prepared surgically with lymphatico-venous shunts and/or re-entrant gallbladder to proximal duodenum shunts to evaluate the effects of degree of saturation of dietary fat on cholesterol transport in intestinal lymph and bile. Liquid diets were formulated to contain 12.5% dried skim milk (SM) or 10.

Effects of dietary fat on amounts of cholesterol transported by mesenteric lymph in calves fed milk.

Five nonruminating male calves were prepared surgically with shunts from mesenteric lymph duct to posterior vena cava and sequentially were fed diets of reconstituted skim milk and skim milk plus supplemental cholesterol plus soybean oil, beef tallow, or milk fat. Calves received skim milk for 2 days, followed by the other diets for 4 days each in a predetermined order. On the 2nd and 4th day each diet was fed, lymph was collected hourly for 8 h, starting 1 h before the morning feeding.

Effects of intravenously infused zeranol on glucose kinetics in growing Holstein steers.

Four Holstein steers fed 2.86 kg of corn and 3.50 kg of chopped alfalfa hay in 12 equal portions daily were used to determine effects of intravenously infused zeranol on glucose kinetics.

Effect of type of dietary fat on plasma and tissue cholesterol of calves.

Two experiments were conducted to examine the effects of liquid milk diets with varying proportions of beef tallow (T) and soybean oil (SBO), with and without dry feed, on cholesterol concentrations in blood and other tissues of nonruminating calves. In experiment 1, 4--10-day-old male Holstein calves were fed for 15 weeks a reconstituted milk containing 9% ot 12% dried skim milk and 2% SBO, 2% T or 3.5% T.

Rumen propionate and blood glucose kinetics in growing cattle fed isoenergetic diets.

The relationship between rumen propionate production and blood glucose kinetics was examined in four rumen-fistulated Holstein steers fed isoenergetic amounts of 80/20 (G) and 30/70 (R) grain/chopped alfalfa hay diets at 2-hour intervals. Single-injection rumen propionate and blood glucose kinetics were determined in consecutive 4-hour periods by using [6-3H]glucose intravenously then [1-14C]propionate intraruminally. Rumen propionate specific activity was determined after isolation and quantitation by high-pressure liquid chromatography.

Effects of monensin on in vivo rumen propionate production and blood glucose kinetics in cattle.

Four rumen-fistulated steers (154 to 253 kg), fed two different diets in succession, were used to determine effects of monensin on rumen propionate production rates and blood glucose kinetics as determined by single-injection isotope-dilution techniques. A high-roughage and a high-grain diet, with and without 150 mg of monensin daily, were fed isoenergetically at 2-hour intervals. Monensin increased rumen propionate pool sizes from 32 to 57 g for the high-roughage diet and from 37 to 66 g for the high-grain diet and increased rumen propionate production rates from 441 to 659 g/day for the high-roughage diet and from 510 to 899 g/day for the high-grain diet.

Gluconeogenesis in ruminants: propionic acid production from a high-grain diet fed to cattle.

Effects of amount of feed intake on in vivo remen propionate production and the reproducibility of measurements of propionate production rates were investigated in five dairy steers weighing 142 to 228 kg. Each steer received 275 g of an 80%-grain diet every 2 hours, and three of the five steers later received 500 g/2 hours. Rumen propionate pool sizes and production rates were determined at both intakes by administering a single dose of [1-14C] propionate via rumen fistula and observing decreasing specific activity of rumen propionate for 4 hours.

Volatile fatty acid metabolism by rumen mucosa from cattle fed hay or grain.

Effects of an all-grain versus an all-hay diet on metabolic activity of rumen mucosa of cattle were investigated. After diets had been fed for 3 to 4 mo, rumen papillae were collected at slaughter from the dorsal rumen sac and incubated with one of various volatile fatty acids. Rates of substrate utilization were in the order: n-butyrate greater than n-valerate approximately propionate greater than iso-butyrate approximately iso-valerate.

Extent of propionate metabolism during absorption from the bovine ruminoreticulum.

1. Solutions containing acetate, [2-(14)C]propionate and butyrate were placed into the ruminoreticulum of calves to measure the extent to which propionate is metabolized by ruminoreticulum epithelium. In response to five different combinations of pH and total volatile fatty acid concentrations, propionate absorption rates ranged from 89 to 341mmol/h.