ABSTRACT
1. Lipolytic rates expressed as mumol glycerol released per mg protein increased with body weight in Holstein steers. 2. Lipolytic rates were greatest in both inner and outer back fat and lowest in omental, perirenal, and intermuscular fat depots. 3. Epinephrine stimulated overall glycerol release 3-5-fold. 4. Fasting resulted in greater basal lipolytic rates but epinephrine-stimulated rates tended to be greater for nonfasted steer adipose tissue. 5. Lipolytic activity in adipose tissue seems to increase with growth and fattening, and differences in lipolytic rates between various depots diminish with growth.
Subject(s)
Adipose Tissue/metabolism , Lipolysis/physiology , Animals , Body Weight , Cattle , Epinephrine/physiology , Fasting/metabolism , In Vitro Techniques , Kinetics , MaleABSTRACT
The effect of monensin on methanogenesis was examined. Growing steers were fed 4.1 kg daily of a low roughage diet (12.6% crude protein, 12% acid detergent fiber) or 5.4 kg daily of either a medium roughage (12.3% crude protein, 27% acid detergent fiber) or a high roughage diet (14.4% crude protein, 40% acid detergent fiber) with or without 200 mg of supplemental monensin. At the low and high roughage levels, monensin increased (P less than .05) the molar proportion of ruminal propionate and decreased acetate. Methane production and inhibition by monensin declined with time postprandially. Monensin decreased methane production by 16% (P less than .05) at the two lower roughage levels and 24% (P less than .01) at the high roughage level. Total heat production and respiratory quotient remained unaltered by monensin. Averaged across roughage levels, metabolizable energy was increased (P less than .01) 5.2% by monensin. Although dry matter digestibility and N retention were not statistically altered, both tended to increase with monensin. Reduced ruminal methane production with monensin feeding can explain a portion of the increased feed efficiency.
Subject(s)
Cattle/metabolism , Furans/pharmacology , Methane/biosynthesis , Monensin/pharmacology , Animals , Dietary Fiber/metabolism , Male , Rumen/metabolismABSTRACT
Effects of nicotinic acid on glucose metabolism were studied in a series of experiments with goats. Oral administration of single doses of nicotinic acid (6.5 to 17.0 g) elevated blood glucose, impaired glucose tolerance, and elevated insulin. The magnitude of the effects was related positively to nicotinic acid dosage. Maximum effect occurred 2 to 3 days after administration. Blood glucose was elevated, with or without glucose administration, despite markedly elevated insulin. However, exogenous insulin given 48 h after nicotinic acid still reduced blood glucose although the response was delayed and was less than in control animals. A lactating cow given 160 g nicotinic acid exhibited alterations in glucose metabolism similar to control animals. These studies demonstrate that nicotinic acid, in addition to previously reported effects on lipid metabolism, also has significant effects on carbohydrate metabolism.
Subject(s)
Glucose/metabolism , Goats/metabolism , Insulin/metabolism , Nicotinic Acids/pharmacology , Animals , Glucose Tolerance Test/veterinary , Insulin/pharmacology , MaleABSTRACT
Blood samples and subcutaneous fat biopsies from six dairy cows at -14, 0, 14, and 28 days of parturition were analyzed to test the hypothesis that movement of calcium into subcutaneous fat contributes to hypocalcemia of parturient paresis. Plasma and subcutaneous fat calcium decreased while plasma free fatty acids increased at parturition. No trends were significant in magnesium or total lipid content of subcutaneous fat. Calcium content of subcutaneous fat was related positively to calcium concentration in plasma.
