Regression of brown adipose tissue mitochondrial function and structure in neonatal goats.

Rapidly regressing perirenal brown adipose tissue (BAT) of neonatal goats was studied to correlate changes in mitochondrial metabolism and thermogenic capacity with changes in mitochondrial structure. The alpha-glycerophosphate shuttle activity of perirenal BAT mitochondria declined 60% from birth to 6 days of age. Oxygen consumption and thermogenic capacity measured by ion conductance peaked at birth and declined to low levels at 6 days. Sample electron micrographs of perirenal BAT showed intact electron-dense mitochondria with many cristae and little matrix area at 2 days. However, by 6 days the mitochondria were very relaxed with large matrix area, few cristae, and observable degradation. These results indicate that the morphological changes exhibited by rapidly regressing goat's perirenal BAT in the 1st wk postpartum are accompanied by dramatic alterations in BAT mitochondrial function.

Chewing efficiency and body size of kid goats.

Thirty-two observations were made on 27 goats (18 mature, nonlactating females and 9 doe kids) to study the relationship among metabolic body size (body weight X 75), cell wall constituent intake, and chewing efficiency. A jaw motion recorder determined the minutes spent eating and ruminating during 24 h. Greater cell wall intake increased the amount of cell wall chewed per minute. Body size was directly related to cell wall eaten and ruminated per minute. In 2- and 3-mo-old kids, incomplete development of rumen function and body size both appeared to affect chewing efficiency. The chewing efficiency of 9-mo-old kids resembled that of the mature goats after adjustments for body size. Because rumination time seldom exceeds 10 h per day, the efficiency with which the time available for rumination is used will affect intake.