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ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #91980
Title: METABOLISM AND MORPHOLOGY OF BROWN ADIPOSE TISSUE FROM BRAHMAN AND ANGUS NEWBORN CALVES

Author
item MARTIN, GAIL - TEXAS A&M UNIVERSITY
item KING, MELISSA - TEXAS A&M UNIVERSITY
item CARSTENS, GORDON - TEXAS A&M UNIVERSITY
item ELI, ALANA - TEXAS A&M UNIVERSITY
item Mersmann, Harry
item SMITH, STEPHEN - TEXAS A&M UNIVERSITY

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: The survival rate of newborn Brahman cattle is less than that of Angus newborns. Tolerance of cold temperatures can be a key factor in survival when calves are born in the fall and spring. Brown fat is a special type of fat that provides the newborn with energy and generates heat. We wanted to find out whether there are differences between the two breed types in regard to the way their brown fat functions to produce heat, which has a protective effect in newborn calves. We obtained eight pregnant purebred Brahman and eight pregnant purebred Angus cows, and then studied their offspring. We found that the breed types do not differ in their capacity to generate heat via brown fat. This is useful scientific information in terms of understanding the factors that might, and might not, affect health and neonatal mortality rates.

Technical Abstract: Because Bos indicus calves experience greater neonatal mortality than Bos taurus calves if cold stressed, the effect of breed type on metabolism and morphology of perirenal brown adipose tissue (BAT) from newborn Brahman and Angus calves was examined. Lipid metabolism and morphology were measured in sternum and tailhead subcutaneous (s.c.)white adipose tissue (WAT). At parturition, Brahman cows were lighter than Fall Angus cows, but heavier than Spring Angus cows (P<.01). Birth weights and perirenal BAT weights were greater in spring-born, but not Fall-born Angus calves than in Brahman calves (P<.01). However, the metabolism and morphology and BAT from both groups of Angus calves was similar. Fall-born Angus BAT contained 63% more (P<.03) adipocytes/100 mg tissue and contained a greater proportion (P<.05) of adipocytes with mean diameters of 40-50 micrometers,and fewer adipocytes with diameters 60 micrometers or greater, than Brahman BAT. Brahman BAT contained two-to-three times as many beta-receptors as Angus BAT (P<.02), although the Kd was not different between breed types. Mitochondria in Brahman BAT were primarily spherical, whereas Angus BAT mitochondria were more elongated, and mitochondrial cross-sectional area tended (P=.08) to be greater in Brahman BAT than in Angus BAT. There was no difference (P=.26) in the mitochondrial uncoupling protein mRNA:28S rRNA ratio between Brahman and Angus BAT. On a per cell basis, palmitate incorporation into neutral lipids was higher (P<.03) in Brahman BAT than in Angus BAT. We conclude that differences UCP gene expression cannot cause the greater peak thermogenesis of Angus calves; however, differences in lipid metabolism and mitochondrial morphology may be responsible for this phenomenon.