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ARS Home » Research » Publications at this Location » Publication #47602
Title: PREDICTING EMPTY BODY COMPOSITION AND COMPOSITION OF EMPTY BODY WEIGHT CHANGES IN MATURE CATTLE

Author
item Williams, Charles
item Jenkins, Thomas

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Energy reserves help to maintain physiological equilibrium in reproducing female cattle, under fluctuating levels of feed availability and animal nutrient requirements. Body fat represents a major store of reserve energy in cattle, and decreased body fat at calving is associated with poor reproductive performance. Experimental data suggest that breeds of nonlactating mature cattle have the same empty body composition and the same composition of empty body weight change at the same proportion of a standard reference empty body weight. This standard reference weight was estimated for 18 breeds of female cattle, and observations on body weight can be converted to empty body weight to calculate the proportion of standard reference empty body weight. This information together with the equations in this paper can be used to predict the composition of empty body weight change in reproducing female cattle, and develop feeding strategies to calve cows at a target empty body weight and composition.

Technical Abstract: Data from two experiments that measured empty body chemical composition of 18 breeds or breed crosses of nonlactating, nonpregnant mature cows, were used to estimate a standard reference empty BW (SREBW) for each breed. The SREBW of a breed was defined as the empty BW at skeletal maturity that contained 25% fat. Relationship between empty body fat percentage (EBFP) and empty BW as a fraction of SREBW (U) was, EBFP = -15.7 + 40.7 * U (r** = .77). This relationship was not significantly different among breeds, suggesting that the 18 breeds of mature cows would all have the same empty body composition at the same proportion of SREBW. An evaluation with chemical composition data of five breeds of mature nonlactating cows showed no significant difference in the relationship between EBFP and U. Data from five experiments showed that cows that lose EBW in early lactation had a leaner empty body composition compared with nonlactating cows at the same value of U. Equations were formulated to adjust predictions of body composition changes in lactating cows. These equations can be incorporated into existing herd models to predict composition of empty body weight changes in reproducing female cattle, and formulate feeding strategies to enhance reproduction.