EFFECT OF BODY COMPOSITION ON NUTRITIONAL AND REPRODUCTIVE EFFICIENCY OF BEEF COWS

PATRICIA LEE HOUGHTON, Purdue University

Abstract

One hundred sixty Charolais-Angus cows were used in an integrated nutrition x reproduction study to (1) determine by comparative slaughter an accurate, practical method for predicting body composition of live cows, (2) identify effects of body composition, energy intake (EI) and lactation on utilization of dietary energy and (3) identify the proper body composition and EI necessary for optimal reproductive efficiency in calf removal (CR) and non-calf removal (NCR) cows. Near infrared reflectance spectroscopy was used to analyze tissue samples collected from comparative slaughter. Regression equations using body condition score (BCS) plus weight most accurately (P < .005) predicted empty body weight (r = .95); backfat, marbling and internal fat (r = .54 to .78); percent lipid for udder, plate and viscera (r = .41 to .73); percent carcass lipid and total empty body lipid (r = .70 to .74). Results suggest BCS plus weight are useful indicators of cow body composition. Low (LE) prepartum (PRP) and postpartum (PP) energy intake (EI) reduced (P < .0001) predicted maintenance energy (PME)/kg metabolic weight (W('.75)). From 30 to 60 d PP, CR reduced (P < .05) PME/kg W('.75) and resulted in a positive (P < .0001) daily change in body energy ((DELTA)BE)/EI. Thin cows (BCS < 3) at parturition and 30 d PP lost less condition and body energy (BE)/IE and required more PME/Mcal of BE during early lactation than fleshy cows (BCS > 3). Results suggest body composition, PRP and PP EI and CR affect utilization of dietary energy in beef cows. Cows receiving a LE PRP diet had lighter calves (P < .05) at birth and 105 d (34.7 vs. 39.0 and 127.9 vs 144.6 kg). Low PRP and high PP EI interacted (P < .05) to reduce the postpartum interval (PPI) by nearly 15 d compared to other EI combinations. High PP EI increased (P < .10) pregnancy rate (PR; 91.2 vs 74.3%) and 105 d calf weight (143.8 vs 128.7 kg). Calf removal reduced the PPI (53.1 vs 77.4 d; P < .0001) and first service conception rate (FSCR; 71.4 vs 91.2; P < .10). Cow BCS at parturition affected PPI ((LESSTHEQ)2('+) = 88.5('a), 3('-) to 3('+) = 60.3('b), (GREATERTHEQ)4('-) = 30.6('c) d; P < .10) and cow BCS at breeding affected FSCR ((LESSTHEQ)3('-) = 98('a), 3(DEGREES) = 80('ab), (GREATERTHEQ)3('+) = 68('b)%; P < .05). Higher PR were obtained (P < .05) in cows moving toward, or maintaining average body condition from parturition to conception than for cows moving away from BCS 3. Results suggest PRP and PP EI, CR and cow BCS affect beef cow reproduction and preweaning calf gain.

Degree

Ph.D.

Subject Area

Livestock

COinS