M. W. Tess

Evaluation of mating systems involving five breeds for integrated beef production systems: I. Cow-calf segment.

Deterministic computer models were used to simulate the cow-calf segment of an integrated production system. Angus, Charolais, Hereford, Limousin, and Simmental breeds were included in three mating systems: pure-breeding (PB) or two- (2R) or three-breed (3R) rotational crossbreeding. Breed data were taken from the literature. Herds were evaluated over the production year. Sires represented breed averages and were available from sources outside their herds, and 100 replacement heifers were saved annually. Females in 3R had the highest average energy requirements (8,144 Mcal of ME.cow-1.yr-1) and production costs (

A model of growth and growth composition for beef bulls of different breeds

322.31.cow-1.yr-1), and PB females had the lowest average requirements (7,748 Mcal of ME.cow-1.yr-1) and costs (

Genetic Parameters for Carcass Traits in Hereford Bulls

313.2.cow-1.yr-1). Purebred systems were the least biologically and economically efficient (64.9 Mcal of ME/kg of steer equivalent,

Cytoplasmic genetic effects on preweaning growth and milk yield in Hereford cattle.

2.35/kg of steer equivalent), respectively, and 3R systems were the most efficient (56.6 Mcal of ME/kg of steer equivalent,

Sire × Environment Interactions for Growth Traits of Hereford Cattle

1.95/kg of steer equivalent). On average, 3R systems were more efficient biologically and economically than 2R systems. However, some 2R systems were as efficient as some 3R systems. Crossbred combinations containing Angus and(or) Hereford ranked more biologically and economically efficient than other breed combinations. Conversely, British purebreds ranked more biologically efficient, whereas Continental purebreds ranked more economically efficient.

Lean and Fat Growth Patterns of Serially Slaughtered Beef Bulls Fed Different Energy Levels

Abstract A biological model was constructed to simulate growth and growth composition of beef bulls representative of different breed types (small, medium and large) as affected by feeding level. Main starting points were breed-specific prediction of average daily lean gain and general concepts about protein and fat deposition. Growth, fat and protein deposition in the carcass and empty body were simulated on a daily basis. The model was validated on a separate data set. On a restricted feeding regimen differences between small and large beef breeds were small, but at a high feeding level large breeds grew faster and deposited less fat. Breed differences were sensitive to assumed maintenance requirements. The model provides a method to evaluate various measures of biological efficiency for alternative combinations of breeds and feeding levels.