Evaluation of life-cycle herd efficiency in cow-calf systems of beef production.

A deterministic beef efficiency model (BEM) was used to evaluate life-cycle herd efficiency (LCHE) in cow-calf beef production systems using four breed groups of beef cattle. The breed groups were Beef Synthetic #1 (SY1), Beef Synthetic #2 (SY2), Dairy Synthetic (DS), and purebred Hereford (HE). The LCHE was defined over the lifetime of the herd as the ratio of total output (lean meat equivalent) to total input (feed equivalent).

Longevity and lifetime productivity of cows in a purebred Hereford and two multibreed synthetic groups under range conditions.

Records on 983 cows born during a period of 10 yr (1966 to 1975) were used to estimate longevity and lifetime productivity of cows raised under range conditions. The cows were from a purebred Hereford and two multibreed synthetic groups, one composed of beef breeds (Beef Synthetic #1) and the other composed of two-thirds dairy breeds and one-third beef breeds (Dairy Synthetic). The cows were raised under a stringent culling system in which all heifers were exposed to bulls as yearlings and were expected to wean a calf each year thereafter or they were culled.

Factors influencing growth performance of beef bulls in a test station.

Performance records of 2,034 beef bulls tested at the Ellerslie Test Station, Alberta, Canada from 1974 to 1987 were analyzed to identify important factors that affect growth of bulls in a test station and to estimate the contribution of herd of origin to phenotypic variances of growth traits. Compared with herd of origin, age of dam, start of test age, and weight of bull were not of practical importance. Herd of origin accounted for a large fraction of phenotypic variance of weight, decreasing from 52 to 35% and from 37 to 30% from start to end of test in groups of small and large breeds, respectively.

A comparison of natural service fertility of yearling and two-year-old bulls on pasture.

The natural service fertility of yearling bulls on pasture was compared with that of 2-year-old bulls in a study (2 experiments) which involved a total of 748 composite breed cows over 3 breeding seasons. Other factors such as age of the cows, breed, year effects, and the sequence in which bulls of a particular age were assigned to cows were also evaluated. Pregnancy and calving rates and calving date were used as criteria for assessing fertility.