The search for ways to select for improved beef cow efficiency has become the holy grail of the beef cattle seedstock industry. Increases in beef production have often been possible due to enhancements in the reproduction indexes (e.g. calving frequency, age at first calving, calving interval), nutrition concepts (e.g. strategic supplementation, type of forage as well as quantity and quality), ...

Twoand 3-year-old beef bulls were exposed to 25 or 40 beef cows on pasture during a 90-day breeding period. Reproductive performance of bulls by age of bull and size of cow group was evaluated in terms of percentage calf crop. Results indicated that reproductive performance of 2-year-old bulls was higher, but not significantly different (P>.05), than that of 3-year-old bulls. The percentage cal...

In the Netherlands a fertility index is introducing which describes the fertility of daughters of a bull. The index is based on two breeding values which are estimated for all bulls; non return after 56 days (NR56) and interval between calving and first insemination (ICI). These two traits are combined in an index: the calving interval index or CI-index. This index was developed after comparing...

Bovine viral diarrhea virus (BVDV) is a common pathogen of cattle herds that causes economic losses due to reproductive disorders in breeding cattle and increased morbidity and mortality amongst infected calves. Our objective was to evaluate the impact of BVDV spread on the productivity of a beef cow-calf herd using a stochastic model in discrete time that accounted for (1) the difference in tr...

quality semen can be produced ulls of any age, but recovery in 3-6 months was found in nearly half of such bulls that could be retested. Semen samples were obtained from 460 bulls 15-24 months of age, from 53 bulls 3 6 years of age, and from 12 bulls 2-6 years of age, used for breeding. The test on the first two groups is recorded in the table in the first and second columns. Of the 460 young b...

The capability of bulls to distribute their genetics is dependant upon their fertility, whether they are used for natural breeding or A.I. In turn, herd reproductive performance has been shown to have a greater impact on economic returns than either growth rate or product quality (Wiltbank 1994). Here, chute-side math indicates it takes approximately 5 generations (15 years) using bulls of 10% ...

Maintaining the health of animals in a beef breeding herd is critical to insure optimum herd productivity since the major contributor to overall herd performance is the reproductive rate. Because of this level of importance, it is essential to carefully monitor all aspects of herd reproduction on a production year basis in order to monitor each year’s production and make good management decisio...

I N connection with the record of performance work carried out at the U.S.D.A. Research Center, Beltsville, Maryland, various body measurements of each steer were taken at a live weight of approximately 900 pounds. This work was undertaken to determine whether any association existed between body measurements and the slaughter grade, carcass grade, and dressing percentage of the steers. If such...

Breeding objectives and their derivation are considered in relation to numerous changes occurring in genetics, in societal attitudes, and in the environment. We outline the experience in Australia with breeding objectives for beef cattle, sheep and pigs and discuss ramifications of the new developments for future objectives. Areas are suggested where more attention will be needed, and where the...

A field study was conducted in a village in northern Vietnam to investigate how host distribution influences Japanese encephalitis (JE) vector abundance. Indoor and outdoor collections were conducted from 50 compounds. We collected three JE vector species--Culex tritaeniorhynchus and Culex vishnui that comprised the Culex vishnui group, and Culex gelidus. Spatial autocorrelation was not observe...