Red Poll

Abstract: For a beef cow to continue in an annual production cycle, she must rebreed within 3 mo after calving. Malnutrition during this period frequently results in failure of the cow to become pregnant. The energetic needs of the cow are increased by lactation, and additional energy is required for growth of the primiparous cow. Determining energy expenditures during the first 40 to 60 d postpartum is critical to developing feed programs that will allow cows to become pregnant with a second calf. Sixty-seven balance trials were conducted on 25 MARC III cows (4-breed composite: (1/4) Hereford, (1/4) Angus, (1/4) Red Poll, and (1/4) Pinzgauer) that were between 3 and 53 d in milk. Cows' BW were 481 +/- 4 kg. Metabolizable energy intake ranged from 14.8 to 28.9 Mcal/d. Milk yields ranged from 4.7 to 13.3 kg/d. Recovered energy (RE) increased linearly with increased ME intake. Forty-seven observations were obtained with cows in negative tissue energy (TE) balance, and 20 observations were obtained with cows in positive TE balance. Estimated zero RE from regression analysis of RE on ME intake was 146 kcal of ME/kg of BW(0.75). Efficiency of conversion of ME to lactation energy (LE) was 72%. The efficiency for conversion of ME to TE and the conversion of TE to LE was 78%. Our findings suggest that, even though their milk production is lower, the overall efficiency of energy retention in young beef cows is similar to that of dairy cows.

Abstract: The effects of heterosis for gestation length, dystocia, calf survival, birth weight, 200-d weight, and ADG from birth to weaning were evaluated in F1, F2, and combined F3 and F4 generations in three composite populations. Breed effects were evaluated for the nine parental breeds (Red Poll, Hereford, Angus, Limousin, Braunvieh, Pinzgauer, Gelbvieh, Simmental, and Charolais) that contributed to the three composite populations. Breed effects were significant for all traits evaluated except survival at birth. The large differences among breeds in additive direct and additive maternal genetic effects offer a great opportunity to use the genetic differences among breeds to achieve and maintain optimum additive genetic (breed) composition to match genetic resources to a wide range of production-marketing ecosystems. There was no heterosis for gestation length. Mean heterosis for dystocia was significant estimated in F1 but not in F2 or in the combined F3 and F4 generations. Mean heterosis was not significant in any generation for survival at birth, to 72 h, and to weaning for the F1 generation; mean heterosis was significant for survival to weaning for the F2 generation and approached significance (P = .06) for the combined F3 and F4 generations. Mean heterosis over all composite populations and heterosis for each composite population were significant in all generations for weight at birth and at 200 d and for ADG from birth to weaning. Retained heterosis was not less than expected from retained heterozygosity in composite populations for the traits evaluated. These results suggest that heterosis for these traits likely is due to dominance effects and, thus, can be attributed to the recovery of accumulated inbreeding depression in the parental breeds.

Abstract: Statistically significant differences were observed in the population density of the horn fly, Haematobia irritans irritans (L.), on different breeds of beef cattle. The European breed Chianina had a population density of horn flies generally less than or equal to 50% than that of the British cattle breeds (Angus, Hereford, Polled Hereford, and Red Poll) and another European breed (Charolais). Generally, no significant difference existed among numbers of horn flies on Hereford, Polled Hereford, and Red Poll cows in 1988 or among Angus, Hereford, Polled Hereford, and Red Poll cows in 1989. Factors other than color appeared to be involved in the selective process between the horn fly and its host. Population densities on two white European breeds (Charolais and Chianina) were significantly different on all weekly intervals except for 4 wk in both 1988 and 1989. No significant difference existed among Charolais and British breeds except during 4 wk in 1988 and 3 wk in 1989. When weaning weights of all calves were adjusted for the effects of age to 205 d, sex of calf, and age of dam, the indirect effect of the horn fly on weaning weight showed a significant linear regression. Each 100 flies per cow caused a reduction of 8.1 kg in calf weaning weight. Cows within each breed with low numbers of horn flies weaned significantly heavier calves than cows with higher numbers of horn flies.

Abstract: Biological efficiency of beef production to weaning and to slaughter was estimated in three groups of cattle reasonably similar in growth and mature size but different in the amount of milk available to the calves (low (L) = Hereford x Angus, medium (M) = Red Poll x Angus and high (H) = Milking Shorthorn x Angus). Efficiency was defined as the ratio of estimated kilograms of calf weight weaned or carcass weight produced by a herd of 100 first-cross cows to estimated metabolizable energy (ME) intake by the cows and preweaning non-milk ME intake by the calves or preweaning non-milk and postweaning ME intake by the calves. Efficiencies were estimated assuming observed and average reproductive rates, and using observed energy requirements for maintenance, as well as the same requirements for maintenance in the M and H groups. With the observed reproductive rates and requirements for maintenance, efficiencies to weaning and to slaughter were 28.1, 27.4 and 27.4 g weaning weight per Mcal ME and 22.0, 20.6 and 20.3 g carcass weight per Mcal ME for the L, M and H groups, respectively. With average requirements for maintenance, efficiencies were 28.2 and 27.5 to weaning and 20.8 and 20.4 to slaughter for the M and H groups, respectively. Under equal reproductive rates and observed maintenance requirements, efficiencies were 28.3, 27.2 and 27.7 to weaning, and 22.1, 20.6 and 20.6 to slaughter for the L, M and H groups, respectively. With average maintenance requirements, efficiencies were 27.5 and 27.4 to weaning and 20.7 and 20.5 to slaughter for the M and H groups, respectively. Across the production output and input assumption scenarios, the L group consistently was the most efficient, especially when evaluated at slaughter of calves.