C. J. Brown

Effect of exercise and pre-slaughter stress on pork muscle characteristics

The effects of exercise, stress and chill temperature on pork muscle characteristics were studied in a 3 × 2 × 2 factorial experiment in which treatments were assigned to blocks made up of six pigs of the same sex from the same litter. Pigs were fed a corn-soybean meal diet with the two littermate pigs on each treatment fed together. Treatments were (1) a control group receiving no exercise and fed in an 8 m(2) pen; (2) a treatment group fed in an 8 m(2) pen and driven 1·6 km/day for 100 days prior to slaughter; and (3) a treatment group fed in pens with 40 m(2) floor space with feeders placed 5 m from their waterers. When the animals averaged approximately 105 kg in weight, one animal from each pair treated alike was subjected to standardized stress. After slaughter, one side was chilled at 2-3°C and the other at 13-15°C for 24 h. Both sides were then chilled at 2-3°C for an additional 24 h. Exercise did not affect average daily gain (ADG), feed efficiency, yield of total wholesale cuts, muscle pH, protein solubility, fiber diameter and sarcomere length of the Longissimus dorsi (LD) and Quadriceps femoris (QF) muscles or the tenderness of the QF muscle. Exercise decreased backfat thickness and the subjective tenderness of the LD muscle. The effects of stress on the characteristics evaluated were consistent with those that have been previously reported. Chilling temperature and interactions involving chilling temperature did not affect any of the characteristics studied. No exercise × stress interactions were observed. Protein solubility values indicated that pale, soft exudative (PSE) muscle was not a factor in any of the treatments. It was concluded that exercise will produce leaner carcasses but less tender muscle and that exercise will not counteract the effects of pre-slaughter stress.

Factors influencing pregnancy rate and calving date in four breeds of beef cows on an Ozark mountain range

Abstract Observations from 4928 matings made over 17 years were used to evaluate the influence of year, exposure class, cow weight, average daily gain (ADG) before and during the breeding season on pregnancy rate (PR) and calving date (CD) in four breeds of beef cows maintained on an Ozark mountain range. Pregnancy rate was the percentage of cows exposed to natural mating that were checked pregnant in the fall. Calving date was the number of days from a base date of 1 January. Pregnancy rate and CD were analyzed separately for each breed by least-squares analysis of variance. A model including the above factors accounted for 10 to 12% of the variation in PR and 3 to 23% of the variation in CD. Variation among years significantly affected PR and CD. Cows being bred for their first lactation had the lowest PR and the latest CD. Mature cows had the highest PR and the earliest CD. Partial regression coefficients of PR and CD on cow weight ranged from 2.9% and −3.2 days to 7.4% and 2.3 days/100 kg. Partial regression coefficients of PR and CD on ADG prior to the breeding season ranged from 3.4% and −14.5 days to 24.9% and −2.8 days/kg. Partial regression coefficients for PR and CD on ADG during the breeding season ranged from 10.4% and −18.2 days to 41.6% and −6.1 days/kg. A second analysis was performed on the adjusted data in which cows were nested within sires and offspring were nested within cows. The major source of variance for the two traits was among offspring within dams, which accounted for 78.7 to near 100% of the variation in PR and 50.6 to 84.6% of the variation in CD.

Inbreeding and Relationship to Performance in a Closed Herd of Small-Framed Angus Cattle1

The objective of this study was to estimate level of inbreeding and relate it to performance in a closed herd of small Angus cattle. This herd of Angus cattle was created in 1973 when the shift from small-framed, compact cattle to the largeframed, more upstanding type of cattle was advocated by the breed association. From 1974 to 1991, 396 cows were exposed to bulls, resulting in 318 live births. Data included percentage of inbreeding for all animals, calf crop percentage for each year, and birth, weaning, and yearling weights of progeny. Regression procedures were used to examine increase in inbreeding over time. Correlation analyses were used to examine relationships between calf crop percentage and average inbreeding. Relationships of inbreeding to birth and weaning weights of progeny were examined by analysis of variance using a model that included terms for year, sex of calf, year by sex of calf interaction, and percentage of inbreeding of calf and(or) dam as covariates. The model for yearling weights included only terms for year and inbreeding. Average inbreeding of progeny ranged from 3.25% in 1975 to 18.37% in 1990, and average inbreeding of cows exposed for breeding ranged from .89% in 1977 to 11.76% in 1989. Average inbreeding of cows actually calving was comparable, ranging from .89% in 1977 to 10.58% in 1988. A linear relationship (P .10). Inbreeding both of calf and of dam influenced (P<.05) birth and weaning weights but not yearling weight. Inbreeding of calf was more important than inbreeding of the dam for birth weight, and inbreeding of the dam had a greater effect on weaning weight than inbreeding of the calf.