The objective of this study was to estimate genetic parameters for growth and body composition traits at 60 d of age and at finish in a population of Berkshire pigs and to evaluate the effectiveness of selection at 60 d of age for meat productivity. A total of 4,548 purebred Berkshire (2,344 males and 2,204 females) pigs born between December 1994 and January 2005 were used in this study. The traits analyzed were BW at 60 d of age; daily BW gain from birth to finish, from weaning to 60 d, from weaning to finish, and from 60 d to finish; age at finish; backfat thickness at 60 d of age and at finish; loin eye area at 60 d of age (LEA60) and at finish; and the number of teats. The heritability estimates for BW at 60 d of age, daily BW gain from weaning to 60 d, backfat thickness at 60 d of age, and LEA60 were 0.22, 0.25, 0.49, and 0.22, respectively. The estimated common environmental effect for BW at 60 d of age, daily BW gain from weaning to 60 d, backfat thickness at 60 d of age, and LEA60 were 0.12, 0.13, 0.18, and 0.21, respectively. Therefore, the common environmental effect should be included in the model to analyze traits at 60 d of age. The positive genetic correlation between LEA60 and loin eye area at finish and the negative genetic correlation between LEA60 and backfat thickness at finish indicated that improvement of the ultrasonic loin eye area at 60 d of age may result in favorable correlated responses to the traits at finish, an increase in loin eye area, and a decrease in backfat thickness. In addition, genetic correlations of backfat thickness at 60 d of age with backfat thickness at finish and loin eye area at finish were found to be favorable, indicating that improvement of ultrasonic backfat thickness at 60 d of age may result in greater correlated responses to the traits at finish: an increase in loin eye area and a decrease in backfat thickness. Therefore, constructing a selection scheme that includes body composition traits at 60 d and traits at finish is practical for gaining a greater selection response.

The objective of this study was to find optimal traits for inclusion in selection criteria by estimating genetic parameters for direct genetic, maternal genetic, and common environmental effects for growth traits before 60 d of age and for the number of teats under an open breeding population, and to evaluate genetic relationships for traits at 60 d of age. Records of 2,344 male and 2,204 female purebred Berkshire pigs were analyzed. For BW at 14 d of age and for weaning weight, the heritabilities of a direct genetic effect were greater than those of a maternal genetic effect. This result is contrary to previous results showing a gradual decrease in the maternal genetic effect and an increase in the direct genetic effect up to weaning. The positive genetic correlations between direct and maternal genetic effects for BW at 14 d of age and weaning weight are clearly contrary to other reports. This phenomenon seems to be caused by creep feeding begun just after the birth of the piglets and maintained throughout the preweaning period in this Berkshire population.

The mRNA expression of sodium-glucose transporter 1 (SGLT1) and fatty acid translocase (CD36) in the gastrointestinal tract of Holstein cattle and Saanen goats before and after weaning was investigated. Before weaning, the expression of both SGLT1 and CD36 was highest in the jejunum, relative to the other parts of the gastrointestinal tract in both species. The expression of SGLT1 and CD36 in the duodenum was second highest in the goats. After weaning, SGLT1 and CD36 expression in the small intestine significantly decreased in both species. The expression of both types of transporters was also detected in the forestomach. From these results, it was concluded that the jejunum is probably the major absorption site for glucose and long-chain fatty acids before weaning, and that the expression of both types of transporters decreases after weaning in cattle and goats.

The Berkshire pig (Sus domestica L.) breed has thin muscle fibers and excellent water-holding capacity. The Berkshire meat makes it widely accepted in the Japanese premium pork market. This study evaluates the accuracy of improving carcass quality with the use of live animal records of Berkshire pigs. Traits analyzed in live animals were: body weight at 60 days of age (W60), age at finish (AGF), daily weight gain from birth to finish (DG), back fat thickness at finish (BFTF), and loin eye area at finish (LEAF), and in carcasses were: carcass weight, loin eye area (LEA), and subcutaneous fat thickness (SCF) at some points, using the records of 4,773 purebred Berkshire pigs. Variance components for the traits were estimated according to the animal model by the Restricted Maximum Likelihood (REML) procedure using the VCE6 program (Neumaier and Groeneveld, 1998). Correlated responses were also calculated. Genetic correlations of back fat thickness (BFT) in live animals with SCF in slaughtered animals were strong, whereas that of LEA between live and slaughtered animals was low. The expected gains by actual selection including W60 and BFTF as selection criterion were superior to other selections. Therefore, selection of live animals at an early stage of growth would be conducive to the production of high quality meat.

We investigated mRNA expression of the glucose transporter, SGLT1, and the long-chain fatty acids translocase, CD36, in the gastrointestinal tract of cattle and goats before and after weaning. SGLT1 and CD36 expression in the jejunum was highest in the gastrointestinal tract before weaning, but it decreased in the small intestine after weaning in both species. From these results, we conclude that the jejunum is likely to be the major absorption site for glucose and long-chain fatty acids before weaning, and the expression of both types of transporters decrease in cattle and goats after weaning.