Most quantitative trait locus (QTL) detection studies in pigs have been done in experimental F2 populations, by crossing 2 genetically different breeds, and some strong candidate genes have been detected. However, segregation of QTLs must be confirmed within purebred populations directly, because the possibility exists that no genetic variation in purebred populations would be observed. In Japan, many local public animal experiment stations have performed selection experiments in closed-line breeding for several generations using estimated breeding value. Segregation of QTLs affecting selection traits might have occurred in these populations. Therefore, we carried out a whole genome QTL analysis for selection and correlation traits such as meat production, meat quality, and carcass traits in a Duroc purebred population. This population had been selected for 7 generations on the basis of breeding values for a daily gain, loin eye muscle area, backfat thickness, and intramuscular fat content. In this study, many significant QTLs for selection and correlation traits were detected in this population. In particular, we found highly significant QTLs for fat accumulation traits and fatty acid composition, for which fine mapping analysis were performed. The SNPs of the leptin receptor (LEPR) gene and the stearoyl-CoA (delta-9-desaturase) (SCD) gene, which are located on significant QTLs, have strong effects on fat accumulation traits and fatty acid composition, respectively. These results imply that QTL analysis by using a closed pig line breeding population is effective for detecting QTLs within a purebred population. Moreover, this study provides useful information for successful implementation of marker-assisted selection in a purebred population.

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Recently, we reported that the addition of 10% (v/v) seminal plasma to thawing solution suppressed sperm activation (cryo-capacitation) and increased implantation rates for embryos following artificial insemination (AI). In order to clarify reproductive performance such as conception rate and litter size, in this study we performed a large-scale AI trial using frozen-spermatozoa thawed by seminal plasma-containing thawing solution at the Oita Prefectural Agriculture, Forestry and Fisheries Research Center. Sows of natural estrus were cervical artificially inseminated three times per estrus (5×10⁹/50mL per injection). When frozen-thawed spermatozoa treated with seminal plasma were injected into the uterus, high reproductive performance was observed. These results were comparable to that of liquid semen (conception rate ; 80.2 vs. 73.9% (liquid semen), litter size ; 10.1 vs. 10.3, number of live born ; 9.2 vs. 9.5). From the basic AI study, examining whether AI by seminal plasma-containing thawing solution is efficient at a commercial level, we carried out AI using frozen-thawed spermatozoa at a pig production farm. The conception rate, litter size and the number of live born after AI with seminal plasma were found to be at a standard level similar to that of liquid semen (conception rate ; 82.4 vs. 84.2% (liquid semen), litter size ; 11.8 vs. 11.0, number of live born ; 11.1 vs. 10.4). From these results, we concluded that the 10% (v/v) seminal plasma-containing thawing solution is a beneficial tool for AI using frozen-thawed boar spermatozoa.

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The objectives of this research were to improve the preservative quality of concentrated rice washing water (CRWW) and evaluate its feed characteristics. The effect of formic acid or propionic acid addition on the preservation of CRWW was examined. Formic acid (0.3%, 0.6% and 1.5%, by weight) or propionic acid (0.5%, 1.5% and 2.7%, by weight) was added to CRWW. The samples were stored at 25°C for 7 days and standard plate counts for bacteria, yeast, and coliform were carried out. The standard plate bacteria count number in 0.6% or more formic acid additions was less than that in counts made immediately after collection. The number of yeast in all levels of either organic acid was less than that in counts made immediately after collection. Coliform was not detected in all levels of either organic acid. From the results, 0.6% formic acid addition was the best choice to preserve the quality of CRWW. Next, twenty five samples of CRWW were collected from five rice milling factories and chemical compositions were determined. Moisture varied from 91.6% to 94.6%, and chemical compositions also varied. From this, variations in moisture and chemical compositions within factories must be noted when using CRWW as feed ingredient. Finally, a digestion study was carried out to investigate the digestibility of CRWW. Six crossbred barrows (Landrace×Large White×Duroc) were used and assigned to a crossover model. Feed given to the animals were 22.2% basal diet and 77.7% water for the control group and 12.5% basal diet and 87.5% CRWW for the experimental group. The digestibility of nutrients of CRWW was 85.7% for crude protein, 85.9% for crude fat, 95.4% for NFE, 35.0% for crude fiber, 42.8% for ADF, 86.4% for NDF. Total digestible nutrients were 97.2%. These results indicate that CRWW contained enough nutrients as a feed ingredient.

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