This study was performed to evaluate the effects of a breadcrumb-based diet with low lysine and sex on growth performance and meat quality of Duroc sow × Japanese Wild boar (Sus scrofa leucomystax) crossbreeds (called “Inobuta” in Japan), and to improve the meat quality of the local specialty by “eco-feed.” Ten Inobuta pigs were assigned to two groups according to body weight and sex. The experimental group (BDL group) was fed the breadcrumb-based diet with low lysine (0.42% lysine content) and the other, the control group, was fed a commercial diet (0.60% lysine content). The BDL group had lower feed intake and daily gain than the control group. Carcass weight, dressing ratio and backfat thickness were higher in barrow than in gilt. Intramuscular fat of the longissimus dorsi muscle was higher in the BDL group (3.97%) than in the control group (2.47%) (P<0.01). The BDL group had a slightly lower C16:0 and C18:0 content in the longissimus dorsi muscle but a slightly higher C16:1 and C18:1 than the control group. Gilt had a slightly higher C18:2 than barrow. Shear force and cooking loss of the longissimus dorsi muscle were higher in the BDL group than in the control group, but were not affected by sex. These results indicate that the Duroc sow × Japanese wild boar crossbreeds had 2.5% of intramuscular fat content in the longissimus dorsi muscle, and feeding the breadcrumb-based diet with low lysine increased the intramuscular fat of the longissimus dorsi muscle, although feed intake and daily gain decreased. The barrow had a slightly higher average daily gain, thicker backfat and a slightly higher melting point of backfat than the gilt.

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Relative weights of breeding values of selected traits for estimating aggregate breeding values are widely used for selection to achieve desired genetic changes in the development of pig strains in Japan. The objective of this study was to investigate the relationship between amount of information on relatives of candidates for selection and expected genetic gains when selection achieving desired genetic changes was used to develop pig strains. A boar was mated to 5 gilts and each mating produced one male and two females that were candidates for selection. Two performance traits with heritabilities of all combinations of 0.2 and 0.6, and genetic correlations of −0.5, 0, or 0.5 were assumed. The phenotypic correlation was assumed to be the same as the genetic correlation. The relative desired changes of the traits were assumed to be the genetic standard deviations. Information on phenotypes for selection was on the candidate for selection and its relatives. A very minor increase in expected genetic gain was found if information on phenotypes of relatives whose relationship coefficient was below 1/4 was used for selection. Therefore, information on phenotypes of the selection candidate and its relatives whose relationship coefficient is equal to or more than 1/4 appears to be sufficient for estimating the aggregate breeding value of candidates for selection when a pig population is selected for desired genetic changes.

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