Tsutomu Furukawa

Selection for testis size and correlated responses of female reproductive traits in golden hamsters

Golden hamsters were selected for large (high selection direction: H) and small (low selection direction: L) testis size, as measured in live males at age 13 weeks over six generations. The selection response and correlated responses in female reproductive traits were evaluated in terms of the divergence between H and L lines for testis size. In males, the differences in testis size at 13 weeks, testis weight at 19 weeks, and body weight at 13 and 19 weeks were significant at the 1% level from generation 1 onward. The realized heritability of testis size, as estimated from regression of the selection responses on effective selection differentials, was 0.29. This was similar to the heritability estimated by using the multiple-trait animal model restricted maximum likelihood (0.30). In females, significant differences in ovulation rate at the 5% level were detected in generations 5 and 6. Litter size 1 day after birth also diverged between the H and L lines, but the difference was not consistently significant. The realized genetic correlation between testis size and ovulation rate was 0.67.

Comparison of production systems for efficient use of indigenous pig breeds in developing countries.

Conserving pig genetic resources and improving their productivity is important to increase returns over investment in developing countries. The purebred, first-cross, rotational cross and backcross matings representing production systems based on pig breeds indigenous to the country and exotic pig breeds were investigated. The number of pigs in the nucleus and commercial herds necessary to produce a defined quantity of pork was considered. The amount of heterosis between the indigenous and exotic breeds, superiority in meat production, and degree of inferiority in reproductive performance of the exotic breed compared with that of the indigenous breed were investigated. The number of breeding pigs in the whole system was in the following order: pure breeding (PB) > first-cross (F1) > rotational cross (RC) > backcross (BC) systems. The number of breeding pigs in the nucleus herds of the RC and BC systems was smaller than that in the nucleus herds of the PB and F1 systems. The degree of inferiority in reproductive performance of the exotic breed compared with that of the indigenous breed affected the efficiency of the production system.

Effects of correcting missing daily feed intake values on the genetic parameters and estimated breeding values for feeding traits in pigs

Abstract Daily feed intake (DFI) is an important consideration for improving feed efficiency, but measurements using electronic feeder systems contain many missing and incorrect values. Therefore, we evaluated three methods for correcting missing DFI data (quadratic, orthogonal polynomial, and locally weighted (Loess) regression equations) and assessed the effects of these missing values on the genetic parameters and the estimated breeding values (EBV) for feeding traits. DFI records were obtained from 1622 Duroc pigs, comprising 902 individuals without missing DFI and 720 individuals with missing DFI. The Loess equation was the most suitable method for correcting the missing DFI values in 5–50% randomly deleted datasets among the three equations. Both variance components and heritability for the average DFI (ADFI) did not change because of the missing DFI proportion and Loess correction. In terms of rank correlation and information criteria, Loess correction improved the accuracy of EBV for ADFI compared to randomly deleted cases. These findings indicate that the Loess equation is useful for correcting missing DFI values for individual pigs and that the correction of missing DFI values could be effective for the estimation of breeding values and genetic improvement using EBV for feeding traits.

Effects of Change in Amount of Information from Relatives of Candidate on Expected Genetic Gain in Selection for Increased Litter Size in a Closed Swine Herd

家系選抜指数およびBLUP法により,選抜候補の血縁情報量がブタの産子数の改良に与える影響について検討した.産子数の遺伝率は0.1,記録として用いた世代数は選抜候補を第0世代として第4世代までとした.一腹から得られる雌の育成頭数は2～4頭,雄1頭あたりに交配される雌の頭数は5または10頭とした.選抜候補およびその世代の血縁個体の記録は得られないものとした.選抜候補の雌親の血縁個体の記録を用いたときの家系指数による選抜の正確度は,選抜候補の雌親のみの記録によるそれに比べて2倍前後大きくなることが期待された.一腹あたりの育成頭数を一定として雌の育成頭数を変えた場合,選抜候補の雌親のみの記録による選抜では,育種価の期待改良量に大きな差はみられなかった.しかし,選抜候補の血縁個体の記録を用いた選抜では,一腹の雌(雄)の育成頭数によって育種価の期待改良量が異なった.さらに,コンピュータシミュレーションにより発生させた産子数の記録に基づいてBLUP法アニマルモデルにより選抜した場合も,育種価の期待改良量に同様の傾向が認められた.したがって,一腹あたりの育成頭数に制限がある場合,BLUP法アニマルモデル等のように家系情報を用いて選抜する場合には,雌親のみの記録による選抜に比べ,一腹あたりの育成頭数に占める雌の頭数を考慮する必要性が示唆された.

Estimates of Genetic Parameters for Daily Gain and Carcass Traits in Swine

Estimates of heritability, genetic and phenotypic correlations among carcass traits, and between average daily gain and carcass traits are reported. The data came from Miyazaki and Iwate prefectures in Japan, and involved 1, 256 records of Large White barrows born between 1981 and 1986. The traits of interest were average daily gain (ADG), dressing out percentage (DOP), carcass loin length (CLL), loin eye area (LEA), average backfat thickness (ABF) and proportion cut ham (PCH). Genetic parameters were estimated by REML under a multitrait animal model including all the six traits. Line and generation were considered as fixed effects in the model. All traits were adjusted for body weight at slaughter. Estimates of heritability were, 0.32, 0.43, 0.56, 0.65, 0.71 and 0.52 for ADG, DOP, CLL, LEA, ABF and PCH, respectively. Genetic correlations between ADG and carcass traits ranged from -0.34 to 0.06. Genetic correlations among carcass traits ranged from -0.65 to 0.37. It was concluded that selection for improved growth rate and carcass composition should be effective.