実際の遺伝的パラメータ，育種目標の変更を仮定した場合での３集団モデルの遺伝的有利性

Breeding efficiency was compared among three population schemes; a single population, a population with two sub-populations and a population with three sub-populations when sets of realistics genetic parameters were assumed, and when breeding objectives were changed in the middle of selection program. A simulation experiment of selection was carried out for 10 generations with 20 replications each by comparing average breeding values and inbreeding coefficients among the three population schemes. Genetic gain of growth trait was the largest, then that of meat quality trait was the second largest, and that of reproductive trait was the smallest. The amount of the genetic gain was dependent on their genetic variance. Among the three population schemes, the single population scheme had similar genetic level with the other two schemes under a selection with same economic weights for the traits, however, the multiple sub-populations scheme had the highest genetic level after crossbreeding between sub-populations when inbreeding depression was assumed. The population shceme with three sub-populations can enjoy full advantage of heterosis when different economic weights were applied to the traits. The change of breeding objective made impact on genetic gain of population scheme when different economic weights were applied to the traits, where the population scheme with three sub-populations had higher genetic than the older population schemes

津高牧場生産和牛の初期成長能力に関する基礎分析

岡山大学農学部附属山陽圏フィールド科学センター津高牧場は約30年前に開設され、現在まで黒毛和種の系統維持や繁殖雌牛の改良を行っている。津高牧場で生産された雌牛は脂肪交雑基準の育種価において岡山県内で最高ランクにされるなど、高い能力を持つ個体が作出されつつある。しかし、これまでに蓄積された体尺および体重の測定記録は相当な数に達するが、未だ育種学的検討が加えられていない。そこで本研究では、津高牧場で測定された黒毛和種集団の体尺測定記録および体重の記録を用いた基礎分析を行い、初期成長能力に関する現状の把握と、この能力に影響を及ぼす要因について明らかにすることを目的とした

Maternal and Direct Genetic Effects on Variance Components Estimation for Economic Traits in Japanese Black Cattle(Animal Production Science Animal Breeding and Genetics)

Variance components due to direct and maternal effects were estimated using data recorded on 740 Japanese Black cattle during the period from 1971-2003. Traits studied were feed intake (FI), feed conversion ratio (FCR), residual feed intake (RFI), average daily gain (ADG), metabolic body weight (MWT) at the mid point of the test period, and body weight (BWT) at the finish of the test (345 days). Data were analyzed using six alternative animal models (direct and including or excluding associated maternal effects). Direct heritability estimates from the model including direct and all the maternal effects were 0.21±0.03 for FI, 0.16±0.05 for FCR, 0.15±0.05 for RFI, 0.18±0.09 for ADG, 0.45±0.03 for MWT and 0.36±0.02 for BWT. Maternal heritability estimates were small and significantly different from zero for only RFI (0.03±0.01), MWT (0.03±0.01) and BWT (0.08±0.04). Antagonistic relationships were observed between direct and maternal genetic effects for FCR and growth traits. The estimates of direct heritability for feed efficiency traits were reduced up to 37% when maternal genetic and maternal environmental effects were considered in the model. The results showed that an antagonistic relationship existed between direct and maternal genetic effect for FCR and growth traits, which indicates that maternal effects should be accounted for these traits in genetic evaluation system

Estimation of Genetic Gain on Growth and Carcass Traits over Direct and Index Selection for Growth and Feed Efficiency of Japanese Black Cattle by computer simulation(Animal Production Science Animal Breeding and Genetics)

A simulation study was performed for performance traits on 740 bulls and carcass traits on 1,774 progeny in Japanese Black cattle to compare the efficiency of direct and index selection. Performance traits included average daily gain (ADG), final body weight (BWF), metabolic body weight (MWT), feed intake (FI), feed conversion ratio (FCR) and residual feed intake (RFI). Progeny traits were carcass weight (CWT), rib eye area (REA), rib thickness (RBT), subcutaneous fat thickness (SFT), marbling score (MSR), meat quality grade (MQG), meat color (MCL) and fat color (FCL). Direct selection for BWF has resulted larger increase in ADG than direct selection for ADG itself. Correlated responses in CWT, REA, RBT and MSR were higher, while in SFT was lower over selection against RFI than those against FCR. Improvement in ADG or BWF resulting positive correlated responses in MSR and SFT, indicating that selection for rapid gain may favor fatter animals. This study provides evidence that selection against RFI might be better than that of FCR for getting better responses in carcass traits. On the other hand, BWF was better than ADG to be included in selection program for either in aggregate index (economic) selection or single trait selection to achieve better correlated responses

Genetic relationships and expected responses for genetic improvement of carcass traits of Berkshire pigs

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