張秀鑾 賴永裕 吳明哲
應用行政院農業委員會畜產試驗所育種場1981至1997年間出生之1977頭純種母豬(藍瑞斯891頭、約克夏500頭與杜洛克種586頭）於1982至1998年間分娩的6593胎產仔性能(包括分娩總仔數LS、分娩活仔數LSA與三週齡窩仔數LS3)，進行遺傳趨勢與遺傳參數估計。採用多性狀線性混合模式配合限制最大似然法(REML)估算各項變方與共變方成份，模式包括品種、分娩產次、母豬出生與分娩季節(涼與熱季)等固定效應，而母豬之累加性遺傳效應、同窩出生共同效應與殘差等為逢機效應。LS、LSA與LS3遺傳變異率估值為0.091、0.099與0.095，同窩出生之共同環境效應估值為0.047、0.033與0.024。性狀間遺傳相關估值均在0.85以上(0.863 ~ 0.938)。LS、LSA與LS3具顯著的品種與分娩產次效應(P＜0.001)，且母豬的出生與分娩季節對其產仔性能LSA與LS3均有顯著的影響；出生或分娩於涼季的母豬顯著地有較大的出生活仔數與三週齡窩仔數(P＜0.05與P＜0.001)。表型與遺傳趨勢均呈現下降的趨勢(-0.083 ~ -0.031與-0.132 ~ -0.049頭/窩/年)，表型方面以約克夏種(-0.132頭/窩/年)之年下降幅度為最大；遺傳趨勢部份，除LS3外，亦以約克夏種(-0.083頭/窩年)之年下滑幅度為最大。同時，各性狀遺傳趨勢佔其表型趨勢之百分率，在藍瑞斯、約克夏與杜洛克種分別為59.6 ~ 75.5%、46.4 ~ 62.9%與59.7 ~ 85.7%。
EVALUATION OF GENETIC TRENDS AND PARAMETERS FOR
PERFORMANCES IN GROWTH SELECTION-BASED HERD AFTER 16 YEARS
H. L. Chang, Y. Y. Lai and M. C. Wu
Taiwan Livestock Research Institute, Council of Agriculture
Record of littering performance data on 891 Landrace, 500 Yorkshire and 586 Duroc pigs in Taiwan Livestock Research Institute between 1982 and 1998 were used. A total of 6593 litters from 1977 sows born between 1981 and 1997 were analyzed. Traits were litter size at birth (LS) and born alive (LSA) as well as litter size at 3 weeks of age (LS3). Mixed linear model via REML for multiple trait analysis was employed for estimation of variance-covariance components. Model for individual genetic evaluations included breed, parity, birth and farrowing seasons of sows as fixed effects, and additive genetic effects, common litter effects and error as random effects. Estimates of heritability from additive genetic variances for LS, LSA and LS3 were 0.091, 0.099 and 0.095. The corresponding estimates for common litter effect were 0.047, 0.033 and 0.024, respectively. Genetic correlation estimates were larger than 0.85 among traits considered (0.863 ~ 0.938). LS, LSA and LS3 differed among breeds and parities (P＜0.001). Significant seasonal effects were also found in LSA and LS3. Sows born or farrowing in cool season produced larger LSA and LS3 than those in hot season (P＜0.05 and P＜0.001, respectively). However, both estimates of phenotypic and genetic trends for traits considered were negative (-0.083 ~ -0.031 and -0.132 ~ -0.049 piglets/litter/year). Yorkhsire sows showed the largest yearly phenotypic decrease (-0.132 piglets/litter/year). Similar trend was also observed in genetic evaluation among sow breeds except LS3. Furthermore, genetic trends accounted for 59.6 ~ 75.5%, 46.4 ~ 62.9% and 59.7 ~ 85.7% of phenotypic trends in Landrace, Yorkshire and Duroc breeds, respectively.
Key Words: Swine breeding stock, Genetic trend, Genetic parameter, Littering performance.