6KING R H, WILLIAMS I H. The effect of nutrition on the reproductive performance of first -litter sows [ J]. Anita Prod, 1984 (38) : 241 -247.
7D. Marois, J. R. Brisbane, J.-P. Laforest. Accounting for lactation length and weaning-to-conception interval in genetic evaluations for litter size in swine. J. Anim. Sci., 2000,78:1 796-1 810
8Variey M A,Coie D J.Studies in sow reproduction: 5. The effect of lactation length of the sow on the subsequent embryonic development. Anita Prod,1976,22(1):79-85
9Hays V W, J. L. Krug, G.L. Cromwell, et al, Effect of lactation length and dietary antibiotics on reproductive performance of sows. J. Anim. Sci., 1978,46:884-891
10Beistra BA, Diekman MA, Richert BT. Effects of lactation length and an exogenous progesterone and estradiol-17beta regimen during embryo attachment on endogenous steroid concentrations and embryo survival in sows. Theriogenology, 2002,57(8):2 063-2 081
