Explanation for embryo death in gilts fed a high energy intake.

Abstract

In four experiments 190 crossbred gilts were assigned to basal feeding levels of either 1.81 kg. (L) or 2.72 kg. (H) per day, 6 days each week, except that one-half of the gilts on each of the basal feeding levels were fed ad libitum (F) for approximately 14 days prior to breeding. The LF gilts had significantly (P<.05) higher ovulation rates than the L gilts in three of the four experiments. The LF gilts also had a significantly (P<.01) higher embryonic death rate as compared to the L gilts in two of four experiments. There was a significant (P<.05) increase in ovulation rate in the HF gilts in two experiments. Complete reciprocal embryo transfers between L and LF or H and HF gilts resulted in a highly significant (P<.01) reduction in fetal survival in the LF recipient gilts, with a similar but nonsignificant trend in the HF recipient gilts. It was concluded that embryos from flushed and nonflushed gilts are equally viable and that the reduced rate of embryonic survival in gilts on high levels of energy intake prior to breeding is due to some uterine factor. The average number of potential embryos was increased to 17.5, 19.7, 21.5 and 22.5 by adding embryos to uteri of the L, LF, H and HF gilts, respectively. Average litter size was not significantly different among treatments or from that of the control gilts. Survival rates of the transferred and nontransferred embryos of the recipient gilts were equal (44% vs. 46%). It was concluded that the uterus can effectively limit litter size and that this limit, called uterine capacity, is not greater than that now reflected in the normal litter size of gilts.