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THE EFFECT OF FEED LEVEL DURING THE OESTROUS CYCLE ON OVULATION, EMBRYO SURVIVAL AND ANTERIOR PITUITARY LH POTENCY IN THE GILT

Summary.: A series of experiments was conducted to investigate the effect of basal feed level and increased feed intake during oestrus on ovulation rate, early embryo survival, and residual pituitary LH potency in the pig. All the gilts used were fed 1·8 kg food/day from puberty to second heat. Gilts whose food intake was reduced from 1·8 kg to 1·4 kg/day following second heat had more atretic follicles at third heat and had fewer CL and fewer embryos at Day 20 of gestation, than control gilts fed 1·8 kg throughout, but these differences were not significant. Increasing the feed intake of gilts fed only 1·4 kg between second and third heat to 3·6 kg on Day 1 of oestrus only resulted in CL counts intermediate between those of the other two groups. The number of mature and atretic follicles during oestrus was not affected. Anoestrus was more frequent in gilts whose feed intakes were reduced to 1·4 kg/day. Residual pituitary LH potency was higher in gilts receiving only 1·4 kg feed/day than in gilts fed 1·8 kg/day. Increasing feed intake to 3·6 kg on Day 1 of oestrus significantly (P<0·05) reduced residual pituitary LH potency in animals previously fed 1·4 kg/day, but had no significant effect on animals previously fed 1·8 kg/day.