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P. H. BROOKS and D. J. A. COLE

Summary.

Groups of gilts of similar age, weight and breeding were allocated at 165 days of age to four treatments. One group of gilts was isolated from boars throughout the experiment. Fewer animals reached puberty during the experiment in this group than in the other groups where boars were introduced. Introduction of a boar to gilts at 165 or 190 days of age resulted in precipitation of oestrous activity. At 165 days, considerable synchrony of oestrus was obtained when there was a rotation of the boars used for testing, but the effect was much less marked when only one boar was used.

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K. J. COOPER, P. H. BROOKS, D. J. A. COLE and N. B. HAYNES

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.

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P. H. BROOKS, K. J. COOPER, G. E. LAMMING and D. J. A. COLE

Summary.

The effect of feed intake during the oestrous period and during previous oestrous cycles on ovulation rate, pituitary weight and pituitary lh potency, has been investigated. Control gilts were fed 1·8 kg food/day from puberty to the third oestrus. Increasing feed intake to 3·6 kg for 1 day, on the day following mating did not significantly affect ovulation rate, pituitary weight or residual lh potency. Increasing feed intake to 3·6 kg on the day ofmating significantly (P<0·05) increased ovulation rate by 1·3±0·15 ova, but did not affect pituitary weight or residual lh potency. Gilts fed 3·6 kg food/day from puberty to the third oestrus had significantly higher ovulation rates than gilts fed 1·8 kg food/day (13·2 versus 11·1 ova; P<0·05), and significantly heavier dried pituitary glands (47·8 versus 38·3 mg; P<0·01). Residual pituitary lh potency was not affected by feed level.

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B. T. Hinton, D. E. Brooks, H. M. Dott and B. P. Setchell

Summary. Spermatozoa were collected from the rat caput epididymidis by micropuncture and their motility assessed after dilution in physiological saline containing carnitine or related compounds. l(+)-Carnitine caused, 2 min after dilution, a transient stimulation of the motility of spermatozoa with low initial motility. No stimulatory effects were seen on spermatozoa which had high initial motility. The d-isomer inhibited the motility of spermatozoa with high initial motility after 2 min and all compounds tested appeared to inhibit, at 20 min after dilution, the motility of spermatozoa with high initial motility. Acetyl-l-carnitine and acetyl-d-carnitine stimulated the motility of spermatozoa with low initial motility. This study suggests that carnitine may be important in the development by spermatozoa of the potential for motility and also to maintain mature spermatozoa in a quiescent state.