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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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J. C. BOURSNELL, D. M. COLE and P. A. BRIGGS

Summary.

Separation of the haemagglutinating protein from other boar seminal plasma proteins has been achieved by using gel-filtration methods. The protein is coagulated by heating at 100° C for 15 min at pH 8·2. It has been confirmed that the haemagglutinating protein thus separated causes the precipitation of Fraction B at pH 8 and low ionic strength. The coagulation by heating of the Fraction A protein of boar seminal plasma has been further studied.

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J. C. BOURSNELL, P. A. BRIGGS and D. M. COLE

Summary.

Further studies, using gel filtration on Sephadex G-200 columns, have confirmed and extended the similarities between the major proteins of boar seminal plasma and the vesicular secretion.

The haemagglutinin in the vesicular secretion has been shown, by red cell agglutination, to occur as a distinct peak masked by the greater protein content of Fraction A.

Completely fresh vesicular secretion kept at 37° C and studied at this temperature within 30 min of slaughter, presents an identical gel filtration pattern.

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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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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.