Components of prolificacy in hyperprolific Large White sows compared with the Meishan and Large White breeds

Abstract

SummaryWe identified the most prolific sows in French Large White herds and 17 hyperprolific sows (HLW) were bought whose average litter size on 3 farrowings was 16.5 piglets born alive, i.e. a superiority of 5.3 piglets per litter over their contemporaries. In 1 to 3 subsequent pregnancies we compared ovulation and embryonic mortality rates of 10 HLW with those of 10 Large White (LW) and 7 Meishan (MS) sows. The ovulation rate of HLW was significantly higher than that of LW (-!-5.3) and MS ( + 5.7). The ovulation rate of HLW daughters was higher by 2.1 corpora lutea compared to that of LW gilts at the 3rd oestrus after puberty, which occurred at the same age in the 2 genotypes (228 days) ; MS gilts were pubescent significantly earlier (88 days) and had a significantly lower ovulation rate than both Large White groups. The embryonic mortality rate was high in HLW sows (41 p. 100), whereas that of MS sows was low (16 p. 100), compared to that of LW sows (26 p. 100). Regression of embryonic mortality rate on ovulation rate was significantly positive (!-2.5), and embryonic mortality rate remained significantly higher in both Large White groups than in MS sows when corrected for ovulation rate. It is concluded that the improvement of embryonic survival in Large White sows should be a high priority to improve the efficiency of the hyperprolific line and that the Meishan breed which is prolific owing to a low embryonic mortality may be an appropriate experimental model.

A comparison of rate and uniformity of embryo development in Meishan and European white pigs

“…Comparisons in France show no difference between the breeds or a greater number of ovulations in the large white females (Bolet et al, 1986;Bazer et al, 1988). By contrast, in the UK, the Meishan females have usually been observed to have a greater number of ovulations than large white females, both as gilts and sows, in experiments involving several hundred observations Ashworth et al, 1992; the present study).…”

Reproductive performance in relation to uterine and embryonic traits during early gestation in Meishan, Large White and crossbred sows

“…In both France (Bidanel et al, 1989) and the UK (Haley and Lee, 1990) (Bolet et al, 1986;Bazer et al, 1988;Bidanel et al, 1990a), whereas studies on the UK Meishan sample have found signifi¬ cantly higher ovulation rates in both gilts and sows than in Large White females Haley and Lee, 1990;Wilmut et al, 1992). With no advantage to the Meishan in ovulation rate, the prolificacy of the French sample compared with the Large White breed is due to enhanced pre¬ natal survival (Bolet et al, 1986;Bazer et al, 1988).…”

“…With no advantage to the Meishan in ovulation rate, the prolificacy of the French sample compared with the Large White breed is due to enhanced pre¬ natal survival (Bolet et al, 1986;Bazer et al, 1988). Prenatal survival in the Meishan breed in the UK is only slightly greater than in the Large White breed (Haley and Lee, 1990).…”

Oestrus and LH reponses to oestradiol during lactational anoestrus in Chinese Meishan and Large White sows

“…Puberty occurs at about 3 months, thus much earlier than in European pig breeds (6-7 months). Average litter sizes are 30-40% higher than those of contemporary Large White pigs (Bolet et al, 1986; (Bidanel and Legault, 1986;Bazer et al, 1988; On day 20 of lactation, blood samples (3 ml) were taken for 6 h at 15-min intervals for analysis of LH. On day 22 all sows received an im injection of 15 5 og oestradiol benzoate (OB, Progynon B Oleosum, Schering)/kg body weight.…”