Analysis of the breeding records of a herd of pigs

Abstract

1. A survey and. statistical analysis of the records of litters born in the N.I.R.D. herd of Large White pigs over a period of 16 years are presented.2. The mean length of gestation was 114 days for both gilts and sows.3. The mean numbers of pigs born alive and born dead per litter from gilts, 10·0 and 0·2 respectively, were both significantly smaller than the corresponding figures for sows, 11·8 and O·8. No seasonal differences were found.4. The mean total losses of pigs from birth to weaning at 8 weeks were 29·5% of pigs born alive. The losses in litters from gilts, 23·0%, were significantly smaller than in litters from sows, 31·0%. The losses during the winter months both for gilts, 32·5%, and for sows, 35·9%, were significantly higher than during the summer months, 19·4% and 26·7% for gilts and sows respectively.5. Over 50% of the total losses were due to crushing by the dam, 74·1% of the losses from this cause occurring during the first 48 hr. after birth.6. The mean number of pigs weaned per litter was 8·0. The difference between the number weaned per litter from gilts, 7·7, and per litter from number of pigs was weaned per litter from sows during the summer months, 8·7, than during the winter months, 7·4.7. There was no significant difference between the number of male and of female pigs weaned.8. The mean weight at weaning was 29·9 lb., male pigs, 30·3 lb., being significantly heavier than females, 29·51b. Pigs in litters from gilts, 27·81b., were significantly lighter at weaning than those from sows, 30·0 lb., and for both gilts and sows, pigs reared during the summer months, 29·7 and 31·8 lb. respectively, were significantly heavier than those reared during the winter months, 25·9 and 28·2 lb. respectively.

A Study of the Reproductive Performance of a Purebred Hereford Herd1

“…Berliner (1942) noted seasonal variation in the reproductive performance of mares and jennets in Mississippi. Braude et al (1954) found no seasonal influence on the fertility of swine.…”

“…The relation was similar for jennets except that they had longer gestations. Braude (1954) reported no seasonal effects on the number of pigs farrowed when the two seasons--November to April and May to October == were considered. As the gilts were slaughtered, Wiggins~ al, (1950) observed the reproductive organs of gilts farrowed in different seasons,…”

“…From the records of 487 litters of swine Braude (1954) Bishop~ al. (1954) made a similar observation.…”

Preweaning Weights in Lines of Pigs Selected for Rate of Gain and Thickness of Backfat

“…This was another expression of the earlier mentioned difference between effect of parity on litter weights and average pig weights when eliminating versus ignoring litter size. Many authors have found the lowest weights in the first parity (Lush & Molln, 1942;Korkman, 1947;Braude et al, 1954;Lynch, 1965;Eikje, 1970;Hetzer & Miller, 1972), but for higher parties the picture was more complex. Lush & Molln (1942) found the highest litter weights at weaning for 2 year old sows both in their own study and in the five studies they reported.…”

“…This was in agreement with Lynch (1965) who found the highest 21-day weights for parities 2 and 3, and Eikje (1970) who found the highest values for the third parity, both for litter weights and average pig weights at 21 days. Korkrnan (1947) found litter size to be decisive for the best parity between the second and sixth, while Braude et al (1954) did not find any effect of later parities on average weaning weight. Both Omtvedt et al (1965) and Hetzer & Miller (1972) found an effect of age of the gilts on average birth weights.…”