These include genetics, management of young sows, duration of lactation, distribution of farrowing, illness, stress and fertility of the boar. More Genetics and Reproduction News An average herd parity of 2.5 to 3.0, with more than 45 percent of sows in births of three to six, is optimal for overall productivity. The farrowing distribution that optimizes litter size varies according to genotype, management and type of facility. There is no difference in litter size between sows served by a wild boar or an AI, assuming both are done correctly.
An increase in the percentage of sows returning to estrus on days six and seven after weaning will lower the calving rate and litter size. At least 85 percent of sows should return to estrus on days three, four, and five after weaning. Since the average litter size is 2.5 puppies, this results in a rough general rule that each breeding recommendation will produce a puppy, a heuristic practice for rapid calculations of population growth. For this reason, if a dosage group contains 1 litter with 10 fetuses of malformed rodents or rabbits among 10 normal litters, that occurrence is less of a concern than 10 of those litters, 5 of which contain 2 defective fetuses each.
This type of litter has a negative influence on the average production of BA on the farm, in turn decreasing future yield at weaning. Entlebucher mountain dog breeders observed a decrease in average litter size and an increase in the number of failed matings in recent years. Sexual maturity (number of cycles), at the time of service, has a greater influence on litter size than the age or weight of the first time. Developmental endpoints include litter size, fetal weight, prenatal mortality (as evidenced by the presence of resorptions and stillborn fetuses), sex ratio, and the presence of variations and malformations.
Figure 3 shows the distribution of stillborn piglets (SB) and the percentage of small litters throughout the year. Incidence and distribution of small litters and factors affecting the number of piglets born alive in pig farms. Decreased litter size in domestic cows aged 3 years or older may indicate the development of uterine adenocarcinoma (Figure 41-, the most common neoplasm of female domestic rabbits). Total puppy losses (7.4%) reduced mean litter size at birth from 5.49 ± 2.13 to a mean litter size in the record of 5.08 ± 2.05.Mother's age and parental inbreeding were identified as significant predictors with a negative effect on litter size at birth.
In litters of less than 10 BA, the prolificacy obtained is clearly lower than that shown by litters of 10 or more BA. An increase of 3.7 eggs was achieved from nine generations of selection for ovulation rate, but only 20% of the increase was reflected in an increase in litter size. The final generalized mixed-effect linear models for litter size at birth, litter size in the record, and total puppy losses accounted for 36%, 33%, and 22% of the total variance, respectively.
