The effect of fetal and maternal genotype on embryo survival was studied in two lines of mice from the same base population: line E, selected for high embryo survival, and line CN-, selected for small litter size. Embryos were collected at 3.5 days postcoitus from normally mated donors of both lines and were transferred to the uteri of 2.5-day pseudopregnant recipients from each line. The numbe...

We examined the influence of chromium picolinate fed to gilts during the growing phase from 50 lb through their first farrowing on reproductive and farrowing performance. No differences were detected in first service farrowing rate or total or live born litter size. These data fail to support a positive influence of chromium picolinate fed during development and gestation on reproductive and fa...

Red fox reproduction in north-eastern Spain was studied by analysing the reproductive tracts of 84 females. Mean litter size was estimated to be 3.32 cubs per female, most of the births occurring from mid-March to mid-April.

Economic values for a range of different maternal and carcass sheep performance traits were derived for hill sheep in the United Kingdom. A bioeconomic model that includes estimates of available energy supply and herbage intake for sheep from hill and mountain pastures, together with that from improved grassland, has provided a base from which to define the economic limitations to genetic impro...

Data obtained from the French Kennel Club and the Fichier National Canin were used to estimate the effect of inbreeding on average litter size and survival in seven French breeds of dog. Depending on the breed, litter sizes were 3.5-6.3 puppies and longevities were 7.7-12.2 years. Estimated heritabilities were 6.0-10.9% for litter size and 6.1-10.1% for survival at 2 years of age. Regression co...

The data from developmental toxicity experiments usually are very difficult to analyze statistically because of the lack of independence among littermates and the random nature of the litter size. Only a few of the models that have been proposed in the literature have accounted for both of these features. One of the models proposed by Van Ryzin is invoked to construct a test of trend (dose resp...

An epidemiological survey undertaken in Kenya indicated that 2 previously well-established factors, namely decline in reproductive efficiency with age, and non-seasonality of canine reproductive parameters, hold true for German shepherd (GSD) bitches in Kenya. Data collection forms were distributed to randomly selected GSD breeders and information so obtained was verified using East African Ken...

Data from 2,089 laboratory rats utilized in selection experiments were used to estimate maternal influence on growth from weaning (21 d) to 16 wk of age. Adjustment factors were calculated for the effects of sex, generation, litter size, inbreeding of the dam and inbreeding of the offspring on the body weights. The effect of line of sire was included in the analysis of variance models. Covarian...

1. In cooperative societies with high reproductive skew, selection on females is likely to operate principally through variation in the probability of acquiring dominant status and variation in reproductive success while dominant. Despite this, few studies of cooperative societies have investigated the factors that influence which females become dominant, and/or their reproductive output while ...

Replicated bidirectional selection (with control lines) for nest-building behavior in Mus musculus, where nesting scores consisted of the total weight of cotton pulled through the cage lid during four days of testing, yielded an eight-fold difference between high and low lines after 15 generations of selection. The overall realized heritability pooled across lines and replicates was 0.18 +/- 0....