The pelvis is a sexually dimorphic structure and although the causes of that dimorphism have long been studied, relatively little is known regarding the effects of partuitive events on the magnitude of that dimorphism. Here, we use a sample of Mus musculus domesticus to contrast dimorphism in body length and os coxae size and shape between males and parous and nulliparous females. We also test ...

Phenotypic plasticity and microevolution are the two primary means by which organisms respond adaptively to local conditions. While these mechanisms are not mutually exclusive, their relative magnitudes will influence both the rate of, and ability to sustain, phenotypic responses to climate change. We review accounts of recent phenotypic changes in wild mammal populations with the purpose of cr...

Iteroparous organisms maximize their overall fitness by optimizing their reproductive effort over multiple reproductive events. Hence, changes in reproductive effort are expected to have both short- and long-term consequences on parents and their offspring. In laboratory rodents, manipulation of reproductive efforts during lactation has however revealed few short-term reproductive adjustments, ...

Improvement of farrowing rate (FR) and litter size (LS) of sows that are AI with frozen-thawed (FT) semen can hardly be reached without identification of the factors behind the high variability seen among trials. Three experiments using weaned (4-d wean-to-estrus interval) multiparous (parity 2 to 7) sows were conducted to evaluate the effect of period of the year on FR and LS of FT-inseminated...

The aim of this study was to address the question of whether differences in farrowing rate and litter size after the use of different ejaculates could be predicted using the standard semen parameters under commercial conditions. In this study, a total of 1818 sows were used to evaluate the fertility predictive value of different sperm parameters. Logistic regression analysis (univariate and mul...

The influence of melatonin receptor 1A gene on litter size was studied in 150 ewes from Zel (n=100) and Naeini (n=50) sheep breeds. Two restriction fragment length polymorphism (RFLP) analyses were done to determine all genotypes occurring by variations at MnlI and RsaI restriction sites. The M and C were the most frequent alleles in both of these breeds. The MM genotype was predominant in Zel ...

The objective was to estimate the incidence of and to determine the effect of some risk factors on the decrease of litter size at parity 2 of sows in three commercial farms in Yucatan, Mexico. Data on 8,592 farrowing records of 4,296 sows were analyzed using a binomial logistic regression procedure. The model included the fixed effect of farm (1, 2, and 3), year of farrowing (2003-2011), season...

Fifteen generations of selection were conducted to study responses for litter size at birth (LSB), weight at weaning of standardized litter (LWW), and individual body weight at 8 wk of age (BW8) using golden hamsters as an experimental model for pigs. The experiment involved three lines: selection on an aggregate breeding value of LSB, LWW, and BW8 (line W); selection on an aggregate breeding v...

A clinical study was conducted to document the effect of administration of hCG at the time of mating on the conception and litter size in Labrador female dogs. A total of 50 Labrador female dogs were used for this study and were assigned to five different groups, each group contained 10 animals. The conception rate, litter size and gestational period of control group were 60 per cent, 5.83 ± 0....