A study was conducted with 360 gilts and sows from four herds to determine whether fertility was affected when the final of multiple inseminations was performed in late estrus or metestrus (late insemination). Sows and gilts were inseminated at 24-h intervals immediately after the detection of estrus. After receiving a first insemination, females were paired according to parity and estrus statu...

In pig (Sus Scrofa) production, within-batch variation in bw gain of piglets during the nursery period (up to 10 wk of age) can be high and is of high economic importance. Homogeneity of BW within batches of animals is important as it influences the efficiency of use of the grower and finisher facilities, and provides an extra value for the fattening farms. In the current study, factors for a l...

P A R T of the genetic damage induced by X rays may be due to mutations which have harmful effects on viability. Such mutations may vary in the seventy of their effects from lethal to mildly detrimental, and in degree of dominance from completely dominant or overdominant to completely recessive. The difficulties of obtaining precise mutation rate estimates for viability mutations in mammals are...

The polymorphisms of ESR1, FSHB and RBP4 genes were detected by PCR-SSCP, PCR and PCR-RFLP in a Large White and a Landrace herd in Beijing, China and the influence of ESR1, FSHB and RBP4 on litter size traits was analyzed using three models. We found polymorphisms for the three genes in Large White besides for ESR1 and RBP4 genes in Landrace. The results showed that the most genotype effects ar...

Implementation of a Bayesian analysis of a selection experiment is illustrated using litter size [total number of piglets born (TNB)] in Danish Yorkshire pigs. Other traits studied include average litter weight at birth (WTAB) and proportion of piglets born dead (PRBD). Response to selection for TNB was analyzed with a number of models, which differed in their level of hierarchy, in their prior...

Although previous studies have addressed the question of why large brains evolved, we have limited understanding of potential beneficial or detrimental effects of enlarged brain size in the face of current threats. Using novel phylogenetic path analysis, we evaluated how brain size directly and indirectly, via its effects on life history and ecology, influences vulnerability to extinction acros...

A flock of 370 Dorset x Romney ewes with up to 96% autumn lambtng was developed without the aid of hormones. Data from flock and experimental records were used to compare the performance of autumnand spring-born lambs and their dams. Preliminary findings for three seasons show that ewes lambed in autumn had a greater spread of lambing, lower litter size and fewer perinatal lamb deaths. Growth o...

The timing of reproductive development and associated trade-offs in quantity versus quality of offspring produced across the life span are well documented in a wide range of species. The relation of these aspects of maternal life history to monogamy and paternal investment in offspring is not well studied in mammals, due in part to the rarity of the latter. By using five large, captive-bred pop...

The aim of this trial was to investigate the fertility of semen doses that contain sperm from either one, three or six Duroc boars. The trial was conducted on five different farms where sows were randomly assigned to three different groups: Group 1: Sows were inseminated with semen doses containing sperm from one boar. Group 2: Sows were inseminated with semen doses containing sperm from three ...

The litter size of homozygous Booroola Merino ewes results in high perinatal mortality. One subcutaneous implant of crystaline oestradiol in silastic tubing in heterozygous Booroola Merino ewes decreased ovulation rate from 3.18 -r0.15 (n = 39) to 2.03 & 0.14 (n = 35), and decreased litter size (5 8 weeks pregnant) from 2.49 + 0.13 (n = 39) to 1.47 + 0.12 (n = 32), providing a useful management...