Relationship Between the Estimated Breeding Values for Litter Traits at Birth and Ovarian and Embryonic Traits and Their Additive Genetic Variance in Gilts at 35 Days of Pregnancy

Abstract

We investigated (1) the relationship between the estimated breeding values (EBVs) for litter traits at birth and ovulation rate (OR), average corpora luteal weight, uterine length and embryonic survival and development traits in gilts at 35 days of pregnancy by linear regression, (2) the genetic variance of OR, average corpora lutea (CL) weight, uterine length and embryonic survival and development traits at 35 days of pregnancy, and (3) the genetic correlations between these traits. Landrace (n = 86) and Yorkshire × Landrace (n = 304) gilts were inseminated and slaughtered at 35 days of pregnancy. OR was assessed by dissection of the CL on both ovaries. Individual CL was weighed and the average CL weight calculated. The number of embryos (total and vital) were counted and the vital embryos were individually weighed for calculation of within litter average and standard deviation (SD) of the embryo weight. Length of the uterine implantation site of the vital embryos was measured and the average per gilt calculated. Results suggests that increasing the EBV for total number of piglets born would proportionally increase OR and number of embryos, while decreasing the average CL weight. On the contrary, increasing the EBV for average piglet birth weight and for within litter birth weight standard deviation would increase the average CL weight. There was no relationship between the EBVs for BW and for BWSD and vital embryonic weight at 35 days of pregnancy. OR, average CL weight, number of embryos, average weight and implantation length of the vital embryos had all moderate to high heritabilities, ranging from 0.36 (±0.18) to 0.70 (±0.17). Thus, results indicate that there is ample genetic variation in OR, average CL weight and embryonic development traits. This knowledge could be used to optimize the balance between selection for litter size, average piglets birth weight and within litter birth weight uniformity.

Recent advances in pig reproduction: Focus on impact of genetic selection for female fertility

“…Da Silva et al. () related estimated breeding values (EBVs) for litter size (TopigsNorsvin, Vught, The Netherlands) to ovarian and embryonic characteristics of gilts at day 35 of pregnancy (see Table ). In these gilts, an increase in one unit of EBV for litter size (i.e.…”

“…In the same study, Da Silva et al. () analysed associations between EBVs for piglet birthweight and within‐litter variation in piglet birthweight with ovarian and embryonic characteristics at day 35 of pregnancy. The EBVs appeared not be related with ovulation rate; so selection for a higher piglet birthweight and lower within‐litter variation in piglet birthweight did not affect ovulation rate.…”

“…In another study, Da Silva, Laurenssen, et al., () used ultrasound to assess the average diameter of the 10 largest CL (five per ovary) at day 20–30 of pregnancy, and related that to subsequent piglet birthweight and standard deviation in piglet birthweight (see Figure ). Each extra mm in CL diameter was related to an increase in average piglet birthweight of 36 g and a standard deviation in piglet birthweight of 24 g. Moreover, an increase in EBV for litter size was related to lower CL weights (Da Silva et al., ). Collectively, these data indicate that selection for litter size results in smaller CL during pregnancy, which is related to lower birthweights.…”

Developments of reproductive management and biotechnology in the pig

“…With increasing occurrence of large litters, providing the sow with a good basis to produce enough colostrum is fundamental. Loss of back fat in late gestation and consequently sows arriving at farrowing with inadequate body condition affect colostrum yield (Decaluwé et al, 2013). Therefore, it appears essential that sows improve their body condition gradually during the whole pregnancy, arriving to farrowing in good body condition (backfat of 17 ± 3 mm) to fulfil protein turnover and sufficient colostrum yield (Oliviero et al, 2010;Decaluwé et al, 2013).…”

“…Loss of back fat in late gestation and consequently sows arriving at farrowing with inadequate body condition affect colostrum yield (Decaluwé et al, 2013). Therefore, it appears essential that sows improve their body condition gradually during the whole pregnancy, arriving to farrowing in good body condition (backfat of 17 ± 3 mm) to fulfil protein turnover and sufficient colostrum yield (Oliviero et al, 2010;Decaluwé et al, 2013). During late pregnancy, not only adequate energy intake but also feeding composition seems to be of key importance in supporting the physiology of farrowing and colostrum quality.…”