Non-linear associations were found between litter size and sow survival to the next parity

Application Number of piglets born alive showed positive or no phenotypic associations with sow survival to subsequent parities. This implies that high litter sizes did not have detrimental effects on sow longevity, and both can be improved. Introduction Procedures using commercially available test antigens have been developed to assess the immune competence phenotype of pigs (Harper et al., 2017), Improving sow longevity is necessary for both economic importance and welfare concerns. But, sow longevity is a difficult trait to select for because it can only be measured at the end of a sow's life. Number born alive (NBA) was positively associated with sow longevity and it was suggested as an early indicator trait for sow longevity (Engblom et al., 2016). However, non-linear associations between NBA and sow survival were not explored. This study aimed to investigate whether a larger NBA continuously favoured sow survival to subsequent parities

Genetic Analyses of Sow Longevity Traits, Age at First Farrowing and First-Litter Characteristics

Sow longevity is a vital trait in the pig production sector because of its economic and welfare importance. However, this trait is recorded late in a sow’s life and early selection criteria associated with sow longevity are beneficial for genetic improvement of sow longevity. The aim of this study was to estimate genetic parameters of sow longevity and other sow reproduction traits. Data included 14,284 purebred sows recorded from 1996 to 2016 in 7 commercial herds across Australia. Traits describing sow longevity included the number of maximum parities reached, length of productive lifetime in days, total number of piglets born alive per sow over her lifetime, and stayability from parity 1 to parity 4. Further traits considered were number of piglets born alive (litter size) and average piglet birth weight (both recorded in the first litter), and age at first farrowing. Sow longevity traits were genetically the same traits and had low heritabilities (0.07 to 0.13). Genetic correlations were lowly negative between sow longevity and age at first farrowing (-0.13 to -0.22), and between sow longevity and average piglet birth weight (-0.19 to -0.26). First litter size had positive genetic correlations with sow longevity traits (0.49 to 0.65). This study showed favourable genetic correlations of the traits first litter size and age at first farrowing with sow longevity, suggesting that these two traits could be suitable genetic indicators for sow longevity

Estimation of genetic correlations between primal cut weights and length or area traits in live pigs

Introduction: The wholesale value of pig carcases is influenced by the market price of each primal cut while carcass value to the producer is determined by weight and subcutaneous fatness levels. The middle cut (loin and belly) is economically more valuable than the leg and shoulder cuts (Australian Pork Limited, 2021). Therefore, genetic improvement of total carcase value can occur by increasing the proportion of these highvalued cuts. Weights of retail cuts at different growth stages are phenotypically related to the size and shape of the live animal (Doeschl-Wilson et al., 2005). Further, Sarker et al. (2021) showed live animal measurements are heritable and could be used as genetic predictors of primal cut weights to improve total carcase value via indirect selection of pigs with a higher proportion of high-valued cuts. The present study aimed to estimate genetic correlations between primal cut weights and length and area measurements of live pigs

Variance components estimation for body length and area traits derived from image analysis of live pigs

Introduction: Body conformation of an animal has traditionally been used in the commercial industry as an indicator of carcase value. Pig body conformation can vary in different genotypes because of fat levels, muscularity and stage of maturity Doeschl et al. (2004). Attention to carcase conformation is becoming more widespread as its effects on total meat yield and the weight of individual retail cuts are being recognised. Linear body measurements on live animals offer advantages over ubjective methods of judging carcase conformation and as predictors of primal cut distribution. In order to implement linear or area measurements in genetic evaluations, genetic variation must exist in these traits. This study aimed to estimate variance components and to derive heritabilities for length and area measures of live pigs that were obtained from digital images

Genetic Parameters for Primal Cut Weights in Pigs

A study was conducted to estimate genetic parameters for phenotypes describing primal cuts recorded on 2,077 pigs with pedigrees comprising 5,011 animals over three generations. The four main primal cuts considered were: shoulder, leg, loin and belly. These were analysed as primal weights, or as a percentage of cold carcase weight. Heritabilities ranged from 0.10 (± 0.04) to 0.24 (± 0.06) for primal cut weights and from 0.12 (± 0.05) to 0.24 (± 0.06) for primal cut percentages. The loin primal was the least heritable. The genetic correlations between primal weights and primal percentages for the same primals ranged from 0.97 to 1.00. The genetic correlations among primal cut weights ranged from -0.45 to 0.07 which were similar to those found among the primal cut percentages (-0.63 to 0.06). The genetic correlations between the shoulder and leg primal with the belly primal were negative. The strongest negative genetic correlation was found between the leg and belly primals (-0.45 for weight trait and -0.63 for percentage trait). The leg weight was genetically uncorrelated with loin weight, suggesting that selection for high leg weights would not result in high loin weights. The phenotypic correlation between loin and belly was negative but the genetic correlation was not significant. Genetic correlations between the loin and other primal cut weights were weaker in comparison to the genetic correlations between the belly and other primal cuts. The genetic correlations amongst primal cut weight traits were similar to those found among the primal cut percentages. Incorporating these genetic parameters into a pig breeding program could help to increase the total economic return from pig carcases but would need to be done in association with other traits that impact pig production

Improving carcase value by incorporating primal weights into pig breeding objectives

This study aimed to evaluate the benefits of including primal cut measures of pig carcases in the breeding objective by comparing the efficacy of two different approaches; a detailed approach and a simpler approach. The detailed approach included economic values for the loin and belly primals separately ($1.54 and$2.24/pig respectively), where the simpler approach included an economic value for the combination of these (the 'middle primal' at $1.89/pig). Each approach was evaluated in two different scenarios by adding information on the primal cut(s). Inclusion of primal traits in the breeding objective increased the predicted response to selection by 2.47% and 3.20% for both approaches (I and II) and primals contributed 15% and 12% to the new breeding objectives. The predicted response to selection was greater for the approach that included the middle primal, which was consistent with moderate to high genetic correlations with other traits in breeding objectives

The effect of dam parity on growth, white blood cell count, haemoglobin and immunoglobulin levels of weaner pigs

Dam parity affects the growth rate of finisher pigs and gilt progeny have lower growth rates than progeny from multiparous sows, although the magnitude of this effect varies between herds (Hermesch and Li 2013). Gilt progeny had lower levels of immunoglobulin (Ig) G and IgA at birth (Klobasa et al. 1986). However, differences in IgG and IgA were the reverse between piglets from gilts v. multiparous sows at 2 (IgA) and 3 (IgG) weeks of age, due to higher de-novo synthetisation of Ig in piglets from gilt litters (Klobasa et al. 1986). Similarly, Miller et al. (2013) found no dam-parity effect on multiple immune parameters measured in piglets. This study hypothesised that gilt progeny have reduced growth and similar haematological and immunoglobulin levels in weaner pigs in comparison to progeny from multiparous sows