Genetic parameters and predicted selection results for maternal traits related to lactation efficiency in sows

Abstract

The increased productivity of sows increases the risk of a more pronounced negative energy balance during lactation. One possibility to prevent this is to increase the lactation efficiency (LE) genetically and thereby increase milk output for a given feed intake and mobilization of body tissue. The benefits of selection for LE depend on its heritability and the relationships with other traits of interest. The objectives of this study were to estimate genetic parameters for LE, its underlying traits, and to predict the consequences of current selection strategies in dam lines. Data from 4 farms were available to estimate genetic parameters. Heritabilities were estimated by using a univariate repeatability model, and genetic correlations were estimated bivariately. Selection index theory was used to predict the genetic progress by 3 alternative breeding programs: 1) a breeding program that aimed at balanced progress in the total number of piglets born, piglet mortality, and percent prolonged interval from weaning to estrus; 2) extension of this breeding goal with LE; and 3) a breeding goal that included only one selection criterion, litter weight gain, to demonstrate the effect of indirect selection for milk production. The heritability for LE was low (0.12). Body fat mass (0.52) and BW (0.45) of sows at the beginning of lactation showed the greatest heritabilities. Protein mass at the beginning of lactation, protein loss, weight loss, and ad libitum feed intake during lactation showed moderate heritabilities (0.39, 0.21, 0.20, and 0.30, respectively). Low to moderate heritabilities were found for litter weight at birth, within-litter SD in the birth weight of piglets, litter weight gain, fat loss, and restricted feed intake during lactation (0.19, 0.09, 0.18, 0.05, and 0.14, respectively). Within-litter SD in the weaning weight of piglets showed no genetic variability. It was predicted that a breeding goal for dam lines with an emphasis on the total number of piglets born, piglet mortality, and percent prolonged interval from weaning to estrus would not dramatically change BW or body composition at the beginning of lactation, or mobilization of body tissue and feed intake during lactation. Inclusion of LE in the breeding goal will improve stayability, as defined by the first-litter survival of sows and LE itself, without negative consequences for other economically important traits. Nevertheless, it might be worthwhile to design a breeding goal in which LE increases and feed intake remains unchanged.

Genetic parameters for thermoregulation and production traits in lactating sows reared in tropical climate

“…LBWg is genetically favorably related to sow's ADFI (r g = 0.25 ± 0.11) and more strongly related to sow's BW change (r g = 0.59 ± 0.20). Similar favorable genetic correlations have been reported by Bergsma et al (2008) but with higher values for genetic correlations between ad libitum feed intake and LBWg (r g = 0.48 ± 0.20) and lower values between LBWg and sow BW change (r g = 0.28 ± 0.20). High LBWg which partly reflected high milk production, leads to high BW loss during lactation as nutrient requirements during lactation are rarely fully covered by feed intake.…”

“…The genetic correlation between ADFI and sow proportion BW change during lactation was −0.80 ± 0.14 suggesting that sows with a high genetic merit for ADFI have less BW loss during lactation. This correlation was similar to the estimate of −0.62 ± 0.16 between ad libitum feed intake and BW change in Dutch climate (Bergsma et al, 2008). This correlation was expected because a genetic increase of sows voluntary feed intake reduces the utilization of maternal body reserves to support high nutrient requirements for milk production.…”

“…Actually, the authors used only two heritability estimations with high between study variance. The heritability estimate of LBWg was moderate (0.31 ± 0.09) and greater than the estimate of 0.18 ± 0.05 reported by Bergsma et al (2008). The heritability estimate of sow proportion of BW change during lactation (0.20 ± 0.07) was in accordance with the 0.20 heritability estimate of sow BW change score reported in Rydhmer's review (2000) or BW losses (in kilogram) reported by Bergsma et al (2008).…”

“…The heritability estimate of LBWg was moderate (0.31 ± 0.09) and greater than the estimate of 0.18 ± 0.05 reported by Bergsma et al (2008). The heritability estimate of sow proportion of BW change during lactation (0.20 ± 0.07) was in accordance with the 0.20 heritability estimate of sow BW change score reported in Rydhmer's review (2000) or BW losses (in kilogram) reported by Bergsma et al (2008). These values are slightly lower than the 0.13 ± 0.05 heritability estimate of change of BW of the sow during lactation reported by Gilbert et al (2012).…”

Body development in sows, feed intake and maternal capacity. Part 2: gilt body condition before and after lactation, reproductive performance and correlations with lactation feed intake

“…Currently published studies suggest that genetic correlations between intake during lactation and sow longevity are more ambiguous than phenotypic results. For example, the results of the study conducted by Lewis and Bunter (2011), Bergsma et al (2008) and Bunter et al (2009) show low genetic correlations between lactation feed intake and longevity. It is possible that considering lactation feed intake in combination with aspects of sow body condition and health will be more informative.…”