DERIVING ECONOMIC VALUES FOR REACTION NORMS OF GROWTH IN PIGS

SUMMARY Slopes of reaction norm models, also called reaction norms (RN), are alternative traits used in animal breeding for selection of genotypes that perform more consistently across a range of environments. Environmental sensitivity is of economic importance when the environment where selection takes place differs considerably from the commercial environment of slaughter pigs. The position on the environmental trajectory where intercept of reaction norm models is defined influences the economic values (EV) for slope and intercept. This position has to correspond to the trait definitions of intercept and slope of reaction norm models used to estimate variance components. The magnitude of EV for RN depends on the difference between the selection and production environments and the EV for the trait of interest. Economic values for RN may be negative or positive depending on whether the production environment is below or above the selection environment. Non-linear EV for growth across the environmental trajectory had minimal impact on the EV for RN of growth. Further genetic and economic analyses of extensive industry data are required to better quantify the economic importance of RN in pig breeding. INTRODUCTION Reaction norms quantify genotype by environment interactions by describing the response of genotypes to varying environmental conditions It was the aim of this paper to discuss economic implications of genetic differences in environmental sensitivity and to define EV for RN when selection is in the average environment using growth rate of pigs as an example trait

History and author analysis of the World Congresses on Genetics Applied to Livestock Production

It is almost fifty years since the first World Congress on Genetics Applied to Livestock Production (WCGALP) was convened in Spain in 1974. This paper, targeted for the early-career scientist session, details the history and evolution of WCGALP, and outlines gender composition of the Permanent International Committee, session chairs, plenary and invited speakers, and authors. Data containing 24,351 author records from all WCGALP proceedings, and old programs were used for the analyses. In the early years, there were few women involved in any aspect of WCGALP, however, more recent congresses have featured an increasing proportion of women on WCGALP committees and serving as session chairs. Based on recent data, gender is not playing a determining role in selection of submitted papers for oral presentations. We recommend greater gender diversity on WCGALP committees and encourage early-career scientists to actively participate in WCGALP conferences to further increase the diversity of future congresses

Life cycle assessment to predict individual environmental impacts: towards selection for sustainable pig production

A life cycle assessment approach is proposed to quantify four environmental impacts at the individual pig level. The approach was applied to two lines divergently selected for feed efficiency, including simulations of performances with two diets. Significant line differences were obtained with least-cost diets for environmental impacts and profit (P0.85), and moderate

Evaluation of milk yield losses associated with Salmonella antibodies in bulk-tank milk in bovine dairy herds

The effect of Salmonella on milk production is not well established in cattle. The objective of this study was to investigate whether introduction of Salmonella into dairy cattle herds was associated with reduced milk yield and the duration of any effect. Longitudinal data from 2005 through 2009 were used, with data from 12 months before until 18 months after the estimated date of infection. Twenty-eight case herds were selected based on an increase in the level of Salmonella specific antibodies in bulk-tank milk from < 10 corrected optic density percentage (ODC%) to ≥ 70 ODC% between two consecutive 3-monthly measurements in the Danish Salmonella surveillance program. All selected case herds were conventional Danish Holstein herds. Control herds (n = 40) were selected randomly from Danish Holstein herds with Salmonella antibody levels consistently < 10 ODC%. A date of herd infection was randomly allocated to the control herds. Hierarchical mixed effect models with the outcome test day energy corrected milk yield (ECM)/cow were used to investigate the daily milk yield before and after the estimated herd infection date for cows in parity 1, 2 and 3+. Control herds were used to evaluate whether the effects in the case herds could be reproduced in herds without Salmonella infection. Herd size, days in milk, somatic cell count, season, and year were included in the models. The key results were that first parity cow yield was reduced by a mean of 1.4 kg (95% CI: 0.5 to 2.3) ECM/cow per day from seven to 15 months after the estimated herd infection date, compared with first parity cows in the same herds in the 12 months before the estimated herd infection date. Yield for parity 3+ was reduced by a mean of 3.0 kg (95% CI: 1.3 to 4.8) ECM/cow per day from seven to 15 months after herd infection compared with parity 3+ cows in the 12 months before the estimated herd infection. There were minor differences in yield in second parity cows before and after herd infection, and no difference between cows in control herds before and after the simulated infection date. There was a significant drop in milk yield in affected herds and the reduction was detectable several months after the increase in bulk-tank milk Salmonella antibodies. It took more than a year for milk yield to return to pre- infection levels

Genotyping dead animals improves post-weaning survival of pigs in breeding programs

A premise was tested that genotyping both surviving and dead pigs will realise more genetic gain in post-weaning survival (PWS) than genotyping only surviving animals. Stochastic simulation was used to estimate the rate of true genetic gain in different genotyping scenarios that differed in varying proportions of genotyping dead animals. Selection was for only PWS that had heritability of 0.02. Mortality was assumed 10%. The trait was controlled by 7,702 biallelic quantitative trait loci distributed across a 30 Morgan genome. We used 54,218 biallelic single nucleotide polymorphisms (SNPs) that were used in genomic prediction. Genotyping both surviving and dead animals realised 12 to 24% more genetic gain than genotyping only surviving animals. The power of detecting SNP effects increased when animals of extreme phenotypes are genotyped. Therefore, genotyping both surviving and dead pigs realised more genetic gain than genotyping only surviving animals

Exploring breeding opportunities for reduced thermal sensitivity of feed intake in the lactating sow

The aims of this study were, first, to evaluate the effects of climatic variables on daily feed intake of lactating sows and, second, to establish whether the response of sows to variation in temperature on feed intake during lactation was heritable. A total of 82,614 records for daily feed intake during lactation were available for 848 sows with 3,369 litters farrowing from January 2000 to December 2007. Climatic parameters available from the nearest weather station were maximum 24 h outside temperature, day length changes, and humidity. Although ambient room temperature was modified at the animal level in the farrowing shed, these climatic variables still had a significant effect on feed intake during lactation. Regression coefficients temperature and humidity were 0.01385 ± 0.00300 (temperature) - 0.00031 ± 0.00009 (temperature2) and 0.01443 ± 0.00620 (humidity) - 0.00009 ± 0.00004 (humidity2). There was an interaction between temperature and humidity, partly due to the climate control in the farrowing shed. At low temperature, feed intake increased considerably with greater humidity, in contrast to a small reduction in feed intake with greater humidity at high temperature. Day length change was modeled with a cosine function. At the start of autumn (September 21), sows ate 0.36 ± 0.056 kg/d less feed than at the start of spring (March 21). Daily feed intake during lactation was described as a function of days in lactation and as a function of both days in lactation and temperature using random regression models. The average heritability and repeatability summarized over the day in lactation at the mean temperature were 0.21 and 0.69, respectively. Genetic variance of temperature response on feed intake was less than 20% of the day effect. The permanent environmental variance was 2-fold (day) and 4-fold (temperature) greater than the corresponding additive genetic variance. Heritabilities of daily feed intake were greater during the first week of lactation compared with the rest of lactation. The genetic correlation between days decreased as time increased down to about 0.2 between the first and last day in lactation. The genetic correlation between feed intake records at the extreme temperatures decreased to about -0.35. It was concluded that random regression models are useful for research and results may be used to develop simpler models that can be implemented in practical breeding programs. An effect of temperature on lactation feed intake was found even in this climate-controlled environment located in a temperate climate zone. Larger effects are expected in more extreme climatic conditions with less temperature-controlled farrowing sheds