IGF-1 Concentration at a Young Age is Associated with Feed Efficiency in Pigs

The concentration of IGF-I in blood of young pigs has previously been found to be genetically associated with feed efficiency and performance in pigs. To test these associations, data from the ISU selection line for residual feed intake (RFI) were used. Compared to controls, in the line selected for increased efficiency through reduced RFI, a correlated response in the expected downwards direction was observed for juvenile IGF-I. Genetic correlations of IGF-I were 0.63 with RFI and 0.78 with feed conversion ratio. These results confirm that juvenile IGF-I is a good physiological indicator of genetic merit for economically important efficiency traits, particularly since it is measured early in an animal’s life

Traits Defining Sow Lifetime Maternal Performance

Declining sow performance with increasing parity or an increase in the number of poor- quality pigs potentially impacts on farm productivity. This study investigated the phenotypic and genetic background of the sow's influence on (i) the number of pigs not meeting the industry standards (tail-enders) and (ii) changes in performance with parity. Data were available for 3592 sows and their litters (13,976 litters) from a pig production system in NSW, Australia. The mean, standard deviation (SD), and slope for trait values over time were estimated for the sow characteristic traits: number of born-alive (NBA) and stillborn (SB) piglets and body condition of sow recorded with a caliper (CAL), along with maternal effects on piglet performance, represented by: average piglet birth weight (APBW), number of weaned piglets (WEAN), and tail-enders (TEND). Traits were analyzed in ASReml 4.2, by using an animal model. The number of tail-enders produced by a sow is a heritable trait, with a heritability estimate of 0.14 ± 0.04. Sow characteristics and maternal effects on piglet performance expressed by mean and slope had similar heritability estimates, ranging from 0.10 ± 0.03 to 0.38 ± 0.05, whereas estimates for SD traits were generally not different from zero. The latter suggests individual variability in sow characteristics or maternal performance between parities is largely not genetic in origin. This study demonstrated that more attention is required to identify contributions to the problem of tail-enders, and that slope traits could potentially be useful in the breeding program to maximize lifetime performance

Feed intake and feeding behavior traits for gestating sows recorded using electronic sow feeders

Electronic sow feeding (ESF) systems are used to control feed delivery to individual sows that are group-housed. Feeding levels for gestating sows are typically restricted to prevent excessive body weight gain. Any alteration of intake from the allocated feeding curve or unusual feeding behavior could indicate potential health issues. The objective of this study was to use data recorded by ESF to establish and characterize novel feed intake and feeding behavior traits and to estimate their heritabilities. Raw data were available from two farms with in-house manufactured (Farm A) or commercial (Farm B) ESF. The traits derived included feed intake, time spent eating, and rate of feed consumption, averaged across or within specific time periods of gestation. Additional phenotypes included average daily number of feeding events (AFE), along with the cumulative numbers of days where sows spent longer than 30 min in the ESF (ABOVE30), missed their daily intake (MISSF), or consumed below 1 kg of feed (BELOW1). The appetite of sows was represented by averages of score (APPETITE), a binary value for allocation eaten or not (DA_bin), or the standard deviation of the difference between feed intake and allocation (SDA-I). Gilts took longer to eat than sows (15.5 ± 0.13 vs. 14.1 ± 0.11 min/d) despite a lower feed allocation (2.13 ± 0.00 vs. 2.36 ± 0.01 kg/d). The lowest heritability estimates (below 0.10) occurred for feed intake traits, due to the restriction in feed allocation, although heritabilities were slightly higher for Farm B, with restriction in the eating time. The low heritability for AFE (0.05 ± 0.02) may have reflected the lack of recording of nonfeeding visits, but repeatability was moderate (0.26 ± 0.03, Farm A). Time-related traits were moderately to highly heritable and repeatable, demonstrating genetic variation between individuals in their feeding behaviors. Heritabilities for BELOW1 (Farm A: 0.16 ± 0.04 and Farm B: 0.15 ± 0.09) and SDA-I (Farm A: 0.17 ± 0.04 and Farm B: 0.10 ± 0.08) were similar across farms. In contrast, MISSF was moderately heritable in Farm A (0.19 ± 0.04) but lowly heritable in Farm B (0.05 ± 0.07). Heritabilities for DA_bin were dissimilar between farms (Farm A: 0.02 ± 0.02 and Farm B: 0.23 ± 0.10) despite similar incidence. Individual phenotypes constructed from ESF data could be useful for genetic evaluation purposes, but equivalent capabilities to generate phenotypes were not available for both ESF systems

Improving sow welfare and outcomes in the farrowing house by identifying early indicators from pre-farrowing assessment

Poor outcomes reflect low performance during the farrowing and lactation periods and unanticipated sow removals. Since the period around farrowing has the highest risk for sow health issues, monitoring of sows in that time-period will improve both welfare and productivity. The aim of this study was to identify the most relevant risk factors for predicting poor outcomes and the implication for sow welfare. Identifying these factors could potentially enable management interventions to decrease incidences of compromised welfare or poor performance. Data from 1,103 sows sourced from two nucleus herds were recorded for a range of variables investigated as potential predictors of poor outcomes in the farrowing house. Poor outcomes (scored as binary traits) reflected three categories in a sow's lifecycle: farrowing, lactation, and removals. Univariate logistic regression was used to identify predictors in the first instance. Predictors from univariate analyses were subsequently considered together in multi-variate models. The least square means representing predicted probabilities of poor outcomes were then reported on the observed scale. Several predictors were significant across two different environments (farms) and for all three categories. These predictors included feed refusal (lack of appetite), crate fit, locomotion score, and respiration rate. Normal appetite compared to feed refusals reduced the risk of farrowing failure (13.5 vs. 22.2%, P = 0.025) and removals (10.4 vs. 20.4%, P P P = 0.025) and reduced piglet mortality (P P P = 0.014). Sows with higher respiration rates had a significantly (

The Heritability of the Expression of Two Stress-Regulated Gene Fragments in Pigs

Pigs reared in commercial production units sometimes encounter stressors that significantly decrease growth performance. It is hypothesized that response to stress challenges could potentially be used as selection criteria. This study aimed to investigate, in a commercial setting, the heritability of two target genes previously shown to be induced in response to stress, and related to growth performance, in an experimental situation. Blood samples (n = 2,392) were collected from three separate breeding lines of pedigreed and performance-tested boars between 24 to 25 wk of age. The expression levels of a novel fragment, '29a,' and the calcitonin receptor gene (CTR) were quantified using quantitative real-time PCR (qRT-PCR) on a subset (n = 709) of the blood samples. Gene expression levels were corrected for the efficiency of PCR reactions and also computed directly from threshold cycle (Ct) values. Resulting data showed a skewed nonnormal distribution of expression levels for the target genes relative to the endogenous control, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and were highly variable. Analyses were subsequently performed using untransformed and log-transformed data, with outliers identified and deleted in edited data sets. Regardlessof the transformation or editing procedures for outliers applied, there was negligible genetic variation for the expression of target genes relative to GAPDH. In contrast, repeatabilities of replicate samples were generally high (between 0.54 and 0.67). Absolute expression levels for GAPDH and 29a were lowly heritable (h² ofabout 0.04), although estimates did not exceed their SE. Subsetting the data according to whether the target gene had a higher or lower level of expression than GAPDH was then performed using the relevant Ct values. In the subset where the target gene was more highly expressed than GAPDH, a moderate estimate of heritability (0.18 ± 0.10) for the log-transformed absolute expression level of 29a was obtained, whereas the estimate for its expression relative to GAPDH was lower (0.09 ± 0.07). Estimates of heritability did not increase in the subset of low expression data. The limitations of using gene expression measures as potential selection criteria in commercial situations are discussed

Behavioural Traits Recorded in Gilts and Associations with Reproductive Performance as Group-Housed Sows

Gilts from two maternal lines were recorded for flight time (FT, N=8854) and scored for the count of lesions resulting from fighting 24 hours after selection and mixing into new groups (N=3238). Anterior (ANT) and posterior lesion counts were scored on a progressive four point scale representing none to multiple lesions (0-3), and aggressive gilts (0/1 scores) were defined by ANT>1. Lesion counts over the whole body were subsequently rescored pre-farrowing (PFBLES). Genetic correlations were estimated between these behavioural traits and average daily gain (ADG), gilt removals without a farrowing event and first parity litter size (TB: total born; NBA: number born alive) and birth weight. All behavioural traits scored for gilts and pregnant sows prefarrowing were lowly to moderately heritable (h²1. Lesion counts over the whole body were subsequently rescored pre-farrowing (PFBLES). Genetic correlations were estimated between these behavioural traits and average daily gain (ADG), gilt removals without a farrowing event and first parity litter size (TB: total born; NBA: number born alive) and birth weight. All behavioural traits scored for gilts and pregnant sows prefarrowing were lowly to moderately heritable (h

Breeding sows better suited to group housing

Housing of pregnant sows is currently being revolutionised around the world. Group housing enhances opportunities for improved sow health and welfare through enabling exercise and social interactions. However, because it enables social interactions, group housing can also be detrimental to welfare and production, particularly if sow aggression occurs. Detrimental effects of adverse interactions between sows include increased injuries to sows, poor body condition and ultimately reproductive failure due to increased stress, all of which will contribute to increased rates of sow culling. Achieving both favourable welfare and reproductive outcomes for group housed sows is possible, but it relies on establishing low stress levels, favourable social interactions and sufficient feed intake for all sows. This requires not only well designed facilities coupled with appropriate animal management; it also requires populations of individual sows that are physically and behaviourally better suited towards group housing systems. This project is intended as a step towards developing breeding programs to create these populations

Managing Consequences of Increasing Litter Size: A Genetic Perspective

Selection for efficient lean growth and litter size can have detrimental consequences for piglet survival. However, survival traits themselves are lowly heritable, making it possible to select for improved survival directly in breeding programs. The generally low magnitudes of unfavourable genetic correlations between traits indicate it is possible to achieve genetic gains in production, litter size and survival traits concurrently. To select for piglet survival successfully requires the implementation of extensive data recording for individual mortality, combined with best-linear unbiased prediction (BLUP) genetic evaluation methodology. Accurate genetic evaluation of piglet mortality is complicated by the categorical nature of some trait definitions, low heritability, the large scale of recording required, population specific management and cross-fostering effects, and potentially the presence of both piglet and sow related genetic and environmental components affecting outcomes. In addition, while prenatal, postnatal and late lactation phases of piglet survival are not strictly independent events, the best approach to selection might differ depending on the relative contributions of each phase to piglet deaths. It is unlikely that there is a generic approach which is universally optimal for all breeding operations. The combination of high performance computing and inexpensive data storage has increased capabilities to apply more complex genetic evaluation procedures, which continue to alter possibilities for selection in this area. However, the efficacy of the chosen strategy should be validated in commercial populations. All breeding companies agree that a balanced breeding goal will include strategies to reduce piglet losses

Fighting of gilts after mixing is associated with early removals, altered litter sex ratio and lower piglet survival

Aggressive behaviour can compromise the welfare of group-housed gilts and sows and affect reproductive performance (Spoolder et al. 2009), but the extent of individual aggression is frequently unknown. Lesions resulting from fighting indicate the intensity and extent of aggressive encounters between sows (Bunter and Boardman 2015). The aim of this study was to investigate if lesions resulting from fighting amongst gilts were associated with subsequent reproductive outcomes for group-housed sows

Piglet Attributes at Birth Can Influence Survival

Piglet attributes at birth are important for postnatal survival. Knot et al. (2002) demonstrated that some aspects of piglet quality had declined due to prior selection for improved production efficiency. Determining attributes (eg. birth weight, rectal temperature, crown-to-rump length) which define better piglet quality and therefore an improved survival rate may enable producers to identify "at risk" piglets (for intervention) and potentially new selection criteria for breeding programs. We hypothesise that individual piglet attributes evaluated soon after birth in a commercial setting are associated with their survival until weaning