Brandon D. Velie

Genetic relationships among pig behavior, growth, backfat, and loin muscle area.

The objective of this study was to estimate repeatabilities and heritabilities for measures of pig behavior and their relationship with performance. Measures of behavior and performance included the backtest, resident-intruder test, human approach test (HAT), novel object test (NOT), d 1 BW, backfat depth (BF), loin muscle area (LMA), ADG in the farrowing house, ADG, 21-d BW, and 140-d BW (W). Each behavioral trait was measured twice. The study consisted of 95 litters from 31 sires with an average of 3 litters per sire (n >or= 457). Between 7 and 14 d of age, the backtest was conducted by placing each pig in a supine position for 60 s. Total time spent struggling (TTS) and total number of attempts to struggle (TAS) were recorded. The resident intruder test involved 2 nursery pigs, a resident pig and an unfamiliar intruder pig. The resident pen was divided in half by a solid partition. A resident pig was placed in the test area, and an intruder pig was then introduced. Latency until an attack occurred (LAT) and total number of attacks over 2 tests (RIS) were recorded. Amount of time taken for each finishing pig to make snout contact with an unfamiliar human or object was recorded. Dam and sire effects influenced all traits (P < 0.01). Sex and pen affected LAT, RIS, HAT, and NOT (P < 0.10). Repeatabilities of TTS, TAS, RIS, LAT, HAT, and NOT were 0.38, 0.21, 0.07, 0.08, 0.17, and 0.11, respectively. The phenotypic correlations of TTS with TAS and HAT with NOT were 0.61 and 0.34, respectively. Phenotypic correlation between RIS and LAT was -0.85. Total time spent struggling and TAS tended to be phenotypically correlated with 21-d BW and ADG in the farrowing house. Total attempts to struggle were phenotypically correlated with BF (0.15). Latency until an attack occurred was phenotypically correlated with LMA (0.23). Resident intruder score was phenotypically correlated with ADG (-0.13), W (-0.13), and LMA (-0.21) and estimated to be lowly heritable (h(2) = 0.12). Heritabilities of TTS and TAS were 0.31 and 0.53, respectively. Genetic correlation of TAS with ADG and W was 0.38. Genetic correlations of TTS with BF, W, and TAS were 0.14, 0.18, and 0.81, respectively. The backtest is a heritable and repeatable measure of a behavioral characteristic in pigs that is phenotypically and genetically correlated with performance.

The association of age at first start with career length in the Australian Thoroughbred racehorse population

REASONS FOR PERFORMING STUDY Studies of Thoroughbred racing populations have provided evidence of a positive effect on racing careers for horses that commence racing as 2-year-olds. Currently, research investigating the presence of this effect in the Australian Thoroughbred racing population is limited. OBJECTIVES To investigate the association between age at first start and career length in the Australian Thoroughbred population and estimate the risk of racing retirement for horses racing in Australia based on age at first start, career earnings, number of starts as a 2-year-old and distance raced. METHODS Data were collected for Thoroughbreds, born on or after 1 January 1998, that had raced between 1 August 2000 and 22 February 2011 in Australia. A Kaplan-Meier survival curve, stratified by age group, was produced for career length. A Cox proportional hazard model was fitted to assess factors influencing the risk of retirement from racing. The model included sex, age at first start, career earnings, number of starts as a 2-year-old, distance raced and appropriate interaction terms. RESULTS The study population included 117,088 horses. Geldings had significantly (P<0.001) longer careers than females and intact males, and females had significantly (P<0.001) longer careers than intact males. Risk of retirement from racing decreased with a younger age at first start, a higher number of starts as a 2-year-old, and a longer average distance raced. For intact males, the risk of retirement from racing increased as earnings increased, while for females and geldings the risk of retirement from racing decreased as earnings increased. CONCLUSIONS AND POTENTIAL RELEVANCE The introduction of young Thoroughbreds to racing appears to have no apparent adverse effects on these horses racing in Australia. The impact of some risk factors associated with retirement from racing varied between sexes and should be considered when evaluating career outcomes.

The association of age at first start with career length in the Australian racehorse population

REASONS FOR PERFORMING STUDY Studies of Thoroughbred racing populations have provided evidence of a positive effect on racing careers for horses that commence racing as 2-year-olds. Currently, research investigating the presence of this effect in the Australian Thoroughbred racing population is limited. OBJECTIVES To investigate the association between age at first start and career length in the Australian Thoroughbred population and estimate the risk of racing retirement for horses racing in Australia based on age at first start, career earnings, number of starts as a 2-year-old and distance raced. METHODS Data were collected for Thoroughbreds, born on or after 1 January 1998, that had raced between 1 August 2000 and 22 February 2011 in Australia. A Kaplan-Meier survival curve, stratified by age group, was produced for career length. A Cox proportional hazard model was fitted to assess factors influencing the risk of retirement from racing. The model included sex, age at first start, career earnings, number of starts as a 2-year-old, distance raced and appropriate interaction terms. RESULTS The study population included 117,088 horses. Geldings had significantly (P<0.001) longer careers than females and intact males, and females had significantly (P<0.001) longer careers than intact males. Risk of retirement from racing decreased with a younger age at first start, a higher number of starts as a 2-year-old, and a longer average distance raced. For intact males, the risk of retirement from racing increased as earnings increased, while for females and geldings the risk of retirement from racing decreased as earnings increased. CONCLUSIONS AND POTENTIAL RELEVANCE The introduction of young Thoroughbreds to racing appears to have no apparent adverse effects on these horses racing in Australia. The impact of some risk factors associated with retirement from racing varied between sexes and should be considered when evaluating career outcomes.

Heritability of racing performance in the Australian Thoroughbred racing population

Performance data for 164,046 Thoroughbreds entered in a race or official barrier trial in Australia were provided by Racing Information Services Australia. Analyses estimating the heritability for a range of racing performance traits using a single-trait animal model were performed using ASREML-R. Log of cumulative earnings (LCE; 0.19 ± 0.01), log of earnings per race start (0.23 ± 0.02) and best race distance (0.61 ± 0.03) were all significantly heritable. Fixed effects for sex were significant (P < 0.001) for all performance traits aside from LCE (P = 0.382). With the exception of annual earnings, trainer was also significant for all performance traits. As the application of modern genetic selection methodologies continues to gain popularity in the racing industry, contemporary heritability estimates from the current population of Thoroughbreds will play a vital role in identifying which traits are better suited to selection and in the development of more accurate genomic evaluations for racing performance.

Profiling the careers of Thoroughbred horses racing in Australia between 2000 and 2010

REASONS FOR PERFORMING STUDY Research investigating trends in racehorse careers require a benchmark for accurate comparison. Currently little whole population data exists for horses racing in Australia. OBJECTIVES To determine the range and variation in career length and number of career starts for horses racing in Australia. To document and provide evidence regarding the current differences between the sexes for career length and careers starts. METHODS Racing data were collected for Thoroughbreds over a 10-year period. Career length, number of career starts and spells per year were evaluated. Statistical analyses were performed using the statistical package R. RESULTS A total of 2,782,774 performance records yielded career information for 164,046 horses. Median career length and number of career starts for the population were 14.7 months and 10 starts, respectively. Significant differences (P<0.001) were present between the sexes for all career outcomes. Between 2000 and 2010, the percentage of Thoroughbreds racing in Australia with careers longer than 12, 24, 36 and 48 months was 56.65, 32.35, 16.66 and 7.74, respectively. CONCLUSIONS AND POTENTIAL RELEVANCE Clear differences in career outcomes exist between intact males, females and geldings racing in Australia. Future research should be conscious of these differences when analysing population data.

Using an Inbred Horse Breed in a High Density Genome-Wide Scan for Genetic Risk Factors of Insect Bite Hypersensitivity (IBH).

While susceptibility to hypersensitive reactions is a common problem amongst humans and animals alike, the population structure of certain animal species and breeds provides a more advantageous route to better understanding the biology underpinning these conditions. The current study uses Exmoor ponies, a highly inbred breed of horse known to frequently suffer from insect bite hypersensitivity, to identify genomic regions associated with a type I and type IV hypersensitive reaction. A total of 110 cases and 170 controls were genotyped on the 670K Axiom Equine Genotyping Array. Quality control resulted in 452,457 SNPs and 268 individuals being tested for association. Genome-wide association analyses were performed using the GenABEL package in R and resulted in the identification of two regions of interest on Chromosome 8. The first region contained the most significant SNP identified, which was located in an intron of the DCC netrin 1 receptor gene. The second region identified contained multiple top SNPs and encompassed the PIGN, KIAA1468, TNFRSF11A, ZCCHC2, and PHLPP1 genes. Although additional studies will be needed to validate the importance of these regions in horses and the relevance of these regions in other species, the knowledge gained from the current study has the potential to be a step forward in unraveling the complex nature of hypersensitive reactions.

Performance selection for Thoroughbreds racing in Hong Kong

REASONS FOR PERFORMING STUDY Different indicators of racing performance are commonly used in the racing industry to assess the genetic superiority of racing Thoroughbreds. However, how well these indicators predict the performance of future progeny or siblings varies depending on the population and circumstances in which the indicators were recorded or achieved. OBJECTIVES To identify heritable indicators of racing performance for horses racing in Hong Kong. STUDY DESIGN Heritability analysis of racing performance traits. METHODS Performance data on the population of Thoroughbreds racing in Hong Kong between 3 September 2000 and 12 March 2011 (n = 4947) were acquired and used to estimate the heritabilities and probability values of fixed effects and covariates for a range of racing performance traits. Heritabilities for all performance traits were estimated using a single trait animal model. Each model included, as a minimum, the effects of sex, region of origin and trainer. RESULTS Heritability estimates for traits relating to finish position ranged from 0.01 to 0.06. Average handicap weight had a heritability of 0.07 ± 0.03. The effects of sex (fixed) and trainer (random) were significant (P<0.05) for all performance traits relating to earnings measures, handicap weights and finish positions. The heritability of win time at 1600 m was 0.52 ± 0.06 and was the only significant estimate of heritability for win time in the current study. CONCLUSIONS Although significantly affected by multiple environmental factors, certain indicators of Hong Kong racing performance can be reliably used to predict the performance of the individuals progeny or siblings. However, despite Hong Kongs controlled racing environment, these indicators appear to be no more heritable than in other less controlled racing environments.

Heritability of racing durability traits in the Australian and Hong Kong Thoroughbred racing populations

REASONS FOR PERFORMING STUDY Many attempts have been made to improve the well-being of racing Thoroughbreds through improvements in management and veterinary care. However, these attempts are often limited by the industrys ability to regulate a large number of environmental variables and as a result have arguably had limited success in providing long-lasting change for the breed. OBJECTIVES To identify heritable durability traits for Thoroughbred horses racing in Australia and Hong Kong. STUDY DESIGN Heritability analysis of a longitudinal dataset. METHODS Performance data on the Thoroughbred populations racing in Australia and Hong Kong between 2000 and 2011 (n = 168,993) were used to estimate the heritabilities and probability values of fixed effects and covariates for a range of racing durability traits. Heritabilities for all durability traits were estimated using a single trait animal model. Each model included, as a minimum, the effects of sex and trainer. RESULTS Racing longevity (0.12 ± 0.01), racing persistence (0.10 ± 0.01), racing frequency (0.03 ± 0.01), spells (a time period between consecutive races, official trials and/or jump-outs greater than 90 days in length) per year (0.05 ± 0.01), spells per 10 starts (0.03 ± 0.01) and variation of days between races (0.08 ± 0.03) were all significantly heritable for horses racing in Australia. Racing longevity (0.08 ± 0.02), racing persistence (0.04 ± 0.02), spells per year (0.06 ± 0.02) and spells per 10 starts (0.11 ± 0.04) were significantly heritable for horses racing in Hong Kong. CONCLUSIONS The heritabilities estimated for durability traits in this study provide support for the successful and practical application of genetic selection methodologies to improving the well-being of racing Thoroughbreds.

Profiling the careers of Thoroughbred horses racing in Hong Kong between 2000 and 2010.

REASONS FOR PERFORMING STUDY Research in Thoroughbred racehorses is often specific to horses from a given racing population or region. In order to investigate trends in racehorse careers across populations accurately, population-specific benchmarks for performance outcomes must be established. OBJECTIVES To provide summary statistics for performance outcomes for Thoroughbreds racing in Hong Kong between 2000 and 2010 and to document and provide evidence on the current differences in racing careers across sexes and regions of origin for horses racing in Hong Kong. STUDY DESIGN Performance data on the population of Thoroughbreds racing in Hong Kong between 3 September 2000 and 12 March 2011 (n = 4950) were acquired and used to describe and compare the careers of Thoroughbred racehorses in Hong Kong. METHODS Career length, number of career starts and number of spells from racing per year were evaluated. Kaplan-Meier survival curves, stratified by sex, age group, country of origin and region of origin were produced for career length. A Coxs proportional hazards model was fitted to assess factors influencing the risk of retirement from racing in Hong Kong. RESULTS Log-rank tests for equality of career length survivor functions showed significant differences (P<0.001) across sexes, age groups, countries of origin and regions of origin. An increased age at first start in Hong Kong tended to increase the hazard rate for retirement from racing in Hong Kong, whereas greater earnings per race and originating from Europe tended to reduce the hazard rate for racing retirement. CONCLUSIONS AND POTENTIAL RELEVANCE Differences in career outcomes within a racing population appear to be influenced partly by the region from which a horse originates, with specific effects on each performance outcome also varying between regions. Future research should take into account these potential differences when comparing results across populations.

Lack of significant associations with early career performance suggest no link between the DMRT3 "Gait Keeper" mutation and precocity in Coldblooded trotters

The Swedish-Norwegian Coldblooded trotter (CBT) is a local breed in Sweden and Norway mainly used for harness racing. Previous studies have shown that a mutation from cytosine (C) to adenine (A) in the doublesex and mab-3 related transcription factor 3 (DMRT3) gene has a major impact on harness racing performance of different breeds. An association of the DMRT3 mutation with early career performance has also been suggested. The aim of the current study was to investigate this proposed association in a randomly selected group of CBTs. 769 CBTs (485 raced, 284 unraced) were genotyped for the DMRT3 mutation. The association with racing performance was investigated for 13 performance traits and three different age intervals: 3 years, 3 to 6 years, and 7 to 10 years of age, using the statistical software R. Each performance trait was analyzed for association with DMRT3 using linear models. The results suggest no association of the DMRT3 mutation with precocity (i.e. performance at 3 years of age). Only two traits (race time and number of disqualifications) were significantly different between the genotypes, with AA horses having the fastest times and CC horses having the highest number of disqualifications at 3 years of age. The frequency of the AA genotype was significantly lower in the raced CBT sample compared with the unraced sample and less than 50% of the AA horses participated in a race. For the age intervals 3 to 6 and 7 to 10 years the AA horses also failed to demonstrate significantly better performance than the other genotypes. Although suggested as the most favorable genotype for racing performance in Standardbreds and Finnhorses across all ages, the AA genotype does not appear to be associated with superior performance, early or late, in the racing career of CBTs.