Designing an early selection morphological traits index for reproductive efficiency in Pura Raza Española mares.

The low rate of reproductive efficiency in horses may be linked to the equine industry's practice of maintaining breeding stock that stands out for its athletic or morphological performance but exhibits poor reproductive efficiency. In this study, the age at first foaling, age at last foaling, interval between first and second foaling, average interval between foaling, foaling number and reproductive efficiency, and their relationship with the morphological records in 19,758 Pura Raza Española (PRE) mares were analyzed. After a partial least squares analysis height at withers, lateral hock angle, dorsal-sternal diameter, perimeter of anterior cannon bone, angle of shoulder, thoracic perimeter, hip-stifle distance, and angle of croup were the most important traits related with reproductive traits in PRE mares. A multivariate animal model with both morphological and reproductive traits was applied, including age, geographical area, coat color, and average stud size in the decade of the mare's first foaling. The results indicate that reproductive selection is feasible, and is enhanced by the use of morphological traits, given the moderate to high magnitudes of heritability values in both types of traits, which oscillated between 0.1 (interval between first and second foaling) and 0.95 (height at withers). The resulting genetic parameters were used to develop a series of selection indexes based on morphological or morphological and reproductive combination traits to improve reproductive efficiency traits in PRE mares and thus compute the expected genetic response (EGR) for the different strategies. The increase in EGR, when comparing EGR using only reproductive traits as selection criteria vs. using a combined index of both morphological and reproductive traits, oscillated between 4.0% for the age at first foaling to 46.8% for the interval between first and second foaling. In addition, two precocity indexes showed positive EGR when the age at last foaling and the interval between first and second foaling, both with and without morphological traits, were used as selection criteria. Therefore, this analysis reveals that the preselection of reproductive traits based on morphological traits is possible in PRE mares. Ultimately, this knowledge will help breeders achieve genetic progress in reproductive traits, leading to healthier and more successful breeding outcomes in horses.

Historically in livestock production, employing combinations of traits as selection criteria for indirect selection of related traits has been a challenging task, particularly when this implies selection for reproductive traits based on the animal morphology. However, if the decision about animal selection is based on morphological traits that are quick and easy to obtain, in addition to early reproductive traits, selection responses can be improved and made earlier. This is particularly significant in sport horse breeds like the Pura Raza Española horse, which is primarily used for dressage competitions. Mares belonging to this breed commonly engage in several years of competition before transitioning to breeding, without the breeders having prior knowledge of their reproductive efficiency. Nonetheless, the availability of existing morphological information enables us to make informed decisions in this regard. While a selection index using morphology alone would not yield as good a response as direct selection for reproductive traits, there are cases, such as age at last foaling, where the correlated response can be very high. Our study further illustrates a substantial increase in selection response when morphological and reproductive traits are jointly included as selection criteria, with the aim of enhancing reproductive efficiency.

Phenotypic and Genetic Study of the Presence of Hair Whorls in Pura Raza Español Horses.

Hair whorls are a hereditary feature in horses that may be associated with temperament and coat color. Hair whorls are described as changes in the hair pattern and may take various forms, such as circular and linear whorls. We first carried out a frequency analysis of hair whorls (circular and linear). Next, a Generalized Non-Linear Model was computed to assess the significance of some potential influencing factors, and a genetic parameter estimation was performed. ENDOG software v4.8 was used to estimate the inbreeding coefficient of all the animals analyzed. It was more common to find horses with circular hair whorls than with linear whorls. The heritability ranges obtained were, in general, medium-high for both circular whorls (0.20 to 0.90) and linear whorls (0.44 to 0.84). High positive correlations were found on the between left and right positions, indicating a tendency to symmetry in certain locations. The laterality of hair whorls was also evidenced, with the biggest concentration on the left-hand side, particularly in gray horses, showing circular whorls below the central line of eyes, which has been associated in a previous paper with a calmer and more docile temperament.

The Relevance of the Expected Value of the Proportion of Arabian Genes in Genetic Evaluations for Eventing Competitions.

The Arabian horse is a generally reliable sport horse, and continues to be a remarkable endurance horse, so the relevance of the expected value of the proportion of Arabian genes (EV%AG) in horses participating in eventing could be a relevant factor. A total of 1089 horses participating in eventing (8866 records) were used. A GLM revealed that the EV%AG was significant in dressage, show jumping and cross-country. A BLUP genetic evaluation was computed with five genetic models (without the EV%AG (0) using as a covariate (A), as a fixed effect (B), with variance heterogeneity, and in genetic groups without (C) and with (D)). Dressage heritability ranged from 0.103 to 0.210, show jumping ranged from 0.117 to 0.203 and cross-country ranged from 0.070 to 0.099. The lowest DIC value was used as a criterion of fitness. The best fits (those which included variance heterogeneity) showed fewer than two points of difference in DIC values. The highest average estimated breeding value in dressage, show jumping and cross-country was found for horses with an expected value of the proportion of Arabian genes of 0%, ≥1% to <25%, and 100%, respectively. Therefore, the best way to model the EV%AG effect seems to be by considering the variance heterogeneity.

Basal Reactivity Evaluated by Infrared Thermography in the "Caballo de Deporte Español" Horse Breed According to Its Coat Color.

Horses have been valued for their diversity of coat color since prehistoric times. In particular, the pleiotropic effect that coat color genes have on behavior determines the way the horse perceives and reacts to its environment. The primary aim of this study was to evaluate the influence of coat color on basal reactivity assessed with infrared thermography as eye temperature at rest (ETR), determine their relation with the results obtained by these horses in Show Jumping competitions and to estimate the genetic parameters for this variable to test its suitability for genetic selection. A General Linear Model (GLM) and Duncan post-hoc analysis indicated differences in ETR due to coat color, sex, age, location, and breed-group factors. A Spearman's rank correlation of 0.11 (p < 0.05) was found with ranking, indicating that less reactive horses were more likely to achieve better rankings. Heritability values ranged from 0.17 to 0.22 and were computed with a model with genetic groups and a model with residual variance heterogeneity. Breeding values were higher with the last genetic model, thus demonstrating the pleiotropic effect of coat color. These results indicate that ETR has a suitable genetic basis to be used in the breeding program to select for basal reactivity due to coat color.

Morpho-Functional Traits in Pura Raza Menorquina Horses: Genetic Parameters and Relationship with Coat Color Variables.

The studbook of Pura Raza Menorquina horses only permits the use of black-coated animals with a small quantity of white marks as breeding stock. Its breeding program uses linear morpho-functional traits as selection criteria. Our aim was to estimate the genetic parameters of linear morpho-functional traits, and reveal relationship of quality of black coat color (QB) and percentage of white marks (WM) with the other morphological and functional linear traits in this breed. A total of 46 linear traits were scored by four appraisers using seven classes, with a total of 772 records from 333 animals (≥4 years old). Univariate animal models using a Bayesian approach were used, with a pedigree of 757 animals. Sex (two) and appraiser-season (13) were included as fixed effects, age as a linear covariate, and permanent environmental and additive genetic as random effect. The heritabilities of the morpho-functional traits were low to medium (0.09-0.58) and matched the range in the bibliography. Heritabilities for coat color traits were 0.36 for QB and 0.23 for WM. The highest genetic correlations were obtained between QB and upper neck line (0.816) and between WM and form of the hoof (0.638). The negative signs of most of the genetic correlations between WM and the functional traits is also remarkable, contributing to the selection of functional traits against the presence of white marks in this population. A clear genetic differentiation was observed between animals with better breeding values for QB and WM, corroborated by a study on founders. In conclusion, QB and WM could show different genetic backgrounds.

Effects of Selection on Breed Contribution in the Caballo de Deporte Español.

The equine breeding industry for sport's performance has evolved into a fairly profitable economic activity. In particular, the Caballo de Deporte Español (CDE) is bred for different disciplines with a special focus on Show Jumping. The main aim of this study was to determine the effects of 15 years of selection and to find out whether it has been effective and adequate regarding the CDE main breeding objectives. The whole pedigree of 19,045 horses registered as CDE was used, comprising 47,884 animals (18,799 males and 29,085 females). An analysis performed to check for the pedigree completeness level yielded a number of equivalent complete generations (t) equal to 1.95, an average generation interval (GI) of 10.87 years, mean inbreeding coefficient (F) of 0.32%, an average relatedness coefficient (AR) of 0.09% and an effective population size (Ne) of 204. For the analyses, animals were divided into fourteen breed groups. Additionally, in order to study the evolution of these breeds over time and their influence on CDE pedigree, five different periods were considered according to the year of birth of the animals. Performance data used in the analyses were the estimated breeding values (EBV) of the Show Jumping sport discipline of 12,197 horses in the CDE pedigree, available from the 2020 routine genetic evaluations of the CDE breeding program (starting in 2004). Dressage and Eventing EBV values were also assessed. Results showed values of F higher than expected under random mating; this pointed to some degree of inbred matings. With regard to the evolution of breeding values, we found that, in general, EBVs of offspring were higher than the EBVs of parents. Notwithstanding, there is still a need for improvement in population management and the coordination of the breeders to get higher responses but controlling the loss of genetic diversity in the CDE breed.

Genetic inbreeding depression load for fertility traits in Pura Raza Española mares.

Fertility is a key factor in the economic success of horse farms. However, it has received little attention due to the difficulty of measuring fertility objectively. Since its studbook creation (1912), the Pura Raza Española (PRE) breed has been a closed population and become high in-bred resulting in inbreeding depression (poor phenotypic values). Nevertheless, heterogeneous effects of inbreeding depression have been detected among founders and nonfounders. The aims of this study were (1) to analyze the genetic parameters for reproductive traits in mares of the PRE horse breed and (2) to estimate, for the first time, the inbreeding depression load associated with common ancestors of the breed. A total of 22,799 mares were analyzed. Heritability estimates ranged from 0.05 (interval between first and second foaling) to 0.16 (age at first foaling), whereas inbreeding depression load ratios ranged from 0.06 (parturition efficiency at 6th foaling) to 0.17 (age at first foaling), for a partial inbreeding coefficient of 10%. Although heritability is related to the variability expressed in the population, inbreeding depression load ratios measure the potential variability, whether expressed in the population or not. Most correlations between additive and inbreeding depression load genetic values were significant (P < 0.001) and of low to moderate magnitude. Our results confirm that individual inbreeding depression loads allow us to select horses that have a genetic value resistant to the deleterious effects of inbreeding.

Genetic Parameters of Effort and Recovery in Sport Horses Assessed with Infrared Thermography.

The way a horse activates (effort phase-EP) and recovers (recovery phase-RP) during a sport event can affect its sport performance. The aim of this manuscript was to test horses' adaptation to sport performance and its genetic basis, using eye temperature assessed with infrared thermography. EP and RP were measured in 495 Spanish Sport Horses, during a performance test, considering sex (2) and genetic lines (5) as fixed effects. The ranking position obtained on an official sport competition was also collected. Differences in variables due to genetic line and sex effects were found, showing that, regardless of the genetic line, stallions tended to recover better than mares after the sport test developed. High positive intra-class correlations (p < 0.001) were found between EP and RP for both fixed effects, so that the higher the EP, the higher the RP. However, for the ranking position, a low negative correlation (p < 0.01) was found, so that the higher the eye temperature increase, the better the position. Heritabilities showed medium-high values with a medium positive genetic correlation between them. Thus, breed origins and sex influence horses' effort and recovery during sport performance, showing a genetic basis adequate for selection.

Testing eye temperature assessed with infrared thermography to evaluate stress in meat goats raised in a semi-intensive farming system: a pilot study.

The Blanca Serrana goat is selected for meat production and usually raised in an extensive farm system. The meat goat industry is getting bigger in Spain, evolving to more intensive farming systems. The negative influence of stress produced by daily management on animal welfare is even bigger in these animals as they are not used to getting so close to humans. Eye temperature has recently appeared as an appropriate and noninvasive tool for welfare assessment in cattle, but no previous studies have been developed in goats. Thus, the main aim of this pilot study was to test eye temperature as a noninvasive tool to explore stress levels associated with a semi-intensive farming system for meat goats in comparison with the standard measurements of stress. For that, 24 Blanca Serrana goats were used. Heart rate (HR), respiratory rate (RR) and eye temperature (ET), assessed with infrared thermography samples, were collected just before and just after a stressful situation created to check how the routine management of semi-intensive farming systems affected this species. A factorial ANOVA, least square means and Scheffé post hoc comparison analyses found statistically significant differences due to the stress test moment for RR ( p < 0.05 ) and ET ( p < 0.001 ) with higher values shown after the stress test than before it. Differences due to age were found just for HR ( p < 0.05 ) and RR ( p < 0.01 ) stress parameters, with kids showing higher results than adults. Pearson correlations between HR, RR and ET parameters showed a medium-high positive correlation of 0.56 between RR and ET. Thus, ET appears as an appropriate and noninvasive tool to explore stress levels associated with a semi-intensive farming system for meat goats.

Genealogical and morphological analysis of Lusitano Purebred horses participating at international Dressage competitions.

The International Equestrian Federation (FEI) ranks horses participating in dressage tests resulting in a prestigious list where equestrians would like to see their horses ranked. The main objective of this study was to analyze morphological and genealogical differences between Lusitano horses (LPB) participating at international events and those ranked by FEI, considering pedigree information. For this study, 324 LPB participating in dressage competitions were analyzed. Thirty-two were ranked at FEI. The pedigree was reconstructed up to 1148 animals. For analyses, the complete pedigree (CP) and 2 subpopulations were used: PARTIC for animals participating in FEI competitions and RANK for animals ranked by FEI. Ten morphological parameters, obtained during the breeding process, were analyzed. A multivariable analysis was developed, with sex, age and sex*age interaction as factors and morphological parameters as the outcome variables. For variables showing statistically significant differences, Least Square Means and Tukey post-hoc tests were performed. Furthermore, the 10 most influential founders were calculated for each population studied and their morphological parameters were compared with the rest of the pedigree's, using a T-Test for independent samples. In general, the CP showed the highest mean values for all morphological parameters, except for "Back", "Croup" and "Height", suggesting an evolution in the morphological selection. Regarding the factors studied, a sexual dimorphism was found, with oldest males scored the highest for most morphological parameters. Finally, different founder lines were found in the RANK population, suggesting different selection trends. Thus, LPB breed standards should reconcile with performance parameters to improve genetic progress.

Stress level effects on sport performance during trotting races in Spanish Trotter Horses.

The stress level is suggested to have a negative effect on horses during equestrian competitions, specifically in trotter racing. The main objectives of this study were to measure stress levels in Spanish Trotter Horse races with a reliable non-invasive method, and determining the threshold level of stress that leads to the best performance results and also shows when the stress perceived by the horse becomes distress. One hundred and thirty individuals were evaluated, measuring their performance (based on racing time per kilometre (TPK)) and their stress (based on eye temperature, assessed with infrared thermography, and heart rate) in different competitions. Eye temperature and heart rate measurements were collected 2h before the race and immediately following the race, and the increases of eye temperature (∆ET) and heart rate were estimated. ∆ET and eye temperature before the race showed significant differences related to the performance level after a GLM analysis. The segmented regression analysis indicated that when the animal was more stressed before the race than just after finishing it (∆ET<0), it showed the poorest competition results, and from the breakpoint (reached at ∆ET=-0.97%), horse's performance started to improve. When comparing eye temperature variables and TPK with a response surface plot, TPK was optimum (77.27s) when the eye temperature before the race and ∆ET reached values of 37.61°C and 7.57%, respectively. Therefore, the stress levels of the horse before the race influence its competition results, and ∆ET during competitions reaching a threshold point is related to an improvement in performance results.