Maria do Mar Oom

Social relationships in a herd of Sorraia horses: Part I. Correlates of social dominance and contexts of aggression

Factors related to dominance rank and the functions of aggression were studied in a herd of Sorraia horses, Equus caballus, under extensive management. Subjects were 10 adult mares 5-18 years old and a stallion introduced into the group for breeding. Dominance relationships among mares were clear, irrespective of rank difference, and remained stable after introduction of the stallion. The dominance hierarchy was significantly linear and rank was positively correlated with age and total aggressiveness. Higher-ranking mares received lower frequency and intensity of agonistic interactions. Nevertheless, higher-ranking dominants were not more likely to elicit submission from their subordinates than lower-ranking dominants. Neither close-ranking mares nor mares with less clear dominance relationships were more aggressive towards each other. Agonistic interactions seemed to be used more importantly in regulation of space than to obtain access to food or to reassert dominance relationships. Contexts of aggression were related to mare rank. The results suggest that dominance relationships based on age as a conventional criterion were established to reduce aggressiveness in a herd where the costs of aggression are likely to outweigh the benefits.

European Domestic Horses Originated in Two Holocene Refugia

The role of European wild horses in horse domestication is poorly understood. While the fossil record for wild horses in Europe prior to horse domestication is scarce, there have been suggestions that wild populations from various European regions might have contributed to the gene pool of domestic horses. To distinguish between regions where domestic populations are mainly descended from local wild stock and those where horses were largely imported, we investigated patterns of genetic diversity in 24 European horse breeds typed at 12 microsatellite loci. The distribution of high levels of genetic diversity in Europe coincides with the distribution of predominantly open landscapes prior to domestication, as suggested by simulation-based vegetation reconstructions, with breeds from Iberia and the Caspian Sea region having significantly higher genetic diversity than breeds from central Europe and the UK, which were largely forested at the time the first domestic horses appear there. Our results suggest that not only the Eastern steppes, but also the Iberian Peninsula provided refugia for wild horses in the Holocene, and that the genetic contribution of these wild populations to local domestic stock may have been considerable. In contrast, the consistently low levels of diversity in central Europe and the UK suggest that domestic horses in these regions largely derive from horses that were imported from the Eastern refugium, the Iberian refugium, or both.

Social relationships in a herd of Sorraia horses: Part II. Factors affecting affiliative relationships and sexual behaviours

The influence of age, dominance rank, kinship and aggressiveness over affiliative relationships and sexual behaviours were analysed in a herd of Sorraia horses, Equus caballus, kept under extensive management. Subjects were 10 adult mares 5-18 years old that had known each other since birth, and a stallion introduced into the group for breeding for the first time. Kinship coefficient and dominance rank were the most important factors affecting affiliative relationships. Bonds were reciprocal and stronger among mares with higher kinship. Mares spent more time in proximity to close-ranking and lower-ranking females. Mares with stronger affiliative relationships or higher relatedness were not less aggressive towards each other. Affiliative relationships between the stallion and the mares were not reciprocal: lower-ranking mares formed stronger bonds with the stallion but he preferred the less genetically related mares for proximity. However, the stallion was involved in sexual behaviours more frequently with the mares that were more genetically related to him. These results suggest that kinship beyond close relatives may affect affiliative relationships both among familiar and among unfamiliar horses. However, the influence of kinship does not imply that horses possess a kin recognition system and alternative explanations are discussed.

Microsatellites in Portuguese autochthonous horse breeds: usefulness for parentage testing

The use of DNA technology for parentage testing is increasing every day. Most laboratories have improved their exclusion probabilities (PE) by the addition of DNA microsatellite loci to standard blood-typing results. The efficacy of each locus depends on the number of alleles detected and their frequencies in the breeds tested. Here we analyzed the usefulness of six microsatellites for routine parentage testing in three Portuguese autochthonous horse breeds: Lusitano, Sorraia and Garrano. The DNA loci analyzed - ASB2, HMS3, HMS7, HTG4, HTG10, and VHL20 - were chosen based upon the polymorphism detected in other breeds with Iberian horse influence. The estimated probability of exclusion of wrongly named parents (PE) was high, with values ranging from 88.5% to 99.6%.

First epidemiological data on pathogenic leptospires isolated on the Azorean islands

Insectivores (Erinaceus europaeus) and rodents (Rattus rattus, R. norvegicus and Mus musculus) from different islands of the Azores Archipelago were found to carry three distinct Leptospira interrogans (s.l.) serovars (copenhageni, icterohaemorrhagiae and ballum) which have never been previously investigated there. The house mouse and the black rat were the major Leptospira reservoirs showing isolation rates ranging from 0% for both species (in Graciosa) to 88% and 33%, respectively (in São Miguel). This study also showed that the majority of the animals with positive kidney cultures exhibited specific agglutinins against the isolated strains of Leptospira. The observed isolation rates in the different islands, with a very interesting island variation in prevalence, suggest that small mammals, serving as sylvatic reservoirs of pathogenic leptospires, may represent an important risk to the health of humans and livestock, particularly in the islands of Terceira and São Miguel.

Genetic Structure of an Endangered Portuguese Semiferal Pony Breed, the Garrano

The present study intends to survey the genetic variability of an endangered semiferal Portuguese native pony breed, the Garrano. Thirteen microsatellite markers were examined in 277 animals born in 1998, belonging to eight subpopulations corresponding to eight northern Portuguese geographic regions. Mean heterozygosity (Ho) in the Garrano breed was 0.732, ranging from 0.531 to 0.857 across subpopulations. Allelic frequencies and diversity differed significantly between regions, suggesting the existence of genetic differentiation within the breed confirmed by the population differentiation estimator FST. Allele sharing genetic distance (Dps) was used to determine the relationship between the analyzed subpopulations, some of which are diverging significantly from the others. Relationships among six Iberian horse breeds (including the Garrano) were assessed through the restricted maximum likelihood method, which clusters the Garrano with another Celtic pony, the Spanish Asturcon, traditionally bred in geographical continuity with the Garrano. Results reveal a statistically significant deficit of heterozygotes within the Garrano breed (FIT = 0.031, p < 0.05). Regular monitoring should therefore be implemented so that the effect of genetic drift within subpopulations, enhanced by inbreeding, may be successfully minimized.

Differential effects of dietary protein on early life-history and morphological traits in natterjack toad (Epidalea calamita) tadpoles reared in captivity.

The production of high quality amphibian larvae through optimal diets is a critical component of amphibian conservation breeding programs. Larval period, survival, body weight and total length are frequently used as metrics of adequate nutrition. However, the effects of nutrition on tadpole and metamorph morphology are rarely tested in detail. In the present study, we analyzed the most common metrics and six other larval and post-metamorphic morphological traits in natterjack toads (Epidalea calamita) fed with three different commercial fish diets, varying in protein content (32.0%, 38.3%, and 46.2%). Our results suggest that early life-history (tadpole growth, development, and survival) and morphological traits of E. calamita tadpoles are differentially affected by the percentage of dietary protein. As protein content increased, tadpoles exhibited larger bodies along with shorter tail fins; however, with no significant differences in total length. Larval period was similar across treatments but mortality was lower in high-protein diet. At high-protein diets the metamorphs revealed significantly longer bodies, and wider heads and hind legs, but there was no significant difference in the average weight across all dietary treatments. Based on our results, feed containing 46.2% protein promotes growth, development and survival of E. calamita tadpoles better than either of the other two feeds tested. The use of other body measures beyond weight, tadpole total length, and snout-vent length in studies of amphibian nutrition in captivity may assist the selection of appropriate diets to optimize tadpole survival and metamorph fitness.

Genetic variation in BoLA microsatellite loci in Portuguese cattle breeds

Major histocompatibility complex (MHC) typing based on microsatellites can be a valuable approach to understanding the selective processes occurring at linked or physically close MHC genes and can provide important information on variability and relationships of populations. Using microsatellites within or in close proximity with bovine lymphocyte antigen (BoLA) genes, we investigated the polymorphisms in the bovine MHC, known as the BoLA, in eight Portuguese cattle breeds. Additional data from non-BoLA microsatellite loci were also used to compare the variability between these regions. Diversity was higher in BoLA than in non-BoLA microsatellites, as could be observed by the number of alleles, allelic richness and observed heterozygosity. Brava de Lide, a breed selected for aggressiveness and nobility, presented the lowest values of observed heterozygosity and allelic richness in both markers. Results from neutrality tests showed few statistically significant differences between the observed Hardy-Weinberg homozygosity (F) and the expected homozygosity (F(E)), indicating the apparent neutrality of the BoLA microsatellites within the analysed breeds. Nevertheless, we detected a trend of lower values of observed homozygosity compared with the expected one. We also detected some differences in the levels of allelic variability among the four BoLA microsatellites. Our data showed a higher number of alleles at the BoLA-DRB3 locus than at the BoLA-DRBP1 locus. These differences could be related to their physical position in the chromosome and may reflect functional requirements for diversity.

In vivo fertilizing ability of stallion spermatozoa processed by single layer centrifugation with Androcoll-E™

A colloid with a species specific silane-coated, silica-based formulation, optimized for stallion (Androcoll-E™), enables a better sub-population of spermatozoa to be selected from stallion ejaculates. However, such a practice has not been critically evaluated in stallions with fertility problems. In this study we evaluate whether single-layer centrifugation (SLC) through Androcoll-E™ could be used to enhance fertility rates in a subfertile stallion. Ejaculates were obtained from two different stallions, one Lusitano (fertile) and one Sorraia (subfertile), with distinct sperm characteristics and fertility. Motility, morphology, plasma membrane structural (eosin-nigrosin) and functional integrity (HOS test), mitochondrial functionality (Δψm; JC-1) and longevity (motility after 72 h cooling) after centrifugation in Androcoll-E™, as well as pregnancy rates obtained after artificial insemination (AI), with and without (control group) SLC-treated sperm were assessed. The effect of SLC on sperm characteristics, and fertility results were evaluated by ANOVA and Fisher procedures, respectively. Our results showed that SLC-selected sperm did not differ from the raw semen in terms of viability, morphology, response to hypo-osmotic conditions (HOS test) and mitochondrial membrane potential (↑ΔΨmit; JC-1). Sperm motility in cooled samples was not improved by SLC treatment. Our data show that SLC through Androcoll-E™ has no effect on pregnancy rates in the stallions used in this trial.

Genetic diversity of the semi-feral Marismeño horse breed assessed with microsatellites

Abstract Marismeño horses originated from primitive horses living around the marshes of the Guadalquivir River in Southern Spain. Throughout their evolution, they have experienced crosses with other breeds, first with horses from North Africa and thereafter with other horses. However, they have not lost their ability to adapt to the demanding marsh environment. Recently, a studbook of the breed was established, and the Breeders Association started a conservation programme. To study the relationship of the Marismeño with other breeds, a microsatellite analysis was developed, which included other ancient Southern Iberian horse populations, such as the Sorraia and Retuertas breeds. Candidates of recent crossbreeding with Marismeño horses, such as the Hispano-Arabian and the Spanish Purebred, were studied, and the Thoroughbred and the Arabian breed were used as international references. The results indicated that the Marismeño horse population maintains a great genetic diversity. Despite recent crossbreeding, the fixation index and the Hardy-Weinberg equilibrium analysis disclosed a certain homogeneity degree. A dendrogram was built using the obtained genetic distances, and clustering was performed with the software STRUCTURE, and the results reflected the genetic differentiation of the Marismeño horse from the other autochthonous Iberian breeds, although the Marismeño population has maintained a tight relationship with the Spanish Purebred. Remarkably, some relatedness between the Marismeño and the Barb horse breeds could be observed and was most likely derived from an ancient gene flow between the horses of the Iberian Peninsula and North Africa.