Aspects of breeding stallion management with specific focus on animal welfare

Risk prevention is often counterproductive to stallions’ living conditions when assessed under welfare aspects. In the wild, stallions live in social groups, but under domestic conditions, the majority of breeding stallions live in individual boxes with limited social contact. This stimulates aggressiveness and the incidence of stereotypic behavior. While racehorse stallions start their breeding career after having finished their performance career, riding horse stallions are often simultaneously used for breeding and performance. Training, performance, and the associated stress are unlikely to impair semen characteristics, but performing stallions may benefit from more opportunities for social contact. With regard to accommodation of stallions in single boxes, changes in the construction of the partition between them may help to improve social contact from merely visual to much more physical. This will help to reduce social isolation but requires careful observation if neighbors tend to either sympathize or fight with each other. Careful organization of the barn is thus of great importance. Under certain conditions, even keeping adult stallions in groups on spacious pastures is possible. Interestingly, the frequency of agonistic interactions usually decreases quickly and remains low after successful group integration. General changes in the husbandry of young stallions and at their transfer into the future career may help to produce stallions with better social skills and facilitate accommodation under improved welfare conditions

Reduced bacterial load in stallion semen by modified single layer centrifugation or sperm washing

The presence of bacteria poses a significant challenge to the quality of stallion semen used in artificial insemination. The bacterial content of insemination doses arises from various sources, such as the healthy stallion, environment, and collection equipment, and is implicated in fertility problems as well as reduced sperm quality during storage. The conventional approach of adding antibiotics to semen extenders raises concerns about antimicrobial resistance and potential negative effects on sperm characteristics, and may not be effective in inhibiting all bacteria. The objective of this study was to determine whether an innovative alternative to antibiotic usage – centrifugation through a single layer of a low density colloid (SLC) – could reduce the bacterial load in stallion semen, and to compare sperm characteristics in samples arising from this procedure, or simple extension of the ejaculate in semen extender, or from sperm washing, i.e. adding extender and then centrifuging the sample to allow the removal of most of the seminal plasma and extender. Eighteen semen samples were collected from six stallions. The semen samples were split and extended prior to washing or SLC, or received no further treatment other than extension. After preparation aliquots from each type of sample were sent for bacteriological examination; the remaining samples were stored for up to 72 h, with daily checks on sperm quality. The low density colloid SLC outperformed sperm washing or extension for bacterial reduction, effectively removing several bacterial species. The bacterial load in the samples was as follows: extended semen, 16 ± 6.7 × 105 ; washed, 5.8 ± 2.0 × 105 ; SLC, 2.3 ± 0.88 × 105 ,

Season does not have a deleterious effect on proportions of stallion seminal plasma proteins

The mechanism by which the content of the major groups of seminal plasma proteins in stallion semen changes between the breeding and non-breeding seasons remains unknown. Here, we investigated the proportions of non-heparinbinding, phosphorylcholine-binding, and heparin-binding proteins in seminal plasma with the aim of relating them to sperm quality and testosterone levels in good and bad freezer stallions. Only minor variations in the major protein groups were found between the breeding and non-breeding seasons. In the non-breeding season, a higher content of a subset of nonheparin binding proteins as well as of heparin-binding proteins was found. Analysis of semen characteristics revealed a somewhat contrasting picture. While only minor variations in sperm kinematics and sperm morphology were found between seasons, the flow-cytometric measurements of mitochondrial membrane potential and also, to some extent, reactive oxygen species production indicated lower sperm quality in the breeding season. Chromatin integrity and testosterone levels were unchanged between seasons. The results suggest that stallion ejaculates could be used year-round for freezing, since only minor differences in protein composition exist between the breeding and non-breeding seasons, as well as between good and bad freezers. In addition, sperm quality is not impaired during the non-breeding season

Sexual differentiation and primordial germ cell distribution in the early horse fetus

It was the aim of this study to characterize the development of the gonads and genital ducts in the equine fetus around the time of sexual differentiation. This included the identification and localization of the primordial germ cell population. Equine fetuses between 45 and 60 days of gestation were evaluated using a combination of micro-computed tomography scanning, immunohistochemistry, and multiplex immunofluorescence. Fetal gonads increased in size 23-fold from 45 to 60 days of gestation, and an even greater increase was observed in the metanephros volume. Signs of mesonephros atrophy were detected during this time. Tubular structures of the fetal testes were present from day 50 onwards, whereas cell clusters dominated in the fetal ovary. The genital ducts were well-differentiated and presented a lumen in all samples. No sign of mesonephric or paramesonephric duct degeneration was detected. Expression of AMH was strong in the fetal testes but absent in ovaries. Irrespective of sex, primordial germ cells selectively expressed LIN28. Migration of primordial germ cells from the mesonephros to the gonad was detected at 45 days, but not at 60 days of development. Their number and distribution within the gonad were influenced (p < 0.05) by fetal sex. Most primordial germ cells (86.8 ± 3.2% in females and 84.6 ± 4.7% in males) were characterized as pluripotent according to co-localization with CD117. However, only a very small percentage of primordial germ cells were proliferating (7.5 ± 1.7% in females and 3.2 ± 1.2% in males) based on co-localization with Ki67. It can be concluded that gonadal sexual differentiation in the horse occurs asynchronously with regard to sex but already before 45 days of gestation.Fil: Scarlet, Dragos. University of Veterinary Medicine Vienna; Suiza. Universitat Zurich; SuizaFil: Handschuh, Stephan. University of Veterinary Medicine Vienna; SuizaFil: Reichart, Ursula. University of Veterinary Medicine Vienna; SuizaFil: Podico, Giorgia. University of Illinois. Urbana - Champaign; Estados UnidosFil: Ellerbrock, Robyn E.. University of Illinois. Urbana - Champaign; Estados UnidosFil: Demyda Peyrás, Sebastián. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Canisso, Igor F.. University of Illinois. Urbana - Champaign; Estados UnidosFil: Walter, Ingrid. University of Veterinary Medicine Vienna; SuizaFil: Aurich, Christine. University of Veterinary Medicine Vienna; Suiz

Efficiency of Semen Cryopreservation in Stallions

Differences in the cryotolerance of spermatozoa exist among stallions, but it remains to be determined to what extent such differences are affected by breed. In this study, post-thaw semen quality in stallions presented for semen cryopreservation was analysed retrospectively (1012 ejaculates from 134 stallions of 5 breeds). The percentage of frozen&ndash;thawed ejaculates acceptable for artificial insemination (AI) and the number of insemination doses per cryopreserved ejaculate was calculated. Logistic regression analysis revealed sperm motility in raw semen as the most important explanatory variable for the percentage of cryopreserved ejaculates with a post-thaw quality acceptable for AI. Of the other variables included into the model, stallion age was the most important parameter with more acceptable ejaculates in younger than in older stallions. Logistic regression also showed more acceptable frozen&ndash;thawed ejaculates in Arab stallions versus Warmbloods, Quarter Horses and Icelandic horses. The analysis thus demonstrates differences in the percentage of acceptable cryopreserved ejaculates among horse breeds. Season was a less relevant explanatory variable for percentage of acceptable cryopreserved ejaculates. Logistic regression revealed total sperm count as the most important variable determining the number of cryopreserved semen doses obtained per acceptable ejaculate. In conclusion, logistic regression analysis revealed stallion age and breed as explanatory variables for the percentage of cryopreserved ejaculates acceptable for AI

Differences in Endocrine and Cardiac Changes in Mares and Her Fetus before, during, and after Parturition in Horses of Different Size

Equine fetomaternal monitoring is based on endocrine and cardiac parameters which may differ among small, medium-size, and full-size horses. Therefore, Shetland (n = 6), Haflinger (n = 8), and Warmblood pregnancies (n = 9) were studied during late gestation and at foaling. Weight of mares, foals and placenta, plasma progestin and cortisol concentration, heart rate and heart rate variability (HRV) were determined. Foal weight always approximated 10% of mare weight but relative placenta weight was highest in full-size mares (p &lt; 0.05). Progestin (p &lt; 0.001) and cortisol (p &lt; 0.05) concentration was highest in full-size mares. Progestin concentration decreased towards parturition (p &lt; 0.001) while cortisol concentration increased (p &lt; 0.01). Maternal heart rate increased before foaling with the most pronounced increase in small mares (p &lt; 0.001). The HRV increased during foaling and decreased when delivery was completed (p &lt; 0.001). Changes were most pronounced in full-size mares (p &lt; 0.001). Atrio-ventricular blocks regularly occurred in parturient full-size mares but only occasionally in medium-size and small mares (time p &lt; 0.05, time &times; group p &lt; 0.05). This may reflect breed differences in cardiovascular efficiency. Fetal heart rate decreased towards birth (p &lt; 0.001) with the most pronounced decrease in full-size horses (p &lt; 0.01). Fetal HRV showed no consistent changes before birth but increased when the foal was born (p &lt; 0.001), this increase being most pronounced in full-size foals (p &lt; 0.05). In conclusion, this study demonstrates both similarities and differences in peripartum endocrine and cardiac changes in horses of different size