Rams Of Breeds Research Articles

Induction of fertile estrus without the use of steroid hormones in seasonally anestrous Suffolk ewes.

ObjectiveTo evaluate the efficacy of treatments based on gonadotrophin-releasing hormone (GnRH), GnRH-prostaglandin F2α (PGF2α), and/or intense exposure to novel rams to induce fertile estrus without the use of steroid hormones in seasonally anestrous Suffolk ewes.MethodsIn the first experiment, ewes were treated with one injection of GnRH, two injections of GnRH administered 7 days apart, or a sequence of GnRH-PGF2α-GnRH (GPG). In the second experiment anestrous ewes were exposed, for 36 days starting on the day of weaning, to groups of four rams of three different breeds that were alternated every day. Besides exposure to the male effect (ME), the ewes were injected with saline solution (ME group, n = 20), with GnRH (ME-GnRH group, n = 20) or with a sequence of GnRH-PGF2α-GnRH (ME-GPG group, n = 20). The rams used for male-effect were fitted with aprons to prevent mating, and ewes detected in estrus were bred to selected fertile rams. Ovarian activity was monitored by progesterone determinations in both experiments.ResultsIn the first experiment sustained induction of ovarian activity was not achieved and no ewe was detected in estrus. In the second experiment induction of sustained ovarian activity was achieved in all groups. Most of the ewes were detected in estrus, 76.7% of the ewes were mated during a 36-d breeding period and 71.7% of all the ewes became pregnant during that period. No significant differences between groups were found for any of these variables. However, estrus detection efficiency was higher in the ME-GnRH group than in the ME group (p<0.05).ConclusionAn intense male-effect, that included the continuous presence and frequent alternation of several rams of different breeds, was sufficient to induce ovarian activity and fertile estrus in Suffolk ewes during the period of deep anestrus without the use of hormones, although addition of GnRH improved the efficiency of estrus detection.

Commodity properties of sheepskins and skin histological structure in young rams of the kalmyk fat-rumped breed and crossbreds (1/2 kalmyk fat-rumped × 1/2 dorper)

They have been studied the commercial properties of sheepskins and the histological structure of the Kalmyk breed young rams skin and crossbreds (1/2 Kalmyk fat-rumped breed × 1/2 Dorper). It was found out that the weight of fresh sheepskins in the sheep young of the 1st group was larger than that in herd mates of the 2nd group by 1.0 kg, or 34.5% (P&gt; 0.999). A large live weight influenced the large area of the skin in the second group of young animals, and the length of the wool in the experimental group, which turned out to be shorter, influenced its smaller sheepskin weight. The crossed animals got on the basis of the crossing of the Kalmyk fat-rumped ewes with the Dorper breed rams have the best quality indices of sheepskins and the best histological structure of the skin. In hybrid animals, a more elastic, firmer and less thick skin is 14.52%, due to a greater epidermal thickness of 27.7% and a denser reticular layer of 13.7%. The wool cover (ratio SF / PF) in crossbred young rams is 10.47% thicker in comparison with herd mates, at white color of wool, which corresponds to the technological requirements for the production of high-quality sheepskins.&#x0D;

Breeding Objective, Breeding Practices and Selection Criteria of Indigenous Sheep in Western Amhara, Ethiopia

The purpose of this research was to generate organized information on breeding objectives, breeding practices and choice criteria of farmers in Farta, Lay Gayint and Sekela districts. A sum of 180 households was selected to survey questionnaires in selected districts, Semi structured questioner and group discussions were used as information sources. The average separation of the Statistical Analysis System was used to analyze the flock size and structure in the three districts. An index was calculated to supply an overall ranking of categorical variables. The average flock per house holding the study districts was 8.8±0.05 heads. For source of income (0.45), home use (0.28), saving (0.20), and manure (0.04) were the reasons of sheep keeping. The uncontrolled mating system was practiced by most (72.6 %) of households. In the study districts 37.7 % of farmers received their own breeding rams while the rest farmers shared with their neighbors. Appearance (0.38), growth rate (0.34), color (0.13), pedigree (0.10) and tail type and size (0.10) were the sheep owner’s standards for breeding ram, while the appearance (0.29), coat color (0.18), lamb growth (0.17), lambing interval (0.12), age at first lambing (0.09) and lamb survival (0.08) where the farmers' selection criteria for breeding ewes. Going through a breed improvement program considering the farmers’ production objectives and existing breeding practices is important. Nevertheless, designing alternative breeding strategies to key out the optimal number of traits to be considered and size of flocks to be mixed is crucial before setting up a breeding plan.

Екстер’єр та інтенсивність росту помісних ярок F1, одержаних від схрещування маток цигайської породи з баранами м’ясних порід

Екстер’єр та інтенсивність росту помісних ярок F1, одержаних від схрещування маток цигайської породи з баранами м’ясних порід

Heritability of ram mating success in multi-sire breeding situations

Multi-sire mating of a mob of ewes is commonly used in commercial sheep production systems. However, ram mating success (defined as the number of lambs sired by an individual) can vary between rams in the mating group. If this trait was repeatable and heritable, selection of rams capable of siring larger numbers of lambs could reduce the number of rams required for mating and ultimately lead to increased genetic gain. However, genetic correlations with other productive traits, such as growth and female fertility, could influence the potential for ram mating success to be used as a selection trait. In order to investigate this trait, parentage records (including accuracy of sire assignment) from 15 commercial ram breeding flocks of various breeds were utilised to examine the repeatability and heritability of ram mating success in multi-sire mating groups. In addition, genetic and phenotypic correlations with growth and female fertility traits were estimated using ASReml. The final model used for the ram mating success traits included age of the ram and mating group as fixed effects. Older rams (3+years old) had 15% to 20% greater mating success than younger rams (1 or 2 years of age). Increasing the stringency of the criteria for inclusion of both an individual lamb, based on accuracy of sire assignment, or a whole mating group, based on how many lambs had an assigned sire, increased repeatability and heritability estimates of the ram mating success traits examined. With the most stringent criteria employed, where assignment of sire accuracy was >0.95 and the total number of lambs in the progeny group that failed to have a sire assigned was<0.05, repeatability and heritability for loge(number of lambs) was 0.40±0.09 and 0.26±0.12, respectively. For proportion of lambs sired, repeatability and heritability were both 0.30±0.09. The two ram mating traits (loge(nlamb) and proportion) were highly correlated, both phenotypically and genetically (0.88±0.01 and 0.94±0.06, respectively). Both phenotypic and genetic correlations between ram mating success and growth and other female fertility traits were low and non-significant. In conclusion, there is scope to select rams capable of producing high numbers of progeny and thus increase selection pressure on rams to increase genetic gain.

WPSII-1 Environmental Effects of High Temperatures on Sperm of Rams of Different Breeds.

WPSII-1 Environmental Effects of High Temperatures on Sperm of Rams of Different Breeds.

THE USE OF IMMUNOGENIC MARKERS IN THE SELECTION OF SHEEP OF ZABAIKALSKAYA BREED

The article presents the results of immunogenic certification of fine-fleece sheep of Zabaikalskaya breed of the Khangil type, bred by a sophisticated reproductive cross-breeding method with Australian and Manych Merino breeds. The animals are adapted to a year-round grazing in harsh climatic conditions. The study was carried out in the pedigree plant of Trans-Baikal Territory. The immunogenic certification of animals was carried out in the laboratory of the immunogenic appraisal by six systems of blood groups including 14 antigenic factors. The blood group characteristics of the young were determined depending on their origin. Progeny of Zabaikalskaya stud ram breed of Khangil type is characterized by the highest frequency of occurrence of antigenic factors Aa, Bd, Bi, Bg, Cb, Ma, Mb, R. Given this, the progeny that was bred revealed similarities in the antigenic factors Bd, Bi, Ca, Cb, Ma and R, whereas the discrepancy was established for the antigens Aa, Ab, Bb, Be, Bg, Mb and O. The degree of the genetic similarity and genetic distance between animals within the breed amounted to 0.920 and 0.083 respectively. It is probable that high incidence of antigens Ma, Aa and Bd with the sheep of Zabaikalskaya breed of Khangil type corresponds to their mutton-wool production type. The work demonstrates necessity of the use of genetic markers in the breeding process and in the objective assessment of the degree of genetic similarity and genetic distance between animals of different origin within one breed.

Caracterização da população de bactérias intestinais de quatro relevantes espécies de animais de produção

Objetivou-se caracterizar a população de Enterobacteriacea do intestino de animais de interesse zootécnico. O contingente amostral do presente estudo foi composto por 50 animais, sendo cinco de cada grupo: vacas em lactação e bezerros; matrizes ovinas, borregos, reprodutores ovinos; cavalos adultos; porcas gestantes, porcas lactantes leitões em fase de creche e terminação. As amostras de fezes foram coletadas da ampola retal dos animais, homogeneizadas e diluídas em solução salina. Posteriormente foram inoculadas alíquotas de 100 microlitros (μL) das diluições em placas estéreis contendo ágar Mac Conkey. Após crescimento bacteriano, as colônias foram classificadas em Lac+ Lac- e quantificadas quanto a esses grupos e quanto ao número total de unidades formadoras de colônias (UFC/grama de fezes). Para a identificação dos gêneros bacterianos foi realizado o reisolamento e após o crescimento, cada bactéria foi inoculada em tubos contendo meio Rugai e Araújo, modificado por Pessoa e Silva. Após análises, observou-se que os borregos apresentaram maior concentração de enterobactérias (7,9 x 107 UFC/g de fezes) e os leitões em creche apresentaram uma menor população (4,20 x 106 UFC/g de fezes). A identificação dos gêneros indicou maior ocorrência de E coli. A população de enterobactérias é influenciada pela categoria e espécie animal, podendo ser justificadas pelas diferenças fisiológicas, do ambiente de criação e da alimentação de cada grupo animal.

English

This study was conducted with the aim to generate organized information on traditional breeding practices and selection criteria for indigenous sheep types in three districts of central zone of Tigray, North Ethiopia. A total of 180 households were randomly sampled for the interview. A semi-structured questionnaire and group discussion were further used to gather information on sheep breeding practices and selection criteria. The primary reason for keeping sheep in Tanqua-Abergelle and Kola-Tembien districts were manure as sources of fertilizer, while in Adwa district cash income. In all the study districts the flock structure were dominated by breeding ewes and they accounted 38.5, 35.9 and 38.7% in Tanqua-Abergelle, Kola-Tembien and Adwa districts, respectively. Sexual maturity of female for Tanqua-Abergelle, Kola-Tembien and Adwa districts were 9.16±0.82, 8.75±1.34, and 8.86±1.04 months, respectively and for male 7.43±0.76, 6.67±0.91, and 6.64±0.95 months, respectively. Tail type and body size in Tanqua-Abergelle and Kola-Tembien were the most frequently reported traits in selecting breeding ram and ewes, while tail type and coat colour in Adwa district. Based on the present result on sheep indigenous breeding practices one may develop selection criteria and productivity schemes of the local sheep in the study districts. Key words: Adwa, breeding practice, indigenous selection criteria, Kola-Tembien, phenotypes, Tanqua-Abergelle.

Динамика роста и откормочные качества баранчиков грозненской породы и помесей различной доли кровности

Динамика роста и откормочные качества баранчиков грозненской породы и помесей различной доли кровности

Flock composition, breeding strategies and farmers\u2019 traits of interest evaluation of Wollo highland sheep and their F1 crosses

BackgroundSheep production is a major component of the livestock sector in Ethiopia. The country owing to the large population of 30.70 million estimated numbers of sheep in the country and out of which about 72.14% are females, and 27.86% are males with diverse genetic resources. The real value of indigenous breeds was often under-estimated mostly due to their poor appearance and relatively low productivity. Developing countries in most cases opt for exotic breeds to increase animal productivity through crossbreeding or breed substitution without properly investigating the production potential of the indigenous breeds. The main objective of the research was to identify sheep flock composition and structure, farmers’ traits of interest and breeding objective of Wollo highland sheep, and their F1 crossbreed progenies.ResultsSmallholder farmers’ flock synthesized from breeding ewes, breeding rams, pre-weaned ewe lambs, pre-weaned ram lambs, unproductive ewes, castrated and fattened rams, with the percentage coverage of 29.2, 13.3, 15.5, 16.5, 12.4, and 12.5%, respectively. The maximum number of flock size was 289.0 sheep per flock and higher in the third stratum. The off-take rate percentage of the three strata presented as 21.9% in 1st stratum, 12% in the 2nd stratum, and 16.4% in the 3rd stratum and higher off-take rate recorded in the first stratum. Sheep producer’s traits of interest ranked by growth rate (first), body size (second) and marketing value was third rank. Communal breeding (random mating), village based controlled breeding, mixed type and private ram controlled breeding practice were comprised of 39.7, 61.7, 52 and 71.3%, respectively. The percentages of ewes per flock composition were presented as 36.5, 27.1 and 25.5%, respectively in the 3rd stratum, 2nd stratum and 3rd stratum in the order of their importance’s.ConclusionGenetic improvement practices at smallholder sheep producers situation was showing promising outcome with indigenous Washera F1 crossbred lambs and which designated for weaning rate, body size, marketing age, age at first lambing, good temperament and large litter size in the order of their rank. The contemporary breeding practice tendency indicated that, reduced flock size to improve flock productivity via crossbreeding practices.

Effect of increasing levels of wasted date palm in concentrate diet on reproductive performance of Ouled Djellal breeding rams during flushing period.

Aim:The aim of the study was to assess the effect of two levels of wasted date (WD) by replacing commercial concentrate on the reproductive performance of Ouled Djellal (OD) rams.Materials and Methods:Eighteen mature (2-year-old) OD rams were equally allocated to three groups and fed during 11 weeks with one of three different experimental diets, that contained 0% (0 WD), 50% (50 WD), or 75% (75 WD) of WDs in concentrate diet. Live body weight (LBW), body condition scoring (BCS), scrotal circumference (SC), testicular weight (TW), sperm production and quality, plasma testosterone concentration (T), and sexual behavior (reaction time and number of mounts with ejaculation) were regularly recorded from every ram.Results:LBW, SC, and TW changed significantly among diet groups and during the experimental period (p<0.001), the highest averages were recorded in (0 WD) group. LBW, BCS, SC, TW, semen volume, and percentage of the positive hypo-osmotic swelling test were (p<0.001) positively influenced by flushing period. Nevertheless, sperm concentration showed a significant (p<0.001) decrease at day 30, followed by a return to the initial values afterward. There were no differences (p>0.05) between diet groups for plasma testosterone concentration and semen attributes, except that (50 WD) group expressed the lowest overall value of semen concentration. Furthermore, neither time nor diet affected (p>0.05) sperm motility and reproductive behavior parameters.Conclusions:It is possible to introduce WD as unconventional local feeding resources in flushing diet of breeding rams without disturbing their reproductive performance.

Indigenous Knowledge in Sheep and Goat Farming Systems in Tamil Nadu, India

The present study was conducted in 2008 to document the indigenous knowledge prevalent in sheep and goat farming systems in Tamil Nadu, India. Fifty sheep farmers in Tirunelveli district and fifty goat farmers in Erode district were selected by proportionate random sampling method and the data were collected through an interview schedule and analysed and ranked for getting inferences. The results revealed that in sheep farming system, the traditional practices such as lamb hut (100%), washing the sheep in ponds for tick removal (100%), selecting good breeding rams (96%), sheep penning (94%), and twinning (76%) were known to sheep farmers. In goat farming system, rearing bucks for religious purpose (100%), kid house (100%), tethering (96%), and locally made shelter (84%) were known to goat farmers. A close look at the indigenous practices in sheep and goat farming systems indicates the area-specific nature of these practices/beliefs.

English

The spermiogram and biometrical observations on the testes and epididymis of 20 adult Uda rams were investigated. The study was aimed at providing information on the reproductive potentials of Uda rams in Ibadan, and thus improved evaluation of breeding soundness in rams. The average age of the rams was 26.40±7.39 months, and their mean body weight was 39.80±3.00kg. The lengths of the right testes (14.34±1.24) and epididymis (20.50±2.94) as well as the circumference of the right testes (19.08±2.46) were significantly higher than their left counterparts (12.86±2.49, 18.50±3.36 and 16.40±4.35, respectively). The longer testes had a higher number of sperm cell abnormalities (23.43±4.97) compared to the shorter testes (15.03±6.91). Progressively, decreasing number of abnormalities was observed from the testes down the length of the epididymis from the head to the tail. The sperm cell abnormality that occurred most was the curved tail while the rudimentary tail was the least observed. The age was positively and significantly correlated with the body weight (r= 0.59, P<0.01) as well as most of the right testicular and epididymal parameters. The right testicular and epididymal volume was positively correlated with sperm motility of right caput epididymis (r= 0.82, P<0.05), and some other spermiogram parameters than the left which did not show any positive correlation. In conclusion, higher correlation observed between age and testicular measurements than with body weight implies that age is an important factor for selection of the Uda breed of ram. Key words: Testes, epididymis, semen, Uda, ram, Ibadan.

Modelling of strategies for genetic control of scrapie in sheep: The importance of population structure.

Scrapie is a transmissible spongiform encephalopathy in sheep and an example of a disease that may be controlled through breeding for disease resistance. Member states of the European Union have introduced strategies for breeding against scrapie based on the selection of genetically resistant breeding rams. An ambitious strategy adopted in The Netherlands consisted of selecting resistant rams for breeding throughout both breeding and production sectors. Mathematical modelling of the effect of a breeding program on the spreading capacity of scrapie in a national flock is needed for making assessments on how long a breeding strategy needs to be maintained to achieve disease control. Here we describe such a model applied to the Dutch situation, with the use of data on the genetic content of the Dutch sheep population as well as on scrapie occurrence in this population. We show that the time needed for obtaining scrapie control depends crucially on two parameters measuring sheep population structure: the between-flock heterogeneity in genotype frequencies, and the heterogeneity of mixing (contact rates) between sheep flocks. Estimating the first parameter from Dutch genetic survey data and assuming scenario values for the second one, enables model prediction of the time needed to achieve scrapie control in The Netherlands.

Seasonal variations in scrotal circumference and semen characteristics of Naimi and Najdi rams in Saudi Arabia

In the present study, the authors analysed the effects of seasonal variations on the scrotal circumference and semen characteristics in two ram breeds in Saudi Arabia, namely Naimi and Najdi. Five rams of each breed were used in this experiment. Scrotal circumference and semen characteristics were evaluated in each ram twice a month throughout the year. Significant differences were observed in the scrotal circumference between various seasons. The largest production of semen was recorded mainly in spring, whereas the lowest semen volume was produced in summer. The pH of the semen was slightly alkaline and significantly lower in autumn than in spring. Furthermore, the highest value of the total number of sperm per ejaculate was observed in spring for both breeds. The results indicated that mass motility increased significantly in autumn compared with winter, spring, and summer. Progressive motility was significantly lower during the months of summer and spring. However, no significant differences were recorded between autumn and winter. Hence, the presence of significant seasonal variations in semen quantity and quality of Naimi and Najdi rams suggests the viability of increased utilization of rams in spring and autumn for semen collection and reproductive practices. Keywords: Mass motility, progressive motility, semen volume, sperm concentration

Thermoregulation of male sheep of indigenous or exotic breeds in a tropical environment

Climate change has intensified the frequency of heat waves in the world, thereby exposing farm animals to stressful conditions. For better productive performance it is important to identify the most resilient genotypes. Thus, our objective was to evaluate the thermoregulatory responses of rams of tropical indigenous (Morada Nova and Santa Inês) and exotic breeds (Dorper and Texel), by monitoring the environmental and physiological indicators related to heat tolerance. The experiment was carried out in a tropical climate region (Cwa), in Brazil, for twelve months, which comprised spring, summer, autumn and winter. Thirty-three rams were divided into groups: Morada Nova (MN; n=8, red-coat), Santa Inês (SI; n=9, black-coat), Dorper (DO; n=8, white-coat) and Texel (TX; n=8, white-coat). The microclimatic variables were monitored, and the THI and BGHI comfort indices were calculated. Coat thickness and body surface temperatures were measured monthly, and serum triiodothyronine-T3 measurements and complete blood tests were performed. The physiological variables were evaluated every fifteen days and skin micro-biopsies were performed in the summer and winter for histological evaluation. During the warmer seasons, the THI and BGHI reached values that indicated thermal discomfort. TX showed higher coat thickness throughout the year, increased physiological variables related to thermolysis, and reduced T3 (P < 0.05). The internal temperature was permanently lower in the MN, SI and DO (P < 0.05). The body surface temperatures were affected by the coat characteristics and wool length. Hematological parameters varied in the seasons with the highest thermal conditions (P < 0.05). The MN showed larger sweat glands, while the area occupied by the sweat glands was higher in the SI. The DO showed higher hair density in the summer and winter (P < 0.05). The results indicated that the MN, SI and DO breeds overcome the thermal challenge more easily throughout the seasons due to specific adaptive morphological and physiological characteristics.

Single Nucleotide Polymorphisms of the Ovine ADRB3 Gene in Crossbred Australian Sheep Supplemented with Spirulina (Arthrospira platensis) Cyanobacterial Microalgae

The adrenergic-receptor beta3 (ADRB3) gene is an obesity gene that is involved in the regulation of energy balance and a variety of physiological functions by increasing lipolysis and thermogenesis. Spirulina (Arthrospira platensis) is a blue-green cyanobacterial alga containing 60-70% protein with an extensive history of human consumption, and more recently, inclusion in animal feeds. We had earlier demonstrated that low level oral supplementation by drenching prime lambs with 100 mL/head/day of 1g of Spirulina powder dissolved in 10 mL of water (10%wt:vol) increased live weight and body conformation measurements in Black Suffolk (BS) x Merino crossbred sheep. The hypothesis that genetics-nutrition interactions between sheep breeds with fewer mutations at the ADRB3 locus and an optimal Spirulina supplementation level will increase lean meat production was tested in the current study. Forty-eight crossbred Australian prime lambs sired by four rams of diverse breeds under the same pasture-based management conditions were subjected to a nine-week feeding trial with Spirulina, followed by genomic DNA extraction and single nucleotide polymorphism (SNP) analysis. Eleven SNPs in both the coding and noncoding regions of the ovine ADRB3 gene were detected. Nine of the SNPs were in exon I and two in the intron. Variations in SNP frequencies were highly significant (P <0.0001) between all sheep breeds. The maximum and minimum number of SNPs were found in purebred Merinos (4.83) and Black Suffolk x Merino (BS) crossbreds (1.67). In total, one indel and six transverse mutations were detected that resulted in six amino acid substitutions. BS crossbreds had the lowest frequency of mutation and amino acid substitutions in their population in agreement with our hypothesis. In conclusion, BS sheep genetics matched with low level (100 mL/head/day) of Spirulina supplementation can lead to higher meat production with less fat content in a typical pasture-based sheep production system.

THE BLEEDING OF THE SHEEP BREED '' HAMRA ''

Because of its extent and geographical diversity, Algeria has a very rich animal heritage. Among its animals, sheep whose roots, so deep, become bogged down well beyond the Numidian period, constitute a heritage that is both natural and genetic, highly varied. However, it is mainly the two steppe breed, namely "Hamra" in the West and "Ouled Djellal" in the East, which have left their mark on the richness of this living national heritage. It should be known that in the early days of French colonization, large quantities of sheep from Algeria, stolen from different steppe regions of the country, were exported to France, but also to its colonies. However, research on this subject reveals that a strong preference for the Hamra breed has quickly seized the brokers responsible for the collection of livestock for export. Thus from 1929 until the last years of colonization, more than a million heads of sheep "Hamra" will be exported, annually, by the French colonists to the metropolis, more exactly to the port of Marseille. Embarkations were made from the port of Arzew, in the West, and the port of Algiers, for the Center and the East. Currently, to make their farms profitable, sheep owners have chosen the ovine genetic type which makes it possible to achieve the best economic and financial profits. And so it was from the time of the mechanization of the steppe and the drought of 1970 that the regression process of the ovine breed Hamra was accentuated. In fact, all thebreeders of the Hamra breed who were formerly hampered by the distances and especially by the reliefs and the lack of means of transport of the cattle began to use heavy breeding rams such as the Ouled Djellal type. This led, over time, to the genetic absorption of the Hamra sheep, which occurred in favor of the Ouled Djellal breed and its crosses, which now constitute more than 65% of the national herd population. Only 20% of which are purebred. Thus, after forty years and in the absence of a policy of management of animal genetic biodiversity, the Hamra breed is now in danger of total extinction. This could be the loss of a national genetic resource but also a heritage that is more than a thousand years old. In fact, apart a few former breeders who still hold a small number of sheep descended from the Hamra breed, this Algerian sheep breed has become unknown today by the majority of young breeders. Pending the reaction of the public authorities, the association for the preservation and promotion of the Hamra breed (APPRHamra), newly created in the wilaya of Naama, engaged with the scientific community (geneticists, agronomists, veterinarians ...) a action to promot this breed and militates in for the preservation of this animal heritage dating back several centuries.

High systemic and testicular thermolytic efficiency during heat tolerance test reflects better semen quality in rams of tropical breeds.

This study aimed to assess the capacity of Morada Nova (MN) and Santa Inês (SIN) rams to maintain body and testicular homeothermy under thermal challenge. For 5days in the summer, 16 males (SIN=7 and MN=9) underwent a heat tolerance test, i.e., period 1-animals maintained in the shade (11 to 12h); period 2-animals exposed to sunlight (12 to 13h); and period 3-animals returned to the shade (13 to 14h). The respiratory rate, heart rate, rectal temperature, and infrared surface temperatures (IRT) of the trunk, back, eyeball, and testicles were assessed in each period. The index of capacity of tolerance to insolation (ICTI), which indicates the animals' level of adaptability, was calculated for each animal. Semen quality and testicular parenchyma integrity were assessed before and after the thermal challenge. Statistical analyses were performed at 5% significance. In period 1, the variables had baseline values for both genotypes. In period 2, the variables involved in thermolysis significantly increased (P<0.05), which matches a thermal discomfort situation. In period 3, the variables returned to baseline values and some values were lower than those in period 1. Semen quality and testicular parenchyma integrity suffered no negative effects with the thermal challenge. IRT ocular and IRT testicular were positively correlated (P<0.05). It is concluded that MN and SIN rams had efficient thermolytic mechanisms that favor preserving gonadal functionality. The animals were considered resilient to a thermal challenge. In addition, infrared thermography was an efficient tool to verify body and testicular thermoregulation.