Effet de l'augmentation de l'alimentation calorique et du traitement au lasalocid sur la sécrétion des gonadotrophines chez les béliers

Chez le bélier adulte, la complémentation alimentaire par les grains de lupin ( Lupinus angustifolius ) stimule la secrétion des gonadotrophines. Pour tester la reproduction de cet effet par des rations alimentaires differentes, des béliers ont été soumis à une ration de base (1 kg de foin, 10% grain de lupin et 2,5% minéraux) ou une ration à niveau énergétique élevé (50% foin de luzerne, 27.5% foin broyé, 20% orge fourrager et 2,5% minéraux) au taux quotidien de 2.5% du poids vif pendant 7 jours. À la fin de cette période, la moitié du premier groupe a reçu 750 g/tête • jour alors que la moitié du deuxième groupe a reçu une dose orale de l'ionophore lasalocid (45 mg/kg d'aliment) pendant 10 jours. Le reste des béliers a continué à reçevoir leur ration alimentaire de départ. Des prises de sang ont été faites toutes les 20 min pendant 24 h à 0, 7 et 17 jours par rapport au début des traitements et ont été utilisées pour le dosage de l'hormone luté inisante. Des prises de sang toutes les 2 heures ont servi au dosage de l'hormone folliculo-stimulante (Jours 0, 7 et17), de l'insuline et du glucose (Jours 7 et 17) .. Des échantillons de liquide ruminaI, pris sur les béliers sous régime riche en énergie à 7 et 17 jours, ont été utilisés pour l'analyse des acides gras volatiles. Les résultats montrent que l'alimentation à base de lupin ou d'autres aliments riches en énergie est suceptible de stimuler les secrétion de la LH et de la FSH. Ces effets sont généralement associés avec des concentrations plasmatiques élevées de glucose et d'insuline

Anatomie et examen échographique des organes génitaux chez le bélier et le bouc

Breeding soundness examination (BSE) of rams and bucks is performed by veterinarians as a service for producers to help identify males that may not be capable of settling females early in the breeding season and sire offspring with the genetic potential for rapid and efficient growth. In the routine BSE, palpation of the testis cannot assess with accuracy testicular parenchyma and presence of small lesions. Ultrasonography and testicular biometric parameters are a better approach for evaluation of the testes. In addition, testicular ultrasonography can be a important tool for the evaluation of scrotal circumference and testicular volume and prediction of fertility potential. To provide a basis for this BSE, this paper presents a detailed overview of the anatomy of ram and buck reproductive system and outlines the basis for ultrasonographic examination of the genital tract. Common and uncommon ultrasonographically visible lesions of the scrotum and its content including abnormalities of the various testicular envelops, the spermatic cord, the testicular parenchyma, the epididymis and the internal genitalia are described and illustrated. Keywords: Ram, buck, breeding soundness examination, genital tract, anatomy, ultrasonography.L’examen de l’aptitude à la reproduction (EAR) des géniteurs réalisé par les vétérinaires permet d’identifier dès le début de la saison de reproduction, les mâles qui seraient capables de fertiliser des femelles. Ces mâles sont supposés garantir la production de descendants porteurs d’un potentiel génétique qui assure une croissance rapide et efficace. Lors de la réalisation d’un EAR de routine, la palpation du testicule ne permet pas d’évaluer avec précision l’état du parenchyme testiculaire et de détecter la présence de petites lésions. L’échographie et la détermination des paramètres biométriques testiculaires constituent une meilleure approche pour l’évaluation de l’état sanitaire des testicules. En outre, l’échographie testiculaire peut être un outil précieux pour l’évaluation de la circonférence scrotale et du volume testiculaire et pour la prédiction du potentiel de fertilité. Le présent article présente en détail l’anatomie du système reproducteur du bélier et du bouc, et décrit ensuite les bases de l’examen échographique du tractus génital. Les lésions échographiquement visibles du scrotum et son contenu, y compris les anomalies des différentes enveloppes testiculaires, le cordon spermatique, le parenchyme testiculaire, l’épididyme et les organes génitaux internes y sont détaillées et illustrées. Mots-clés: Bélier, bouc, examen de reproduction, tractus génital, anatomie, échographie

Examen de l’aptitude à la reproduction chez le bélier et le bouc

Male breeding soundness examination (BSE) is an important component of sheep and goat farming. BSE is best performed 2 months before the breeding season and is based on clinical and physical examination as well as sperm abnormalities detection. Rams are classified based on physical examination and semen evaluation finding in one of 4 categories: Unsatisfactory, questionable, satisfactory, and excellent. The satisfactory rams will achieve good reproductive performance if joined to ewes at a ratio of 1:50 for 60 days. However exceptional rams are expected to achieve good reproductive performance at a ratio of 1 ram to 100 ewes. For Buck, scrotal circumference should be at least 25 cm for breeds weighing more than 40 kg. Buck is deemed satisfactory breeder if he passes the physical examination, and has an ejaculate with at least 50 % progressively motile spermatozoa and less than 30 % total sperm abnormalities. This paper reviews factors affecting fertility, sperm production and quality as well as libido and mating ability in the ram. Details of genital examination and semen evaluation and interpretation of results are discussed. Classification of rams according to their reproductive potential is presented. Specific recommendations, when available for the buck, are highlighted. The main genital diseases are presented. The most frequent culling reason for ram is epididymitis due to Brucella ovis. Systematic culling of rams with epididymitis improves flock lambing rates by 10 to 15 %. Overall, the examination of the reproductive capacity in the ram and the buck is an important tool for improvement of flocks/herds fertility and prevention of contagious or hereditary diseases. Keywords: Genital diseases, fertility, sheep, goat.L’examen de l’aptitude à la reproduction (EAR) du mâle est une composante importante de l’élevage des petits ruminants. L’EAR est mieux réalisée 2 mois avant la saison de reproduction. Il est basé sur l’examen clinique et physique ainsi que sur la détection des anomalies des spermatozoïdes. En considérant les résultats de cet examen, les béliers sont classés en 4 catégories: Insatisfaisant, douteux, satisfaisant et excellent. Les béliers satisfaisants permettront d’obtenir de bonnes performances de reproduction s’ils sont mis pendant 60 jours pour saillir des brebis au ratio de 1:50. Cependant, des béliers exceptionnels peuvent réaliser une bonne performance reproductive au ratio de 1 bélier pour 100 brebis. Chez le bouc, la circonférence scrotale doit être d’au moins 25 cm pour les races pesant plus de 40 kg. Il est considéré comme satisfaisant s’il passe l’examen physique et produit un éjaculat avec au moins 50 % de spermatozoïdes progressivement mobiles et moins de 30 % d’anomalies totales des spermatozoïdes. Cet article examine les facteurs affectant la fertilité, la production et la qualité du sperme ainsi que la libido et la capacité de saillie chez le bélier. Les détails de l’examen de l’appareil génital et du sperme et l’interprétation des résultats sont traités. La classification des béliers selon leur potentiel de reproduction est présentée. Des recommandations spécifiques, lorsqu’elles sont disponibles pour le bouc, sont mises en évidence. Les principales maladies génitales sont traitées. La cause de réforme la plus fréquente chez le bélier est l’épididymite à Brucella ovis. La réforme systématique des béliers à épididymite améliore les taux d’agnelage des troupeaux de 10 à 15 %. Globalement, l’examen de l’aptitude de reproduction chez le bélier et le bouc est un outil important pour l’amélioration de la fertilité des troupeaux et la prévention des maladies contagieuses ou héréditaires. Mots-clés: Reproduction, maladies génitales, fertilité, bélier, bou

Environmental cues and seasonal patterns of reproduction in goats

Goats usually exhibit a seasonal sexual activity and breeding at a specific season ensures the survival of offsprings by coinciding parturition with the adequate period of nutrition and climate conditions. Photoperiod is the main modulator of this seasonality in goats within different latitudes. Other environmental cues like seasonal changes in ambient temperature cycles seem also to induce a synchronizing effect on this seasonality. Moreover, food availability was found to affect reproductive physiology. Indeed, an improved nutrition enhances sexual behavior in goats while under-nutrition and particularly a negative energy balance adversely impact this activity. On the other hand, the social interaction in this species also affects the expression of the physiology and the sexual behavior during the breeding season. Goats, generally display a good plasticity of adaptation to all weathers including hot, cold, wet and dry ones. This peculiarity seems genotype-dependent and may be crucial for an efficient anticipation of new changes in the environmental cues related to global climatic changes. In this review we outline the effect of exogenous and endogenous factors on reproduction in goats thus providing a basis for comparing previous studies on main factors controlling the breeding seasonality in this species. Keywords: Goats, seasonal breeding, photoperiod, ambient temperature, food availability, social cues, genotype.La chèvre présente une reproduction saisonnière. Cette saisonnalité permet de coïncider la parturition avec la période adéquate de la nutrition et les conditions climatiques pour la survie de la progéniture. La présente revue analyse à travers les différents biotopes, les facteurs intervenants dans l'expression de cette saisonnalité de l'activité sexuelle chez cette espèce. Sous les différentes latitudes, la photopériode est le principal modulateur de cette saisonnalité chez la chèvre. D'autres facteurs environnementaux comme les changements saisonniers des cycles de la température ambiante semblent également induire un effet de synchronisation de cette saisonnalité. De plus, la disponibilité de la nourriture affecte de manière sensible la physiologie de la reproduction chez cette espèce. En effet, un état de bonne nutrition renforce le comportement sexuel chez la chèvre, alors que la sous-nutrition et en particulier un bilan énergétique négatif ont un impact négatif sur cette saisonnalité. D'autre part, l'interaction sociale chez cette espèce affecte également l'expression de la physiologie et le comportement sexuel pendant la saison de la reproduction. La chèvre présente une bonne adaptation à tous les biotopes, y compris les chauds, froids, humides et secs. Cette particularité semble dépendre du génotype et peut être cruciale pour une anticipation efficace des changements climatiques globaux. Mots clés: Chèvre, reproduction saisonnière, photopériode, température ambiante, disponibilité alimentaire, facteurs sociaux, génotype

Kisspeptin signaling is required for the luteinizing hormone response in anestrous ewes following the introduction of males

The introduction of a novel male stimulates the hypothalamic-pituitary-gonadal axis of female sheep during seasonal anestrus, leading to the resumption of follicle maturation and ovulation. How this pheromone cue activates pulsatile secretion of gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) is unknown. We hypothesised that pheromones activate kisspeptin neurons, the product of which is critical for the stimulation of GnRH neurons and fertility. During the non-breeding season, female sheep were exposed to novel males and blood samples collected for analysis of plasma LH profiles. Females without exposure to males served as controls. In addition, one hour before male exposure, a kisspeptin antagonist (P-271) or vehicle was infused into the lateral ventricle and continued for the entire period of male exposure. Introduction of a male led to elevated mean LH levels, due to increased LH pulse amplitude and pulse frequency in females, when compared to females not exposed to a male. Infusion of P-271 abolished this effect of male exposure. Brains were collected after the male effect stimulus and we observed an increase in the percentage of kisspeptin neurons co-expressing Fos, by immunohistochemistry. In addition, the per-cell expression of Kiss1 mRNA was increased in the rostral and mid (but not the caudal) arcuate nucleus (ARC) after male exposure in both aCSF and P-271 treated ewes, but the per-cell content of neurokinin B mRNA was decreased. There was also a generalized increase in Fos positive cells in the rostral and mid ARC as well as the ventromedial hypothalamus of females exposed to males. We conclude that introduction of male sheep to seasonally anestrous female sheep activates kisspeptin neurons and other cells in the hypothalamus, leading to increased GnRH/LH secretion

Relationship between nutritional stimulation of gonadotrophin secretion and the peripheral and cerebrospinal fluid (CSF) concentrations of glucose and insulin in rams

In numerous studies it has been shown that supplementing diets of rams with lupin grain (Lupinus angustifolius), a highly digestible energy and protein source, increases gonadotrophin secretion, perhaps by providing metabolic signals that stimulate gonadotrophin-releasing hormone (GnRH) neurons. In the first experiment, we tested the hypothesis that the increase in gonadotrophin secretion caused by lupin supplementation is accompanied by an increase in cerebrospinal fluid (CSF) concentrations of glucose and insulin. In the second experiment, we tested the hypothesis that supplying peripheral glucose to rams, in quantities approximating those associated with digestion of a lupin supplement, would increase gonadotrophin secretion. After 10 days of dietary treatment in the first study, rams (n = 6) given a lupin supplement had increased luteinising hormone (LH) pulse frequencies (P < 0.05) and mean follicle stimulating hormone (FSH) concentrations (P < 0.05) compared with rams (n = 6) not given a lupin supplement. Compared with control values, glucose concentrations in CSF, but not plasma, were higher (P < 0.05) in the lupin-supplemented group by Day 10, and insulin concentrations in both plasma and CSF were higher (P < 0.05) in the lupin supplemented group on Days 3 and 10. In the second study, rams (n = 6) infused intravenously for 10 days with glucose (1.6 mol in l l of saline infused over 4 h) had increased plasma concentrations of glucose and insulin (P < 0.05) on Days 2 and 10, compared with values in saline-infused controls (n = 6). The secretion of LH and FSH was not affected by infusion with either saline or glucose. These experiments demonstrate that nutritional supplementation increases gonadotrophin secretion and peripheral and CSF concentrations of glucose and insulin, but short-term glucose infusion, which increases peripheral glucose and insulin concentrations, does not increase gonadotrophin concentrations. The absence of an increase in gonadotrophin secretion in glucose-infused rams suggests that glucose and insulin in the peripheral circulation do not influence gonadotrophin secretion. However, the glucose and insulin in CSF are not necessarily derived from the peripheral circulation, so further studies are needed to determine whether central glucose or insulin are involved directly in the control of gonadotrophin secretion

Effect of increasing dietary energy and lasalocid treatment on gonadotrophin secretion in rams

In the mature ram, supplementary feeding, for example with lupin grain, stimulates gonadotrophin secretion. To test whether this effect is reproducible with alternative diets not containing lupin grain, rams were fed either a basal diet (1kg of oat hay containing 10% lupin grain and 2.5% minerals) or a high energy diet (50% lucerne chaff, 27.5% hammer-milled oat hay, 20% rolled barley and 2.5% minerals) at the daily rate of 2.5% of live weight for 7 days. After this period, half of the first group received 750 g/head daily whereas half of the second group received a daily drench of an ionophore, lasalocid (45 mg/kg of food) for 10 days. The other rams remained on their respective diets. Blood was sampled every 20 min for 24 h on days 0, 7 and 17 relative to the start of treatments for the study of plasma LH pulse profiles. Plasma samples taken every other hour were assayed for FSH (days 0, 7 and 17), insulin and glucose (days 7 and 17). Rumen fluid samples taken, from rams fed the high energy diet, on days 7 and 17 were analysed for volatile fatty acid content. It is concluded that feeding either lupins grain or a high energy diet stimulates LH and FSH secretion. These effects are associated with increased plasma concentrations of glucose and insulin

Controls and manipulation of reproductive functions in native sheep

Meeting: Small Ruminants Research and Development in the Near East, 2-4 Nov. 1988, Cairo, EGIn IDL-298

Central metabolic messengers and the effects of nutrition on gonadotrophin secretion in sheep

Nutrition influences the reproductive axis via alteration of gonadotrophin secretion. However, a link between nutrition and the secretion of GnRH, which drives the axis, has yet to be established. The aim of the present study was to measure the change in the concentrations of metabolic substances in the cerebrospinal fluid of adult male sheep offered a diet designed to maintain constant gonadotrophin secretion (Group M; n = 6), or a diet known to increase gonadotrophin secretion (Group M + L; n = 6). On days 1, 3 and 10 of the dietary treatments, cerebrospinal fluid and jugular blood were sampled and analysed for metabolic fuels (glucose, amino acids and free fatty acids) and metabolic hormones (insulin, insulin-like growth factor I, GH, prolactin, cortisol and the thyroid hormones). On day 11 of the dietary treatment, LH pulse frequency and mean FSH concentrations in Group M + L had increased relative to Group M and to day 0. Plasma concentrations of prolactin and insulin on days 3 and 10, and glucose and insulin-like growth factor I on day 10, were higher in Group M + L than in Group M, but only cerebrospinal fluid concentrations of insulin, glucose and certain amino acids were affected by the dietary treatments on days 3 and 10. Cerebrospinal fluid, but not plasma, concentrations of aspartate, tyrosine, cystine, phenylalanine and arginine on day 3, and glutamine, γ-aminobutyric acid, threonine, alanine on days 3 and 10, were higher in Group M + L relative to Group M. On day 10, plasma and cerebrospinal fluid concentrations of arginine, phenylalanine, proline, tyrosine, methionine and phosphoserine, but only the plasma concentrations of linoleic acid, aspartate and serine, were higher in Group M + L than in Group M. Concentrations of triiodothyronine, thyroxine, and cortisol in plasma and cerebrospinal fluid were not affected. These results show that the nutritional stimulation of gonadotrophin secretion is accompanied primarily by fluctuations in plasma and cerebrospinal fluid concentrations of insulin and certain amino acids, which suggests that, when nutritional status is improved, insulin, amino acids and possibly glucose interact to modulate GnRH secretion