Philippe Chemineau

El objetivo del presente estudio fue evaluar si la exposición al efecto macho, a los 9 o 10 meses de edad, adelanta la pubertad y mejora la fertilidad al parto en cabras nacidas en septiembre, mantenidas bajo un sistema semiextensivo con complementación alimenticia. Se trabajó con cabras de dos rebaños distintos. Las hembras fueron estabuladas desde el nacimiento, destetadas a los dos meses y manejadas en pastoreo diario junto a cabras adultas, recibiendo al finalizar una suplementación ajustada mensualmente según su peso vivo. A los 9 meses de edad (12 de junio), las hembras del primer rebaño fueron expuestas durante 15 días a machos adultos, mientras que las del segundo rebaño permanecieron aisladas de los machos. Un mes después, este segundo grupo fue expuesto a machos durante el mismo periodo. La exposición al efecto macho en junio indujo la ovulación en todas las cabras, mientras que las hembras mantenidas aisladas no presentaron actividad ovárica (P < 0,001). Cuando el segundo grupo fue expuesto a los machos en julio, todas las hembras ovularon y quedaron gestantes. Las tasas de parto no difirieron entre los dos grupos expuestos al efecto macho (P > 0,05). En conclusión, en cabras nacidas en septiembre y mantenidas bajo un sistema semiextensivo con suplementación alimenticia, la exposición al efecto macho a los 9 o 10 meses de edad adelanta el inicio de la pubertad y permite obtener elevadas tasas de fertilidad al parto.

In subtropical latitudes, goats are managed under semi-extensive systems grazing natural vegetation without supplementation. During the dry season, reduced forage availability leads to undernutrition and reduced breeding activity in bucks. This study evaluated whether pre-breeding nutritional supplementation enhances testosterone and reproductive performance in bucks joined with anestrous females. On 15 March, bucks were assigned to two groups (n = 6 each) and placed with separate flocks of 90–100 females grazing 9 h/day. Control bucks received no supplementation; supplemented bucks received 600 g/day of concentrate from 15 March to 30 May. Males were fitted with aprons until 1 June to prevent mating. Testosterone was low and similar between groups in March and April (P > 0.05). In supplemented bucks, testosterone increased from mid-May to mid-June, reaching higher than controls (P < 0.05). Females joined with supplemented bucks had higher fertility (71% vs. 53%; P < 0.01), earlier parturition, and a shorter kidding period (P < 0.0001). In conclusion, pre-breeding supplementation increases testosterone, improves fertility, and advances and synchronizes kidding under semi-extensive conditions.

Progesterone (P4) is an endogenous sex steroid hormone involved in the ovulatory cycle and pregnancy of animal species. In sheep and goats, P4 analogues are used to induce synchronized ovulations and oestrus behavior of the females. In humans, P4 from chemical synthesis is used to treat peri-menopausal disorders. However, such molecules are released into aquatic environment and can be a source of pollution, are prohibited in organic farms and go against the trend of “naturality” in animal production as well as in human health. A natural alternative may consist in the extraction and use of P4 in plants. Mammalian hormones were discovered in an increasing number of plant species, including walnut leaves that contain high levels of P4. We compared the content of P4 in leaves of 170 accessions of Juglans regia from the walnut germplasm collection of INRAE Prunus-Juglans Biological Resources Center previously genotyped using the Axiom™ J. regia 700 K SNP array. We conducted a genome-wide association study (GWAS) using multi-locus models. When collected in October, P4 content goes from 34,1 to 287,5 mg/kg dry weight of leaves. The two laciniate accessions have the largest P4 content. We identified seven significant marker-trait associations on chromosomes 1, 2, 3, 6, 7, 15 and 16, and a candidate gene involved in the metabolism of sterols, precursors of plant steroid hormones. Our results raise the huge variability of P4 content within J. regia and propose a candidate gene which may have a role in the control of this variability, opening the way to a potential use of walnut P4 by the pharmaceutical industry towards more natural source of chemical compounds.

In mammals, olfactory communication between conspecifics is crucial in modulating reproductive function. In anestrous does (i.e. female goats), exposure to hair from sexually active bucks (SAB, i.e. male goats) triggers a luteinizing hormone response that may induce ovulation, the “male effect.” However, the chemicals in buck hair responsible for this effect and the sensory pathways used by the females to detect this information remain insufficiently understood. In this study, we investigated whether sensory cells from the main olfactory epithelium (MOE) and the vomeronasal organ (VNO) of does respond differently to olfactory stimuli from SAB versus wethers (CAS, i.e. castrated bucks) and how this response is influenced by the female reproductive status (breeding season, anestrous, or ovariectomized (OVX)). To explore this possibility, we stimulated freshly dissociated cells of MOE and VNO cells with chloroform/methanol and aqueous extractions from buck hair, and we assessed cell activation using calcium imaging. Regardless of the extraction method, we observed more cells activated by SAB hair compounds than by those from CAS males. More MOE cells from anestrous were activated by both chloroform and aqueous extracts from SAB than MOE cells from breeding season, or OVX does. Most of these responses originated from non-mature olfactory neurons. These findings suggest that females can discriminate buck sexual activity through sensory detection by the MOE and VNO. The increased response in the MOE to SAB hair compounds during the anestrous period suggests that the MOE may play a more significant role in the “male effect” during this period.