Effect of Melatonin Implants during the Non-Breeding Season on the Onset of Ovarian Activity and the Plasma Prolactin in Dromedary Camel

To examine a possible control of reproductive seasonality by melatonin, continual-release subcutaneous melatonin implants were inserted 4.5 months before the natural breeding season (October–April) into female camels (Melatonin-treated group). The animals were exposed to an artificial long photoperiod (16L:8D) for 41 days prior to implant placement to facilitate receptivity to the short-day signal that is expected with melatonin implants. The treated and control groups (untreated females) were maintained separately under outdoor natural conditions. Ovarian follicular development was monitored in both groups by transrectal ultrasonography and by plasma estradiol-17β concentrations performed weekly for 8 weeks and then for 14 weeks following implant insertion. Plasma prolactin concentrations were determined at 45 and 15 days before and 0, 14, 28, 56, and 98 days after implant insertion. Plasma melatonin concentration was determined to validate response to the artificial long photoperiod and to verify the pattern of release from the implants. Results showed that the artificial long photoperiod induced a melatonin secretion peak of significantly (P < 0.05) shorter duration (about 2.5 h). Melatonin release from the implants resulted in higher circulating plasma melatonin levels during daytime and nighttime which persisted for more than 12 weeks following implants insertion. Treatment with melatonin implants advanced the onset of follicular growth activity by 3.5 months compared to untreated animals. Plasma estradiol-17β increased gradually from the second week after the beginning of treatment to reach significantly (P < 0.01) higher concentrations (39.2 ± 6.2 to 46.4 ± 4.5 pg/ml) between the third and the fifth week post insertion of melatonin implants. Treatment with melatonin implants also induced a moderate, but significant (P < 0.05) suppressive effect on plasma prolactin concentration on the 28th day. These results demonstrate that photoperiod appears to be involved in dromedary reproductive seasonality. Melatonin implants may be a useful tool to manipulate seasonality and to improve reproductive performance in this species. Administration of subcutaneous melatonin implants during the transition period to the breeding season following an artificial signal of long photoperiod have the potential to advance the breeding season in camels by about 2.5 months

Diagnostic Accuracy of an Indirect Enzyme Linked Immunosorbent Assay (iELISA) for Screening of <i>Babesia bovis</i> in Cattle from West Africa

The epidemiology of corresponding tick-borne diseases has changed as a result of the recent introduction of Rhipicephalus (Boophilus) microplus to West Africa. The current study aimed to assess the diagnostic performance of an indirect ELISA for the detection of Babesia bovis infection in cattle. In a cross-section study, using a Bayesian Latent Class Model and iELISA diagnostic test for cattle babesiosis due to Babesia bovis, accuracy has been assessed with RT-PCR as an imperfect reference test. A total of 766 cattle were tested. The optimal diagnostic performances were obtained with 5% percentage of positivity. Sensitivity and specificity were, respectively, 0.94 [Cr. I.: 0.85–0.99] and 0.89 [Cr. I.: 0.87–0.92]. Additional diagnostic characteristics revealed that the Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were 96.6% [Cr. I.: 92.7–100%] and 82.2% [Cr. I.: 72–93%]. Overall, this test well discriminates an infected status from an uninfected status considering the area under the ROC curve (AUC) which was 0.78 [Cr. I: 0.72–0.85] and a Diagnostic Odds Ratio (DOR) of 127.8 [Cr. I.: 10.43–1562.27]. The AUC was significantly higher than 0.5 (p −5). In consequence, this serologic assay could be suitable in moderate to high prevalence assessments

Effet du niveau d’alimentation sur le poids vif, la taille, la teneur en lipides et le volume des adipocytes de la bosse chez le dromadaire

International audienc

Effects of feeding level on body weight, hump size, lipid content and adipocyte volume in the dromedary camel

Les effets de la suralimentation et de la sous-alimentation sur les réserves lipidiques chez le dromadaire ont été mesurés chez 14 chamelles divisées en trois lots : un lot suralimenté - sous-alimenté (OV-UN), un lot sous-alimenté - suralimenté (UN-OV) et un lot témoin (CTRL). Après 4 semaines d'adaptation un schéma expérimental croisé a été appliqué pendant 16 semaines comprenant 2 périodes de 8 semaines chacune. L'apport énergétique des 3 niveaux d'alimentation représentait 17, 68 et 134 % des besoins énergétiques théoriques d'entretien respectivement pour le régime sous-alimentation, témoin et suralimentation. Le poids vif et les paramètres barymétriques ont été mesurés chaque semaine. Les biopsies de la bosse pour la détermination de la taille des adipocytes et la teneur en lipides ont été réalisées mensuellement. La suralimentation a un effet significatif sur le poids vif, la taille de la bosse et sa teneur en lipides ainsi que sur le volume des adipocytes. Le poids de la bosse augmente de 71 % pour le lot OV-UN et de 19 % pour le lot UN-OV. La teneur en matière grasse augmente de 52,9 à 63,6 % pour le lot OV-UN et de 54,2 à 64,7 % pour le lot UN-OV. Des évolutions similaires sont observées pour le volume des adipocytes qui augmente de 138 à 253 pL et de 275 à 346 pL pour les lots OV-UN et UN-OV, respectivement. La sous-alimentation a un effet inverse avec une diminution du poids de la bosse de 41 % pour le lot OV-UN et de 4 % pour le lot UN-OV. La teneur en lipides de la bosse diminue également significativement de 63,6 à 53,0 % pour le lot OV-UN et de manière non significative de 58,0 à 54,2 % pour le lot UN-OV. De même, la sous-alimentation diminue significativement le volume des adipocytes de 253 à 167 et de 292 à 275 pL pour les lots OV-UN et UN-OV, respectivement. Une corrélation hautement significative est observée entre le volume des adipocytes de la bosse et sa teneur en lipides. La faible vitesse de variation de la taille de la bosse, de sa teneur en lipides et de la taille de ses adipocytes sont probablement des particularités liées aux mécanismes d'adaptation du dromadaire à la sous alimentation dans les zones arides. (Résumé d'auteur