Comparaison de la composition physicochimique du lait camelin et bovin du Sud tunisien; variation du pH et de l’acidité à différentes températures

La composition physicochimique du lait de chamelle est variable selon l’alimentation des animaux, les conditions environnementales ainsi que la période de lactation. Dans le but de déterminer la composition du lait de chamelle du sud tunisien, le lait camelin de la région a été comparé à celui bovin sur le plan de l’acidité et du pH du lait des deux espèces en fonction de la température du milieu. Le lait de chamelle est plus acide (17,25 ± 1,035°D) et moins dense (d= 1,027± 0,003) que le lait de vache. Le lait de vache est plus riche en matière protéique (34,15 ± 3,11 g/L), matière sèche (119,43 ± 15,34g/L) et azote non protéique NPN (1,04 ± 0,08g/L). Le suivi de la variation du pH et de l’acidité du lait camelin et bovin à trois températures différentes (température ambiante (25°C), à 4°C et à -4°C) a révélé une acidification plus lente du lait de chamelle dans les trois cas avec une conservation durant 30 heures à température ambiante, 7 jours dans le réfrigérateur (4°C) alors quelle est de 5 jours pour le lait de vache à la même température. La congélation du lait à -4°C peut ainsi constituer une méthode simple pour la conservation du lait camelin qui n’est accessible que dans les régions de sa production.Mots-clés : Lait, chamelle, vache, composition physicochimique, acidité,températur

Effects of two different management systems on hormonal, behavioral, and semen quality in male dromedary camels

Effects of two different management systems on male dromedary camel hormones, behaviors, and semen parameters were documented. Camels (n=6) were tested under two management systems: (i) housed in single boxes with 1-h freedom (H23); (ii) exposed to females for 17 h (from 3.30 p.m. to 8.30 a.m.) and then housed (ConExF). Blood was collected every morning; camel behavior was recorded twice a day: (i) from 7:00 to 8:00 a.m. to determine the short effects; (ii) from 2:00 to 3:00 p.m. to determine the long effects. Each camel underwent a female parade and semen collection thrice a week; sexual behavior, libido, and semen parameters were assessed. Testosterone and cortisol concentrations were higher in ConExF than H23. Compared to the H23 group, ConExF group spent more time walking, standing tripods, and looking outside their pen/box but they spent less time eating, ruminating, resting, standing, and showing stereotypical behaviors. In the morning, ConExF group spent more time walking, ruminating, and showing typical sexual behaviors compared to themselves during afternoon time and the H23 group. However, in the afternoon time, ConExF camels put more time their heads outside the box through the window and showed higher frequencies of stereotypies, probably due to a higher level of frustration. While the sexual behavioral score was higher and ejaculates showed a higher fraction of milky white and white-colored semen in ConExF than H23 group, their libido was similar. Overall, 17 h of exposure led to an increase in testosterone and cortisol levels, enhancing sexual behavior and semen color, but leading to frustration

Effect of diet supplementation on growth and reproduction in camels under arid range conditions

Eighteen pregnant dromedary females (Camelus dromedarius) were used to determine the effect of concentrate supplement on growth and reproductive performances in peri-partum period. The females were divided into supplemented (n = 9; S) and unsupplemented (n = 9; C) experimental groups. All animals grazed, with one mature male, 7 to 8 hours per day on salty pasture rangelands. During night, they were kept in pen, where each female of group S received 4 kg per day of concentrate supplement during the last 3 months of gestation and 5 kg per day during the first 3 months post-partum. During the last 90 days of gestation daily body weight gain (DBG) was at least tenfold more important in group S than in group C (775 g vs. 72 g respectively). Supplementation affected birth weight of offspring (30.3 kg vs. 23.4 kg) and its DBG (806 g vs. 430 g) in group S and group C respectively. During the post-partum period, females in group S gained in weight (116 g per day) whereas females in group C lost more than 200 g per day. The mean post-partum interval to the first heat and the percentage of females in heat were 29.5 day and 44.4/ vs. 41.2 day and 71.4/ for the C and S groups, respectively. We conclude that under range conditions, dietary supplementation of dromedary during late pregnancy stage and post-partum period improves productive and reproductive parameters

Air temperature measurements using autonomous self-recording dataloggers in mountainous and snow covered areas

High mountain areas are poorly represented by official weather observatories. It implies that new instruments must be evaluated over snow-covered and strongly insolated environments (i.e. mid-latitude mountain areas). We analyzed uncertainty sources over snow covered areas including: 1) temperature logger accuracy and bias of two widely used temperature sensors (Tinytag and iButton); 2) radiation shield performance under various radiation, snow, and wind conditions; 3) appropriate measurement height over snow covered ground; and 4) differences in air temperature measured among nearby devices over a horizontal band. The major results showed the following. 1) Tinytag performance device (mean absolute error: MAE≈ 0.1–0.2°C in relation to the reference thermistor) was superior to the iButton (MAE≈ 0.7°C), which was subject to operating errors. 2) Multi-plate radiation shield showed the best performance under all conditions (> 90% samples has bias between ±0.5°C). The tube shield required wind (> 2.5ms⁠−1) for adequate performance, while the funnel shield required limited radiation (< 400Wm⁠−2). Snow cover causes certain overheating. 3) Air temperatures were found to stabilize at 75–100cm above the snow surface. Air temperature profile was more constant at night, showing a considerable cooling on near surface at midday. 4) Horizontal air temperature differences were larger at midday (0.5°C). These findings indicate that to minimize errors air temperature measurements over snow surfaces should be carried out using multi-plate radiation shields with high-end thermistors such as Tinytags, and be made at a minimum height above the snow covered ground.This study was funded by the research projects “El papel de la nieve en la hidrología de la peninsula ibérica y su respuesta a procesos de cambio global-HIDROIBERNIEVE-CGL2017-82216-R” and CLIMPY “Characterization of the evolution of climate and provision of information for adaptation in the Pyrenees” (FEDER-POCTEFA)

Resin tapping in Pinus pinaster: effects on growth and response function to climate

Dendrocronología sobre Pinus pinaster, como la recolección de resina y los factores climáticos han afectado a su crecimiento