L'imagerie de précision au service de l'expérimentation terrain

National audienceLes progrès technologiques réalisés dans les domaines de l’imagerie offrent de nouveaux outils transpo‑ sables sur le terrain au service du phénotypage de précision, au niveau des élevages

The use of computer tomography to estimate reticulo-rumen content in Alpine goats

International audienceEstimation of reticulo-rumen content (volume and mass) is required in ruminant nutrition to determine effects ofdiet and environment on gut filling, nutrient turnover and to model digestive processes. Reticulo-rumen content is commonly measured via a rumen cannula. Animal scientists continuously seek to refine experimental procedures by developing less invasive techniques. The objective was to compare reticulo-rumen volume assessed by computer tomography (CT) with post mortem measurement of reticulo-rumen content mass in dairy goats. Twenty Alpine dairy goats (3±0.6 years old; 226±9 DIM) with body weight ranging from 47 to 72 kg were used. Goats were housed in a free-stall barn, had free access to hay and water, and were offered 0.75 kg/d of concentrate. Goats were anesthetised and placed in an inflatable mattress before duo CT scan (Siemens, Erlange, Germany) was performed. Between 400 to 500 images were generated per goat and analysed semi-automatically (www.turtleseg.org). The volume of reticulorumen and omasum were determined separately. Each goat was slaughtered within 15 min after CT, the reticulo-rumen and omasum were weighed full and after removing the digesta, and content weights were obtained by difference. The SAS GLM procedure was used to test simple regressions between organ volume obtained with CT and digesta mass measured post mortem. Volume of reticulo-rumen and omasum determined by CT were good estimators of digesta mass measured post mortem [R2=0.72 and 0.73, residual standard deviation (rSD)=1.18 and 0.10 kg and residual coefficient of variation (rCV)=11 and 22%, respectively, n=20]. The regression was improved for omasum content when one individual with an extremely low digesta mass (22 g) was excluded (R2=0.87, rSD=0.06 kg, rCV=12%, n=19). The use of CT may constitute a promising non-invasive method to estimate volume and mass of reticulo-rumem digestive content in small ruminants. Further research is warranted to test the ability of this technique to discriminate dietary treatments that induce differential rumen fill

Automatiser la détection des chaleurs en valorisant l’identification électronique par boucle RFID chez les caprins

Séance : ReproductionInternational audienc

Host factors determine the evolution of infection with Staphylococcus aureus to gangrenous mastitis in goats

The online version of this article (10.1186/s13567-018-0564-4) contains supplementary material, which is available to authorized users.International audienceStaphylococcus aureus is the major cause of very severe mastitis of dairy goats. The initial objective of our study was to fine-tune an experimental model of infection of the goat mammary gland with two strains of S. aureus and two lines of goats (low and high somatic cell score lines). Following the challenge, the 10 infected goats divided in two clear-cut severity groups, independently of the S. aureus strain and the goat line. Five goats developed very severe mastitis (of which four were gangrenous) characterized by uncontrolled infection (UI group), whereas the other five kept the infection under control (CI group). The outcome of the infection was determined by 18 h post-infection (hpi), as heralded by the bacterial milk concentration at 18 hpi: more than 107/mL in the UI group, about 106/mL in the CI group. Leukocyte recruitment and composition did not differ between the groups, but the phagocytic killing at 18 hpi efficiency did. Contributing factors involved milk concentrations of α-toxin and LukMF' leukotoxin, but not early expression of the genes encoding the pentraxin PTX3, the cytokines IL-1α and IL-1β, and the chemokines IL-8 and CCL5. Concentrations of TNF-α, IFN-γ, IL-17A, and IL-22 rose sharply in the milk of UI goats when infection was out of control. The results indicate that defenses mobilized by the mammary gland at an early stage of infection were essential to prevent staphylococci from reaching critical concentrations. Staphylococcal exotoxin production appeared to be a consequent event inducing the evolution to gangrenous mastitis

L’impact de l’activité sexuelle sur la croissance des chèvres existe en 1ère ainsi qu'en 2ème saison sexuelle

National audienceL’âge et le poids à la puberté sont des facteurs décisifs du poids adulte et des performances de production pour les ruminants. L’espèce caprine est particulièrement sensible à ces caractéristiques de la puberté du fait du saisonnement de l’activité sexuelle et d’une conduite de reproduction en lot. Les chèvres n’atteignant pas un poids type en saison de reproduction la première année (environ 60% du poids adulte (Fiche_GRC_PHYSIOLOGIE, 2012) ont une reproduction reportée d’un an. Afin de caractériser la saisonnalité de l’activité sexuelle des chèvres, l’activité ovulatoire et le poids de femelles alpines, créoles et back-cross créole-alpines ont été mesurés de façon régulière au cours de leurs 2 premières saisons sexuelles sur l’unité expérimentale INRA de Bourges. L’objectif du présent travail est d’analyser l’impact du démarrage de l’activité sexuelle des chèvres sur leur croissance lors de la 1ère et 2ème saison sexuelle

Divergent selection on milk somatic cell count in goats improves udder health and milk quality with no effect on nematode resistance

International audienceMilk somatic cell count (SCC) is commonly higher in goats than in cattle and sheep. Furthermore, the ability of milk SCC to predict mastitis is considered lower in goats than in cattle and sheep, and the relevance of somatic cell score (SCS)-based selection in this species has been questioned. To address this issue, we created 2 divergent lines of Alpine goats using artificially inseminated bucks with extreme estimated breeding values for SCS. A total of 287 goats, 158 in high- and 129 in low-SCS lines, were scrutinized for mastitis infections. We subjected 2,688 milk samples to conventional bacteriological analyses on agarose and bacterial counts were estimated for positive samples. The SCS, milk yield, fat content, and protein content were recorded every 3 wk. Clinical mastitis was systematically noted. A subset of 40 goats (20 from each line) was subsequently challenged with Haemonchus contortus and monitored for anemia (blood packed cell volume) and fecal egg counts to see if SCS-based selection had an indirect effect on resistance to gastrointestinal nematodes. Milk production traits, including milk quantity, fat content, and protein content, were similar in both goat lines. In contrast, the raw milk SCC almost doubled between the lines, with 1,542,000 versus 855,000 cells/mL in the high- and low-SCS lines, respectively. The difference in breeding value for SCS between lines was 1.65 genetic standard deviation equivalents. The Staphylococcus spp. most frequently isolated from milk were S. xylosus, S. caprae, S. epidermidis, and S. aureus. The frequency of positive bacteriology samples was significantly higher in the high-SCS line (49%) than in the low-SCS line (33%). The highest odds ratio was 3.49 (95% confidence interval: 11.95-6.25) for S. aureus. The distribution of bacterial species in positive samples between lines was comparable. The average quantity of bacteria in positive samples was also significantly higher in high-SCS goats (69 ± 80 growing colonies) than in low-SCS goats (38 ± 62 growing colonies). Clinical cases were rare and equally distributed between high- (n = 4; 2.5%) and low-SCS (n = 3; 2.3%) lines. Furthermore, the larger the amounts of bacteria in milk the higher the SCS level. Conversely, goats with repeatedly culture-negative udders exhibited the lowest SCC levels, with an average of below 300,000 cells/mL. We therefore confirmed that SCS is a relevant predictor of intramammary infection and hygienic quality of milk in goats and can be used for prophylactic purposes. After challenge with H. contortus, goats were anemic with high fecal egg counts but we found no difference between the genetic lines. This result provides initial evidence that resistance to mastitis or to gastrointestinal nematodes infections is under independent genetic regulation. Altogether, this monitoring of the goat lines indicated that SCS-based selection helps to improve udder health by decreasing milk cell counts and reducing the incidence of infection and related bacterial shedding in milk. Selection for low SCC should not affect a goat's ability to cope with gastrointestinal nematodes