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International audience; This review describes the effects of milking (routine and management) on milk yield and milk quality on dairy ruminants and examines the physiological effects of milking on the synthesis and secretion of milk. During milking, differences in the composition of milk as a result of milk ejection reflex are observed: the cisternal milk, immediately available, contains little fat, then milk ejection provokes active transport of high-fat content alveolar milk, into the cisternal compartment. Milking frequency has the capacity to affect milk production too. So, an increase in milking frequency augments milk yield whereas a decrease in milking frequency decreases milk production, with effects on milk composition. The milk ejection reflex is mediated by oxytocin, which induces myoepithelial cell contraction. Nevertheless, other actions of oxytocin may exist, such as a direct effect on proliferation and differentiation of myoepithelial cells and on secretory processes in the mammary epithelial cells.; Ocytocine et vidange mammaire : deux facteurs de variation essentiels de la quantité et la qualité du lait pendant la traite et entre les traites. Cette revue bibliographique présente les effets de la traite (technique et conduite) sur la production quantitative et qualitative de lait, puis précise les mécanismes d'action des effets physiologiques de la traite sur la synthèse et la sécrétion des composants du lait. Au cours d'une traite, la composition du lait évolue, grâce au réflexe d'éjection du lait qui provoque le transfert du lait alvéolaire, riche en matières grasses, vers la citerne. Ainsi, le lait de début de traite est pauvre en matière grasse, tandis que le lait de fin de traite est riche en matière grasse. Les rythmes de traite ont aussi un impact sur la production laitière. Ainsi, l'accroissement de la fréquence de traite augmente la production laitière alors que la réduction du nombre de traite la diminue, avec des répercussions en terme de qualité du lait. L'hormone responsable de l'éjection du lait, l'ocytocine, exerce son rôle de vidange mammaire par déclenchement de la contraction des cellules myoépithéliales. Cependant, d'autres effets sont envisagés avec notamment un effet direct de l'ocytocine sur la prolifération et la différentiation des cellules myoépithéliales et épithéliales et sur les processus sécrétoires des cellules épithéliales.

[Departement_IRSTEA]GT [TR1_IRSTEA]RURAMEN / AMANDE; National audience; In order to gain a better knowledge and understanding and to analyse the conflicts that commonly occur in rural and periurban areas, we have, for the last four years, worked on a research programme on land-use and neighbourhood conflicts. This programme is conducted in partner ship between different French multi-disciplinary teams from public research institutes. Our research consists in giving conflicts the attention they deserve and in studying them closely without diabolising them. It is deliberately based on an empirico-deductive approach and aims to analyse how conflicts emerge and develop and what modes of conflict resolution are used within the French territory. The research rests on a series of empirical studies conducted in different regions, deemed representative of the national territory. In the paper, we first present our approach, the definition of conflicts, the hypotheses of the research and our methodology (1). We then propose a presentation of the results obtained in the framework of studies conducted in six specific geographical areas (2). Finally, we draw a number of general conclusions about the generic nature of land-use and neighbourhood conflicts in rural and periurban areas (3).; Afin de mieux connaître, comprendre et analyser les conflits qui traversent les espaces ruraux et périurbains nous avons élaboré, depuis quatre ans, un programme de recherche sur les conflits d’usage et de voisinage, mené conjointement, dans le cadre français, par différentes équipes pluridisciplinaires appartenant à des organismes de recherche publique. Notre recherche consiste à prendre les conflits au sérieux et à les étudier de près, sans les diaboliser. Elle est délibérément construite sur des fondements empirico-déductifs et se donne pour objectif d’analyser les modalités d’émergence, le déroulement et les tentatives de résolution des conflits au sein de l’espace français. Le travail est fondé sur une série d’études empiriques, menées sur différentes zones, jugées représentatives du territoire national. Cet article présente tout d’abord notre approche, la définition des conflits, les hypothèses de la recherche et la méthode de travail (1). Nous procédons, ensuite, à une présentation des résultats obtenus dans le cadre des études menées dans six zones géographiques particulières (2). Nous en tirons, enfin, un certain nombre de réflexions générales, concernant les caractères génériques des conflits d’usage et de voisinage des espaces ruraux et périurbains (3).

In postparturient goats, olfactory recognition of the young allows the establishment of a selective bond between the mother and her kids. Once this bond is formed, the mother rejects alien young that attempt to suckle. We tested whether the development of the maternal selective bond in goats modulates prolactin (PRL) and oxytocin (OT) release in response to suckling. On day 37 of lactation, serial blood samples were taken during nursing of the mother's own or alien kid(s) in 10 intact/selective goats and in 10 goats rendered anosmic/nonselective through prepartum peripheral ZnSO(4) irrigation. Spontaneous nursing behavior was also studied weekly from day 7 to 30 of lactation, at which time milk production was measured. Maternal selectivity had no effect on PRL release, in contrast to OT release, which was significantly affected by this factor. Intact mothers released OT only when nursing their own kids, but not with aliens, while anosmic/nonselective dams showed an increase in OT levels regardless of the identity of the kids. In addition to these effects on maternal selectivity, the amplitude of the response of both hormones was lower in anosmic mothers than in intact mothers. Finally, nursing behavior and milk production were not significantly affected by anosmia. We conclude that maternal selective behavior in goats, which relies on the individual olfactory signature of the kid, modulates the OT, but not the PRL, response to suckling. In addition, perception of the smell of the young appears to have a general facilitatory effect, independent of the kid's identity, on the release of both hormones.

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*INRA Centre de Rennes (FRA) Diffusion du document : INRA Centre de Rennes (FRA); National audience

chap. 12; International audience

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Cheese can be considered as a paracasein network including fat and aqueous phases. Changes in the composition of the aqueous phase reflect the enzymatic and physico-chemical phe- nomena that occur in cheese during ripening. For the first time, juice was expressed by pressing from Camembert cheese ripened up to 16 d and analysed in addition to the cheese to evaluate the extent of proteolysis together with the solubilisation of minerais. The amount of expressable juice decreased sharply during ripening, i.e. from 67 to 19 % of the total water content for cheeses ripened 0 and 16 d, respectively. In parallel, the levels of pH 4.6-soluble nitrogen and non-protein nitrogen increased in the whole Camembert cheese; the increase was higher in the juice. Simultaneously, the concentration of organic phosphate in the juice increased with concomitant decreases in the concentrations of cal- cium and inorganic phosphate. This last observation suggests that salt precipitates at the surface of the cheese. The expression and subsequent analysis of juice from Camembert cheeses is an appropriate method for following the sequential action of proteolytic enzymes and minerai transfer that occur dur- ing ripening. © InralElsevier, Paris. soft cheese / aqueous phase / proteolysis / mineral/ ripening

The aim of our in vitro experiments with isolated porcine ovarian follicles was to study the effects of gonadotropins, GH, IGF-I and oxytocin (OT) on release of ovarian steroid, OT, IGF-I, insulin-like growth factor-binding protein-3 (IGFBP-3), prostaglandin F (PGF), prostaglandin E (PGE) and cAMP. It was found that quarters of ovarian follicles cultured for 8 days produced significant amounts of progesterone, estradiol-17 beta, OT and IGFBP-3 with peaks of accumulation from the 3rd to the 8th day of culture. Addition of serum promoted progesterone, estradiol and OT release, whilst accumulation of IGFBP-3 was maintained to a greater extent in serum-free medium. GH (10 ng/ml or above) was able to inhibit androstenedione, OT, PGF and IGFBP-3, to stimulate IGF-I and cAMP, and to alter testosterone and PGE release by follicles cultured in serum-supplemented and/or serum-free medium. IGF-I (10 ng/ml or more) inhibited androstenedione and PGF secretion, stimulated testosterone, estradiol, OT and cAMP production, but did not influence progesterone, IGFBP-3 or PGE output in these conditions. OT (100 ng/ml) was able to inhibit androstenedione and to stimulate testosterone, IGF-I, PGF and PGE, but not estradiol or IGFBP-3 release. A stimulatory effect of LH on progesterone and OT and an inhibitory influence of LH on estradiol secretion in the serum-supplemented medium were observed. FSH in these conditions stimulated OT, but not progesterone or estradiol secretion. The use of this experimental model suggests the involvement of gonadotropins, OT, GH and IGF-I in the control of ovarian steroid and nonapeptide hormone, growth factor, growth factor-binding protein, prostaglandin and cyclic nucleotide production. The stimulatory effect of GH on IGF-I, and the stimulatory influence of IGF-I on OT, as well as coincidence of the majority of effects of IGF-I and OT, suggest the existence of a GH-IGF-I-OT axis. On the other hand, the different patterns of action of GH and IGF-I on OT, estrogen and IGFBP-3 suggest that part of the GH effect on ovarian cells is IGF-I independent.

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GRS'98, résumé P-15; International audience

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152 ref. 6 graph. Chantier qualité spécifique "Auteurs Externes" département de Génétique animale : uniquement liaison auteur au référentiel HR-Access; International audience

Spécial Space; National audience

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Trois lots equilibres de 44 brebis Lacaune traites a la machine apres 48 heures d'allaitement sont soumis entre la 8e (S8) et la 23e semaine (S23) de leur lactation aux trois traitements suivants. Lot 1 (superovule): six injections de FSH et LH sont appliquees toutes les 4 semaines (S8, S12, S16, S20) au moment de la depose d'une eponge (40 mg FGA) placee dans le vagin 14 jours plus tot (S6, S10, S14, S18). Lot 2 (eponge): des eponges vaginales (40 mg FGA) sont posees au meme stade et pour la meme duree que le lot 1 mais les injections de FSH et LH sont supprimees. Lot 3 (temoin): Il ne recoit ni FGA, ni FSH, ni LH. Au cours des 16 semaines experimentales (S8 a S23), les lots 3, 2 et 1 produisent en moyenne quotidiennement et respectivement 955,3, 983,8 (+ 3,0 %) et 1 063,0 (+ 11,3 %) mL de lait; 68,1, 68,6 (+ 0,7 %) et 74,1 (8,8 %) g de matieres grasses et 47,1, 48,1 (+ 2,1 %) et 52,3 (+ 11,1 %) g de matieres proteiques. Ce travail suggere que la secretion lactee pourrait etre stimulee par: i) les progestagenes exogenes (FGA) ou endogenes (progesterone) mais le mecanisme d'action reste a preciser; ii) l'ocytocine luteale, qui, en facilitant le transfert du lait alveolaire vers la citerne, evite les consequences inhibitrices de la stagnation lactee sur le metabolisme des cellules qui tapissent les parois des acini.

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The pure tetrameric form of Acetylcholinesterase (EC-3.1.1.7) from the electric eel electrophorus electricus has been covalently coupled to oxytocin. This conjugate has been used as tracer in a heterologous competitive immunoassay. Microtiter plates coated with a mouse monoclonal anti-rabbit immunoglobulin antibody were used to separate bound and free moieties of the tracer. Acetylcholinesterase activity bound to the solid phase was measured by a colorimetric assay. The minimum detectable concentration was 0.075 pg/well (ie 1.5 pg/ml) and precision was less than 8% at concentration above 0.15 pg/well. An extraction step improved sensitivity up to 10 times with good recoveries. To assess the validity of this assay, basal levels of oxytocin were measured during the oestrous cycle of a cow.

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Supplement 1; National audience

This experiment was conducted in 59 Lacaune breed ewes in order to compare milk production and milk distribution between alveolar and cisternal storage after superovulation. After a corpora lutea (CL)-free control period, the ewes were superovulated by different treatments (experimental period) and 5 classes were differentiated according to the number of corpora lutea observed (0, 1, 2, 3 to 6 and > 6 CL respectively (group A (n = 20), B (n = 7), C (n = 14), D (n = 7), E (n = 11)). Our results showed a positive correlation between the number of corpora lutea and the oxytocin and progesterone levels in plasma, total milk production and cisternal volume, and a negative correlation with alveolar volume. The milk production at the evening milking for groups A and E (388.6 and 384.8 ml respectively during the control period) respectively reached 321.7 ml (-17.2%) and 413.4 ml (+7.4%) during the experimental period; ie, a 24.6% difference between these 2 extreme groups. These results could likely be explained by oxytocin levels reaching those obtained during milking and by the effect of milk transfer from the alveolar to the cisternal lumen. Additionally, progesterone could act directly on milk synthesis at the level of the secretory cells.

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The diagnosis of pregnancy described in this article is based on the observation of milk ejection which, in the case of corpus luteum maintenance, results from the release of luteal oxytocin induced by intravenous administration of a non luteolytic dose of PGF2 alpha. The tests were performed in 410 lactating cows, 18-22 days after insemination (mean 19.95 days, SD 0.75), 3 h prior to the evening milking. A cannula was placed in the left fore-teat; when the cisternal milk flow ceased, a small dose of a prostaglandin F2 alpha analogue (256 micrograms Dinolytic) was injected. If a corpus luteum was present, the alveolar milk flow (1,276 +/- 570 ml) started 86 +/- 35 s later and pregnancy could be presumed. If the corpus luteum was no longer functional, the milk flow did not start again and the cow was considered not pregnant. The accuracy of positive results, ie 72.3%, significantly exceeded that obtained by radioimmunoassay of plasma progesterone used as a reference method, ie 68.6% (P less than 0.05). By contrast, the accuracy of negative results was lower, ie 93.5 vs 100%, (P less than 0.05): of the 195 pregnant cows which proceeded to term, 10 did not respond to the milk ejection test. In spite of these reserves, the test has the advantage of being inexpensive, rapid (about 5 min) and easy to interpret, ie either the milk flows or it does not. In addition, it may be used early, because from day 20 after Al the reliability of prediction of non pregnant cows (67.0%) was significantly higher when compared to the use of progesterone radioimmunoassay (58.6%) (P less than 0.05). With such a test, non pregnant cows can be reinseminated immediately and not only after a 3-week period. This may contribute to reducing the length of the infertile period.

Suplemento 1; International audience

Suplemento 1; International audience