Two experiments were conducted to evaluate the effects of nature of forage on fatty acid composition and lipolytic system in cow milk to increase the nutritional quality of dairy products. Each experiment was divided into a 4-wk preexperimental and 6- or 8-wk experimental period. During the 2 preexperimental periods, 56 midlactating Montbéliarde or Tarentaise cows received a diet based on corn silage. Subsequently, in Experiment 1,40 cows were allocated into 5 groups (4 Montbéliarde and 4 Tarentaise cows per group) and assigned to dietary treatments: corn silage (87% of dry matter intake), grass silage (86%), ryegrass hay (90%), mountain natural grassland hay (87%), or a diet rich in concentrate (CONC, 65/35% concentrate/hay). In Experiment 2, 16 cows divided into 2 groups were fed during 3 or 6 wk mountain natural pasture (100%) or mountain natural grassland hay (87%). Principal component analysis was applied to describe the relationships among dairy performances, milk fatty acids (FA), and lipolytic system. The milk 18:0, cis-9-18:1, trans-11-18:1, and cis-9, trans-11-18:2 percentages were closely associated with 3-wk mountain natural pasture diet, whereas short- and medium-chain (mostly saturated) FA were associated with the CONC diet. Tarentaise milk fat contained a lower proportion (-3 to 4 g/100 g) of 16:0 and higher proportions of stearic acid and fewer markedly polyunsaturated FA than Montbéliarde milk fat. Milk lipolysis was lowest for CONC and corn silage groups. Milk from Tarentaise cows presented lower initial free FA and postmilking lipolysis. Diets given to cows, especially young grass, modified the milk content of FA with a putative nutritional effect on human health.

This review summarizes the recent developments in understanding of the relationships between the diet of animals and the sensory quality of dairy products. Feeding dairy cattle with maize silage by comparison with hay or grass silage leads to whiter and firmer cheeses and butter and sometimes to differences in flavour. Major differences in sensory characteristics were observed between cheeses made with milk produced by cows on winter diets (based on hay and grass silage) or turned out to pasture in the spring. Conversely, preserving grass as silage, by comparison with hay, has no major effect on cheese sensory characteristics, except on colour, the cheese being yellower with grass silage. Several recent experiments have shown a significant effect of grass botanical composition on cheese texture and flavour. These effects are due to the presence in milk of specific molecules directly introduced by feeding (carotenes, terpenes) or produced by the animals (plasmin, fatty acids) under the effect of specific diets.

-The influence of pastures on milk characteristics was studied in natura in the Abondance cheese area (Haute-Savoie, France) on 10 diversified pastures exploited by 3 dairy farmers. The effects of the herd were controlled and measured by feeding an identical hay to herds. The plasmin activity and the concentration of long-chain poly-unsaturated fatty acids in milks produced in mountain pastures (n = 5, 1 500 and 1 850 m) were significantly higher (P < 0.001 and P < 0.05 respectively) than in milks from valley pastures (n = 5, 850 and 1 100 m). The terpene composition of milk was linked to the terpene composition of pastures. Milks from the pastures rich in dicotyledons, in particular Apiaceae, contained a greater quantity and a wider variety of terpenes, than milks from the pastures rich in Gramineae. The other volatile compounds, casein composition, calcium and phosphorus contents did not seem to be influenced by the type of pasture.pasture / milk / plasmin / fatty acid composition / volatile compound Résumé -Influence de la nature de pâturages alpins sur l'activité de la plasmine, la composition en acides gras et en composés volatils du lait. L'influence de la nature des pâturages sur les caractéristiques des laits a été étudiée in natura dans la zone du fromage d'Abondance (Haute-Savoie, France) sur 10 types de pâturages divers exploités par 3 producteurs. Les effets liés au troupeau ont été contrôlés et mesurés sur une période où les 3 troupeaux recevaient la même alimentation. L'activité de la plasmine et la teneur en acides gras poly-insaturés à 18 carbones étaient plus élevées dans les laits des pâturages de montagne (n = 5, 1 500-1 850 m) que celles des laits de pâturages de vallée (n = 5, 850-1100 m) (respectivement P < 0,001, P < 0,05). La composition en terpènes des laits est apparue dépendre de celle des pâturages. Les laits issus des pâturages les plus riches en dicotylédo-nes, notamment en ombellifères, contenaient plus de terpènes, tant en quantité qu'en variété, que les laits issus des pâturages riches en graminées. Les compositions en molécules volatiles non terpéni-ques et en caséines, les teneurs en calcium et phosphore n'ont pas semblé être influencées par le type de pâturage.pâturage / lait / plasmine / composition en acides gras / composé volatil

The transfer of monoterpenes and sesquiterpenes from forages into milk fat was studied in a group of cows fed successively with forages containing high and low amounts of these substances. In a first 24-d period the cows received 11 kg of a cocksfoot hay containing low quantities of monoterpenes and sesquiterpenes. In a second 36-d period, 3 kg of the cocksfoot were replaced by 3 kg of yarrow, a plant rich in terpenoids. In a third 24-d period the cows returned to the cocksfootbased diet they were fed in the first period. The quantities of monoterpenes and sesquiterpenes desorbed from the milk fat were measured by dynamic headspace-gas chromatography-mass spectrometry. Results showed that the quantities of monoterpenes had increased by the first milking carried out 8 h after ingestion of yarrow, whereas the increase in the quantities of sesquiterpenes was observed only after the third milking, 32 h after the diet change. The maximal quantities of monoterpenes and sesquiterpenes were measured after 4 d of the yarrow-enriched diet, after which the total quantities decreased, despite the constant supply of yarrow. Four days after discontinuing yarrow the amounts of monoterpenes and sesquiterpenes desorbed from the milk fat reverted to those measured during the first period. traceability / type of feeding / terpenoid analysis / purge-and-trap / gas chromatography-mass spectrometry Résumé-Transfert des monoterpènes et des sesquiterpènes des fourrages dans la matière grasse du lait. Le transfert des monoterpènes et des sesquiterpènes des fourrages dans la matière grasse du lait a été étudié sur un lot de vaches successivement nourries avec des fourrages riches ou pauvres

-This review summarises the last 10 years' knowledge established on the relationships between the management of animals (genetics, physiology and feeding) and the sensory quality of cheese. In the production of full-fat raw milk cheese, the cow's breed can modify the texture of cheeses because of differences in fat in dry matter content due to variations in the fat/protein ratio in milk. Within the same breed, large differences in texture and taste were observed between cheeses issued from milk differing by the genetic variant of β-casein (in dairy cows) or α s1 -casein (in goats). Except in very early or late lactation, the physiological stage had no significant effect on cheese sensory characteristics. In contrast, mastitis has a well-known negative impact on cheese sensory properties. Feeding dairy cows or goats with corn silage by comparison with hay or grass silage leads to whiter cheeses and sometimes to differences in flavour. Conserving grass as silage, by comparison with hay, has no important effect on cheese sensory characteristics, except on colour, which is yellower with grass silage. Conversely, major differences in sensory characteristics were observed between cheeses made with milk produced by cows fed winter diets (based on hay and grass silage) or turned to pasture in the spring. Several recent experiments showed a significant effect of grass' botanical composition on cheese texture and flavour. Those effects are due to the presence in milk of specific molecules or structures directly induced by feeding (carotenes and terpenes) or produced by the animals (plasmin, fatty acids and casein micellar structures) according to their genetic or physiological characteristics or under the effect of specific diets. Milk / cheese / sensory characteristic / feeding / genetic characteristicRésumé -Effets des facteurs de production sur les caractéristiques sensorielles des fromages : une revue. Cette revue fait le point sur les connaissances acquises au cours des 10 dernières années sur les relations entre les facteurs de conduite des animaux (génétiques, physiologiques et alimentaires) et la qualité sensorielle des fromages. Chez la vache, avec des fabrications au lait entier, la race peut modifier les caractéristiques de texture des fromages. Cet effet est lié essentiellement aux différen-ces de composition chimique des laits et donc de gras/sec des fromages. Au sein d'une même race, des différences importantes de texture et de goût ont été observées en fonction des variants généti-ques de la caséine β (espèce bovine) et surtout α s1 (espèce caprine). Le stade physiologique n'a un effet marqué sur la couleur, la texture et le goût qu'en tout début ou en toute fin de lactation. En revanche, les mammites ont un effet négatif important sur les caractéristiques sensorielles des fromages. L'utilisation d'ensilage de maïs conduit toujours à des fromages plus blancs, et parfois à des différences de flaveur. Lorsqu'elle est correctement réalisée, la conservation de l'herbe sous forme * Corresponding author:...

-To assess the relationship between conditions of milk production and cheese contents of components of nutritional interest, it is necessary to know to what extent the compositional variability of cheese depends on that of milk. The respective effects of milk composition and the cheese-making process on cheese compositional variability in components of nutritional interest were therefore studied under real conditions of cheese production considering four different cheese-making technologies. The nutritional characteristics of the original milk were subject to high variations partly due to animal species (cow vs. goat). Apart from the aspects related to the dry matter content of cheese, the cheese compositional variability in fatty acids, β-carotene, xanthophylls and vitamin E depended mainly on the composition of the original milk. For vitamin A, it was partially influenced by both the original milk composition and the cheese-making process. Regarding folates and minerals, as well as total antioxidant capacity, the cheese composition varied mainly with the cheese-making process. In addition, the cheese-making technology had a significant effect on the cheese composition in minerals and folates, but did not influence the other components affected by the cheesemaking process. Consequently, the cheese contents of fat-soluble compounds depend directly on the conditions of milk production. On the contrary, the composition of cheese in water-soluble compounds varies independently of the conditions of milk production. The total antioxidant capacity of pressed cheeses, unlike the original milk, was positively correlated with some fat-soluble antioxidants. It could therefore be influenced by the conditions of milk production. Résumé -Effets respectifs de la composition du lait et de la transformation fromagère sur la variabilité de composition du fromage en composés d'intérêt nutritionnel. De façon à étudier la relation entre les conditions de production du lait et les teneurs en composés d'intérêt nutritionnel dans le fromage, il est nécessaire de savoir dans quelle mesure la variabilité de composition du fromage dépend de celle du lait d'origine. Les effets respectifs de la composition du lait et de la transformation fromagère sur la variabilité de composition du fromage en composés d'intérêt nutritionnel ont donc été étudiés en conditions réelles de production du fromage et en considérant quatre technologies fromagères différentes. Les caractéristiques nutritionnelles du lait à l'origine du fromage sont soumises à de grandes variations en partie dues à l'espèce animale (vache vs. chèvre). Mis à part les aspects liés à la teneur en matière sèche du fromage, la variabilité de composition du fromage en acides gras, en β-carotène, en xanthophylles et en vitamine E dépend principalement de la composition du lait d'origine, alors que pour la vitamine A celle-ci est influencée à la fois par la composition du lait d'origine et par la transformation fromagère. Par contre, la composition en folates et en minéraux du fr...

-The effect of mastitis and related-germs on milk chemical composition (protein and lactose contents) and milk somatic cell count (SCC) was investigated in 501 milk quarter samples during two consecutive years in cows from three experimental herds. Each infected quarter was matched by a healthy one in the same udder, as a control. Milk protein and mineral assays were performed in a subsample of 128 milks. Staphylococci were the most frequently isolated germs (Staphylococcus aureus: 27%, coagulase-negative Staphylococci: 26%, Streptococci: 21%). Major milk pathogens (Staphylococcus aureus, Streptococcus uberis or Escherichia coli) associated with clinical signs of mastitis were accompanied by higher SCC (+1.6 log·mL -1 , P < 0.01), lower lactose concentration (-7.6 g·kg -1 , P < 0.01), higher protein concentration (+3.3 g·kg -1 , P < 0.01) and higher soluble protein concentrations (IgG and BSA), hence a sharp decrease in the casein/protein ratio (-10 percentage points, P < 0.01). Changes were more marked when Escherichia coli was present. Corynebacterium bovis did not alter milk chemical composition whereas coagulase-negative Staphylococci slightly reduced lactose concentration (-1.8 g·kg -1 ) and increased SCC (+0.37 log·mL -1 ). Calcium and phosphorus milk contents were hardly modified by the presence of microorganisms. The decrease in milk yield during clinical mastitis varied from 1.6 kg·d -1 in the presence of Staphylococcus aureus to 15 kg·d -1 in the presence of Escherichia coli. mastitis / milk composition / microorganismRésumé -Effet du type de mammite et du germe sur la production et la composition du lait lors d'infections mammaires naturelles chez la vache laitière. L'effet de la nature des germes pathogènes présents dans le lait sur la composition chimique (taux protéique, taux de lactose) et la numération cellulaire du lait a été étudié à partir d'un échantillon de 501 laits de quartiers prélevés au *Correspondence and reprints E-mail: jbc@clermont.inra.fr cours de 2 années consécutives sur les vaches de 3 troupeaux expérimentaux. Pour chaque quartier infecté, un quartier sain de la même mamelle a servi de témoin. Sur 128 de ces prélèvements, des analyses de la composition minérale et protéique des laits ont été réalisées. Les germes les plus fréquemment observés ont été les staphylocoques (27 % de Staphylococcus aureus et 26 % de staphylocoques à coagulase négative) et les streptocoques (21 %). Lorsqu'elle a été associée à des signes de mammites cliniques, la présence d'un germe majeur (Staphylococcus aureus, Streptococcus uberis ou Escherichia coli) s'est accompagnée d'une augmentation de la numération cellulaire (+1,6 log·mL -1 , P < 0,01), d'une diminution de la teneur en lactose (-7,6 g·kg -1 , P < 0,01), d'une augmentation du taux protéique (+3,3 g·kg -1 , P < 0,01) et du taux de protéines solubles (IgG et BSA), de sorte que le rapport caséines/protéines a fortement diminué (-10 points de pourcentage, P < 0,01). Ces modifications ont été les plus importantes en présence d'Escherichia ...

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