Philippe Pradel

Phospholipid, Sphingolipid, and Fatty Acid Compositions of the Milk Fat Globule Membrane are Modified by Diet

The phospholipid and sphingolipid composition of milk is of considerable interest regarding their nutritional and functional properties. The objective of this article was to determine the lipid composition of the milk fat globule membrane (MFGM) of milk from cows fed a diet rich in polyunsaturated fatty acids. The experiments were performed with 2 groups of 6 cows feeding on (i) maize silage ad libitum (+ grassland hay, mixture of cereals, soyabean meal) or (ii) the maize silage-based diet supplemented with extruded linseed (bringing a lipid proportion of 5% of dry matter). The phospholipid and sphingolipid composition of the MFGM was determined using HPLC/ELSD. The fatty acid (FA) composition of total lipids and phospholipids was determined using GC. As expected, the linseed-supplemented diet decreased the saturated FA and increased the unsaturated FA content in milk fat. MFGM in milk from cows fed the diet rich in polyunsaturated FA resulted in (i) a higher amount of phospholipids (+ 18%), which was related to a smaller size of milk fat globules (ii) an increase of 30% (w/w) of the concentration in sphingomyelin, (iii) a higher content in stearic acid (1.7-fold), unsaturated FA (1.36-fold), and C18:1 trans FA: 7.2 +/- 0.5% (3.7-fold). The MFGM contained a higher concentration of unsaturated FA (C18:1, C18:2, and C18:3) and very long-chain FA (C22:0, C23:0, C24:0, EPA, DHA) compared with total lipids extracted from milk. The technological, sensorial, and nutritional consequences of these changes in the lipid composition of the MFGM induced by dietary manipulation remain to be elucidated.

Nonnutritive oral activities and stress responses of veal calves in relation to feeding and housing conditions

Abstract This study assessed the extent to which eating solid foods and social contacts influence nibbling objects and improve the welfare of veal calves. Animals were fed milk replacer only vs. supplemented with solid foods and were housed in individual stalls vs. together in pens. Time budget, reactions to handling in a weighing machine, growth, health (length of medical treatments) and abomasal lesions were assessed. In addition, chronic activation of the hypothalamo–pituitary–adrenocortical axis was evaluated after ACTH and CRF challenges, and that of the sympathetic nervous system, through activities of catecholamine-synthesising enzymes. The provision of solid foods reduced time spent nibbling objects and being inactive in proportion to and at the time of the increase in time spent eating and chewing. The calves housed together in pens had higher basal cortisol levels and they reacted to weighing. Health and physiological indices of chronic stress did not vary with feeding or housing conditions. It is concluded that nibbling in veal calves derives at least in part from a lack of development of feeding behaviour appropriate to ruminants. There was no clear evidence of poorer welfare due to feeding on milk replacer only or individual housing, but calves reared in groups seemed more stressed by handling than calves reared in individual stalls.

Desorbed terpenes and sesquiterpenes from forages and cheeses

The composition and sensory characteristics of matured cheeses are controlled by a number of factors, among which the type of feed is important. The influence of feeding can be reflected by the presence in cheeses of terpenes and sesquiterpenes, compounds typically indicating their vegetable origin (Mariaca et al . 1997). Indeed, several investigators have already established that these compounds could characterize the forage even to a specific geographical location. Dumont & Adda (1978), Dumont et al . (1981), Guichard et al . (1987), Bosset et al . (1994) and Moio et al . (1996) were thus able to distinguish cheeses from lowland and upland regions. In most of these studies, the conditions under which milk was produced and processed were not completely controlled. Furthermore, all these studies analysed only the volatile fraction of cheeses and did not examine the volatile compounds in the forages used. Recently Bosset et al . (1994), in one part of the project described by Jeangros et al . (1997), showed that highland grass with a highly diversified botanical composition produces milk and cheeses with significantly different chemical compositions from those from lowland grass. To improve our understanding of the relationship between animal feed and cheese composition, we have investigated under controlled experimental conditions both the composition of the terpene and sesquiterpene fractions of four forages with different botanical diversities and the influence of those forages on the terpene fraction of cheeses.

Effects of supplementation of maize silage diets with extruded linseed, vitamin E and plant extracts rich in polyphenols, and morning v . evening milking on milk fatty acid profiles in Holstein and Montbéliarde cows

The aim of this study was to evaluate the effects on dairy performance and milk fatty acid (FA) composition of (i) supplementation with extruded linseed (EL), (ii) supplementation with synthetic or natural antioxidants, namely vitamin E and plant extracts rich in polyphenols (PERP), (iii) cow breed (Holstein v. Montbéliarde) and (iv) time of milking (morning v. evening). After a 3-week pre-experimental period 24 lactating cows (12 Holstein and 12 Montbéliarde) were divided up into four groups of six cows: the first group received a daily control diet (diet C) based on maize silage. The second group received the same diet supplemented with EL (diet EL, fat level approximately 5% of dietary dry matter (DM)). The third group received the EL diet plus 375 IU/kg diet DM of vitamin E (diet ELE). The fourth group received the ELE diet plus 10 g/kg diet DM of a PERP mixture (diet ELEP). Compared with the diet C, feeding EL-rich diets led to lower concentrations of total saturated FA (SFA) and higher concentrations of stearic and oleic acids, each trans and cis isomer of 18:1 (except c12-18:1), non-conjugated isomers of 18:2, some isomers (c9t11-, c9c11- and t11t13-) of conjugated linoleic acid (CLA), and 18:3n-3. The vitamin E supplementation had no effect on milk yield, milk fat or protein percentage and only moderate effects on milk concentrations of FA (increase in 16:0, decreases in 18:0 and t6/7/8-18:1). The addition of PERP to vitamin E did not modify milk yield or composition and slightly altered milk FA composition (decrease in total saturated FA (SFA) and increase in monounsaturated FA (MUFA)). The minor effects of vitamin E may be partly linked to the fact that no milk fat depression occurred with the EL diet. During both periods the Holstein cows had higher milk production, milk fat and protein yields, and milk percentages of 4:0 and 18:3n-3, and lower percentages of odd-branched chain FA (OBCFA) than the Montbéliarde cows. During the experimental period the Holstein cows had lower percentages of total cis 18:1, and c9,c11-CLA, and higher percentages of 6:0, 8:0, t12-, t16/c14- and t13/14-18:1, and 18:2n-6 than Montbéliarde cows because of several significant interactions between breed and diet. Also, the total SFA percentage was higher for morning than for evening milkings, whereas those of MUFA, total cis 18:1, OBCFA and 18:2n-6 were lower. Extruded linseed supplementation had higher effect on milk FA composition than antioxidants, breed or time of milking.

Plant polyphenols associated with vitamin E can reduce plasma lipoperoxidation in dairy cows given n-3 polyunsaturated fatty acids

Diets rich in n-3 polyunsaturated fatty acids (PUFA) improve the nutritional value of ruminant products but also increase the risk of lipoperoxidation in plasma and tissues. The relative effectiveness of dietary antioxidants such as vitamin E (vit E) given alone or with plant extracts rich in polyphenols (PERP) containing rosemary, grape, citrus, and marigold was investigated in the plasma of mid-lactation dairy cows given diets enriched in 18:3 n-3. For a 30-d period, the animals were given a maize silage-based diet (control group C, n = 6) or the same basal diet supplemented with extruded linseed rich in 18:3 n-3 [50 g of oil/kg of diet dry matter (DM); group L, n = 6], extruded linseed + vit E (375 international units/kg of diet DM; 7,500 IU/cow per day; group LE, n = 6), or extruded linseed + vit E + PERP (10 g/kg of diet DM; group LEP, n = 5). Plasma susceptibility to lipoperoxidation was evaluated using in vitro parameters of conjugated diene formation (lag phase and maximum oxidation rate). Plasma indicators of lipoperoxidation and antioxidant status were analyzed in the 4 experimental groups as well as the fatty acid (FA) composition of total plasma lipids. At d 30, group L significantly increased plasma cholesterol esters (+57%) and phospholipids (+35%) compared with group C. It also increased plasma n-3 PUFA (4.7-fold increase) to the detriment of n-6 PUFA (-30%), leading to a higher peroxidizability index (+20%). Plasma in vitro lipoperoxidation was higher in group L (rich in 18:3 n-3) than in group C. Vitamin E alone had no effect on lipoperoxidation, whereas vit E in association with PERP lowered lipoperoxidation by increasing the resistance time against peroxidation (+47%) and by decreasing the oxidation rate (-48%) compared with group L at d 30. Surprisingly, in vivo plasma lipoperoxidation estimated by the plasma level of the major lipoperoxidation product (malondialdehyde) was not significantly increased in group L. This study shows, for the first time, that PERP supplied in association with vit E were able to reduce lipoperoxidation in lactating cows given a diet rich in 18:3 n-3, thereby helping to protect cows against the deleterious consequences of lipoperoxidation and potentially ensuring antioxidant potential for 18:3 n-3-enriched dairy products.

Ultraviolet-absorbing compounds in milk are related to forage polyphenols

The aim of this work was to characterize UV-absorbing compounds (UAC) in milk in relation to diet. In winter, 4 groups of cows each received a different diet: concentrate rich containing 35% cocksfoot hay (CCH), maize silage (MS), rye grass silage (RS), or rye grass hay (RH). In summer, 2 additional diets were given: mountain grassland hay (GH) and mountain grassland pasture (GP). Polyphenols were analyzed by HPLC and Folin reaction on forages and UAC were extracted from milks and analyzed by HPLC. In forages, the number of polyphenols was lowest in MS (57) and greatest in GP (85). Twenty-four peaks were identified, accounting for 28 to 47% peak area at 280 nm. Caffeoyl compounds and flavonoid glycosides were mainly found in RH, GH, and GP. Hydrolyzed compounds such as hydroxycinnamic acids and aglycones were found in MS and RS. Estimated amounts of polyphenols were lowest for MS (3.7 g/kg), roughly similar for CH, RS, and RH (about 15 g/kg), and greatest for GH and GP (21.6 and 35.3 g/kg, respectively). About 230 different peaks were separated in milks. Milks from RH and GP contained the lowest (87) and the greatest (127) numbers of peaks, respectively. Only 10 peaks were identified, accounting for 21 to 54% of the total spectra area. In addition to the major compound hippuric acid, phenylacetic acid, benzoic acid, 4-hydroxybenzoic acid benzaldehyde, catechol, and small amounts of ferulic acid were found in varying amounts depending on the diet. Flavonoids such as quercetin, luteolin, and apigenin were also present. Hippuric acid was clearly related to the presence of caffeoylquinic compounds in forages. Other identified UAC may originate essentially from forage simple polyphenols or from cell wall aromatics. Some of the several unknown compounds may also originate from the transformation of other nutrients. Estimated amounts of UAC were widely variable within each animal group. They were surprisingly high in CCH and roughly similar in all milks from preserved forages (about 3.6 mg/L), with generally greater values for GH milks, whereas the greatest amount was found in GP milks (13.3 mg/L). Hierarchical clustering clearly discriminated the 6 diets, showing that there were major differences in GP milks. Some UAC were specific to one or a group of diets. Ultraviolet-absorbing compounds are therefore a potential tool to distinguish between milks according to diet. In addition, they may have a bioactive effect on milk component conservation or on human health.

Effect of a Hay-Based Diet or Different Upland Grazing Systems on Milk Volatile Compounds

The effect of animal feeding on milk volatile organic compounds (VOCs) of metabolic origin was tested on a hay-based diet (H), a highly diversified pasture under continuous grazing (CG), or a less diversified pasture under rotational grazing (RG). Individual milk of 24 Montbéliarde cows (8 per treatment) were sampled after 2 weeks. Pasture-derived milk was richer (p < 0.05) in camphene, sabinene, β-caryophyllene, and skatole than H milk. Neither milk yield nor fat content affected the majority of VOCs measured. Skatole increased slightly with milk yield, while indole and cineole decreased slightly with milk fat content but with poor regression (R(2) < 0.54). Multivariate analysis showed that, on the basis of those VOCs of metabolic origin whose concentration differed between treatment (dimethyl-sulfone, skatole, toluene, undecanoic acid, 1-octadecene, benzeneacetaldehyde, octanoic acid, and 2-pentanone-4-hydroxy-4-methyl), it was possible to obtain good discriminations among feeding systems. This study is promising for a future use of VOCs of metabolic origin to trace animal feeding systems.

Yield and sensory properties of cheese made with milk from Holstein or Montbéliarde cows milked twice or once daily

The aim of this study was to evaluate the milk properties and the yield and sensory properties of Cantal cheese made with milk from Holstein or Montbéliarde cows milked once or twice daily. Sixty-four grazing cows [32 Holstein (H) and 32 Montbéliarde (M) cows] in the declining phase of lactation (157 d in milk) were allocated to 1 of 2 equivalent groups milked once daily (ODM) or twice daily (TDM) for 7 wk. The full-fat raw milk collected during 24 h from the 4 groups of cows (M-TDM, M-ODM, H-TDM, and H-ODM) was pooled and processed into Cantal cheese 4 times during the last 4 wk of the experimental period. In all, 16 cheeses were made (2 milking frequencies x 2 breeds x 4 replicates) and analyzed after a ripening period of 15 and 28 wk. The results showed that for both breeds, the pooled milk content of fat, whey protein, casein, total protein, and phosphorus as well as rennet clotting time and curd firming time were significantly higher with ODM cows, whereas the casein-to-total protein ratio was lower, and lactose, urea, calcium, and free fatty acids contents of milk remained unchanged. The acidification and draining kinetics of the cheese as well as cheese yields and the chemical and rheological properties of the ripened cheese were not significantly modified by milking frequency. For both breeds, the cheeses derived from ODM cows had a slightly yellower coloration but the other sensory attributes, except for pepper odor, were not significantly affected by milking frequency, thereby demonstrating that ODM does not have an adverse effect on the sensory properties of Cantal cheese. Compared with that of Holstein cows, milk from Montbéliarde cows resulted in a higher cheese yield (+1.250 kg/100 kg of milk) and ripened cheeses with lower pH, dry matter, calcium, sodium chloride, and water-soluble nitrogen concentrations. These cheeses had also a less firm and more elastic texture, a more acidic taste, and a yogurt/whey aroma.

Effect of genetic potential and level of feeding on milk protein composition

Two groups of 15 multiparous cows in mid-lactation were used in a Latin square design experiment with 4-week experimental periods. The genetic milk protein concentration level was high in the first group and low in the second. Each group of cows was given in a random order three feeding levels that covered 85, 100 and 115% of energy requirements and 90, 110 and 125% of nitrogen requirements, respeetively. In both groups, increasing level of feeding induced a significant increase in milk yield (+ 2.4 kg/d between lowest and highest levels) and in protein concentration (+ 1.7 g/kg). The proportion of paracasein in total proteins was not altered by either genetics or nutrition. The proportion of casein in total proteins was slightly increased by 0.5 percentage points (P < 0.05) with the intermediate level of feeding. Plasmin and plasminogen activities were not significantly modified by the genetic milk concentration level. Plasmin activity significantly increased with nutrient supplementation, but only in animals of low genetic potential (+ 21% between low and high levels, P < 0.01). Casein composition was not significantly altered by the genetics or level of nutrition. Over the whole range of individual measurements taken (n = 90), the relationships between casein or paracasein and total protein concentrations were linear and very narrow (R2 = 0.92 and 0.95, respectively). The proportion of casein or paracasein in total proteins significantly decreased as plasmin activity increased.

Effects of hay quality on intake, growth path, body composition and muscle characteristics of Salers heifers

A comparison between continuously (CG group, n = 9) and discontinuously (DG, n = 14) growing Salers heifers during a two year growth period after weaning was performed. Feed was available to all animals ad libitum throughout the experiment. Growth differences in the winter resulted from a different quality of the offered hay. In the summer, the animals were conducted indoors and offered the same good quality hay. Serial slaughter was carried out in order to estimate the evolution of body composition and muscle characteristics (fibre type and area, collagen) which may influence meat quality. This experimental scheme made it possible to simulate two types of nutritional environment (poor and rich) and to study their impact on intake, growth, body composition and muscle characteristics of the animals. DG heifers always underwent a summer compensatory growth, even though not complete, when compared with CG animals. The final slaughter was carried out at the same live weight, approximately 700 kg. On average, DG heifers were therefore slaughtered 56 days later than CG animals. The differences in mean daily weight gains always neared 300 g.d–1, respectively in favour of CG in the winter and DG in the summer. Growth compensation was attributable to an increased intake (between +6 and +7%) in the summer and a tendency for a higher growth efficiency of DG animals. No significant major difference was detected between CG and DG body composition at the final slaughter at which final carcass was approximately 400 kg and total adipose tissue weight reached approximately 130 kg (21.5% of the empty body weight). Final muscle characteristics were not modified by growth type either. It was concluded that growth path can vary according to food availability, without affecting the characteristics of the finished carcasses at constant weight. growth path / heifer / body composition / muscle characteristics / hay intake * Corresponding author: hoch@vet-nantes.fr Present address: UMR ENV Nantes INRA Gestion de la Santé Animale, Atlanpole-Chantrerie, BP 40706, 44307 Nantes Cedex 03, France. Article published by EDP Sciences and available at http://www.edpsciences.org/animres or http://dx.doi.org/10.1051/animres:2005022