This study focuses on extensive grassland-based dairy systems, where cows may be exposed to various hazards (climatic, health...) and limiting environments (feeding conditions) over their life. In such livestock systems, the ability of cows to remain in the herd (i.e. lifespan) reveals their ability to cope with such perturbations and to continue meeting the farmer?s expectations. Productive lifespan was thus considered as a proxy of robustness in dairy cows. We hypothesized that productive lifespan of dairy cows can be predicted by a set of life function traits recorded during first lactation. A dataset composed of variables describing the entire productive life of 185 (Montbe?liarde and Prim?Holstein) dairy cows managed in an experimental farm was used to test our hypothesis. This dataset contained information on 32 variables related to productive and reproductive performances, health status, average daily dry matter intake, body weight and body condition score describing the first lactation of all multiparous dairy cows, together with their productive lifespan (difference between age at culling and age at first calving). Clustering and multi-trait profile analyses of dairy cows revealed the existence of trade-offs between the productive lifespan of dairy cows and milk productivity, fertility and body weight at first lactation. For instance, cows with good functional performance (in terms of health and reproduction traits) but moderate milk production during first lactation had longer productive lifespan, whereas cows with moderate milk production but poor reproductive performance had a shorter one. We applied linear discriminant (LD) modelling technique to predict to which productive lifespan (short, average, long) profile an individual cow would belong, based on life function and production traits measured during the first lactation. K-fold cross-validation (k=4) of the LD model yielded an accuracy of 89% and precision ranged between 89 and 97%. Prediction quality of the cross-validated LD model suggests that our approach of classifying individual dairy cows is relevant and advantageous compared to classifications done per average cluster or profile. Studying traits of cows at first lactation enables early identification of cows that have a greater probability of living longer and thus have a better robustness.

The objective was to assess effects of experimentally induced undernutrition on responses to an intramammary lipopolysaccharide (LPS) challenge in early-lactation cows. Starting at 24 ± 3 d in milk, multiparous Holstein cows either received a ration containing 48% straw for 96 h to restrict nutrient intake (REST, n = 8) or were allowed ad libitum intake of a lactation diet (CONT, n = 9). After 72 h on diet or after an equivalent period for CONT, 50 µg of LPS (Escherichia coli 0111:B4) was injected into one healthy rear mammary quarter to induce an acute inflammation response. Blood samples were collected weekly until 7 wk of lactation, daily during feed restriction (or control), before and at 1, 2, 4, 6, 10, and 24 h relative to LPS injection. Foremilk quarter samples were collected before and at 4, 6, 10, and 24 h after LPS injection. Dry matter intake, milk yield, energy balance, plasma glucose, nonesterified fatty acids (NEFA), and β-hydroxybutyrate (BHB) concentrations did not differ between CONT and REST immediately before nutrient restriction in REST (least squares means at d -1 were 21.8, 39.0 kg/d, -2.5 MJ/d, and 3.78, 0.415, 0.66 mM, respectively) but were significantly altered at 72 h of nutrient restriction (9.8, 28.3 kg/d, -81.6 MJ/d, and 2.77, 1.672, and 2.98 mM, respectively), when the LPS challenge was performed. The rectal temperature increment from baseline values in response to LPS did not differ, but cortisol increment was greater and cortisol response area under the curve (AUC) tended to be greater [202 vs. 122 (ng/mL) × 10 h] for REST than CONT. No treatment differences were observed in foremilk IL-8, IL-1β, tumor necrosis factor-α, and chemokine (C-X-C motif) ligand 3 concentrations in response to LPS injection. Composite milk somatic cell count per milliliter (6.919 × 106 vs. 1.956 × 106 cells/mL) and total number of somatic cells secreted in milk per day were greater for REST than CONT during the day following LPS. Plasma glucose, urea, and insulin concentrations increased after the LPS challenge, suggesting establishment of insulin resistance and modifications of glucose metabolism to support acute inflammation in both CONT and REST. Nonetheless, nutrient-restricted cows had delayed plasma insulin and glucose responses to LPS, smaller insulin AUC but greater glucose AUC compared with CONT, despite the limited nutrient availability to sustain an inflammation response. Undernutrition altered peripheral metabolic responses to an intramammary LPS challenge but had limited effects on selected indicators of inflammation response in early-lactation cows.

Based on the potential benefits for long-term human health, nutritional strategies have been developed in order to increase the milk fat concentrations of bioactive fatty acids (FA) in ruminants. Dietary supplements of fish oil (FO), extruded linseed (EL) or a mixture of EL and FO increase c9,t11-CLA and n-3 PUFA in milk from bovine and caprine. These supplements associated with a high level of starch from concentrates cause milk fat depression in cows, but information for dairy goats is limited. An experiment was performed to investigate the effects of addition of extruded linseed to a diet containing fish oil in interaction with the type and level of starch concentrate on dairy goat performance and milk fatty acid (FA) profile. Following a 2 x 3 factorial design, 72 goats were allocated to 6 experimental diets based on alfalfa hay and with concentrates including fish oil (40 g/d) without or with extruded linseed (360 g/d) and either rich in starch from barley grain or extruded wheat or that were low in starch from barley grain. In contrast to cows, in goats adding extruded linseed to low-or high-starch diets based on hay and containing fish oil increases milk fat content and changes the milk FA composition in particular by increasing some bioactive FA with 18 carbons. In these conditions FA changes were characterized by decreases in SFA (on average 22% decrease) and increases in 18:0, c9-18:1, t11-18:1, c9,t11-CLA and 18:3n-3. The milk t10-18:1 concentration remained low (<1% total FA) and the t11-18:1/t10-18:1 ratio was much higher than in cows fed fish oil with plant oils. The combination of EL and FO induced larger concentrations in t11-18:1 and c9,t11-CLA than FO alone (2.9- and 2.1-fold higher, respectively). The apparent transfer rates of 20:5n-3 and 22:6n-3 from fish oil to milk were lower when EL was added to the diet (on average, 6.6 and 5.4%) compared to FO alone (on average, 8.0 and 7.4%, respectively). Extruded wheat, as the more rapidly degradable starch source in the rumen, decreased milk fat content. Based on the milk FA changes (e.g., c9,t11-CLA,18:2n-6, 18:3n-3, 20:5n-3, 22:6n-3), diets rich in starch from barley grain would induce a lower rumen bacterial biomass and a more extensive biohydrogenation of dietary FA in the rumen than diets rich in starch from extruded wheat. Starch level in the diets had negative effect on milk yield but moderate effects on milk fat and FA content, under these dietary conditions. (C) 2016 Elsevier B.V. All rights reserved.

BACKGROUND:Fatty acid (FA) composition plays a crucial role in milk nutritional quality. Despite the known nutritional regulation of ruminant milk composition, the overall mammary mechanisms underlying this regulation are far from being understood. The aim of our study was to determine nutritional regulation of mammary transcriptomes in relation to the cow milk composition.METHODS:Twelve cows received diets differing in the forage-to-concentrate ratio [high forage (HF) and low forage (LF)] supplemented or not with lipids [HF with whole intact rapeseeds (RS) and LF sunflower oil (SO)] in a 4 × 4 Latin square design. Milk production and FA composition were determined. The gene expression profile was studied using RT-qPCR and a bovine microarray.RESULTS:Our results showed a higher amplitude of milk composition and mammary transcriptome responses to lipid supplementation with the LF-SO compared with the LF diet than with the HF-RS compared with the HF diet. Forty-nine differentially expressed genes, including genes involved in lipid metabolism, were identified with LF-SO versus LF, whereas RS supplementation to the HF diet did not affect the mammary transcriptome.CONCLUSIONS:This study highlights different responses to lipid supplementation of milk production and composition and mammary transcriptomes depending on the nature of lipid supplementation and the percentage of dietary concentrate.

after calving as well as on persistency. Mucus score and DA had a negative impact on milk yield immediately after calving. Consistent with Wood’s estimates, Wilmink’s estimates indi-cated that multiparous cows have higher milk production and lower persistency than primiparous cows. Number of mastitis cases and DA were associated with lower overall milk production and higher persistency. Beta hydroxybutyrate was associated with a higher level of milk yield and lower persistency. The ratio of sire to residual variance estimates from Wood’s and Wilmink’s functions were consistent and approximately (cid:19)(cid:17)(cid:23)(cid:17) Wood’s model offered a better fit for the lactation curves considered(cid:17) Our findings demonstrate the need to incorporate disease indicators on the assessment of the genetic compo-nent influencing the tra(cid:77)ectory of the lactation curve(cid:17) These findings contribute to a long-term multistate pro(cid:77)ect database (USDA-NIFA-AFRI-003542) for direct measures of fertility. retained placenta, lameness, and displacement of abomasum. Clinical endometritis, metritis, lameness, and respiratory problems were lower in summer than winter. Dystocia, retained placenta, and subclinical ketosis were positively and significantly associated with clinical endometritis and metritis. Subclinical ketosis and dystocia were positively and significantly associated with displace ment of abomasum(cid:17) Mastitis was negatively and significantly associated with milk yield at first test-day(cid:17) Heritability esti mates for the diseases ranged from 0.06 (retained placenta) to 0.4 (respiratory problems). The differences in genetic pa-rameter estimates among alternative disease descriptors offer insights into effective approaches to lower the incidence of disease through genetic selection(cid:17) These findings contribute to a long-term multistate project database (USDA-NIFA-A-FRI-003542) for direct measures of fertility. in RES compared with CON, but it was greater for NEFA, BHBA, and glucose. The NEFA nadir post LPS was 599 and 101 µM at 4 h for RES and CON ( P £ 0.001), respectively, and it preceded insulin change in RES. The BHBA decrease in RES was consistent with NEFA response to LPS, but BHBA increased from a low baseline in CON (treatment × time interactions, P £ 0.05). The negative glucose AUC in CON could be related to the insulin increase post LPS. Rectal temperature increase did not differ between treatments (+2.1 ± 0.15°C at 6 h). Nutrient restriction altered peripheral metabolic responses to an intramammary LPS challenge. or absence of an E. coli infection and with or without LAB. Samples were mounted in FESEM stubs and observed without coating in a Zeiss Merlin micro-scope. A qualitative assessment of general structure of the ep-ithelium (size and shape of cells, ultrastructure, and amounts of ultrastructure of microvilli), presence of E. coli and LAB in cell surface, cell debris, presence of mucus in the cell surface, mitochondrial damage, and cell death was performed by the analysis of 10 random selected areas for each treatment. For TEM, contrasted ultrathin sections were observed in a Jeol 1400 operating at 80kV. A semiquantitative approach was performed by the analysis of 10 random selected sections in three areas for each treatment and data were analyzed using a Fisher exact test. Escherichia coli alone or with LAB appeared in low numbers in epithelial cells surface and in no case formed biofilms or interactions between each other(cid:17) Escherichia coli abundance was lower ( P < 0.05) in samples treated with LAB than in those infected with E. coli alone. Healthy epithe-lium was observed in cells treated with LAB (epithelial cells with normal size and shape and normal aspect of microvilli), whereas in cultures infected with E. coli , abundant areas with cell debris and bacilli in epithelial cell surface were observed. The incidence of necrosis (as assessed by TEM) in E. coli samples tended ( P = 0.07) to be greater than in noninfected cultures. Control or LAB preincubated cells showed less mitochondrial damage ( P = 0.01) than nontreated cells, a pa-rameter strongly related to cell death. Overall, LAB appear to offer protection against E. coli , by mechanism different than the formation of biofilms, and thus, LAB combinations could be used as a preventive strategy for metritis.

The objective was to study milk production, body reserve mobilization, metabolic and hormonal profiles, and ovarian cyclicity of Holstein-Friesian (HOLS) and Montbéliarde (MONT) cows under two low-input dairy production systems with seasonal spring calving: an extensive (EXT; 12 HOLS and 12 MONT) based on permanent diversified grasslands and zero concentrate, and a semi-extensive (SEMI; 12 HOLS and 10 MONT) based on established temporary grasslands and up to 4 kg/day of concentrate. Individual measurements were performed between -4 and 12 weeks of lactation. Cows in EXT secreted less milk (22.1 v. 24.4 kg/day), protein (660 v. 755 g/day) and energy (67.7 v. 74.4 MJ/day), had greater plasma β-hydroxybutyrate (BHBA) (0.97 v. 0.69 mM), lower glucose (59.0 v. 62.0 mg/dl) and IGF-1 (62 v. 71 ng/ml), lower milk fat concentration in fatty acids originating from de novo synthesis (e.g. ∑ 10:0 to 15:0) and greater concentration of those derived in part from mobilization of fat reserves (e.g. 18:0 and ∑>C16), and showed greater frequency of abnormal ovarian cycles compared with SEMI. Across production systems, HOLS produced more milk (24.7 v. 21.8 kg/day), protein (738 v. 674 g/day) and fat (939 v. 819 g/day), secreted more energy (75.1 v. 67.0 MJ/day), lost more body condition score (BCS) (1.41 v. 1.03) and reached a lower BCS nadir (1.12 v. 1.43), had greater plasma BHBA (0.91 v. 0.75 mM), lower insulin (15.9 v. 17.2 µIU/ml) and tended to have lower glucose (59.6 v. 61.4 mg/dl), had lower milk fat concentration in ∑ 10:0 to 15:0, tended to have higher ∑>C16 and tended to show more abnormal estrous cycles compared with MONT. Ultrasound measurements did not differentiate fat mobilization and were confounded by breed differences of skin thickness. The greater nutrient allowance in SEMI improved indicators of physiological status and ovarian function during early lactation compared with EXT, but did not attenuate body reserve mobilization because cows prioritized milk secretion. HOLS secreted more nutrients than MONT but lost more BCS, which negatively affected nutritional balance and tended to affect ovarian cyclicity during early lactation. Breed by system interactions were not observed except for a few variables.

A study with 2 ruminant species (goats and cows) with inherent differences in lipid metabolism was performed to test the hypothesis that milk fat depression (MFD) due to marine lipid supplements or diets containing high amounts of starch and plant oil is caused by different mechanisms and that each ruminant species responds differently. Cows and goats were allocated to 1 of 3 groups (4 cows and 5 goats per group) and fed diets containing no additional oil (control) or supplemented with fish oil (FO) or sunflower oil and wheat starch (SOS) according to a 3 × 3 Latin square design with 26-d experimental periods. In cows, milk fat content was lowered by FO and SOS (-31%), whereas only FO decreased milk fat content in goats (-21%) compared with the control. Furthermore, FO and SOS decreased milk fat yield in cows, but not in goats. In both species, FO and SOS decreased the secretion of C16 FA output. However, SOS increased milk secretion of >C16 FA in goats. Compared with the control, SOS resulted in similar increases in milk trans-10,cis-12 conjugated linoleic acid (CLA) in both species, but caused a 2-fold larger increase in trans-10 18:1 concentration in cows than for goats. Relative to the control, responses to FO in both species were characterized by a marked decrease in milk concentration of 18:0 (-74%) and cis-9 18:1 (-62%), together with a ~5-fold increase in total trans 18:1, but the proportionate changes in trans-10 18:1 were lower for goats. Direct comparison of animal performance and milk FA responses to FO and SOS treatments demonstrated interspecies differences in mammary lipogenesis, suggesting a lower sensitivity to the inhibitory effects of trans-10,cis-12 CLA in goats and that ruminal biohydrogenation pathways are more stable and less prone to diet-induced shifts toward the formation of trans-10-containing intermediates in goats compared with cows. Even though a direct cause and effect could not be established, results suggest that regulation of milk fat synthesis during FO-induced MFD may be related to a shortage of 18:0 for endogenous mammary cis-9 18:1 synthesis, increase in the incorporation of trans FA in milk triacylglycerols, and limitations in the synthesis of FA de novo to maintain milk fat melting point. However, the possible contribution of biohydrogenation intermediates with putative antilipogenic effects in the mammary gland, including trans-9,cis-11 CLA, trans-10 18:1, or cis-11 18:1 to FO-induced MFD cannot be excluded.

Based on the potential benefits for long-term human health, there is interest in developing sustainable nutritional strategies for lowering medium-chain saturated fatty acids (FA) and increasing specific unsaturated FA in ruminant milk. Dietary supplements of extruded linseeds (EL), fish oil (FO) or a mixture of EL and FO increase cis-9,trans-11 CLA and long-chain n-3 polyunsaturated FA in bovine milk. Supplements of FO cause milk fat depression in lactating cows, but information for dairy goats is limited. A total of 14 Alpine goats were used in a replicated 3×3 Latin square with 28-days experimental periods to examine the effects of EL alone or in combination with FO on animal performance, milk fat synthesis and milk FA composition. Treatments comprised diets based on natural grassland hay supplemented with no additional oil (control), 530 of EL or 340 g/day of EL and 39 g/day of FO (ELFO). Compared with the control, ELFO tended (P=0.08) to lower milk fat yield, whereas EL increased (P<0.01) milk fat content and yield (15% and 10%, respectively). Relative to EL, ELFO decreased (P<0.01) milk fat content and yield (19% and 17%, respectively). Relative to the control and ELFO, EL decreased (P<0.05) milk 10:0 to 16:0 and odd- and branched-chain FA content and increased 18:0, cis-18:1, trans-13 18:1 (and their corresponding ∆-9 (desaturase products), trans-12,cis-14 CLA, cis-13,trans-15 CLA, cis-12,trans-14 CLA and trans-11,cis-13 CLA and 18:3n-3 concentrations. ELFO was more effective for enriching (P<0.05) milk cis-9, trans-11 CLA and trans-11 18:1 concentrations (up to 5.4- and 7.1-fold compared with the control) than EL (up to 1.7- and 2.5-fold increases). Furthermore, ELFO resulted in a substantial increase in milk trans-10 18:1 concentration (5.4% total FA), with considerable variation between individual animals. Relative to the control and EL, milk fat responses to ELFO were characterized by increases (P<0.05) in milk trans-16:1 (Δ9 to 11), trans-18:1 (Δ6 to 11), trans-18:2, CLA (cis-9,trans-11, trans-9,cis-11, trans-8,trans-10 and trans-7,trans-9) and 20- and 22-carbon FA concentrations. Overall, EL resulted in a relatively high cis-9 18:1 concentration and an increase in the 18:3n-3/18:2n-6 ratio, whereas combining EL and FO resulted in substantial increases in trans-FA, marginal enrichment in 20:5n-3 and 22:6n-3 and lower 16:0 concentration changes associated with a decrease in milk fat content. In conclusion, data provide further evidence of differential mammary lipogenic responses to diet in the goat compared with the cow and sheep.

Two experiments were performed to investigate the effects of supplementing a diet with fish oil either alone or with plant oils on dairy goat performance and milk fatty acid (FA) profile (Experiment 1), and the interaction between fish oil with the type and level of starch concentrate (Experiment 2). In Experiment 1, 84 goats were allocated to 7 experimental diets without a lipid supplement or with a low or high dose of fish oil (20 or 40 g/d, respectively) either alone or with linseed or sunflower-seed oils (the combinations included 130 g/d of oil supplements). In Experiment 2,72 goats were allocated to 6 experimental diets without a lipid supplement and with a concentrate rich in corn and barley grain starch or with the high dose of fish oil (40 g/d) and concentrates rich in starch from barley grain, corn grain or both; or that were low in starch from barley grain or corn grain. In contrast to cows, in goats, fish oil supplements modulated milk FA composition without decreasing the milk fat content; this result may have been related to specific milk FA responses, such as a lack of or a small reduction in 18:0 and c9-18:1 (Experiment 1) or a moderate reduction compensated through increases in short-chain FA (Experiment 2) and limited increases in t10-18:1. The combinations of fish oil with sunflower-seed oil were more efficient than either fish oil plus linseed oil or fish oil alone at increasing (P<0.05) milk c9,t11-18:2 and t11-18:1 concentrations (up to 24- and 35-fold increases, respectively), simultaneously decreasing (P<0.05) medium-chain saturated FA (on average, 40% decrease). Based on the milk FA changes (e.g., 18:2n-6, 18:3n-3, t11-18:1 and 18:0) in Experiment 2, diets rich in barley grain starch with fish oil would induce less extensive ruminal dietary FA biohydrogenation and better inhibit the trans 18:1 reduction than diets that are supplemented with the same level of fish oil but are low in barley grain starch or rich in corn grain starch. The apparent transfer rates of 20:5n-3 and 22:6n-3 from fish oil to milk were low (on average, 2.8% and 2.4%, respectively; Experiment 1) but were slightly higher in barley-grain treatments (on average, 5.1% and 7.6%, respectively) compared with corn-grain-only treatments (on average, 2.5% and 3.7%, respectively; Experiment 2). The milk t10-18:1 concentration remained low (<= 1.1% total FA) and the t10-18:1/t11-18:1 ratio was much lower than in cows fed fish oil with plant oils. (C) 2014 Elsevier B.V. All rights

The current short review summarizes recent data on the specificities of goats compared with cows, of milk fatty acid (FA) secretion and milk fat lipolysis responses to physiological and nutritional factors. The influence of lactation stage on milk fat yield and FA composition is similar between goats and cows. In contrast, changes in milk fat yield and composition to diet, lipid supplements in particular, differs between the two ruminant species. In almost all cases, dietary lipid supplements increase milk fat content in goats, but not in cows. The goat is much less sensitive to diet-induced alterations in ruminal biohydrogenation pathways causing trans-10 18:1 to replace trans-11 18:1 as the major intermediate relative to the cow. Mammary lipid secretion in the goat is also less sensitive to the anti-lipogenic effect of trans-10,cis-12 conjugated linoleic acid (CLA) compared with the cow. Consistent with these observations, mammary lipogenic gene expression is less affected by diets rich in starch and polyunsaturated FA (PUFA) in goats than cows. However, diets containing PUFA induce much greater changes in delta-9 desaturase gene expression in goats compared with cows, that may be related to differences in the availability of biohydrogenation intermediates at the mammary glands (e.g. trans-9,trans-11-CLA). The development of either goat flavour or rancidity is related to the inherent peculiarities of milk FA composition and lipolytic system in this species. In contrast with cows, milk LPL activity and lipolysis are low during early and late lactation in goats, and are decreased when animals are underfed or receive a diet supplemented with plant oils. In goats the alpha-s1-casein (CSN1S1) gene polymorphism is associated with a decrease in milk fat content and 8:0–12:0 concentrations in the low CSN1S1 genotype. Conversely, milk fat product/substrate concentration ratios for delta-9 desaturation and spontaneous lipolysis are increased in the low genotype.

Near infrared reflectance spectroscopy (NIRS) was used to predict the goat milk fatty acid (FA) profile. The ability of cow milk broad-based calibration equations to predict the goat milk FA profile was assessed. Three hundred twenty-eight samples in the calibration set and 108 in the validation set were analyzed. We showed that the bias and unexplained error were significant for most of the FA despite an adequate standardized Mahalanobis distance (index to establish the boundaries of a population of samples) which allowed us to test the ability of bovine models to predict goat milk FA profiles. To better predict the goat milk FA composition, a specific goat model was investigated. The cross-validation coefficient of determination (R2CV; proportion of variance explained by the model in cross-validation) and residual predictive deviation (RPD; index which allows to standardize the standard error of prediction (SEP)) were >0.90 and 3, for saturated, monounsaturated, and unsaturated FA, total trans FA, isomer cis9trans11 of CLA, cis9-, trans10-, and trans11-C18:1, respectively. Monitoring of the equation performance of milk FA included the calculation of the bias and unexplained error. Practical applications: In this work, we evaluated the ability of NIRS to predict FA composition of goat milk and tested the ability of using broad-based cow milk calibration equations to monitor an independent set of goat milk samples. We tested the hypothesis that the calibration equations obtained for FA from cow milk could be applied on goat milk. As the spectra of goat milk are similar to those of cow milk when they are measured by the standardized Mahalanobis distance (index to establish the boundaries of a population of samples), we can accept the hypothesis. It will be possible to use the existing calibration equations for predicting FA profile on spectra of milk of a different specie. However, the rejection of the hypothesis would put in doubt the use of Mahalanobis distance as the unique index for testing the performance of calibration equations on different milk populations for predicting FA.

This study compares two groups of 23 and 24 goats with different CSN1S1 genotypes, matched for lactation number and stage. During the first experimental period (4 weeks) half of the goats of each genotype received the control diet (CT) and the second half received a similar diet containing extruded linseed (EL diet). During the second experimental period, the two groups of goats were switched from the CT to the EL diet and from the EL to the CT diet, respectively. Results confirm the lower milk protein (−4.8g/kg) and fat (−6.5g/kg) concentrations in the low genotype group, whereas milk yield was slightly higher (+0.49kg/d) and lactose concentration was unchanged. Between the genotype groups, there were differences in milk fat proportions of at least 25 FAs, particularly the C7 to C13 saturated FAs and C16:0, C18:0, C18:2n-6 and cis9,trans11-C18:2 acids. In addition, delta-9 desaturation ratios were higher in the low CSN1S1 group for C10:0, C14:0, C18:0, trans11-C18:1 and trans13-C18:1. This strongly suggests an effect on mammary delta-9 desaturase activity, especially for C18:0 and trans11-C18:1. It is likely that higher desaturation ratios in the low genotype, as well as observed changes in other FAs, could compensate for the lower synthesis of medium-chain FAs (C7:0–C13:0), thus contributing to maintenance of the melting point of milk fat in this genotype. The effect of the EL diet on milk FA proportions was highly significant for almost all FAs, along with increased milk fat content and decreased post-milking free FA concentration. Numerous interactions (significant but of limited quantitative extent) between the CSN1S1 genotype and EL feeding were shown on milk composition, including 26 FA proportions or delta-9 desaturation ratios, and post-milking free FA concentration.

The potential benefits on human health have prompted an interest in developing nutritional strategies for reducing saturated and increasing specific unsaturated fatty acids (FA) in ruminant milk. The impact of the level and type of starchy concentrate added to diets supplemented with sunflower-seed oil on caprine milk FA composition and on mammary, omental and perirenal adipose, and liver lipid metabolism was examined in fourteen Alpine goats in a replicated 3 × 3 Latin square with 21 d experimental periods. Treatments were a grass hay-based diet with a high level of forage (F) or a high level of concentrate with either maize grain (CM) or flattened wheat (CW) as source of starch and supplemented with 130 g/d sunflower-seed oil. Milk yield was enhanced (P<0·01) and milk fat content was decreased on the CM and CW diets compared with the F diet, resulting in similar milk fat secretion. Both high-concentrate diets increased (P<0·05) milk yield of 10 : 0-16 : 0 and decreased trans-9,11-18 : 1 and cis-9, trans-11-18 : 2. The CW diet decreased (P<0·05) the output of ΣC18 and Σcis-18 : 1 and increased (P<0·05) the output of trans-10-18 : 1 in milk. The expression and/or activity of fourteen proteins involved in the major lipogenic pathways in mammary tissues and of lipogenic genes in adipose and liver tissues were similar among treatments. In conclusion, high starch concentrates alter milk FA yield via mechanisms independent of changes in mammary, liver or adipose tissue lipogenic gene expression. Furthermore, data provided indications that mammary lipogenic responses to starch-rich diets differ between caprine and bovine ruminants.

This review gives an update of available data on the effect of nutrition on milk fatty acid (FA) composition in dairy cow and goat. It starts by an overview of the main digestive and metabolic pathways involved in the milk fat secretion processes. Used data are originated from literature and from two databases developed by Inra. Altogether, analyses confirm the wide plasticity of milk FA profiles in dairy ruminant, peculiarly for the saturated FA (10 to 18 carbon), oleic (9c-18:1) and vaccenic (11t-18:1) acids, and other trans isomers of 18:1 and 18:2. Compared to diets with large amount of concentrate and/or maize silage, grass-based diets (grazed or correctly preserved) show a decrease in saturated FA, at the expense of 9c- and 11t-18:1, and to a lesser extent, 18:3 n-3 and 9c11t-CLA. Dietary supplements of plant oil or oilseeds have similar effects than grass feeding, sometimes more marked, but they increase simultaneously other trans isomers of 18:1 and 18:2, especially when added to maize silage and/or high-concentrate diets. Oils or seeds rich in 18:2 n-6 (sunflower, soybean,…) increase particularly 10t-18:1, and 10t12c-, 8t10c-, 7t9c- and 9t11c-CLA, whereas those rich in 18:3 n-3 (linseed) enhance notably 13t/14t-18:1, and 9ct12-, 9ct13- and 11tc15-18:2. When comparing goats’ with cows’ results, it appears that they are less sensitive to the 11t- to 10t- ruminal shift, thus explaining the good stability and the large magnitude of the responses of their milk 11t-18:1 and 9c11t-CLA content to lipid supplementation of high-concentrate diets. Furthermore, goats seem to respond better than cows to 18:3 n-3 rich supplements. Ongoing studies are evaluating the use of milk FA profile as biomarkers for the authentication of milk according to production zone and type of feeding, or to predict methane enteric emissions by dairy cows receiving oilseeds. Future studies should also integrate the expected progress of knowledge on the potential effects on consumers of the different major and minor FA found in standard or modified dairy products, as well as putative secondary effects of feeding conditions on sensory quality of dairy products and ruminant health.

This review gives an update of available data on the effect of nutrition on milk fatty acid (FA) composition in dairy cow and goat. It starts by an overview of the main digestive and metabolic pathways involved in the milk fat secretion processes. Used data are originated from literature and from two databases developed by Inra. Altogether, analyses confirm the wide plasticity of milk FA profiles in dairy ruminant, peculiarly for the saturated FA (10 to 18 carbon), oleic (9c-18:1) and vaccenic (11t-18:1) acids, and other trans isomers of 18:1 and 18:2. Compared to diets with large amount of concentrate and/or maize silage, grass-based diets (grazed or correctly preserved) show a decrease in saturated FA, at the expense of 9c- and 11t-18:1, and to a lesser extent, 18:3 n-3 and 9c11t-CLA. Dietary supplements of plant oil or oilseeds have similar effects than grass feeding, sometimes more marked, but they increase simultaneously other trans isomers of 18:1 and 18:2, especially when added to maize silage and/or high-concentrate diets. Oils or seeds rich in 18:2 n-6 (sunflower, soybean,.) increase particularly 10t-18:1, and 10t12c-, 8t10c-, 7t9c- and 9t11c- CLA, whereas those rich in 18:3 n-3 (linseed) enhance notably 13t/14t-18:1, and 9ct12-, 9ct13- and 11tc15- 18:2. When comparing goats' with cows' results, it appears that they are less sensitive to the 11t- to 10t- ruminal shift, thus explaining the good stability and the large magnitude of the responses of their milk 11t- 18:1 and 9c11t-CLA content to lipid supplementation of high-concentrate diets. Furthermore, goats seem to respond better than cows to 18:3 n-3 rich supplements. Ongoing studies are evaluating the use of milk FA profile as biomarkers for the authentication of milk according to production zone and type of feeding, or to predict methane enteric emissions by dairy cows receiving oilseeds. Future studies should also integrate the expected progress of knowledge on the potential effects on consumers of the different major and minor FA found in standard or modified dairy products, as well as putative secondary effects of feeding conditions on sensory quality of dairy products and ruminant health.

The potential benefits on human health have prompted an interest in developing nutritional strategies for specifically increasing rumenic acid (RA) in ruminant milk. The aims of the present study were to (i) compare two dietary treatments with lipid supplements on milk yield and composition, (ii) measure the in vivo delta9-desaturation of vaccenic acid (VA) to RA using 13C-labelled VA and (iii) determine the effect of the dietary treatments on this variable. Treatments were 90 g sunflower-seed oil (SO) per d or 60 g sunflower-seed oil and 30 g fish oil per d plus additional starch (SFO), in a grassland hay-based diet given to eight Alpine goats in a 2 x 2 cross-over design with 21 d experimental periods. Milk yield and composition were similar between treatments. Goats fed SFO had higher milk 6 : 0-16 : 0 concentration, lower milk sigmaC18 concentrations and showed no effect on milk VA and RA, compared with SO. At the end of the experiment, intravenous injection of 1.5 g [13C]VA followed by measurements of milk lipid 13C enrichment showed that in vivo 31.7 and 31.6 % of VA was delta9-desaturated into milk RA in the caprine with the SO and SFO treatments, respectively. The expression of genes encoding for delta9-desaturase (or stearoyl-CoA desaturase; SCD1, SCD5) in mammary tissues and four milk delta9-desaturation ratios were similar between treatments. In conclusion, the present study provides the first estimates of in vivo endogenous synthesis of RA (63-73 % of milk RA) from VA in goats, and shows no difference between the two lipid supplements compared.

This review gives an update of available data on the effect of nutrition on milk fatty acid (FA) composition in dairy cow and goat. It starts by an overview of the main digestive and metabolic pathways involved in the milk fat secretion processes. Used data are originated from literature and from two databases developed by INRA. Altogether, analyses confirm the wide plasticity of milk FA profiles in dairy ruminant, peculiarly for the saturated FA (10-18 carbon), oleic (9c-18: 1) and vaccenic (11t-18: 1) acids, and other trans isomers of 18: 1 and 18: 2. Comparing effects of diets with large amount of concentrate and/or maize silage with grass-based diets (grazed or correctly preserved) shows a decrease in saturated FA, at the expense of 9cand 11t-18: 1, and to a lesser extent, 18: 3 n-3 and 9c11t-CLA. Dietary supplements of plant oil or oilseeds have similar effects, sometimes more marked, but they increase simultaneously other trans isomers of 18: 1 and 18: 2, especially when added to maize silage and/or high-concentrate diets. Oils or seeds rich in 18: 2 n-6 (sunflower, soybean...) increase particularly 10t-18: 1, and 10t12c-, 8t10c-, 7t9c-and 9t11c-CLA, whereas those rich in 18: 3 n-3 (linseed) enhance notably 13t/14t-18: 1, and 9ct12-, 9ct13-and 11tc15-18: 2. When comparing goats' with cows' results, it seems that they are less sensitive to the 11t-to 10t-ruminal shift, thus explaining the good stability and the large magnitude of the responses of their milk 11t-18: 1 and 9c11t-CLA content to lipid supplementation of high-concentrate diets. Furthermore, goats seem to respond better than cows to 18: 3 n-3 rich supplements. Ongoing studies are evaluating the use of milk FA profile as biomarkers for the authentication of milk according to production zone and type of feeding, or to predict methane enteric emissions by dairy cows receiving oilseeds. Future studies should also integrate the expected progress of knowledge on the potential effects on consumers of the different major and minor FA found in standard or modified dairy products, as well as putative secondary effects of feeding conditions on sensory quality of dairy products and ruminant health. (C) 2010 Published by Elsevier Masson SAS on behalf of Societe francaise de nutrition.