Role of trans fatty acids in the nutritional regulation of mammary lipogenesis in ruminants

Dietary combination of linseed and hazelnut skin as a sustainable strategy to enrich lamb with health promoting fatty acids

This study investigated the effect of the inclusion of extruded linseed and hazelnut skin on fatty acid (FA) metabolism in finishing lambs. Forty lambs were divided into 4 groups and fed for 60 d with: a conventional cereal-based diet, or the same diet with 8% of extruded linseed, or 15% of hazelnut skin, or 4% of linseed plus 7.5% of hazelnut skin as partial replacement of maize. Dietary treatments did not affect growth performances, carcass traits, and ruminal fermentation. The combined effect of linseed and hazelnut skin enriched the intramuscular fat with health promoting FA. Particularly, increases in α-linolenic acid (3.75-fold), and very long-chain n-3 poly-unsaturated FA (+ 40%) were attributed to the supplementation with linseed, rich in α-linolenic acid. In addition, increases in rumenic (+ 33%), and vaccenic (+ 59%) acids were attributed to hazelnut skin tannins modulating ruminal biohydrogenation and accumulating intermediate metabolites. The simultaneous inclusion of linseed and hazelnut skin can be a profitable strategy for enriching the intramuscular fat of lambs with health promoting FA, without adverse effects on ruminal fermentation and animal performance.

Effect of Dietary Eicosapentaenoic and Docosahexaenoic Fatty Acid Supplementation during the Last Month of Gestation on Fatty Acid Metabolism and Oxidative Status in Charolais Cows and Calves

Fatty acids (FAs) are of utmost importance in the peripartal period for the development of the central nervous and immune systems of the newborn. The transport of polyunsaturated fatty acids (PUFAs) through the placenta is considered to be minimal in ruminants. Nevertheless, the cow's FAs are the main source of FAs for the calf during gestation. This research aimed to investigate the influence of low-dose eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation during late gestation on the FA metabolism of cows and their calves. A total of 20 Charolais cows during the last month of their gestation were included in the feeding trial and were divided into a control group (CON) and an experimental group (EPA + DHA). The latter received a supplement in the amount of 100 g/day (9.1 and 7.8 g/cow/day of EPA and DHA, respectively). Supplementation of low-dose EPA and DHA alters colostrum and milk fatty acid composition through the elevation of n-3 long-chain polyunsaturated fatty acids (LC-PUFAs) without affecting milk fat and protein concentrations and oxidative status. Plasma composition in cows was significantly altered, while the same effect was not detected in calf plasma. No significant change in mRNA expression was detected for the genes fatty acid synthase (FASN) and acetyl-CoA carboxylase alpha (ACACA).

Effects of dietary forage-to-concentrate ratio and forage type on milk phospholipids and fatty acid composition of polar lipids

The effects of grass silage and red clover silage on milk fatty acid (FA) composition are extensively studied, but little is known of their effects on minor lipid constituents of milk fat globule membrane. We investigated the effects of forage:concentrate (FC) ratio in grass silage-based diets and forage type (grass silage vs. red clover silage) on selected molecular species of milk phospholipids (PL) and the FA composition of PL. Ten multiparous Nordic Red cows were offered following dietary treatments: grass silage-based diets containing 70:30 (HG) or 30:70 (LG) FC ratio or a red clover silage-based diet (RC) comprising 50:50 FC ratio on a dry matter basis. The most abundant molecular species within the phosphatidylcholines was 16:0-18:1 phosphatidylcholine that was increased by 18% in HG compared with LG milk. Dietary treatments did not affect the relative proportion of 18:1-18:1+18:0-18:2 phosphatidylethanolamine that was the most prevalent species (ca. 44%-45%) in that class. We identified the d18:1-22:0 sphingomyelin as the most abundant sphingomyelin species that tended to increase in HG milk compared with LG. The FC ratio did not affect the relative proportions of saturated FA nor monounsaturated FA in PL, but the proportion of cis-9 18:1 was elevated in HG versus LG milk, whereas the proportion of 18:2n-6 was 50% higher in LG versus HG milk. The RC diet increased monounsaturated FA and 18:3n-3 levels in PL compared with grass silage-based diets and decreased the relative proportion of saturated FA. However, the RC diet did not affect the relative proportion of polyunsaturated FA in PL, although red clover silage typically increases the proportion of polyunsaturated FA in milk fat. This study provides valuable knowledge of the minor lipid components in milk on species level in relation to common feeding strategies in high-forage systems.

Impacts of red clover and sainfoin silages on the performance, nutrient utilization and milk fatty acids profile of ruminants: A meta-analysis

Inclusion of plants rich in secondary metabolites into grass ensiling offers multiple benefits for ruminants, from improving productive performance to health-promoting effects as well as helping to reduce environment pollution. The present meta-analysis summarizes the dietary inclusion levels of red clover silage (RCS) and sainfoin silages (SS) as well as the types of silages fed to dairy cows and small ruminants. A total of 37 in vivo studies (26 articles in dairy cows and 11 articles in small ruminants) were aggregated after being strictly selected using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A mixed model methodology was used to examine our objectives. This method declares the subject 'study' as random effects and 'inclusion level' as fixed effects. Results indicated that RCS proportion was not associated with nutrient digestibility except for a quadratic effect (p < 0.05) on neutral detergent fibre digestibility. Higher RCS inclusion linearly increased (p < 0.05) nitrogen (N) intake but had no effect on dairy cows' production. Increasing RCS proportion altered milk fatty acid profile where the concentration of conjugated linolenic acid (CLA), C18:3 α-linolenic acid (ALA) and C18:0 linearly increased (p < 0.01). In small ruminants, SS proportion had no relationship with nutrient digestibility, N metabolism and growth performance (p > 0.05). However, a combination of dietary RCS + SS resulted in significantly higher (p < 0.05) CLA and ALA concentration in cow milk and average daily gain (ADG) in small ruminants compared to diets composed from either grass silage or alfalfa silage. Altogether, this meta-analysis highlights the synergistic effects of a combination of SS + RCS inclusion in improving milk fatty acids (FA) profile of dairy cows and ADG of small ruminants.

Progress of Conjugated Linoleic Acid on Milk Fat Metabolism in Ruminants and Humans

As a valuable nutrient in milk, fat accounts for a significant proportion of the energy requirements of ruminants and is largely responsible for determining milk quality. Fatty acids (FAs) are a pivotal component of milk fat. Conjugated linoleic acid (CLA) is one of the naturally occurring FAs prevalent in ruminant dairy products and meat. Increasing attention has been given to CLA because of its anti-cancer, anti-inflammatory, immune regulation, and lipid metabolism regulation properties, and these benefits potentially contribute to the growth and health of infants. In breast milk, CLA is present in trace amounts, mainly in the form of cis-9, trans-11 CLA. Notably, cis-9, trans-11 CLA improves the milk fat rate while trans-10, cis-12 CLA inhibits it. Apart from having multiple physiological functions, CLA is also a pivotal factor in determining the milk quality of ruminants, especially milk fat rate. In response to growing interest in green and healthy functional foods, more and more researchers are exploring the potential of CLA to improve the production performance of animals and the nutritional value of livestock products. Taken together, it is novel and worthwhile to investigate how CLA regulates milk fat synthesis. It is the purpose of this review to clarify the necessity for studying CLA in ruminant milk fat and breast milk fat.

The Dietary Inclusion of Ensiled Olive Cake Increases Unsaturated Lipids in Milk and Alters the Expression of Lipogenic Genes in Mammary and Adipose Tissue in Goats

This study aimed to evaluate the effect of the dietary inclusion of ensiled OC on milk yield, composition, fatty acid (FA) profile, and the expression of selected genes involved in lipid metabolism in the udder and adipose tissue of goats. Seventy-two Damascus dairy goats in mid-lactation were assigned randomly to three iso-nitrogenous and iso-energetic diets containing 0, 10, and 20% of ensiled OC as a replacement of forage (OC0, OC10, and OC20, respectively) for 42 days. During weeks 5 and 6 of the trial, dry matter intake, milk yield, milk composition, and FA profiles were recorded, while mammary and perirenal adipose tissue samples were also collected from six animals per treatment from the OC0 and OC20 groups for gene expression analysis. No significant differences were observed among groups concerning milk yield, 4% fat-corrected milk, fat, or protein yield (kg/d). In contrast, the milk fat percentage was gradually increased with increasing OC inclusion rates in the diets, while milk protein percentages were elevated in both OC groups but significantly only in the milk of the OC20 group. The content of FA between C4:0 to C16:0 was reduced, while mono-unsaturated FA (MUFA) concentration was enhanced in the goat milk of OC groups. The OC feeding treatment was associated with the increased mammary expression of SLC2A1 (p < 0.05), VLDLR (p < 0.01), FABP3 (p < 0.01), and elevated SLC2A1 (p < 0.05) and FASN (p < 0.01) gene expression in the adipose tissue of goats fed the OC20 diet. Overall, OC can be used in goats' diets as a forage replacement, at least in the inclusion rate of 20% DM, since this could increase the milk protein and fat percentage and enrich its content with beneficial for human health lipids without adversely affecting milk production traits.

Cactus cladodes for dairy goats: what is the best fiber source?

This study evaluated the effect of different fiber sources supplied with cactus cladodes in diets on the intake and digestibility of nutrients, ingestive behavior, milk yield, and composition of dairy goats. The fiber sources were corn silage, sorghum silage, Digitaria pentzii Stent. hay, and sugarcane bagasse. Twelve Saanen goats with an average weight of 48.9 ± 7.3 kg and average production of 2.8 ± 0.7 kg of milk/day were assigned in three simultaneous 4 × 4 Latin squares (four animals, four treatments, and four experimental periods). There was no difference between the fiber sources for intake (P > 0.05) of dry matter (2.58 kg/day), organic matter (2.30 kg/day), crude protein (0.385 kg/day), neutral detergent fiber (0.895 kg/day), non-fibrous carbohydrates (0.858 kg/day), and metabolizable energy (5.66 Mcal/day). Also, the fiber sources did not influence dry matter and nutrient digestibility (P > 0.05). The association of cactus cladodes with silages, hay, and sugarcane bagasse did not change milk production, milk production corrected for 3.5% of fat and corrected for energy (2.78; 2.53 and 2,55 kg/day, respectively), in addition to milk composition (P > 0.05). No differences were observed in ingestive behavior (P > 0.05). Any fiber sources evaluated are recommended.

Effects of forage and grain legume-based silages supplemented with faba bean meal or rapeseed expeller on lactational performance, nitrogen utilization, and plasma amino acids in dairy cows

The objective of this experiment was to investigate the effect of forage type [red clover (51%)-grass silage, i.e., RCG; vs. faba bean (66%)-grass silage, i.e., FBG] and concentrate type (faba bean, FB; vs. rapeseed expeller, RE) on lactational performance, milk composition and nitrogen (N) utilization in lactating dairy cows. Eight lactating multiparous Nordic Red cows were used in a replicated 4 × 4 Latin Square experiment, with 21-d periods, in a 2 × 2 factorial arrangement of treatments. The experimental treatments were as follows: (1) RCG with RE, (2) RCG with FB, (3) FBG with RE, and (4) FBG with FB. Inclusion rates of RE and FB were isonitrogenous. Crude protein contents of the experimental diets were 16.3, 15.9, 18.1, and 17.9% of dry matter, respectively. All diets included oats and barley and were fed ad libitum as total mixed rations with forage-to-concentrate ratio of 55:45. Dry matter intake and milk yield were recorded daily, and spot samples of urine, feces, and blood were collected at the end of each experimental period. Dry matter intake did not differ across diets, averaging 26.7 kg/d. Milk yield averaged 35.6 kg/d and was 1.1 kg/d greater for RCG versus FBG, and milk urea N concentration was lower for RCG compared with FBG. Milk yield was 2.2 kg/d and milk protein yield 66 g/d lower for FB versus RE. Nitrogen intake, urinary N, and urinary urea N excretions were lower, and milk N excretion tended to be lower for RCG compared with FBG. The proportion of the dietary N excreted as fecal N was larger in cows fed RCG than for those fed FBG, and the opposite was true for urinary N. We detected an interaction for milk N as percentage of N intake: it increased with RE compared with FB for RCG-based diet, but only a marginal increase was observed for FBG-based diet. Plasma concentration of His and Lys were lower for RCG than for FBG, whereas His tended to be greater and Lys lower for FB compared with RE. Further, plasma Met concentration was around 26% lower for FB than for RE. Of milk fatty acids, saturated fatty acids were decreased by RCG and increased by FB compared with FBG and RE, respectively, whereas monounsaturated fatty acids were increased by RCG versus FBG, and were lower for FB than for RE. In particular, 18:1n-9 concentration was lower for FB compared with RE. Polyunsaturated fatty acids, such as 18:2n-6 and 18:3n-3, were greater for RCG than for FBG, and 18:2n-6 was greater and 18:3n-3 was lower for FB versus RE. In addition, cis-9,trans-11 conjugated linoleic acid was lower for FB compared with RE. Faba bean whole-crop silage and faba bean meal have potential to be used as a part of dairy cow rations, but further research is needed to improve their N efficiency. Red clover-grass silage from a mixed sward, without inorganic N fertilizer input, combined with RE, resulted in the greatest N efficiency in the conditions of this experiment.

Lactation performance, milk fat output, and nutrient digestibility responses to the addition of liquid molasses or yeast culture in dairy cows fed super-conditioned corn

Increased diet fermentability may decrease ruminal pH and fiber digestibility, and increase the flow of trans fatty acids (FA) to the lower tract ultimately leading to milk fat depression. We recently showed that feeding super-conditioned corn, a new method of corn processing (95°C for 6 min in super-conditioner) for ruminants has potential to the reduction in milk fat yield caused by changes in ruminal pH and increased trans FA in milk fat. Supplementing yeast culture (YC) and replacing starch with sugar sources in diet can counteract the negative effects of high fermentable diets by improving ruminal pH and milk fat output. This study aimed to evaluate the effect of feeding beet liquid molasses (LM) and YC on intake and total-tract digestibility of nutrients, milk yield and composition, ruminal fermentation, milk FA profile, and plasma concentrations of glucose, nonesterified FA, β-hydroxybutyric acid, and urea N in early-lactation dairy cows fed high-starch diets containing super-conditioned corn. Twelve primiparous and 18 multiparous Holstein cows (mean ± SD; 67 ± 12 d in milk and 42 ± 2.1 kg of milk at the beginning of the experiment) were blocked by parity, pre-experimental milk yield, and DIM. Cows were used in a randomized complete block design experiment with 14 d as covariate period and 37 d for the experimental period. The following dietary treatments were fed as total mixed rations: (1) control diet (CTRL = no YC or LM supplementation), (2) LM supplementation at 5% of the diet dry matter (MOL diet), and (3) CTRL supplemented with 10 g/d of YC (YST diet). Diets were formulated to be isonitrogenous and isoenergetic. Intake of nutrients and apparent total-tract digestibility of crude protein and starch did not change across treatments. In contrast, cows fed the YST diet had the greatest apparent total-tract digestibility of dry matter, organic matter and neutral detergent fiber. Compared with the CTRL diet, yield of 4% FCM increased by 2.4 and 1.8 kg in cows fed MOL or YST, respectively. The ruminal molar proportions of acetate and butyrate increased in cows fed the YST or MOL diets, respectively, but the proportion of ruminal propionate was not affected by treatments. Milk fat concentration increased by supplementing both LM and YC and the milk yield of total trans-18:1 dropped by 45% and 18% relative to CTRL with MOL or YST diets, respectively. While the MOL diet increased the milk proportion and yield of de novo FA, no treatment effects were observed for the proportion and yield of preformed FA in the milk fat. Apart from β-hydroxybutyric acid concentration in plasma, which was greatest in cows fed MOL, remaining blood metabolites were not affected by treatments. Overall, MOL and YST diets increased 4% FCM and milk fat concentration and reduced the proportion of total trans-18:1 FA in milk fat in cows fed a concentrate based on super-conditioned corn. These responses were associated with increased ruminal pH and the molar proportions of acetate and butyrate with feeding the MOL and YST diets.

Quality and sensory milk traits of goats grazing Caatinga or confined receiving either corn or spineless cactus-based diets in the Brazilian semiarid environment

This study aimed to evaluate the yield, physical-chemical properties, fatty acid (FA) profile, and sensory traits of goat milk under different nutritional strategies in a Brazilian semiarid environment. Eighteen lactating crossbred dairy goats were distributed in a completely randomized design with three nutritional strategies: Caatinga strategy (1.5% of body weight with a concentrate supplementation), Corn-based confined strategy, and Spineless Cactus confined strategy. Daily milk yield was recorded, and milk samples were collected from all animals. Goats fed the spineless cactus-based diet presented a higher milk yield than goats feed the other strategies. Moreover, milk from goats fed with a spineless Cactus confined strategy presented higher saturated FA (SFA), and a lower proportion of cis- monounsaturated FA, trans-monounsaturated FA, and c9,t11-18:2 than milk from goats feed the other strategies. Milk from goats in the pasture system presented the highest proportions of 18:2n-6, 18:3n-3, and thus of polyunsaturated FA, when compared with milk from confined goats. We assume that milk from goats grazing in Caatinga pastures presents more benefits to human health due to the positive effects of this diet on the milk's fat content and FA profile, and this feeding strategy also results in a better sensory evaluation that may increase the acceptability of goat milk by consumers. All nutritional strategies evaluated herein and adopted in the semiarid region of Brazil are recommended for maintaining the yield, physical-chemical properties, and acceptability of milk goats.

Effect of a High-Starch or a High-Fat Diet on the Milk Performance, Apparent Nutrient Digestibility, Hindgut Fermentation Parameters and Microbiota of Lactating Cows

In this study, changes in milk performance, nutrient digestibility, hindgut fermentation parameters and microflora were observed by inducing milk fat depression (MFD) in dairy cows fed with a high-starch or a high-fat diet. Eight Holstein cows were paired in a completely randomized cross-over design within two 35 d periods (18 d control period and 17d induction period). During the control period, all cows were fed the low-starch and low-fat diet (CON), and at the induction period, four of the cows were fed a high-starch diet with crushed wheat (IS), and the other cows were fed a high-fat diet with sunflower fat (IO). The results showed that, compared to when the cows were fed the CON diet, when cows were fed the IS or IO diet, they had lower milk fat concentrations, energy corrected milk, 3.5% fat-corrected milk yield, feed efficiency and apparent digestibility of NDF and ADF. However, cows fed the IO diet had a lower apparent digestibility of ether extracts. In addition, we observed that when cows were fed the high-starch (IS) or high-fat (IO) diet, they had a higher fecal concentration of propionate and acetate, and a lower NH3-N. Compared to when the cows were fed the CON diet, cows fed the IS diet had a lower pH, and cows fed the IO diet had a lower concentration of valerate in feces. In the hindgut microbiota, the relative abundance of Oscillospiraceae_UCG-005 was increased, while the Verrucomicrobiota and Lachnospiraceae_AC2044_group were decreased when cows were fed the IO diet. The relative abundance of Prevotellaceae_UCG-003 was increased, while the Alistipes and Verrucomicrobiota decreased, and the Treponema, Spirochaetota and Lachnospiraceae_AC2044_group showed a decreasing trend when cows were fed the IS diet. In summary, this study suggested that high-starch or high-fat feeding could induce MFD in dairy cows, and the high-fat diet had the greatest effect on milk fat; the high-starch or high-fat diet affected hindgut fermentation and apparent fiber digestibility. The changes in hindgut flora suggested that hindgut microbiota may be associated with MFD in cows.

Changes in Chemical Composition and Fatty Acid Profile of Milk and Cheese and Sensory Profile of Milk via Supplementation of Goats' Diet with Marine Algae

The aim of the present study was to assess the effects of the low level of Schizochytrium limacinum marine algae (daily 5 g per animal) on the milk, cheese, and whey composition; fatty acid profile of milk and cheese; and the sensory profile of goat milk using an e-nose device. Thirty Alpine goats were randomly divided into two groups: the control group (C, n = 15)-fed grass with daily 600 g concentrate and the experimental group (MA, n = 15) who received the same forage and concentrate supplemented with 5 g/head/day marine algae. Animals were kept indoors and the investigation period lasted 52 days, including the first six weeks as the period of adaptation and the last 10 days as the treatment period. During the adaptation period, bulk milk samples from each group were collected once a week (0, 7, 14, 21, 28, 35, and 42 d), while during the treatment period (10 days), bulk milk samples from each group were taken every day, and cheese samples were processed from bulk milk each day from both groups. Marine algae supplementation had no negative effect on milk composition. In contrast, the marine algae inclusion significantly elevated the fat and protein content of whey and the protein content of cheese, as well as the recovery of fat and protein in the curd, while increasing the cheeses' moisture content on a fat-free basis. The marine algae supplementation significantly increased the docosahexaenoic acid (DHA) and the rumenic acid (CLA c9t11) concentrations and decreased the n-6/n-3 ratio in the milk and cheese. There were no significant differences between the C and the MA group with regard to the sensory profiles of the milk. It can be concluded that the milk obtained from goats given daily supplementation of 5g of MA has a fatty acid profile more beneficial to human health, without any negative effects on the milk's aromatic components.

The Influence of Cold-Pressed Linseed Cake Supplementation on Fatty-Acid Profile and Fat-Soluble Vitamins of Cows' Milk in an Organic Production System

The aim of the study was to determine the effect of linseed cake supplementation during the winter period as a factor influencing the level of some bioactive components (milk composition, fatty-acid profile, and fat-soluble vitamins) in the milk fat fraction in cows kept on an organic farm. Forty multiparous (second and third lactation) Holstein-Friesian cows were selected that had 81 ± 12 days in milk and produced 15.08 ± 1.20 kg of milk/day. Two groups were created for the experiment: control (CTL; n = 20) and experimental (LC; n = 20). The experiment was divided into two periods: an initial period lasting 7 days in which the experimental group was habituated to the new supplement in their diet; the proper experimental phase, lasting 6 weeks, in which the cows in the experimental group received an individual daily dose of linseed cake (300 g/day/cow). Linseed cake supplementation had a positive impact on the levels of bioactive components (fatty-acid profile and fat-soluble vitamins) in the milk fat fraction. At the end of the trial, the concentration of C18:2 cis9 trans11, C18:1 trans11, α-retinol, α-tocopherol, and total antioxidant status increased 1.59-, 1.94-, 3.12-, 3.38-, and 3.09-fold, respectively, relative to the control levels. The use of linseed cake in winter on organic farms makes it possible to increase the antioxidant potential of milk, thereby eliminating the disparity in the quality of milk from the summer season compared to the winter season.

Milk and plasma proteomes from cows facing diet-induced milk fat depression are related to immunity, lipid metabolism and inflammation

Milk proteins are a source of bioactive molecules for calves and humans that may also reflect the physiology and metabolism of dairy cows. Dietary lipid supplements are classically used to modulate the lipid content and composition of bovine milk, with potential impacts on the nutrient's homeostasis and the systemic inflammation of cows that remains to be more explored. This study aimed at identifying discriminant proteins and their associated pathways in twelve Holstein cows (87 ± 7 days in milk), multiparous and non-pregnant, fed for 28 d a diet either, supplemented with 5% DM intake of corn oil and with 50% additional starch from wheat in the concentrate (COS, n = 6) chosen to induce a milk fat depression, or with 3% DM intake of hydrogenated palm oil (HPO, n = 6) known to increase milk fat content. Intake, milk yield and milk composition were measured. On d 27 of the experimental periods, milk and blood samples were collected and label-free quantitative proteomics was performed on proteins extracted from plasma, milk fat globule membrane (MFGM) and skimmed milk (SM). The proteomes from COS and HPO samples were composed of 98, 158 and 70 unique proteins, respectively, in plasma, MFGM and SM. Of these, the combination of a univariate and a multivariate partial least square discriminant analyses reveals that 15 proteins in plasma, 24 in MFGM and 14 in SM signed the differences between COS and HPO diets. The 15 plasma proteins were related to the immune system, acute-phase response, regulation of lipid transport and insulin sensitivity. The 24 MFGM proteins were related to the lipid biosynthetic process and secretion. The 14 SM proteins were linked mainly to immune response, inflammation and lipid transport. This study proposes discriminant milk and plasma proteomes, depending on diet-induced divergence in milk fat secretion, that are related to nutrient homeostasis, inflammation, immunity and lipid metabolism. The present results also suggest a higher state of inflammation with the COS diet.

Replacement of corn silage with shredded beet pulp and dietary starch concentration: Effects on performance, milk fat output, and body reserves of mid-lactation dairy cows

We aimed to evaluate the interaction between dietary starch concentration, varied by replacing wheat bran with dry ground corn, and replacement of corn silage (CS) with shredded beet pulp (BP) on production, milk fat output, milk fatty acid profile, and body reserves in dairy cows. Sixty-four Holstein dairy cows (140 ± 26 d in milk) were randomly assigned to 8 pens (8 animals per pen). Treatments were arranged in a 2 × 2 factorial arrangement with 2 concentrations of starch and 2 sources of fiber and were allotted to 8 pens (2 pens per treatment). Treatments were (1) 15% dry ground corn and 24% CS, (2) 15% dry ground corn and 24% BP replacing CS, (3) 30% dry ground corn and 24% CS, and (4) 30% dry ground corn and 24% BP replacing CS. The trial lasted for 47 d and final 7 d of experimental period was used for data and sample collection. Cows fed the BP-based diets had greater dry matter intake than those offered the CS-based diets, whereas no effects were observed with starch concentration. Milk yield increased by 1.8 kg/d with BP-based diets compared with CS-based diets and by 2.5 kg/d when cows received the high-starch compared with low-starch diets. Interactions between dietary starch concentration and forage substitution were detected for milk fat concentration and yield as BP inclusion lowered milk fat output with high-starch diet. Milk trans-18:1 concentration was lower with 15% dry ground corn and 24% CS compared with other diets. In conclusion, the effects of dietary starch concentration (22 and 32% dry matter) and forage substitution on production responses were independent except for milk fat output and milk trans 18:1 isomers. Substituting CS with BP is effective at increasing milk yield regardless of starch concentration; however, milk fat yield is lower when BP is used with high-starch concentration.

Effects on rumen microbiome and milk quality of dairy cows fed a grass silage-based diet supplemented with the macroalga Asparagopsis taxiformis

The objective was to determine the effects on rumen microbiome and milk quality of reducing the methane (CH4) produced from enteric fermentation by the addition of Asparagopsis taxiformis (AT) to the diets of dairy cows. Six Nordic Red cows at 122 ± 13.7 (mean ± SD) days in milk, of parity 2.7 ± 0.52 and producing 36 kg ± 2.5 kg milk per day at the start of the trial were divided into three blocks by milk yield and assigned to an extra-period Latin-square change-over design comprising two dietary treatments. An extra period of observation was added to the Latin-square change-over design to control for carry-over effects. The dietary treatments were a diet consisting of grass silage and a commercial concentrate mixture (60:40) either not supplemented or supplemented with 0.5% AT on an organic matter intake basis. On average, daily CH4 production, CH4 yield, and CH4 intensity decreased by 60%, 54%, and 58%, respectively, in cows fed the diet supplemented with AT. Furthermore, hydrogen gas emitted by cows fed diets supplemented with AT increased by more than five times compared with cows fed a non-AT-supplemented diet. Feed intake was decreased and milk production altered, reflecting a decreased yield of milk fat in cows fed an AT-supplemented diet, but feed efficiency increased. Rumen fermentation parameters were changed to promote propionate rather than acetate and butyrate fermentation. The most prominent change in milk quality was an increase in bromine and iodine when the diet was supplemented with AT. The reduction in CH4 was associated with a shift from Methanobrevibacter to Methanomethylophilaceae in the archaeal population and a lower relative abundance of Prevotella in the bacterial population. Changes in milk fat odd-numbered and branched-chain fatty acids in the current study of AT supplementation support observed differences in ruminal archaeal and bacterial populations.

Effects of PUFA-Rich Dietary Strategies on Ruminants' Mammary Gland Gene Network: A Nutrigenomics Review

Although the inclusion of polyunsaturated fatty acids (PUFAs) in ruminants' diets appears to be a well-documented strategy to enrich milk with PUFAs, several gene networks that regulate milk synthesis and mammary gland homeostasis could be impaired. The objective of this literature review is to assess the effects of nutritional strategies focused on enriching milk with PUFAs on gene networks regulating mammary gland function and lipogenesis, as well as the impact of feed additives and bioactive compounds with prominent antioxidant potential on immune-oxidative transcriptional profiling, as a part of mammary gland homeostasis and health. The findings support the conclusion that PUFAs' inclusion in ruminants' diets more strongly downregulate the stearoyl-CoA desaturase (SCD) gene compared to other key genes involved in de novo fatty acid synthesis in the mammary gland. Additionally, it was revealed that seed oils rich in linoleic and linolenic acids have no such strong impact on networks that regulate lipogenic homeostasis compared to marine oils rich in eicosapentaenoic and docosahexaenoic acids. Furthermore, ample evidence supports that cows and sheep are more prone to the suppression of lipogenesis pathways compared to goats under the impact of dietary marine PUFAs. On the other hand, the inclusion of feed additives and bioactive compounds with prominent antioxidant potential in ruminants' diets can strengthen mammary gland immune-oxidative status. Considering that PUFA's high propensity to oxidation can induce a cascade of pro-oxidant incidences, the simultaneous supplementation of antioxidant compounds and especially polyphenols may alleviate any side effects caused by PUFA overload in the mammary gland. In conclusion, future studies should deeply investigate the effects of PUFAs on mammary gland gene networks in an effort to holistically understand their impact on both milk fat depression syndrome and homeostatic disturbance.

Milk fat depression and plasma lipids in dairy cows and goats

This study examines the effects of diets supplemented with various lipids selected to induce divergent milk fat content responses (including a milk fat depression) between dairy cows and goats on plasma lipid composition. The objective was to better understand the mechanisms behind the regulation of milk fat secretion in these two ruminant species. Twelve Holstein cows and 12 Alpine goats were fed a basal diet not supplemented (CTL) or supplemented with corn oil plus wheat starch (COS, 5% DM intake (DMI)), marine algae powder of Schizochytrium sp. (MAP, 1.5% DMI), or hydrogenated palm oil (HPO, 3% DMI), in a replicated 4 × 4 Latin square design, during 28 days. On day 27, blood samples were collected for lipid analysis. Plasma lipid classes were quantified by high-performance thin-layer chromatography, with triacylglycerol (TAG) and free fatty acid (FFA) fractions analysed for FA composition by GLC. Plasma molecular species of TAG and ceramides were determined by HPLC-high-resolution MS and by liquid chromatography-triple quadrupole, respectively. Irrespective of diet, plasma total lipid content was higher in cows than goats (+61%), and TAG concentration was higher in goats than cows (+157%). In cows, conversely to goats, COS increased the trans-10 C18:1 proportion in the free FA (+248%) and the TAG (+195%) fractions. In cows and goats, MAP induced increases in cholesterol esters, cholesterol and phospholipids compared to CTL and changes in the plasma free FA and FA of TAG profiles. In both ruminant species, the concentrations of the lipid fractions were unchanged by HPO compared to CTL. Our results point to species specificities and different diet effects in plasma concentrations and compositions of lipid fractions in cows and goats. These new data highlight how diets, that induce large variations in milk fat secretions, affect the plasma lipid classes available for milk fat synthesis.

The Effect of Dietary Inclusion of Microalgae Schizochytrium spp. on Ewes’ Milk Quality and Oxidative Status

An unprecedented challenge for nutritionists arises during the 21st century in order to produce highly nutritious and functional food which promotes human health. Polyunsaturated fatty acids (PUFA) that are highly contained in microalgae have broadly been confirmed for preventing cardiovascular diseases and regulating immune-oxidative status. However, their optimum dietary inclusion level needs to be defined since PUFA are prone to oxidation. For this purpose, 24 cross-bred dairy ewes, were separated into four groups (n = 6) and were fed with different levels of microalgae Schizochytrium spp. [0 (CON, no microalgae), 20 (SC20), 30 (SC30) and 40 (SC40) g/ewe/day] for 60 days. The results showed that although the production parameters were not impaired, milk fat content was decreased in medium and high-level supplemented groups while protein content was suppressed only for the medium one. Concerning the fatty acids (FA) profile, the proportions of C_14:0, trans C_18:1, trans-11 C_18:1, cis-9, trans-11 C_18:2, trans-10, cis-12 C_18:2, C_20:5 (EPA), C_22:5n-6 (DPA), C_22:6n-3 (DHA), the total ω3 FA and PUFA were significantly increased, while those of C_18:0, cis-9 C_18:1 and C_18:2n-6c were decreased in the milk of treated ewes. Additionally, in the S40 group an oxidative response was induced, observed by the increased malondialdehyde (MDA) levels in milk and blood plasma. In conclusion, the dietary inclusion of 20 g Schizochytrium spp./ewe/day, improves milks’ fatty acid profile and seems to be a promising way for producing ω3 fatty acid-enriched dairy products.

Changes of acute-phase proteins, glucose, and lipid metabolism during pregnancy in lactating dairy cows

The study aimed to evaluate the effects of different stages of lactation (0 to >  300 d) and pregnancy (0 to >  180 d) on serum amyloid A (SAA), C-reactive protein (CRP), glucose, total cholesterol (TCho), and triglyceride (TG) concentrations in dairy cows of different breeds. Thus, 40 healthy multiparous cows (10 Holstein, 10 Simmental, 10 Brown, and 10 Modicana) were randomly selected, and blood samples were collected once every 60 d for 1 year. Overall, SAA and CRP serum concentrations progressively increased and became more variable along the lactation, peaking at >  240-300 d, and then decreased in the last period ( >  300 d). Along pregnancy, SAA and CRP initially increased, with the highest concentrations at >  60-120 d, and then decreased until the last phase of pregnancy ( >  180 d). However, lactation and gestation phases did not significantly affect SAA and CRP when all the cows were analyzed together. A significant and positive correlation was observed between SAA and CRP both along lactation ( r = 0.89 ; p < 0.0001 ) and pregnancy ( r = 0.91 ; p < 0.0001 ). Breeds only showed differences in CRP levels along gestation ( p = 0.0102 ), due to a peak registered at 0-60 d in Holstein cows. In pregnant cows, glucose was positively correlated with SAA ( r = 0.43 ; p = 0.0017 ) and CRP ( r = 0.42 ; p = 0.0019 ). Hence, these significant and positive relationships reflect the physiological adaptations of the dairy cows along both gestational and lactational dynamics, suggesting that these proteins may also be involved in non-pathological processes. In this perspective, this study established that the obtained response markedly varies among healthy individuals along lactation and gestation and thus that the physiological range of acute-phase proteins (APPs) is wide; this makes it difficult to use these proteins as a marker of different physiological reproductive and productive periods.

Influence of almond hulls in lamb diets on animal performance and meat quality

Almond hulls (AH) were fed to lambs to study effects on performance and meat quality. Thirty Sarda lambs were allotted to three experimental groups and fed for 40 days either a cereal-based concentrate diet (control) or diets in which cereals were replaced with 15% (AH15) or 30% (AH30) almond hulls on a DM basis. Diets did not affect final body weight, dry matter intake, average daily gain, feed conversion ratio or carcass weight. Replacing part of the cereal mix (i.e., barley and maize) with AH did not affect meat fatty acid profiles. After 5 and 7 days of refrigerated storage respectively for cooked and raw meat, AH15 and AH30 treatments reduced meat lipid oxidation (P < 0.001). Our results suggest feeding almond hulls up to 30% in fattening lamb diets can improve meat oxidative stability without compromising growth performance.

Identification of Key Genes Associated With Early Calf-Hood Nutrition in Subcutaneous and Visceral Adipose Tissues by Co-Expression Analysis

Background

Substantive evidence has confirmed that nutrition state is associated with health risk and the onset of pubertal and metabolic profile. Due to heterogeneity, adipose tissues in different anatomical positions tend to show various metabolic mechanisms for nutrition. To date, the complicated molecular mechanisms of early calf-hood nutrition on bovine adipose tissue are still largely unknown. This study aimed to identify key genes and functionally enriched pathways associated with early calf-hood nutrition in visceral and subcutaneous adipose tissue.

Results

The RNA-seq data of visceral and subcutaneous adipose tissues of calves feeding on low and high dietary nutrition for more than 100 days were downloaded and analyzed by weighted gene co-expression network analysis (WGCNA). Two modules that positively associated with a low plane of nutrition diet and two modules with a high plane of nutrition diet were identified in the subcutaneous adipose tissue. The blue and yellow modules, most closely associated with low and high nutrition, were selected for the functional enrichment analysis and exploration of hub genes. The results showed that genes in the blue module were significantly enriched in pathways that related to fat metabolism, reproduction, and cell communication. Genes in the yellow module were enriched in pathways related to fat metabolism, reproduction, cell proliferation, and senescence. Meanwhile, the blue and brown modules in visceral adipose tissue were most closely associated with low and high nutrition, respectively. Notably, genes of the blue module were significantly enriched in pathways related to substance metabolism, and genes in the brown module were significantly enriched in energy metabolism and disease pathways. Finally, key genes in subcutaneous adipose tissue for low nutrition (PLCG1, GNA11, and ANXA5) and high nutrition (BUB1B, ASPM, RRM2, PBK, NCAPG, and MKI67), and visceral adipose tissue for low nutrition (RPS5, RPL4, RPL14, and RPLP0) and high nutrition (SDHA and AKT1) were obtained and verified.

Conclusion

The study applied WGCNA to identify hub genes and functionally enriched pathways in subcutaneous and visceral adipose tissue and provided a basis for studying the effect of early calf-hood nutrition on the two adipose tissue types.

Associations between Milk Fatty Acid Profile and Body Condition Score, Ultrasound Hepatic Measurements and Blood Metabolites in Holstein Cows

Dairy cows have high incidences of metabolic disturbances, which often lead to disease, having a subsequent significant impact on productivity and reproductive performance. As the milk fatty acid (FA) profile represents a fingerprint of the cow’s nutritional and metabolic status, it could be a suitable indicator of metabolic status at the cow level. In this study, we obtained milk FA profile and a set of metabolic indicators (body condition score, ultrasound liver measurements, and 29 hematochemical parameters) from 297 Holstein–Friesian cows. First, we applied a multivariate factor analysis to detect latent structure among the milk FAs. We then explored the associations between these new synthetic variables and the morphometric, ultrasonographic and hematic indicators of immune and metabolic status. Significant associations were exhibited by the odd-chain FAs, which were inversely associated with β-hydroxybutyrate and ceruloplasmin, and positively associated with glucose, albumin, and γ-glutamyl transferase. Short-chain FAs were inversely related to predicted triacylglycerol liver content. Rumen biohydrogenation intermediates were associated with glucose, cholesterol, and albumin. These results offer new insights into the potential use of milk FAs as indicators of variations in energy and nutritional metabolism in early lactating dairy cows.

Exploring the relationship between bacterial genera and lipid metabolism in bovine rumen

The rumen is characterised by a complex microbial ecosystem, which is particularly active in lipid metabolism. Several studies demonstrated a role of diet and breed on bacterial community profile, with the effect on metabolic pathways. Despite the knowledge achieved on metabolism and the bacterial profile, little is known about the relationship between individual bacteria and metabolic pathways. Therefore, a multivariate approach was used to search for possible relationships between bacteria and products of several pathways. The correlation between rumen bacterial community composition and rumen lipid metabolism was assessed in 40 beef steers (20 Maremmana and 20 Aubrac) reared with the same system and fed the same diet. A canonical discriminant analysis combined with a canonical correlation analysis (CCA) was performed to explore this correlation. The variables showing a Pearson correlation higher than 0.6 as absolute value and significant were retained for CCA considering the relationship of bacterial composition with several metabolic pathways. The results indicated that some bacterial genera could have significant impacts on the presence of several fatty acids. However, the relationship between genera and fatty acid changes according to the breed, demonstrating that the metabolic pathways change according to the host genetic background, related to breed evolution, although there is also an intra-breed genetic background which should not be ignored. In Maremmana, Succiniclasticum and Rikenellaceae_RC9_gut_group showed a high positive correlation with dimethylacetals (DMAs) DMA_C13:0, DMA_C14:0, DMA_C14:0iso, DMA_C15:0, DMA_C15:0iso, and DMA_C18:0. Prevotellaceae_UCG-003 correlates with C18:3c9c12c15 and C18:1t11, while Fibrobacter and Succiniclasticum correlate with C18:2c9t11 and Lachnospiraceae_NK3A20_group correlates with C18:1c12. Prevotellaceae_UCG-003, Ruminococcaceae_UCG-010, and Oribacterium showed a positive correlation with C13:0iso, and C17:0. Conversely, in Aubrac, Treponema_2 and Rikenellaceae_RC9_gut_group correlated with DMA_C14:0iso, DMA_C16:0iso, DMA_C17:0iso, while Ruminococcaceae_UCG-010, Christensenellaceae_R-7_group and Ruminococcaceae_NK4A214_group correlated with DMA_C18:1t11, DMA_C14:0, DMA_C18:1c12. Acetitomaculum correlated with C18:2c9c12, C18:1c12, C18:1c13, C18:1t12 and Lachnospiraceae_NK3A20_group with C18:1t6-8 and C18:1t9. Saccharofermentas, Ruminococcaceae_UCG-010 and Rikenellaceae_RC9_gut_group correlated with C18:2c9t11 while, Prevotellaceae_UCG-001 and Ruminococcus_1 correlated with C14:0iso, C15:0, C15:0iso, C17:0. Saccharofermentans, Rikenellaceae_RC9_gut_group, Ruminococcaceae_NK4A214_group, and Ruminococcaceae_UCG-010 correlated with C13:1c12 and C16:0iso. These results lead to hypothesise a possible association between several metabolic pathways and one or a few bacterial genera. If these associations are confirmed by further investigations that verify the causality of a bacterial genus with a particular metabolic process, it will be possible to deepen the knowledge on the activity of the rumen population in lipid metabolism. This approach appears to be a promising tool for uncovering the correlation between bacterial genera and products of rumen lipid metabolism.

Study of the Fatty Acid Profile of Milk in Different Sheep Breeds: Evaluation by Multivariate Factorial Analysis

Simple Summary

The quality of milk is strongly influenced by its lipid profile. The increase in fats with nutraceutical properties at the expense of those negative for human health, has always been a goal to improve the functional properties of milk. To achieve this goal, it is essential to know the metabolism of the mammary gland and the relationship between the various lipid components. Much is known about bovine milk, while the aspect relating to the sheep species has not been developed. The present work aims to investigate the relationships between the various fatty acids in sheep’s milk through a multivariate approach, which can highlight the mammary role of lipid synthesis.

Abstract

A multivariate analysis was used to investigate the fatty acid (FA) profile in three different Italian sheep breeds: Comisana, Massese, and Sarda. A sample of 852 animals was considered: 118 Massese, 303 Comisana, 431 Sarda. Sarda sheep were divided into two groups, based on their breeding origin (298 and 133 reared in Sardinia and Tuscany, respectively). Sarda sheep, bred both in Sardinia and in Tuscany, were considered in different groups, both because in these two regions most of the sheep of this breed are reared, and because they differ in geographical characteristics and in the farming system. The individual milk FA composition of dairy ewes was analyzed with multivariate factor analysis. The extracted factors were representative of the following eight groups of fatty acids or functions: factor 1 (odd branched fatty acids and long-chain fatty acids), factor 2 (sn3_position), factor 3 (alternative biohydrogenation), factor 4 (SCD_1), factor 5 (SCD_2), factor 6 (SCD_3), factor 7 (fat secretion) and factor 8 (omega-3). A factor analysis suggested the presence of different metabolic pathways for de novo short- and medium-chain fatty acids and Δ9-desaturase products. The ANOVA of factor scores highlighted the significant effects of the breed. The results of the present study showed that breed is an important factor in defining the fatty acid profile of milk, combined with the effect of the diet. Breeds reared in the same farming system (Comisana, Massese and Sarda reared in Tuscany) showed significant differences for all the factors extracted. At the same time, we found differences between the Sarda sheep reared in Sardinia and Tuscany, two different regions of Italy.

Intake and apparent digestibility of dry matter, milk production, and composition of cows fed with diets containing oilseed cakes: A meta-analysis

Oilseed cakes can partially replace corn or soy used in the diet without losing animal performance. The objective was to carry out a meta-analysis and principal component analysis to evaluate the effects of cakes on the intake and apparent digestibility coefficient (ADC) of dry matter (DM) and milk production and composition in lactating dairy cows. The data set used in the meta-analysis came from 51 studies published between 2009 and 2019, which resulted in 119 studies with 18 types of cakes evaluated in 1350 cows. Cows fed with cakes increased dry matter intake (DMI) by 0.366 kg d^-1 (P < 0.001) and DMI as a function of the animal's body weight by 0.103% (P < 0.0001) compared with the diet without cake. The milk protein content decreased by 0.050% (P < 0.010). The contents of neutral detergent fiber (NDF) (26%-%) and ether extract (EE) (3%-7%) of the cake diets did not affect ADCDM. Cakes with contents between 10% and 30% can replace corn or soy in the diet without affecting milk production, components (fat, protein, and lactose), and contents (fat and lactose), but it can reduce the milk protein content of milk.

Evaluating the effects of high-oil rapeseed cake or natural additives on methane emissions and performance of dairy cows

We evaluated the potential of feeding high-oil rapeseed cake or natural additives as rumen modifiers on enteric methane (CH₄) emissions, nutrient utilization, performance, and milk fatty acid (FA) profile of dairy cows. Eight Nordic Red dairy cows averaging (mean ± SD) 81 ± 21 d in milk and 41.0 ± 1.9 kg of milk yield at the beginning of the study were randomly assigned to a replicated 4 × 4 Latin square design with 21-d periods. Treatments comprised grass silage-based diets (45:55 forage to concentrate ratio on dry matter basis) including (1) control containing 19.3% rapeseed meal (CON), (2) CON with full replacement of rapeseed meal with rapeseed cake (RSC), (3) supplementation of CON with 50 g/d of yeast hydrolysate product plus coniferous resin acid-based compound (YHR), and (4) supplementation of CON with 20 g/d of combination of garlic-citrus extract and essential oils in a pellet (GCE). Apparent total-tract digestibility was measured using total collection of feces, and CH₄ emissions were measured in respiratory chambers on 4 consecutive days. Data collected during d 17 and 21 in each period were used for ANOVA analysis using a mixed model. Treatments did not affect dry matter intake (DMI), whereas feeding RSC increased crude protein and ether extract digestibility compared with the other diets. Emissions of CH₄ per day, per kilogram of DMI, and per kilogram of energy-corrected milk, and gross energy intake were lower for RSC compared with other diets. We found no effect of YHR on daily CH₄ emissions, whereas CH₄ yield (g of CH₄/kg of DMI or as percentage of gross energy intake) decreased with GCE compared with CON. Treatments did not influence energy balance. Further, RSC reduced the proportion of N intake excreted in feces, and YHR improved N balance compared with CON diet. Feeding RSC resulted in greatest yields of milk and energy-corrected milk, and feed efficiency. Relative to the CON diet, RSC decreased saturated FA by 10% in milk fat by increasing cis-monounsaturated FA but also increased the proportion of trans FA. Proportion of odd- and branched-chain FA increased with GCE and YHR compared with CON. We conclude that replacing rapeseed meal by rapeseed cake decreased CH₄ emissions, whereas YHR or GCE had no effect on CH₄ emissions in this study.

Fatty acid metabolism in lambs supplemented with different condensed and hydrolysable tannin extracts

Five groups of lambs (n = 9 each) were used to test the effect of plant extracts rich in hydrolysable (HT) or condensed tannin (CT) on animal performance, fatty acid composition of rumen content, liver and meat. The control group (CO) received a concentrate-based diet without tannins supplementation. The other groups received the same diet as the control lambs plus 4% chestnut (CH) and tara (TA) extracts as a source of HT and mimosa (MI) and gambier (GA) extracts as a source of CT. One-way ANOVA was used to assess the overall effect of dietary treatments, tannins supplementation (CO vs. CH+TA+MI+GA) and the effect of tannin type (HT vs. CT: CH+TA vs. MI+GA) on animal performance, rumen content, liver and intramuscular FA. Dietary CH negatively affected animal performance. The rumen content of the different groups showed similar levels of 18:3 c9c12c15, 18:2 c9c12, 18:2 c9t11, 18:1 t11 and 18:0, whereas 18:1 t10 was greater in CO. Also, 18:1 t10 tended to be lower in the rumen of HT than CT-fed lambs. These data were partially confirmed in liver and meat, where CO showed a greater percentage of individual trans 18:1 fatty acids in comparison with tannins-fed groups. Our findings challenge some accepted generalizations on the use of tannins in ruminant diets as they were ineffective to favour the accumulation of dietary PUFA or healthy fatty acids of biohydrogenation origin in the rumen content and lamb meat, but suggest a generalized influence on BH rather than on specific steps.

Transcriptome Adaptation of the Ovine Mammary Gland to Dietary Supplementation of Extruded Linseed

Several dietary strategies were adopted to reduce saturated fatty acids and increase beneficial fatty acids (FA) for human health. Few studies are available about the pathways/genes involved in these processes. Illumina RNA-sequencing was used to investigate changes in the ovine mammary gland transcriptome following supplemental feeding with 20% extruded linseed. Comisana ewes in mid-lactation were fed a control diet for 28 days (control period) followed by supplementation with 20% DM of linseed panel for 28 days (treatment period). Milk production was decreased by 30.46% with linseed supplementation. Moreover, a significant reduction in fat, protein and lactose secretion was also observed. Several unsaturated FAs were increased while short and medium chain saturated FAs were decreased by linseed treatment. Around four thousand (1795 up- and 2133 down-regulated) genes were significantly differentially regulated by linseed supplementation. The main pathways affected by linseed supplementation were those involved in the energy balance of the mammary gland. Principally, the mammary gland of fed linseed sheep showed a reduced abundance of transcripts related to the synthesis of lipids and carbohydrates and oxidative phosphorylation. Our study suggests that the observed decrease in milk saturated FA was correlated to down-regulation of genes in the lipid synthesis and lipid metabolism pathways.

Evaluating the Inclusion of Cold-Pressed Rapeseed Cake in the Concentrate for Dairy Cows upon Ruminal Biohydrogenation Process, Ruminal Microbial Community and Milk Production and Acceptability

The aim of this trial was to assess the effect of feeding a concentrate including cold-pressed rapeseed cake (CPRC) on productive performance, milk quality and its sensory properties, ruminal biohydrogenation, and bacterial communities. Eighteen cows were paired, and two experimental diets (control vs. CPRC) were distributed within the pair. Concentrates were iso-energetic and iso-proteic and contained similar amounts of fat. The average days in milk, milk yield, and body weight of the animals were (mean ± SD) 172 ± 112 d, 585 ± 26 kg, and 25.4 ± 6.2 kg/d, respectively. The experiment lasted for 10 wk. Feeding CPRC resulted in lower ruminal saturated (p < 0.001) and higher monounsaturated (p = 0.002) fatty acids. Feeding CPRC increased Ruminococcus, Prevotella, and Entodinium but decreased Blautia; p-75-a5; undefined genera within orders Clostridiaceae and RF39 and within families Christensenellaceae, Lachnospiracease, and Ruminococcaceae; and fungi from the phylum neocallimastigomycota. The milk fatty acid profile was characterized by a lower n6:n3 ratio (p = 0.028). Feeding CPRC did not affect the milk yield, milk quality, or fat corrected milk (p > 0.05). Feeding CPRC improved the overall milk acceptability (p = 0.047). In conclusion, CPRC affected some microbial taxa, modified the biohydrogenation process, and improved the milk fatty acid profile and consumer acceptance without detrimental effects on milk production and composition.

Simultaneous Determination of C18 Fatty Acids in Milk by GC-MS

The determination of C18 fatty acids (FAs) is a key and difficult aspect in FA profiling, and a qualified method with good chromatographic separation and high sensitivity, as well as easy methylation, is required. A GC-MS method was established to simultaneously determine C18 FAs in milk. To simplify the methylation protocol for milk samples, besides a base-catalyzation methylation (50 °C for 20 min), the necessity of an additional acid-catalyzation was also studied using different temperatures (60 °C, 70 °C, 80 °C, and 90 °C) and durations (90 min and 150 min). The results showed that the chromatographic resolution was improved, although three co-eluted peaks existed. The base-catalyzation was sufficient, and an additional acid-catalyzation was not necessary. The proposed method was validated with good sensitivity, linearity, accuracy, and precision, and then applied in determining C18 FAs in 20 raw milk and 30 commercial milk samples. UHT milk presented a different profile of C18 FAs from raw milk and PAS milk samples, which indicated that excessive heating could change the profile. Overall, the proposed method is a high-throughput and competent approach for the determination of C18 FAs in milk, and which presents an improvement in chromatographic resolution and sensitivity, as well as a simplification of methylation.

Effect of concentrate enriched with palmitic acid versus rapeseed oil on dairy performance, milk fatty acid composition, and mammary lipogenic gene expression in mid-lactation Holstein cows

This study was performed to characterize the effect of a concentrate supplemented with free palmitic acid (4% on a DM basis; PA) or rapeseed oil (4% on a DM basis; RO) compared with a no-added-lipid control concentrate (CT) on the performance of dairy cows fed a corn silage-based diet over a 9-wk period. After a 3-wk pre-experimental period, 54 Holstein cows were randomly allocated to 3 experimental treatments to receive forage ad libitum with a fixed amount of CT, RO, or PA (8 kg/d for 2-yr-old primiparous; 10 kg/d for older cows). During the experiment, dry matter intake, milk yield and composition, fatty acid (FA) yields and FA profile, and feed efficiency were determined. At wk 9 of the experimental period, the mRNA levels of 10 genes involved in lipid metabolism in mammary tissue biopsy samples were measured. Compared with CT, RO and PA increased forage intake. Compared with CT, RO increased concentrate intake, the value being intermediate for PA. Compared with CT, RO increased milk yield (+2.0 kg/d) and decreased milk fat and protein content (-3.8 and -1.2 g/kg, respectively), whereas PA increased milk fat content (+4.1 g/kg). Compared with CT and RO treatments, PA increased milk fat yield (+179 g/d) and 3.5% fat-corrected milk and energy-corrected milk output (+2.8 and +2.3 kg/d, respectively), and thus improved feed efficiency (+7.3%). Compared with CT treatment, RO increased milk contents of the sum of >C16 FA, monounsaturated FA, polyunsaturated FA, trans FA, and n-3 FA, whereas PA decreased these FA contents (except n-3 FA) and also decreased n-6 FA. The variations in milk fat yield and content and FA secretion at wk 9 were not associated with modifications in mammary expression of 10 genes involved in major lipid pathways, except for the transcription factor PPARG1, which tended to be higher in PA versus RO treatment. This study demonstrated that PA improved milk fat yield and feed efficiency compared with RO and suggests that factors other than gene expression, such as substrate availability for mammary metabolism or other levels of regulation (transcriptional, posttranscriptional, translational or posttranslational), could play a key role in milk fat and FA responses to changes in diet composition in cows.

Individual differences in responsiveness to diet-induced milk fat depression in dairy sheep and goats

Both sheep and goats can display very different individual degrees of milk fat depression (MFD), which might explain some apparent contradictions in the literature. Because the antilipogenic effect of certain fatty acids (FA) is the most likely origin of MFD, characterizing the milk FA profile of animals showing different degrees of MFD seems a helpful step to understand the physiological basis of the tolerance or susceptibility to the syndrome. Analyzing whether specific traits may predetermine a particular responsiveness would also be of relevance to meet this aim. However, information about these aspects is scant, not only in goats and sheep but in ruminants in general. This study was conducted with 25 Murciano-Granadina does and 23 Assaf ewes that were fed a total mixed ration without lipid supplementation for 3 wk (control period). Then, all animals received the same basal diet supplemented with 2% of fish oil (FO) for 5 additional weeks (MFD period). At the end of this second period, and on the basis of the extent of FO-induced decreases in milk fat concentration, the 5 most responsive (RESPON+) and the 5 least responsive (RESPON-) animals were selected within each species, 20 in total. Milk yield and composition, including a comprehensive FA profile, were examined at the end of each period. By design, between-group variation in milk fat concentration and yield was substantial, but no significant interaction with the effect of species was detected. Reductions in these 2 performance traits averaged 6% in RESPON- and 26% in RESPON+. Results do not allow suggesting that responsiveness to MFD would be clearly predetermined neither by the studied performance traits nor by milk FA profile, although a certain relationship with energy balance might exist. Furthermore, variations in ewes and does displaying different individual degrees of MFD may be associated with changes in certain candidate milk fat inhibitors, such as trans-10 18:1 and cis-9 16:1, whereas trans-10,cis-12 conjugated linoleic acid would only have a minor role in determining MFD severity. Alterations in the molar yield of de novo and preformed FA suggest relevant differences in the mechanisms underlying MFD in RESPON+ and RESPON-, with interspecies effects being observed only in more tolerant animals. Further research is still required to elucidate key determinants of responsiveness to MFD.

Sensory-Directed Identification of Creaminess-Enhancing Semi-Volatile Lactones in Crumb Chocolate

In order to gain a more comprehensive knowledge of the chemical nature of creaminess-related flavor compounds in milk chocolates on a molecular level, crumb chocolate was analyzed by means of activity guided screening techniques. Sensory studies of a triglyceride-free lipid emulsion indicated that the n-pentane extract showed the highest impact regarding creaminess sensation. Enhancement of creaminess by adding anhydrous milk fat fractions to chocolate was demonstrated by fractionated high-vacuum distillation of different fats associated with the chocolate production combined with sensory experiments. Syntheses of various δ-lactones and the quantification of these sensory active semi-volatiles led to the conclusion that the anhydrous milk fat contains a series of γ- and δ-lactones. Cocoa butter revealed a high concentration of δ-hexadecalactone, too. Experiments suggested that lactones are generated from the potential precursors monohydroxyalkanoic acid(s) esterified (mono-tri)glyceride(s) during heating. Sensory studies exhibited recognition thresholds of 29–40 µmol/kg for the long-chain δ-lactones in crumb chocolate. Furthermore, significant enhancement of the retro-nasal creamy flavor was found for δ-tetradecalactone.

Short-term forage substitution with ensiled olive cake increases beneficial milk fatty acids in lactating cows

This study aimed to evaluate the effect of short-term forage substitution with ensiled olive cake (OC), on yield, composition and fatty acid (FA) profile of cows' milk. Mid-lactating Holstein-Friesian cows were randomly assigned for 21 days to two isoenergetic and isoproteic feeding treatments (12 animals per treatment), containing 0 and 10% DM of ensiled OC (C and OC groups, respectively). Milk yield was recorded daily, and milk samples were collected at 14 and 21 days of the trial for analyzing the fat, protein, and FA profile of milk. No significant differences were observed in milk yield, protein, and fat nor in protein and fat percentage of milk between groups. However, dietary supplementation with ensiled OC modified the FA profile of cow milk. Feeding cows with ensiled OC resulted in a significant decline of medium-chain FA, while long-chain and mono-unsaturated FA were risen in milk (P < 0.05). Among individual saturated FA, palmitic was particularly reduced, while among individual mono-unsaturated FA, increments of C18:1 cis-9 were demonstrated with the OC treatment (P < 0.05). Although total poly-unsaturated FA were decreased, the concentration of CLA cis-9, trans-11 tended to be elevated with OC feeding (P = 0.06). Overall, short-term forage substitution with ensiled OC improved, beneficially for human health, the lipid profile of milk without adversely affecting milk yield or milk composition of lactating cows.

Effect of Marine Algae Supplementation on Somatic Cell Count, Prevalence of Udder Pathogens, and Fatty Acid Profile of Dairy Goats' Milk

The aim of this study was to evaluate the effect of the Schizochytrium limacinum marine algae on the milk composition and fatty acid profile, somatic cell count, and prevalence of pathogen bacteria in the raw milk of multiparous Alpine goats. Twenty-eight dairy goats were randomly allocated to two groups: control group (C)-fed with 1500 g alfalfa hay and 600 g concentrate; experimental group (MA)-received the same forages and concentrate supplemented with 10 g/head/day marine algae. The goats were housed indoors, while the experiment lasted five weeks, and the milk samples were taken every week. Marine algae feeding had no negative effect on milk composition. The marine algae inclusion significantly decreased the milk somatic cell count and the presence of udder pathogens in the MA group. Mean somatic cell count and presence of udder pathogens were 5.73 log cells/mL and 31%, respectively, in the C group, while these values were 5.34 log cells/mL and 10%, respectively, in the MA group. The marine algae supplementation significantly increased DHA and rumenic acid concentration in the milk of the MA group (0.32 and 0.99 g/100 g of fatty acids, respectively) compared to the C group (0.04 and 0.65 g/100 g of fatty acids, respectively). It can be concluded that a diet supplemented with marine algae significantly improves the udder health of goats and the concentrations of health-promoting fatty acids in milk.

Nutritional Regulation of Mammary Gland Development and Milk Synthesis in Animal Models and Dairy Species

In mammals, milk is essential for the growth, development, and health. Milk quantity and quality are dependent on mammary development, strongly influenced by nutrition. This review provides an overview of the data on nutritional regulations of mammary development and gene expression involved in milk component synthesis. Mammary development is described related to rodents, rabbits, and pigs, common models in mammary biology. Molecular mechanisms of the nutritional regulation of milk synthesis are reported in ruminants regarding the importance of ruminant milk in human health. The effects of dietary quantitative and qualitative alterations are described considering the dietary composition and in regard to the periods of nutritional susceptibly. During lactation, the effects of lipid supplementation and feed restriction or deprivation are discussed regarding gene expression involved in milk biosynthesis, in ruminants. Moreover, nutrigenomic studies underline the role of the mammary structure and the potential influence of microRNAs. Knowledge from three lactating and three dairy livestock species contribute to understanding the variety of phenotypes reported in this review and highlight (1) the importance of critical physiological stages, such as puberty gestation and early lactation and (2) the relative importance of the various nutrients besides the total energetic value and their interaction.

Rumen biohydrogenation and milk fatty acid profile in dairy ewes divergent for feed efficiency

A sustainable increase in livestock production would require selection for improved feed efficiency, but the mechanisms underlying this trait and explaining its large individual variation in dairy ruminants remain unclear. This study was conducted in lactating ewes to test the hypothesis that rumen biohydrogenation (BH) would differ between high- and low-efficiency animals, and these differences would be reflected in rumen fatty acid (FA) profile and affect milk FA composition. A second aim was to identify differences in FA that may serve as biomarkers of feed efficiency. Data of daily feed intake and milk yield and composition, as well as body weight, were collected individually over a 3-wk period in 40 ewes. The difference between the mean actual and predicted feed intake (estimated through metabolizable energy requirements for maintenance, production, and body weight change) over the period was used as the feed efficiency index (FEI) to select 8 of the highest feed efficiency (H-FE) and 8 of the lowest feed efficiency (L-FE) animals. In addition, residual feed intake (RFI) was estimated as the residual term from the regression of feed intake on various energy sinks. Rumen and milk FA composition were characterized by using gas chromatography, and results were analyzed using a statistical model that included the fixed effect of the group (H-FE vs. L-FE). The FEI averaged -0.29 ± 0.046 and 0.81 ± 0.084 in H-FE and L-FE, respectively, whereas RFI averaged -0.16 ± 0.084 and 0.18 ± 0.082, respectively. The correlation coefficient between both metrics was 0.69. Feed intake was similar in both groups, but H-FE showed greater milk yield, with increases in lactose content and yield, and in milk protein and fat production. Results from rumen FA profiles included a lower proportion of 18:2n-6, cis-9 18:1, and of several of their BH metabolites, and a greater concentration of 18:0, which may indicate that the apparent BH would be more complete in more efficient sheep. Milk FA analysis suggested that the greater fat yield in the H-FE group was mostly explained by increased de novo FA synthesis, whereas their milk would have lower proportions of cis-9 18:1 and C20 to 22n-6 polyunsaturated FA than L-FE. Stepwise multiple linear regression suggested that milk C20 to 22n-6 PUFA might be convenient biomarkers to discriminate more efficient dairy sheep. Further research is needed to validate these findings (e.g., under different dietary conditions).