Changes in fatty acid profile of Bovec sheep milk due to different pasture altitude

Sheep rearing on mountain pastures is an ancestral tradition in northwestern Slovenia. The indigenous Bovec sheep are widespread there and are well adapted to the rough Alpine rearing conditions. Every year, after weaning, the sheep start grazing in the lowlands (L) and then gradually move to mountain pastures, and finally, to the highland (H) pastures of the Alps. Grazing positively affects the fatty acid (FA) composition in sheep milk fat with increased availability of polyunsaturated FA (PUFA) in grass, and subsequently, in milk. Consequently, the objective of this work was to study the FA profile in sheep milk during grazing in four geographical areas in the Alps. A total of 15 ewes of the Bovec sheep breed were randomly selected and milk samples from these ewes were taken at four different pasture locations that differed with regard to altitude: the L pasture location at an altitude of 480 m, the mountain pastures (M1 and M2) at altitudes of 1100 to 1300 m and 1600 to 1900 m, respectively, and the H pastures at altitudes of 2100 to 2200 m. Milk samples from the ewes were taken during the grazing season from April to September. The chemical and FA composition of the milk samples from each pasture location were determined. There were significant differences in the concentrations of FA among the L, M1, M2 and H milk samples. We observed decreases of the concentrations of saturated FA (SFA) in milk from L to H pastures. The concentration of α-linolenic FA, monounsaturated FA (MUFA), PUFA and n-3 PUFA in milk were increased significantly with pasture altitude. The n-6/n-3 PUFA ratio was reduced by the change of pasture altitude with the lowest value at the M1 pasture (1.5). The concentrations of total SFA decreased significantly and was lowest at the L pasture. Our results underline the importance of the effect of grazing in the Alpine region associated with pasture altitude on the FA profile of sheep milk. The first variation in FA concentration in sheep milk occurred between L and M1, although it was more evident on H pastures in the Alpine mountains. Changes of the FA profile in sheep milk due to pasture altitude were related to variation in FA concentration in the pasture and the botanical composition of the pasture location.     

Maternal grazing on stubble and Mediterranean shrubland improves meat lipid profile in light lambs fed on concentrates

Concentrates-fed lamb meat is often associated with an unfavourable lipid profile (high levels of saturated and/or n-6 polyunsaturated fatty acids; SFA and PUFA). For this reason, Spanish sheep producers from Mediterranean areas are turning to traditional grazing by ewes to obtain healthier lamb meat. The objective of this research was to determine the effects of maternal grazing on the fatty acid (FA) composition of weaned lamb meat. The ewes (Segureña breed) were allocated to two different rearing systems during pregnancy (5 months) and lactation (45 days): (i) feeding indoors on barley grain and lucerne pellets; (ii) grazing on cereal stubble, fallow land and seasonal pastures consisting of Mediterranean shrubs, herbs and trees. Two groups of 20 autumn and spring lambs were sampled. The lambs were weaned at 13.1±0.9 kg and 45.0±4.1 days age and fed on grain-based concentrates until they reached 24.8±2.1 kg live weight (light lambs slaughtered at 98.3±3.6 days of age). The FA content was determined in the intramuscular loin fat by gas chromatography using a flame ionization detector. The ewe diet did not affect the levels of the main lamb FAs (C18:1c+t, C16:0 and C18:2c), and so did not provide any additional reduction in fat saturation. Saturated fatty acids represented around 40% of total FAs determined in the meat. Ewe grazing acted as an n-3 PUFA-promoting diet, providing a lamb meat with a lower n-6/n-3 ratio. Spring lamb meat had higher proportions of n-3 PUFA (C18:3n-3, C20:5, C22:5 and C22:6) and conjugated linoleic acid (C18:2c9t11+c11t9) to the detriment of the n-6 PUFAs (C20:4, C20:2 and C22:4), while autumn lamb meat also had higher levels of C18:3n-3 and C18:3n-6, and lower level of C20:4, which points to little seasonal differences. The n-6/n-3 ratio achieved by ewe grazing fell from 8.2 to 4.1 (Spring) and from 7.6 to 5.5 (Autumn), values which are close to those recommended in human diet for good cardiovascular health. These n-6/n-3 reductions were associated with lower levels of total PUFA and C20:4n-6. Our research concluded that grazing on stubble and Mediterranean shrubland by ewes, a sustainable rearing practice involving local agro resources, contributed to obtaining weaned lamb meat with a more favourable lipid profile and so can be recommended to sheep farmers.     

Milk and meat fatty acids from sheep fed a plantain–chicory mixture or a grass-based permanent sward

Plantain and chicory are interesting forage species since they present good nutritional quality and are more resistant to drought than many temperate grasses. The fatty acid (FA) profile in milk and meat is related to a growing concern for the consumption of healthy foods, that is, with a lower content of saturated FA, higher polyunsaturated FA (PUFA) and a favourable n-6 : n-3 FAs ratio. Our objective was to evaluate the FA content in ewe’s milk and lamb’s meat fed a plantain–chicory mixture (PCH) or a grass-based permanent sward (GBS) dominated by perennial ryegrass. Eighteen Austral ewes in mid-lactation were allocated to PCH and GBS treatments. Milk samples were obtained during September (spring). Thirty weaned lambs were finished on both treatments from November to December (7 weeks), slaughtered and their meat sampled. Fat from milk and meat samples was extracted and stored until analysed by gas chromatography. Milk fat from GBS was higher than from PCH (P < 0.05) in C18:0 (11 385 v. 5874 mg/100 g FA), 9c-18:1 (15 750 v. 8565 mg/100 g FA), 11 t-18:1 (4576 v. 2703 mg/100 g FA) and 9c,11 t-18:2 (1405 v. 921 mg/100 g FA) and lower in 18:2n-6 (827 v. 1529 mg/100 g FA) and 18:3n-3 (943 v. 1318 mg/100 g FA) FA. Total mono-unsaturated FA was higher in GBS than PCH (P < 0.05). Meat fat from PCH swards presented a higher (P < 0.05) content than GBS for 18:2n-6 (46.8 v. 28.2 mg/100 g FA), linolenic (24.6 v. 14.2 mg/100 g FA), polyunsaturated FA (119.7 v. 73.4 mg/100 g FA), n-6 (65.9 v. 40.8 mg/100 g FA) and n-3 (53.8 v. 32.5 mg/100 g FA), respectively. No effect of treatment (P > 0.05) was detected for 9c-18:1 (283.9 v. 205.8 mg/100 g FA), 11 t-18:1 (26.2 v. 19.3 mg/100 g FA) and 9c,11 t-18:2 (10.1 v. 7.6 mg/100 g FA), for PCH and GBS. These results suggest that grazing a PCH mixture results in a higher concentration of PUFA in ewes’ milk and in lambs’ fat, as compared to a GBS sward.     

Effects of starch-rich or lipid-supplemented diets that induce milk fat depression on rumen biohydrogenation of fatty acids and methanogenesis in lactating dairy cows

Optimizing milk production efficiency implies diets allowing low methane (CH₄) emissions and high dairy performance. We hypothesize that nature of energy (starch v. lipids) and lipid supplement types (monounsaturated fatty acid (MUFA) v. polyunsaturated fatty acid (PUFA) mitigate CH₄ emissions and can induce low milk fat content via different pathways. The main objective of this experiment was to study the effects of starch-rich or lipid-supplemented diets that induce milk fat depression (MFD) on rumen biohydrogenation (RBH) of unsaturated fatty acids (FA) and enteric CH₄ emissions in dairy cows. Four multiparous lactating Holstein cows (days in milk=61±11 days) were used in a 4×4 Latin square design with four periods of 28 days. Four dietary treatments, three of which are likely to induce MFD, were based (dry matter basis) on 56% maize silage, 4% hay and 40% concentrates rich in: (1) saturated fatty acid (SFA) from Ca salts of palm oil (PALM); (2) starch from maize grain and wheat (MFD-Starch); (3) MUFA (cis-9 C18:1) from extruded rapeseeds (MFD-RS); and (4) PUFA (C18:2n-6) from extruded sunflower seeds (MFD-SF). Intake and milk production were measured daily. Milk composition and FA profile, CH₄ emissions and total-tract digestibility were measured simultaneously when animals were in open-circuit respiration chambers. Fermentation parameters were analysed from rumen fluid samples taken before feeding. Dry matter intake, milk production, fat and protein contents, and CH₄ emissions were similar among the four diets. We observed a higher milk SFA concentration with PALM and MFD-Starch, and lower milk MUFA and trans-10 C18:1 concentrations in comparison to MFD-RS and MFD-SF diets, while trans-11 C18:1 remained unchanged among diets. Milk total trans FA concentration was greater for MFD-SF than for PALM and MFD-Starch, with the value for MFD-RS being intermediate. Milk C18:3n-3 content was higher for MFD-RS than MFD-SF. The MFD seems more severe with MFD-SF and MFD-RS than PALM and MFD-Starch diets, because of a decrease in milk SFA concentration and a stronger shift from trans-11 C18:1 to trans-10 C18:1 in milk. The MFD-SF diet increased milk trans FA (+60%), trans-10 C18:1 (+31%), trans-10,cis-12 CLA (+27%) and PUFA (+36%) concentrations more than MFD-RS, which explains the numerically lowest milk fat yield and indicates that RBH pathways of PUFA differ between these two diets. Maize silage-based diets rich in starch or different unsaturated FA induced MFD with changes in milk FA profiles, but did not modify CH₄ emissions.     

Transient reductions in milk fat synthesis and their association with the ruminal and metabolic profile in dairy cows fed high-starch,low-fat diets

Sub-acute ruminal acidosis (SARA) is sometimes observed along with reduced milk fat synthesis. Inconsistent responses may be explained by dietary fat levels. Twelve ruminally cannulated cows were used in a Latin square design investigating the timing of metabolic and milk fat changes during Induction and Recovery from SARA by altering starch levels in low-fat diets. Treatments were (1) SARA Induction, (2) Recovery and (3) Control. Sub-acute ruminal acidosis was induced by feeding a diet containing 29.4% starch, 24.0% NDF and 2.8% fatty acids (FAs), whereas the Recovery and Control diets contained 19.9% starch, 31.0% NDF and 2.6% FA. Relative to Control, DM intake (DMI) and milk yield were higher in SARA from days 14 to 21 and from days 10 to 21, respectively (P < 0.05). Milk fat content was reduced from days 3 to 14 in SARA (P < 0.05) compared with Control, while greater protein and lactose contents were observed from days 14 to 21 and 3 to 21, respectively (P < 0.05). Milk fat yield was reduced by SARA on day 3 (P < 0.05), whereas both protein and lactose yields were higher on days 14 and 21 (P < 0.05). The ruminal acetate-to-propionate ratio was lower, and the concentrations of propionate and lactate were higher in the SARA treatment compared with Control on day 21 (P < 0.05). Plasma insulin increased during SARA, whereas plasma non-esterified fatty acids and milk β-hydroxybutyrate decreased (P < 0.05). Similarly to fat yield, the yield of milk preformed FA (>16C) was lower on day 3 (P < 0.05) and tended to be lower on day 7 in SARA cows (P < 0.10), whereas yield of de novo FA (<16C) was higher on day 21 (P < 0.01) in the SARA group relative to Control. The t10- to t11-18:1 ratio increased during the SARA Induction period (P < 0.05), but the concentration of t10-18:1 remained below 0.5% of milk fat, and t10,c12 conjugated linoleic acid remained below detection levels. Odd-chain FA increased, whereas branched-chain FA was reduced during SARA Induction from days 3 to 21 (P < 0.05). Sub-acute ruminal acidosis reduced milk fat synthesis transiently. Such reduction was not associated with ruminal biohydrogenation intermediates but rather with a transient reduction in supply of preformed FA. Subsequent rescue of milk fat synthesis may be associated with higher availability of substrates due to increased DMI during SARA.     

Frequent moving of grazing dairy cows to new paddocks increases the variability of milk fatty acid composition

The aim of this work was to investigate the variations of milk fatty acid (FA) composition because of changing paddocks in two different rotational grazing systems. A total of nine Holstein and nine Montbéliarde cows were divided into two equivalent groups according to milk yield, fat and protein contents and calving date, and were allocated to the following two grazing systems: a long duration (LD; 17 days) of paddock utilisation on a heterogeneous pasture and a medium duration (MD) of paddock utilisation (7 to 10 days) on a more intensively managed pasture. The MD cows were supplemented with 4 kg of concentrate/cow per day. Grazing selection was characterised through direct observations and simulated bites, collected at the beginning and at the end of the utilisation of two subsequent MD paddocks, and at the same dates for the LD system. Individual milks were sampled the first 3 days and the last 2 days of grazing on each MD paddock, and simultaneously also for the LD system. Changes in milk FA composition at the beginning of each paddock utilisation were highly affected by the herbage characteristics. Abrupt changes in MD milk FA composition were observed 1 day after the cows were moved to a new paddock. The MD cows grazed by layers from the bottom layers of the previous paddock to the top layers of the subsequent new paddock, resulting in bites with high organic matter digestibility (OMD) value and CP content and a low fibre content at the beginning of each paddock utilisation. These changes could induce significant day-to-day variations of the milk FA composition. The milk fat proportions of 16:0, saturated FA and branched-chain FA decreased, whereas proportions of de novo-synthesised FA, 18:0, c9-18:1 and 18:2n-6 increased at paddock change. During LD plot utilisation, the heterogeneity of the vegetation allowed the cows to select vegetative patches with higher proportion of leaves, CP content, OMD value and the lowest fibre content. These small changes in CP, NDF and ADF contents of LD herbage and in OMD values, from the beginning to the end of the experiment, could minimally modify the ruminal ecosystem, production of precursors of de novo-synthesised FA and ruminal biohydrogenation, and could induce only small day-to-day variations in the milk FA composition.     

Effect of replacing grass silage with maize silage in the diet on bovine milk fatty acid composition

Even though extensive research has examined the role of nutrition on milk fat composition, there is less information on the impact of forages on milk fatty acid (FA) composition. In the current study, the effect of replacing grass silage (GS) with maize silage (MS) as part of a total mixed ration on animal performance and milk FA composition was examined using eight multiparous mid-lactation cows in a replicated 4 × 4 Latin square with 28-day experimental periods. Four treatments comprised the stepwise replacement of GS with MS (0, 160, 334 and 500 g/kg dry matter (DM)) in diets containing a 54 : 46 forage : concentrate ratio on a DM basis. Replacing GS with MS increased (P < 0.001) the DM intake, milk yield and milk protein content. Incremental replacement of GS with MS in the diet enhanced linearly (P < 0.001) the proportions of 6:0-14:0, decreased (P < 0.01) the 16:0 concentrations, but had no effect on the total milk fat saturated fatty acid content. Inclusion of MS altered the distribution of trans-18:1 isomers and enhanced (P < 0.05) total trans monounsaturated fatty acid and total conjugated linoleic acid content. Milk total n-3 polyunsaturated fatty acid (PUFA) content decreased with higher amounts of MS in the diet and n-6 PUFA concentration increased, leading to an elevated n-6 : n-3 PUFA ratio. Despite some beneficial changes associated with the replacement of GS with MS, the overall effects on milk FA composition would not be expected to substantially improve long-term human health. However, the role of forages on milk fat composition must also be balanced against the increases in total milk and protein yield on diets containing higher proportions of MS.     

Effects of flaxseed,raw soybeans and calcium salts of fatty acids on apparent total tract digestibility,energy balance and milk fatty acid profile of transition cows

Oilseeds offer some protection to the access of ruminal microorganisms and may be an alternative to calcium salts of fatty acids (FA), which are not fully inert in the ruminal environment. This study aimed to evaluate the effects of different sources of FA supplementation on apparent total tract nutrient digestibility, milk yield and composition, and energy balance (EB) of cows during the transition period and early lactation. We compared diets rich in C18:2 and C18:3 FA. Multiparous Holstein cows were randomly assigned to receive one of the four diets: control (n=11); whole flaxseed (WF, n=10), 60 and 80 g/kg (diet dry matter (DM) basis) of WF during the prepartum and postpartum periods, respectively; whole raw soybeans (WS, n=10), 120 and 160 g/kg (diet DM basis) of WS during the prepartum and postpartum periods, respectively; and calcium salts of unsaturated fatty acids (CSFA, n=11), 24 and 32 g/kg (diet DM basis) of CSFA during the prepartum and postpartum periods, respectively. Dry cows fed WF had higher DM and net energy of lactation (NE_L) intake than those fed WS or CSFA. The FA supplementation did not alter DM and NDF apparent total tract digestibility, dry cows fed WF exhibited greater NDF total tract digestion than cows fed WS or CSFA. Feeding WS instead of CSFA did not alter NE_L intake and total tract digestion of nutrients, but increased milk fat yield and concentration. Calculated efficiency of milk yield was not altered by diets. FA supplementation increased EB during the postpartum period. Experimental diets increased long-chain FA (saturated and unsaturated FA) in milk. In addition, cows fed WS and CSFA had higher C18:1 trans-11 FA and C18:2 cis, and lower C18:3 FA in milk than those fed WF. Furthermore, cows fed CSFA had higher C18:1 trans-11 and cis-9, trans-11 FA than cows fed WS. Although supplemental C18:2 and C18:3 FA did not influence the milk yield of cows, they positively affected EB and increased unsaturated long-chain FA in milk fat.     

Predicting duodenal flows and absorption of fatty acids from dietary characteristics in ovine and bovine species: a meta-analysis approach

Dietary and ruminal factors modify the ruminal biohydrogenation (RBH) of polyunsaturated fatty acids (FA), with duodenal FA flows being quantitatively and qualitatively different from FA intake. Using a meta-analysis approach from a database on duodenal flows of FA in ruminants, this study aimed to determine predictive equations for duodenal and absorbed flows of saturated FA, C18:1, C18:2 and C18:3 isomers, odd- and branched-chain FA (OBCFA), C20:5n-3, C22:5n-3 and C22:6n-3 and to quantify the effects of dietary and digestive factors on those equations. The database was divided into four subsets: forage, seed, vegetable oils or animal fats (oil/fat), and fish products (fish) subsets. Models of duodenal and absorbed FA flows were obtained through variance–covariance analysis. Effects of potential interfering factors (conservation mode and botanical families of forages, lipid source, technological processing of lipid supplements, diet composition and animal characteristics) were analysed. We obtained 83 models for duodenal FA flows as a function of FA intake for saturated FA (C14:0, C16:0 and C18:0), C18:1, C18:2 and C18:3 isomers and seven other models for OBCFA. For the seed/oil/fat subset, intakes of total C18:3, C18:2 and starch content increased the duodenal t11-C18:1 flow with 0.08, 0.16 and 0.005 g/kg of dry matter intake (DMI), respectively, whereas intake level [(DMI×100)/BW] decreased it. The c9c12c15-C18:3 RBH was higher for oil/fat than seed (96.7% v. 94.8%) and a protective effect of Leguminosae v. Gramineae against RBH for that FA appeared in the forage subset. The duodenal C17:0 flow increased with starch content and decreased with ruminal pH, respectively, whereas duodenal iso-C16:0 flow decreased with dietary NDF content for the seed/oil/fat subset. The duodenal C20:5n-3, C22:5n-3 and C22:6n-3 flows depended on their respective intake and the inhibitory effect of C22:6n-3 on duodenal C18:0 flow was quantified. Thirteen models of absorbed FA flows were performed depending on their respective duodenal flows. This study determined the effects of different qualitative and quantitative dietary and digestive factors, allowing for improved predictions of duodenal and absorbed FA flows.     

The identification of QTL that affect the fatty acid composition of milk on sheep chromosome 11

In this work, we analysed 11 genetic markers localized on OAR11 in a commercial population of Spanish Churra sheep to detect QTL that underlie milk fatty acid (FA) composition traits. Following a daughter design, we analysed 799 ewes distributed in 15 half‐sib families. Eight microsatellite markers and three novel SNPs identified in two genes related to fatty acid metabolism, acetyl‐CoA carboxylase α (ACACA) and fatty acid synthase (FASN), were genotyped in the whole population under study. The phenotypic traits considered in the study included 22 measurements related to the FA composition of the milk and three other milk production traits (milk protein percentage, milk fat percentage and milk yield). Across‐family regression analysis revealed four significant QTL at the 5% chromosome‐wise level influencing contents of capric acid (C10:0), lauric acid (C12:0), linoleic conjugated acid (CLA) and polyunsaturated fatty acids (PUFA) respectively. The peaks of the QTL affecting C10:0 and PUFA contents in milk map close to the FASN gene, which has been evaluated as a putative positional candidate for these QTL. The QTL influencing C12:0 content reaches its maximum significance at 58 cM, close to the gene coding for the glucose‐dependent insulinotropic polypeptide. We were not able to find any candidate genes related to fat metabolism at the QTL influencing CLA content, which is located at the proximal end of the chromosome. Further research efforts will be needed to confirm and refine the QTL locations reported here.     

Influence of feeding whole sunflower seed and extruded linseed on production of dairy cows, rumen and plasma constituents, and fatty acid composition of milk

Holstein cows were fed total mixed rations (TMR) supplemented with protected palm fat (PPF), whole sunflower seed (WSS) or extruded linseed (ELS) for 100 days. Percentage of dietary crude fat was 5.3, 5.1 and 5.1, respectively. Diet had no (p > 0.05) effect on feed intake, milk yield or milk protein content. Percentage of milk fat and yield of fat--corrected milk were significantly increased when diets were supplemented with WSS and ELS. Feeding PPF resulted in the lowest (p < 0.05) ruminal concentration of volatile fatty acids. No significant dietary effect on plasma characteristics was observed. Concentration of polyunsaturated fatty acids (PUFA) was higher (p < 0.05), and PUFA n-6/n-3 ratio lower (p < 0.05), in the milk fat from cows fed ELS compared to WSS. Supplementation of TMR with oilseeds compared to PPF increased the content of CLA in milk fat (p < 0.005) and decreased its atherogenicity, primarily due to a significant reduction of palmitic acid concentration. Both oilseeds significantly improved the spreadability index of manufactured butter. ELS, but not WSS, increased the susceptibility of milk fat to oxidation (p < 0.05). It can be concluded that feeding of oilseeds to dairy cows improved nutritional quality of milk fat, with supplementation with ELS producing an even more desirable milk fatty acid profile than WSS supplementation.     

Inclusion of cocoa by-product in the diet of dairy sheep: Effect on the fatty acid profile of ruminal content and on the composition of milk and cheese

In this study, we hypothesized that dietary cocoa bean shell (CBS) as a partial replacer of human edible cereal grains in the diet of lactating ewes may affect performance and milk and cheese composition. Twenty Comisana lactating ewes allotted into control (CTRL; n = 10) or cocoa (CBS; n = 10) group received alfalfa hay ad libitum and 800 g of conventional (CTRL) or experimental (CBS) concentrate containing 11.7% CBS to partially replace corn and barley of the CTRL concentrate. Milk yield and composition did not differ between groups, and only urea concentration was lower in CBS milk. Dietary CBS increased cheese fat and reduced protein percentage in CBS group. Fatty acid composition of rumen content partially reflected that of the ingested diet, with total saturated fatty acids (SFA), total monounsaturated fatty acids (MUFA), 16:0, 18:0 and 18:1c9 greater in the CBS group. Moreover, all the identified trans- and cis-18:1 isomers were greater in CBS rumen content. Milk and cheese showed a similar fatty acid composition. Total MUFAs were greater in milk and cheese of CBS, mainly due to the proportion of 18:1c9, and conversely, total polyunsaturated fatty acids (PUFA), PUFAn-6 and PUFAn-6-to-PUFAn-3 ratio was greater in CTRL group. Concluding, the inclusion of CBS in the diet of lactating ewes within the limit imposed by the current legislation did not cause detrimental effects on animal performance and milk composition. Interestingly, dietary CBS reduced milk urea concentration probably due to the phenols contained in CBS concentrate. However, our results support that biohydrogenation was weakly impaired by dietary CBS. Finally, CBS negatively affected cheese nutritional characteristics due to lower protein and greater fat content, but improved fat health indexes in milk and cheese.     

Herbage utilisation method affects rumen fluid and milk fatty acid profile in Holstein and Montbéliarde cows

Compared with maize silage- and concentrate-based diets, herbage-based diets were repeatedly shown to favourably influence the milk fatty acid (FA) profile. However, it is unclear how the herbage feeding mode (grazing vs indoor green-feeding) and conservation (fresh herbage vs hay vs silage) modify the milk FA profile. Therefore, the aim of the present experiment was to investigate the effect of different herbage utilisation methods (including herbage feeding mode and herbage conservation method) on the ruminal biohydrogenation of dietary FA and the consequences on the milk FA composition in cows of two breeds (Holstein and Montbéliarde). Concomitant effects of botanical composition and phenological stage of the herbage on milk FA profile were controlled for by harvesting barn-dried hay and silage simultaneously as first cut from the same ryegrass-dominated grassland in a semi-mountainous region. Seven weeks later, the first regrowth of the same plot was used as fresh herbage, either grazed or fed indoor (indoor green-feeding). Twenty-four Montbéliarde and 24 Holstein cows were randomly allocated to four groups of 12 cows balanced by breed, parity, and milk yield. In a free-stall barn, three groups were given ad libitum access to hay, silage, or fresh herbage, respectively. The fourth group was strip-grazing. All cows were supplemented with 3 kg DM/day of the same energy-rich concentrate. After 2 weeks of adaptation to the forage, samples of forage, concentrate, milk, blood, and rumen fluid were collected. Fatty acid composition of forages, rumen fluid, and milk was analysed by gas chromatography. Haymaking reduced total FA content of the herbage, in particular that of linoleic acid (LA) and α-linolenic acid (ALA). Still, rumen fluid lipids of hay-fed cows had the highest proportion of rumenic acid, LA, ALA, and total polyunsaturated fatty acids (PUFAs). Milk fat from hay-fed cows had the highest proportion of LA, and the apparent transfer rates from feed to milk of LA and ALA were higher in hay-fed cows than in silage-fed cows. The proportion of PUFAs was highest in milk fat from grazing and indoor green-fed Montbéliarde cows and lowest in silage-fed cows of both breeds. In conclusion, the herbage utilisation method affects the ruminal biohydrogenation of LA and ALA, whereby herbage drying particularly increases their transfer from herbage to milk.     

Milk fatty acid profile of Peruvian Criollo and Brown Swiss cows in response to different diet qualities fed at low and high altitude

Two identical experimental protocols were followed at 200 and 3,600 m above sea level (a.s.l.) determining the changes of the milk fatty acid (FA) profile of Brown Swiss (BS) and indigenous Peruvian Criollo cows (CR) as a response to diets which were designed to cover the variation in feed quality caused by season. At each site (altitude), six BS and six CR cows, adapted to >3,500 m a.s.l., were fed three dietary treatments (DS, dry-season forage; RS rainy-season forage; OC, diet optimised to meet the cow's requirements) in a 2 × 2 × 3-factorial arrangement. Intakes of FA and milk yield increased from diet DS (low quality diet) to RS and OC (high quality diet) for both cow types. Milk fat proportions of conjugated linoleic acid (CLA), C18:3 c9,c12,c15, total n-3 and polyunsaturated FA (PUFA) were highest (p < 0.05) with diet OC and higher in the lowlands than in the highlands. Low intakes of diet DS obviously resulted in a ruminal energy deficiency and body lipid mobilisation. The ruminal energy deficiency with diet DS was especially pronounced in BS, apparently reducing biohydrogenation rate and leading to lower proportions of C18:0 and higher proportions of C18:3 c9,c12,c15 in milk fat (p < 0.05). Especially C18:3 c9,c12,c15 intake did not concur with its proportion in milk fat, suggesting a strong dependence on energy status. Milk yield and FA excretion with milk were higher for BS than for CR (p < 0.05) with all three diets although milk fat content was lower (p < 0.05) for BS than CR. Milk fat of BS was richer in CLA and PUFA than milk fat of CR (p < 0.05). The desaturase indices for 18 FA were also higher for BS than CR (p < 0.05), suggesting a slightly higher Δ9-desaturase activity for BS, especially with diet DS. Milk fat content was generally higher at the high altitude than at the lowland site (p < 0.05), whereas the FA profile was unexpectedly similar across sites. Various interactions were found among diet type, cow type and altitude (site) indicating that a combination of these factors contributes to the characteristic FA profile of the respective milk.     

Effect of linseed supplementation of the gestation and lactation diets of dairy ewes on the growth performance and the intramuscular fatty acid composition of their lambs

In this study, we investigated the effects of maternal gestation and/or lactation diets supplemented with extruded linseed (rich in 18:3n-3) on growth performance and long-chain polyunsaturated faaty acid (PUFA) accumulation in muscle tissues of suckling lambs. A total of 36 dairy ewes were fed a control diet (CON) and a diet containing linseed (LIN) during the last 8 weeks of gestation and/or the first 4 weeks of lactation. The four dietary treatments consisted of the following gestation/lactation feeding treatments: CON/CON, CON/LIN, LIN/LIN or LIN/CON. The lambs born from ewes fed the aforementioned diets were reared exclusively on milk and were slaughtered at 4 weeks of age. Profiles of ewes’ milk fatty acids and that of intramuscular fat (IMF) of leg muscles from lambs were determined. Compared with the CON/CON, LIN/CON offspring tended to grow slower and to have reduced cold carcass weights. Moreover, the LIN supplementation only in the prepartum period (LIN/CON) resulted in greater PUFAn-3 accumulation in the IMF compared with the CON/CON offspring due to increased 20:5n-3 (1.20 v. 0.64 mg/100 mg of total FA), 22:5n-3 (1.91 v. 1.46;) and 22:6n-3 (1.25 v. 0.89) contents, respectively. Compared with the CON/CON diet, providing LIN only during lactation (CON/LIN) caused a greater PUFAn-3 content in the IMF mainly due to a greater 18:3n-3 (1.79 v. 0.75 mg/100 g total FA) concentration. Continuous PUFAn-3 exposure, both via the maternal gestation and lactation diet, had no additive effects on PUFAn-3 accumulation in tissues. The results suggest that linseed, as an 18:3n-3 source, seems to be more efficient in increasing long-chain PUFAn-3 in fetal than in suckling lamb tissues.     

The effect of fish oil supplementation of pregnant and lactating ewes on milk production and lamb performance

Supplementation of pregnant ewes with long-chain n-3 polyunsaturated fatty acids (PUFA) demonstrably improves indicators of neonatal lamb vigour, potentially improving the number of lambs reared per ewe. The present study investigated the effect of supplementing ewes with fish oil and vitamin E (α-tocopherol acetate) throughout both pregnancy and lactation on the performance of lactating ewes and sucking lambs. Forty-eight ewes were supplemented with one of four concentrates containing either Megalac or fish oil plus a basal (50 mg/kg) or supranutritional (500 mg/kg) concentration of vitamin E from 6 weeks pre-partum until 4 weeks post partum in a two-by-two factorial randomised-block design. All concentrates were formulated to contain approximately 60 g/kg supplemental fatty acids. Ewes were housed, penned on sawdust and offered straw ad libitum. Blood samples were taken from ewes and lambs at intervals throughout the experiment and milk samples were obtained at 21 days into lactation. There was no notable effect of dietary vitamin E concentration upon ewe or lamb performance. Ewe dry-matter (DM) intake and yield were unaffected by dietary treatment, although ewes fed fish oil lost less weight during lactation (-1.88 kg compared with -3.97 kg for Megalac-supplemented ewes; P < 0.01). Milk fat concentrations (67.3 g/kg compared with 91.8 g/kg; P < 0.01) and yields (6.65 g/h v. 9.26 g/h; P < 0.01) were reduced in ewes fed fish oil and these decreases were associated with lower litter-growth rates (0.49 g/day compared with 0.54 g/day; P < 0.05). Milk protein yield was increased by fish oil supplementation (3.82 g/h) compared with Megalac supplementation (3.28 g/h; P < 0.05); moreover, there was an interaction between fat source and vitamin E concentration in that both protein concentration and yield were significantly lower in milk from ewes fed treatment with Megalac + basal vitamin E (MB) compared with the other three treatments. Fish oil supplementation increased the concentrations of C18:1 trans-, cis-9, trans-11 conjugated linoleic acid (CLA), C20:5 (n-3) and C22:6 (n-3) within ewe plasma, milk and lamb plasma. The mechanisms by which fish oil supplementation affects milk composition warrants further investigation.     

Influence of feeding whole sunflower seed and extruded linseed on production of dairy cows,rumen and plasma constituents,and fatty acid composition of milk

Holstein cows were fed total mixed rations (TMR) supplemented with protected palm fat (PPF), whole sunflower seed (WSS) or extruded linseed (ELS) for 100 days. Percentage of dietary crude fat was 5.3, 5.1 and 5.1, respectively. Diet had no (p > 0.05) effect on feed intake, milk yield or milk protein content. Percentage of milk fat and yield of fat – corrected milk were significantly increased when diets were supplemented with WSS and ELS. Feeding PPF resulted in the lowest (p < 0.05) ruminal concentration of volatile fatty acids. No significant dietary effect on plasma characteristics was observed. Concentration of polyunsaturated fatty acids (PUFA) was higher (p < 0.05), and PUFA n-6/n-3 ratio lower (p < 0.05), in the milk fat from cows fed ELS compared to WSS. Supplementation of TMR with oilseeds compared to PPF increased the content of CLA in milk fat (p < 0.005) and decreased its atherogenicity, primarily due to a significant reduction of palmitic acid concentration. Both oilseeds significantly improved the spreadability index of manufactured butter. ELS, but not WSS, increased the susceptibility of milk fat to oxidation (p < 0.05). It can be concluded that feeding of oilseeds to dairy cows improved nutritional quality of milk fat, with supplementation with ELS producing an even more desirable milk fatty acid profile than WSS supplementation.     

Effect of extruded linseed supplementation on blood metabolic profile and milk performance of Saanen goats

This study assessed the effects of dietary supplementation with extruded linseed on milk yield and composition, milk fatty acid (FA) profile and renal and hepatic metabolism of grazing goats in mid-lactation. Forty Saanen goats were divided into two isoproductive groups: one group was fed the control diet (CON) composed of hay and pelleted concentrate and the other group was supplemented with additional 180 g/day of extruded linseed (LIN; dry matter basis), which supplied 70 g/day of fat per head for 9 weeks. Animals grazed on pasture for ∼3 h/day after the first of the 2 daily milkings. Milk samples were collected weekly and analyzed for fat, protein, lactose, milk urea nitrogen (MUN) and somatic cell count. Blood samples were collected every 2 weeks and analyzed for total bilirubin, creatinine, aspartate transaminase (AST), alanine transaminase (ALT), gamma glutamyl transpeptidase, alkaline phosphatase, total protein and urea nitrogen. Milk yield was higher in the LIN than in the CON group (2369 v. 2052 g/day). LIN group had higher milk fat (37.7 v. 33.4 g/kg) and protein (30.7 v. 29.1 g/kg) concentration and lower MUN (35.0 v. 43.3 mg/dl) than CON group. Goats fed LIN had greater proportions of 18:1 trans11, 18:2 cis9trans11 and total polyunsatured fatty acids n-3 in milk fat, because of higher 18:3n-3 and 20:5n-3 FA, and lower proportions of short- and medium-chain FAs than goats fed CON. All kidney and liver function biomarkers in serum did not differ between dietary groups, except for AST and ALT, which tended to differ. Extruded linseed supplementation to grazing mid-lactating goats for 2 months can enhance the milk performance and nutritional profile of milk lipids, without altering the general hepatic and renal metabolism.     

Untersuchungen zur ernährungsphysiologischen Bedeutung von NPN-Verbindungen

The aims of the experiment were to investigate the variation in ruminal fermentation, milk performance and milk fatty acid profile triggered by induced subacute ruminal acidosis (SARA); and to evaluate the ability of beet pulp (BP) as a replacement for ground maize in order to alleviate SARA. Eight Holstein-Friesian cows were fed four diets (total mixed rations) during four successive periods (each of 17 d): (1) without wheat (W0); (2) with 10% finely ground wheat (FGW) (W10); (3) with 20% FGW (W20); (4) with 20% FGW and 10% pelleted BP (BP10). Inducing SARA by diet W20 decreased the daily mean ruminal pH (6.37 vs. 5.94) and the minimum ruminal pH (5.99 vs. 5.41) from baseline to challenge period. Ruminal concentrations of total volatile fatty acid, propionate, butyrate, valerate and isovalerate increased with the W20 compared with the W0 and W10 treatments. The substitution of BP for maize increased the minimum ruminal pH and molar percentage of acetate and decreased the molar percentage of butyrate. The diets had no effect on dry matter intake (DMI) and milk yield, but the milk fat percentage and yield as well as the amount of fat-corrected milk was reduced in the W20 and BP10 treatments. The cows fed the W20 diet had greater milk concentrations of C11:0, C13:0, C15:0, C14:1, C16:1, C17:1, C18:2n6c, C20:3n6, total polyunsaturated fatty acids (FA) and total odd-chain FA, and lower concentrations of C18:0 and total saturated FA compared with the cows fed the W0 diet. Therefore, it can be concluded that changes in ruminal fermentation, milk fat concentration and fatty acid profile are highly related to SARA induced by feeding high FGW diets, and that the substitution of BP for maize could reduce the risk of SARA in dairy cows.