不同形式的植物油对奶牛生产性能和瘤胃微生物区系的影响

试验研究了日粮中分别补充0(对照组)、2%亚麻籽油(亚麻籽油组)、2%大豆油(大豆油组)和等同2%植物油的10%膨化大豆(膨化大豆组)对奶牛生产性能和瘤胃微生物区系的影响。结果表明:饲喂亚麻油、大豆油和膨化大豆组奶牛的奶产量显著(P<0.05)高于对照组,而乳脂含量显著低于对照组(P<0.05),校正乳(FCM)产量各组间差异不显著(P>0.05)。饲喂亚麻油、大豆油或膨化大豆对奶牛瘤胃微生物图谱条带数量和区系的相似性指数无显著影响(P>0.05)。各处理组的白色瘤胃球菌、溶纤维丁酸弧菌和产琥珀酸丝状杆菌比例无显著性差异(P>0.05)。研究结果显示,日粮补充适宜水平的不同形式植物油可改善奶牛生产性能,但对瘤胃微生物区系无显著影响。     

Partially replacing sorghum silage with cactus (Opuntia stricta) cladodes in a soybean oil-supplemented diet markedly increases trans-11 18:1, cis-9, trans-11 CLA and 18:2 n-6 contents in cow milk

Based on low 18:0 contents observed in milk fat of cows fed cactus cladodes (CC), we hypothesized that including Opuntia stricta cladodes in a soybean oil (SO)-supplemented diet would promote incomplete rumen biohydrogenation of supplemental PUFA, leading to increased trans-11 18:1 and cis-9, trans-11 CLA contents in milk. Twelve Holstein cows were used in a two-period study: (a) Baseline: all cows received a total mixed ration (TMR) composed of sorghum silage (SS) and a concentrate containing no SO for 14 days; (b) Treatment: cows received one of the following SO-supplemented diets for 21 days: (1) SS-TMR: a TMR composed of SS and a SO-enriched concentrate, (2) CC-TMR: a TMR containing CC as a partial substitute for SS plus the SO-enriched concentrate, and (3) CC-PMR: same diet as in treatment 2, but CC were mixed with the SO-enriched concentrate and fed as a partial mixed ration (PMR). Both CC diets increased relative abundances of trans-11 18:1, cis-9, trans-11 CLA, and 18:2 n-6 in milk fat, whereas opposite effects were observed on 18:0 and cis-9 18:1. Proportion of 18:2 n-6 increased, and cis-9, trans-11 CLA tended to increase with CC-PMR as compared to CC-TMR, whereas 18:3 n-3 was higher with CC-PMR than with SS-TMR. Proportions of several odd- and branched-chain fatty acids, certain 18:1 isomers, and trans-9, cis-11 CLA changed with CC diets, notably with CC-PMR. Milk yield and intake of most nutrients (except fibre) increased or tended to increase with the CC diets, whereas gross milk composition was unaltered. Stearoyl-CoA desaturase-1 index for C18 (SCD₁₈) was higher with CC-PMR than with SS-TMR, and milk n-6:n-3 FA ratio and apparent transfer of 18:2 n-6 to milk increased with CC diets. These results indicate that Opuntia stricta cladodes can be a valuable feed ingredient for improving the nutraceutical value of milk fat.     

Effect of monensin and vitamin E on milk production and composition of lactating dairy cows

Feeding unsaturated oils to lactating dairy cows impair ruminal biohydrogenation (BH) of unsaturated fatty acids (USFA) and increase ruminal outflow of BH intermediates such as trans‐10, cis‐12 CLA that are considered to be potent inhibitors of milk fat synthesis. Supplementing lactating dairy cow’s rations containing plant origin oils with monensin and/or vitamin E may minimise the formation of trans‐10 isomers in the rumen, thereby preventing milk fat depression. Therefore, this study was conducted to evaluate the effects of monensin and vitamin E supplementation in the diets of lactating dairy cows containing whole cottonseed, as the main source of FA on feed intake, milk production and composition, milk fatty acid profile, efficiency of nitrogen (N) utilisation, efficiency of net energy (NE) utilisation and nutrients digestibilities. Four multiparous Holstein lactating dairy cows (86 ± 41 days in milk) were assigned to a balanced 4 × 4 Latin square design. Each experimental period lasted 21 days with a 14 days of treatment adaptation and a 7 days of data collection. The control diet was a total mixed ration (TMR) consisted of 430 g/kg forage and 570 g/kg of a concentrate mixture on dry matter (DM) basis. Cows were randomly assigned to one of the four dietary treatments including control diet (C), control diet supplemented with 150 mg of vitamin E/kg of DM (E), control diet supplemented with 24 mg of monensin/kg of DM (M) and control diet supplemented with 150 mg of vitamin E and 24 mg of monensin/kg of DM (EM). Dry matter intake (DMI) ranged from 19.1 to 19.5 kg/d and was similar among the dietary treatments. Dietary supplementation with vitamin E or monensin had no effect on milk production, milk fat, protein and lactose concentrations, efficiency of utilisation of nitrogen and net energy for lactation (NE_L). Digestibility of DM, organic matter (OM), crude protein (CP) and ether extract (EE) was not affected by the dietary treatments. Digestibility of neutral detergent fibre (NDF) was higher in cows fed with the M and EM diets in relation to those fed the C and E diets. The concentrations of C4:0, C6:0, C8:0, C10:0, C12:0, C14:0, C15:0, trans‐10‐16:1, cis‐9‐16:1, 17:0, 18:0, trans‐11‐18:1, cis‐9‐18:1, cis‐9, trans‐11 conjugated linoleic acid (CLA), trans‐10, cis‐12 CLA, and 18:3n‐3 FA in milk fat were not affected by the dietary supplementations. While feeding the M diet tended to decrease milk fat concentration of C16:0, the milk fat concentration of C18:2n‐6 FA tended to be increased. Dietary supplementation with vitamin E or monensin had no effect on milk fat concentrations of saturated, unsaturated, monounsaturated, polyunsaturated, short chain and long chain FA, but feeding the M diet numerically decreased milk fat concentration of medium chain fatty acids (MCFA). The results showed that vitamin E and/or monensin supplementations did not improve milk fat content and did not minimise the formation of trans‐10 FA isomers in the rumen when whole cottonseed was included in the diet as the main source of fatty acids.     

Influence of the calf presence during milking on dairy performance,milk fatty acid composition,lipolysis and cheese composition in Salers cows during winter and grazing seasons

The milking of Salers cows requires the presence of the calf. The removal of the calf would simplify the milking routine, but it could also modify the milk yield and the milk and cheese composition. Therefore, the aim of this experiment was to evaluate the effect of calf presence during milking during sampling period (winter or grazing periods), on dairy performance, milk fatty acid (FA) composition, lipolysis and cheese yield and composition. Nine and 8 Salers lactating cows were milked in the presence (CP) or absence (CA) of their calves respectively. During winter, the cows were fed a hay‐based diet and then they only grazed a grassland pasture. Calf presence during milking increased milk yield and milk 16:0 concentration and decreased milk fat content and milk total odd‐ and branched‐chain FA (OBCFA) concentrations. Calf presence only increased initial lipolysis in milk collected during the winter season. Milk from CP cows compared to CA cows resulted in a lower cheese yield and ripened cheeses with lower fat content. Milk from the grazing season had lower saturated medium‐chain FA and OBCFA concentrations and higher 18:0, cis‐9‐18:1, trans‐11‐18:1 and cis‐9, trans‐11‐CLA concentrations than that from the winter season. Initial milk lipolysis was higher in the winter than in the grazing season. These variations could be due to seasonal changes in the basal diet. Furthermore, the effect of calf presence during milking on milk fat composition was lower than that on dairy performance, cheese yield and composition. Removing the calf during the milking of Salers cows seems feasible without a decrease in milked milk, and with a positive effect on cheese yield and fat content, under the condition that we are able to select cows having the capacity to be milked easily without the calf.     

Conjugated linoleic acids (CLA) moderate negative responses of heat-stressed cows

The objective of this study is to examine whether CLA would help to improve negative responses in lactating cows during heat stress. During a 2-week adjustment period, all cows were fed a control diet supplemented with 400 g of calcium salts of palm oil fatty acids. After the adjustment period, cows (n = 9 per group) were randomly assigned by block to one of four treatments: control or three diets containing 100, 200, or 400 g of CLA (70% of which were mixed isomers of CLA). Milk fat percentage and yield decreased by supplementation of CLA (P < 0.01), but milk yield and other nutrient components did not vary (P > 0.05). The concentrations of short and medium-chain fatty acids (C4–C14) decreased and long-chain fatty acids (C18) increased in milk fat for cows fed CLA. Moreover, the contents of cis9, trans11 and trans10, cis12-CLA in milk fat increased markedly (P < 0.01). Respiration rate was lower (P < 0.05) for cows fed 200 g of CLA and rectal temperature decreased (P < 0.01) in all CLA groups during day 15 to day 28. Contents of aspartate aminotransferase, creatine kinase, thyroxin, potassium, sodium, calcium and chlorine were altered by CLA supplements, whereas other plasma parameters were not affected (P > 0.05). Lower concentrations of aspartate aminotransferase and creatine kinase in blood for cows fed 200 g or 400 g of CLA suggested that CLA protected cows from muscle damage. In addition, higher concentrations of electrolytes and thyroxin in blood in these groups suggested that CLA could improve heat stress situations in cows. Overall, the results showed that supplementations with 200 or 400 g/day of CLA moderated the negative responses in heat-stressed cows.     

Milk fatty acid profile from cows fed with mixed rations and different access time to pastureland during early lactation

Milk fatty acid (FA) profiles were determined in Holstein cows (n = 27) fed total mixed rations (TMR) ad libitum (G0) or diet composed by TMR (50% dry matter [DM] offered) plus grazing of pasture with 6 hr of access time to paddock in one session (G1) or 9 hr in two sessions (G2) at 45 days in milk (DIM). Moreover, milk FA was determined at 65 DIM when G0 cows turned out to G1 diet without adaptation period (Post‐G0), G1 remained as controls. Milk FA was quantified using gas chromatography and mass spectrometry. Preformed FA at 45 DIM was greater (+27%) for G2 than G0 cows (p < .05). Stearic acid (C18:0) was 30% greater for G2 cows (p < .05). De novo FA was lowest for G2 cows (p < .05). Conjugated linoleic acid (CLA) did not differ (p < .12), while vaccenic acid (C18:1trans) was twofold greater for grazing treatments (p < .01). Linolenic acid [C18:3(n‐3)] was greatest for G2 and lowest for G0 cows (p < .01). Omega 6 FA was greater for G0 than grazing cows, mainly due to linoleic acid [18:2cis(n‐6); p < .05]. These results determined that n‐6/n‐3 ratio was almost threefold greater for G0 than grazing cows (p < .001). When diet of G0 cows changed to include pasture (Post‐G0), preformed FA increased (p < .05), explained mainly by the increase (p < .05) of stearic (C18:0) and C18:1trans, while de novo FA tended to decrease (p < .1). Moreover, the amount of CLA and C18:3(n‐3) tended to increase (p < .1) in Post‐G0 cows. Offering 50% of dietary DM from pasture modified milk FA profile in early lactation potentially beneficial for human health. When TMR‐fed cows were turned out to 50% pasture, milk FA profile reflected dietary change without need of an adaptation period.     

Concentrations of retinol and tocopherols in the milk of cows supplemented with conjugated linoleic acid

This study was performed to investigate the hypothesis that supplementation of conjugated linoleic acid (CLA) changes the concentrations of retinol and tocopherols in the milk of cows. To investigate this hypothesis, Holstein cows received daily from 3 weeks ante‐partum to 14 weeks post‐partum either 172 g of a CLA‐free rumen‐protected control fat (control group, n = 20) or the same amount of a rumen‐protected CLA fat, supplying 4.3 g of cis‐9, trans‐11 CLA and 3.8 g of trans‐10, cis‐12 CLA per d (CLA group, n = 20). Milk samples (collected at weeks 1, 3, 5, 8 and 11 of lactation) were analysed for retinol, α‐ and γ‐tocopherol concentrations. Milk of cows supplemented with CLA had higher concentrations of retinol (+34%), α‐tocopherol (+44%) and γ‐tocopherol (+21%) than milk of control cows (p < 0.05). The daily output of these vitamins via milk was also greater in cows of the CLA group than in cows of the control group (+36, 50 and 24% for retinol, α‐tocopherol and γ‐tocopherol, respectively, p < 0.05). In agreement with higher concentrations of tocopherols, concentrations of thiobarbituric acid‐reactive substances, determined in milk of week 5, were lower in cows of the CLA group than in control cows, indicative of a lower susceptibility of milk lipids to peroxidation. Plasma concentrations of retinol and α‐tocopherol, determined at 1 and 5 weeks post‐partum, were not different between the two groups of cows. In conclusion, this study shows that supplementing dairy cows with a moderate amount of CLA causes an increase of the concentrations of vitamins A and E in the milk and results in an increased output of those vitamins via milk. These effects might be beneficial with respect to the nutritional value of dairy products and the susceptibility of milk fat to oxidative deterioration.     

Effect of supplementation of soy sauce oil and Ca salts of fatty acids on rumen fermentation,milk production and conjugated linoleic acid in milk of dairy cows

Eight cows were used to evaluate the effects of supplementation of soy sauce oil (SO) or Ca salts of fatty acids (FA) on rumen fermentation and milk production. The control diet (CO) consisted mainly of hay, corn silage and a concentrate. In the experimental diets, 400 g/day per cow of SO or FA (soybean oil and rapeseed oil) was supplemented to the CO diet. Experimental period for the three treatments was 14 days, and milk samples were taken during the last 2 days and rumen sample was taken on the last day. Dry matter intake was not affected by the treatments. The number of rumen protozoa at 0 h increased by SO and FA diets. Total volatile fatty acids at 2 h after feeding of SO diet was decreased compared to CO. The milk composition yield did not differ among treatments, although the percentages of fat and protein were decreased by SO and FA diets. The proportions of C8–C16 fatty acids in milk fat decreased, and those of C18 increased by SO and FA diets. The proportion of cis‐9, trans‐11 conjugated linoleic acid in milk fat by SO and FA diets increased by 120% and 135%, respectively. In spite of the slight suppression of rumen fermentation by SO diet, negative effects on feed intake and milk production were not detected.     

Effect of linseed oil supplementation on performance and milk fatty acid composition in dairy cows

Thirty‐six Holstein‐Friesian crossbred lactating dairy cows were used to determine the effects of linseed oil supplementation on performance and milk fatty acid (FA) profile. Three treatments were as follows: basal diet (56:44 Roughage:concentrate [R:C] ratio, dry matter basis) supplemented with 500 g of palm oil as control (PO), 500 g mixture (1:1, w/w) of palm oil and linseed oil (POLSO) and 500 g of linseed oil (LSO). The LSO supplementation had no effects on total dry matter intake (DMI), milk yield and milk composition. Compared to control cows, cows supplemented with LSO increased milk concentrations of cis‐9,trans‐11 conjugated linoleic acid (CLA) and n‐3 FA (P < 0.05), particularly C18:3n‐3, C20:5n‐3 and C22:6n‐3. Feeding LSO reduced concentrations of milk short‐ and medium‐chain saturated fatty acids (P < 0.05) while it increased concentration of milk unsaturated fatty acids (P < 0.05). Milk proportions of n‐3 FA increased, whereas n‐6/n‐3 ratio decreased in the LSO as compared with the control (P < 0.05). In conclusion, supplementing dairy cows' diet based on corn silage with LSO at 500 g/day could improve the nutritional value of milk with potential health‐beneficial FA without detrimental effect on milk composition or cow's performance.     

Rumen-protected conjugated linoleic acid supplementation to dairy cows in late pregnancy and early lactation: effects on milk composition,milk yield,blood metabolites and gene expression in liver

Background

Conjugated linoleic acid (CLA) is a collective term for isomers of octadecadienoic acid with conjugated double-bond system. Thus, it was the objective to investigate whether milk composition and metabolic key parameters are affected by adding CLA to the diet of dairy cows in the first four weeks of lactation.

Methods

A study was carried out with five primiparous cows fed a CLA supplemented diet compared to five primiparous cows without CLA supplementation. CLA supplemented cows received 7.5 g CLA/day (i.e. 50% cis(c)9,trans(t)11- and 50% t10,c12-CLA) starting two weeks before expected calving and 20 g CLA/day (i.e. 50% c9,t11- and 50% t10,c12-CLA) throughout day 1 to 28 of lactation.

Results

The CLA supplement was insufficiently accepted by the animals: only 61.5% of the intended amount was ingested. Fed CLA were detectable in milk fat, whereas contents of c9,t11-CLA and t10,c12-CLA in milk fat were higher for CLA supplemented cows compared to the control group. On average over the entire treatment period, there was a decrease of saturated fatty acids (FA) in milk fat of CLA supplemented cows, combined with a higher content of monounsaturated and trans FA.Our study revealed no significant effects of c9,t11- and t10,c12-CLA supplementation either on milk yield and composition or on metabolic key parameters in blood. Furthermore the experiment did not indicate significant effects of c9,t11- and t10,c12-CLA-supplementation on gene expression of peroxisome proliferator-activated receptor-alpha (PPARα), PPARγ, sterol regulatory element-binding protein-1 and tumor necrosis factor-alpha in liver tissue.

Conclusions

Feeding c9,t11- and t10,c12-CLA during the first weeks after calving did not affect metabolic key parameters of blood serum or milk composition of fresh cows. Milk fatty acid composition was changed by feeding c9,t11- and t10,c12-CLA resulting in higher contents of these isomers in milk fat. High contents of long chain FA in milk fat indicate that CLA supplementation during the first four weeks of lactation did not affect massive peripheral lipomobilization.     

Concentration of conjugated linoleic acid in grazing sheep and goat milk fat

The conjugated linoleic acid (CLA) content of grazing sheep and goat milk fat, throughout their lactation period, was examined. Six sheep and six goat representative farms were selected at random and milk samples were taken at monthly intervals for fatty acids profile determination. Sheep and goat nutrition was based on natural grazing and on supplementary feeding during the winter months. From April onwards, grazing native pastures was the only source of feed for sheep and goats. The University farm whose sheep are kept indoors all year round without any grazing, was also used as reference. Fifteen individual milk samples were also taken in April from a sheep and goat farm respectively, in order to see the variability of CLA inside the farm. The results showed that: a. the CLA content of grazing sheep and goat milk fat increased significantly in April–May (early growth stage of grass) and then declined while that of indoors kept sheep was more or less constant during the same period, b. the isomers cis-9, trans-11 and trans-10, cis-12 of CLA were found in grazing sheep milk fat, while in indoors kept sheep and goats' milk fat only the cis-9, trans-11 isomer was found, c. the CLA content of sheep milk fat was much higher than that of goats, d. a negative correlation between sheep milk fat and CLA content was found and e. there was considerable variation in milk fat CLA content between sheep and goat farms and inside the farms.     

Rumen fermentation,milk production and conjugated linoleic acid in the milk of cows fed high fiber diets added with dried distillers grains with solubles

The effects of corn dried distillers grains with solubles (DDGS) feeding on rumen fermentation and milk production in cows were evaluated using diets high in neutral detergent fiber (NDF, 45.9–46.6%). The control diet (Control) consisted mainly of hay, corn silage and concentrates. In the experimental diets, the concentrates were replaced with DDGS as 10% dry matter (DM) (10%DDGS) and 20% DM (20%DDGS). Eight cows were used for each 14‐day treatment period. Effect of DDGS feeding on DM intake was not significant. Ruminal volatile fatty acids and ammonia‐N at 5 h after feeding of 20%DDGS were decreased compared to Control, whereas protozoal count at 2 h after feeding of 20%DDGS was higher than that of 10%DDGS. Milk yield of cows fed DDGS diets was greater than that of Control, although percentages of milk protein and solids‐not‐fat were decreased by DDGS diets. The proportions of C10:0, C12:0, C14:0 and C16:0 in the milk fat decreased, and those of C18:0, C18:1, C18:2 and cis‐9, trans‐11 conjugated linoleic acid (CLA) increased markedly with elevated DDGS. Increase in trans‐11 C18:1 was observed in the rumen fluid at 5 h after feeding. These findings suggest that DDGS feeding enhanced milk yield, as well as CLA synthesis under a high dietary NDF condition.     

瘤胃保护共轭亚油酸和亚油酸对奶牛产奶性能的影响

选择健康、泌乳月份与产奶量相近的多胎荷斯坦泌乳牛20头,随机分成5组,每组4头,研究日粮中添加商业来源的瘤胃保护共轭亚油酸钙盐(Ca-CLA)同时添加自然来源亚油酸(葵花油)对奶牛生产性能的影响。试验期为52d。对照组基础日粮为60%粗饲料(苜蓿、羊草、青贮)和40%精料(以DM为基础),处理组在对照组日粮基础上分别添加Ca-CLA100g/d·头(CLA)、葵花油350g/d·头(Sunf);Ca-CLA100g/d·头 葵花油350g/d·头(CLA Sunf),Ca-CLA50g/d·头 葵花油175g/d·头(1/2CLA 1/2Sunf)。结果表明:在奶牛日粮中,单独添加自然来源亚油酸产奶量较对照组差异不显著(P>0.05),而单独添加共轭亚油酸钙盐或与自然来源亚油酸高低不同剂量添加产奶量较对照组都分别显著提高2.20%、9.95%、11.16%,无论单独添加自然来源亚油酸或Ca-CLA或二者以高低不同剂量同时添加,牛奶的乳脂率较对照组都分别显著降低15.0%,6.24%,21.74%,14.35%。总之,奶牛日粮中同时添加Ca-CLA和自然来源亚油酸能显著提高产奶量,降低乳脂率,并且,减少Ca-CLA的添加量同时添加自然来源亚油酸可以达到高剂量添加Ca-CLA相同的效果。     

Inflammatory and metabolic responses to an intramammary lipopolysaccharide challenge in early lactating cows supplemented with conjugated linoleic acid

Supplementation of dairy cows with trans‐10, cis‐12 conjugated linoleic acid (CLA) allows nutrient repartitioning despite an energy deficiency in early lactation, which might be a benefit for the immune system, too. In this study, we investigated potential nutrient sparing effects of CLA in early lactating cows with low plasma glucose concentrations exposed to an intramammary lipopolysaccharide (LPS) challenge. Fifteen multiparous Holstein cows were exposed to an intramammary LPS challenge in week 4 p.p. Eight cows (CLA) were supplemented daily with 70 g of lipid‐encapsulated CLA (6.8 g trans‐10, cis‐12 and 6.6 g of the cis‐9, trans‐11 CLA isomer; CLA) and seven cows with 56 g of control fat (CON). Blood samples were obtained every 30 min along with rectal temperature, heart and respiratory rate, and milk samples were taken hourly until 10 hr after the LPS application. Plasma was analysed for concentrations of glucose, free fatty acids, beta‐hydroxybutyrate (BHB), cortisol, insulin and glucagon. In milk, somatic cell count and activity of lactate dehydrogenase were determined. Initial plasma glucose concentration was lower in CLA than in CON. During the immunostimulation, CLA had higher glucose concentrations than CON, and BHB decreased distinctly in CLA, whereas CON cows maintained BHB concentration at a lower level. Body temperature in CLA increased earlier, the difference between peak and basal temperature was higher, and the decline thereafter occurred earlier. In conclusion, CLA supplementation of early lactating cows exposed to an intramammary LPS challenge affected local and systemic immune responses. We assume that CLA supplementation triggered glycogen storage. Cows supplemented with CLA provided more glucose and preferentially used BHB as an energy source during the immune response. The more intense metabolic and more concentrated endocrine responses support an immunomodulatory effect of CLA supplementation.     

Influence of percentage of concentrate in combination with rolled canola seeds on performance, rumen fermentation and milk fatty acid composition in dairy goats

The effect of rolled canola seeds (RCS, 0% or 20% of the dry matter (DM) of the concentrate) combined with percentage of concentrate (45% (L) vs. 65% (H) of the diet DM) on rumen fermentation characteristics, production parameters and fatty acid (FA) profile of milk fat was studied in 20 entire goats and 12 goats fitted with ruminal and duodenal cannula. Goats were fed TMR ad libitum for 15 weeks with the final 12 weeks as the test period. Individual milk samples were taken in weeks 5 and 11 to determine the FA profile of milk fat. Feeding the H diets increased NE_L intake, raw milk yield and yield of fat, protein and lactose. Feeding RCS increased fat corrected milk, milk fat content and fat yield. Combination of RCS and high percentage of concentrate increased fat corrected milk and fat yield. Milk protein content was not affected by dietary factors. Feeding the H diets increased the proportion of short-chain FA (C4:0–C8:0), each isomer of trans-C18:1 and c9,t11-C18:2 in milk at the expense of medium-chain FA with 11 to 17 C units. Feeding RCS decreased the proportion of medium-chain FA with 10 to 17 C units in milk and it increased that of C18:0, all isomers of trans-C18:1, c9-C18:1 and c9,t11-C18:2. Goats fed the H diets, and those fed the RCS had lower c9-C18:1/C18:0 and c9,t11-C18:2/t11-C18:1 ratios. Combination of RCS and high percentage of concentrate produced the highest proportion of all isomers of trans-C18:1 and c9,t11-C18:2 in milk, with the highest variability among the four diets for these FA. This was possibly related to between-goats differences in ruminal fermentation and to individual difference in desaturase activity in the mammary gland. It is concluded that feeding a high-concentrate diet combined with rolled canola seeds had a synergistic effect on the milk production and fat yield without alteration in milk protein content in dairy goats. This combination also resulted in changes in FA profile that may differently affect the nutritional value of goat milk for human health.     

Supplementation of dairy cows with a fish oil containing supplement and sunflower oil to increase the CLA content of milk produced at pasture

It has been shown that the cis 9, trans 11 isomer of conjugated linoleic acid (CLA) can be increased in milk by supplementation with fish oil and vegetable oils. Feeding a high level of oil, however, can impact negatively on gross milk composition. The principal aim of this study was to determine if relatively low levels of fish oil or sunflower oil, either alone or in combination, offered to dairy cows on pasture would increase the C18:2 cis 9, trans 11 CLA concentration in milk. Forty autumn-calved cows on a diet of grazed grass were assigned to 4 supplementation treatments: (i) No supplement (P), (ii) 255 g/day of sunflower oil (SO), (iii) 255 g/day of sunflower oil + 52.5 g/day of fish oil (SOFO), and (iv) 105 g/day of fish oil (FO). The fish oil was supplied in a proprietary product called Omega-3 Supplement which is a mixture of marine oils and an extracted oilseed meal and contains 500 g/kg of oil. The oils were fed in a concentrate mixture, which was offered at a rate of 3.0 kg/cow per day. The production of the cows was measured for 54 days and the milk fatty acid composition was determined on day 0 (immediately before the supplements were introduced) and on days 14, 28 and 42 after the treatments were imposed. Supplementation increased the yield of milk (P < 0.01), protein (P < 0.05) and lactose (P < 0.001), decreased milk fat (P < 0.05) and protein (P < 0.01) concentrations and increased (P < 0.01) lactose concentration. Type of oil did not significantly affect any production variable. The concentration of C18:1 trans 9 + C18:1 trans 11 (mainly C18:1 trans 11) (P < 0.001) and C18:2 cis 9, trans 11 CLA (P < 0.01) were greater on supplemented treatments than on P and the concentration of both were greater (P < 0.05) on FO than on SO. The results confirm that the concentration of C18:2 cis 9, trans 11 CLA can be increased further, from an already relatively high concentration in milk from pasture, by offering supplements containing a low level of fish oil either alone or in combination with sunflower oil.     

Occurrence of conjugated linoleic acid in ruminant products and its physiological functions

Milk and meat products derived from ruminants contain a mixture of positional and geometric isomers of C_18:2 with conjugated double bonds, and cis‐9, trans‐11C_18:2 (conjugated linoleic acid, CLA) is the predominant isomer. The presence of CLA in ruminant products relates to the biohydrogenation of unsaturated fatty acids by rumen bacteria. Although, it has been suggested that cis‐9, trans‐11 CLA is an intermediate that escapes complete ruminal biohydrogenation of linoleic acid, is absorbed from the digestive tract, and transported to tissues via circulation. Its major source is endogenous biosynthesis involving Δ⁹‐desaturase with trans‐11C_18:1 produced in the rumen as the substrate. CLA has recently been recognized in animal studies as a nutrient that exerts important physiological effects, including anticarcinogenic effects, prevention of cholesterol‐induced atherosclerosis, enhancement of the immune response, reduction in fat accumulation in body, ability to enhance growth promotion, antidiabetic effects and improvement in bone mineralization. The present review focused on the origin of CLA in ruminant products, and the health benefits, metabolism and physiological functions of CLA.     

Effect of raw soya bean particle size on productive performance and digestion of dairy cows

Differing soya bean particle sizes may affect productive performance and ruminal fermentation due to the level of fatty acid (FA) exposure of the cotyledon in soya bean grain and because the protein in small particles is more rapidly degraded than the protein in large particles, which influence ruminal fibre digestion and the amounts of ruminally undegradable nutrients. The objective of this experiment was to investigate the effects of raw soya bean particle size on productive performance, digestion and milk FA profile of dairy cows. Twelve Holstein cows were assigned to three 4 × 4 Latin squares with 21‐day periods. At the start of the experiment, cows were 121 days in milk (DIM) and yielded 30.2 kg/day of milk. Cows were fed 4 diets: (i) control diet (CO), without raw soya bean; (ii) whole raw soya bean (WRS); (iii) cracked raw soya bean in Wiley mill 4‐mm screen (CS4); and (iv) cracked raw soya bean in Wiley mill 2‐mm screen (CS2). The inclusion of soya beans (whole or cracked) was 200 g/kg on dry matter (DM) basis and partially replaced ground corn and soya bean meal. Uncorrected milk yield and composition were not influenced by experimental diets; however, fat‐corrected milk (FCM) decreased when cows were fed soya bean treatments. Soya bean diets increased the intake of ether extract (EE) and net energy of lactation (NE_L), and decreased the intake of DM and non‐fibre carbohydrate (NFC). Ruminal propionate concentration was lower in cows fed WRS than cows fed CS2 or CS4. Cows fed cracked raw soya bean presented lower nitrogen in faeces than cows fed WRS. The milk of cows fed WRS, CS2 and CS4 presented higher unsaturated FA than cows fed CO. The addition of raw soya bean in cow diets, regardless of the particle size, did not impair uncorrected milk yield and nutrient digestion, and increased the concentration of unsaturated FA in milk. Cows fed cracked raw soya bean presented similar productive performance to cows fed whole raw soya bean.     

Comparative study between sheep and goats on rumenic acid and vaccenic acid in milk fat under the same dietary treatments

A number of studies have shown that the rumenic acid (RA = cis-9 trans-11 C_18:2 CLA) content of milk fat is usually higher in sheep than in goats, due partly to different dietary regimens. An experiment was conducted with 12 lactating dairy ewes and 12 goats with the objective to compare the two animal species (sheep/goats) fed diet with the same forage/concentrate (F/C) ratio, on their milk fatty acids (FA) profile with emphasis on RA and vaccenic acid (VA) production. The experiment was carried out in three consecutive phases, lasted 3 weeks each, immediately after weaning of lambs and kids. In phase I, the ewes and the goats were fed according to their maintenance and lactation requirements, with 14 kg alfalfa hay, 4 kg wheat straw and 12 kg concentrate the 12 ewes (F/C ratio = 60/40), and with 14 kg alfalfa hay, 4 kg straw and 24 kg concentrate the 12 goats (F/C ratio = 43/57). In phase II, 14 kg alfalfa hay, 4 kg straw and 14 kg concentrate were offered daily to each group of sheep and goats, with a F/C ratio = 56/44. In phase III, all ewes and goats were fed individually with 0.8 kg alfalfa hay, 0.2 kg wheat straw and 0.8 kg concentrate daily with a F/C ratio = 56/44. The results showed that the different F/C ratio between sheep and goats diets, in phase I, changed significantly the milk FA profile, with no significant difference in RA and VA milk fat content between sheep and goats in phase I. In phases II (group feeding) and III (individual feeding), where sheep and goats fed with the same amount of food of the same F/C ratio, the sheep milk fat had higher RA and VA content compared to goats. In conclusion, these findings support the hypothesis that there are species differences, as RA and VA production concerns, which needs further investigation.     

Energy balance in lactating goats: Response to mixture of conjugated linoleic acid

The objective of this study was to determine the energy balance in early lactating local goats when supplemented with conjugated linoleic acid. Fifteen local goats from the north‐east of Mexico were used. Three treatments were evaluated: (a) Control (Base diet); (b) CLA 50 g; and (c) CLA 90 g. The CLA was a mixture of micro‐encapsulated FA, which supplied c9, t11 and t10, c12. Goats had an adaptation period of 2 weeks and 7 experimental weeks. The variables evaluated were body weight, DMI, milk yield, and fat, protein, and lactose yield, FA milk profile, and energy balance. The analysis of the data was analyzed as repeated measures using the PROC MIXED procedure and Tukey test (p < .05). In milk of goats from the treatment 90 g of the isomer t10, c12 CLA (p < .05) the milk fat content and milk fat yield with respect to the control treatment were reduced and the energy balance was improved. In goats treated with 11 g of t10, c12 CLA increased (p < .05) milk yield and milk lactose content. These results suggest that energy not used to synthesize dairy fat was used to increase milk yield and improve energy balance.