The objective was to reduce saturated fatty acids (SFA) and increase conjugated linoleic acid (CLA, cis-9, trans-11 C 18:2), α-linolenic ( cis-9, cis-12, cis-15 C 18:3) and docosahexaenoic (DHA, C 22:6) contents in milk from confined dairy cows in order to promote a healthier option. The work was carried out in a commercial farm (Talar) located in Laguna del Sauce, Maldonado (Uruguay). Twenty four cows were assigned to one of two treatments (12 cows per treatment) over a 6 weeks experimental period. Treatments consisted in a control total mixed ration (C-TMR) without supplementary lipids (L) or the same TMR with the addition of 0.144 kg/cow·day of algae and 0.72 kg/ cow·day of soybean oil (L-TMR). Chemical composition of the TMR (44.27% DM) averaged 15.94% for crude protein (CP), 38.20% neutral detergent fiber (NDF), 20.36% acid detergent fiber (ADF), 5.56% fat, 5.30% ash and 28.6% nonstructural carbohydrate (NSCH) with 1.81 Mcal/kg of net energy for lactation (NE L). After 39 days of feeding, individual milk samples were collected during three consecutive days. From the total milk collected, 20 ml were immediately used for chemical composition (Milko Scan) and 80 ml for analysis for milk FA profile. From week 3 onwards, milk production (kg/ cow·day) resulted higher ( P < 0.001) in L-TMR (36.9) compared to C-TMR (35.2). At week 6 of trial, the difference in milk production averaged 5.14% for L-TMR. Supplementary lipids reduced ( P < 0.002) milk fat concentration (g/100g) from 3.36 in C-TMR to 2.40 in L-TMR without effect ( P = 0.43) on milk protein content (C-TMR = 3.20; L-TMR = 3.07 g/100g). Milk lactose (C-TMR = 4.86, L-TMR = 4.69 g/100g) and urea nitrogen contents (C-TMR = 21.18, L-TMR = 17.33 g/100g) tended ( P < 0.056) to decrease in L-TMR as well as fat corrected milk output (C-TMR = 30.89, L-TMR = 29.49 kg/ cow·day, P < 0.098). Lipid supplementation reduced (-23%) milk con-tent of C 12:0 to C 16:0 FA averaging 45.19 in C-TMR and 34.74 g/100g in L-TMR ( P < 0.001). The atherogenic index (AI) of milk decreased ( P < 0.001) from 2.69 in C-TMR to 1.50 in L-TMR (-44.2%). Concentration (g/100g) of elaidic (C 18:1 trans-9) (0.23) and C 18:1 trans-10 (0.44) FA increased ( P < 0.001) in L-TMR milk. Milk vaccenic acid ( trans-11 C 18:1, VA) increased from 1.08 in C-TMR to 2.56 g/100g of FA in L-TMR ( P < 0.001). Milk CLA content ( cis-9, trans-11 C 18:2) increased (127%) from 0.62 in C-TMR to 1.41 g/100g FA in L-TMR milk. Content of α-linolenic acid resulted 20% higher ( P < 0.001) in L-TMR milk (0.35 g/100g FA) compared to C-TMR (0.30 g/100g FA). Milk DHA increased from 0 in C-TMR to 0.14 g/100g FA in L-TMR. The omega-6/-3 ratio in C-TMR milk (9.61) was reduced ( P < 0.001) to 6.78 in L-TMR milk. Milk oleic acid ( cis-9 C 18:1) resulted higher ( P < 0.001) in L-TMR (23.65) than in C-TMR (19.75 g/100g FA). The nutritional value of milk fat from confined cows was naturally improved by feeding polyunsaturated FA in the ration, obtaining a reduction of saturated FA and increased levels of healthy FA (CLA, DHA and α-linolenic).
Bovine milk fat represents up to 75% of total fat consumption from ruminant animals and dairy products provide about 15% - 25% of the total saturated fat (SF) in the human diet [
Feeding PUFA rich supplements to dairy cows is an effective tool to inhibit de novo mammary synthesis of SF and reduce the potentially atherogenic FA of milk [
A current special interest exists on RA because it plays an important role regulating levels of plasma lipids and cardiovascular functions, reducing cancer incidence, as well as blocking tumor growth and metastasis from breasts [
Supplementation with DHA and EPA from fish oil did not affect rumen environment nor fiber digestion [
The work was carried out at the Talar Agroindustrial Complex located in Laguna del Sauce, (Route 12 km 10, Department of Maldonado, Uruguay). Two lots of 80 multiparous Holstein cows (80 - 100 days in lactation) were used. During a pre-experimental period of 14 days all cows received the control ration (C-TMR) composed on a DM basis by ryegrass silage (18.26%), sorghum silage (23.24%), concentrate (56.43%) and cheese whey (2.07%). Concentrate included corn grain (51.95%), soybean meal (31.17%), dry distillers grains (12.99%) and a commercial premix (3.90%). The C-TMR averaged 44.27% DM with 15.94% crude protein (CP), 38.20% neutral detergent fiber (NDF), 20.36% acid detergent fiber (ADF), 5.56% fat, 5.30% ash, 28.6% non-structural carbohydrates with an estimated net energy of lactation content of 1.81 Mcal/kg DM. TMR in take in the pre-experimental period averaged 24 kg DM/cow∙day. After the pre-experimental period cows were fed treatment diets for an extra period of 6 weeks. Cows in the control group (80) continued with the C-TMR while cows in the lipid supplemented group (80) were fed the same TMR in which supplementary soybean oil (0.72 kg/cow∙day) and DHA-micro algae (0.144 kg/cow∙day) were added. Microalgae (Schizochytrium limacinum, about 14% DHA, All-G Rich, All Tech Inc.) were grown heterotrophically in a unique process on a fresh water, low sodium media and fed at 6 g/kg DM intake as suggested in [
Within each lot of 80 animals, two groups of 12 cows/treatment were selected for experimental measurements. Milk production was recorded individually during the whole trial and milk samples were collected from each cow during the last 3 days of the study for milk chemical and FA composition. Samples were obtained from the morning (50 ml) and the afternoon (50 ml) milkings. Of the total (100 ml) milk collected, 20 ml were immediately analyzed for fat, protein, lactose, total solids and non-fat solids by mid-infrared spectrophotometry (Milko Scan, Foss Electric, Hillerod, Denmark) and the remaining 80 ml were frozen (−20˚C) until analysis for milk FA composition. Milk fat was extracted following the method described in [
At the end of the experimental period, additional milk was obtained from the storage tanks of control and supplemented groups to make two cheeses and analyze its FA profile.
Milk production was analyzed using a model with repeated observations over time adjusted for covariate with cow (C = 12), treatment (T = 2), week (W = 6) and T*W interaction. The difference in the milk quality parameters and milk FA profile was analyzed using the Student t test for independent observations.
At the start of the experiment, milk yield averaged 35.9 kg/cow∙day in C-TMR and 36.4 kg/cow∙day in L-TMR (P < 0.88). The treatment x week interaction (P < 0.018) showed that from week 3 onwards, cows fed the L-TMR produced more milk (P < 0.001) than cows fed the C-TMR (
Feeding soybean oil at 2.9% (±1.2) of DM intake did not affect milk production in the experiments reviewed by [
Before lipid supplementation, milk fat content averaged 3.71 and 3.53 g/100g in C-TMR and L-TMR treatments respectively (P = 0.48). Addition of soybean oil and DHA-micro algae to the TMR strongly reduced (P < 0.002) milk fat concentration to an average of 3.36 g/100g in C-TMR and 2.40 g/100g in L-TMR milk. Milk fat content resulted very low in L-TMR treatment if compared to the average pre-trial record of 3.53 g/100g. The inhibition of the de novo mammary synthesis of FA with the corresponding reduction in the total concentration of SFA in milk (
Supplementing PUFA to dairy cows in pasture based diets tends to reduce milk fat content by 8% [
Fatty Acid g/100g FA | C-TMR | L-TMR | P<(1) | ∆%(2) |
---|---|---|---|---|
C4:0 | 2.10 (±0.22) | 1.86 (±0.30) | 0.068 | 11.4 |
C6:0 | 1.89 (±0.18) | 1.32 (±0.26) | 0.000 | −30.2 |
C8:0 | 1.36 (±0.12) | 0.83 (±0.18) | 0.000 | −38.9 |
C10:0 | 3.37 (±0.36) | 1.87 (±0.40) | 0.000 | −44.5 |
C12:0 | 3.91 (±0.26) | 2.29 (±0.41) | 0.001 | −41.4 |
C14:0 | 11.89 (±0.54) | 8.61 (±1.0) | 0.001 | −27.6 |
C16:0 | 29.39 (±2.60) | 23.84 (±1.22) | 0.001 | −18.9 |
∑C12:0-C16:0 | 45.19 (±2.69) | 34.74 (±2.34) | 0.001 | −23.1 |
C18:0 | 9.75 (±1.33) | 11.42 (±1.89) | 0.043 | +17.1 |
C18:1 trans-9 (elaidic acid) | 0.23 (±0.02) | 0.54 (±0.06) | 0.001 | +135 |
C18:1 trans-10 | 0.44 (±0.05) | 3.14 (±1.86) | 0.001 | +614 |
C18:1 trans-11 (vaccenic acid) | 1.08 (±0.14) | 2.56 (±0.71) | 0.001 | +137 |
C18:1 cis-9 (oleica cid) | 19.75 (±2.05) | 23.65 (±1.54) | 0.001 | +19.7 |
C18:2 cis-9 cis-12 (linoleic acid) | 3.01 (±0.34) | 3.50 (±0.38) | 0.01 | +16.3 |
C18:2 cis-9. trans-11 (rumenic acid) | 0.62 (±0.09) | 1.41 (±0.22) | 0.001 | +127 |
C18:3 cis-9 cis-12 cis-15 (linolenic acid) | 0.30 (±0.04) | 0.36 (±0.03) | 0.004 | +20 |
C20.5 n-3 (EPA) | 0.017 (±0.002) | 0.017 (±0.002) | 0.57 | − |
C22.6 n-3 (DHA) | --- | 0.14 (±0.03) | 0.000 | |
CLA/(CLA+AV) | 0.36 (±0.03) | 0.36 (±0.06) | 0.937 | |
SFA | 66.76 (±2.24) | 54.92 (±3.30) | 0.001 | −17.7 |
MUFA | 26.60 (±2.02) | 36.44 (±2.82) | 0.001 | +37 |
PUFA | 4.45 (±0.48) | 6.05 (±0.53) | 0.001 | +36 |
Atherogenic index | 2.69 (±0.30) | 1.50 (±0.20) | 0.001 | −44.2 |
n-6/n-3 | 9.61 (±0.50) | 6.78 (±0.66) | 0.001 | +29.4 |
(1)Student t Test for independent observations. (2)Relative FA changes (%) compared to values observed in milk from C-TMR cows.
note that the reduction in milk fat occurred at the expense of the hypercholesterolemic milk fraction contributing to decrease its atherogenic index (
A direct effect on fat synthesis in the mammary gland by supplemental PUFA or trans-fatty acids formed during the ruminal biohydrogenation and ulterior transfer to the udder is the more likely explanation. Indeed, uptake of some specific preformed FA like trans-10, cis-12 CLA and trans-8, cis-10 CLA reduce the activity and/or expression of genes that encode important enzymes involved in uptake, synthesis and desaturation of fatty acids in the mammary gland [
The presence of DHA (inhibitor of de novo mammary lipogenesis) in the micro algae plus the generation of certain FA such as trans-10 C18:1 and its subsequent transfer to milk (
Milk protein content was not affected (P = 0.43) by supplementary PUFA averaging 3.20 g/100g in C-TMR and 3.07 g/100g in L-TMR. The absence of negative effects on milk protein concentration is an important result since this parameter not only affects the price of milk but also determines the speed and quality of coagulation in the cheese making industry. Synthesis of milk protein can be limited by energy availability and the reduced milk fat content observed could improve the energy status of the cows. In pasture based diets, lipid supplementation does not usually affect milk protein concentration [
Lactose (C-TMR = 4.86 and L-TMR = 4.69 g/100g) and milk urea nitrogen (C-TMR = 21.18 and L-TMR = 17.33 g/100g) tended (P < 0.056) to decrease in PUFA supplemented cows as well as yield of 4% fat corrected milk (C-TMR = 30.89 and L-TMR = 29.49 kg/cow∙day; P = 0.098). Supplementation with unsaturated lipids generally has neutral effects on the production of 4% fat corrected milk both in confined [
Changes in milk FA composition induced by the addition of soybean oil and micro algae to the TMR are presented in
Except in the case of butyric acid which is synthesized by an independent malonyl-CoA pathway, milk concentration of de novo FA (C4:0-C15:1) decreased after adding PUFA supplements to the TMR. This result may be explained at secretory cell level due to the inhibition of activity of lipogenic enzymes such as acetyl-Coa carboxylase [
Adding soybean oil combined with DHA micro-algae to the ration decreased total SFA from 66.76 g/100g in C-TMR to 54.92 g/100g in L-TMR cows. This SFA reduction (17.7%) was coupled to a concomitant increase (36%) in total PUFA (P < 0.001) from a basal value of 4.45 g/100g in C-TMR milk to 6.05 in L-TMR milk. It has been shown that a high intake of SFA is associated with raised blood cholesterol levels which in turn can lead to an increased risk of developing heart disease. There is evidence that substituting SFA with PUFA’s reduces the risk of coronary heart disease [
Compared to milk from C-TMR group, level of total atherogenic FA (C12:0 to C16:0) was reduced (23.1%) in L-TMR promoting a healthier milk. Concentration of myristic acid (C14:0) in C-TMR (11.89 g/100g FA) whose atherogenic role is considered to be very potent [
Another important fact, was the reduction (−44.2%, P < 0.001) in the atherogenic index (AI) of milk from a basal value of 2.69 in C-TMR to 1.50 in the L-TMR as previously observed (1.88 to 0.80) when cows were supplemented with sunflower and fish oils [
Concentration of VA in L-TMR milk averaged 2.56 g/100g FA which represented an increase of 137% over the basal value of 1.08 g/100g observed in C-TMR milk (
In previous work on pasture-based diets, VA represented 73.3% of the total trans-C18: 1 and remained constant after the supply of a soybean-fish oil based supplement representing 73.2% of total trans-C18:1 in cows that received increasing amounts of the supplement [
Concentration of RA increased from a basal value of 0.62 g/100g FA in C-TMR to 1.41 g/100g FA in L-TMR milk (+127%). The RA levels observed in the L-TMR milk were higher than the 1.02 (±0.36) g/100g FA reported in the meta analysis of [
Considering the different sources that may influence on microbial ruminal biohydrogenation activity (intake and interactions of precursors with basal diet, forage:concentrate ratio), an average RA:VA ratio of 0.41 has been proposed as the most frequently observed [
The concentration of linoleic acid (cis-9 cis-12 C18:2) was increased from a basal value of 3.01 in C- to 3.50 g/100g in L-TMR treatment (
In C-TMR milk, the concentration of cis-9, cis-12, cis-15 C18:3 or α-linolenic acid (0.30 g/100g) was within the range (0.28 - 0.33 g/100g) obtained in a previous trial [
In humans, epidemiological and experimental studies have shown that the omega-3 FA have shown hypocholesterolemic, antithrombotic, anti-inflammatory and immune suppressive properties [
Fatty acid, g/100g of total FA | C-TMR cheese | L-TMR cheese | ∆ %(1) |
---|---|---|---|
C4:0 | 2.09 (±0.09) | 1.83 (±0.02) | −12.44 |
C6:0 | 1.81 (±0.07) | 1.29 (±0.01) | −28.73 |
C8:0 | 1.25 (±0.02) | 0.83 (±0.00) | −33.60 |
C10:0 | 2.92 (±0.01) | 1.85 (±0.03) | −36.64 |
C12:0 | 3.36 (±0.04) | 2.28 (±0.04) | −32.14 |
C14:0 | 11.20 (±0.07) | 8.94 (±0.03) | −20.18 |
C16:0 | 29.33 (±0.09) | 25.01 (±0.09) | −14.73 |
C18:0 | 11.09 (±0.03) | 11.74 (±0.01) | +5.86 |
trans-9 C18:1 | 0.22 (±0.01) | 0.59 (±0.01) | +168.18 |
trans-10 C18:1 | 0.33 (±0.04) | 2.55 (±0.30) | +672.73 |
trans-11 C18:1 | 1.28 (±0.04) | 2.82 (±0.16) | +120.31 |
cis-9 C18:1 | 21.43 (±0.08) | 22.92 (±0.04) | +6.95 |
cis-9,-12 C18:2:n-6 | 2.52 (±0.03) | 3.04 (±0.02) | +20.63 |
cis-9, trans-11 C18:2 (RA) | 0.69 (±0.01) | 1.39 (±0.04) | +101.45 |
cis-9,-12,-15 C18:3 (α-linolenic) | 0.28 (±0.02) | 0.33 (±0.04) | +17.86 |
C22:6:n-3 (DHA) | 0.00 | 0.09 (±0.00) | |
SFA | 66.16 (±0.14) | 56.96 (±0.42) | −13.91 |
MUFA | 28.25 (±0.42) | 35.30 (±0.07) | +5.86 |
PUFAFA | 3.93 (±0.19) | 5.47 (±0.04) | +168.18 |
Total omega-6 | 2.69 (±0.33) | 3.17 (±0.03) | +672.73 |
Total omega-3 | 0.33 (±0.03) | 0.46 (±0.03) | +120.31 |
Omega 6/3 ratio | 8.08 (±0.72) | 6.92 (±0.45) | −14.36 |
Atherogenic Index | 2.48 (±0.05) | 1.42 (±0.01) | −42.74 |
(1)Relative FA changes (%) compared to values observed in milk from C-TMR cows. (−) = decrease, (+) = increase.
through alternative foods to fish like dairy products has been considered of interest in several countries (United States, Korea, Canada, Thailand, Australia, China and Singapore).
In Western diets, increased consumption of omega-6 and decreased levels of omega-3 has left dietary omega ratios drastically out of balance (15-20:1) instead of an optimal 1-4:1 [
Finally, it is worth nothing that the presence of oleic acid (cis-9 C18:1) was higher (P < 0.001) in the L-TMR milk (+19.7%) than in the control milk (
The FA composition of cheese made with the milk collected from cows fed the L-TMR diet showed differences compared to the cheese made with the C-TMR (standard) milk (
Taken together, the results indicated a positive effect of lipid supplementation on milk production and milk healthy value in dairy cows fed in a confined feeding system. There is an opportunity to increase the nutritional value of milk in a rapid and natural way by dietary factors including polyunsaturated fatty acids in a confined total mixed ration system in the form of soybean oil and microalgae. This practice resulted in an effective tool to reduce saturated fat content and increase levels of healthy fatty acids like rumenic, docosahexaenoic and α-linolenic. Given the promising health benefits of these fatty acids and the importance of health and nutrition related to fat quality, the opportunity to provide milk and dairy products with increased levels of PUFA and DHA should be explored further as a way of prevention of the onset of many chronic diseases. The induced changes observed in milk fatty acid composition were recovered in cheese elaborated with it.
This work was partially supported by the National Agency of Research and Innovation (ANII), Uruguay Republic (Project Milk Talar CLA, Res. No. 2484-017) and by the National Institute of Agricultural Technology (INTA, Argentina). We thank the staff of Tambo Talar for the collaboration in animal care and management and to AllTech Inc. for supplying the microalgae.
The authors declare no conflicts of interest regarding the publication of this paper.
Gagliostro, G.A., Antonacci, L.E., Pérez, C.D., Rossetti, L. and Carabajal, A. (2018) Improving the Quality of Milk Fatty Acid in Dairy Cows Supplemented with Soybean Oil and DHA-Micro Algae in a Confined Production System. Agricultural Sciences, 9, 1115-1130. https://doi.org/10.4236/as.2018.99078