Thirty-six grazing dairy cows were used to determine the effect of combinations of soybean (SO), and linseed (LO) oils on milk production, composition and milk fatty acid (FA) profile. Treatments were a basal control diet (56% pasture, 44% concentrate) or the control diet supplemented with oils at 4% of estimated total dry matter (DM) intake. Oils were manually mixed to the concentrate in pure forms (SO100 or LO100) or in blends (%w/w) at SO75 - LO25, SO50 - LO50 and SO25 - LO75. Concentrate and oils were thoroughly consumed. Pasture intake (kg DM/cow·day) was 9.27 in control and decreased ( p < 0.05) in SO25 - LO75 (8.09) and LO100 (8.98). Total DM intake (kg/cow·day) in control (16.47) increased (p < 0.05) to 17.04 in SO100 and 17.20 in SO75. Yield of fat corrected milk (4% FCM) averaged 20.73 kg in control resulting higher in SO75 (23.73 kg). Milk fat content (g/100g) in control averaged 3.40 and decreased to 2.79 in SO50-LO50 and to 3.06 in SO25 - LO75 treatments. Milk protein content was not affected and milk protein yield increased in SO100 (11%) and SO75 - LO25 (21%) over Control (0.729 kg/cow·day). Milk basal (Control) content (g/100g FA) of C12:0 (2.58), C14:0 (10.21) and C16:0 (25.69) was reduced (p < 0.05) to 1.64, 6.82 and 19.70 respectively in oil supplemented cows. Basal content of C12:0 to C16:0 averaged 38.48 g/100g FA and decreased (27.4%) after oil intake. Basal trans-10 C18:1 (0.46 g/100g FA) increased ( p < 0.01) in SO100 (1.48) and SO50-LO50 (1.80). Basal level (g/100g FA) of vaccenic acid (trans-11 C18:1, VA) averaged 3.49 and increased (135%) after oil intake with maximum values observed in LO100 (8.17) and SO50 - LO50 (9.20). Rumenic acid (cis-9, trans-11 C18:2, RA) level (g/100g FA) in milk from Control cows (1.56) increased ( p < 0.05) to 3.03 (SO100), 3.21 (SO75 - LO25), 3.24 (SO50 - LO50), 2.33 (SO25 - LO75) and 2.96 (LO100). Results obtained confirmed a great milk fat plasticity in response to PUFA feeding in grazing dairy cows which constitutes a very effective and easy tool in order to improve the healthy value of milk with a potential benefit to the consumer’s health. A net or conclusive response pattern over parameters that improve the healthy value of milk to soybean and linseed oils and their blends was not clearly detected. Taken together, the results suggest some advantage for the SO75:LO25 blend considering the relative costs of both oils, the positive effects on milk, fat and protein yields, the lower hypercholesterolemic FA content of milk and the increase in VA and RA content while maintaining a healthy n - 6/n - 3 ratio and very low levels of the detrimental trans-9 C18:1 and trans-10 C18:1 FA.
Dairy products provide about 25% - 30% of total saturated fat in the human diet and some saturated FA like lauric (C12:0), myristic (C14:0) and palmitic (C16:0) may have a potential negative effect on human health if consumed in excess [
Studies in vitro suggested that the partial replacement of linoleic by linolenic acid in the diet increased the rate of conversion of linoleic to RA and from RA to VA in ruminal fluid. The higher rate of isomerization was obtained when linoleic was combined with linolenic acid [
The experiment was carried out at the National Institute of Agricultural Technology (INTA) in Balcarce (37˚45'S, 58˚18'W) during September and October of 2013. Total duration of the experiment was 38 days. Procedures and animal cares were approved by the Institutional Committee for the Care and Use of Experimental Animals (CICUAE, INTA CERBAS). Thirty-six multiparous Holstein cows (548 ± 56 Kg LW) in early lactation (77 ± 43 days postpartum) were grouped based on parity and milk production measured during the first 7 days of the experiment and randomly assigned to 1 of 6 treatments (6 cows/treat- ments) in a complete randomized design. The basal (Control) diet was composed (DM) by pasture (56%) and concentrate (44%) without supplementary oils. From day 8th of the trial, six cows remained in the Control diet while the cows in oil treatments were supplemented with SO (Glycine max), LO (Linum usitatitissimum), or their blends (%w/w) at 75 - 25 (SO75 - LO25), 50 - 50 (SO50 - LO50) and 25 - 75 (SO25 - LO75). The dose of supplemented materials was calculated to provide 4.0% of the total DM intake of cows [
Milk production was daily recorded over the whole experiment. Milk samples (50 ml) were collected at a.m. and p.m. milkings twice a week on non-consecu- tive days, composited according to the corresponding volume measured at each milking time and analyzed for fat, total protein, lactose, total and not-fat solids by mid-infrared spectrophotometry (Milko Scan-Minor, Foss Electric, Hillerod, Denmark). Milk urea nitrogen (MUN) was determined using a commercial enzymatic kit (Wiener Lab., Rosario, Argentina). During the last 2 weeks of oil supplementation and from each composite sample collected to determine the chemical composition of milk, aliquots of 50 ml were frozen (−24˚C) to obtain a single pool sample per cow for the determination of milk FA composition by gas liquid chromatography (GLC) as described in [
The quality of the concentrate and herbage was estimated from samples taken weekly. Each sample was dried in a forced-air oven (60˚C, 48 hs), ground through a 1-mm screen (Willey mill, Philadelphia, PA) and analyzed for organic matter (OM), neutral detergent fiber (NDF) [
Milk production and composition were evaluated by the PROC MIXED procedure of SAS/STAT® program [
Y i j k = μ + T i + A ( i ) j + W j + C o v + ( T i ∗ W j ) + E ( i j k )
where: Yijk = the dependent variable, μ: overall mean, Cov = covariate (milk yield and composition over the first 7 days), Ti = treatment effects, A(i)j = random effects of animal within treatments, Wj = effects of week, (Ti * Wj) = interaction effects between of treatment and sampling week, E(ijk) = the residual error associated with the ijk observation. Data from milk FA composition, DM intake and changes in BW gain were analyzed by the PROC GLM procedure of the SAS/STAT® (2002-2010) program using the following model:
Y i j = μ + T i + A ( i ) j + E ( i j )
where: Yij = the dependent variable, μ: overall mean, Ti = treatment effects, A(i)j = random effects of animal within treatments, E(ij) = the residual error associated with the ij observation.
Herbage mass in the pregrazing strips averaged 2253 ± 590 kg DM/ha and herbage allowance was 29 ± 1.1 Kg DM/cow.day. Chemical composition of the concentrate and the forage is shown in
As expected, the linoleic acid content in SO resulted high (53.55%) with a low level of saturated FA (SFA) and 21.55% of oleic (cis-9 C18:1) acid. Linolenic acid content resulted high in linseed oil (41.9%) and pasture (54.21%).
Parameter | Pasture2 | Concentrate |
---|---|---|
Dry matter,% | 21.85 ± 2.70 | 89.6 ± 0.65 |
Organic matter,% DM | 90.01 ± 1.35 | 92.80 ± 0.46 |
Crude protein,% DM | 15.10 ± 3.68 | 17.32 ± 1.02 |
NDF,% DM | 46.23 ± 8.16 | 23.97 ± 2.00 |
FDA,% DM | 26.84 ± 4.42 | 11.51 ± 1.41 |
In vitro DM digestibility,% | 68.62 ± 3.10 | 75.14 ± 1.88 |
Starch,% DM | 2.38 ± 0.66 | 32.59 ± 4.05 |
Ether extract,% DM | 2.62 ± 0.54 | 4.47 ± 0.77 |
Metabolizable energy (Mcal/kg DM) | 2.48 ± 0.11 | 2.71 ± 0.07 |
Water soluble carbohydrates,% DM | 11.90 ± 3.60 | 20.70 ± 2.30 |
1Values are expressed as the mean ± standard deviation. Pasture and concentrate n = 10. 2Consociated pasture containing Bromus unioloides, Festuca arundinacea, Trifolium pratense and Trifolium repens.
Fatty acid | Pasture1 | SO2 | LO3 | Concentrate |
---|---|---|---|---|
g/100g AG | ||||
C14:0 | 0.32 | ND4 | ND | ND |
C16:0 | 17.55 | 10.25 | 7.15 | 15.40 |
cis-9 C16:1 | 1.16 | ND | ND | ND |
C18:0 | 1.50 | 4.90 | 5.45 | 3.43 |
cis-9 C18:1 | 1.87 | 21.55 | 21.05 | 26.95 |
cis-11 C18:1 | ND | ND | ND | 3.20 |
cis-12 C18:1 | ND | ND | ND | 0.81 |
cis-9 cis-12 C18:2 | 12.45 | 53.55 | 23.6 | 45.85 |
C20:0 | 0.69 | 0.40 | 0.25 | 0.33 |
cis-9 cis-12 cis-15 C18:3 | 54.21 | 8.50 | 41.90 | 3.21 |
C22:0 | 0.99 | 0.40 | 0.20 | 0.38 |
1Consociated pasture containing Bromus unioloides, Festuca arundinacea, Trifolium pratense and trifolium repens. 2Soybean oil. 3Linseed oil. 4Not detected.
Compared to Control records (23.03 kg/cow∙day), supplementation with 4% oils increased (p < 0.05) milk yield (25.19 kg/cow∙day). Production of fat corrected milk (FCM) resulted greater for cows in AS75 - AL25 (
No significant differences were observed in BW gain of cows (
Parameter | Treatment1 | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Control | SO100 | SO75 - LO25 | SO50 - LO50 | SO25 - LO75 | LO100 | SEM | T | W | T * W | |
P2 | ||||||||||
Milk yield, kg/d | 23.03c | 24.59bc | 26.12ab | 24.53c | 26.85a | 23.86c | 0.55 | 0.0004 | 0.44 | NS3 |
4%FCM%, kg/d | 20.73b | 22.87ab | 23.73a | 20.45b | 22.90ab | 21.21b | 0.92 | 0.08 | 0.0008 | NS |
Fat, g/100 g | 3.40a | 3.47a | 3.33ab | 2.79c | 3.06bc | 3.40a | 0.12 | 0.002 | <0.0001 | NS |
Protein, g/100 g | 3.34 | 3.29 | 3.34 | 3.25 | 3.16 | 3.29 | 0.09 | NS | <0.0001 | NS |
Lactose, g/100 g | 4.82 | 4.90 | 4.89 | 4.89 | 4.88 | 4.96 | 0.04 | NS | <0.0001 | 0.001 |
Solids, g/100g | 12.29a | 12.37a | 12.41a | 11.80bc | 11.74c | 12.24ab | 0.15 | 0.006 | <0.0001 | NS |
Fat yield, kg/día | 0.748bc | 0.857ab | 0.886a | 0.709c | 0.820abc | 0.791abc | 0.04 | 0.04 | <0.0001 | NS |
Protein yield, kg/día | 0.729d | 0.811abc | 0.882a | 0.806bcd | 0.850ab | 0.773cd | 0.03 | 0.007 | 0.001 | NS |
1Values are expressed as least squares means and standard error of least squares means. Cows were fed a basal diet (Control) without oils or basal diet supplemented with pure oils or blends at 4% of total DM intake as follows: 0.8 kg SO, 0.6 kg SO and 0.2 kg LO (SO75 - LO25), 0.4 kg SO and 0.4 kg LO (SO50 - LO50), 0.2 kg SO and 0.6 kg LO (SO25 - LO75) and 0.8kg LO. 2Treatment effect. 3Not significant effects. 4FCM% = 4% Fat Corrected Milk. T = treatment effect. W = week effect. TxW = treatment for week interaction. a,dMeans in the same row with different superscripts differ significantly for treatment effect with P-value as mentioned in column for significance at p < 0.05 (Test Tukey-Kramer).
Parameter | Treatment1 | SEM | P<2 | |||||
---|---|---|---|---|---|---|---|---|
Kg | Control | SO100 | SO75 - LO25 | SO50 - LO50 | SO25 - LO75 | LO100 | ||
Initial BW | 542.2 | 547.8 | 562.3 | 528.5 | 554.2 | 554.8 | 23.9 | 0.94 |
Final BW | 568.6 | 584.7 | 588.3 | 559.2 | 592.2 | 584.2 | 22.6 | 0.88 |
Daily BW gain | 0.690 | 0.960 | 0.680 | 1.00 | 0.810 | 0.780 | 0.14 | 0.47 |
BW change | 26.5 | 36.8 | 26.0 | 30.8 | 38.7 | 29.7 | 5.55 | 0.45 |
1Values are expressed as least squares means and standard error of least squares means (SEM). Cows were fed a basal diet (Control) without oils or basal diet supplemented with pure oils or blends at 4% of total DM intake as follows: 0.8 kg SO, 0.6 kg SO and 0.2 kg LO (SO75 - LO25), 0.4 kg SO and 0.4 kg LO (SO50 - LO50), 0.2 kg SO and 0.6 kg LO (SO25 - LO75) and 0.8 kg LO. 2Treatment effect.
Pasture DM intake increased by 6% and 8% in SO100 and S75 - LO25 while it was reduced by 0.3%, 13% and 9% in SO50 - LO50, SO25 - LO75 and LO100 respectively (
Milk content of butyric (C4:0) acid was not affected after oil intake (
Parameter | Treatment1 | SEM | P2 | |||||
---|---|---|---|---|---|---|---|---|
Control | SO100 | SO75 - LO25 | SO50 - LO50 | SO25 - LO75 | LO100 | |||
Intake (kg DM/d) | ||||||||
Pasture3 | 9.27ab | 9.84ab | 10.00a | 9.24ab | 8.09c | 8.98bc | 0.35 | 0.007 |
Concentrate | 7.2 | 7.20 | 7.20 | 7.20 | 7.20 | 7.20 | - | - |
Oil | - | 0.80 | 0.80 | 0.80 | 0.80 | 0.80 | - | - |
Total DM | 16.47b | 17.84a | 18a | 17.24ab | 16.09c | 16.98bc | 0.39 | <0.0001 |
Milk/DM intake | 1.40a | 1.38a | 1.45b | 1.42b | 1.67c | 1.41a | 0.11 | 0.0006 |
ME, Mcal/d | 43.11c | 48.65a | 49.05a | 47.17ab | 44.07bc | 46.48abc | 0.91 | <0.0001 |
NEl(Mcal/d) | 27.59c | 31.14a | 31.40a | 30.18a | 28.20bc | 29.75ab | 0.58 | <0.0001 |
1Values are expressed as least squares means and standard error of least squares means (SEM). Cows were fed a basal diet (Control) without oils or basal diet supplemented with pure oils or blends at 4% of total DM intake as follows: 0.8 kg SO, 0.6 kg SO and 0.2 kg LO (SO75 - LO25), 0.4 kg SO and 0.4 kg LO (SO50 - LO50), 0.2 kg SO and 0.6 kg LO (SO25 - LO75) and 0.8 kg LO. 2Treatment effect. 3Consociated pasture containing Bromus unioloides, Festuca arundinacea, Trifolium pratense and trifolium repens. a,dMeans in the same row with different superscripts differ significantly for treatment effect with P-value as mentioned in column for significance at p < 0.05 (Test Tukey-Kramer).
FA | Treatment1 | P2 | ||||||
---|---|---|---|---|---|---|---|---|
g/100 g of FA reported | Control | SO100 | SO75 - LO25 | SO50 - LO50 | SO25 - LO75 | LO100 | SEM | T |
C4:0 | 2.38ª | 2.41ª | 2.47a | 2.18a | 2.60a | 2.46a | 0.15 | <0.0001 |
C6:0 | 1.50ª | 1.25ab | 1.35ab | 1.11b | 1.30ab | 1.34ab | 0.10 | 0.02 |
C8:0 | 0.93ª | 0.66b | 0.74b | 0.60b | 0.72b | 0.74b | 0.06 | 0.0002 |
C10:0 | 2.20ª | 1.39b | 1.55b | 1.27b | 1.54b | 1.55b | 0.13 | <0.0001 |
C12:0 | 2.58ª | 1.60b | 1.79b | 1.52b | 1.73b | 1.73b | 0.12 | <0.0001 |
C14:0 | 10.21ª | 6.78b | 7.27b | 6.42b | 6.75b | 6.95b | 0.32 | <0.0001 |
cis-9 C14:1 | 0.88ª | 0.43b | 0.48b | 0.37b | 0.42b | 0.34b | 0.08 | <0.0001 |
C15:0 | 0.98ª | 0.68b | 0.72b | 0.73b | 0.69b | 0.68b | 0.03 | <0.0001 |
C16:0 | 25.69ª | 19.49b | 20.07b | 19.53b | 19.52b | 18.96b | 0.66 | <0.0001 |
C16:1 | 0.88ª | 0.58bc | 0.62b | 0.40bc | 0.54bc | 0.38c | 0.07 | <0.0001 |
C17:0 | 0.52ª | 0.32b | 0.31b | 0.34b | 0.34b | 0.33b | 0.03 | <0.0001 |
C18:0 | 12.78c | 14.11bc | 13.86bc | 14.10bc | 16.15a | 15.33ab | 0.67 | 0.004 |
C18:1 Isomers | ||||||||
Trans-6 - 8 | 0.16c | 0.38ab | 0.32b | 0.41a | 0.36ab | 0.36ab | 0.03 | <0.0001 |
Trans-9 | 0.23b | 0.53ª | 0.48ª | 0.52a | 0.47a | 0.50a | 0.02 | <0.0001 |
Trans-10 | 0.46c | 1.48ab | 0.95bc | 1.80a | 1.13abc | 0.91bc | 0.29 | 0.006 |
Trans-11 (VA) | 3.49c | 8.17ab | 7.82b | 9.20a | 7.67b | 8.15ab | 0.38 | <0.0001 |
Total trans | 4.34c | 10.56ab | 9.57b | 11.93a | 9.63b | 9.91b | 0.52 | <0.0001 |
cis-9 C18:1 | 26.14b | 27.80ab | 27.50ab | 27.45ab | 27.76ab | 28.10a | 0.68 | 0.02 |
cis-11C18:1 | 2.15ª | 2.10ª | 1.92ab | 1.95ab | 1.92ab | 1.78b | 0.09 | 0.01 |
C18:2 (n − 6) | 1.96b | 3.36ª | 3.50ª | 3.44a | 2.87a | 2.74a | 0.29 | <0.0001 |
C18:3 (n − 3) | 0.35d | 0.40d | 0.64c | 0.73bc | 0.85ab | 1.05a | 0.07 | <0.0001 |
cis-9trans-11 C18:2 (CLA) | 1.56c | 3.03ª | 3.21ª | 3.24a | 2.33b | 2.96a | 0.22 | <0.0001 |
Short chain FA3 | 7.02ª | 5.70b | 6.11ab | 5.16b | 6.17ab | 6.08ab | 0.42 | 0.005 |
Medium chain FA4 | 41.69ª | 29.30b | 31.21b | 29.18b | 29.70b | 29.15b | 0.98 | |
Long chain FA5 | 49.27b | 61.32a | 60.21a | 62.70a | 61.52a | 61.86a | 1.08 | <0.0001 |
Saturated FA (SFA) | 59.76ª | 48.24b | 50.10b | 47.74b | 51.28b | 49.95b | 1.24 | <0.0001 |
Unsaturated FA (UFA) | 38.21b | 48.07a | 47.43a | 49.30a | 46.12a | 47.14a | 1.17 | <0.0001 |
SFA/UFA | 1.58ª | 1.01b | 1.06b | 0.97b | 1.12b | 1.06b | 0.06 | <0.0001 |
AI6 | 1.85ª | 1.05b | 1.12b | 1.00b | 1.09b | 1.07b | 0.07 | <0.0001 |
∆D products | 35.77b | 43.93a | 42.97a | 44.72a | 42.04a | 43.00a | 0.99 | <0.0001 |
Substrates8 | 54.51ª | 51.50b | 51.76b | 52.99ab | 53.01ab | 52.01b | 0.85 | <0.0001 |
Índex7 | 0.40b | 0.46ª | 0.45ª | 0.46a | 0.44a | 0.45a | 0.008 | <0.0001 |
De novo FA (C4:0-C15:1) | 21.07ª | 15.60b | 16.35b | 14.17b | 15.59b | 15.70b | 0.81 | <0.0001 |
Preformed FA (>17:0) | 50.70b | 61.26a | 60.16a | 62.57a | 61.42a | 61.72a | 1.06 | <.0001 |
n − 6/n − 3 FA | 5.94b | 8.53ª | 5.66b | 4.86c | 3.47d | 2.76d | 0.26 | 0.0008 |
CLA/AV | 0.44ª | 0.37abc | 0.42ab | 0.33bc | 0.31c | 0.37bc | 0.03 | <0.0001 |
å(C12:0 - C16:0) | 38.48ª | 27.43b | 29.13b | 27.47b | 28.00b | 27.64b | 0.96 | <0.0001 |
1Values are expressed as least squares means and standard error of least squares means (SEM). Cows were fed a basal diet (Control) without oils or basal diet supplemented with pure oils or blends at 4% of total DM intake as follows: 0.8 kg SO, 0.6 kg SO and 0.2 kg LO (SO75 - LO25), 0.4 kg SO and 0.4 kg LO (SO50 - LO50), 0.2 kg SO and 0.6 kg LO (SO25 - LO75) and 0.8 kg LO. 2Treatment effect. 3Short chain FA (C6:0 to C10:0). 4Medium chain FA: (C12:0 to C17:1). 5Long chain FA: (C18:0 to C22:6). 6Atherogenicity index: (C12 + 4 * C14 + C16)/(åUFA). UFA: cis-9 C14:1, C16:1, cis-9 C18:1, cis-11 C18:1, trans-11 C18:1, C18:3, C18:2, C18:2 cis-9 trans11 CLA. The detrimental FA trans-6-8, 9, 10 C18:1 were excluded. 7Index: ([å∆9Dproducts]/[å∆9D products + Susbstrates]). 8Substrates:C14:0 + C15:0 + C16:0 + C17:0 + C18:0 + Trans11 C18:1. a,dMeans in the same row with different superscripts differ significantly for treatment effect with P-value as mentioned in column for significance at p < 0.05 (Test Tukey-Kramer).
(
In mik from Control cows, VA content represented 80.41% of the total trans- C18:1 remaining high (77% to 82%) after oil intake (
Content of VA in Control milk averaged 3.49 g/100g FA (
rated/saturated/ratio in milk were higher in oil compared to Control (p < 0.05) treatment without differences between oil blends.
Plasma metabolite concentration (glucose, non-esterified fatty acids, triglyceride and urea) were not affected (data not shown). Compared to Control (199.4 mg/dl), circulating levels of plasma cholesterol increased (p < 0.05) in SO50 (229.3 mg/dl), SO25 (231.9 mg/dl) and LO 100 (236.4 mg/dl).
The daily strip-grazing system allowed to provide 29 kg DM/cow.day considered adequate to maximize pasture intake [
SO represented a good source of oleic (21.55%) and essentially linoleic (53.55%) acids as reported in [
In [
The lack of negative effects of oil supply on milk protein content (
The lack of differences in BW gain (
In our trial, the effect of supplemental fat on DM intake showed different responses (
The increase in mammary uptake of circulating FA after oil supply [
The decrease in the total content of de novo synthesized FA (C4:0 to C15:1) was similar between the pure oils and their mixtures (
The reduction (33%) in myristic acid content (
Milk content of stearic acid increased only when LO was present at 75% and 100% of the blend without differences in treatments with a higher proportion of SO (
In the meta-analysis by [
Linoleic acid content in milk from Control cows (2.96 g/100g FA,
The levels of RA achieved in treatments with pure oils (2.96 to 3.03 g/100g FA) were higher than those of 1.60 - 2.39 g/100g FA reported in [
The results confirmed the existence of a broad plasticity in milk FA composition in response to PUFA feeding to grazing dairy cows which constitutes an effective tool to the farmer in order to improve the healthy and added value of milk with a potential benefit to the consumer’s health. A net or well defined response over parameters linked to healthy value of milk was not detected after feeding soybean and linseed oils or blends at 4% of total DM intake. Taken together, the results suggest some advantage for the SO75:LO25 blend considering the relative costs of both oils, the positive effects on milk, fat and protein yields, the lower hypercholesterolemic FA content of milk and the increase in VA and RA content while maintaining a healthy n − 6/n − 3 ratio and very low levels of the detrimental trans-9 C18:1 and trans-10 C18:1 FA.
This work was supported by the National Institute of Agricultural Technology (INTA). This Institute is a decentralized state agency with operational and financial autarchy, under the Ministry of Agroindustry of the Argentine Republic. This publication is part of the requirements to access to the academic degree of Doctor in Agricultural Sciences by the Mar del Plata National University, Argentina.
Antonacci, L.E., Gagliostro, G.A., Cano, A.V. and Bernal, C.A. (2017) Effects of Feeding Combinations of Soybean and Linseed Oils on Productive Performance and Milk Fatty Acid Profile in Grazing Dairy Cows. Agricultural Sciences, 8, 984-1002. https://doi.org/10.4236/as.2017.89072