The objective of the experiment was to determine the effect of feeding three levels (T3.5, T7.0 and T10.5) of energy concentrate (3.5, 7.0 and 10.5 kg cow -1 day -1) on total dry matter (DM) and energy intakes, milk yield and composition, nutritional value of milk and rumen pasture neutral detergent fiber (NDF) digestion in grazing dairy cows. Twenty-one multiparous Holstein cows in early lactation (70.2 ± 13 days postpartum) producing 37.1 (±4.7) kg of milk were assigned to a 3 treatments (7 cows/treatment) × 3 periods Latin square design. Parameters of ruminal environment and pasture NDF degradation were obtained using 3 additional cows of the same breed fitted with rumen cannulae. On a wet basis, concentrate was composed by corn grain (68%), soybean meal (22%), wheat bran (8%) and a vitamin-mineral nucleus with monensin. Pasture ( Medicago sativa, sp) was used in a rotational grazing system with an herbage allowance of 30 kg DM cow -1 d -1. Yield (kg cow -1 d -1) of fat corrected milk (4% FCM) resulted higher ( p < 0.05) in T7.0 (29.0) compared to T3.5 (26.8) but similar to T10.5 (30.2). Milk and protein yields were linearly increased ( p < 0.01) by concentrate intake. Milk fat (3.13 g/100g) and total solid contents (11.79 g/100g) did not differ whereas milk protein ( p < 0.03) and casein ( p < 0.01) levels (g/100g) increased linearly from 3.05 to 3.10 (protein) and from 2.42 to 2.47 (casein). Pasture intake decreased but total DM and energy consumption were enhanced showing addition effects after concentrate feeding. Body weight (BW) loss and plasmatic levels of non esterified fatty acids (NEFA) decreased with concentrate intake. Circulating levels of insulin-like growth factor-I (IGF-I) were higher ( p < 0.05) in T10.5 while those of glucose, plasma urea nitrogen, insulin and somatotrophin were not affected. Ruminal pH and acetate concentration resulted lower ( p < 0.05) in T10.5 when compared to T3.5. The acetate:propionate ratio decreased ( p < 0.01) from 4.25 in T3.5 to 3.08 in T10.5 and ruminal ammonia nitrogen levels tended ( p < 0.07) to be lower as concentrate intake increased. Kinetics parameters of NDF degradation remained unchanged. The potential hypercholesterolemic fatty acids (FA) of milk (C12:0 to C16:0.) remained unchanged as concentrate intake increased. Milk content of linolenic acid decreased and the n-6:n-3 ratio increased with concentrate intake from 1.56 (T3.5) to 2.57 (T10.5) remaining below the recommended values for human health (<4:1). Milk content of antioxidant vitamins was not significantly altered even when pasture DM intake fall in T10.5 compared to T3.5. Increased consumption of a starch-rich concentrate up to 40% of DM intake of cows showed additive effects on total DM and energy intakes improving milk yield, milk protein and casein contents without negative effects on milk fat concentration or yield. Pasture fiber digestion and nutritional parameters linked to healthy value of milk fat were not affected.
Significant variability in commodity prices and perceived animal welfare concerns around permanent housing of livestock have led to increased global interest in grazing production systems for dairy cows [
Energy to protein imbalances in pasture-based diets may in turn be attenuated by increased consumption of starch-rich concentrates [
The experiment was carried out in the experimental farm of INTA Rafaela (31˚12'S, 61˚30'W) during the spring of 2009. Measurements of milk production and composition, BW, body condition score (BCS), DM intake (DMI) and plasma metabolite and hormone concentration were carried out using 21 multiparous (3.3 ± 1.7 lactations) Holstein cows in early lactation (70.2 ± 13 days postpartum). At the start of the trial, cows produced 37.1 (±4.7) kg milk, averaging 593 (±59.9) BW and 2.52 (±0.24) BCS. Cows were grouped by milk production, number of lactations and days postpartum and randomly assigned to 3 treatments (7 cows/treatment) according to a Latin square design with 3 experimental periods of 19 days long (14 days for adaptation and 5 for data collection). Parameters of ruminal environment and digestion were obtained using 3 cows of the same breed fitted with rumen cannulae in a Latin square design with experimental periods of 19 days (17 days for adaptation and 2 of measurements). All cows were fitted with transponders (ALPRO version 6.60/DeLaval, Tumba, Sweden) to individually record daily milk production and concentrate allocation in the milking parlor. Treatments were three levels (T3.5, T7.0 and T10.5) of concentrate intake (3.5, 7.0 and 10.5 kg cow−1 day−1) composed (wet basis) of corn grain (68%), soybean meal (22%), wheat bran (8%) and a vitamin-mineral nucleus with monensin. It was supplied by halves in individual feeders during each milking time (4:30 a.m. and 3:30 p.m.). An alfalfa (Medicago sativa, sp) pasture was used in a rotational grazing system with an herbage allowance of 30 kg DM cow−1 d−1 adjusted using portable electric wiring. During the 3 weeks prior to the start of the trial all cows received 7.0 kg of the experimental concentrate and pasture.
Herbage mass (kg DM ha−1) was weekly measured by cutting samples at 4 cm in height [
Milk production was individually recorded over the last 5 days of each experimental period by a DeLaval ALPRO milk metering system (DeLaval International AB, Tumba, Sweden). Individual milk samples were collected at days 15th and 18th of each period, composited according to the corresponding volume measured at each milking time and analyzed for content of fat, total protein, lactose, total solids (TS), non-fat solids (NFS) and urea by infrared spectrophotometry (MilkoScanTM Minor; FOSS Electric, Hillerod, Denmark) according ISO/IDF standard method [
Concentrate intake was determined throughout the trial by the difference between offered and refused material. Pasture intake was estimated in each experimental period from the individual production of faeces and the in vitro DM digestibility (IVDMD) of the pasture. The total faecal production of each cow was determined using an indigestible marker (LIPE®) according to [
Cows were weighed after the morning milking at the beginning and end of each experimental period avoiding previous access to water. Concurrently, BCS was determined as the average records of two independent observers using a 5-point scale (1 = excessively thin to 5 = excessively fat) with increments of 0.25 units [
The rate and extent of pasture NDF degradation was estimated using the in situ technique [
Kinetics parameters of NDF degradation were estimated with the equation proposed by [
During the first six sampling hours, 200 mL of ruminal liquor (ventral sac) were drawn from each cannulated cow for measurements of pH, ammonia nitrogen (NH3-N) and volatile fatty acid (VFA). Immediately after extraction and previous filtration of the ruminal liquor with cheese-like cloth, pH was measured with a portable digital pH-meter (ORION model 250 A). A sample (100 mL) was acidified with 1 mL of 1 N H2SO4 and stored at −20˚C until the NH3-N and VFA determinations. The NH3-N concentration was determined by titration with steam entrainment, prior to alkalization of the samples with sodium hydroxide. For VFA determination, the samples were purified with orthophosphoric acid (25%) on sulfuric acid 0.5 M at 0.5 mL for each 2 mL of sample and then centrifuged per 10 min with 5000 g [
Milk production and composition, changes in BW and BCS, DM intake, plasma metabolite and hormone concentration and kinetics parameters of NDF degradation were analyzed in a 3 × 3 Latin-square design with the MIXED procedure of SAS [
The average value of herbage mass in the pregrazing strips was 1996 (±260) kg DM ha−1 and the average herbage allowance obtained was 31.4 (±1.9) kg DM cow−1 per day during the trial. Values for the chemical composition of the feedstuffs used in this trial are shown in
Pasture DM content was above the critical range (15% - 18%) that would
Parameters | Pasture2 | Concentrate |
---|---|---|
DM (%) | 22.5 ± 2.0 | 90.8 ± 1.0 |
g/100g DM | ||
OM | 90.2 ± 0.8 | 93.9 ± 0.8 |
IVDMD | 75.2 ± 2.8 | 86.1 ± 3.5 |
CP | 25.1 ± 3.3 | 18.3 ± 2.0 |
NDF | 34.8 ± 3.9 | 18.0 ± 2.0 |
ADF | 19.9 ± 1.6 | 6.6 ± 1.2 |
LDA | 4.6 ± 1.1 | 1.2 ± 0.4 |
EE | 2.9 ± 0.3 | 6.0 ± 0.6 |
Starch | nd | 42.5 ± 4.4 |
1Values are expressed through the mean ± standard deviation. 2Perennial pastures of alfalfa (Medicago sativa). DM = dry matter; OM = organic matter; IVDMD = in vitro DM digestibility; CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; ADL = acid detergent lignin; EE = ether extract; nd = not determined.
affect voluntary DM intake [
ECM and 4% FCM yields were significantly higher in T7.0 compared to T3.5 but similar to those obtained in T10.5 while milk and protein yields increased (+13.6% and +14.9%, respectively) with level of supplementation (
Parameter | Treatment1 | SEM | P<2 | ||||
---|---|---|---|---|---|---|---|
T3.5 | T7.0 | T10.5 | Treat2 | Lineal3 | Quadratic3 | ||
Milk, kg d−1 | 30.8c | 33.3b | 35.0a | 1.2 | 0.01 | 0.01 | 0.35 |
4% FCM, kg d−1 | 26.8b | 29.0a | 30.2a | 1.1 | 0.01 | 0.01 | 0.40 |
ECM, kg d−1 | 26.7b | 29.0a | 30.2a | 1.0 | 0.01 | 0.01 | 0.37 |
Fat, kg cow−1 d−1 | 0.97b | 1.05ab | 1.08a | 0.04 | 0.02 | 0.01 | 0.51 |
Fat, % | 3.15 | 3.16 | 3.09 | 0.08 | 0.79 | 0.63 | 0.64 |
Protein, kg cow−1 d−1 | 0.94c | 1.02b | 1.08a | 0.03 | 0.01 | 0.01 | 0.35 |
Protein, % | 3.05 | 3.08 | 3.10 | 0.04 | 0.08 | 0.03 | 0.60 |
Lactose, % | 4.85b | 4.91a | 4.94a | 0.03 | 0.01 | 0.01 | 0.43 |
TS, % | 11.73 | 11.84 | 11.82 | 0.11 | 0.57 | 0.42 | 0.50 |
NFS, % | 8.58b | 8.69a | 8.74a | 0.06 | 0.01 | 0.01 | 0.34 |
Urea, % | 0.046a | 0.045a | 0.043b | 0.001 | 0.01 | 0.01 | 0.53 |
Casein, % | 2.42b | 2.44b | 2.47a | 0.01 | 0.01 | 0.01 | 0.62 |
1Values are expressed as least square means (LSMeans) and standard error of LSMeans (SEM). 2Effect of treatment (Treat). 3Contrast. a,b,cWithin rows LSMeans with different letters differs (Tukey-Kramer test, P < 0.05). 4% FCM = milk fat corrected 4%; ECM = milk corrected energy; TS = total solids; NFS = non-fat solids.
fat yield in T10.5 resulted higher compared to T3.5 and similar to T7.0 without significant differences between T3.5 and T7.0.
Milk fat and TS contents were similar between treatments, whereas protein content tended (p < 0.08) to be higher in T10.5. As concentrate intake increased, a lower milk urea level together with higher lactose and casein contents were observed (
Concentrate was thoroughly consumed by cows without refusals for any treatment. Pasture DM intake decreased (−20.7%), while total DM and net energy for lactation (NEl) increased (+12.6% and +20.7%, respectively) with concentrate intake. On the other hand, conversion efficiency remained constant (
These results suggest that the increase in milk production obtained with increasing levels of concentrate intake would be linked to a higher DM and energy intake. Substitution rate (kg DM pasture kg DM concentrate−1) was similar between treatments with an average value of 0.58.
Parameter | Treatment1 | SEM | P<2 | |||
---|---|---|---|---|---|---|
T3.5 | T7.0 | T10.5 | Treat | Period | ||
Pasture intake | ||||||
DM, kg d−1 | 17.96a | 16.07b | 14.24c | 0.18 | 0.01 | 0.01 |
NE 1 3 , Mcal d−1 | 26.76a | 23.95b | 21.22c | 0.27 | 0.01 | 0.01 |
Total intake | ||||||
DM, kg d−1 | 21.15c | 22.45b | 23.81a | 0.18 | 0.01 | 0.01 |
NE 1 3 , Mcal d−1 | 32.95c | 36.33b | 39.78a | 0.27 | 0.01 | 0.01 |
GE4, Mcal ENL d−1 | 5.69c | 7.91b | 9.93a | 0.05 | 0.01 | 0.01 |
Conversion efficiency | ||||||
Milk, kg DM−1 | 1.48 | 1.52 | 1.52 | 0.06 | 0.36 | 0.04 |
Milk, Mcal ENL−1 | 0.95 | 0.94 | 0.91 | 0.04 | 0.13 | 0.04 |
ECM kg MS−1 | 1.27 | 1.33 | 1.29 | 0.06 | 0.25 | 0.02 |
ECM Mcal ENL−1 | 0.81 | 0.82 | 0.77 | 0.03 | 0.08 | 0.03 |
1Values are expressed as least square means (LSMeans) and standard error of LSMeans (SEM). 2Effects of treatment (Treat) and period. 3Calculated using [
BW loss (
Increased concentrate intake significantly enhanced plasma IGF-I concentration, a result consistent with the observed higher milk production (
Parameter | Treatment1 | SEM | P<2 | |||
---|---|---|---|---|---|---|
T3.5 | T7.0 | T10.5 | Treat | Period | ||
BW, kg | ||||||
Initial | 587.1a | 580.8b | 581.5b | 12.2 | 0.05 | 0.01 |
Final | 580.5 | 580.7 | 585.4 | 12.8 | 0.08 | 0.01 |
Change | −6.6b | −0.1ab | 3.8a | 2.5 | 0.02 | 0.01 |
BCS, 1 to 5 | ||||||
Initial | 2.50 | 2.46 | 2.43 | 0.06 | 0.18 | 0.02 |
Final | 2.45 | 2.43 | 2.49 | 0.06 | 0.44 | 0.21 |
Change | −0.05 | −0.03 | 0.06 | 0.04 | 0.13 | 0.02 |
1Values are expressed as least square means (LSMeans) and standard error of LSMeans (SEM). 2Effects of treatment (Treat) and period. a,bWithin rows LSMeans with different superscripts differ (Tukey-Kramer test, P < 0.05).
Parameter | Treatment1 | SEM | P<2 | |||
---|---|---|---|---|---|---|
T3.5 | T7.0 | T10.5 | Treat | Period | ||
Glucose, mmol l−1 | 3.53 | 3.41 | 3.46 | 0.05 | 0.10 | 0.01 |
Urea, mmol l−1 | 7.47 | 7.42 | 7.21 | 0.21 | 0.37 | 0.01 |
NEFA, μEq l−1 | 265.7a | 240.5ab | 227.6b | 12.4 | 0.02 | 0.01 |
GH, ng ml−1 | 3.89 | 3.97 | 3.75 | 0.36 | 0.90 | 0.56 |
Insulin, ng ml−1 | 0.65 | 0.68 | 0.75 | 0.07 | 0.32 | 0.01 |
IGF-I, ng ml−1 | 113.1b | 128.9ab | 149.0a | 8.45 | 0.02 | 0.13 |
GH/Insulin ratio | 8.96 | 7.47 | 6.11 | 1.54 | 0.28 | 0.04 |
1Values are expressed as least square means (LSMeans) and standard error of LSMeans (SEM). 2Effects of treatment (Treat) and period. a,bWithin rows LSMeans with different superscripts differ (Tukey-Kramer test, P < 0.05). NEFA = non esterified fatty acids; GH = somatotrophin; IGF-I = somatomedin C.
The treatment × hour interaction was not significant for any variable of ruminal
environment (
Kinetics parameters of NDF degradation were not affected except for the lag time that resulted lower (p < 0.05) in T7.0 and T10.5 with respect to T3.5 (
In spite of the lower pH records observed as concentrate intake increased, effective pasture NDF degradability was unaffected.
Parameter | Treatment1 | SEM | P<2 | ||||
---|---|---|---|---|---|---|---|
T3.5 | T7.0 | T10.5 | Treat | Hour | Treat * Hour | ||
VFA | |||||||
Total, mmol L−1 | 75.3 | 67.5 | 66.3 | 3.17 | 0.29 | 0.01 | 0.96 |
Acetate, mmol L−1 | 55.6a | 48.1ab | 45.7b | 2.20 | 0.01 | 0.02 | 0.94 |
Acetate, mol 100 mol−1 | 73.9a | 71.5b | 69.0c | 0.34 | 0.01 | 0.04 | 0.36 |
Propionate, mmol L−1 | 13.1 | 13.7 | 15.0 | 0.68 | 0.09 | 0.01 | 0.99 |
Propionate, mol 100 mol−1 | 17.4c | 20.2b | 22.5a | 0.25 | 0.01 | 0.10 | 0.63 |
Butyrate, mmol L−1 | 6.6 | 5.7 | 5.6 | 0.47 | 0.39 | 0.01 | 0.79 |
Butyrate, mol 100 mol−1 | 8.7 | 8.3 | 8.4 | 0.20 | 0.46 | 0.05 | 0.13 |
Acetate:Propionate ratio | 4.25a | 3.55b | 3.08c | 0.06 | 0.01 | 0.05 | 0.60 |
pH | 6.20a | 6.02ab | 5.94b | 0.07 | 0.04 | 0.16 | 0.89 |
NH3-N, mg % | 41.62 | 35.87 | 35.04 | 2.14 | 0.07 | 0.01 | 0.93 |
1Values are expressed as least square means (LSMeans) and standard error of LSMeans (SEM). 2Effects of treatment (Treat), hour and treat*hour interaction. a,b,cWithin rows LSMeans with different superscripts differ (Tukey-Kramer test, P < 0.05). VFA = volatile fatty acids.
Parameter | Treatment1 | SEM | P<2 | |||
---|---|---|---|---|---|---|
T3.5 | T7.0 | T10.5 | Treat | Period | ||
Digestible fraction, % | 66.38 | 57.83 | 55.96 | 3.44 | 0.28 | 0.26 |
Rate of digestion, % hour−1 | 6.94 | 8.09 | 9.33 | 1.90 | 0.72 | 0.51 |
Lag time, hours | 3.64c | 2.40a | 3.07b | 0.45 | 0.01 | 0.01 |
Effective degradability | ||||||
Kp3 = 5% hour−1 | 30.63 | 30.98 | 30.11 | 1.89 | 0.94 | 0.09 |
1Values are expressed as least square means (LSMeans) and standard error of LSMeans (SEM). 2Treatment (Treat) and period effects. 3Rate of passage (kp) assumed according to [
Milk fat levels of C10:0 (caproic), C12:0 (lauric) and C18:2n6 (linoleic) resulted higher in T10.5 without differences between T3.5 and T7.0, whereas that of C18:3n3 (linolenic) decreased and the n−6/n−3 ratio was higher as concentrate intake increased (
FA (g 100 g−1) | Treatment1 | SEM | P<2 | ||
---|---|---|---|---|---|
T3.5 | T7.0 | T10.5 | |||
C4:0 | 4.60 | 4.36 | 4.37 | 0.06 | 0.13 |
C6:0 | 2.67 | 2.60 | 2.60 | 0.06 | 0.07 |
C8:0 | 1.45 | 1.44 | 1.48 | 0.05 | 0.07 |
C10:0 | 2.96b | 3.00b | 3.09a | 0.10 | 0.02 |
C10:1 | 0.33 | 0.33 | 0.35 | 0.02 | 0.17 |
C12:0 | 3.52b | 3.60ab | 3.71a | 0.11 | 0.04 |
C13:0 | 0.12 | 0.11 | 0.12 | 0.005 | 0.50 |
C14:0 | 12.17 | 12.12 | 12.38 | 0.19 | 0.65 |
C14:1 c9 | 0.94 | 0.96 | 1.02 | 0.03 | 0.35 |
C15:0 | 1.37 | 1.26 | 1.26 | 0.03 | 0.15 |
C15 iso | 0.26 | 0.28 | 0.25 | 0.01 | 0.34 |
C16:0 | 28.36 | 27.47 | 27.47 | 0.61 | 0.27 |
C16:1 c9 | 1.53 | 1.48 | 1.50 | 0.02 | 0.51 |
C17:0 | 0.72 | 0.68 | 0.64 | 0.01 | 0.09 |
C18:0 | 9.62 | 9.97 | 9.58 | 0.17 | 0.38 |
C18:1 t11 (VA) | 3.31 | 3.27 | 2.99 | 0.21 | 0.26 |
C18:1 c9 | 16.79 | 17.49 | 17.71 | 0.24 | 0.21 |
C18:2 n6 | 2.04b | 2.24b | 2.56a | 0.06 | 0.03 |
C18:3 n3 | 1.30a | 1.07b | 0.93c | 0.04 | 0.02 |
CLAc9. t11 (RA) | 1.18 | 1.16 | 1.15 | 0.08 | 0.75 |
C22 + C20:4 n6 + C20:3 n3 | 0.22 | 0.23 | 0.21 | 0.01 | 0.53 |
∑ C12:0 to C16:0 | 44.04 | 43.18 | 43.55 | 0.63 | 0.60 |
n−6/n−3 ratio | 1.56c | 2.10b | 2.77a | 0.05 | 0.01 |
Antioxidant vitamins (µg g milk fat−1) | |||||
Retinol | 5.45 | 5.62 | 4.97 | 0.67 | 0.55 |
α-tocoferol | 36.63 | 41.94 | 36.83 | 1.99 | 0.30 |
γ-tocoferol | 0.67 | 1.12 | 1.11 | 0.11 | 0.16 |
β-carotene | 4.73 | 7.12 | 5.99 | 0.41 | 0.07 |
1Values are expressed as least square means (LSMeans) and standard error of LSMeans (SEM). 2Treatment effect. a,b,cWithin rows means with different superscripts differ (Tukey-Kramer test, P < 0.05). VA = vaccenic acid. RA = rumenic acid.
The hypercholesterolemic fraction of milk fat (C12:0 to C16:0.) remained unchanged when levels of concentrate intake increased. Linolenic (C18:3 n3) concentration was lowered and the n−6:n−3 ratio raised but it remained below the recommended values (<4:1) for human health. Antioxidant vitamin content of milk fat was not significantly altered in spite of the lower pasture DM intake (−21%) between T3.5 and T10.5 (
The linear response in milk production observed in this trial (
In grazing conditions, milk protein content is often increased after the intake of starchy concentrates [
According to [
Milk lactose content linearly increased with concentrate intake (
The lack of changes in 4% FCM and ECM production when concentrate intake exceeded 28% of total DM intake (
The increase of casein content and the trend to the lower milk urea nitrogen with gradual increases in concentrate intake (
It was reported [
The estimated increase in NEL intake arising from concentrate (6.2 and 12.4 Mcal d−1 for T7.0 and T10.5, respectively) resulted higher than the decrease in NEL intake from pasture (−2.8 and −5.5 Mcal d−1 for T7.0 and T10.5, respectively) resulting in a higher total NEL intake (
According with previous findings [
Regardless the higher glucogenic energy theoretically absorbed when concentrate intake increased (
A lower ruminal pH is expected with increasing intake of starchy concentrates in grazing dairy cows [
In line with the previously reported studies [
The lack of significant changes in total VFA concentration (
It was reported that feeding corn-based concentrates does not affect the in situ pasture NDF digestion [
The most remarkable feature in the present trial was that the consumption of concentrate up to 40% of total DM, did not affect either the total vaccenic acid (VA) or conjugated linoleic acid (CLA) content in milk. The average CLA concentrations (1.16 g/100g FA) obtained were similar to 1.2 g percent, as previously reported for dairy cows grazing alfalfa pastures [
Antioxidant vitamins content was also not affected by concentrate feeding. Moreover the average concentrations of all-trans β-carotene and retinol in the present work were similar to those found by [
Increased levels of concentrate intake was an effective tool to improve milk yield in grazing dairy cows fed good quality alfalfa pastures without affecting pasture fiber digestion. Additive effects for DM and energy intakes were observed even when forage quality and quantity were non-limiting. Increased consumption of glucogenic energy failed to improve milk protein content but casein concentration and protein yield were enhanced. The increase in BW gain with increasing concentrate intake was compatible with the reduction of the circulating levels of NEFA and the reduction in the rumen acetate:propionate ratio but not with the absence of increases in plasma insulin concentration or decreases in the GH/insulin ratio, parameters that were not altered by supplementation levels. We have demonstrated for the first time that the increase on concentrate intake, up to 40% of total DM, did not affect the concentration of bioactive micronutrients in milk maintaining the healthy value of the milk produced.
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.
Salado, E.E., Bretschneider, G., Cuatrin, A., Descalzo, A.M. and Gagliostro, G.A. (2017) Milk Yield and Composition and Pasture Ruminal Digestion in Grazing Dairy Cows Receiving Three Levels of Energy Concentrate Supplementation. Agricultural Sciences, 8, 1135-1156. https://doi.org/10.4236/as.2017.810083