Science and Technology [600369]

Journal of Food, Agriculture & Environment, V ol.10 (3&4), July-October 2012 815 www.world-food.net Journal of Food, Agriculture & Environment Vol.10 (3&4): 815-818. 2012 WFL Publisher
Science and Technology
Meri-Rastilantie 3 B, FI-00980
Helsinki, Finland e-mail: [anonimizat]
Effect of feeding type (pasture vs. total mixed rations) of Turcana ewes on animal
performance and milk fatty acid profile
Daniel Mierlita
University of Oradea, Department of Animal Science, 26 Magheru, Oradea 410087, Romania. e-mail: [anonimizat]
Abstract
The objective of this study was to investigate the effect of feeding type (pasture vs. total mixed rations) of Turcana ewes on animal performance and
profile of fatty acids (FA) of milk fat. The diets were pasture without supplementation (P) and total mixed ration (TMR 1.5 kg grass hay and 700
g mixed concentrates). Milk produced by ewes in TMR group had a higher proportion of fat in milk and a higher energy corrected milk (ECM) (p
<0.001). No differences were noticed between the dietary groups in respect of milk protein and lactose content. FA profile of m ilk fat produced by
ewes in group P was more favourable for humans, due to higher concentrations of α-linolenic acid (ALA), c9,t11-CLA (RA; rumenic acid) and
t11,C18:1 (V A; vaccenic acid which is a precursor to CLA in humans) (p <0.001) and lower content of saturated fatty acids with high
hypercholesterolemia potential. Decreased content in saturated FA (especially hypercholesterolemic FA: C12:0, C14:0 and C16:0) led to lower
atherogenic index of milk fat of ewes maintained on pasture, compared with ewes in whose diet concentrates and hay were introdu ced. TMR diet
caused a significant increase in milk yield and fat content but also an increase in saturated fatty acids (SFA: C6:0, C8:0, C10 :0, C14:0, C16:0) and a
decrease of monounsaturated FA (C16:1, t11-C18: 1 and c9-C18:1) and polyunsaturated FA (c9,t11-C18:2, C18:3 n-3). When the qual ity and
availability of pasture does not limit milk yie ld, using TMR diets in Turcana ewes was not recommended because adverse effects on the FA profile
in milk, even if it has a positive effect on milk yield and fat content.
Key words: Ewe’s milk, α-linolenic acid and rumenic acid, atherogenic index, Turcana breed. Received 12 June 2012, accepted 6 October 2012.
Introduction
To improve the nutritional characteristics and impact of milk fat on human health, fatty acids (FA) profile must be modified for increasing the proportion of polyunsaturated fatty acids (PUFA), especially conjugated linoleic acid (CLA) and
α-linolenic acid (C18: 3),
at the expense of saturated fatty acids (SFA). It is widely recognized that dietary factors have a supreme role in modulating fatty acid profile in milk from cows
1, goats 2, 3 and ewes 4-7. Traditionally,
Turcana ewes fed on mountain pastures were not supplemented with concentrates
8. TMR diets p romote milk production, milk fat
and protein content 9. However, this type of diets often have a
detrimental effect on FA composition of milk fat, since SFA increased and C18:3, CLA and V A (vaccenic acid, t11C18:1) decreased. FA composition of milk fat reflects the nutritive value of the pasture and is influenced by its intake level
10. The sheep
milk is much richer in n-3 FA and CLA than the cow milk; a possible reason might be that sheep are pasture-fed, while dairy cows are usually fed on preserved and concentrate feed
11.
The objective of this study was to investigate the effect of
feeding ration structure (pasture vs. total mixed rations) on production parameters and, in particular, on milk fatty acid profile.
Materials and Methods
The study was conducted at the University of Oradea for 10 weeks, of which the first three weeks were used to adjust the types of feed rations meant to be tested. Twenty Turcana ewes were divided into 2 homogeneous groups (10 ewes/group), which were randomly assigned to one of the tested feed rations: pasture (P) without additional ration and total mixed ration (TMR) consisting of 1.5 kg grass hay and 700 g mixed concentrates (consisting of corn 58%, triticale 20%, soybean oil cakes 18% and vitamin-mineral premix 5%).
Ewes were grazed together on a mountain pasture (1248 m altitude),
consisting of a mixture of Festuca rubra , Phleum pratense , Poa
pratensis , Dactylis glomerata and Trifolium repens .
Ewes were milked twice daily (at 07:00 and 20:00 o’clock),
individual milk production being recorded daily. Milk fat content, crude protein (N x 6.38) and lactose were determined weekly. At week 6 and 10 of experimental period, milk samples were taken from two consecutive milking, in order to determine the FA profile of milk fat.
Fodder samples were collected in weeks 3, 5, 7 and 10 of
experimental period (n = 4) and analyzed for DM
12, NDF (Neutral
Detergent Fiber), ADF (Acid Detergent Fiber) (Fibersac with an
Ankom Technology analyzer, Fairport, NY)13, N (Kjeldahl method)
and crude fat 14.
Milk samples were preserved using 2 tablets of Bronopol®
(BroadSpectrum Micro-tabs II, D&F Control Systems Inc., USA). They were kept in a refrigerator at 4°C until the determination of fat and protein by infrared analysis (Milk Analyser System 4000, Foss Electric, Hillerod, Denmark). Lactose content was determined using an enzymatic method
27. Samples of milk collected at weeks
6 and 10 for fat FA profile analysis, were frozen at -20°C, without preservatives.
To determine the FA profile in fodder fat, fatty acids methyl

816 Journal of Food, Agriculture & Environment, V ol.10 (3&4), July-October 2012 esters (FAME) were obtained by the method with a single step of
extraction-methylation 15. Quantification of fatty acids was done
using 4 mg of C17:0 as internal standard. To determine the composition of fatty acids in milk, fat was extracted in accordance with international standard ISO 14156/FIL 172:2001. Fatty acid methyl esters (FAME) were prepared in accordance with the method proposed by Christie
16 and Chouinard et al. 17. FAME were
determined by gas chromatography using a Varian GC 3600 equipped with FID and a melted silica capillary column (Supelco SP 2560), 100 m × 0.25 mm id and film thickness of 0.20 µm. The carrier gas was
helium at a rate of 1 ml/min. Oven temperature was programmed at 70°C and held for 1.5 min, then it was raised to 190°C at a rate of 8°C/ min, for a period of 25 min. and then increased to 230°C at a rate 15°C/ min., for 7 min. Injector and detector temperature was set at 270°C.
Atherogenic index (AI) was calculated according to Chilliard et al.
18,
using the following equation: (C12:0 + 4 x C14:0 + C16:0)/ unsaturated FA.
All statistical analyses were performed using the Mixed
statistical procedure of SAS
19. Analyses of data concerning milk
yield, milk composition, FA composition, ∆9-desaturase enzyme
and AI were done using Proc Mixed in a repeated measures design. The significance level was declared at p <0.05.
Results and Discussion
Chemical composition and content of main fatty acids in fodder used (pasture, total mixed ration) are presented in Table 1. All fodders and, particularly, total mixed ration were good source of linoleic acid (C18: 2), but the pasture was richer in α-linolenic acid
(C18: 3) (41.32% of total FAME), these results are consistent with
those mentioned in the literature
6, 20, 21.
Milk production was affected by experimental factors (ration
structure) (Table 2), ewes in TMR group showed a tendency to
increase milk production (p <0.001), and milk fat content and fat production increased. Fodder fiber content is considered to be a key factor in achieving a higher fat content in milk
22. Ewes in TMR group had a higher percentage of fat in milk and a higher daily production of fat and corrected milk production (ECM = energy corrected milk) was significantly higher compared with ewes in P group. Milk content of protein and lactose were not affected by ration structure. Results on the effect of experimental factors on milk fatty acids profile are presented in Table 3.
Diet based with concentrates and hay (TMR), has led to
increased milk fat content in saturated fatty acids (SFA: C6:0, C8:0, C10:0, C14:0, C16:0) and decreased the amount of monounsaturated FA (C16:1, t11-C18: 1 and c9-C18:1) and polyunsaturated FA (c9,t11-C18:2, C18:3). The results suggest that
Specification Pasture TMR
Chemical composition (g/kg DM)
Dry matter (DM) 288 863
Crude Protein (CP) 153.7 148.75
Crude Fat 26.6 24.15
NDF 478.5 309.2
ADF 293.1 186.4
Content in fatty acids(% of FAME)
C12:0 0.69 0.55 C14:0 0.95 0.71
C16:0 18.77 14.58
C16:1 0.43 0.51
C18:0 2.57 4.08
C18:1 5.81 14.91
C18:2 24.63 39.26
C18:3 41.32 16.87
C20:1 0.74 0.87
SFA
2 22.83 19.92
MUFA3 6.55 16.34
PUFA4 64.34 56.12
Others 6.28 7.62 Table 1. Chemical composition and fatty acid contents
of fodder used in ewes’ feeding1.
DM = dry matter; NDF = Neutral Detergent Fiber; ADF = Acid Detergent Fiber; FAME
= fatty acid methyl esters. 1Data presented are least square means (n = 4), except for
FA (fatty acid) profile (n = 2 samples per feeds). 2SFA = saturated FA (C12:0 + C14:0
+ C16:0 + C18:0); 3MUFA = monounsaturated FA (C16:1 + C18:1 + C20:1 + C22:1);
4PUFA = polyunsaturated FA (C18:2 + C18:3). Ration structure3 P TMR SEM4 P5
C4:0 2.50 2.17 0.230 0.10
C6:0 2.42 2.35 0.123 0.24
C8:0 2.49 2.52 0.316 0.12
C10:0 5.95 7.75 0.143 < 0.001
C12:0 3.60 4.87 0.101 <0.001
C14:0 8.08 10.18 0.249 <0.01
C14:1 0.10 0.13 0.017 0.14
C15:0 0.79 0.95 0.067 <0.01
C16:0 17.41 23.56 1.122 <0.001
C16:1 0.53 0.72 0.112 <0.01
C17:0 0.45 0.60 0.074 <0.05
C18:0 15.18 11.30 0.423 <0.001
C18:1 n9t 0.68 0.29 0.160 <0.001
C18:1 trans -11 (VA) 5.09 2.67 0.314 <0.001
C18:1 n9c 23.28 20.77 0.543 <0.05
C18:1 cis-11 0.94 0.62 0.094 0.27
C18:2 n6t 0.34 0.32 0.066 0.63
C18:2 n6c 2.49 2.76 0.213 0.41
cis-9, trans -11 CLA (RA) 2.29 1.39 0.198 <0.001
C18:3 n-3 (ALA) 2.02 1.34 0.3246 <0.001
C20:0 0.40 0.32 0.056 0.16
C20:4 0.14 0.21 0.092 0.08 Others 2.88
2.21 0.317 0.12
Saturated FA 59.45 66.58 0.578 <0.001
Unsaturated FA 37.44 31.23 0.619 <0.001
Monounsaturated FA 30.10 25.20 0.354 <0.001
Polyunsaturated FA 7.34 6.02 0.271 <0.001
AI6 1.44 2.23 0.204 <0.001
ǻ9 – desaturase ratios:
16:1/16:0 + 16:1 0.028 0.030 0.003 <0.05
18:1/18:0 + 18:1 0.66 0.68 0.026 0.60 RA/VA + RA 0.30
0.34 0.015 <0.05 Table 3. Influence of feeding type (pasture vs. total mixed
rations) of dairy ewes on milk fatty acid profile1
(% of total FAME2).
1n = 10 ewes/group. 2FAME = fatty acids methyl esters; 3P: pasture without additional
ration, TMR: total mixed rations (1.5 kg grass hay and 700 g concentrates); 4SEM: standard
error of least square means. 5Significance for treatment effect. 6Atherogenic Index; MUFA
and PUFA: mono- and polyunsaturated fatty acids. RA: rumenic acid ( cis-9, trans -11
CLA); VA: vaccenic acid ( trans -11 C18:1); ALA: α-linolenic acid (C18:3 n-3). Table 2. Influence of feeding type (pasture vs. total
mixed rations) of dairy ewes on milk yield and its
composition1.
1n = 10 ewes/group. 2P: pasture without additional ration, TMR: total mixed rations (1.5 kg grass
hay and 700 g concentrates); 3SEM: standard error of least square means. 4Significance for
treatment effect. 5Energy Corrected Milk (ECM) = Milk yield (kg/day) x (0.071 x Fat (%) +
0.043 x Protein (%) + 0.2224). Ration structure2 P TMR SEM3 P4
Milk yield (g/day) 521.4 730.3 27.2 <0.001
ECM5 (kg/day) 0.481 0.720 0.122 <0.001
Fat (g/L) 67.3 77.8 3.57 <0.01
Fat (g/day) 35.09 52.9c 1.96 <0.001
Proteins (g/L) 51.8 49.1 2.34 0.68
Proteins (g/day) 27.00 35.86 1.12 <0.05
Lactose (g/L) 48.3 48.6 2.02 0.28 Lactose (g/day) 25.18 35.49 1.28 <0.05

Journal of Food, Agriculture & Environment, V ol.10 (3&4), July-October 2012 817 the introduction of concentrates and hay in lactating ewes’ diet,
led to important changes in the populations of rumen bacteria, which favoured biohydrogenation processes, thus a part of unsaturated FA from feed have been fully hydrogenated
21. This
argument is confirmed by significantly lower milk fat content of α-linolenic acid (ALA), rumenic acid (c9,t11-C18: 2) and vaccenic
acid (t11-C18:1), indicating more intense activity of the rumenal microflora responsible for PUFA biohydrogenation from the diet based with concentrate mixed and hay (TMR).
Increases in the concentration of C18:0, C18:1 cis-9 and C18:1
trans -11 in milk fat and decrease in C16:0 were found in grazing
sheep and cows compared with those fed with TMR
7, 23.
Ingestion of pasture with the ewes in group P resulted in
decreased content of linoleic acid (C18:2 n6c) and increased content of α-linolenic acid (ALA) in milk fat, according to the
structure of FA in feed. Increased content of α-linolenic acid,
rumenic acid and oleic acid in fat milk is an advantage of pasture- based feed ration, in terms of dietary fat impact on human
health
7.
Grazed ewes’ milk fat had over 65% more CLA cis-9, trans -11,
compared with ewes’ milk fat, which have had introduced in their feed concentrate mixed and hay. The positive effect of pasture on milk fat content in CLA cis-9, trans -11, was found previous, not
only in dairy cows, but also in lactating ewes and goats
7, 20, 24.
Metabolic pathways that lead pasture to increased c9,t11-CLA in milk are not well known. It is unknown how α-linolenic acid, which
predominates in the fat of the pasture (55-65% of total FA
25),
participates as an intermediate in the formation of c9,t11-CLA,
although pasture favours the formation of C18:1 trans -11 26.
Ewes maintained on pasture and whose ration was not
supplemented with other fodder, had in the milk fat the lowest concentration of FA C10:0, C14:0, C16:0 and C17:0 (p <0.10 to 0.05),
but they had the highest concentration of FA C18:0, t11- C18:1, c9-
C18:1 c9, t11-C18:2 and C18:3 in milk fat (p <0.05 to 0.001).
Decreased content in C12:0, C14:0 and C16:0 has led to lower
atherogenic index of milk fat of ewes maintained on pasture, compared with ewes in whose diet concentrates and hay were introduced.
The milk produced on pasture had a lower content in saturated
FA (FA especially hypercholesterolemia: C12:0, C14:0, C16:0) and higher in unsaturated FA, mainly c9, t11 CLA, t11 C18: 1 and n-3 FA.
Conclusions
Pasture is an important source of polyunsaturated FA, particularly α-linolenic acid, affecting milk FA profile. Ewes maintained on
pasture and whose ration was not supplemented with other fodder, had in their milk fat the lowest concentration of FA C10:0, C14:0, C16:0 and C17:0 (p <0.10 to 0.05), but, they had the highest concentration of FA t11-C18:1 (V A: vaccenic acid); c9, t11-C18:2 (CLA – rumenic acid) and C18:3 (ALA: α-linolenic acid) in milk fat
(p <0.05 to 0.001). TMR diet caused a significant increase in milk yield and fat content but the increased content in saturated fatty acids (SFA: C6:0, C8:0, C10:0, C14:0, C16:0) and decreased the amount of monounsaturated FA (C16:1, t11-C18: 1 and c9-C18:1) and polyunsaturated FA (c9,t11-C18:2; C18:3). Acknowledgements
This work was supported by CNCSIS – UEFISCDI, project number PN II – IDEI 679/2008.
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