composição quimica.pdf

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Research Article

Re ce ived : 1 Dec embe r 2011 Re vise d: 5 April 2012 Acc epted : 16 April 2012 Published online in W iley O nline Library: 1 June 2012

(wileyonlinelibrary.com) DOI 10.1002/jsfa.5735

Chemical composition and sensory quality of

bovine milk as affected by type of forage andproportion of concentrate in the feed ration

Mette K Larsen,a Ulla Kidmose,b Troels Kristensen,c Pierre Beaumonta

and Grith Mortensena

Abstract

BACKGROUND: The objective of this study was to investigate how some small changes in the forage content of maize andlucerne silage and in the ration between forage and concentrate in the diet of dairy cows affect milk quality. Milk qualitywas assessed by quantitative descriptive sensory analysis and by analysis of tocopherols and carotenoids as well as fatty acid

composition.

RESULTS: Changing the ratio between maize silageand lucerne silagefrom 5 : 1 to 2 : 1 increasedmilk fat content of carotenoids(2327%) and C18: 3 n3 (15%), and reduced stale aroma and creamy flavour. Increasing the proportion of concentrates in thefeed ration from 0.2 to 0.4 increased energy corrected milk yield (26%), reduced fat content (10%), increased C18 fatty acids(862%) and reduced C16(20%) content in milk fat. In addition, this milk type was described bythe sensory panel as lessoily,less saturated and less yellow. The changes in milk composition were related to differences in feed composition.

CONCLUSION: The study revealed the potential to produce milk with a distinct composition and sensory quality based on evensmall changes in the feed composition that are straightforward to implement by farmers.c 2012 Society of Chemical Industry

Keywords: bovine milk; fatty acids; sensory evaluation; antioxidants; feeding

INTRODUCTIONCertain types of forage plants or other feedcomponentsmay influ-

ence milk composition andaffect sensory as well as thenutritional

and technological quality of the dairy products. Additionally such

production conditions may affect the productivity and environ-

mental load. This may be used in the marketing of the produced

dairy products.

Numerous studies have been conducted to assess the effect

of various forage types on the milk composition, especially milk

fatty acid composition.1 5 High contents of polyunsaturated fatty

acids, in particular C18: 3 n3 and conjugated linoleic acid (CLA)

cis9 trans11 in milk fat, are desirable due to positive effects on

human health.

1,6

The main sources of polyunsaturated fatty acidsin normal cow diets are forage, especially grass crops (including

legumes such as clover and lucerne), and oil seeds or oil seed

by-products used as concentrates.1,2,79 Only minor amounts of

the ingested polyunsaturated fatty acids from feed are recovered

in the milk as these fatty acids are hydrogenated to a wide extent

during the ruminal processes.10

A higher content of polyunsaturated fatty acids makes the

milk more susceptible to oxidation, but this oxidation is delayed

to some extent by the inherent content of antioxidants such as

tocopherols, carotenoids and urate.5,1114

Forages as well as oil seeds contain various amounts of

tocopherols and the main source of carotenoids is forage,

especially fresh grass and legumes and silage of grass and

legumes.15 Urate is synthesised during the ruminal processes,

and the amounts are affected by the feed structure.13

The sensory quality of milk is affected by direct transfer of

aroma compounds from feed to milk, but also by formation of

aroma compounds during feed digestion.16The effects of pasture

the composition of milk aroma compounds as well as the sensory

properties have been studied, and milk from cows consuming

pasture has a higher content of a range of aroma compounds,

whereas the sensory properties have been described as more

barny, or more salty, grassy, mothball and less sweet, sweet malty,

sweet aromatic compared to milk from cows fed a total mixed

ration (TMR).1618 CompositionoftheTMRalsoaffectsmilksensory

propertiesandmaizesilagecomparedtograsssilagegivesahigher

Correspondence to: Mette K Larsen, Department of Food Science, Aarhus

University, DK-8830 Tjele, Denmark. E-mail: [email protected]

Present address: VetAgroSup Clermont-Ferrand, Dept of Food Science, Site de

Marmilhat, FR-63370 Lempdes, France.

a Aarhus University, Department of FoodScience,BlichersAll e 20,DK-8830 Tjele,

Denmark

b Aarhus University, Department of Food Science, Kirstinebjergvej 10, DK-5792

Aarslev, Denmark

c Aarhus University, Departmentof Agroecology, Blichers All e 20,DK-8830 Tjele,

Denmark

J Sci Food Agric2013; 93: 9399 www.soci.org c 2012 Society of Chemical Industry


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www.soci.org MK Larsenetal.

sweet corn odor and less boiled milk, sour/buttermilk, cardboard

and metallic flavour.3,19 Feeding different lipid sources has only

minor effects on milk sensory properties.5,19,20

These results indicate that the sensory quality of milk is highly

affected by forage composition, i.e. the type of forage as well as

the proportion of forage in the ration. Thus, the hypothesis of the

present work was that milk composition and sensory quality are

affected by even small variations in the proportion of forage and

concentrate as well as the variations in the composition of forage

and concentrates which could be observed between commercial

dairy farms.

EXPERIMENTALAnimals, feeding and production

The experiment involved 72 Danish Holstein cows (mean at start:

86 37 days post partum, 30.1 5.7 kg energy corrected milk

yield) in a traditional production trial with eight treatments in

a balanced 2 2 2 design. Cows were randomly allocated to

treatments (nine cows per treatment) during an experimental

period of four weeks. The treatments were:

Ratio between maize silage and lucerne silage (5 : 1 or 2 : 1,

respectively)

Type of concentrate (barley or beet pulp in combination with

rape seed cake)

Proportion of concentrate (200 or 400 g kg1 of planned dry

matter intake)

Maize was cut when the dry matter content in the total plant

reached 320 g kg1 and ensiled in a bulk silo. Lucerne silage was

from the primary growth and cut when one tenth of the plants

were flowering. After 1 day of wilting in the field plants were

chopped and ensiled in a bulk silo.

All cows were housed in one group with ad libitum access

to one of the four different TMRs (Table 1) through Insentec

feeders (Insentec B.V., Marknesse, The Netherlands) controlling

the individual access and monitoring the intake. In addition, the

cows assigned to the high proportion of concentrate treatments

(400 g kg1 of dry matter intake) were fed 2.2 kg dry matter

rapeseed cake in combination with either 2.2 kg dry matter barley

or 2.2 kg dry matter dried beet pulp at automatic feeding stations

in the barn controlling the individual access and the amount of

feed, the type of concentrate being identical to the type given in

the TMR for the individual cow.

Table 1. Composition (g kg1 of drymatter) of thetotal mixed rationfedad libitum

Maizelucerne ratio 5 : 1 Maizelucerne ratio 2 : 1

Component Barley Beet pulp Barley Beet pulp

Barley 100 100

Beet pulp 100 100

Rapeseed cake 94 94 94 94

Maize silagea 655 655 527 527

Lucerne silageb 135 135 263 263

Urea 6 6 6 6

Mineral 10 10 10 10

a DM 360 g kg1, ash 33, protein 85, starch 320, NDF 390 g kg1 DM.b DM 300 g kg1, ash 128, protein 220, NDF 440 g kg1 DM.

The composition of each TMR fed through the Insentec feeders

was measured daily. Individual intake of TMR as well as additional

concentrates was registered at each feeding bout and daily intake

was calculated. Individual milk recordings were performed six

times during the experimental period representing 24-h milk yield

from an afternoon andthe followingmorningmilking. Milk fatand

protein analysis for registration of production was based on these

samples.

Sampling

Representative samples of each feed component were taken

weekly and were stored at 20 C until analyses of the fatty acid

composition and the content of tocopherols and carotenoids was

performed.

Individual milk samples were collected from two morning

milkings during the last week of the experiment and sub-samples

werefrozen immediately after sampling and stored at20 C until

analyses were performed for contents of tocopherols, uric acid

and carotenoids, fatty acid composition and colour measurement.

For sensory analysis, cows were milked in groups according to

treatments, and a 30 L milk sample was withdrawn from the bulk

milk of eachtreatment. Milk samples were pasteurised (72

C, 15 s)within 6 h after milking, poured into 2-L milk plastic bottles that

were placed in ice water and kept at 1 C until sensory analysis

was carried out the next day.

Chemical analysis

Milk fat and protein contents were analysed using a Milkoscan

4000 (Foss, Hillerd, Denmark). The milk colour was measured

using a Minolta Chroma Meter (Minolta Co. Ltd, Osaka, Japan)

and the CIE (Commision Internationale dEclairage) Lab scale

with standardised daylight (D65). The L, a and b values

reflect lightness (0 = black, 100 = white), redness (100

= green, 100 = red) and yellowness (100 = blue, 100 =

yellow), respectively. The instrument was calibrated against a

white standard plate. Milk (14 mL) was poured into a white

porcelain basin (diameter 45 mm, height 30 mm) and colour was

measured on the liquid surface, i.e. where the front plate of

the instrument just touched the surface. Urate was analysed as

described previously.13

Feed samples were mixed with liquid nitrogen and ground by

use of a domestic coffee grinder to obtain sizes of2 mm length.

Carotenoids and tocopherols were extracted and analysed using

either 1 g ground feed sample or 2 mL milk sample as described

by Slotsetal.,21 with the following modification: HPLC analysis of

carotenoids wascarriedout using a YMCC30 column (YMC Europe

GmbH, Dinslaken, Germany), 250 4.6 mm i.d., 5 m particle size,

operatedatatemperatureof25 C.Isocraticelutionwascarriedout

with ethanol/methanol/tetrahydrofuran (75 : 20 : 5) (v/v/v) with aflow rate of 1 mL min1, and chromatograms were recorded at

450 nm.

For fatty acids analysis, cream was separated from skim milk by

centrifugation (1700 g, 4 C, 20 min), subsequently cream was

centrifuged (13 000 g, 20 C, 10 min) to separate fat. A liquid

fat fraction was obtained by heating at 60 C for 10 min and

centrifugation (13000 g, 40 C, 10 min). Ten milligrams of milk

fat was dissolved in 1 mL pentane and 10 L 12.5 mol L1 sodium

methylate in methanol was added for methylation. Samples were

mixed for1 min andleft for10 min at ambient temperaturebefore

centrifugation (13 000 g, 4 C, 5 min). The supernatant was used

foranalysis by gaschromatography.Fatty acids fromherbage were

isolated and methylated as described by Palmquist and Jenkins.22

wileyonlinelibrary.com/jsfa c 2012 Society of Chemical Industry J SciFood Agric2013; 93: 9399


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Milk quality affected by forage and concentrate www.soci.org

Table 2. Feed intake and effect of ratio between maize and lucerne and share of concentrate on milk production

Proportion of silage,maizelucerne

Amount of concentrate indry matter intake

Effect of silage Effect of amount

Parameter 5 : 1 2 : 1 proportion 20% 40% of concentrate

Feed intake (kg DM day1) 20.2 19.7 NS 18.1 21.7


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Table 3. Effect of ratio between maize and lucerne and share of concentrate on milk composition

Proportion of silage,maizelucerne

Amount of concentrate indry matter intake

Effect of silage Effect of amount

Parameter 5 : 1 2 : 1 proportion 20% 40% of concentrate

Fatty acids (mg g fatty acids1)

Sum C6 C14 19.9 20.0 NS 19.9 20.0 NS

C16 : 0 27.6 29.2


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Milk quality affected by forage and concentrate www.soci.org

Table 4. Effect of ratio between maize and lucerne and share of concentrate on sensory attributes

Proportion of silage,maize : lucerne

Amount of concentratein dry matter intake

Effect of Effect of amount

Attibutes 5 : 1 2 : 1 silage proportion 20% 40% of concentrate

Aroma attributes

Creamy aroma 4.2 4.6 NS 4.6 4.2 NS

Metallic aroma 2.7 2.3 NS 2.6 2.4 NS

Cowstable aroma 2.3 2.3 NS 2.1 2.5 NS

Stale aroma 4.0 3.0


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treatments were observed for these compounds. Furthermore,

the loading vector of creamy flavour had high scores of the first

as well as the second PC although this attribute was not affected

significantly by the amount of concentrate which was the main

X variable of the first PC. Thus, several properties which did

not show significant differences in the univariate analysis were

affected by treatments according to the multivariate analysis and

such differentresults shouldbe explainedby the differentnatures

of univariate and multivariate analysis.

Effect of feeding on fatty acid composition

The loadings plot (Fig. 2) shows that higher contents of C18 : 3

n3, C18:2n6 and C18 : 1 in milk fat were directly related to feed

content of these components. The content of C18 : 0 in milk fat

was related to the content of all C18 fatty acids in feed instead

of the content of C18 : 0 in feed, due to the fact that a major part

of the unsaturated fatty acids from feed are hydrogenated in the

ruminal metabolism.10

These findings confirm that the content of unsaturated C18

fatty acids in milk fat can be increased by increasing the content

of these compounds in feed. Apart from supplying the fatty acids,

a higher fat content in feed also reduces rumen hydrogenationwhich gives a higher recovery of C18 : 3n3 and C18: 2n6.7,24 The

main feed source of C18 : 3n3 was lucerne silage, and the content

of this fatty acid in milk fat was higher when the proportion of

lucerne in forage was higher. However, an increased proportion of

concentratealso increasedthe C18: 3 n3 content in milk fat, which

was due toa combinationof C18 : 3 n3 supply from rapeseed cake

and the fat content of rapeseed cake, giving a protection against

hydrogenation.

The content of C18 : 1 trans11 in milk fat was also closely

related to the rapeseed cake because this fatty acid is a product

of partial hydrogenation in the rumen of polyunsaturated C18

fatty acids.10 Higher fat content in rapeseed cake may reduce the

final hydrogenation step and in this way also increase the C18 : 1trans11 content in milk fat. CLA cis9trans11 is mainly formed by

udder desaturation of C18 : 1 trans11 and these two fatty acids

were closely related as commonly found.2 Other research has

reported a higher content of C16 in milk fat from cows fed maize

silage and higher contents of C18 : 0, C18 : 1 and C18 : 3 n3 in

milk fat are observed when cows are fed lucerne silage due to a

higher fat content in the lucerne based feed.25 Lucerne has also

been reported to create more stable rumen environments where

hydrogenation is more complete.26This results in a higher content

of C18 : 0 in milk fat; however, the content of C18 : 3n3 in milk fat

is still elevated due to the higher feed content of this fatty acid.26

As shown in Fig. 2, the milk fat content was negatively related

to thefeedcontent of rapeseed cake. This mightbe dueto a slight,

non-significant milk fat depression caused by the higher contentof unsaturated fat in the rapeseed cake.2,9

The content of C16 in milk fat was not related to the feed

content of C16 because this fatty acid is also de novosynthesised.

It is evident that a lower supply of fat from feed leads to a higher

de novosynthesis.9,27

Effect of feeding on antioxidants

Tocopherolsand carotenoids in the feed were closely correlated to

identical compounds in milk (Fig. 2). These findings confirm that

the milkcontents of tocopherols and carotenoids can be increased

by increasing the feed content of these compounds. Figure 2 also

reveals that the main feed source of carotenoids was lucerne

silage, which, as well as rapeseed cake, was the major source

of -tocopherol, while rapeseed cake was the most important

source of-tocopherol. The levels of tocopherol and carotenoids

in milk were similar to values in milk fromcows fed maize silage.12

When feed concentrations of carotenoids and tocopherols are

enhanced, the effects on milk content decreases as only a limited

amountof carotenoids andtocopherols canbe secreted in milk on

a daily basis.15,28 The present study indicated that concentrations

of antioxidants were relatively low, and this explains the positive

relationshipbetween thecontentof antioxidantsin feed andmilk.

Effect of feeding on sensory characteristics

Milk yellow colour (b values) were positively affected by higher

lucerne amounts as well as higher forage intake, and to some

extent related to carotenoids; however, more specifically related

to fat. Similarly, yellow colour (b values) are reported to be related

to carotenoid content of milk and feed content of grass products,

however, other components such as riboflavin also affect the

colour, and therefore, yellow colour (b values) cannot directly

predict-carotene content.15,17,29,30

The visual sensory attributes (yellowness, saturation and oilyappearance) were closely connected and were related to creamy

aroma, fat content, yellow and white colour (b and L values)

(Fig. 2). These attributes were associated with high forage levels.

In contrast, high concentrate levels were associated with cow

stable aroma. This was not in accordance with previous results

in which milk from grazing cows has a more barny, salty and

grassy flavour than milk from cows fed a total mixed ration, which

has a sweeter and more malty flavour.17,18 Feeding with maize

has led to a higher intensity of cream flavour, maize odour and

sweet corn flavour, whereas grass silage has led to an increased

intensity in boiled milk flavour, sour flavour, cardboard flavour

and metallic taste.3 Although grass silage and the attribute maize

flavour were not included in the study, the higher intensity of

creamy flavour with increased maize silage was in accordancewith previous results.3

The results show that milk composition including sensory

properties were affected by composition of forage as well as

proportion of forage to concentrate, whereas the different types

of concentrate did not affect milk quality. This knowledge can be

used to develop guidelines for feeding of dairy cows targeted at

production of milk with distinct properties. If such type of milk

is used for production of dairy products, product composition as

wellas sensory properties includingappearance could be affected.

ACKNOWLEDGEMENT

This projectwas fundedby the Danish Ministry of Food, Agricultureand Fisheries and by the Danish Cattle Federation.

REFERENCES1 Dewhurst RJ, Shingfield KJ, Lee MRF and Scollan ND, Increasing the

concentrations of beneficial polyunsaturated fatty acids in milkproduced by dairy cows in high-forage systems. Anim Feed SciTechnol131:168206 (2006).

2 Grummer RR, Effect of feed on the composition of milk-fat.J Dairy Sci74:32443257 (1991).

3 Mogensen L, Vestergaard JS, Frette X, Lund P, Weisbjerg MR andKristensen T, Effect of toasting field beans and of grass-clover:Maizesilage ratioon milk production,milk compositionand sensoryquality of milk.Livest Sci128:123 132 (2010).

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