ANALELE UNIVERSITĂłII DIN ORADEA Fascicula Ecotoxi cologie, Zootehnie și Tehnologii de Industrie Alime ntară [600509]

ANALELE UNIVERSITĂłII DIN ORADEA Fascicula Ecotoxi cologie, Zootehnie și Tehnologii de Industrie Alime ntară

THE EFFECT OF ENERGY AND PROTEIN LEVELS OF FEEDING ON MILK
YIELD AND RUMEN FERMENTATION IN DAIRY EWES

Mierlita Daniel

University of Oradea; Environmental Protection Facu lty, Gen. Magheru Street, no. 26, Oradea, eCmail:
[anonimizat]

Abstract

Keywords: energy and protein in the diet, milk, rumen fermen tation, dairy ewes.

The obiective of this trial was to evaluate the eff ect with different level energy and protein on
diet of caracteristics fermentation ruminal, yield and quality of sheep milk. Consequently,
experimental diets were constituted by a 2 x 2 fact orial arrangement of energy level in diets (Low –
0,90 UFL/kg DM vs. High – 0,97 UFL/kg DM) and prote in level (Low – 14% CP vs. High – 16%
CP). On a dry matter (DM) basis, forage : concentra te ratios were 73 : 27 (low energy diets) and 57 :
43 (high energy diets). Protein level diet were giv en either with soybean meal (5,5% of DM) or
without. Increased levels of protein and energy of diet in lactating sheep, influenced positively the
quantitative and qualitative production of milk. So , the average daily production of milk increased up
to 14.7% (p ≤ 0.05) and, also, fat, protein and lac tose content, but it decreased the casein
content(which could reduce the processing performan ce of milk in cheese) and nonproteic nitrogen.
After feeding, ewes fed the high energy and protein diets had higher proportion of propionate
and lower proportion of acetate and acetate/propion ate ratio than those fed the low energy and
protein diets. Sheep fed the high energy and high p rotein diets had lower NH 34N in ruminal fluid,
than those fed the low diets (p ≤ 0,05).

INTRODUCTION

The type and proportion of forages and concentrates in the diet may also
have a significant effect on the yield and composit ion of the milk given by
dairy ewes (Kukuk et al., 2001; Mele et al., 2006; Cannas et al., 1998;
Guitard et al., 1996; Bocouier et al. 2001; Bencini et al., 1997). The
concentration of fat in the milk is correlated posi tively with the
concentration of fibre in the diet. Bencini et al. (1997) have calculated the
relationship between milk fat and NDF in the diet ( fat% = 4,59 + 0,05 NDF;
r = 0,48).
The protein content of the diet affects the quantit y and the partition of
nitrogenous substances in the milk; that milk prote in was significantly
reduced if ewes were fed a protein deficient diet. Milk yield and
concentration of milk fat can be increased by incre asing the protein content
of the diet (Bencini et al. 1997).

The obiective of this trial was to evaluate the eff ect of energy and protein
content in the effect with different level energy a nd protein on diet of
caracteristics fermentation ruminal, yield and qual ity of sheep milk.

MATERIAL AND METHODS

Animals and diets
Researches were conducted on 48 lactating łurcană s heep (with a live
weight of 46,4 ± 4,2 kg and milk yield 0,61±0,12 k g), being at lactation 3
and 4, respectively, months 2C4 of lactation. The s heep were divided into 4
groups of 12 sheep/lot in a preexperimental period of 14 days, when feeding
was made with a basic portion and it was followed t he average milk yield
per lot, so it does not differ significantly from a lot to another. The animals
were kept in collective boxes (one box for a lot) o n the permanent straw
bedding, and food was administered twice daily (at 7.00 and 18.00), ad
libitum.
The analytical composition of the diet (table 1) ha ve also been reported.
The 4 experimental diets differed in terms of level energy and protein, of
forage/concentrate ratio respectively (diet composi tion expressed as the
percentage of dry matter):
C A diet with low energy and low protein (forage/co ncentrate ratio – 73 :
27), made up of forage (73%), corn grein (18,8%) an d triticale meal (7,2%);
C A diet with low energy and hig protein (forage/c oncentrate ratio – 73 :
27), made up of forage (73%), corn grein (13,3%), t riticale meal (7,2%) and
soybean meal (5,5%);
C A diet with high energy and low protein (forage/ concentrate ratio – 57 :
43), made up of forage (57%), corn grein (32,6%) an d triticale meal (9,4%);
C A diet with high energy and high protein (forage /concentrate ratio – 57 :
43), made up of forage (57%), corn grein (29,2%), t riticale meal (7,3%) and
soybean meal (5,5%).

Table 1
Feed ingredients of the experimental diets of dairy ewes (% DM)

Energy lelel Low – 0,90 UFL High – 0,97 UFL
Protein level 14% CP 16% CP 14% CP 16% CP
Grass hay 13,8 13,8 8,9 8,9
Mixed grass pasture 28,6 28,6 18,5 18,5
Alfalfa grass 30,7 30,7 29,8 29,8
Corn grein 18,8 13,3 32,6 29,2
Triticale meal 7,2 7,2 9,4 7,3
Soybean meal C 5,5 C 5,5
Minerals and vitamins 1 1,0 1,0 1,0 1,0
Forage : concentrate 73 : 27 73 : 27 57 : 43 57 : 4 3
1 : Contains (g/kg): I, 1,22; Mn, 103; Zn, 110; Fe, 137; Cu, 16; Co, 0,35; Se,
0,31; (IU/kg): vitamin A, 11000; vitamin D, 3200; v itamin E, 56.

Forage (grass hay, mixed grass pasture and lucerne grass) was fed
separately twice a day, controlling the actual inta kes of both forage and
concentrate.
The chemical composition of the diet was determined according to
AOAC methods (AOAC, 1990). Fiber fractions (NDF and ADF) were
analyzed according to the method described by Van S oest et al. (1991). Non
structural carbohidrates (NSC) were calculated acco rding to Van Soest et al.
(1991). Net energy for lactation (NE L) and intestinal digestible protein
(PDIN and PDIE) were estimated from INRA tables (19 89).

Experimental design
Experimental diets were constituted by a 2 x 2 fact orial arrangement of
level energy in diets (Low – 0,90 UFL/kg DM vs. Hig h – 0,97 UFL/kg DM)
and level protein (Low – 14% CP vs. High – 16% CP). After a 10Cday
adaptation period to the diets experiments, meant t o let the rumen microbes
get accustomed to the changed diet.

Milk yield and rumen fermentation
The animals were milked twice daily (at 06:00 h and 18:00 h). The two
samples were gathered in a single sample according to the morning and
afternoon yield. Milk samples were then analyzed to determine fat matter
(Gerber method), total nitrogen (Kjeldahl method, N x 6,38 = total protein),
lactose (infrared method, Combifoss 4000 FOSS, Hill erod, Denmark), and
fatty acids composition.
On week 6 experiments, ruminal fluid was colected b efore and 2 h after
the morning feeding. Following immediate determinat ion of pH, ruminal
fluid was acidified with 25% (wt/vol.) H 3PO 4 and frazen until analysis of
ammonia (Wheatherburn, 1967) and VFA (Kristensen et al. 2000).

Statistical analysis
Ruminal samples obtained before and 2 h after feedi ng were analyzed
separately with a model including the fixed effects of energy level, protein
level diet and their interaction. All other data we re analyzed using the GLM
procedure of SAS (SAS Inst. Inc., 1999). The statis tical model included
energy level, protein level, energy x protein inter action and residual error.
Data are reported as least squares means ± SEM. Ove rall diferences between
treatment means and interaction for level of energy leve land protein level
were considered to be significant when p ≤ 0,05.

RESULTS AND DISCUSSION

Diet composition
Portions with high energy value (0.97 UFL / kg DM) are characterized
by a lower content of fibers (NDF and ADF) and a hi gher content of ether
extract (EE) and nonstructural carbohidrates (NSC), comparing to low
energy value portions (table 2). The increase of fo od protein level from 14%
CP to 16% CP, by introducing soybean meal (5.5% of DM), regardless of
energy level, it determines the increase of ether e xtract (EE) share and the
decrease of nonCstructural carbohidrates (NSC) prop ortion.

Table 2
Chemical composition and nutritional values of expe rimental diets (% DM) 1
Energy lelel Low – 0,90 UFL High – 0,97 UFL
Protein level 14% CP 16% CP 14% CP 16% CP
CP (crude protein) 14,18 16,10 13,87 16,17
NDF 44,10 44,0 35,4 35,1
ADF 26,90 26,60 24,70 24,40
NSC 16,4 14,2 34,6 31,4
EE 1,72 2,17 2,52 3,08
PDIE (g/kg DM) 2 90,1 98,6 94,3 112,8
PDIN (g/kg DM) 2 86,1 102,4 89,3 108,7
NE L (kcal/kg DM) 3 1547 1561 1664 1678
1 Data presented are least square means (n = 4 sampl es per diet). 2PDIN and
PDIE = digestible CP in the intestine from microbia l protein synthesis when
availability of fermentable N in the rumen is limit ing, and from microbial
protein synthesis when availability of energy in th e rumen is limiting,
respectivively (INRA, 1989). 3 Calculated values (INRA, 1989).

DM intake, milk production and composition

Average dry matter intake (DMI) did not differ betw een experimental
groups (table 4).
Increasing energy level by increasing the proportio n of concentrates
from ration structure led to a significant increase of NEL intake (kcal / kg)
(p ≤ 0.01), but also to the quantitative and qualit ative improvement of milk
production. It was increased the average daily prod uction of milk (p ≤ 0.05)
and its fat, protein and lactose content and it was reduced the content in
nitrogen and non protein casein, which could negati vely influence the
performance of processing milk into cheese (table 3 ).
Table 3
The effect of energy and protein levels of feeding on production and
composition of sheep milk 1.
Energy lelel Low – 0,90 UFL High – 0,97 UFL p values of effects 2
Protein level 14% CP 16% CP 14% CP 16% CP SEM
E CP ExCP
DMI (kg/day)
NE L intake
(kcal/day)
Milk yield (kg/day)
Milk fat (g/l)
Milk protein (g/l)
Milk lactose (g/l)
Casein (g/l)
Fat yield (g/day)
Protein yield (g/day)
Lactose yield (g/day)
Non proteic nitrogen
Casein, % of CP 1,828
2828
0,585
66,7
53,4
47,4
40,4
39,0
31,2
27,7
1,34
75,6 1,837
2867
0,671
66,5
54,6
46,8
38,6
44,6
36,6
31,40
1,86
73,82 1,890
3145
0,628
64,7
58,2
48,8
38,3
40,6
36,5
30,6
1,17
72,8 1,885
3163
0,643
67,3
57,6
48,3
37,6
43,3
37,0
31,0
1,40
68,7 0,08
174
0,18
0,82
0,41
0,40
0.44
2,61
1,02
0,74
0,06
0,91 NS
**
*
*
*
*
**
*
*
**
**
** NS
NS
**
*
NS
NS
NS
**
NS
NS
**
NS NS
NS
NS
NS
NS
NS
NS
**
NS
NS
***
*
1 Data presented are least square means – n = 12 ewe s per group.
2 E = effect of energy level, CP = effect of protein level, ExCP = interaction
between energy and protein level diet. *** : p ≤ 0, 001; ** : p ≤ 0,01; * : p ≤
0,05.

Protein level of feed influenced positively the pro duction of milk (p ≤
0.01) and the content in fat of milk (p ≤ 0.05), bu t increased milk content in
nonCproteic nitrogen (p ≤ 0.01).
Robinson et al.; CalderonCCortes et al.; Cowan et a l. (cit. Bencini R.
1997), Pulina et al. (1995), Bocquier et al. (2001) , Gargouri, (2005);
Schmidely et al. (2001), all have shown that milk y ield and concentration of
milk fat can be increased by increasing the protein content of the diet. By
contrast Sinclair et al. (1990), Lynh et al. (1991) , Rossi et al. (1991) and
Cannas et al. (1995) raported that high concentrati ons of protein in the diet
can increase the concentration of non proteic nitro gen and especially ureea

which results in a poorer processing performance of the milk. Feeding highC
energy diets generally induce slow milk fat content in cow, ewes and goats
(Bauman et al., 2001; Sauvant et al., 2000). Positi ve effect of feeding highC
energy combined with highCprotein diet on milk fat/ protein ratio was also
obtained because milk protein content and protein y ield ewes not reduced,
in agreement with previous observations in sheep an d goats (Chilliard et al.,
2003; Schmidely et al., 2005).

Rumen fermentation
Ruminal pH, ruminal ammoniaCN and VFA (acetate, pro pionate and
acetate/propionate ratio) were affected by the diet ary factors or by their
interaction (table 4). Sheep fed the high energy di ets to have lower acetate
and higher butyrate molar proportion before feeding than those fed the low
energy diets. After feeding, ewes fed the high ener gy and protein diets had
higher proportion of propionate and lower proportio n of acetate and
acetate/propionate ratio than those fed the low ene rgy and protein diets.
Sheep fed the high energy and high protein diets ha d lower NH 3CN in
ruminal fluid, than those fed the low diets (p ≤ 0, 05).

Table 4
Fermentation characteristics in the ruminal fluid c ollected of 2 h after feeding in
dairy ewes fed low C or high – energy and protein d iets 1.
Energy lelel Low – 0,90 UFL High – 0,97 UFL p values of effects 2
Protein level 14% CP 16% CP 14% CP 16% CP SEM
E CP ExCP
pH
VFA, mol/100 mol
C Acetate
C Propionate
C Butyrate
C Isobutyrate
C Valerate
C Isovalerate
Acetate/propionate
Ammonia – N, mM 6,70

68,4
16,7
12,2
1,82
0,77
0,11
4,09
3,38 6,82

67,5
18,2
11,9
1,40
0,90
0,10
3,71
4,30 6,30

64,0
19,0
13,3
2,31
0,96
0,43
3,36
3,13 6,21

65,3
21,0
11,4
1,34
0,87
0,09
3,11
3,01 0,05

0,50
0,47
0,31
0,07
0,03
0,05
0,11
0,45 *

***
***
NS
NS
NS
NS
***
NS NS

NS
*
*
*
NS
NS
*
NS NS

*
NS
NS
NS
*
*
NS
*
1 Data presented are least square means – n = 4 ewes per group – 2 h after
feeding
2 E = effect of energy level, CP = effect of protein level, ExCP = interaction
between energy and protein level diet. *** : p ≤ 0, 001; ** : p ≤ 0,01; * : p ≤
0,05.
CONCLUSIONS

1. Increased energy level of lactating sheep food(0 .90 UFL / kg DM vs. 0.97
UFL / kg DM) by increasing the share of concentrate s in the ration
(from 27% to 43% in DM) and protein level (from 14% CP to 16% CP
of DM) by introducing soybean groats (5.5% of DM), positively
influenced the quantitive and qualitative productio n of milk and, in
particular, the profile of fatty acids. This way, t he average daily
production of milk increased up to 14.7% (p ≤ 0.05) and, also, fat
content, protein and lactose content increased, but decreased the casein
content (which could reduce the performance of proc essing milk in
cheese) and non protein nitrogen.
2. Sheep fed the high energy diets to have lower ac etate and higher butyrate
molar proportion before feeding than those fed the low energy diets.
After feeding, ewes fed the high energy and protein diets had higher
proportion of propionate and lower proportion of ac etate and
acetate/propionate ratio than those fed the low ene rgy and protein diets.
Sheep fed the high energy and high protein diets ha d lower NH 3CN in
ruminal fluid, than those fed the low diets (p ≤ 0, 05).

Acknowledgments
Financial support for this research the Ministery o f Education and
Research, Romania, is gratefully acknowledged – CNC SIS, PN II project,
ID_679, no. 1082/2008.

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