Livestock Research for Rural Development 20 (4) 2008 Guide for preparation of papers LRRD News

Citation of this paper

In vitro and in sacco ruminal protein degradability of common Indian feed ingredients

G Mondal, T K Walli and A K Patra*

Dairy Cattle Nutrition Division, National Dairy Research Institute, Karnal, Haryana, 132001, India
goutam_mondal@rediffmail.com
*Department of Animal Nutrition, West Bengal University of Animal and Fishery Sciences, Kolkata 700037, WB, India
akpatra75@rediffmail.com

Abstract

Protein degradability by in sacco method and protein fractionation by laboratory analysis using CNCP (Cornell Net Carbohydrate and Protein) system was determined to develop a prediction equation for predicting degradability from different protein fractions.

 

Sixteen different types of feeds namely, maize grain (MZ), maize gluten meal (MGM), maize fibre (MF), maize oil cake (MOC), wheat (WT), wheat bran (WB), barley (BRL), soybean meal (SBM), sunflower meal (SFM), deoiled coconut cake (DCC), cottonseed cake (CSC), groundnut cake (GNC), mustard cake (MC), fish meal (FM), guar chuni (GC) and subabul leaves (LLM) were analysed for (A+B1), B2, B3 and C. The above feeds were also incubated in the rumen of three fistulated, adult crossbred cattle to estimate the effective protein degradability (EPD) of individual feeds. A linear regression equation was drawn for EPD from different protein fractions.

 

Higher A+B1 fraction was observed in MC, GNC and BRL, whereas lower values were noted in MGM, MF and MZ. B2 fraction was highest in MF followed by MZ and LLM and lower values were found in GNC, MC and SBM. B3 fraction was greater in MGM, FM and CSC, whereas the lower values were noted in MC, LLM and MF. Lignin bound nitrogen or C fraction was greater in MGM, GC and LLM and with lower values in BRL, WT, WB, MF and MZ. Higher EPD was found in MC, GNC followed by BRL, MOC and WB, whereas lower values were obtained in MGM, MF, LLM and CSC.

 

ECPD at different outflow rates were highly and positively correlated (r = 0.84 to 0.88) with (A+B1) fraction, whereas with B2, B3 and C it was negatively associated (r = 0.55 to 0.62, 0.29 to 0.32 and 0.50 to 0.52 for B2, B3 and C, respectively).

 

Significant predicted variables in stepwise regression included (A+B1), (A+B1)2 and B32 at fractional outflow rate of 0.02 h-1 with R2 value of 0.90. However, the predicted equations at fractional outflow rate of 0.04 and 0.06 h-1 contained (A+B1), (A+B1)2, B3, B32 and C2 predictive variables with high degree of prediction (R2 = 0.93). B3 alone was weak predictor for UDP content of feeds.

 

Therefore, to avoid the maintenance of fistulated animals and to save time for in sacco experiment, laboratory analysis of protein fractions and fitting them in the regression equation may predict the EPD values effectively.  

Key words: Indian feeds, prediction equation, protein degradability, protein fractions


Introduction

The rate and extent of protein degradability of different feed ingredients varies considerably with protein source and animal species, which ultimately determines the incorporation of feed ingredients in the diets of ruminants.(Kandylis and Nikokyris 1999, Bach et al 2005) It is suggested that there should be enough soluble readily fermentable protein to support microbial growth and fermentation in the rumen for optimum utilization of roughages, and a source of less fermentable protein, which can pass directly to the abomasum and small intestine for a normal proteolytic digestion and absorption process for optimal performance in high-producing ruminants (Tamminga 1979, Broderic et al 1991, Mathis et al 2000). Therefore, information of protein degradability of various feedstuffs that are available locally is needed for formulation of diets using these feeds.

 

The degradability can be measured by in vivo methods (Chaturvedi and Walli 1995) and in vitro methods (Walli et al 2000). In vitro methods are quicker for screening of large number of feeds but do not give protein degradability in absolute terms. In sacco method is widely accepted to measure the degradability, which is analysed by a computer model developed by Orskov and McDonald (1979). But result obtained may differ depending on bag pore size, fineness of grinding, sample size, sample size to bag surface ratio, position of the bag in the rumen, microbial population/ contamination of bag residues and incubation time (Micchalet- Doreau and Bah 1993, Nocek 1988, Stern et al 1997). To avoid these problems and maintaining fistulated animals for the in sacco studies, Chalupa and Sniffen (1996) proposed partitioning of protein by subjecting the feeds to digestion in different solvents/ detergents based on Cornell Net Carbohydrate and Protein (CNCP) model. Database for different protein fractions have been estimated from a number of feedstuffs (Sharma and Singh 1997a) and for formaldehyde treated groundnut cake and mustard cake at three different levels (Chatterjee 1998). The present study was conducted to determine in vitro and in vivo degradability of some common Indian feed ingredients, and to develop prediction equations for effective protein degradability on the basis of different protein fractions.

 

Materials and methods 

Sixteen common feedstuffs viz., maize grain (MZ), maize gluten meal (MGM), maize fibre (MF), maize oil cake (MOC), wheat (WT), wheat bran (WB), barley (BRL), soybean meal (SBM), sunflower meal (SFM), deoiled coconut cake (DCC), cottonseed cake (CSC), groundnut cake (GNC), mustard cake (MC), fish meal (FM), guar churi (GC) were procured from local market near by Karnal region of Haryana, India and subabul leaves (LLM) were collected from trees planted around the fodder farm of the Institute. All the samples were ground to pass 2.5 mm sieve size and N content was estimated by Kjeldahl’s method (AOAC 1984). In sacco study was conducted on three fistulated adult male crossbred cattle, kept on a constant diet of concentrate to roughage (35:65) as per NRC (1989) to meet their maintenance requirement. Pre-weighed nylon bags (Nocek 1988) containing 5 g of milled samples were placed inside the rumen of each animals. The samples were taken out at 3, 6, 12, 36, and 48 h interval and thoroughly washed and bags were dried in an oven first at low temperature (60 ºC) and then at higher temperature (90oC) to determine DM and N loss in rumen. Dry and protein disappearance data were fitted to the model of Orskov and McDonald (1979) to estimate  the kinetics of degradability of DM and CP such as a, b and c.  

 

Y= a+b(1-exp-ct)

where,

a = rapidly degradable fraction,

b = insoluble but potentially degradable fraction,

c = rate of degradation

 

The effective degradability (P) of DM and CP was calculated using the equation shown below, using rumen fractional outflow rates (r) of 0.02 and 0.04 and 0.06 h-1

P = a + [(bxc)/(c+r)]

 

Fractionation of protein was done as per Chalupa and Sniffen (1996). Accordingly, different protein fractions were calculated:

 

(A + B1):  Corresponds to non-protein nitrogen and rapidly degradable true proteins (all globulin and some albumin). This fraction is soluble in phosphate buffer.

 

B2 :  (PBIN - NDIN) is rest of albumin and all glutelins. This true protein have intermediate degradation rate.

 

B3 : (NDIN - ADIN) is prolamins, extension proteins and denatured protein, and is slowly degradable.

 

C : It is derived from acid detergent insoluble nitrogen (ADIN). This fraction corresponds to Maillard products and N bound to lignin. 

Statistical analysis 

One-way analysis of variance (ANOVA) using SPSS (2001) was carried out to compare the data of in sacco degradability values, RDP and UDP content, and different N fractions of feeds. The significance among the individual means was identified using Tukey’s multiple range test. Simple Pearson correlation between effective degradability of CP and different N fractions of feeds estimated using SPSS (2001). Stepwise multiple regression procedure of SPSS (2001) was conducted to predict the effective crude protein degradability (ECPD) from different N fractions with their quadratic terms included for the model development.

 

Results and discussion  

In sacco degradability of DM and CP

 

Degradation constants (a, b and c), potential and effective degradability for DM at different rumen fractional outflow rates is shown in Table 1.


Table 1.  Dry matter degradation kinetics and effective dry matter degradability (EDMD) of different feeds

Ingredients

a

b

c

EDMD at outflow rate, h-1

0.02

0.04

0.06

Mustard cake

68.38k

31.62a

0.033abc

88.10i

82.73g

79.66g

Groundnut cake

46.41j

42.36a

0.091ef

81.26hi

75.90fg

71.98fg

Barley grain

40.39ij

44.86a

0.069de

72.83fgh

66.87def

62.76ef

Maize oil cake

1.98a

98.01f

0.052cd

72.61fgh

57.23cd

47.36c

Wheat bran

28.99fg

59.74bc

0.072de

75.77gh

67.47ef

61.68e

Wheat

11.02bcd

83.55e

0.097f

80.61hi

70.45ef

62.88ef

Deoiled coconut cake

30.22gh

69.77cd

0.021ab

65.52def

54.05c

48.26cd

Guar chuni

21.31ef

64.80bcd

0.067de

72.75fgh

63.14cde

56.56cde

Sunflower meal

37.76hi

35.49a

0.042bc

61.57cde

55.71c

52.18cd

Soybean meal

25.94fg

55.82b

0.112f

73.15fgh

66.85def

62.03e

Fish meal

8.16abc

56.66b

0.055cd

49.69b

40.94b

35.23b

Maize grain

15.30cde

64.26bc

0.027ab

52.12bc

41.13b

35.19b

Cotton seed cake

38.91ij

61.08bc

0.014a

63.92def

54.69c

50.44cd

Leucaena leaf meal

17.17de

56.19b

0.143g

66.47efg

61.08cde

56.76de

Maize fiber

3.21ab

96.78f

0.024ab

55.78bcd

39.34b

30.74b

Maize gluten meal

5.81ab

77.80de

0.012a

34.85a

23.69a

18.73a

SE

2.16

3.41

0.0067

2.69

2.62

2.50

a, b and c are constants of the exponential equation [P= a+b (1-e-ct)] where ‘a’ is the rapidly degradable fraction, b the slowly degradable fraction and ‘c’ the rate of degradation of fraction ‘b’, EDMD: effective degradability of DM.

a-kLetters with different superscripts within a column differ significantly (P < 0.05)


Rapidly degradable fraction (a) was greatest in MC, with intermediate values in GNC, BRL, CSC, WB, DCC, SFM and SBM. Other feeds had low ‘a’ values. Potential degradable fraction (b) was higher in MOC, MF, WT and MGM; intermediate values in DCC, GC, MZ, CSC, WB, FM, LLM and SBM and lower values in BRL, GNC, SFM and MC. Rate of degradation (c) of DM was higher in LLM, SBM, WT and GNC, whereas the lower values were obtained in MGM, CSC, DCC, MF, MZ and MC. EDMD at different rumen fractional outflow rate was lower in MGM followed by FM, MZ and MF, and was higher in MC, GNC and WT.

 

Degradation constants and effective degradability of CP is shown in Table 2.


Table 2.  Crude protein degradation kinetics and effective protein degradability (EPD) of different feeds

Ingredients

a

b

c

ECPD at outflow rate, h-1

0.02

0.04

0.06

Mustard cake

46.40j

57.72a

0.060defg

84.78fg

76.87g

71.77f

Groundnut cake

26.98gh

70.38e

0.107i

86.28g

78.21g

72.08f

Barley grain

22.51fg

72.26ef

0.104i

83.10efg

74.68fg

68.32f

Maize oil cake

13.54cd

82.86gh

0.075gh

78.96def

67.58ef

59.57e

Wheat bran

12.91cd

78.48fg

0.090hi

77.08de

67.18e

59.94e

Wheat

10.00bc

89.99ij

0.064efg

78.54def

65.35de

56.42e

Deoiled coconut cake

22.45fg

77.54fg

0.049def

77.50de

65.13de

57.30e

Guar chuni

21.53f

67.60cde

0.068fgh

73.75cd

64.07de

57.42e

Sunflower meal

38.18i

61.81bcd

0.025abc

72.38cd

61.86de

56.29e

Soybean meal

23.04fg

60.95bc

0.058defg

68.21c

58.94d

52.83e

Fish meal

20.06ef

57.62ab

0.045cde

59.94b

50.56c

44.75d

Maize grain

31.50h

68.49de

0.012a

57.14b

47.28bc

42.90cd

Cotton seed cake

16.73de

83.26ghi

0.022ab

60.33b

46.27bc

39.07bcd

Leucaena leaf meal

6.03b

78.52fg

0.038bcd

57.63b

44.39bc

36.56bc

Maize fiber

7.71b

92.28j

0.023abc

57.01b

41.36b

33.26b

Maize gluten meal

0.13a

87.23hij

0.011a

30.94a

18.88a

13.60a

SE

1.23

1.85

0.0060

1.83

1.96

1.95

a, b and c are constants of the exponential equation [P= a+b (1-e-ct)] where ‘a’ is the rapidly degradable fraction, b the slowly degradable fraction and ‘c’ the rate of degradation of fraction ‘b’, ECPD: Effective degradability of crude protein.
Letters with different superscripts within a column differ significantly (P < 0.05)


The values of ‘a’ for CP were high in MC, SFM, MZ and GNC followed by in SBM, DCC, BRL, GC and FM, and was low in other feeds. Potential degradability (b) of CP was greater in MF, WT, MGM, CSC, MOC, LLM, WB and DCC, whereas low values were obtained in FM, MC, SBM and SFM. Rate of degradation for CP was higher in GNC, BRL, MOC and WB, and was lower in MGM, MZ, CSC, MF and SFM. The ECPD values ranked MGM < MF = LMM = CSC = MZ = FM < SBM ≤ SFM = GC ≤ DCC = WB ≤ WT = MOC ≤ BRL ≤ MC ≤ GNC at fractional outflow rate of 0.02 h-1. Same trend also followed in other rumen outflow rates. Out of 16 feeds, most of these viz., MOC, SFM, SBM, BRL, WT, WB, DCC, GC, GNC, MC had high (> 55%) ECPD at fractional outflow rate of 0.04 h-1.

 

Murphy and Kenelly (1987), Walli et al (1991) and Woods et al (2002) observed similar trend in ECPD value for BRL, whereas Mustafa et al (1998) reported lower ECPD value, which may be due to difference in milling of the grain. Zerbini and Polan (1985) and Sharma and Singh (1997b), Murphy and Kennelly (1987), Walli et al (1991) and Haldar and Rai (2002) reported a different value for MZ. For CSC, Sharma and Singh (1997b) reported a similar value, but Walli et al (1991) reported a lower value and Zerbini and Polan (1985) and Haldar and Rai (2002) reported a higher value of ECPD. Ha and Kennelly (1984), Zerbini and Polan (1985) reported a lower ECPD value for FM, whereas Siddons et al (1985) reported a higher and Woods et al (2002) observed a similar ECPD value for FM. This may be due to type of fish used for preparation of meal and processing of the feed. In case of SBM, Ha and Kennelly (1984) and Walli et al (2000) reported a little difference in EPD value, but Santos et al (1984), Zerbini and Polan (1985) and Woods et al (2002) reported a higher EPD value. In case of SFM, Sharma and Singh (1997b) and Woods et al (2002) observed a higher ECPD value for SFM. For WB, Walli et al (1991) and Sharma and Singh (1997b) reported a similar ECPD value however, Haldar and Rai (2002) observed a different EPD value. LLM, which is also a high protein source, had the similar EPD value as reported by Sampath et al (1989). ECPD of GNC was similar as reported by Haldar and Rai (2002) but for MC they reported a lower value.

 

UDP content of feeds

 

UDP values were calculated from ECPD at different rumen outflow rates for each feed and presented in Table 3.


Table 3.  Crude protein (CP) and rumen undegradable protein content (RUP, % DM basis) of some common feeds at
different rumen fractional outflow rates

Ingredients

 

CP

UDP at rumen outflow rates

0.02

0.04

0.06

Mustard cake

1

33.18de

5.12bc

7.76cd

9.45de

Groundnut cake

2

43.19f

5.92c

9.40d

12.06e

Barley grain

3

10.25a

1.73a

2.60a

3.26a

Maize oil cake

4

21.00b

4.42abc

6.80cd

8.49cde

Wheat bran

5

13.56a

3.12abc

4.46abc

5.45abc

Wheat

6

8.94a

1.92ab

3.11ab

3.91ab

Deoiled coconut cake

7

25.50bc

5.74c

8.89d

10.89e

Guar chuni

8

55.12h

14.46ef

19.79gh

23.45hi

Sunflower meal

9

36.31e

10.04d

13.86e

15.88f

Soybean meal

10

54.81h

17.44fg

22.51hi

25.85ij

Fish meal

11

49.06g

19.66g

24.27i

27.12j

Maize grain

12

12.56a

5.36c

6.60bcd

7.15bcd

Cotton seed cake

13

29.19cd

11.58de

15.69ef

17.79fg

Leucaena leaf meal

14

32.87de

13.92e

18.28fg

20.85gh

Maize fiber

15

10.12a

4.36abc

5.95abcd

6.76abcd

Maize gluten meal

16

70.31i

48.56h

57.04j

60.75k

SE

 

1.305

0.894

0.956

0.990


Although UDP content (%DM) differed depending upon the rumen outflow rates, it was greatest in MGM, followed by moderate quantity in FM, SBM, GC, LLM, SFM and CSC, low quantity in DCC, GNC, MC, MOC and MZ. UDP content was lowest in BRL, WT and WB. Haldar and Rai (2002) reported a similar UDP value for GNC and WB whereas different value for MZ, CSC, MC and MGM. On the basis of UDP values, it may be suggested that MGM, FM, SBM, GC, CSC and LLM are good source of naturally occurring bypass protein.

 

Fractions of protein in different feeds

 

Crude protein is the heterogeneous mixture of true protein and NPN. The protein fractions in the feed affect both ruminal degradability and digestion of undegradable protein in the small intestine. A method of partitioning proteins by subjecting feeds in different solvents and detergents have been developed by Chalupa and Sniffen (1996). Results of different protein fractions are shown in Table 4.


Table 4.  N solubility and protein fractions in different feeds (% of total N)

Ingredients

PBSN (A+B1)

PBIN

NDIN

B2

B3

ADIN (C)

Mustard cake

76.24i

23.76a

13.19a

10.57b

9.96a

3.23ab

Groundnut cake

74.15i

25.85a

20.50cd

5.35a

15.33b

5.17abcde

Barley grain

51.35h

48.65b

36.49gh

12.16bc

32.31fg

4.18abcd

Maize oil cake

35.61de

64.39ef

26.79ef

37.60i

20.81c

5.98bcdef

Wheat bran

46.51gh

53.49bc

23.39de

30.10gh

20.32c

3.07a

Wheat

37.80def

62.20def

31.76fg

30.44h

27.59de

4.17abcd

Deoiled coconut cake

43.80fg

56.20cd

43.27ij

12.93bc

38.18hi

5.09abcde

Guar chuni

46.41gh

53.59bc

32.82gh

20.77def

25.27d

7.55ef

Sunflower meal

37.71def

62.29def

36.95h

25.34fg

31.13ef

5.82abcde

Soybean meal

41.61efg

58.39cde

42.49i

15.90cd

35.70gh

6.79def

Fish meal

27.82bc

72.18gh

47.82j

24.36ef

44.32jk

3.50abc

Maize grain

23.72b

76.28h

18.75bcd

57.50j

14.78b

3.97abcd

Cotton seed cake

32.10d

67.90fg

47.82j

20.08de

41.49ij

6.33cdef

Leucaena leaf meal

25.41bc

74.59gh

17.55abc

57.04j

9.97a

7.58ef

Maize fiber

20.41b

79.59h

14.83ab

64.76k

8.91a

5.92abcdef

Maize gluten meal

11.65a

88.35i

54.95k

33.40hi

46.17k

8.78f

SE

2.03

2.03

1.40

1.34

1.19

0.77

PBSN, phosphate buffer soluble nitrogen; PBIN, phosphate buffer insoluble nitrogen; NDIN, neutral detergent insoluble nitrogen; B2, (PBIN - NDIN); C, corresponds to acid detergent insoluble nitrogen (ADIN); B3, (NDIN - ADIN)

SE, standard error


The lower values (percent of CP) for PBSN or A+B1 fraction was in MGM followed by MF and the greater values were in MC, GNC and BRL. NDIN content was greater in MGM, CSC, DCC, FM and SBM, was and lower in MC, LLM and MF. ADIN was highest in MGM followed by LLM and GC, whereas the lowest ADIN value was obtained in WB followed by MC and FM. (A+B1) represents PBSN portion, which is highly degradable in rumen and B2 fraction is 5-15% degradable whereas B3 is only 0.1-1.5% degradable, and C is the fraction that is neither degraded in rumen nor digested in lower tract, and this represents the ADIN portion of the feed. B2 fraction was higher in MF, MZ, LLM, and was lower in GNC, MC, BRL, DCC and SBM. B3 portion was greater in MGM, FM, CSC and DCC, whereas the lower B2 value was noted in MF, MC and LLM. Results of N solubility and protein fractions in some of the feeds are somewhat different than those obtained by Sharma and Singh (1997a) and Chatterjee (1998) which may be due to variation in feed sources, as composition could vary from region to region or from time to time, depending on soil type, fertilization as well as plant variety and the method of processing.

 

Prediction equation for EPD based on different protein fractions

 

Correlation coefficient (r) of ECPD at different fractional rumen outflow rates with (A+B1), B2, B3, and C are presented in Table 5.


Table 5.   Pearson correlation between effective crude protein degradability (ECPD) at different outflow rates (0.02 to  0.06) and different protein fractions

 

ECPD0.02

ECPD0.04

ECPD0.06

A + B1

B2

B3

C

ECPD0.02

1

0.99**

0.98**

0.84**

-0.55**

-0.32*

-0.50**

ECPD0.04

 

1

1**

0.87**

-0.60**

-0.29*

-0.51**

ECPD0.06

 

 

1

0.88**

-0.62**

-0.29*

-0.52**

A + B1

 

 

 

1

-0.72**

-0.30*

-0.41**

B2

 

 

 

 

1

-0.43**

0.17

B3

 

 

 

 

 

1

0.20

C

 

 

 

 

 

 

1

A+B1, phosphate buffer soluble nitrogen; B2, [phosphate buffer insoluble nitrogen (PBIN) - neutral detergent insoluble nitrogen (NDIN)]; C, corresponds to acid detergent insoluble nitrogen (ADIN); B3, (NDIN - ADIN)

**Correlation is significant at the 0.01 level.

*Correlation is significant at the 0.05 level.


ECPD values were highly and positively correlated with (A+B1) fraction, whereas with B2 and C it was negatively associated with intermediate correlation. ECPD and B3 was also negatively correlated with low value of r. The prediction equations to determine in sacco ECPD using different protein fractions is shown in Table 6.           


Table 6.  Stepwise regressions to predict the effective protein degradability from different protein fractions

Dependent variables

Intercept or independent  variables

Parameter estimate

SE

P Value

Model R2

RMSE

ECPD0.02

Intercept

19.07

3.81

<0.001

0.90

4.68

 

(A+B1)

2.10

0.170

<0.001

 

 

 

(A+B1)2

-0.016

0.002

<0.001

 

 

 

B32

-0.004

0.001

0.001

 

 

ECPD0.04

Intercept

10.41

4.28

0.019

0.93

4.28

 

(A+B1)

1.43

0.286

<0.001

 

 

 

(A+B1)2

-0.009

0.003

0.004

 

 

 

B3

1.18

0.460

0.014

 

 

 

B32

-0.024

0.008

0.006

 

 

 

C2

-0.104

0.036

0.006

 

 

ECPD0.06

Intercept

5.93

4.16

0.16

0.93

4.16

 

(A+B1)

1.210

0.277

<0.001

 

 

 

(A+B1)2

-0.006

0.003

0.032

 

 

 

B3

1.348

0.447

0.002

 

 

 

B32

-0.027

0.008

0.002

 

 

 

C2

-0.115

0.035

0.004

 

 

ECPD0.02-0.06: effective crude protein degradability at outflow rate of 0.02 to 0.06; SE: standard error; RMSE: root means square error.

A + B1: phosphate buffer soluble nitrogen; C: acid detergent insoluble nitrogen (ADIN); B3, (neutral detergent insoluble nitrogen - ADIN)


Significant predicted variables in stepwise regression included (A+B1), (A+B1)2 and B32 at fractional outflow rate of 0.02 h-1 with R2 value of 0.90. However, the predicted equations at fractional outflow rate of 0.04 and 0.06 h-1 contained (A+B1), (A+B1)2, B3, B32 and C2 predictive variables with high degree of prediction. Stepwise regression did not include B2 protein fractions of feeds. Therefore, it seems that (A+B1), B3, and C fraction of feeds are most important in predicting ECPD. When slowly degradable protein fraction (B3) was used to predict the UDP content of feeds, B3 predicted the UDP content moderately (Figure 1).


Figure 1. Prediction of UDP content (% of CP) of feeds from B3 (% of CP). When all the data included, the prediction equation () was UDP (%CP) = 75.53 - 3.71 x B3 + 0.076 x B32, R2 = 0.49. However, when some data () was excluded, the prediction equation () was UDP (%CP) = 12.76 + 0.0826 x B3, R2 = 0.86


However, when the UDP data of some feeds was not included to develop prediction equation from B3, equation gave high degree of prediction (R2 = 0.86). Some of the characteristics of these feeds when not included predicting UDP from B3 highly is having high fiber content and/or high B2 content. B2 protein fraction of feeds is partially digested and thus may contribute to UDP content of feeds. This might be one reason of low prediction of UDP from B3 when all the data were included. Sharma and Singh (1997b) reported a high R2 value for the prediction equation involving ECPD and all the protein fractions of the feed. Similarly Chatterjee and Walli (2002) reported a high R2 value for the prediction equation with respect to formaldehyde treated mustard cake and groundnut cake at four different levels.

 

Conclusions

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Received 30 October 2007; Accepted 13 December 2007; Published 4 April 2008

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