Livestock Research for Rural Development 19 (11) 2007 Guide for preparation of papers LRRD News

Citation of this paper

Effect of varying levels of concentrate supplementation on growth performance and carcass traits of finisher lambs

S A Karim, M K Tripathi* and V K Singh

Central Sheep and Wool Research Institute, Avikanagar (via-Jaipur)
Rajasthan, 304 501 India
mktirpathi@gmail.com

Abstract

The slaughter study was conducted on finisher lambs drawn from a growth trial on weaner lambs maintained on grazing with concentrate supplementation of 1.5 (C1.5) and 2.5 % (C2.5) of body weight and ad-libitum concentrate (C-AL) in cafeteria system of feeding management of 90 days duration during active phase of growth to assess their carcass traits.

 

Weaning weight was similar in the three groups (13.9 kg) while the finishing weight was higher (P<0.01) in C-AL (27.2 kg) than C2.5 (23.2 kg) and C1.5 (20.9 kg). Level of concentrate feeding improved daily gain and feed efficiency. The empty live weight, hot carcass weight and weight of edible offals of the 3 groups also followed trend similar to that of pre slaughter weight. The dressing yield, both in terms of pre slaughter weight as well as empty live weight, although statistically similar in the three groups. The dressing yield inclusive of edible offals in terms of empty live weight (ELW) was however significantly (P<0.05) higher in C-AL than C1.5 and C2.5. The total edible and inedible offal yield as % of pre slaughter weight (PSW) was similar in the three groups (4.79 and 34.67 % of PSW). The cut weights of the primal cuts were higher in C2.5 and C-AL than C1.5 whereas as % of PSW the cut proportions were similar in 3 groups excepting leg cut which was similar in C2.5 and C-AL and significantly (P<0.01) higher in C1.5. The chilling loss % was higher in loin and rack than other primal cuts with an average of 2.7 % chilling loss of the half carcass. The lean content of primal cuts was similar in the three groups while the loin fat content was 10.3 % in C1.5, which increased (P<0.05) to 14.1 and 19.5 %, respectively in C2.5 and C-AL.

 

It is concluded that the growth performance was better under cafeteria system of feeding management than grazing with 1.5 or 2.5 % of body weight as concentrate supplementation. Moreover under cafeteria system of feeding management the feed conversion efficiency improved while half carcass fat content remained well within limit (9 %) providing a carcass of desired quality thus rendering the production system suitable for commercial application. Better performance of C-AL lambs was the reflection of higher concentrate intake, however higher feed cost per kg meat was incurred.

Key words: carcass traits, concentrate supplementation, growth, lambs


Introduction

Under the existing land utilization in the country sheep are traditionally reared on grazing with top feed supplementation during critical summer months. The male lambs in farmers flock surplus to the breeding requirement are disposed off for slaughter at 9- 12 months of age weighing 22 kg (Karim 2004) with average carcass weight of 10- 11 kg (Kondaiah and Agnihotri 1995). The male lambs under field condition have poor growth rate and in active phase of growth (3- 6 months) attain 60- 70 g average daily gain (Kaushish et al. 1990) while these native lambs under intensive feeding management are able to attain 150 g average daily gain (Karim and Rawat 1996) indicating that the feeding management has to be optimized for enhancing mutton production.

 

Carcass evaluation is essential for growth studies to determine relative efficiency of finisher lambs in converting feed to animal tissue. The slaughter traits, in turn are modulated by heredity, feeding regimen and prevailing rearing environment. It is however realized that for practical meat disposal in the country, the western concept of meat grading is not practiced as different primal cuts do not fetch variable market prices. Indian consumers usually prefer meat with desired fat content (12- 15 %) whereas fat content exceeding 20 % is not liked by the locals. Moreover higher fat deposition in the carcass reduces the feed conversion efficiency thus increasing the cost of feed input/kg gain in live weight and hence is uneconomical. A series of slaughter studies conducted at the station on finisher lambs drawn from breeding and feeding experiments indicated that the native lambs in farmers flock have dressing yield (Ratio of hot carcass weight to pre slaughter weight) of 40 % which increased to 50 % under organized feeding management (CSWRI 1998). Moreover the dressing percentage was generally higher in lambs maintained under high level of feeding than their range managed/low plane fed counterparts (Katiyar et al. 1974; Krishnamohan and Chryalu 1983; Sen et al. 2000).

 

The reported slaughter study was conducted on finisher lambs drawn from a growth trial on weaner lambs maintained on grazing with varying level of concentrate supplementation and cafeteria system of feeding management to assess their carcass traits.
 

 

Materials and methods

 

Sixty weaner (About three months old) were adopted from a local farmer adopted under Jaivigyan Project. The lambs were dewormed and vaccinated against enterotoxaemia and divided into 3 equal groups. The lambs were maintained in groups in separate enclosures under a side open asbestos roofed animal shed for further 90 days. They were fed under cafeteria system of feeding management and offered ad lib. roughage (Prosopis cineraria and Albizia lebbeck leaves in ratio of 50: 50) in feeding troughs during morning hours. Residue, if any, of the previous day was weighed and discarded the next day before fresh feed offer. Besides ad lib. roughage the C1.5 and C2.5 lambs were offered concentrate (Maize 29, GN cake 30, wheat bran 20, de oiled rice bran 18, mineral mixture 2 and common salt 1 parts) of1.5 and 2.5 % of body weight, respectively while the C-AL lambs were maintained under cafeteria system of feeding management with free choice concentrate and roughage in separate containers. The feeding experiment continued for 90 days followed by a slaughter study on 6 finisher lambs from each group to assess carcass traits.

 

The lambs were fasted for 18 hrs with free access to water and slaughtered as per the standard procedures by Halal method. Carcass, edible (Testicle, spleen, pancreas, mesenteric fat, caul fat, kidney fat, kidney, heart, liver) and non edible (Head, skin, fore and hind canons, lungs with trachea, gall bladder, penis, empty GI tract) offal weights were recorded immediately after slaughter. Lungs, trachea and heart were weighed as one piece and designated as pluck. Weight of ingesta was determined as the difference between full and empty digestive tract. The empty live weight was computed as the difference between pre slaughter weight and weight of digestive content. The hot carcass was then split to fore and hind quarters. The fore and hind quarters were further split along the mid line and the left half was disjointed as per ISI (1963) specifications to standard cuts viz. leg, loin, rack, neck and shoulder and breast and fore shank. The cuts were chilled over night at 4C and the next day the cuts were dissected into lean, fat and bone which was expressed as proportion of chilled weight of the various cuts. The dissected bones of different cuts were boiled for 15 mins in 2 % KOH solution and KOH bone content was determined. Loin eye area (cm2) was recorded on the cut surface of Longissimus dorsi muscle at the interface of 12th and 13th ribs on both the sides of the carcass.

 

The data generated in the experiment were subjected to analysis of variance and significant group differences were compared using SPSS 10 package.
 

 

Results and discussion

 

Weaning weight was similar in the three groups (13.9 kg) while the finishing weight was higher (P<0.01) in C-AL (27.2 kg) than C2.5 (23.2 kg) and C1.5 (20.9 kg), similar trend was for average daily gain and feed efficiency (Figure 1).


               


Figure 1
.  Effect of level of concentrate feeding (C1.5, 1.5 % of LW; C2.5, 1.5 % of LW; C-AL, ad-libitum)
on average daily gain (ADG) and feed efficiency (%, g gain/ 100g feed intake)


Initial live weight of lambs were similar but concentrate supplementation significantly increased gain and feed conversion ration with increase in concentrate supplementation (Table 1)


Table 1.  Effect of concentrate level on growth and feed efficiency of lambs

 

C1.5

C2.5

C-AL

SEM

P value

Body weight, kg

 

 

 

 

 

Initial

13.8

14.3

13.5

0.649

0.690

Finishing

20.9a

23.2a

27.2b

1.118

0.001

Daily gain, g/day

78.9

98.9

152

7.4

 

Total gain, kg

7.1a

8.9a

13.7b

0.665

<0.001

Feed intake, kg/day

 

 

 

 

 

    Roughage

44.5

41.8

14.2

 

 

    Concentrate

20.7

33.9

79.0

 

 

     Total

65.2b

75.7a

93.2a

7.203

0.036

R/C Ratio

2.15c

1.23b

0.18a

 

 

Feed conversion ratio, kg feed / kg gain

9.2b

8.5b

6.8a

0.427

0.001


Higher growth rate in high concentrate fed lambs was due to better plane of nutrition which was also observed by Santra et al. (2002). The results indicated that farmer’s weaner lambs have higher growth potential under cafeteria system of feeding management than those reported for the genotype maintained under extensive range management (Kaushish et al. 1990).

 

The pre slaughter weight reflected the trends of finishing weight of the three groups which was also higher (P<0.01) in C-AL followed by C2.5 and C1.5, in that order (Table 2).


Table 2.  Carcass characteristics of finisher lambs maintained on varying level of concentrate supplementation during post weaning phase of growth

Traits

C1.5

C2.5

C-AL

Pooled

Pre slaughter weight, kg**

19.5A0.27

23.5B0.94

26.5C0.80

23.20.80

Empty live weight, kg**

17.2 A 0.19

20.6 B 0.64

23.5 C 0.66

20.40.69

Hot carcass weight, kg**

9.2 A 0.18

11.0 B 0.35

13.0 C 0.44

11.10.43

Weight of edible offal, kg**

0.91A 0.026

1.13 B 0.049

1.34 C 0.088

1.130.054

Dressing % on live weight

46.971.051

46.650.719

49.201.026

47.610.581

Dressing % on ELW

53.341.030

53.110.568

55.550.666

54.000.500

Dressing yield with edible offal as % PSW

51.631.129

51.470.790

54.251.028

52.450.621

Dressing yield with edible offal as % ELW*

58.63a1.094

58.59 a .509

61.25b0.662

59.490.526

Weight of fore quarter, kg**

4.91 A 0.098

5.95 B 0.193

7.10 C 0.257

5.990.241

Fore quarter as % of hot carcass weight

53.59 0.256

54.300.218

54.46 0.392

54.120.186

Weight of hind quarter, kg**

4.25 A 0.084

5.01 B 0.163

5.93 C 0. 191

5.060.186

Hind quarter as % of hot carcass weight

46.410.256

45.700.218

45.540.392

45.880.186

Loin eye area, cm2

12.20.18

13.60.75

12.50.73

12.80.44

*P<0.05; **P<0.01


The empty live weight, hot carcass weight and weight of edible offals of the 3 groups also followed trend similar to that of pre slaughter weight. The dressing yield, both in terms of pre slaughter weight as well as empty live weight, although statistically similar in the three groups, was generally higher in C-AL than other two groups. The dressing yield inclusive of edible offals in terms of empty live weight (ELW) was however significantly (P<0.05) higher in C-AL than C1.5 and C2.5. The range of dressing yield of the lambs observed in the study was similar to earlier reports on Indian sheep (Karim and Rawat 1997; Karim et al. 2002; Sen et al. 2004). The loin eye area as index of muscle growth was similar in the three groups (12.8 cm2) indicating that tissue accretion of even C1.5 was optimum for the genotype.

 

Edible organ weight, kidney fat and caul fat content was generally higher in high concentrate fed groups which was reflected in higher (P<0.01) total edible offal weight in C-AL followed by C2.5 and C1.5 in that order (Table 3).


Table 3.  Organoleptic traits of the slaughtered lambs (% of pre slaughter weight)

Traits

C1.5

C2.5

C-AL

Pooled

Edible offal

Testicle

0.530.070

0.610.072

0.650.123

0.600.051

Spleen

0.210.025

0.240.038

0.200.017

0.220.015

Pancreas

0.160.012

0.130.024

0.100.005

0.130.009

Caul fat

0.650.194

0.650.035

0.960.116

0.750.079

Kidney fat

0.280.039

0.420.053

0.520.069

0.410.038

Kidney

0.380.016

0.300.023

0.310.010

0.330.013

Heart

0.4910.022

0.460.018

0.430.016

0.460.011

Liver

1.910.057

1.970.059

1.820.076

1.900.038

Total edible offal weight, kg**

0.90 A 0.026

1.12B0.049

1.33C0.087

1.110.053

Total edible offal as % of PSW

4.61 0.130

4.77 0.195

4.990.218

4.790.107

Inedible offal

 

 

 

 

Blood

4.320.183

4.920.149

4.550.2356

4.600.121

Head **

7.27C0.075

6.76B0.197

6.30A0.135

6.780.124

Shorn skin **

8.87A0.260

8.45A0.195

10.03B0.519

9.110.251

Fore canon with hooves

1.640.056

1.510.047

1.520.24

1.560.028

Hind canon with hooves**

1.39B0.047

1.22A0.029

1.20A0.023

1.270.028

Lungs with trachea

2.300.163

2.060.077

2.240.074

2.200.066

Gall bladder **

0.08B0.006

0.04A0.011

0.03A0.004

0.050.006

Penis

0.020.001

0.020.001

0.020.001

0.020.001

GI tract empty ** 

8.97AB0.338

9.63B0.211

8.32A0.176

8.970.189

Total inedible offal weight, kg**

6.82 A 0.167

8.16 B 0.241

9.07 C 0.231

8.020.252

Total inedible offal as % of PSW

34.960.627

34.750.551

34.300.809

34.670.370

*P<0.05; **P<0.01


The total edible offal weight expressed in terms of pre slaughter weight was however similar in the three groups (4.79 % of PSW). Likewise the inedible offal weights and total inedible offal weight were also higher in C-AL than C2.5 and C1.5 whereas on expression of total inedible offal weight in terms of pre slaughter weight, the differences were non significant with over all average of 34.67 %. The higher edible and inedible offal weights of C-AL and C2.5 than C1.5 reflected the variation in their pre slaughter weight which got rationalized on expression in terms of pre slaughter weight hence the difference was found non significant.

 

The data on primal cuts and percent yield of half carcass are presented in Table 4.  The cut weights of the primal cuts reflected the trend of pre slaughter weight and were higher in C2.5 and C-AL than C1.5.


Table 4.  Cutability of standard cuts of the slaughtered lambs

Traits

C1.5

C2.5

C-AL

Pooled

Leg cut weight, kg**

1.49A0.038

1.71B0.053

2.02C0.081

1.740.0062

Leg as % of half carcass weight*

34.84 B 0.367

33.32 A 0.321

33.76A0.371

33.970.246

Loin cut weight, kg**

0.52 A 0.017

0.65 B 0.020

0.77 C 0.033

0.650.028

Loin as % of half carcass weight

12.170.192

12.780.316

12.830.511

12.590.211

Rack cut weight, kg**

0.52 A 0.021

0.63 B 0.018

0.76 C 0.043

0.640.028

Rack as % of half carcass weight

12.280.448

12.350.160

12.620.366

12.420.191

Neck and shoulder cut weight, kg**

1.08 A 0.031

1.31 B 0.040

1.50 C 0.067

1.300.049

Neck and shoulder as % of half carcass weight

25.360.697

25.64.0449

24.980.327

25.330.287

Breast and fore shank cut weight, kg**

0.66 A 0.028

0.81 B 0.031

0.94 C 0.019

0.800.032

Breast and fore shank as % half carcass weight

15.360.582

15.900.454

15.810.552

15.690.294

**P<0.01


Although the leg cut weight was higher (P<0.01) in C-AL than C2.5 and C1.5, in that order, still on expression in terms of % pre slaughter weight, a reverse trend was noted wherein it was similar in C2.5 and C-AL and significantly (P<0.01) higher in C1.5. It was evident from the results that with improvement in plane of nutrition in C2.5 and C-AL, the higher tissue accretion in these groups was on cuts other than leg.  Other cut weights viz. loin, rack, neck and shoulder and breast and fore shank also reflected the trends of pre slaughter and were higher in C2.5 and C-AL than C1.5 whereas on their expression in terms of pre slaughter weight, the cut proportions were found similar in the three groups. Similar trends in primal cuts was also noted by Sen et al. (2000) by slaughtering finisher lambs maintained on free grazing with varying levels of concentrate supplementation. The overall average cut proportion of three groups was 33.97, 12.59, 12.42, 25.33 and 15.69 % of half carcass for leg, loin, rack, neck and shoulder and breast and fore shank, respectively which was similar to earlier studies (Karim and Verma, 2001).

 

The lean, fat, bone and KOH bone of the primal cuts are presented in Table 5.


Table 5.  Dissected composition of standard cuts and half carcass, %

Traits

C1.5

C2.5

C-AL

Pooled

Leg

 

 

 

 

   Lean

72.161.058

72.230.978

71.180.978

71.860.558

   Fat

2.960.336

3.700.498

4.691.064

3.790.419

   Bone

23.790.882

22.711.116

23.40.721

23.300.511

   KOH bone

15.590.662

15.650.598

14.480.287

15.240.321

Loin

 

 

 

 

   Lean

62.842.334

62.431.291

58.503.486

61.261.454

   Fat *

10.33a1.081

14.07ab1.624

19.50b3.405

14.631.531

   Bone

20.011.457

18.612.085

17.961.401

18.860.933

   KOH bone

9.010.998

11.361.698

9.900.993

10.10.730

Rack

 

 

 

 

   Lean

62.791.126

54.831.015

54.551.191

57.390.638

   Fat

7.281.584

7.850.852

10.341.229

8.480.755

   Bone

31.951.837

29.520.510

27.481.416

29.650.866

   KOH bone

14.991.745

18.560.745

17.111.058

16.890.767

Neck and shoulder

 

 

 

 

   Lean

63.841.505

65.781.125

67.990.904

65.870.771

   Fat

7.301.928

6.39+1.013

6.601.202

6.760.784

   Bone

28.770.785

28.151.434

25.570.949

24.500.681

   KOH bone

14.491.269

18.931.261

15.761.185

16.390.810

Breast and fore shank

 

 

 

 

   Lean

55.821.722

58.711.050

59.781.105

58.100.826

   Fat

8.221.326

8.170.392

11.151.508

9.180.724

   Bone *

33.71b1.280

31.71ab0.623

29.08a1.001

31.500.713

   KOH bone

19.091.530

17.950.900

18.450.932

18.490.638

Half carcass

 

 

 

 

   Chilled weight, kg**

4.19A0.092

4.97B0.128

5.82C0.0209

4.990.181

   Chilling loss

2.640.354

3.160.467

2.860.523

2.690.271

   Lean

65.901.863

65.590.884

65.460.966

65.650.714

   Fat *

6.26a0.672

7.01ab0.473

8.94b1.312

7.400.557

   Bone

27.270.819

26.041.006

24.870.818

26.560.535

   KOH bone

16.040.847

16.770.785

15.300.640

15.700.453

*P<0.05; **P<0.01


The chilling loss % was higher in loin and rack than other primal cuts with an average of 2.7 % chilling loss of the half carcass. The lean content of primal cuts was similar in the three groups whereas, in general, with increase in level of concentrate supplementation, the fat content of the cuts increased with concomitant decrease in lean content. The loin fat content of C1.5 was 10.3 % which increased (P<0.05) to 14.1 and 19.5 %, respectively in C2.5 and C-AL. Considering that the lean, fat and bone content of loin cut to be an indicator of carcass fat content, it was evident that the carcass fat content increased with increase in  level of concentrate supplementation. The dissected half carcass fat content of C2.5 (7.0 %) and C-AL (8.9 %) was higher (P<0.05) than C1.5 (6.3 %) whereas the fat content of even C-AL was within acceptable norms i.e. less than 12- 13 %. Even with relatively higher half carcass fat content the feed conversion efficiency was better in lambs maintained under cafeteria system of feeding management (Singh et al. 2003) indicating that the carcass tissue accretion was in terms of lean content hence relatively higher fat deposition did not influence the feed conversion efficiency. The cost of feed input/kg dressed meat production was Rs. 61.72, 62.95 and 62.23, respectively in C1.5, C2.5 and C-AL. The dressed meat selling @ Rs. 100- 150 in different parts of the country together with the realization from edible and inedible offals has wide margin of profitability both for the producer and entrepreneurs for commercialization of the venture.


Conclusions


Acknowledgements

The authors are indebted to NATP for financial assistance and Director CSWRI for facilities provided to undertake the work. Technical assistance rendered by Mr. Nasimmuddin, T- 5 in slaughter studies is acknowledged.   

 

 

References

 

CSWRI 1998 35 Years of Research, Central Sheep and Wool Research Institute, Avikanagar, pp. 113-118

 

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Karim S A and Rawat P S 1997 Growth performance and carcass characteristics of lambs raised on varying proportion of roughage and concentrate. Indian Journal of Animal Sciences 67: 902-905

 

Karim S A, Santra A and Verma D L. 2002 Growth, feed conversion efficiency and carcass characteristics of Malpura and Malpura X Awassi crossbred lambs in a hot semiarid environment. Asian-Australasian Journal of Animal Science 15: 377-381

 

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Sen A R, Karim, S A and Santra A 2000 Carcass characteristics of finisher lambs maintained on grazing with supplementation. Indian Journal of Animal Sciences 70: 988-990

 

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Received 3 August 2007; Accepted 10 September 2007; Published 1 November 2007

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