Livestock Research for Rural Development 19 (4) 2007 Guide for preparation of papers LRRD News

Citation of this paper

The influence of age and feeding regimen on the carcass traits of Arsi-Bale goats

Mesfin Tadesse

Jimma University Ambo College,
PO Box 19, Ambo, Ethiopia
tamesfin@yahoo.com

Abstract

The study was conducted to see the effect of age and feeding regimen on the carcass traits of Arsi-Bale goats kept under feedlot or range condition at Adami Tulu Agricultural research center. A total of 44 male goats of three age categories (six months, 12 months and 24 months) were assigned randomly to range and feedlot treatments. Arsi-Bale goats from two feeding regimen: Feedlot (FL) and Range(R) were slaughtered and live and carcass weight were taken. Twenty-four hours after death various yield measurements were collected. Carcass weight was highly significant (P<0.0001).

There was significant (p<0.05) interaction effect between feed and age groups with regard to weight gain. Weight gain of six month goats grazing on range was significantly higher (P< 0.05) compared to their contemporaries managed on feedlot, but no significance observed in other age groups and feeding regimen. Yearling goats managed on range deposited higher (p<0.01) scrotal fat than their contemporaries managed on feedlot.

In generally feeding goats in the feedlot is not recommended for Arsi Bale goats as they perform equally when raised only in the range condition. Even though there is no significant with regard to weight gain in different ages, 12 months goats managed on range are generally better for weight gain.

Key words: Age, Arsi-Bale goats, carcass characteristics, feeding regimen


Introduction

Goat production in Ethiopia historically has been a low labor enterprise with little emphasis on animal productivity and management practices. Maintained virtually under the traditional subsistence oriented management systems goats constitute an important livestock component in all ecological zones and agricultural systems in the country.

Goats make a significant contribution to income generation and supply of animal source food to resource-poor rural households. In general, the relatively huge number of livestock resources, proximity to the export markets and the liberalization of the economy give the country comparative advantage in livestock trade.

Small ruminants are kept for various purposes and objectives. The roll of small ruminants for income generation, food supply (protein, essential micronutrients, vitamin A, iodine,and ion) and financial security for the rural population is well established (Gryseels 1988; Zelalem and Fletcher 1993; Barrs 1998; Workneh Ayalew 1998).

The value of meat animals lies in the acceptability of the carcass on the market. Evaluation of meat quality and composition is important to the producers, meat packers, and retailers and consumers. Ethiopia's lowland cattle breed; sheep, goats and camels are highly demanded in neighboring countries as well as the strategic livestock markets of the Middle East (Belachew and Jemal 2003).

Goat meat evaluations have received little attention and as a result knowledge of yield and quality of goat meat is limited when compared to sheep and cattle (Warmington and Kirton 1990; Anous and Mourad 1993). Nevertheless, this situation is changing because of increase in demand for goat meat. Thus, to be profitable and satisfy market demands further performance evaluation of carcass traits and improvement is required. Thus, the purpose of this study was to see the effect of feeding regimen and age groups on the carcass trait of Arsi-Bale goats.
 

Methodology

The experiment was conducted at Adami Tulu Agricultural Research Center (ATARC) situated at a latitude of 70 9'N and 380 7'E longitude with an altitude of 1650 m.a.sl. in the semi-arid middle rift valley of Ethiopia. The soil is fine sandy loam with sand silt and clay in the proportion of 34, 48 and 18%, respectively It receives bimodal unevenly distributed average annual rainfall of 760.9 mm (ATARC 1998) The area is mainly dominated by pennesitum; cinchrus grass species, forbs and acacia trees.

A total of 44 Arsi-Bale goats of three age groups (six, 12, 24 months) were bought from nearby located markets. The animals were dewormed and sprayed against internal and external parasites before commencement of the experiments respectively. After two weeks of adaptation period equal number of goats (each 22 animals) were assigned randomly to feedlots and range. Those goats assigned to feedlots were supplemented with concentrate while there was no provision for goats managed on range. The goats in the feedlot treatments were supplemented gradually up to 900g concentrate/head/day in accordance with their body weight.

The composition of the concentrate feed was 50% noug cake, 49% wheat bran and 1% salt. Hay was supplied to feedlot goats' adlibitum and all experimental goats had free access to water. Goats on the range were fed on native grass/forbs or shrubs for the whole experimental period.

Feeding commenced at 08.00 a. m and collection of feed refusals was done 24 h later. Feed offered and refusals from each age group were weighed. Intake was calculated as the difference between feed offered and refused corrected for dry-matter content. Each goat was weighed at the beginning of the experiment and every successive fortnightly thereafter. Average daily gains (g/d) were calculated as differences between final and initial body weights divided by number of days of feeding.

At the end of experiment the goats were fasted for 16 hours with free access to water and were weighed moreover slaughtered and dressed in the center's abattoir. The empty gut and dressed carcass were weighed separately. Hot carcass weight, weight of the head, skin, visceral organs (heart, liver, lung and kidneys) and fat depots (scrotal fat, kidney, pelvic fat and omental fat) were also recorded.

Carcass were chilled at -100c and at approximately 24 hrs postmortem the following measurement were taken: Longissimus muscle area at 12th ribs, fat thickness, muscles, fat and bone weight of different parts (leg, loin, shoulder and neck as well as shank and breast). Waterproof paper was used for measuring the rib eye area and fat thickness was measured by using a ruler at the mid point of the 12th and 13th ribs.

Analyses involved 2x3 factorial arrangement with feeding regime (feedlots and range) and age groups (6, 12 and 24 months). All data were analyzed using PROC GLM (SAS 2000). Analyses were conducted with the model that included age groups and feeding regime as a main effects and two-way interaction between them.

The following statistical model was used for the analyses:

Yijk = μ + ai +fj+ eijk

Where:

Yijk = individual observation,

μ = general mean,

ai = effect of ith age (i =6,12,24),

fj= effect of jth feeding regimen(Feedlot, range),

eijk = residual error,

Means were separated using Tukey test (α=0.05).
 

Results and discussion

Significance difference was observed in daily feed intake among age groups in which feed intake increases with age groups (Table 1).

Table 1.  Least square mean of daily feed intake of goats under feedlot condition

Age of animals, months

Daily Feed Intake, kg  (Mean   s.e)

6

0.598c 0.006

12

0.871b 0.010

24

1.014a  0.009

*Different letters across column indicate significance (p<0.05)

Since the volume of gut increases with the age so does the feed intake moreover maintenance requirement is higher for older ones. Weight gain of six month goats grazing on range was significantly higher (P< 0.05) compared to their contemporaries kept on feedlots, but no significance was found in other age groups even though weight gain of 24 months of feedlots was higher than their contemporaries on range (47.5 vs 24.3) as it can be seen from figure1.


Figure 1.   Least square mean of weight gain across age and feeding regimen


This is mainly related to growth that is responsible for the weight gain in younger animals.

Yearling goats managed on range deposited higher (p<0.01) scrotal fat than those on feedlot.) Internal fat content of Arsi-Bale goats increase with age although not statistically significant (P>0.05).

As indicated in Table 2 no significant difference was observed between six month goats with regard to live weight, pelvic fat, rib eye area and scrotal fat in feedlots and range condition but with inference to hot carcass weight, chilled carcass weight and dressing percentage the goats managed on range outperformed significantly (P< 0.05) than feedlot group.

Table 2.   Mean and standard error of Carcass yield for goats with age groups and feeding regime

Parameters

6 months

12 months

24 months

Feedlot (FL)

Range (R)

Feedlot (FL)

Range (R)

Feedlot (FL)

Range (FL)

Live weight, kg

14.3a 0.66

15.5a 0.54

25.3a1.61

28.8a0.95

30.3a 1.76

34.2 a 0.6

Hot carcass weight, kg

5.1b 0.2

6.3a 0.23

10.7a1.00

12.8a0.77

12.9 a 0.87

15.1 a 0.22

Rib eye area

28a 0.02

37.66a0.32

49.25a0.02

49.00a 0.04

2.50 0.04

1.5 0.015

Fat thickness, mm

1

-

1.670.33

-

2.5 a 1.50

1.5 a 0.50

Heart fat, kg

0.02a 0.01

0.03a 0.01

0.03a 0.01

0.02a 0.01

0.04 a0.01

0.06 a 0.03

Pelvic fat

0.031 a 0.01

0.027 a 0.01

0.030 a  0.02

0.02 a  0.015

0.042 a0.02

0.064 a 0.03

Scrotal fat, kg

0.011 a 0.003

0.015a 0.01

0.016b 0.004

0.039a 0.005

0.04a0.03

0.01a 0.004

Dressing %

35.6 b 0.86

40.4a 1.21

42.3a1.34

44.2a1.36

42.1 a 60.96

44.3 a 0.87

Full gut, kg

3.98a0.27

3.99a 0.2

4.84a0.59

5.46a0.06

5.8a0.25

6.68a0.67

*Different letters across rows indicate significance (p<0.05)

Live weight, hot carcass weight, dressing percentage, rib eye area and pelvic fat for 12 month goats were not significant under feedlots and range condition; however, scrotal fat was found to be significantly higher (P< 0.05) in case of range condition compared to feedlots. All aforementioned parameters were found to be insignificant under feedlots and range condition for 24 months goats.

Mean percentage of carcass component within feeding regimen and age are reported in table 3.

Table 3.  Mean and standard error of carcass component for goats with age groups and feeding regimen

Components, %

6 months

12 months

24 months

FL

R

FL

R

FL

R

Leg

Bone

25.11 a 1.96

25.89 a 2.11

25.00 a 1.51

24.58 a 2.22

34.25 a 7.21

26.18 a 4.09

Muscle

71.88 a 2.94

72.85 a 1.05

72.11 a 1.18

62.78 a 12.1

64.67 a 8.01

72.81 a 4.42

Fat

1.83 a 0.64

0.69 a 0.51

2.47 a 0.3

0.54b 0.33

1.11 a 0.83

0.89 a 0.37

Loin

Bone

34.0 a 6.67

37.08 a 5.28

20.90 a 3.98

27.43 a 6.18

19.97 a 2.21

22.14 a 6.12

Muscle

64.8a6.15

62.91a 62.91

72.67 a 3.90

72.11 a 5.96

74.66 a 2.68

76.77 a 7.03

Fat

2.84 a 1.07

0.83 a 0.55

3.51 a 1.59

0.40 a 0.4

5.11 a 3.30

1.71 a 1.41

Rack

Bone

35.27 a 5.51

33.03 a 5.19

33.19 a 1.2

30.61 a 3.85

32.45 a 2.20

29.81 a 70.18

Muscle

60.44 a 6.88

61.96 a 2.93

64.17 a 1.07

67.10 a 2.84

64.52b0.93

70.18 a 0.62

Fat

0.99 a 0.60

0.00 a 0.0

1.54 a 0.71

0.12 a 0.12

3.30 a 1.79

0.09 a 0.09

Breast and shank

Bone

32.50 a 3.50

35.89 a 2.51

33.94a 1.78

19.12 a 6.62

30.1a 70.55

26.69b  0.52

Muscle

58.05 a 3.52

57.41 a 2.70

61.64a 2.67

51.09 a 17.43

64.91a3.07

70.49a 1.29

Fat

3.63 a 1.29

2.25 a 1.30

3.80 a 1.14

5.17 a  3.85

4.72a 3.34

2.93a 1.07

Shoulder and neck

Bone

33.94 a 7.26

25.34 a 4.33

24.71a 3.12

22.28 a 1.33

23.98a 2.79

48.04a 27.58

Muscle

62.61 a 7.60

70.95 a 1.49

69.43a 2.55

73.07 a 3.24

71.77a 2.57

59.06a 18.53

Fat

2.20a 0.85

1.44a0.85

3.87 a 0.48

3.06 a 2.33

4.25a 1.58

1.59a 0.18

Means within the row with different subscript letter differ at P<0.05

The proportion of bone ranges from 25.11% to 35.89%. This is in agreement with the reports of Fonseca (1987) for Chernequiera goats and Ash and Norton (1987) for Australian Feral goats, but higher than Morand-Fehr et al (1976) for carcass weight ranged from 8-13kg for Alpine goats. The lean percentage of the Arsi-Bale goat ranges from 51.09 to 76.77. Yearling goats raised on the range had higher (p<0.01) fat from the leg compared to range. Higher (p<0.05) proportion of bone was found in two years Buck of feedlot condition when seen in line with range condition.
 

Conclusion and recommendation

Arsi-Bale goats did not like the feedlot management in which there was a provision of high diet concentrate and achieved the same result with those managed on range condition. Yearling age was found to be better to undertake the fattening even though it was not as such statistically significant from other groups. Parameters like live weight, carcass weight as well as almost all carcass characteristics were not significant. The Arsi-Bale goats may show significance in live weight, carcass weight as well as carcass characteristics provided that they are allowed to graze and supplemented with concentrate at night.
 

Acknowledgements

We want to thank Dr. Girma Taye for his assistance in data analysis and Oromia Agricultural Research Institute (OARI) for funding this experiment. Lastly, Mesert Terefe also contributed in animal management and data record.
 

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Received 12 December 2006; Accepted 13 February 2007; Published 2 April 2007

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