Growth performance and carcass characteristics of Iranian fat-tailed crossbred lambs

Abbas Atefi, Jalil Shoja, Seyyed Abbas Rafat and Yadollah Jahani Maleki

Department of Animal Science, College of Agriculture, Tabriz University, Tabriz, Iran
abbas.atefi@gmail.com

Abstract

 In this study the growth performance and carcass traits of Iranian pure and crossbred lambs (5 genetic groups) were compared. After weaning, the growth rates of male lambs were measured. At the end of the rearing period lambs were slaughtered and the left side of the carcass was cut into six pieces.  Fixed effect of Genotype and birth type has been studied.

Genotype had significant effect on start weight, neck weight, weight of fat-tail and weight of total body fat. There were no differences due to genotypes and birth types in physical traits and offal parts of carcass.  

Keywords: Breed, carcass, growth, Iran, lamb

Introduction

In Iran, all sheep breeds are fat-tailed except the Zel breed. Meat from sheep accounts for approximately 45% of the total red meat production in Iran (FAOSTAT). The fat deposited in the body or tail is laid down at a much higher cost in terms of feed energy than lean meat. Also, the consumers in many instances show an increasing preference for lean meat. Therefore, either removing or reducing the size of the fat-tail of local sheep can be an objective for the sheep industry of the country (Kashan et al 2005). Moghani, Ghezel, Baluchi and Makui are native breeds of Iran. The aim of this study was to investigate the efficiency of live weight gain and carcass quality in Iranian fat-tailed crossbred lambs.

Materials and methods

This study was conducted at the Research Station of Khalatpushan, faculty of Agriculture, University of Tabriz. Five genotypes including Ghezel, Moghani× Baluchi, Ghezel× Baluchi, Ghezel× Akhar Merinos and Moghani× Merinos (Four of the genotypes were F1 crosses) have been compared in this study. A total of 30 male lambs (6 lambs per genotype) were included in the trial. The lambs were reared with their dams and had all the ewes’ milk from birth until an average age of 90 days. Two weeks prior to the trial, the lambs were treated for internal and external parasites. The lambs were fed in a group with alfalfa and supplement (including barley and maize) under an intensive feeding and management system. The ratio of alfalfa to supplement in the ration was 60:40. During the 150-day fattening period, the lambs were weighed each week. The feed was offered twice a day on the basis of 3–4% of body weight. Every morning and before feeding the animals, extra feed from the previous day was collected.

The weekly feed consumption of each group was determined from difference of the two respective weights.

 

After slaughter, head, skin, feet and offal were removed from the carcass and skin were weighed. The carcasses were chilled at 4 ◦C for 24 h. Then, the carcasses were split longitudinally into two parts. The left side of carcasses were cut into six pieces (neck, shoulder, rib, sirloin, flank, leg shank) and fat-tail were weighed separately (Figure 1a).

 

Figure 1. a: Wholesale cuts of lamb carcass as Iranian standard, b : Physical traits

 

The physical traits were recorded as shown in Figure 1b. The physical traits included length of carcass (K), width of pelvis (G), length of gigot1 (H), length of gigot2 (A), length of gigot3 (F), width of shoulder (M), diamond of bone (OS) and width of breast (LAC).

 

The statistical model for the analysis of growth performance, physical traits, commercial joints and carcass included fixed effects of lamb breed (5 genetic groups ), birth type ( single, twins), first order interactions and residual error. The final live weight of the lambs was used as co-variate for fat-tail and carcass weight, while carcass weight was used as co-variate for the carcass components. The analysis was performed by proc GLM of SAS.

Results and Discussion

Mean growth performance, offal parts, carcass cuts and physical traits are presented in Table1. The average birth weight from the recorded groups was 3.89 kg. Higher birth weights were recorded for single lambs (4.26 kg vs.3.53 kg). The differences between types of birth reflect different inter uterus and feeding conditions.

 

There were no differences due to genotypes and birth types in physical traits and offal parts of carcass. Ghezel×Arkhar Merino lambs had significantly higher (P < 0.05) neck weight than other lambs. However, the weights of other carcass cuts were similar between five genetic groups.

The primary objective of crossing Iranian breeds with the tailed breeds was to improve rate of weight gain, feed efficiency and reduce the carcass fat content in order to divert energy stored as fat in the tail to meat in the carcass. Nevertheless, the present data show that the fat-tail in crossbred lambs of Arkhar Merino and Ghezel was about 60% less, and internal fat was 50% more than Ghezel pure lambs (P < 0.01). The total body fat (including subcutaneous, internal and fat-tail) of Arkhar Merino lambs was 30% lower than the Ghezel pure lambs. The decrease of fat-tail and increase of  internal fat in crossbred lambs is in agreement with Kyanzad (2001), where the percentage of fat-tail, total Subcutaneous fat (SCF) and  inter muscular fat (IMF) were 16.6, 20.1 in Chaal and 6.6, 27.5 in Zel×Chaal and were 1.9, 27.3 in purebred Zel lambs, respectively. Also, the results of fat deposition of the present crossbreeding experiment can be compared to docking the fat-tailed lambs.

 

In docked lambs compared to control fat-tailed lambs the loss of fat in the tail was compensated for by a greater quantity of SCF and IMF and internal fat (Donovan et al 1973, Shelton et al 1991, Shelton 1990, Bicer et al 1984).

 

It is clear from the present data that in spite of lower fat-tail percentage in crossbred lambs, none of two cross combinations were significantly superior in terms of economically important traits such as, average daily gain, lean meat and lean to bone ratio. In tailed sheep breeds the fat in carcass is mostly deposed as SCF and IMF. For example, the percentage of total SCF and IMF, fat-tail and chemical lipid of the Zel sheep breed is reported to be 27.3, 1.9 and 29.4, respectively (Kyanzad 2001).

About half of the total body fat (carcass and internal fat), of the fat tailed breeds are stored as fat-tail and internal fat. When pasture becomes scarce these sheep draw upon the fat reserves stored in their tails for nutriment. Two other considerable points are that, the quality of fat-tail is higher in terms of lower saturated fatty acids compared with internal, SCF and IMF, (Kashan et al 1997), while the fat-tail is easily removed from the carcass in the abattoir or butcher shop. These characteristics need to be considered in determining the superior carcass quality of pure animals than their crosses.

In general, results of the study showed no major differences in growth performance, carcass characteristics and physical composition of carcass among the five genotypes investigated in this study.

References

Bicer O, Pekel E and Guney O 1984 Effects of docking on growth performance and carcass characteristics of fat-tailed Awassi ram lambs. Small Ruminant Research  8: 353–357.

 

Donovan P B O, Ghadaki M B, Beheshti R D and Salehi B A 1973 Performance and carcass composition of docked and control fattailed Kellakui lambs. Animal Production 16: 67–76.

 

Fozooni R and Zamiri M J 2007 Relationships between chemical composition of meat from carcass cuts and the whole carcass in Iranian fat-tailed sheep as affected by breed and feeding level. Iranian Journal of Veterinary 8: 304-312.

 

Kashan N E J, Manafi Azar G H, Afzalzadeh A and Salehi A 2005 Growth performance and carcass quality of fattening lambs from fat-tailed and tailed sheep breeds. Small Ruminant Research 60: 267–271.

 

Kashan N E J, Alipanah M and Eghbaleh A 1997 Study of fatty acids in tail fat internal fat and meat of three fat-tailed Iranian sheep. First Sheep and Goat Congress Animal Science Research Institute, Karaj, Iran, pp 223–230 ( in Persian).
 

Khaldari M, Kashan N, Afzalzadeh A and Salehi A 2007 Growth and carcass characteristics of crossbred progeny from lean-tailed and fat-tailed sheep breeds. South African Journal of Animal Science 37: 51-56.

 

Kirton A H, Bennett G L, Dobbie J L, Mercer G J K and Duganzich D M 1995 Effect of sire breed (South down, Suffolk), sex, and growth path on carcass composition of crossbred lambs. New Zealand Journal of Agriculture Research, 38: 105-114.
 

Kyanzad M R 2001 Crossbreeding of the three Iranian sheep breeds with emphasis on growth and carcass characteristics of the lambs. Ph.D. Thesis. University of Utra, Malaysia.

 

Macit M, Shahin S, Esenbuga N and Karaoglu M 2003 Growth and carcass characteristics of three fat-tailed pure breeds under grazing with concentrate supplementation. Turk Journal of Veterinary Animal Science 27:331-337.

 

SAS 2004 User’s Guide Version 9.1 SAS Institute.

 

Shelton M, Willingham T, Thompson P and Roberts E M 1991 Influence of docking and castration on growth and carcass traits of fat-tailed Karakul, Rambouillet and crossbred lambs. Small Ruminant Research 4: 235–243.

 

Thieme O, Ali Zaman M and Ugurlu A 1999 Performance of Village Sheep Flocks in Central Anatolia. I. Growth of lambs. Turkey Journal of Veterinary Animal Science 23: 467–474.

Received 12 November 2011; Accepted 30 December 2011; Published 7 February 2012

Go to top