A COMPARATIVE STUDT ON GROWTH, CARCASS TRAITS AND BODY COMPOSITION OF AWASSI AND KARADI LAMBS RAISED UNDER TWO LEVELS OF FEEDING AND SLAUGHTERED AT DIFFERENT WEIGHTS: 2- BODY COMPOSITION AND CARCASS TISSUE DISTRIBUTION

1109 A COMPARATIVE STUDT ON GROWTH, CARCASS TRAITS AND BODY COMPOSITION OF AWASSI AND KARADI LAMBS RAISED UNDER TWO LEVELS OF FEEDING AND SLAUGHTERED AT DIFFERENT WEIGHTS: 2BODY COMPOSITION AND CARCASS TISSUE DISTRIBUTION D. A. O. Al-Sherwany J. E. Alkass Assit. Prof . Prof . College of Agricultural Engineering Sciences College of Agricultural Engineering Sciences University of Salahaddin University of Duhok dler.othman@su.edu.krd nljealkas2001@yahoo.com ABSTRACT A total of 32 weaned (3.5-4 months) of Awassi (16) and Karadi (16) lambs were randomly allocated into two equal groups to be fed either ad libitum or 3% of their body weight concentrate, and to be slaughtered at 36 and 44 kg body weight. After chilling at 4 0 c for 24h, the carcass was split along the vertebral column into two halves by electric saw, and the left side was separated into eight whole sale cuts and were physically dissected into lean, fat and bone and weighed. Results reveal that the overall mean of lean, fat, bone, lean: fat and lean: bone ratio were 60.31±0.25%, 17.05± 0.69%, 22.63 ± 0.59%, 3.78 ±0.20 and 2.71 ± 0.06, respectively. It was noticed that Karadi lambs surpass significantly (P<0.01) Awassi lambs in the content of lean (61.32±0.29 vs. 59.30±0.21%) and bone (24.72±0.85 vs. 20.53±0.35%) and had lower content of fat (13.94±0.75 vs. 20.15±0.39%). Neither lambs fed ad libitum nor 3% concentrate had a significant effect on composition of the carcasses. Lambs slaughtered at 44 kg had significantly (P<0.01) higher content of fat and lower bone content. Awassi lambs and those slaughtered at 44 kg had significantly (P<0.01) higher total body fat than did Karadi lambs and those slaughtered at 36 kg.


INTRODUCTION
Meat production depends on several environmental factors and management practices. Meat animal carcasses vary in composition through genetic, age and sex of animal, nutritional, and environmental effects (12). Moreover, growth and development are the basis for meat production, whereas, distribution of carcass tissues are significant in determining carcass quality. Lean muscle and to a lesser extent fat, are the major edible tissue of the carcass (18). Thus, a high proportion of muscle with a low proportion of bone and an optimum level of fat represent a superior carcass (23). It is known that the distribution of muscle, bone and fat is largely a function of maturity (25), and as animal become older and heavier the proportion of fat in their carcasses increases and the proportion of muscles and bones decreases (12). Also, it was recognized that diet have been shown to be one of the main factors affecting the carcass yield, composition and qualities in many species (33,35). Thus the objectives of this study is to evaluate Awassi and Karadi lambs for carcass composition and tissue distribution raised under two levels of feeding and carcass slaughtered at two different weights.

MATERIALS AND METHODS Animals and experimental design
Sixteen weaned (3.5-4 months) entire male lambs from each of Awassi and Karadi with an average initial weight of 25.62±0.57 and 25.56±0.73 kg, respectively maintained at Grdarasha field, College of Agricultural Engineering Sciences, Salahaddin University were used in the current investigation. Full detail of management, feeding and slaughtering was described in our previous study (5). In brief, lambs from each breed were divided equally into two subgroups (8 lambs) to be fed concentrate either ad lib concentrate or 3% concentrate of their body weights, and to be slaughtered at 36 and 44kg (4 lambs). Animals were slaughtered when each individual lamb reached its designated body weight. After chilling the carcass at 4 0 c for 24h, the carcass was split along the vertebral column into two halves.

Physical dissection
Eight cuts of the left half carcasses were weighed and dissected completely into lean, fat and bone. The three components were weighed separately to determine their percentages. Non-carcass fat was the sum of the omental, mesenteric, pelvic, kidney, scrotal and cardiac fat. Carcass fat including subcutaneous and intermuscular fat was separated from each cut.

Statistical analysis
General Linear Model within SAS (31) was used to study the effect of breed, feeding level and slaughter weight on studied traits. Significant difference between means were assessed using Duncan multiple range tests (9).

RESULTS AND DISCUSSION Tissue distribution in the carcass
The proportion of separable carcass tissue of cuts and carcass side of Karadi and Awassi lambs fed either ad lib or 3% concentrate and slaughtered at 36 and 44 kg are given in Tables (1 and 2). It seems from Table (1) that lean percentage of Karadi lambs surpass significantly (P<0.01) Awassi lambs in the leg, loin and flank cuts. On the other hand, the proportion of lean in the fore shank cut only was significantly higher (P<0.01) in Awassi. Moreover, lean percent is almost similar in rack, shoulder, neck and breast cuts. With respect to percent fat in the different cuts, results reveal that with the exception of fore shank, the proportion of fat in the remaining cuts of Awassi lambs excelled significantly (P<0.01) Karadi lambs. Also, with the exception of neck cut, the proportion of bone in all carcass cuts was significantly (P<0.01) higher in Karadi lambs as compared to Awassi carcasses. Thus as it appears from  (24) found that Awassi lambs had higher fat and lower bone content as compared with Hamdani lambs. Also, several authors found breed differences in carcass composition (6, 20, 34). Additionally, muscle content varied according to its location in the carcass. For example, the higher muscle content was in the leg (66.50%), whereas the lowest was in the breast (54.44%) and fore shank (47.53%) in Karadi lambs. In the Awassi lambs, the highest lean content was in the shoulder (65.66%) and the lowest in the breast (54.76%) and the fore shank (53.07%) ( Table 1). Such variation in muscle mass is primarily due to differences in the total number of muscle fiber. Possibly the evolutionary increases in muscle fiber size is limited by physiological status in that normal cell function is maintained only as long as certain limit in cell size is not exceeded (27). As slaughter weight increases from 36 to 44 kg, the lean proportion increased either numerically or significantly (P<0.01) in the rack, neck and fore shank cuts. However, a decrease in lean percent was noticed in the loin, breast and flank cuts (Table 1). Such result could be attributed mainly to the fact that muscle distribution is affected by the differential rate of growth in individual muscle and muscle groups on the carcass (7). With the exception of the neck cut, the fat content in all cuts in the carcass as well as the whole carcass side increased with the increases of slaughter weight from 36 to 44 kg (Table 1 & 2). It is well known that the fat is a late growing body tissue and therefore proportions in the carcass greatly changed with the progress of growth (7). A significant (P<0.01) decrease in the proportion of bone was noticed of all cuts and the whole side in lambs slaughtered at 44 kg compared to those slaughtered at 36 kg. It is well known that bone is an early maturity carcass component so it grows at slower rate during post-natal life, and consequently decreasing with increasing body weight (17,21). In general, the proportion of lean and fat in the half carcass increased by 0.80 and 23.70%, respectively. This increase was associated in a decrease in bone content by 20.16%. Several investigators noted that as slaughter weight increased, there is mainly an increase in fat and a decrease in bone proportion of the carcass (2, 10, 24, 32). From the results given in Table (1), it appears that lambs slaughtered at 36 kg had higher lean: fat ratio (4.29±0.35 vs. 3.28±0.13) and lower lean: bone ratio (2.47±0.08 vs. 2.95±0.04) as compared with lambs slaughtered at 44 kg. Since the proportion of fat increasing and bone content is decreasing, therefore, the result is expected. Previous workers also reported decreasing carcass lean: fat ratio (16, 36) and increasing lean: bone ratios (8, 30). It appears from Tables 1 and 2 that the effect of level of feeding on carcass composition either on all cuts or the whole side was not significant except that lambs fed ad lib had lower bone proportion in the leg cut and a higher bone in the neck cut. However, it is generally agreed that animals full-fed high concentrate diet usually produce more-carcass fat, and consequently, are less efficient in converting feed to lean meat than an animals fed slightly below ad libitum energy intake, even though the ad libitum fed animals would be more efficient in total feed energy retention. This is particularly evident in the late stage of growth, as muscle and bone approach their mature size (12).

Partition of fat
It is well documented that fat is the most variable tissue in the carcass, and it varies not in its total amount but also in its distribution between the various deposits which alter markedly during growth, and the proportion and location of fat in the body are important in meat animals (19). In the present work, weight of carcass fat, non-carcass fat, fat tail and total body fat averaged 2.51±0. 15 This finding is similar to those noticed by Koyuncu (15), Mustafa et al (22) and Alkass and Hassan, (3). However, Kempster et al. (14) reviewed knowledge on fat partitioning in sheep and pointed out, just as it has been recorded by Hammond (11) that sheep differed considerably in the manner in which they partitioned their body fat. Such difference may be related to environmental origin of breed. It appears from