Meat Yield of Lambs of Serbian “Improved Pirot Sheeps” Depending on Slaughter Results

Lambs of “improved Pirot sheep”, divided into three groups (6 male and 6 female in each group). The first group of lambs was fattened for 60 days, the second 120 and the third 180 days. At the end of the fattening, the lamb is slaughtered by the usual technique. Objective of this research was measurement of body mass prior to slaughtering, slaughter weight and to determine the meat yield (dressing percentage) depending on the length of the fattening and gender of the lamb. With increasing of fattening weights and fattening time, the yield of meat decreases, because the weight of the offal increases. Between all three groups for male and female lambs in a body mass before slaughtering, in a mass of a warm carcass with head and offal, in a body mass of a cold carcass with head and offal, in a body mass of a cold carcass without a head and offal there is a significant difference on the level (Р<0,001). In a dressing percentage of a warm carcass with head and offal, a dressing percentage of a cold carcass with head and offal, as well as a dressing percentage of a cold carcass without head and offal, for male and female lambs, there are a significant difference between the first and the second and the first and the third group levels (P<0.001). The results of examination the slaughtering characteristics show that female lambs of the first group achieved significant (P<0.05) higher yield of meat, compared to male lambs. Differences in other examined properties are not statistically significant. In the second group, the male lambs achieved higher body mass before slauthering and slaughter mass of female lambs (P<0.05), but no significant differences were found in the yield of meat. In the third group, male lambs achieved higher body mass before slauthering and slaughter mass, but female achieved higher yield of meat (P<0.05).


Introduction
The global growing tendency of lamb and mutton meat production has been evidenced, [1]. For sustainable sheep and goat production, it is necessary to know a number of biological, technological, organizational and market factors, [2]. The new Strategy for Agriculture and Rural Development in Serbia from 2014 to 2024 defines goals and priorities for further development of agriculture, [1]. Grasslands in Serbia represent natural resource and great production potential in development and improvement of livestock production, especially in hilly-mountainous regions which have not been exploited to the full extent so far [3][4][5].
The historical data concerning the characteristics of the Pirot sheep are scarce. The environmental conditions and poor pastures were the main factors that influenced the formation of Pirot sheep, [6]. According to [7], the body mass of an adult sheep was about 41 kg. Ewes of Pirot Zackel are polled. The lack of detailed description of the breed reflected the widespread policy that autochthonous animal breeds were "primitive", low in productivity and the signature of poverty. The selection of "improved animals" through crossbreeding with imported animals high in productivity was implemented as a compulsory measure of animal breeding and sheep reproduction practice in Socialist Yugoslavia. Even so, the Pirot sheep was highly appreciated for its good milk and wool quality. The length of lactation was around 190 days, and the average milk yield per lactation was 77.5 kg [7]. The wool yield was very low -1.4 kg per ewe, and 1.8 kg per ram [7]. The mandatory crossbreedings with Merino Precos and Wurtenbergin aiming to select larger animals for meat, increase the production of finer wool and preserve the milk production started in 1954, and the so-called "improved Pirot sheep" type was developed.
Research of [8], was carried out in population of R2 generation Pirot pramenka x Pirot improved sheep during period of three years. Lambs were divided into three groups: the first from 2.5 kg to 3.5 kg; the second from 3.6 kg to 4.5 kg; the third from 4.6 kg to 5.5 kg. Weight of lambs was controlled at birth, with 30, 60 and 90 days of age. Average body weight at birth of the tested lambs was 3.35 kg in the first group, 4.30 kg in the second group and 5.06 kg in the third group. At 30 days of age, the body weight of the lambs was 10.19 kg in the first group, 11.39 kg in the second and 12.49 kg in the third group. All these differences in body weight of lambs at birth were statistically highly significant (P<0.01). With 60 days of age, average body weight was 16.48 kg in the first group, 19.01 kg in the second and20.49 kg in the third group. Differences between groups of lambs at this age were statistically very significant (P<0.01). On the end of experiment at 90 days of lambs age, we have found the following values of the body weight of lambs: 26.35 kg in the first group, when the second 30.49 kg and 28.93 kg in the third group. Differences between groups of lambs at this age were statistically very significant (P<0.01).

Animals and Experimental Design
The experiment included a total of 36 lambs from the purified ennobled sheep divided into 3 groups (6 males and 6 females), according to the duration of the fattening period, as follows: I group 60 days fattening; II group 120 days fattening and III group 180 days fattening, at the farm Djumruk on Vlasina Lake, Republic of Serbia, at an altitude of over 1250 m in the environment that is environmentally clean. The test is performed only in lambs, lambing as unions, an intense form of lamb growing.

Plane of Nutrition
The daily meal of sheep breastfeeding from the beginning of the experiment to the 40 th day consisted of: seeds 1.8 kg / lamb; silage 1.5 kg / lamb and concentrate 0.5 kg / lamb.
In the first 10 days, the mother's milk was present in the diet of the lambs, and from the 11 th day until the end of the fattening, all three groups of lambs had at their disposal a pelleted concentrate and a quality seeds at will, whose consumption was monitored and recorded every day. The lambing period of the lambs was completed on the 40 th day of their life.
In the diet of all three groups of lambs, the pelleted concentrate and the quality seeds were represented until the end of the experiment and that no group was pasture or used any other foods.

Transport and Health Inspection of Lambs
After finishing the fattening, the lambs were slaughtered in the slaughterhouse Jugokop -Bujanovac, Serbia, which had an export character, which means that all necessary prerequisites for processing and storage of the meat received were met, according to the strict European standards.
Each group of lambs from farm to slaughterhouse was transported by truck. Twelve hours before slaughter, food was broken at the lambs, while water was available until loading in a truck.
Immediately after the landing of the lambs in the livestock depot, a visual inspection was carried out by the veterinary inspection, which concluded that all the lambs were in good condition, with good health and that they could go to slaughter.

Slaughter Procedure, Carcass Characteristics and Dissections
The slaughter of the lambs is carried out according to the technological procedure, according to the following phases: preparing lamb for slaughter; raising to the track; bleeding; removing the skin; evisceration and cooling.
After taking the linear measures is done cutting left half on basic parts, and their measurement. Then, the calculated values of the yield of individual tissues (meat, fat, bones) in the main parts of the carcass. After slaughtering the lambs, the primary processing and cooling, the halves are cut into the main parts.

Statistical Analysis
Variational statistical analysis was performed by analyzing the variance of two-factorial experiment (3 x 2), according to [9]. The differences in the mean values were tested with the Tukey test.

Results and Discussion
Average body weight immediately before slaughter of male lambs of the first group was 18.42 kg ( Table 1). The Depending on Slaughter Results dressing percentage of warm carcass with head and offal was 55.94%. The dressing percentage of cold carcass with head and offal was 54.22% and the dressing percentage of cold carcass without head and offal was 45.22%. Average body weight immediately before slaughter of female lambs of the first group was 16.92 kg ( Table 2). The dressing percentage of warm carcass with head and offal was 57.65%. The dressing percentage of cold carcass with head and offal was 56.25% and the dressing percentage of cold carcass without head and offal was 47.74%.
Average body weight immediately before slaughter of male lambs of the second group was 30.75 kg ( Table 1). The dressing percentage of warm carcass with head and offal was 54.17%. The dressing percentage of cold carcass with head and offal was 52.03% and the dressing percentage of cold carcass without head and offal was 43.61%. Average body weight immediately before slaughter of female lambs of the second group was 26.25 kg ( Table 2). The dressing percentage of warm carcass with head and offal was 54.62%. The dressing percentage of cold carcass with head and offal was 53.33% and the dressing percentage of cold carcass without head and offal was 42.66%.
Average body weight immediately before slaughter of male lambs of the third group was 37.08 kg ( Table 1). The dressing percentage of warm carcass with head and offal was 52.99%. The dressing percentage of cold carcass with head and offal was 52.01% and the dressing percentage of cold carcass without head and offal was 42.09%. Average body weight immediately before slaughter of female lambs of the third group was 33.50 kg ( Table 2). The dressing percentage of warm carcass with head and offal was 54.95%. The dressing percentage of cold carcass with head and offal was 53.88% and the dressing percentage of cold carcass without head and offal was 43.32%. Results of research [10], indicate that medium heavy kids (average body mass prior to slaughtering 17.61 kg) realize the best meat yield, i.e. higher dressing percentage of cooled carcass (55.85%) compared to light (average body mass prior to slaughtering 12.65 kg) whose dressing percentage was slightly (P>0.05) lower 54.69%, and heavier kids (average body mass prior to slaughtering 22.70 kg) whose dressing percentage was considerably (P<0.05) lower 52.93%. Between all three groups of male and female lambs in a body mass before slaughtering, in a mass of a warm carcass with head and offal, in a body mass of a cold carcass with head and offal, in a body mass of a cold carcass without a head and offal there is a significant difference on the level (Р<0.001).
In a dressing percentage of a warm carcass with head and offal, a dressing percentage of a cold carcass with head and offal, as well as a dressing percentage of a cold carcass without head and offal, for male and female lambs, there are a significant difference between the first and the second and the first and the third group levels (P<0.001).  Table 3 provides a comparison of the slaughtering results according to the gender of the lambs. The results of the examination of the slaughtering characteristics show that female lambs of the first group achieved significant (P<0.05) higher yield of meat, compared to male lambs. Differences in other examined properties are not statistically significant.
In the second group, the male lambs achieved higher body mass before slauthering and slaughter mass of female lambs (P<0.05), but no significant differences were found in the yield of meat.
In the third group, male lambs achieved higher body mass before slauthering and slaughter mass, but female achieved higher yield of meat (P<0.05). The results from Table 1 and 2 show that with increasing of fattening weights and fattening time, the yield of meat decreases because the weight of the offal increases. It was established that heavier kids have lower dressing percentage (55.01%) compared to lighter (57.21%) and medium heavy kids (58.21%), [10].
Supporting the current study, various authors [11][12][13][14] reported higher fatness level in lambs fed concentrate in sheepfold than lambs fed on pasture and concomitant dressing percentage increase. Group of authors [15] also reported an increase in fatness level of carcass with increasing slaughter weight of lambs. In study of [16] there are differences between rearing groups in terms of slaughter weight of lambs which were slaughtered at the same age -(winter rearing) lambs had the highest slaughter weight compared with other groups (springsummer rearing and autumn rearing).

Conclusion
With increasing of fattening weights and fattening time, the yield of meat decreases, because the weight of the offal increases. Between all three groups of male and female lambs all slaughtering properties there was a significant difference on the level (Р<0.001). In a dressing percentage of a warm carcass with head and offal, a dressing percentage of a cold carcass with head and offal, as well as a dressing percentage of a cold carcass without head and offal, for male and female lambs, there are a significant difference between the first and the second and the first and the third group levels (P<0.001). The results of the examination of the slaughtering characteristics show that female lambs of the first group achieved significant (P<0.05) higher yield of meat, compared to male lambs. Differences in other examined properties are not statistically significant. In the second group, the male lambs achieved higher body mass before slauthering and slaughter mass of female lambs (P<0.05), but no significant differences were found in the yield of meat. In the third group, male lambs achieved higher body mass before slauthering and slaughter mass, but female achieved higher yield of meat (P <0.05).