Effect of Docking on Adaptation, Fertility and Meat Quality of Growing Fat-Tail Awassi Ram Lambs.
The aim of this study was to evaluate the effect of fat tail docking on adaptation, fertility and meat quality of growing fat tail Awassi ram lambs in comparison with meat quality of thin-tail Lacaune sheep. Fifty-seven new-born ram lambs (Nine Lacaune and forty-eight Awassi breeds) were brought to the experimental farm. All Animals were grown under the same management and feeding conditions. The study includes two parts, a first part concerning growth and fertility, and a second part concerning meat quality. After weaning, thin-tailed intact Lacaune (IL) animals were left intact until one year of age for the meat quality study. In the first experiment, fat-tailed Awassi ram lambs were divided equally into two groups: docked Awassi (DA) and intact Awassi (IA) animals. Docking was applied at 1-3 weeks of age with a rubber-ring elastrator. Each group was divided into 2 sub-groups: one ventilated (V), and one left at ambient temperature for control (C). Data was collected every ten days over a period of one year. Studied parameters (body measurements, adaptation measurements, testicular measurements and semen quality) were retrieved during four physiological periods: growth (PI), pre-pubertal (PII), pubertal (PIII) and sexual activity period (PIV). During the growth period, body weight was negatively affected by docking however during the other periods docked animals had a better development. Adaptation measurements did not differ significantly among groups. During the sexual activity period, the recorded values of semen volume, motility, concentration, and abnormalities gave the best results in the docked ventilated animals (DAV), the docked control (DAC) followed, than the intact ventilated (IAV) and finally, the intact control (IAC) animals showed the lowest fertility results. During sexual activity period, semen volume was 1.4±0.4ml for DAV vs. 1.3±0.3ml for DAC, both significantly different (P<0.05) than intact animals (0.9±0.2ml for IAV and 0.6±0.2ml for IAC). The semen motility was 85.1±2.7% for DAV, vs. 84.4±0.7% for DAC, both significantly higher (P<0.05) than intact animals (76.1±0.7% for IAV and 72.4±0.4% for IAC). Sperm concentration for DAV was 2.5±0.2x109spz/ml vs. 1.5±0.1 x109spz /ml for DAC, both significantly higher (P<0.05) than intact animals (1.3±0.3 x109spz /ml for IAV and 1.1±0.2x109spz /ml for IAC). Semen abnormalities were 12.2±0.3% for DAV vs. 14.1±0.4% for DAC, significantly lower (P<0.05) than intact animals (15.2±0.9% for IAV and 16.6±0.3% for IAC). In the second part of the experiment, 27 rams (9 Intact Lacaune, 9 Docked Awassi and 9 Intact Awassi) having the same body weight and growing conditions, were slaughtered at one year of age. Three samples of muscles were excised from each carcass; Biceps Femoris (Bf), Longissimus Dorsii (Ld) and Gluteus Medius (Gm). Samples were used for the assessment of the ultimate pH, and the meat quality traits. The ultimate pH was significantly higher (P<0.01) in the three different studied muscles of Lacaune breed as compared to both docked and intact Awassi breed. Concerning fat content, DA animals had significantly higher (P<0.01) fat content in Ld muscle than IA and IL lambs. Moreover, color results showed that both Awassi groups presented higher L* values than Lacaune animals (P<0.05). In addition for Awassi breed, L* values of Bf and Gm muscles were significantly greater (P<0.05) than that of Ld muscle. Color b* values were significantly greater (P<0.05) in Gm of all animals under study. Lacaune group had lower drip loss values than Awassi groups (P<0.05 in Bf and Gm muscles and P<0.01 in Ld muscle). However, for Awassi breed, the drip loss in Ld muscle of DA animals was significantly lower (P<0.01) than IA ones. Furthermore, thawing and cooking losses were neither affected by breed nor by docking. Regarding the PND values, the Ld muscle of DA group presented higher values (P<0.05) than Bf and Gm muscles of both intact groups. In addition, cooked meat PND values were significantly higher (P<0.05) in Ld muscle of DA when compared to intact groups. In conclusion, it can be said that docking and ventilation of fat-tailed Awassi lambs were beneficial in improving growth and semen quality of the animals. Due to the scarcity of information in this area of research, further investigations are needed.
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