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Ecotype; Eosin-nigrosin; Gallus gallus domesticus; local chickens, semen quality
Several findings on the semen characteristics of domestic chickens have revealed that ecotype and age significantly affect semen quality. There is, however, lack of data on effects of ecotype and age on semen characteristics of Tanzanian native roosters. This study evaluated the effect of ecotypes (Ching’wekwe, Morogoro-medium and Kuchi) and ages (11-15 and 24-28 months) on semen quality. A total of 192 semen samples were collected from 12 roosters (four from each ecotype) using the abdominal massage technique at weekly interval for four consecutive months. Semen characteristics of individual samples were evaluated. The semen volume, pH, sperm motility, sperm concentration, proportion of spermatozoa with normal morphology and proportion of live spermatozoa among the ecotypes varied from 0.42±0.04 to 0.52±0.03mL, 7.01±0.00 to 7.02±0.00, 72.81±1.27 to 76.63±1.35%, 3.90±0.98 to 4.12±1.96 x 109/mL, 86.16±0.55 to 89.38±0.80% and 88.06±1.13 to 90.97±0.81% respectively. However, only the variations in proportion of spermatozoa with normal morphology and proportion of live spermatozoa among the ecotypes were significant (P<0.05). The semen volume, pH, sperm motility, sperm concentration, proportion of spermatozoa with normal morphology and proportion of live spermatozoa among the two age groups varied from 0.44±0.03 to 0.52±0.03mL, 7.01±0.00 to 7.02±0.00, 73.88±1.13 to75.92±0.99%, 3.80±0.45 to 4.28±0.32 x 109/mL, 87.02±0.58 to 88.15±0.64%, 88.27±0.77 to 89.83±0.77% respectively. However, only the variations in semen volume among the two age groups were significant (P<0.05). The Pearson correlation coefficients between semen volume and other semen quality characteristics were mostly low to medium with positive values ranging from 0.01-0.51 between semen volume and sperm motility and between morphological normal spermatozoa and proportion of live spermatozoa, respectively. Although there is minimal variation in semen quality among ecotypes and age groups, all the ecotypes might still be used in breeding purposes to maintain native chickens, because the results found were within the reference range for chickens.