Seasonal variation in semen characteristics of Chios and Friesian rams in Greece

Five Chios and five Friesian rams were used to study the effect of season o n semen production. Semen samples were collected with an artificial vagina. In spite of the large variation of most of the semen characteristics among rams of the two breeds, seasonal variation in semen quantity (volume, conc entration and total number of spermatozoa per ejaculate) and quality (perce ntage of motile spermatozoa, sperm progressive motility and percentage of a bnormal spermatozoa) were significant (P < 0.05). The best semen was produc ed mainly during autumn and the worst during spring (semen volume: 1.47 mi in Chios and 1.48 mi in Friesian rams versus 1.24 mi in Chios and 1.07 mi i n Friesian rams; percentage of abnormal sperm: 5.66% in Chios and 5.42% in Friesian rams versus 8.22% in Chios and 7.75% in Friesian rams; total sperm /ejaculate (x 10(9)): 7.05 in Chios and 6.74 in Friesian rams versus 4.09 i n Chios and 4.05 in Friesian rams). The magnitude of these seasonal effects was not sufficient to prevent rams from being used for breeding throughout the year. However, the existence of differences among rams within each bre ed in semen quality and quantity makes it necessary to perform a semen eval uation on individual basis in order to select the best males before they ar e used for breeding. (C) 2000 Elsevier Science B.V. All rights reserved.