S. M. H. Andrabi, S. Naheed, L. A. Khan and N. Ullah

Animal Sciences Institute, National Agricultural Research Centre.. Islamabad, Pakistan

Abstract   

    The aim of the present study was to investigate the. semen characteristics (volume, motility concentration and morphology) of crossbred (Friesian x Sahiwal; F x S) bulls maintained at Livestock Research Station of National Agricultural Research Centre, Islamabad. Moreover, sperm head, mid-piece and tail dimensions in crossbred (F x S) and pure-bred (Friesian and Sahiwal) bulls were also studied. Semen was routinely collected twice a week during the. months of June 1997 to May 1998 from seven crossbred (F x S;.No. 36, 37, 38,39, 40,41 and 42) bulls by means of prewarmed (42 °C) artificial vagina. Crossbred bulls No. 36 and 37 had the highest volume of semen (4.8 ml), whereas, bull No.40 yielded the lowest volume of semen (3.9 ml). Semen volume was high during August, September, October, November and December which averaged 4.96 ml and low in the remaining part of the year (4.06 ml). Mean semen volume was higher (P<0.05) in the first ejaculate than in the second ejaculate in .all. the crossbred bulls. Crossbred bull No.36 showed highest {P<0.05) sperm motility (61%), whereas bull No.40 and 42 expressed the lowest sperm motility (34 %). Mean sperm moti1ity was high from October to December which averaged 55% and low in rest of the year (44 %). Mean sperm motility was higher (P<0.05) in the first ejaculate than in the second ejaculate of all the crossbred bulls, Crossbred bulls bearing No.36, 37 and 39 had the highest concentration, of sperm in ejaculate10.81 x 10⁹/ml), while bulls having tag No. 38, 40, 41 and 42 yielded at least sperm concentration (0.63 x 10⁹/ml). Sperm concentration was high during most of the months (0.77 x ,10⁹/ml), while it was low in April, May and August (0.52 x 109/ml). Mean total sperm abnormalities were higher (P<0.05) in bull No.40 and 42 (39.15%) as compared with other bulls (25.46%). Total sperm abnormalities were high (P<0.05) during June and July (60%) than other months (December, January, February, March;' April and May) which averaged 19.6%. Sperm head, mid-piece and tail length was shorter (P<0.05) in 'crossbred (F x S) than pure-bred (Friesian and Sahiwal) bulls. The results of present study demonstrate that changes in semen characteristics of crossbred (F x S) bulls were observed to be occasioned by bull, month of semen collection or ejaculate number. There was a relative difference in sperm head, mid-piece and tai1 length of crossbred (F x S) and pure-bred (Friesian and Sahiwal) bulls spermatozoa. Therefore, it can be concluded that genetics and seasons (months) clearly contribute to semen characteristics of crossbred (F x S) bulls.

Key words: Crossbred bull, semen volume, sperm motility, concentration, morphology.