The objective of this study was to evaluate the relation between the physical and morphological characteristics of semen from Bos taurus taurus and Bos taurus indicus cattle, the age of the bull and semen collection periods. Observations were made on 42 bulls with ages ranging from 12 to 174 months in five classes: subspecies Bos taurus taurus - 12 to 36 months; 37 to 60 months, 61 to 84 months, 85 to 108 months and 109 to 138 months and subspecies Bos taurus indicus - 12 to 42 months; 43 to 72 months, 73 to 102 months, 103 to 132 months and 133 to 174 months, from 1993 to 1999. The analyzed characteristics were: semen volume, mass motility, sperm concentration, sperm motility, sperm vigor, abnormalities and acrosome integrity. The average of characteristics in each age class and collection month were used for the analysis process during the period from 1993 to 1999. The statistical multivariate techniques of clustering and principal components showed results that can help in selection of semen with better quality. The age classes 4 and 5 of Bos taurus indicus and the age class 5 of Bos taurus taurus were the most contrasting. For both subspecies, the wetter months showed the lowest semen quality. This result was more evident in Bos taurus taurus. The most contrasting semen characteristics were: sperm vigor, sperm motility, sperm concentration, acrosome integrity and tertiary abnormality.
clustering analysis; principal components analysis; semen quality
