Andrological characteristics of tropical milking criollo bulls

Resumen

Objective: To assess the testicular and semen characteristics in Criollo Lechero
Tropical (CLT) bulls in the subhumid Mexican tropics.
Design/methodology/approach: Eight bulls were included in the study and distributed
in two groups: G1 (n=5): young bulls and G2 (n=3): adult bulls. All bulls were managed
under grazing and were evaluated throughout one year. From each bull the following
measurements were taken once a month: live weight, body condition score, scrotal
circumference, and testicular width, length and volume. Semen was obtained every 3
months via artificial vagina. Semen variables evaluated in each collection were: aspect,
volume, mass and individual motility, and sperm concentration and morphology.

Results: Live weight and testicular measurements increased linearly during the study in
bulls from both groups. All bulls had scrotal circumference larger than the minimum
threshold value for cattle and semen of high quality.
Study limitations/implications: The low availability of CLT bulls prevented the
inclusion of a larger number of animals in the study. This low availability of animals
makes it necessary to establish standard values for testicular measurements and semen
characteristics in the CLT breed in order to select the best individuals as sires and
contribute to its conservation.
Findings/conclusions: The CLT bulls had good scrotal circumference and semen
quality since a young age and into adulthood. These traits make the CLT bulls an
important alternative for livestock breeding in the tropics.