Management of the storage of cryopreserved sperm on dairy cattle farms

Resumo

26 liquid nitrogen tanks were selected from different dairy cattle farms. Three sperm doses were introduced in a frequently used canister, while another three straws were deposited in another canister that did not contain any sperm doses, to determine whether the refilling with liquid nitrogen had been done appropriately. Then, 10 sperm doses belonging to the same freezing lot were stored in our laboratory under ideal conditions to be used as control doses. After certain time period, the doses were collected from the farms and were analysed to obtain data about their total sperm motility and the individual kinetic parameters of each sperm. Four sperm subpopulations (SP) with different patterns of motility were identified using a cluster multivariate analysis. The results show that the mean total sperm motility has hardly decreased for the doses stored in the frequently used canister (45.2 ± 6.9%) in comparison with the doses stored in the rarely used canister (46.9 ± 59.0). However, the decrease in total motility was greater when compared with the control doses (59.0%). As for the sperm SP, (SP4 rapid and progressive sperm) which contained 31% of the total of sperm (control doses), differed the most when control doses were compared to straw stored in farm tanks. The percentage of the latter was reduced to 10 % after being stored in the tanks of the farms for 7 mo. Such damage in SP 4 is progressive and cumulative and would probably reduce drastically compromising the fertility of the aforementioned sperm doses.