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Summary Furty‐seven A. I. bulls between 15 and 26 months of age, were used to study the relationship between sperm morphology in fresh semen and fertility (56‐day non‐return rate) in frozen semen following 11,749 inseminations. The sperm morphology was studied in two freezing operations/bull in a phase‐contrast microscope and morphological abnormalities were recorded as a percentage of the total number of counted spermatozoa. Morphological categories used in this study were abnormal heads, detached heads, nuclear pouches, abnormal acrosomes, proximal cytoplasmic droplets, abnormal midpieces and abnormal tails. The greatest mean value recorded for the investigated categories was found for abnormal heads (3.8%) but the majority of morphological abnormalities only occurred in about 1 % of all studied spermatozoa. Breed effects were found, with a somewhat higher incidence (p ≤ 0.05‐0.01) of sperm abnormalities and poorer fertility among SRB than among SLB bulls. Despite the low frequency of sperm abnormalities, statistically significant (p ≤ 0.05‐0.001) correlations were found between abnormal heads, nuclear pouches and proximal cytoplasmic droplets assessed in fresh semen and fertility (56‐day non‐return rate) of frozen semen.

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ContentsTwenty ejaculates from _ve dairy AI!bulls were used to compare\ in a split!sample experiment\ the fertility ð45 day! non!return!rate "NRR# from more than 03999 AI# and sperm viability post!thaw of semen diluted with an egg yolk! "Tri! ladyl þ # or soybean!based "Biociphos!Plus þ # commercial extender[ The in vitro evaluations were divided in two experi! ments[ Experiment 0 "n 19# included post!thaw evaluations of motility "subjective and computerized#\ membrane integrity "CalceinAM:EthD!0\ SYBR!03:PI\ and osmotic resistance testÔ RT#\ and capacitation status "CTC:EthD!0#[ Experiment 1 "n 09# included evaluations of the capacitation!"CTC:EthD! 0# and acrosome status "FITC!PSA:EthD!0# during incubation with:without a challenge with solubilized zona pellucida pro! teins "SZP#[ No signi_cant di}erence in the fertility "58[0 2 9[7 versus 58[1 2 9[7# results was found between the two extenders[ In experiment 0\ the computerized motility evaluations post! thaw "CASA# showed higher values for Biociphos!Plus þ pro! cessed semen for the velocity patterns and lateral sperm head displacement[ After 5 h at room temperature "19Ð11>C# all the CASA motility patterns were signi_cantly higher for Biociphos! Plus þ [ The proportion of spermatozoa with intact membranes assessed by CalceinAM was signi_cantly higher in Biociphos! Plus þ "p ³ 9[990# compared to Triladyl þ \ but such di}erence was not seen when using SYBR!03 or the ORT!assay[ When using the CTC:EthD!0 assay\ a lower proportion of acrosome reacted "AR# spermatozoa post!thaw "p ³ 9[90# was found in Biociphos!Plus þ processed semen\ as well as a tendency "p ³ 9[96# for a higher number of uncapacitated spermatozoa[ In experiment 1\ the proportion of uncapacitated spermatozoa was signi_cantly higher for Biociphos!Plus þ when semen was incubated "27>C and 4) CO 1 # without SZP at both 9 "p ³ 9[990# and 29 min "p ³ 9[94#[ Concomitantly\ Triladyl þ showed a higher percentage of capacitated spermatozoa at 9 "p ³ 9[90#\ 29 "p ³ 9[94# and 019 min "p ³ 9[94#[ A higher "p ³ 9[94# incidence of AR!spermatozoa was seen in Triladyl þ at the beginning of the incubation with SZP[ No signi_cant di}erence between extenders was detected for the acrosome status by the FITC!PSA!assay[ Incubation with SZP induced acrosome reaction of capacitated spermatozoa in both extenders\ which was detected by CTC and FITC!PSA assays[ In conclusion\ fertility was not a}ected by Biociphos!Plus þ when 04 × 09 5 of spermatozoa per AI dose were inseminated[ The _nding that higher frequencies of spermatozoa seemed more membrane stable post!thaw\ when frozen in Biociphos! Plus þ \ might indicate that this extender better protects the sperm viability compared with Triladyl þ [