Relationship of bull fertility to sperm nuclear shape.
The relationship between sperm nuclear shape and bull fertility was determined. Two groups of bulls, 3 per group, were selected. Bulls differed in fertility based on lifetime nonreturn rates. Digital images of propidium iodide-stained sperm from each bull were collected and shape-evaluated by Fourier harmonic amplitudes 0 to 5. A discriminant function (P < .05) was constructed based on harmonic amplitudes and the 2 fertility groups. When individual sperm were classified as being of high or lower fertility, the percentage of each bull's sperm placed in the high-fertility group had a linear relationship (r = .89, P < .05) with fertility. To construct a plot of mean sperm shapes, a novel technique to automatically orient and identify the anterior tip of the sperm head was developed. The mean nuclear shape of high-fertility sperm was more elongated and tapered than those of lower fertility. A discriminant function (P < .05) was also constructed that separated the 6 bulls into 2 groups based only on the harmonic amplitudes or sperm nuclear shape. The bulls were correctly classified into the 2 fertility groups. A comparison of sperm chromatin structure analysis (SCSA) and harmonic amplitudes found that overall size variance, anterior roundness, and posterior taperedness of sperm nuclei were related to chromatin stability (P < .05). Some of the differences observed in sperm nuclear shape between the high- and lower-fertility bulls may be explained by varying levels of chromatin stability. However, sperm nuclear shape appears to contain additional information from chromatin stability alone. In this particular study, with 6 bulls, all with good chromatin quality, sperm nuclear shape was a better predictor of bull fertility.
Ostermeier
G C
GC
Department of Animal Sciences, University of Wisconsin-Madison, USA.
Sargeant
G A
GA
Yandell
B S
BS
Evenson
D P
DP
Parrish
J J
JJ
D000818:Animals; D002417:Cattle; D002467:Cell Nucleus; D002843:Chromatin; D005298:Fertility / Q000502:physiology*; D005583:Fourier Analysis; D007091:Image Processing, Computer-Assisted; D008297:Male; D011237:Predictive Value of Tests; D012661:Semen / Q000166:cytology; D013094:Spermatozoa / Q000648:ultrastructure*
D002843:Chromatin