INFLUENCE OF BREED, AGE, AND EJACULATION FREQUENCY ON BOAR SEMEN COMPOSITION

Abstract

Seven semen characteristics were studied in two ejaculates collected at 24-h intervals from each of 41 Yorkshire (body weight 86 ± 6 kg) and 54 Lacombe (body weight 95 ± 8 kg) boars between 21 and 26 wk of age (group 1), and from each of 56 Yorkshire (body weight 94 ± 7 kg) and 47 Lacombe (body weight 107 ± 10 kg) boars between 27 and 31 wk of age (group 2). Means for certain semen criteria of the Yorkshire and Lacombe boars in group 1 were, respectively: semen volume 180 ml, 184 ml; sperm per ml 111 × 10 6 , 104 × 10 6 ; total sperm per ejaculate 15.9 × 10 9 , 13.9 × 10 9 ; motility 58%, 53%. Means for these criteria of group 2 Yorkshire and Lacombe boars were, respectively: semen volume 194 ml, 199 ml; sperm per ml 202 × 10 6 , 126 × 10 6 ; total sperm per ejaculate 29.5 × 10 9 , 17.8 × 10 9 ; motility 66%, 55%. Group 1 boars had fewer sperm per ml (P < 0.01), fewer total and motile sperm per ejaculate (P < 0.01), and fewer progressively motile sperm (P < 0.05) than group 2 boars. First ejaculates differed (P < 0.01) from second ejaculates for all criteria measured except percent motile sperm. In general, Yorkshire boars between 21 and 31 wk of age had better quality semen, as measured by sperm per ml and motile sperm per ejaculate, than Lacombe boars. A third ejaculate was collected 24 h after the second from 33 Yorkshires in group 1 and from 17 Yorkshires in group 2. Most semen criteria showed significant changes from first to second and from second to third ejaculates, but correlations among ejaculates for all criteria were significant. Nine 36-wk-old, six 86-wk-old, and seven 139-wk-old Yorkshire boars were ejaculated at 72-h intervals for 63 days, followed by daily ejaculations for 13 days. Mean semen criteria for the 36-, 86-, and 139-wk-old groups on the 72-h collection schedule were, respectively: semen volume 170 ml, 368 ml, 404 ml; sperm per ml 209 × 10 6 , 128 × 10 6 , 146 × 10 6 ; total sperm per ejaculate 25.6 × 10 9 , 36.8 × 10 9 , 45.9 × 10 9 ; motility 79%, 79%, 79%. On the 24-h collection schedule the means for these criteria were, respectively: semen volume 157 ml, 277 ml, 316 ml; sperm per ml 93 × 10 6 , 39 × 10 6 , 56 × 10 6 ; total sperm per ejaculate 9.9 × 10 9 , 8.3 × 10 9 , 12.8 × 10 9 ; motility 79%, 80%, 78%. On an ejaculate basis, the three groups showed highly significant decreases in all semen criteria except gel volume and motility when the ejaculation interval was changed from 72 to 24 h. Sperm output per unit time was greater on the 72- than on the 24-h collection schedule.