Effect of Season on Sexual Behaviour, Semen Quality and Fertility of Nubian, Saanen and Crossbred Bucks in Sudan

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Date
2015-04-01
Authors
Abdelhai, Elsir
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UOFK
Abstract
The present study was conducted to investigate the effect of season on reproductive traits of Saanen bucks in comparison to Nubian and Nubian x Saanen Crossbred bucks. The study was carried under the normal climatic conditions of Sudan, in order to provide necessary data to use these bucks in genetic improvement programmes, using artificial insemination technique. Eleven mature bucks (4 Nubian, 3 Saanen and 4 Nubian x Saanen Crossbred) were used in this study to prepare semen samples which were collected with an artificial vagina. Sexual behaviour of the bucks was assessed by recording the reaction time to mating. Body measurements including scrotal circumference, heart girth and body condition scores were recorded throughout the study period. The study examined the relationship between season and sperm characteristics (volume of ejaculate, concentration, physical appearance, mass activity, sperm motility percent, post-thaw sperm motility, dead sperm percent and abnormal sperm percent). Semen samples were diluted with either Tris or skim milk-based extenders. The diluted semen was preserved at +5 0C and was evaluated for motility at 0 hour, 24 hours and 48 hours. Another proportion of the semen was preserved in liquid nitrogen at – 196 0C and examined for sperm motility after 48 hours. A total of 90 female goats (60 Nubian and 30 Nubian x Saanen Crossbred) were used in the fertility trial. The goats were selected and grouped according to the breeds of bucks used to prepare fresh and frozen semen. All groups were synchronized with intravaginal progesterone-impregnated sponges or with controlled internal drug release (CIDR) device for 12 days. At time of sponge withdrawal, all goats received an intramuscular injection of pregnant mare serum gonadotropin (PMSG) hormone. Following termination of treatment, the goats were artificially inseminated 48 hours latter with 0.5 ml of either fresh-diluted or frozen-thawed semen of Nubian, Saanen or Crossbred bucks. Conception rates were determined by radioimmunoassay (RIA) and ultrasonic means. 4 The results obtained indicated that sexual desire was significantly affected by breed. Nubian and Crossbred bucks showed the strongest sexual desire (43.23 ± 8.72 and 41.56 ± 9.54 seconds, respectively), while Saanen bucks showed the slowest sexual desire (56.77 ± 13.38 seconds). The influence of season on sexual desire was significant. The shortest reaction time was observed during autumn and winter, while during summer all bucks showed weak sexual desire. Complete lack of libido was observed among Saanen bucks during May and June. Sexual desire showed significant correlations with ambient temperature and daylight for Saanen bucks, while these correlatios for Nubian and Crossbred bucks were not significant. Scrotal circumference measurements were significantly affected by breed. The highest value was recorded among Saanen bucks (26.75 cm), while the lowest measurement (24.68) was observed among Nubian bucks, although in all breeds, scrotal circumference increased with age. Effect of season on scrotal circumference revealed significant difference in all the three breeds of bucks. The highest measurements were recorded during summer, while the lowest measurements were observed during winter. The body growth, measured by recording the heart girth (HG) and body condition scores was significantly affected by breed. Although Saanen bucks recorded the highest measurements for heart girth and body condition score (93.20 and 4.12, respectively), Crossbred bucks recorded the faster rate of growth among the different groups. Effect of season on body growth measurements revealed non significant difference among Saanen bucks, while for Nubian and Crossbred bucks, it was significant. Semen characteristics of all groups were not affected by breed except for volume of ejaclate. Saanen bucks produced the greatest value (0.98 ml), while the smallest volume was recorded for Nubian bucks (0.82 ml). The influence of season on ejaculate volume was significant. Greater ejaculate volumes were observed during summer and autumn, while during winter, the smallest ejaculate volumes were recorded for the three groups. The influence of season on sperm cell concentration was significant. Higher values were observed during autumn (2.55 ± 0.62x109, 2.55 ± 0.92x109 and 2.54 ± 0.40x109 for Nubian, Saanen and Crossbred bucks, respectively), while the lowest sperm concentration values were observed during summer. 5 Physical appearance of semen showed thick-creamy semen during autumn, while thin milky semen was observed during summer for the three breeds of bucks. Influence of season on mass activity of semen was significant. Mean values of mass activity scores were higher during autumn (3.39 ± 0.49, 3.42 ± 0.50 and 3.32 ± 0.47, for Nubian, Saanen and Crossbred bucks, respectively), while a progressive decrease was observed during summer. Higher values of sperm motility (65.53 ± 5.89%, 65.59 ± 8.00% and 67.50 ± 6.45% for Nubian, Saanen and Crossbred bucks, respectively) were observed during autumn, while the lowest values were observed during summer. The influence of season on post-thaw sperm motility was significant. Semen frozen during autumn and winter (Nubian: 29.64 ± 6.07% and 33.10 ±11.89%, respectively; Saanen: 36.42 ± 10.14% and 35.33 ± 9.15%, respectively and the Crossbred: 30.00 ± 10.04% and 35.00 ± 12.03%, respectively) had the highest values. During summer lower mean values were observed (27.18 ± 9.65%, 20.00 ± 5.64% and 23.43 ± 8.31% for Nubian, Saanen and Crossbred bucks, respectively). The influence of season on the incidence of dead spermatozoa was significant. Lower values of dead spermatozoa were recorded during autumn (10.25 ± 2.78%, 10.52 ± 3.80% and 10.25 ± 4.23% for Nubian, Saanen and Crossbred bucks, respectively). Highest percentages of dead spermatozoa were observed during summer for the three breeds of bucks (16.37 ± 1.20, 17.25 ± 3.33 and 16.87 ± 3.30, respectively), while winter showed intermediate values with regard to this characteristic. A significant negative correlations (r = - 0.80, - 0.80 and – 0.70) between percentage of dead spermatozoa and humidity for Nubian, Saanen and Crossbred bucks, respectively were obtained. All types of sperm abnormalities studied showed significant seasonal variations. Mean values of abnormal spermatozoa (morphologic defects), followed the same trend of dead spermatozoa. It was lower during autumn (7.00 ± 1.98%, 6.85 ± 2.68% and 7.67 ± 3.42% for Nubian, Saanen and Crossbred bucks, respectively), while the poorest quality semen was collected during summer for the three breeds of bucks. A significant negative correlations (r = - 0.78, - 0.86 and – 0.67) between percentage of abnormal spermatozoa and humidity for Nubian, Saanen and Crossbred bucks, respectively were recorded. 6 In cold stored semen, sperm motility consistently dropped after one day of preservation, although its mean percentage after chilling for 48 hours was 43.12 in Tris-based extender and 42.71 in skim milk extender. In frozen stored semen, sperm motility remained at 31% or more in Tris-based extender, while it dropped to 10.85% in skim milk extender. The fertility of the sperms assessed by the conception rates of goats, was not significantly different after artificial insemination with fresh-diluted (46.66%, 53.33% and 53.33% for Nubian, Saanen and Crossbred bucks, respectively) or with frozen-stored semen (40%, 46.66% and 46.66% for the three breeds, respectively). It can be concluded that the season affected significantly almost all parameters measured. The best semen was produced during autumn and winter. Fresh diluted semen can be preserved at + 5 0C for up to 48 hours using Tris or skim milk extenders, whereas frozen stored semen can be preserved successfully using Tris-based extender. Tris-based diluent with 2.5% egg yolk content was superior for freezing goat semen than skim milk extender. Frozen stored semen of Nubian, Saanen and Crossbred bucks, raised under the climatic conditions prevailing in Sudan can be used successfully for artificial insemination programmes.
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Keywords
Sexual Behaviour, Semen Quality ,Fertility,Crossbred Bucks,Sudan,Nubian
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