EFFECT OF SUCCESSIVE EJACULATION ON THE SPERMIOGRAM OF WEST AFRICAN DWARF GOATS

EFFECT OF SUCCESSIVE EJACULATION ON THE SPERMIOGRAM OF WEST AFRICAN DWARF GOATS

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Introduction
The west African Dwarf Goat (WADG) is the predominant breed of goats found in the Southern part of Nigeria. The breed has the remarkable ability to make maximum use of roughages. Its preference for browsing on a wide variety of vegetation, its ability to withstand the extremes of tropical climate and its relative trypanotolerance account for its widespread distribution throughout West, Central and East Africa, India and Fiji (1,2,3).
Reports on base-line data of semen characteristics have been documented (4,5,6,7), while others (8,9) reported on the effect of frequent ejaculation on semen characteristics. The increasing need for the use of artificial insemination in WAD goats has created a greater demand for semen from superior progeny tested sires. Sexual preparation prior to ejaculation and high ejaculation frequencies increase the sperm output (10).
The objective of this study was to determine the level of morphological abnormalities that may occur following successive ejaculations. It is hoped that such information will be a useful guide in semen collection for artificial insemination.
Materials and Methods
Twenty healthy WADG aged between 2 to 4 years and weighing between 16 to 20kg were used in this study. They were randomly assigned to four groups of five bucks per group after equalization of weight. All animals were clinically examined and confirmed to be free from any obvious abnormalities of the palpable reproductive organs. They were housed in pens with concrete floors covered with wood shaving as litter.
They were allowed to graze in the morning (7:00h-15:00h) on pasture consisting of carpet grass (Axonopus compressors), guinea grass (Panicum Maximum), elephant grass (Pennisetum purpreum) and dries Cassava (Manihot esclentum) peelings and supplemented with a corn based concentrate ration in the evening. Water was provided ad libitum. Routine medication consisted of deworming with Albendazole¨ (Phenix, Belgium) at a dosage of 2ml/10kg body weight and vaccinated against PPR using Tissue culture Rinderpest Vaccine (NVRI, Vom, Nigeria). Animals were weighed weekly with a spring balance and scrotal circumference was determined at the widest part of the scrotum weekly.

Semen collection
Semen was collected by the electro-ejaculation (EE) method. In group A, semen was collected once a week for a period of eight weeks, while in group B semen was collected twice a week for a period of eight weeks, once a day for 21 days in group C, and twice daily at an interval of five hours for 21 days in group D. The pH of each ejaculate was determined using a pH-meter.

Semen examination
Colour and consistency were determined by visual assessment and volume of ejaculate read from a graduated collection tube. Sperm concentration was determined using the improved Neubauer haemocytometer after dilution in 0.05% formol-saline. Sperm mass activity, progressive motility, live-dead ratio and morphology were determined by conventional methods (11). Acrosomal integrity was determined in wells and Awa stained smears.
Morphological aberrations were determined from a total count of 400 spermatozoa in smears obtained with Nigrosin and Eosin for live-dead count. Sperm abnormalities were classified as described (12).

Data analysis
Data obtained was subjected to student’s t-test and chi-square test for the establishment of significance (13).

Results
The results of body weights, scrotal circumference and the spermatgram are summarized in Table 1. The body condition of the animals was not significantly influenced by the frequency of collection. The colour of the ejaculate was white/creamy at the start of treatment in all groups.
There was no change in ejaculate colour in groups A and B, and rather watery in groups C and D at the end of the experiment. There was no significant difference in the groups in ejaculate volume and mass activity although the volume tended to decrease with increase in rate of ejaculation. The percentage progressive motile spermatozoa were not affected by treatments.
The concentration per ml of spermatozoa was affected by treatment with group D being inferior (p<0.05) to the other groups, which were not different from each other. Expectedly, the total number of spermatozoa in the ejaculate followed the same trens observed in concentration.
Table 2 summarizes the morphological aberration to treatments. Group A with only weekly collection had the least of abnormalities especially head abnormalities. An increase (p<0.05) in abnormalities consequent on increased ejaculation was observed especially in groups C and D.

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Posted on ธันวาคม 18, 2012, in บทความ. Bookmark the permalink. ใส่ความเห็น.

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