Background: Cottonseed cake is used as source of proteins for animal feeding. However, cotton seeds present a substance with
toxic potential in their composition, the gossypol. Gossypol is a compound highly reactive that binds rapidly to different
substances, including minerals and amino acids. In males, gossypol promotes reduction of motility and spermatozoid
concentration. The present work evaluated the effects on spermatogenesis of male sheep fed cottonseed cake.
Materials, Methods & Results: Twelve male adult Santa Inês sheep with high genetic standard were used. They were separated
into two groups, the first was fed with 0.5 kg/animal/day cottonseed cake (treated group) and the second was fed with 0.5 kg/
animal/day corn meal (control group), both for 120 consecutive days. Cottonseed cake or corn meal was offered moiled. At the
end of the experimental period, samples of semen were collected for laboratorial determination of quality, including density
and spermatic pathologies. Sample collection was done be use of artificial vagina. Semen ejaculates were collected directly
into a graduated tube, the volume recorded, and samples were immediately examined. Motility was estimated by examining
a fresh drop of semen on slide without cover slip with a light microscope at 100x magnification. Motility was scored as: 1: little
or no individual spermatozoa motion with no wave; 2: slow motion with no swirl; 3: rapid motion with slow swirl and eddies;
and 4: vigorous progressive motion with rapid swirl and eddies. From each ejaculate, 10 μL of semen were suspended in 2 mL of
10% buffered formol saline solution and spermatozoids were counted in a Neubauer chamber using a light microscope. Total
spermatozoids counts were obtained by multiplication of spermatozoids concentration by semen volume. The percentage of
abnormal sperm was calculated for a total of 200 sperm from each sample with a microscope under 1000x magnification. Data were
compared using unpaired t test, with the level of significance set at P < 0.05. In the present study none of the experimental animals
from both groups presented any clinic alteration, during the evaluated period. No statically significant differences were found at
semen volume, spermatozoids concentration, total spermatozoids, motility and percentage of abnormal spermatozoids between
the two groups.
Discussion: The obtained results revealed that administration of cottonseed cake to sheep did not affect the quality of
produced semen. During the process of oil extraction, it occurs binding of gossypol to proteins from the seeds, probably in the
radical epsilon-amine from lysine. Gossypol bound to proteins is not absorbed by the gastrointestinal tract of the ruminants,
and this form is considered non toxic. Moreover, ruminal microbia of developed animals is capable to detoxify the gossypol
by binding it to proteins. In this study, one possible explanation for the absence of deleterious effects in sheep is that the free
gossypol concentration in cottonseed cake is low because of the thermic treatment performed during the oil extraction process.
Further studies are necessary to determine the residual amounts of gossypol, both free and bound forms, at cotton residue.
Therefore, we conclude that, based on our experimental conditions, the cottonseed cake can be administered, at the concentration
and time evaluated in this study, to male adult sheep without compromising their spermatogenesis.
