Aims: The present study was conducted to clarify the effect of Kemzyme or Bentonite and their mix as feed additives on the main semen characteristics, testicular enzyme markers, plasma testosterone level and fertility indices of bucks.
Study Design: Twenty- four mature male New Zealand White bucks were equally divided into four groups (6 in each). The first group was the control group (C) the animals were kept untreated and were fed the basal diet without additives. The second group (K) was supplemented with 0.1% “Kemzyme”, a multi-enzyme blend of Kemin Agrifoods Europe, composed of cellulases, amylases, proteases and lipases. The third group (B) the animals were supplemented with 2% sodium bentonite  which purchased from (Morgan for chemicals – Egypt) while the fourth group (KB) was supplemented with 0.1% Kemzyme plus 2% sodium bentonite. Doses of supplemented additives were mixed with the basal ration pellets.
Place and Duration of Study: The study was conducted in the experimental rabbitry of Physiology Department, Faculty of Veterinary Medicine Cairo University. The treatment lasted for 10 weeks to cover a complete spermatogenic cycle.
Methodology: The rabbits were housed individually in commercial cages (55×60×34 cm), equipped with automatic drinkers and j-feeders. Daily lighting regime was 10-12 hours photoperiod /day through both natural and fluorescent lighting. A commercial pelleted diet of 16.7% crude protein, 13.7% crude fiber and 2590 kcal of digestible energy per kg (Atmida Feed Company, Egypt) was offered ad libitum. Clean, fresh water was available all times. The diet subjected to chemical analysis according to . Kemzyme”, a multi-enzyme blend of Kemin Agrifoods Europe, composed of cellulases, amylases, proteases and lipases. Sexual activity of the bucks was evaluated through behavioural testing “mating test”. On the test day, a receptive female was introduced to the male’cage and the following behavioral parameters were recorded according to  and  during 10 min testing period for each buck: latency to mount, time from introduction of the female until the first mount with pelvic thrusting; mating latency “reaction time”, time from introduction of the female until the first ejaculation; interval between the first and second mating as a measure of libido. The previously mentioned parameters were measured in seconds using a stopwatch. Total number of mounts and ejaculations were also recorded. Each male in the different groups was tested three times, two days after each semen collection .At the beginning of the ninth week of the treatment, Semen collection was done by using a teaser female and artificial vagina that was locally fabricated as described by  Semen was collected weekly for three consecutive times and in every collection two successive ejaculations (with a lag of 15 min.) were obtained from each buck between 8:00 to 10:00 h to ensure optimum quality of semen obtained [6,7]. The volume of each ejaculate was recorded (using a graduated collection tube) after removal of the gel mass. A weak eosin solution  was used for evaluation of sperm concentration by the improved Neubauer haemocytometer slide (GmbH & Co., Brands twiete 4, 2000 Hamburg 11, Germany). Total sperm output was calculated by multiplying semen ejaculate volume and semen concentration. Assessment of live, dead, and abnormal spermatozoa were performed using an eosin–nigrosin blue staining mixture . The percentages of motile sperm and motility grade were estimated by visual examination under high-power magnification (40×) using an ordinary microscope with heated stage. Motility was scored as follows: 0 = no movement; 1 = twitching, no forward progressive movement (fpm); 2 = slow fpm; 3 = good fpm; and 4 = fast fpm.The two motility parameters were combined to yield; Sperm motility index: SMI = percentage motile X motility grade  Total number of motile sperm (TMS) was calculated by multiplying percentage of motile sperm and total sperm outputs.Seminal plasma was obtained by centrifugation of semen samples at 860 X g for 20 min, and was stored at −20°C until analysis. The activities of seminal plasma lactate dehydrogenase /LDH , Alkaline phosphatase / ALP  and Gamma glutamyle transferase /GGT  were measured spectrophotometerically by using kinetic mode. Total lipids were also measured in the seminal plasma according to method of . For evaluation of their fertility parameters, bucks of the different groups were bred with 24 receptive nulliparous female rabbits and their parameters were recorded for each group according to  kindling rate, total born and total born alive litter also stillborn kits were monitored,Blood samples were collected from the ear vein of all animals in the morning before accesses to feed and water. Heparin was used as anticoagulant.
Plasma was obtained centrifugation of samples at 860×g for 20 min and was stored at -20°C until used for determination of total testosterone [16,17]. Data of the experiment for all variables were subjected to ANOVA as a completely randomized design according to . Means were compared by Least Significant Difference (LSD) test at 0.05 significant level .
Results: The current result indicated that;significant sexual performance and higher libido of rabbit bucks supplemented with 0.1% “Kemzyme”, a multi-enzyme blend of Kemin Agrifoods.
Conclusions: Kemzyme supplementation in bucks was associated with improved sexual activity indices, improved semen parameters and steroidogensis. Its application as fertility enhancer should not be neglected. Bentonite, although it was claimed to have a growth promoting effect, its influence on animal sexuality and fertility was unsatisfactory. Practically, it could be considered that (K) supplementation is a good reproductive promotant tool in the field of rabbit production.
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