The present study aimed to determine the effects of zinc oxide nanoparticles (ZnO-NPs), thyme oil (THO), or their combination on the nutrient digestibility coefficients, reproductive parameters, and some blood metabolites of male Californian rabbits. One hundred rabbits, 29-weeks of age (initial body weight 3.48 ± 0.08 kg) were randomly distributed into four groups, 25 rabbits each. Treatment groups were fed a control diet, a control diet supplemented with ZnO-NPs (100 mg/kg), THO (500 mg/kg), or combination of ZnO-NPs (100 mg/kg) and THO (500 mg/kg). The feeding trial lasted for 35 days. Results showed improvements in dry matter, crude protein, ether extract, and crude fiber in ZnO-NPs, THO, and their combination treated groups compared to those of control. Furthermore, semen volume, sperm motility, vitality, and morphology were significantly improved (p < 0.01) in ZnO-NPs and THO groups rather than the control. Both ZnO-NPs and THO, as either individual or combined treatments significantly improved the serum alanine amino-transferase (ALT), aspartate amino-transferase (AST), urea, and creatinine compared to the control. Moreover, serum concentrations of testosterone were significantly increased in rabbits supplemented with ZnO-NPs, THO, or their combination compared to those of control (p < 0.05). In conclusion, ZnO-NPs, THO, or their combination improved the digestibility of nutrients, liver/ kidney functions, semen characteristics, and testosterone concentration in male rabbits.

Ninety six unsexed one-day old; Ross 308 broiler chicks were randomly divided into 4 treatment groups. Each treatment had 3 replicates with 8 chicks each. The chicks of each replicate were allocated in a cage in a windowless house. The experimental period was divided into two feeding phases, starter (0-3 weeks of age) and grower (4-6 weeks of age). The basal experimental diets had 23.33 and 20.42% crude protein and 3115 and 3162 Kcal ME/kg diet for the starter and the grower diet, respectively. Chicks in first treatment were injected muscularly with saline solution weekly and served as a control. Whereas, in treatments 2, 3 and 4 chicks were injected muscularly with 0.5, 1.0 and 1.5 mg of honey bee venom (BV) extract weekly till 5 weeks of age, respectively. Injection with BV decreased significantly (P<0.05) body weight (BW) at 3 weeks of age, average daily gain (ADG) during the period from 0-3 weeks of age and daily feed intake (FI) during the periods from 4-6 and 0-6 weeks of age. On the other hand, there were no significant differences (P>0.05) in BW at 6 weeks of age, ADG at 4-6 and 0-6 weeks of age, FI during period from 0-3 weeks of age, feed conversion ratio, haemagglutinin antibody titers against (SRBC), aspartate amino transaminase (AST) and alanine amino transaminase (ALT), serum total protein, albumin (Alb.), globulin (Glb.), (Alb./Glb.), cholesterol and total lipids. These data indicate that injection of broiler with BV extract by these doses did not adversely affect the productive performance and physiological traits However,BV extract has the ability to enhance the immune responses of broiler chicks. But more research is needed in future to evaluate the best dose and different supplementation methods.

The aim of the study was to evaluate the effect of a temporary quantitative feed restriction on growth performance, nutrient digestibility and carcass criteria of rabbits. A total of 80 weaned male Californian rabbits (30 d of age) were randomly assigned to four treatments of 20 rabbits each. The Control group was fed ad libitum during the whole experimental period (days 30-72 of age). For the three restricted fed groups the feed intake was reduced by 15%, 30% and 45% compared to the Control group, respectively. The feed restriction was applied after weaning and lasted for 21 d. Thereafter, at 51 d of age, in all treatments the feed supply returned to ad libitum intake till 72 d of age (AL period). The feed restriction decreased the body weight gain of rabbits (during the restriction period and the whole experimental period, p < 0.001) and improved feed conversion ratio during all tested periods (p < 0.001). In the AL period, the daily body weight gain of all groups was similar. After the AL period, the digestibility of all measured nutrients was significantly higher for animals fed restrictively. Furthermore, feed restrictions significantly decreased the proportion of perirenal and scapular fat and increased relative weight and length of the gastrointestinal tract. Therefore, it can be concluded that the applied feed restriction improved feed conversion, nutrient digestibility and reduced fat at the slaughter age of Californian rabbits, but the reduced body weight gain could not be compensated by a subsequent ad libitum feeding for 3 weeks.

The ability of the animal gut to absorb the trace elements and other nutrients, therefore, improving the growth performance of animals. Nanoparticles of Selenium (Nano-Se) promote growth performance of rabbits and it can act as antioxidants, antibacterial agents, improving the immunity system of the rabbits. Moreover, Se is one of the critical nutritional factors necessary for the normal functioning of the immune system and maintenance of gut health, growth, and organ functions. Numerous studies have demonstrated that a deficiency in Se could lead to serious disruptions in animal performances such as growth, digestion, liver damage, pancreatic fibrosis, cystic ovaries, and thyroid metabolism dysfunction. Furthermore, sufficient Se supplementation in rabbits tends to maintain good health and productive performance. The levels of Se in the rabbit diets vary widely according to dietary ingredients and selenium supplementation, ranging from 0.05 to 2.0 mg/kg diet. Since there are almost unlimited possibilities concerning the dosage of Se there is still more research needed. This review gives an overview of the mode of action, recommendation levels of Nano-Se, and their effects on growth performance, nutrient digestibility, carcass criteria and blood biochemical of rabbits.

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