A total number of 30 primiparous New Zealand White (NZW) pregnant rabbit, does were used in the current study to evaluate the changes of leptin levels during pregnancy in relation to each of physiological, reproductive and productive performance of does. Rabbits aged 5-6 months and weighed 3098.15 ± 20.24 g on average. Plasma biochemical parameters were determined at 13, 21, 28 days of pregnancy and at kindling day. Also, the does weigh, litter size, litter weight, milk yield and milk compositions were determined.
The results showed that,leptin levels increased slightly during gestation days, reached to the highest value (2.91 ng/ml) at day 28 of pregnancy and then declined at delivery day. Furthermore, leptin levels positively correlated with GST and negativelywith H2O2and MDA. Both H2O2and MDA were at the lower levels day 28 of pregnancy when leptin recorded its highest level (2.91 ng/ml). This clear that, leptin may play an important role in the system of antioxidant and free radicals. Blood proteins (TP, Alb and A/G, except Glb) were associated positively with leptin levels. This indicates that, leptin may interfere with blood proteins metabolism. Furthermore, leptin correlated negatively with plasma TL, TG and Glu which declined during gestation days and recorded their lower values (154.47,135.11 and 106.55 mg/dl, respectively) at day 28 of pregnancy. Additionally, leptin also was in a negative relationship with BUN levels, which were higher than normal range at days 13 and 21 of pregnancy. Afterwards, significantly declined at day 28.Also, CR levels correlated negatively with leptin levels. The liver enzymes (AST and ALT) were in a negative relationship with leptin levels. These enzymes declined during gestation days recorded their lower values at day 28 of pregnancy, respectively. Also,body weight of dam, litter weights and size were positively associated with leptin levels, because leptin play an important role in regulating BW by controlling the mass of adipose tissue. Additionally, the results showed a negative relationship between leptin levels and milk yield, MF, ML and milk ash. In contrast, MP, MTS and MSNF were associated positively with leptin levels.
In conclusion, the study clarified the importance of leptin levels during pregnancy period in primiparous rabbit does through its relationship with blood parameters and the productive performance of both dam and the kits. However, its relationship with these parameters need further studies, especially, studies on rabbits are very rare and most of them have been conducted on other species.