Effect of nano-ZnO, compared to ZnO and Zn-methionine, on performance, nutrient status, rumen fermentation, blood enzymes, ferric reducing antioxidant power and immunoglobulin G in sheep

Abstract

This study was conducted to assess the effect of nano-ZnO, compared to ZnO and Zn-methionine, on dry matter (DM) intake (DMI), performance, nutrient status, digestibility, rumen fermentation, microbial nitrogen (N) synthesis (MNS), blood enzymes, ferric reducing antioxidant power (FRAP) and immunoglobulin G (IgG) in sheep. Thirty-six healthy male Shal sheep were divided into four experimental groups (n = 9) in a completely randomized design, and assessed for 40 days. The control animals received the basal diet without Zn supplementation, containing a native Zn content of 22.6 mg/kg DM. Other sheep were fed with the diets containing 28 mg supplementary Zn/kg DM in the form of ZnO, Zn-methionine or nano-ZnO. The DMI of sheep receiving Zn-methionine was higher (P = 0.035) than the control group, but was similar among the Zn-supplemented groups. Although supplementation of the basal diet with Zn increased (P < 0.05) the digestibility, rumen total volatile fatty acids (VFA), average daily gain and feed efficiency, the chemical forms of Zn did not affect these variables. The intake, daily absorption, retention and blood concentration of Zn were not affected by using nano-ZnO instead of ZnO and Zn-methionine. The animals receiving Zn-methionine had higher (P = 0.019) rumen fluid Zn than the ZnO fed sheep. Compared to the control diet, the Zn supplementations increased retained N (P = 0.037) and decreased rumen ammonia-N (P = 0.046). Using nano-ZnO instead of ZnO and Zn-methionine had no effect on rumen ammonia-N, retained N and MNS. The blood urea-N (BUN) concentration was lower (P = 0.027) for the Zn-methionine and nano-ZnO fed animals versus the control and ZnO groups. The nano-ZnO and Zn-methionine fed sheep had higher (P < 0.05) rumen and blood FRAP and Zn absorbability than the ZnO group. The blood IgG concentration was higher (P = 0.028) for the Zn-methionine and nano-ZnO fed animals versus the control sheep, and nano-ZnO group versus the ZnO fed animals. There were no differences among sheep in terms of the ruminal pH, individual VFA proportions and protozoa counts, Cu status and blood alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase. Overall, using nano-ZnO in the diet of sheep had advantages over ZnO in terms of increasing the Zn absorbability, rumen and blood FRAP and blood IgG, and decreasing BUN. However, there were no differences between the animals consuming nano-ZnO or Zn-methionine.