The present study was designed to investigate, which source of added zinc (Zn) to the basal ration could optimize or increase the reproductive efficiency and maintain the health status of Rahmany ewes and their offspring. To achieve the objectives of the study, forty Rahmany ewes in the last two months of pregnancy with average body weight (49.98±0.64 kg) and 3 years old were used until two months after parturition. Animals were distributed into 4 groups (10 ewes in each). The first experimental group was used as a control and was fed a basal ration without zinc supplementation, and other three groups were fed a basal ration supplemented with 50 mg Zinc in the form of Zinc sulphate (Zn-S) or Zinc methionine (Zn-MS) or Nano -Zinc oxide (Nano-Zn) per kg concentrate feed mixture(CFM), respectively.
The basal ration in this experiment consisted of 50% roughages (clover hay or Egyptian clover and rice straw) and 50% concentrates (CFM + barley grains). The basal ration was formulated to meet the nutritional requirements of pregnant ewes (NRC, 2007). The daily ration of each ewes consisted of one Kg CFM + 300 g barley grains + 4.0 Kg Egyptian clover (fresh) + 400 g rice straw. CFM contained: 38% yellow corn, 17% sunflower meal, 39.0 % wheat bran, 3.0 % molasses, %2.0 lime stone and 1.0 % table salt. The reproductive performance traits, some biochemical blood serum parameters, milk yield and milk composition of Rahmany ewes were used as indices for the study.
Results of the study showed that chemical analysis of basal ration recorded: 2.471 kg DM; 15.2 % CP; 3.2 EE; 19.2 % CF; 9.6 % ash, 52.8 % NFE, 0.86% Ca, 0.40% P and 51mg Zn/ kg DM.
Lambs weights at birth and at 15, 30, 45 and 60 days of age and placenta weights were significantly heavier (P < 0.05) with ewes fed supplemental Zn-M or Nano-Zn than those fed the basal ration only (control) or those fed the supplemental Zn-S. Lambs of the control ewes recorded the lightest weights compared with other groups. Litter size and viability (%) of lambs were insignificantly better with the ewes fed supplemental Zn than those fed the basal ration without Zn supplementation (control).
The serum total protein (TP) and globulin (Glob) were higher (P < 0.05) in ewes fed supplemental Zn than those fed the basal ration without Zn supplementation (control). The ALT activity level, also in blood serum tended to be higher (P < 0.05) at lambing and after 60 days from lambing in ewes fed supplemental Zn than those fed the control ration. The levels of serum AST, urea-N and creatinine showed insignificant difference among the ewes groups. All the determined blood serum components in all the ewes groups were within the normal range of healthy sheep. Zinc concentration in the blood tended to be the highest (P < 0.05) with ewes fed Nano-Zn and Zn- M, indicating that Zn is more absorbed from the gastrointestinal tract when Zinc is in the form of Nano-Zn or Zn- Methionine.
Milk yield (kg) was greater (P<0.05) with ewes fed supplemental Nano-Zn or Zn-M than those fed the control basal ration or supplemental Zn-S. Zinc supplementation from different sources had no significant effect on milk constituents of ewes including, crude fat, crude protein, lactose, total solids and solids not fat at 15,30,45 and 60 days from lambing .
In conclusion, Zinc supplementation to the daily ration of pregnant ewes in the form of Nano-Zn or Zn- Methionine at level of 50 mg / kg concentrated feed mixture (CFM) can be recommended to improve reproductive performance and milk production of Rahmany ewes and maintain their health status during pregnancy and lactation.