Effect of different methods of AD3E supplementation on performance, fermentation, rumen protozoa, and blood metabolites of fattening lambs by in vivo and in vitro experiments

 Animals need vitamins A, D3, and E to improve their performance and health. Vitamin A has an active role in maintaining all epithelial cells in the body and plays an important role in bone growth. Vitamin D3 plays an important role in increasing the absorption of calcium and phosphorus, in addition to the formation and calcification of the bones in animals. Vitamin E is a fat soluble vitamin which is both a growth-promoting vitamin and is considered an antioxidant. These vitamins also play an important role in improving the immune system in ruminants. Ruminants cannot produce vitamins A, D3, and E in their body; therefore, to meet physiological requirements and maintain high production performance, they need to be provided with an exogenous regular intake of vitamins A, D3, and E in their diet. Several studies have been carried out on the effects of dietary or injectable vitamin AD3E supplements on fattening lambs. This study aimed to determine the effects of various forms of AD3E supplementation on growth performance, rumen fermentation, protozoa population, and blood parameters in Mehraban lambs by in vivo and in vitro experiments.

 The project comprised two in vitro and in vivo experiments. In this experiment, the in vivo growth parameters such as final body weight, total weight gain, average daily gain, average daily gain, dry matter intake, feed conversion ratio, the ruminal fermentation parameters such as pH, ammonia nitrogen, total volatile fatty acids, blood biochemical metabolites [blood urea nitrogen (BUN), cholesterol, triglyceride, glucose, albumin, HDL, LDL, and malondialdehyde (MAD)], protozoa count, and in vitro gas production, organic matter digestibility, methane gas production, metabolizable energy, and short-chain fatty acids were studied. This experiment consisted of a 14-day adaptation period and a 60-day experiment. Twenty Mehraban lambs (body weight of 41.3±0.5 kg) were divided into four groups with five replicates in each group using a completely randomized design. The treatments included 1) the control group received a base diet without vitamin supplements, 2) injectable vitamin AD3E, 3) rumen-protected vitamin AD3E as a part of concentrate, and 4) AD3E vitamin in drinking water. Feed intake and body weight of lambs were recorded weekly during the fattening period. The samples of blood and rumen liquid were collected from the lambs on the 30th and 60th days of the experiment.

 The results indicated that the gas production, digestible organic matter, metabolizable energy, and short-chain fatty acids were reduced due to vitamin AD3E supplementation compared with the control group (P<0.05). Growth performance was not different when supplemented with AD3E, but for the rumen-protected vitamin, the average daily increase was 48 g more than that in the control group. The feed conversion ratio showed a significant decrease in AD3E water-soluble vitamins compared with the control group (P<0.05). The pH was not influenced by experimental treatments. The ammonia concentration was higher in treatments 3 and 4 (P<0.05), and the protozoa count was reduced due to vitamin AD3E supplementation (P<0.05). The BUN serum concentration was lower in treatments 2 and 3 compared with other treatments (P=0.008). Vitamin supplementation with AD3E administered in water or its injection made a significant increase in cholesterol concentration (P=0.002). Blood concentration of triglyceride showed a significant increase in treatment 4 (P=0.007). Plasma concentration of HDL was lower in lambs who received rumen-protected AD3E compared to the control group (P<0.05). Experimental treatments did not affect plasma glucose, total protein, albumin, LDL, and MAD concentrations of fattening lambs (P>0.05). Plasma concentration of BUN on day 60 was higher compared to the 30th day in all treatments (P<0.05). However, plasma concentrations of triglyceride and glucose were lower on day 60 compared to the 30th day of the experiment in all groups.

 Results showed that vitamin AD3E had no significant effect on growth performance; however, it was greater in the vitamin group treated with rumen protection than in the control group. Gas production, protozoa population, and ammonia nitrogen decreased compared to control. Higher doses of vitamins, especially the rumen-protected vitamin AD3E, are recommended in larger sample sizes and for longer periods.