Physiological benefits of protected AD3E on nutrient digestibility, hematology, and small intestinal morphology and carcass characteristics in fattening lambs.

Adequate intake of fat-soluble vitamins, including vitamin A, D3, and E, is essential for fattening lambs due to their roles in immune competence, metabolic regulation, and antioxidant protection. Conventional diets often provide inconsistent levels of these vitamins, making supplementation necessary. The present study was conducted to investigate the effect of different levels of rumen-protected AD3E supplementation on performance, rumen fermentation, feed digestibility, quantitative carcass characteristics, and small intestinal morphology of fattening lambs. Twenty-four male lambs (4-month-old) with a body weight of 34.11 ± 2.2 kg were divided into three groups in a completely randomized design for 70 days. The experimental treatments included a control group fed a basal diet (without vitamin supplementation), a second group fed a basal diet plus 1 kg/t of vitamin AD3E, and a third group fed a basal diet plus 2 kg/t of vitamin AD3E. Growth performance, nutrient digestibility, rumen fermentation parameters, and carcass traits were evaluated. The results showed that the use of protected AD3E improved the daily weight gain and feed conversion ratio of male lambs in the two vitamin-receiving groups compared to the control group (P < 0.05).The final weight of lambs receiving the protected vitamin supplement was higher than that of the control group (P < 0.05). Digestibility of nutrients remained unaffected. In comparison with the control group, rumen protozoa (total population and Entodinium) significantly increased in lambs that received vitamin at a level of 1 kg per ton (P < 0.05). Blood parameters showed alterations, including reduced glucose at 1 kg/ton, increased total protein and reduced cholesterol at 2 kg/ton, and elevated hematocrit and hemoglobin with supplementation. Small intestinal morphology showed no significant changes in villus height or crypt depth. Carcass traits were unaffected. In general, the results showed that the use of protected vitamin AD3E supplement in lamb diets improved the performance of fattening lambs (Final Body Weight (kg), Total Weight Gain (kg) and Daily Weight Gain (g)) through a positive effect on rumen fermentation, although it did not affect diet digestibility.