Effect of slow-release bolus containing zinc, selenium, copper, cobalt, manganese, and iodine on the growth performance and blood parameters of Mehraban male lambs

Introduction: Trace minerals are essential for supporting the growth and health of animals. Trace element deficiencies are common in many countries and affect animal health, productivity, and welfare. Trace element imbalance conditions may be manifested as a result of a single or multiple element deficiency. The trace elements of selenium, copper, zinc, manganese, iodine, and cobalt are involved in the immune function of domestic farm animals and will therefore potentially have roles in the etiology of infectious diseases of animals. In addition, many structural proteins, enzymes, and cellular proteins rely on the presence of these minerals to function properly. Among them, the activation of enzymes, strengthening the immune system, and improving performance can be mentioned. Zinc is essential for the metabolism of carbohydrates, proteins, and nucleic acids. Selenium is part of the glutathione peroxidase enzyme, which plays an important role in protecting the cell membrane and oxidative processes. In addition, selenium plays an important role in the protection of the thyroid gland as well as the metabolism of thyroid hormones, and selenium deficiency causes the destruction of mitochondrial and cell membranes. Copper is essential for growth and the prevention of pathological and clinical problems in animals. Copper deficiency can cause anemia, bone disorders, connective tissue disorders, insufficient growth of lambs, and abortion. Manganese is an essential element in bone growth, reproduction, and the functioning of the nervous and immune system. Cobalt is another essential element that is underutilized in ruminants. Cobalt is part of vitamin B₁₂ and plays a role in protein and energy metabolism. The most important task of iodine in the body is the synthesis of thyroid hormones. Using supplemental feed as a trace element carrier incurs the costs of both feed and labour if additional feed is not required. Free access minerals, mineral licks, and blocks are subject to variable intakes, with animals consuming between nothing and many times the required intake. Daily supplementation has a short-term effect and is impractical for systems such as grazing, where manual feeding is not possible. Methods such as injection, which provide specific doses at regular intervals, are suitable for elements with storage capability in the body, but injection is also an expensive and time-consuming practice. Oral dosing with trace element drenches is another possible alternative. Although this ensures that each animal receives a dose, it may need regular handling, storage mechanisms for the element, and/or a high animal tolerance to the levels of element given for long-term dosing. The use of slow-release boluses can provide a certain amount of minerals to the animal over time. It has been reported that the use of slow-release bolus containing copper, cobalt, and selenium has improved the performance of sheep compared to the control group. This experiment aimed to determine the effect of a slow-release bolus containing zinc, selenium, copper, cobalt, manganese, and iodine (multitace) on the performance and blood parameters of Mehraban male lambs.
Materials and methods: 14 Mehraban male lambs aged 5.5 months with an average weight of 29±2 kg were used in a completely randomized design in two treatments and seven replicates. The control group received a basal diet, and the bolus treatment group received a basal diet + slow-release bolus. The slow-release bolus used in this study contained 150000 ppm Zn, 2282.5 ppm Se, 21600 ppm Cu, 2574 ppm Co, 20250 ppm Mn, and 2125 ppm I and released 150 to 200 mg daily on average. Bolus was administered on day 0 before feeding via a bolus gun. The experiment lasted for 56 days. To obtain the amount of feed consumed (based on dry matter), daily feed consumption and its residue were measured. Lambs were weighed on the first day of the experiment and on days 14, 28, 42, and 56 of the experiment to determine weight changes and performance of lambs. Blood samples were taken on the first and last days of the experiment before the morning meal. Alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), mineral elements concentration (zinc, copper, iron, calcium, and phosphorus), total protein, albumin, globulin, and blood urea nitrogen concentrations were measured. Data were analyzed in a completely randomized design using the GLM procedure of SAS 9.1 software.
Results and discussion: Although the final weight and feed conversion ratio in the lambs receiving bolus showed a numerically higher value than the control, statistically, no significant difference was observed in the measured parameters. Blood parameters, including liver enzyme activities, concentrations of total protein and globulin, showed no significant difference between the treatments, but the blood serum albumin was significantly higher in lambs that received a bolus than in control lambs (P<0.05). Plasma zinc concentration also increased significantly in the group receiving bolus compared to the control group (P<0.05). Different results have been reported in different studies using slow-release mineral boluses. The differences in results between studies probably depend on the amount of minerals in the basal diet, the age and species of the animals, and the geographical conditions. It seems that in the present study, the amount of minerals in the basal diet was close to the level required by growing lambs, and the slow-release bolus did not have much effect on the performance of the lambs. In the present study, the significant difference in albumin levels between the treatment and control groups may be due to the positive effect of the bolus, especially the zinc element contained in it, on protein synthesis.
Conclusions: In general, the use of slow-release bolus containing zinc, selenium, copper, cobalt, manganese, and iodine affected the concentration of albumin and zinc element, and a significant difference was observed in the group receiving the bolus and the control group. But it had no significant effect on the performance of lambs, liver enzyme activities, and the concentration of other mineral elements and blood protein parameters. According to the results, although the difference in performance was not significant, the daily weight gains of lambs receiving the bolus were about six percent higher than the control group, and this could improve efficiency.