Effects of Feeding Different Chelated Mineral Sources on the Performance of Afshari Ewes and Lambs

Background: Iran is geographically located in a hot and dry region, and its pastures are mainly lacking and imbalanced in terms of nutrients, including minerals.In addition to causing many complications caused by the lack of minerals, this problem also endangers the metabolism of other nutrients.Due to the fact that most of the feed consumed by sheep in the country is provided from pastures, and there is no possibility of manual feeding, the aforementioned deficiencies can play an effective role in reducing the income of farmers and livestock productivity.Chelated minerals are those that are attached to one or more amino acids or organic acids.In other words, when a mineral substance is connected to another one, such as amino acids, it produces a chelated mineral substance.Numerous studies have shown that chelate forms of zinc, manganese, and copper are more bioavailable than inorganic forms.This issue supports the functions related to low-consumption minerals and causes their very small excretion due to the much lower consumption amount.The higher bioavailability of chelates is related to different absorption and balancing mechanisms and the absence of antagonists related to minerals.Therefore, this study aimed to investigate the effects of feeding sources of chelated trace minerals (Zn, Cu, Mn, Se, and Co) on the performance of Afshari ewes and lambs.Methods: Experimental animals were used from a herd using estrus synchronization with 60 heavy pregnant ewes of the Afshar breed with an approximate age of 2 years and the second calving cycle in the form of a completely randomized design with three treatments each containing 20 replications.The test period was from the 21 st day before delivery to the 70 th day after delivery.Experimental treatments were a basal diet without supplemental trace minerals (Control, n = 20), a basal diet plus chelate sources of trace minerals (Chelate, n = 20), and a basal diet plus organic sources of trace minerals (n = 20).Experimental diets were adjusted and balanced based on meeting the metabolic needs of pregnant and lactating ewes using SRNS small ruminant feeding system software based on dry matter with 68% fodder and 32% pre-lambing concentrate and 70% fodder plus 30% post-lambing-partum concentrate percentage after birth.The consumed ration was completely mixed and offered to the ewes twice a day (8 am and 4 pm).The ewes were weighed with a digital scale (accuracy of 50 g) before offering the morning feed at the beginning of the experiment, on the day of calving, and on the 35 th and 70 th days after calving.The body conditions of the ewes at the beginning, the day of calving, and days 35 and 70 after calving were scored based on a scoring system of 1 -5.Colostrum production was measured by weighing lambs before and after eating colostrum 24 hours after birth and milk production by the milking method with the intramuscular injection of oxytocin.The lambs were also weighed at birth and at 30 and 70 days old, along with measuring their daily weight gain (using a digital scale with an accuracy of 50 g).The final data were analyzed using the GLM procedure by SAS statistical software version 9.1 (SAS, 2001).The means of the treatments were compared using Duncan's multiple range test at an error probability level of 0.05 .Results: Dry matter consumption, colostrum production, and milk production in the chelate group were significantly higher than those of the other two groups (P < 0.05).The composition of ewes' milk after parturition was not affected by the experimental treatments (P < 0.05).Body weight and body condition scores were affected by the experimental treatments, except they were