| چکیده انگلیسی مقاله |
Extended Abstract
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 the farmer and livestock productivity. Chelated minerals are those minerals that are attached to one or more amino acids or organic acids. In other words, when a mineral substance is connected to another organic substance 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 it to have a 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, the objective of this study was to investigate the effects of feeding chelated trace minerals (Zn, Cu, Mn, Se and Co) sources on performance of Afshari ewes and lambs.
Material and 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 two years and the second calving cycle in the form of a completely randomized design with three treatments and 20 repetitions in each treatment. The test period was from the 21st day before delivery to the 70th day after delivery. Experimental treatments were basal diet without supplemental trace minerals (Control, n=20), basal diet plus chelate sources of trace minerals (Chelate, n=20) and basal diet plus organic sources of trace minerals (n=20). Experimental diet based on meeting the metabolic needs of pregnant and lactating ewes using SRNS small ruminant feeding system software (Tedeschi et al., 2010) based on dry matter with 68% fodder and 32% pre-lambing concentrate and 70% fodder plus 30 post lambing-partum concentrate. The concentration percentage was adjusted and balanced 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 grams) before offering the morning feed at the beginning of the experiment, on the day of calving and on the 35th and 70th days after calving. The body condition score of the ewes at the beginning, day of calving, and days 35 and 70 after calving were scored based on a scoring system of 1 to 5. Colostrum production was measured by weighing lambs before and after eating colostrum (Ocak et al., 2005) at 24 hours after birth and milk production by milking method with intramuscular injection of oxytocin (Purroy and Jaime, 1995). Also, the lambs were weighed at birth and 30 and 70 days old and their daily weight gain was measured (using a digital scale with an accuracy of 50 grams). The final analysis of the data was performed using the GLM procedure, by SAS statistical software version 9.1 (SAS, 2001). The mean comparison of the treatments was also done using Duncan's multiple range tests at the error probability level of 0.05 (Duncan, 1955).
Results: The results showed that dry matter consumption, colostrum production and milk production in the chelate group were significantly higher than the other two groups (P<0.05). The composition of ewes' milk after parturition was not affected by experimental treatments (P<0.05). Body weight and body condition score were affected by the experimental treatments except at the time of lambing on days 35 and 70 after lambing, and in the chelate and organic groups it was significantly greater than the control group (P<0.05). The weight loss of the ewes was affected by the experimental treatments and the ewes of the chelate and organic groups lost significantly lower weight than the control group (P<0.05). The weight of lambs at birth, 35 days old and 70 days old in lambs born from ewes fed with chelated source of low consumption minerals was higher than organic group and control group (P<0.05). Daily weight gain up to 70 days in ewes fed with chelated source of low-consumption minerals was higher than organic group and control group (P<0.05).
Conclusion: In general, the results of the present study showed that feeding ewes with mineral substances in the form of chelate led to more feed consumption, less body weight loss, and ultimately improved the growth performance of Afshari lambs.
|