Document Type : Research Paper
Authors
1 Corresponding Author, Department of Animal and Poultry Science, Faculty of Agricultural Technology, College of Agriculture & Natural Resources, University of Tehran, Pakdasht, Iran. E-mail: bkhorrami@ut.ac.ir
2 Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran. E-mail: sarvakili@um.ac.ir
3 Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran. E-mail: danesh@um.ac.ir
Abstract
Introduction: Today, the use of antimicrobial agents such as antibiotics in livestock diets is facing reduced social acceptance because of the appearance of residues in milk and meat, and therefore, ruminant nutritionists are seeking for appropriate alternatives for these feed additives. The study of essential oils (EOs) as natural feed additives capable of improving rumen microbial fermentation has taken into consideration by nutritionists. Among the EOs, thyme (THY) and cinnamon (CIN) oil have attracted significant attention due to their antimicrobial activity against ruminal microorganisms. Therefore, more research is required to understand their impacts on rumen microbial fermentation in ruminants. Moreover, to the best of our knowledge, few studies has synchronously compared the influences of THY and CIN on rumen fermentation and microorganisms. This study was conducted to evaluate the effect of THY and CIN on performance, and rumen microbial fermentation under in vitro and in vivo conditions.
Materials and methods: In the in vitro experiment, different concentrations (0, 125, 250, 500, and 1000 mg/l) of THY and CIN were incubated for 24-h in batch culture. In the in vivo study 18 growing Holstein calves were used in a completely randomized design to examine effects of supplementing a basal diet (CON) with thyme oil (THY, 5 g/d/calf) or cinnamon oil (CIN, 5 g/d/calf) on performance and rumen microbial fermentation. Calves were fed ad libitum diets consisting of 15% forage and 85% concentrate for 80 d.
Results and discussion: The high concentration of THY and CIN (1000 mg/l) inhibited rumen microbial fermentation thereby decreasing total gas production and DM disappearance at 24 of incubation, and total VFA concentration. Cinnamon oil at 1000 mg/l increased final pH of batch culture (P<0.05). The lower concentration of THY and CIN (125 and 250 mg/l) decreased the acetate to propionate ratio (P<0.05), without reducing VFA concentration. Supplementation of THY or CIN did not affect DMI and ADG. There were also no effects of EOs on ruminal pH, rumen concentrations of ammonia nitrogen and total VFA; whereas molar proportion of acetate and ratio of acetate to propionate decreased (P<0.05), and the molar proportion of propionate increased (P<0.05). Rumen molar proportion of butyrate was significantly increased (P<0.05) by adding CIN. The population of protozoa and methanogens bacteria decreased in the rumen of calves receiving EOs (P<0.05). Ruminal population of Fibrobacter succinogenes was not affected by treatments, but populations of Ruminococcus albus and flavefaciens decreased by THY and CIN (P<0.05).
Conclusion: Based on the results of the present study, although dietary addition of THY and CIN did not have a significant effect on the performance of feedlot calves, but it improved the rumen fermentation properties, which may be considered as potential alternatives for antibiotics in beef production systems.
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