نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Introduction: Buffers are frequently incorporated into high-concentrate diets to mitigate ruminal acidity and stabilize ruminal pH. Their inclusion can augment the acetate-to-propionate ratio and enhance fiber digestibility, thereby promoting dry matter intake. In parallel, plant extracts, owing to their antimicrobial, antioxidant, and biologically active properties, have emerged as promising feed additives. Among these, thyme (Thymus vulgaris L.) extract has demonstrated antimicrobial activity under in vitro conditions, evidenced by reduced methane production and altered rumen fermentation characteristics. Garlic (Allium sativum L.) extract exhibits prebiotic-like effects and possesses antioxidant, antimicrobial, anti-methanogenic, and anti-protozoal properties. Eucalyptus (Eucalyptus globulus Labill.) extract contains a mixture of volatile essential oils such as 1, 8-cineole, limonene, and α-terpineol, along with non-volatile phenolic compounds, which may modulate rumen fermentation and inhibit methanogenesis. Given the potential benefits of both buffers and plant extracts, this study aimed to evaluate the effects of supplementing the diet with 2% sodium bicarbonate and plant extracts (thyme, garlic, and eucalyptus) on gas production parameters, ruminal degradability, and the apparent digestibility of nutrients.
Materials and Methods: This study was conducted to evaluate the effects of 2% sodium bicarbonate supplementation, combined with various plant extracts, on in vitro gas production kinetics and the in sacco ruminal degradability of dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF). Additionally, the apparent nutrient digestibility of the experimental diets was assessed. The treatments were structured as follows: 1) 2% sodium bicarbonate (control); 2) Control + thyme extract (400 mg/kg DM of the diet); 3) Control + garlic extract (300 mg/kg DM); 4) Control + eucalyptus extract (150 mg/kg DM). A fattening diet was formulated using the Small Ruminant Nutrition System (SRNS) software and provided as a Total Mixed Ration (TMR) with a forage-to-concentrate ratio of 30:70 (DM basis). Three 2-year-old Zel ewes (average body weight: 43±2 kg) were utilized to evaluate ruminal degradability parameters following the approved animal welfare protocols. The animals were housed individually in semi-open, roofed metabolic cages with free access to water. Following an adaptation period, the ewes were fed the experimental diets twice daily at 08:00 and 20:00 h. Rumen fluid was collected from the ruminally cannulated Zel ewes prior to the morning feeding to determine gas production parameters. Apparent nutrient digestibility was determined using the acid-insoluble ash (AIA) method as an internal marker. Twenty male Zel sheep (6–7 months old; 38±2 kg body weight) were assigned to four dietary treatments (five lambs per treatment) and fed the experimental diets for 42 days. Data were analyzed using the GLM procedure of SAS software, and means were compared using Duncan’s multiple range test at a significance level of P<0.05.
Results and Discussion: The results indicated that gas production potential (P = 0.0003) and gas production at 96 h (P = 0.0002) were significantly higher in the treatment containing eucalyptus extract compared to the other experimental treatments. Gas production at 24 and 48 h was significantly increased by eucalyptus extract supplementation compared to the other treatments (P < 0.05). Organic matter digestibility (P = 0.0352), metabolizable energy (P = 0.0371), and the concentration of short-chain fatty acids (P = 0.0482) were significantly higher in the eucalyptus extract and control groups compared to the thyme extract treatment. The rapidly degradable fraction of DM was significantly increased in the eucalyptus extract treatment compared to the thyme and garlic extract treatments (P = 0.0137). The slowly degradable fraction and effective degradability of DM at outflow rates of 0.02, 0.05, and 0.08 tended to be higher in the garlic extract group relative to the control (P = 0.0828). The degradation rate constant of DM was significantly higher in the eucalyptus extract treatment compared to the other experimental groups (P = 0.0218). None of the ruminal degradability parameters for CP were significantly affected by the experimental treatments (P > 0.05). The rapidly degradable fraction of NDF was significantly reduced in all plant extract treatments compared to the control group (P = 0.0009), while no significant differences were observed among treatments for the other ruminal degradability parameters of NDF (P > 0.05). Dietary supplementation with plant extracts significantly enhanced dry matter (P = 0.0155) and organic matter (P = 0.0041) digestibility compared to the control diet. The effect of treatments on crude protein digestibility showed a trend toward significance (P = 0.0874). Neutral detergent fiber digestibility was significantly higher in the thyme extract treatment compared to the other treatments (P = 0.0200). Finally, crude fat digestibility was significantly increased in all plant extract treatments compared to the control group (P = 0.0406).
Conclusion: Supplementation with plant extracts distinctly modulated ruminal fermentation and nutrient digestibility in Zel sheep. Eucalyptus extract exhibited the most pronounced positive effects on nutrient digestibility, the rapidly degradable fraction of dry matter, and gas production parameters, whereas thyme and garlic extracts suppressed fermentation due to their strong antimicrobial activity. Despite these differences, all plant extract treatments enhanced apparent nutrient digestibility relative to the control. Overall, eucalyptus extract with sodium bicarbonate proved most effective in enhancing ruminal fermentation efficiency and maintaining pH stability in concentrate-based diets.
کلیدواژهها English
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