نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم دامی، دانشکده کشاورزی ، دانشگاه شهید باهنر کرمان، کرمان، ایران
2 گروه گیاهی، دانشکده کشاورزی، دانشگاه ولیعصر رفسنجان، رفسنجان، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
In early lactation, dairy cows encounter numerous metabolic and physiological challenges, including a sudden surge in energy demands for milk production coupled with reduced feed intake. This leads to a negative energy balance, potentially causing adverse outcomes such as decreased body condition scores, heightened fat mobilization, impaired immune function, and elevated blood metabolites like non-esterified fatty acids (NEFA) and beta-hydroxybutyrate (BHB). Consequently, the use of natural feed additives to enhance health status, boost productivity, and mitigate metabolic issues in freshly calved cows holds significant importance. Natural feed additives, particularly plant essential oils—derived from various plant parts and rich in bioactive compounds like terpenes and phenolics—have gained attention for improving health, productivity, and metabolic status in dairy cows especially during early lactation period. Although these oils can modulate rumen fermentation, enhance nutrient digestibility, and reduce oxidative stress, but their rapid degradation in the rumen poses a challenge, which encapsulation technology addresses by protecting active compounds for improved stability and efficacy. Therefore, this study was done to investigate the effects of incorporating mixtures of free and encapsulated plant essential oils (carvacrol, thymol, and eucalyptol) into the diet on performance, nutrient digestibility, and blood metabolites of Holstein dairy cows. In this study 21 Holstein lactating dairy cows with an average parity of 2.16 ± 1.7, mean body weight of 620 ± 43 kg, daily milk yield of 33.6 ± 3.4 kg, and 30 ± 12 days in milk were used. Experimental diets comprised a basal diet (control), basal diet plus 80 mg/kg DM of free essential oils (carvacrol, thymol, eucalyptol mixture in equal proportion), or 40 mg/kg DM of encapsulated essential oils (Carogut, Aral Fanavar Karo, Iran) and were formulated according to NASEM (2021) guidelines. The trial wad 56 days, including a 14-day adaptation period to the experimental diets and a 42-day period for sampling and data collection. The chemical analyses of feeds (DM, OM, CP, EE) were done according to AOAC (2023) and Fiber fraction according to Van Soest et al. (1991). Cows were housed individually, fed twice daily (8:00 and 17:00) ad libitum, milked thrice daily (5:00, 12:00, 18:00), and milk composition (fat, protein, lactose, solids-not-fat, total solids) was analyzed on days 54–55 using a MilkoScan (B133) from samples preserved with potassium dichromate. Daily feed intake was monitored, orts weighed each morning to calculate dry matter intake, and cow body weights were measured three times (start, mid, end of the experiment) using a digital scale. Nutrient digestibility was assessed in the final week via fecal sampling from the rectum, employing acid-insoluble ash as an internal marker. On day 56, blood was collected from the tail vein, cooled in ice, centrifuged at 3000 rpm for 15 minutes, and serum stored at -20°C; blood metabolites (glucose, urea nitrogen, total protein, cholesterol, NEFA, BHB) and antioxidant capacity were measured using commercial kits and Autoanalyzer apparatus. Results of this study showed that initial body weights of cows across treatments showed no significant differences, indicating effective randomization. Body weight decreased in all groups, though numerically less in those receiving essential oils. Dry matter intake tended to increase (P = 0.06) in cows fed encapsulated essential oils (21.38 vs. 20.75 kg/day for control), while dry matter digestibility (67.25%, 68.16%, 70.83% for treatments 1–3, respectively) remained unaffected (P > 0.05). Encapsulated essential oils significantly improved apparent protein digestibility (67.87% vs. 64.14%, P = 0.04) and tended to enhance organic matter (P = 0.08) and neutral detergent fiber (P = 0.09) digestibility. Milk yield numerically increased from 35.13 kg/day (control) to 36.45 and 37.1 kg/day with free (80 mg) and encapsulated (40 mg) essential oils, respectively, with 4% fat-corrected milk showing a similar trend (32.45, 33.40, 34.35 kg/day; P = 0.08). Milk protein was significantly increased in response to addition of encapsulated essential oils compared to control diet (3.12% vs. 2.98%, P = 0.04), Blood glucose tended to increase (61.35 vs. 56.71 mg/dL, P = 0.08), and total antioxidant capacity was significantly higher (0.81 vs. 0.68 mmol/L, P = 0.03) compared to the control. Overall, the findings of this research suggest that the inclusion of encapsulated plant essential oils in the diet can positively influence early-lactation dairy cows by enhancing feed intake, protein digestibility, and total blood antioxidant capacity, thereby contributing to reduced oxidative stress and improved performance.
کلیدواژه‌ها [English]
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