تاثیر مخلوط اسانس‌های گیاهی کارواکرول، تیمول و اکالیپتول به‌شکل آزاد یا کپسوله‌شده بر عملکرد تولیدی، گوارش‌پذیری مواد مغذی و متابولیت‌های خون گاوهای شیرده هلشتاین

این پژوهش با هدف مطالعه تاثیر افزودن مخلوط اسانس‌های گیاهی آزاد و کپسوله‌شده به جیره بر عملکرد شیردهی، گوارش‌پذیری مواد مغذی و متابولیت‌های خونی گاوهای شیرده هلشتاین انجام شد. برای این منظور از 21 راس گاو شیرده هلشتاین با میانگین شکم زایش 1.7±2.16، میانگین وزن بدن 43±620 کیلوگرم، تولید شیر روزانه 3.4±33.6 کیلوگرم و روزهای شیردهی 12±30 روز در قالب طرح کامل تصادفی با سه تیمار آزمایشی (هفت تکرار برای هر تیمار) استفاده گردید. جیره‌های آزمایشی شامل (1) جیره پایه (جیره بدون افزودنی)، (2) جیره پایه + 80 میلی‌گرم مخلوط اسانس‌های گیاهی (کارواکرول، تیمول و اکالیپتول) به‌شکل آزاد در هر کیلوگرم ماده خشک، (3) جیره پایه + 40 میلی‌گرم مخلوط اسانس‌های گیاهی (کارواکرول، تیمول و اکالیپتول) به‌شکل کپسوله‌شده در هر کیلوگرم ماده خشک بود. نتایج نشان داد که گاوهای تغذیه‌شده با جیره دارای مخلوط اسانس‌های گیاهی به شکل کپسوله‌شده، تمایل به مصرف خوراک و تولید شیر تصحیح‌شده برای چهار درصد چربی بیشتر، قابلیت هضم پروتئین بالاتر و میزان پروتئین شیر بیشتر در مقایسه با گروه شاهد داشتند. میانگین ظرفیت آنتی‌اکسیدانی کل خون گاوهای تغذیه‌شده با جیره دارای اسانس‌های گیاهی کپسوله‌شده در مقایسه با گاوهای تغذیه‌شده با شاهد بالاتر بود. گاوهای تغذیه‌شده با جیره دارای مخلوط اسانس‌های گیاهی به شکل کپسوله‌شده، تمایل به کاهش سول‌های سوماتیک بدنی شیر و نیتروژن اوره‌ای خون در مقایسه با گروه شاهد داشتند. به‌طور کلی، نتایج این پژوهش نشان داد که اضافه‌کردن اسانس‌های گیاهی به شکل کپسوله به جیره از طریق بهبود خوراک مصرفی، قابلیت هضم پروتئین و ظرفیت آنتی‌اکسیدانی کل خون می‌تواند اثر مثبت بر کاهش تنش اکسیداتیو و عملکرد گاوهای شیرده اوایل شیردهی داشته باشد.

the effect of mixtures of free or encapsulated plant essential oils (carvacrol, thymol, and eucalyptol) on performance, nutrient digestibility, and blood metabolites of holstein dairy cows

introduction: natural feed additives, particularly plant essential oils (peos)—derived from leaves, flowers, bark, and other plant parts and rich in bioactive compounds like terpenes, phenolics, and aldehydes—have gained increasing attention in ruminant nutrition. these compounds exert antimicrobial, antioxidant, anti inflammatory, and digestive stimulant effects, which make them attractive candidates for improving health, productivity, and metabolic efficiency in dairy cows, especially during the critical early lactation period. early lactation is a challenging phase for high yielding dairy cows, characterized by negative energy balance, reduced dry matter intake (dmi), mobilization of body reserves, and increased risk of oxidative stress and metabolic disorders. supplementing diets with natural additives such as peos is a strategy to improve nutrient utilization, reduce stress, and support milk production and immune function. although peos modulate ruminal fermentation, inhibit undesirable microbes, and promote volatile fatty acid (vfa) production, their high volatility and rapid degradation in the rumen can limit their effectiveness. encapsulation technology, using protective coatings (e.g., lipids, polysaccharides), addresses this issue by improving stability, controlled release, and targeted delivery of active ingredients to the lower gut, thereby enhancing their bioavailability and physiological effects. therefore, this study aimed to evaluate the effects of free vs. encapsulated mixtures of carvacrol, thymol, and eucalyptol on feed intake, nutrient digestibility, milk yield and composition, and blood metabolites in holstein dairy cows during early lactation. material and methods: a total of 21 holstein multiparous cows (average parity of 2.16 ± 1.7, mean body weight of 620 ± 43 kg, average daily milk yield of 33.6 ± 3.4 kg, and 30 ± 12 days in milk) were enrolled in a completely randomized design with three dietary treatments (n = 7 per treatment). cows were housed in individual tie stalls with free access to water and fed twice daily (08:00 and 17:00). a total of 21 holstein multiparous cows (average parity of 2.16 ± 1.7, mean body weight of 620 ± 43 kg, average daily milk yield of 33.6 ± 3.4 kg, and 30 ± 12 days in milk) were enrolled in a completely randomized design with three dietary treatments (n = 7 per treatment). cows were housed in individual tie stalls with free access to water and fed twice daily (08:00 and 17:00). the experimental treatments were: control: basal tmr diet without additive; free peos: basal diet + 80 mg/kg dm of free essential oil mixture (carvacrol, thymol, eucalyptol); encapsulated peos: basal diet + 40 mg/kg dm of encapsulated essential oil mixture (same compounds). the trial lasted 56 days, comprising 14 days of adaptation and 42 days of data collection. feed intake was recorded daily. milk production was measured during three daily milkings (05:00, 12:00, 18:00), and milk composition was analyzed on days 54–55. fecal samples were collected for digestibility analysis using internal markers. blood samples were drawn on days 40 and 55 to evaluate glucose, urea nitrogen, cholesterol, nefa, bhb, and total antioxidant capacity (tac). results and discussion: dry matter intake (dmi) was slightly increased in cows fed encapsulated peos compared to the control. this may be attributed to improved palatability and reduced negative sensory impacts due to microencapsulation, which masks the pungent odor and bitter taste of free essential oils. cows receiving encapsulated peos showed significantly higher apparent crude protein digestibility, suggesting a more efficient bypass of ruminal degradation and improved absorption in the small intestine. this finding is consistent with calsamiglia et al. (2007), who reported that certain eo compounds can inhibit ruminal proteolysis, leading to increased rumen undegraded protein (rup) flow. notably, the milk protein percentage and yield were higher in the encapsulated group. this is likely linked to the increased availability of absorbable amino acids, supporting enhanced milk protein synthesis in the mammary gland. furthermore, blood analysis showed elevated total antioxidant capacity (tac) and blood glucose in the encapsulated peo group. the improved tac suggests a reduction in oxidative stress, which is crucial during early lactation when metabolic demands are high. elevated glucose also reflects improved energy status due to better nutrient digestion and possible shifts in vfa profiles toward more glucogenic propionate (patra yu, 2012). in contrast, cows fed free peos demonstrated moderate improvements in intake and digestibility but less pronounced than the encapsulated group. this supports the concept that encapsulation enhances the functional delivery of eos beyond the rumen. the somatic cell count (scc), although not statistically significant, tended to be lower in eo fed cows, particularly in the encapsulated group. this may reflect better mammary health or immune modulating effects of peos. these results collectively highlight the advantages of encapsulated over free essential oils in enhancing performance, digestion, and metabolic health in dairy cows. conclusion: results of this study showed that incorporating encapsulated plant essential oil mixtures (karoguttm) into the diet positively impacts feed intake, protein digestibility, and performance in early lactation dairy cows. notably, the encapsulated form increased blood glucose and antioxidant capacity while reducing milk somatic cell counts, crucial for mitigating oxidative stress and sustaining milk production during early lactation.