牛至精油对荷斯坦犊牛生长性能、血清免疫指标及瘤胃微生物的影响OA

[Objective]This study aimed to investigate the effects of supplementing starter feed with oregano essential oil(OEO)on the growth performance,serum indicators,and rumen microbial communities in newborn Holstein calves.[Method]Thirty-two newborn female Holstein calves with similar body weight(38.9 kg±1.3 kg)and good body condition were selected.According to birth date,the calves were alternately assigned to a control group(CO)or an oregano essential oil group(OEO),with 16 replicates per group were fed a basal starter feed,whereas those in OEO group were fed the same basal starter feed supplemented with 1.25 g/(head·d)of oregano essential oil.Calves were weaned at 56 days of age,and the experimental period lasted 70 days.During the trial,feed intake was recorded daily.Body weight was measured on days 0 and 70 to calculate average daily gain(ADG)and feed-to-gain ratio(F/G).Body oblique length,body height,chest circumference,tube circumference and hip width were measure on days 2,28,and 56.Blood samples of 10 mL were collected on days 2,56,and 70,and serum was separated to determine the concentrations of urea nitrogen,immunoglobulin G(IgG),IgA,IgM,along with volatile fatty acid(VFA)at 56 days of age.On days 70,rumen fluid was collected to analyze the composition of the rumen microbiology.[Result]①Compared with CO group,the average feed intake of calves in OEO group at 57-63 and 64-70 days of age,as well as the chest circumference at 56 days of age,were significantly increased(P<0.05),the F/G was significantly decreased(P<0.05),while final weight and body oblique length at 56 days of age were highly significantly increased(P<0.01).②Compared with CO group,the content of serum IgG at 56 days of age and serum urea nitrogen at 70 days of age of calves in OEO group were significantly increased(P<0.05).The contents of valeric acid,isovaleric acid,and acetic acid in serum increased significantly or extremely significantly at 56 days of age(P<0.05 or P<0.01).③Compared with CO group,the relative abundance of f_Marinifilaceae in the rumen was significantly increased in OEO group(P<0.05),and the relative abundance of microorganisms involved in chemoheterotrophy and fermentation was also significantly increased(P<0.05).[Conclusion]The addition of 1.25 g/d of oregano essential oil to the starter diet for newborn Holstein calves could enhance growth performance,serum immunity and ruminal fermentation,regulate the rumen microbiota,and improve calf health,demonstrating potential for use as an alternative to antibiotics.