Effects of a blend of essential oils in milk replacer on performance, rumen fermentation, blood parameters, and health scores of dairy heifers

The aim of this study was to evaluate how the inclusion a blend essential oils in milk replacer (MR) affects different outcomes dairy heifers. evaluated: feed intake, performance, body development, blood cells and metabolites, insulin-like growth factor-1 (IGF-1), rumen fermentation, fecal scores, respiratory scores. All were evaluated during pre-weaning (4–60 d age), carry-over effects post-weaning (61–90 age) periods. experimental units utilized 29 newborn Holstein × Gyr crossbred heifers, with genetic composition 5/8 or more 3/8 less weight (BW) at birth 32.2 ± 5.2 kg. Experimental assigned either control (CON, n = 15) oil supplementation (BEO, 14) treatment, maintaining balance composition. BEO supplemented MR 1 g/d/calf (Apex Calf, Adisseo, China) composed by plant extracts derived from anise, cinnamon, garlic, rosemary, thyme. During phase, all heifers fed 5 L MR/d reconstituted 15% (dry matter basis), divided into two equal meals. Water starter provided ad libitum . post-weaning, animals received maximum 3 kg starter/d, corn silage, Feed scores daily. BW measured every three days, while development recorded weekly. Blood samples collected on 0, 30, 60 age for total cell count, weekly weaning day determinate ß-hydroxybutyrate, urea glucose, biweekly IGF-1. Ruminal parameters (pH, volatile fatty acids, ammonia-N, acetate:propionate proportion—C2:C3) days 14, 28, 42, 60, 74 90. A randomized complete block design an interaction between treatment week method choice test hypothesis BEO’s effect outcomes. An ANOVA procedure used continuous outcomes, non-parametric ordered categorical both adopting CI 95%. Results indicated that there not enough evidence accept alternative metabolites However, results significantly proportion C2:C3 pre- ( P 0.05). Similarly, significant basophil ≤ 0.001), platelet 0.04) counts pre-weaning. also lymphocytes revealing cumulative effect. Lastly, pre-weaning, lower values BEO. contributed ruminal manipulation immunity improvement, decreased morbidity neonatal diarrhea phase.