Early-life organic supplementation and its impact on ruminal SCFA profile in pasture-raised dairy heifer calves

Abstract

Early modulation of the ruminal microbiota has been explored as a strategy to improve digestive efficiency and mitigate methane production in ruminants. This approach depends on the concept of early-life programming, which recognizes the microbial plasticity during initial developmental stages and the potential of early dietary interventions to promote long-term effects on rumen functionality. This study aimed to evaluate the impact of providing an organic additive from birth to three months of age on the profile of short-chain fatty acids (SCFA) in the ruminal fluid of pasture-raised dairy heifer calves. The experiment was carried out at Embrapa Southeast Livestock (São Carlos, SP, Brazil) using 19 Holstein × Jersey crossbred calves (28.2 ± 5.15 kg BW), all daughters of the same bull. Calves were randomly assigned in a randomized block design based on birth date. Treatments were: 1) control (placebo); and 2) treated (organic additive composed of Saccharomyces cerevisiae, essential fatty acids, organic chromium and zinc, crude protein, and mannan oligosaccharide; 3.0 g/animal/day), administered orally. Animals were raised on Cynodon spp. pasture, receiving whole milk (≈ 6 L/day), water, and concentrate since birth. Weaning was gradual, from 62 to 67 days of age. Rumen fluid was collected at 60, 120, and 180 days using an oro-esophageal tube after morning feeding. Samples were analyzed by gas chromatography (GC-2014, Shimadzu, Japan), and SCFA concentrations were calculated using GCSolution^® software. Data were analyzed using a mixed model (SAS PROC MIXED), with treatment, period, and their interaction as fixed effects. SCFA production was mainly affected by age, with increases in acetate, butyrate, and total SCFA over time (P < 0.05). Treatment had no significant effect, except for isovalerate at 60 days, which was lower in treated calves (P = 0.0402). Therefore, early additive supplementation had a limited impact on SCFA profiles under pasture-based conditions.