Abstract
BackgroundThe nutrition of calves from birth until weaning is predominantly from liquid (milk or milk-based) feeds. Liquid feed allowances are often restricted during artificial rearing to accelerate the development of the rumen by promoting solid feed intake. Liquid feeds bypass the rumen and are digested in the lower digestive tract, however, the influence of different types of milk feeds, and their allowances, on the calf hindgut microbiota is not well understood. In this study, faecal samples from 199 calves raised on three different allowances of milk replacer: 10% of initial bodyweight (LA), 20% of initial bodyweight (HA), and ad libitum (ADLIB), were collected just prior to weaning. Bacterial community structures and fermentation products were analysed, and their relationships with calf growth and health parameters were examined to identify potential interactions between diet, gut microbiota and calf performance.ResultsDifferences in the total concentrations of short-chain fatty acids were not observed, but higher milk replacer allowances increased the concentrations of branched short-chain fatty acids and decreased acetate to propionate ratios. The bacterial communities were dominated by Ruminococcaceae, Lachnospiraceae and Bacteroides, and the bacterial diversity of the ADLIB diet group was greater than that of the other diet groups. Faecalibacterium was over three times more abundant in the ADLIB compared to the LA group, and its abundance correlated strongly with girth and body weight gains. Milk replacer intake correlated strongly with Peptococcus and Blautia, which also correlated with body weight gain. Bifidobacterium averaged less than 1% abundance, however its levels, and those of Clostridium sensu stricto 1, correlated strongly with initial serum protein levels, which are an indicator of colostrum intake and passive transfer of immunoglobulins in early life.ConclusionsHigher milk replacer intakes in calves increased hindgut bacterial diversity and resulted in bacterial communities and short chain fatty acid profiles associated with greater protein fermentation. Increased abundances of beneficial bacteria such as Faecalibacterium, were also observed, which may contribute to development and growth. Moreover, correlations between microbial taxa and initial serum protein levels suggest that colostrum intake in the first days of life may influence microbiota composition at pre-weaning.
Highlights
The nutrition of calves from birth until weaning is predominantly from liquid feeds
This study provides further insights into the influence of milk replacer allowance on the gut microbiota and their contributions to calf growth and development prior to weaning
The total faecal short-chain fatty acids (SCFA) concentrations did not differ among the treatment groups, but the branched shortchain fatty acids (BSCFA), isobutyric acid and isovaleric acid, were in higher concentrations in calves on the ad libitum (ADLIB) treatment (ANOVA, P < 0.001; Table 1)
Summary
The nutrition of calves from birth until weaning is predominantly from liquid (milk or milk-based) feeds. Liquid feeds bypass the rumen and are digested in the lower digestive tract, the influence of different types of milk feeds, and their allowances, on the calf hindgut microbiota is not well understood. Ruminants are born with under-developed rumens and from birth until weaning, are highly reliant on milk-based feeds which bypass the rumen [1] and are largely digested in the lower gut. The microbial communities of the lower gut are important for pre-weaned ruminants as they contribute to nutrition, gut development and homeostasis. Characterisation of the calf intestinal microbiota is generally undertaken through the analysis of faecal samples [4,5,6,7], though the characterisation of microbial communities along the gastrointestinal tract is commonly performed, which allows a comprehensive view of the development of both foregut and hindgut communities in concert [8,9,10]. Faecalibacterium were dominant in the calf caecum and colon microbiota of 7-week old calves [8], and were associated with greater weight gains and lower incidences of diarrhoea in calves [5], where their potential as a probiotic for calves is being explored [12, 13]
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