Substitution of non-forage fibre sources for cereal grains and molasses in calf starter on performance and development of ruminal function

One hundred and thirty-six, new-born female Holstein calves (body weight (BW) = 37.6±0.79 kg) were allocated to one of four starter feeds to evaluate the effects of replacing cereal grains and (or) molasses with non-forage fibre sources on intake, weight gain, and indicators of ruminal development. Diets consisted of a typical, low (16%) neutral detergent fibre (NDF) texturised calf starter, texturised calf starter with moderately higher (20%) NDF, texturised calf starter with moderately higher (21%) NDF and no molasses, and a complete pelleted high (25%) NDF calf starter. Average daily gains and starter intakes were unaffected by moderate levels of NDF. Average daily gain and feed intakes were increased in the preweaning phase but decreased in the postweaning phase by the high NDF complete pelleted diet. Total tract apparent NDF digestibility increased linearly with age but did not differ among diets. Blood concentrations of glucose and β-hydroxybutyrate (BHB) decreased and increased, respectively, with age. Further, blood BHB concentrations were largely unaffected by diet and did not change with increasing dry matter (DM) intake until a threshold was reached, and then increased linearly. Calf-side blood BHB testing resulted in an appreciable number of measurements below the limit of detection of the meter, resulting in censored data. Application of appropriate statistical methodology, required for proper parameter estimation from censored data, suggest the potential for successful field application of calf-side BHB measurements for monitoring starter intake and readiness for weaning in commercial settings. Feeding solely a complete pelleted calf starter throughout the starter phase may provide insufficient levels of effective fibre. Integration of the results of this study with previously published literature via a quantitative analysis suggests that maintaining intake may be the key to successful inclusion of non-forage fibre sources in calf starters.