Dried citrus pulp (DCP) is a high-fibre by-product of the citrus industry. In total mixed ration (TMR) systems it has been shown to maintain a more stable ruminal environment, improving overall production compared with maize. The aim of the study was to determine the effects of stepwise replacement of maize with DCP in a concentrate supplement on milk yield, milk composition and rumen health of Jersey cows grazing ryegrass pasture. Sixty-eight lactating Jersey cows (μ ± SD; 84.5 ± 43.8 days in milk, 20.4 ± 3.09 kg/day) were used in the trial. Cows were allocated to one of four treatments, with 17 cows per treatment, namely no DCP (NDCP): 0% replacement; low DCP (LDCP): 33% replacement; medium DCP (MDCP): 66% replacement; and high DCP (HDCP): 100% replacement. An additional six ruminally cannulated Jersey cows were randomly allocated to the NDCP and HDCP treatments in a two-period cross-over design. Milk yield decreased between 2.1 and 3.2 kg/day when maize was replaced with DCP. Milk fat content did not differ between treatments. However, treatment had a quadratic effect on milk protein and lactose content, with the LDCP and MDCP treatments having the highest values. No change in the diurnal ruminal pH curve and no differences in the rate and extent of pasture dry matter and neutral detergent fibre degradability between treatments were observed. In conclusion, replacing maize grain with DCP in a conventional concentrate diet led to a decrease in milk yield, while rumen health was maintained. ______________________________________________________________________________________

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