Effect of supplementation of a robotic milker pellet on mixed diet intake, milk production, and blood metabolites of lactating cows

Abstract The objective of this experiment was to determine the effect of concentrate pellets, typically supplied by a voluntary robotic milking system (VMS), on milk production and composition, nutrient metabolism, and diet dry matter intake (DMI) of lactating dairy cows. Holstein cows (n = 24) were assigned to receive either no supplemental pellets (CON), 2 kg/d (LP), or 6 kg/d (HP) in addition to ad libitum diet access, with treatments balanced by lactation number and days in milk. The LP group was allotted 1 kg of pellets every 12 hours and the HP group was allotted 2 kg every 8 hours, to simulate the amount consumed while visiting a VMS unit two or three times daily. Pellet and diet consumption were measured using the Insentec feeding system. Milk production was measured daily, utilizing a milk meter in a conventional parlor. Milk samples were collected twice weekly for 35 days and analyzed for components. Blood samples, body weight, and body condition scores were obtained weekly after the morning milking. Data were analyzed using a mixed model (SAS 9.4) with fixed effects of treatment, day, and their interaction, with day as a repeated measure. No treatment × day interaction was present for diet DMI (P = 0.72); however, addition of pellets to the LP and HP treatment groups decreased diet DMI when compared to CON (P < 0.006). Plasma lactate tended to be greater for CON (P = 0.09) than LP and HP treatment groups with no treatment effect on other blood metabolites (P ≥ 0.30). There was no effect of treatment on milk yield, milk components, or body weight and condition (P ≥ 0.23). These data suggest that feeding a pellet similar to conditions in a robotic milking system could alter DMI without negatively impacting metabolism or milk production.