Randomized controlled study assessing the effect of milking permission settings and concentrate supplementation on milking frequency and milk yield in a pasture based automatic milking system

This study aimed to verify the impact of milking permission (MP) and concentrate supplementation (CS) on milking frequency (milkings per cow/day) and milk yield (kg per cow/day) in a farm using a pasture-based automatic milking system (AMS). Sixty-eight cows milked using this AMS unit were randomly assigned to one of 4 groups homogeneous for parity, days in milk and milk yield. Treatments used were: Frequent (F) or Restricted (R) MP, that granted cows permission to milk after 6 to 8 h or 9.6 to 14 h of the previous milking, respectively; and low (LC) or high (HC) CS of 0.5 kg or 3.5 kg per cow/day, respectively. The combination of the 2 levels of MP and the 2 levels of CS resulted in the 4 treatment combinations (FHC, RHC, FLC, RLC). This study was designed as a 2 X 2 factorial arrangement with treatment crossover: each of the 4 cow-groups was randomly assigned to one of the 4 treatment combinations for a 5-week experimental period (one pre-treatment week and 4 treatment weeks), and after each 5-week period groups crossed over to another treatment combination until they experienced all.Statistical analysis assessed the impact of MP, CS and their interaction on milk yield, milking frequency, box time, milking time and average milk flow rate. This was done using a mixed model analysis with repeated measures to account for repeated observations on the experimental unit (cow). Milk yield per cow/day and milkings per cow/day were significantly higher with the Frequent compared with the Restricted MP (1.5 kg and 0.65 respectively). Milk yield per cow/day and milkings per cow/day were significantly higher with the HC compared with the LC CS (3.1 kg and 0.25 respectively).Additionally, milk yield per cow/day was affected by the interaction of MP and CS and it was highest with the FHC (20.1 kg) treatment combination, followed by RHC (18.2 kg) treatment combination. The number of milkings per cow/day were also affected by the interaction of MP and CS. The highest estimated number of milkings per cow/day was recorded for the FHC (2.12) and the FLC (1.77) treatment combinations, followed by the RHC (1.38) and RLC (1.23) treatment combinations. Similarly, milking interval was 2.5 h longer for the RLC treatment combination compared with RHC. The shortest milking interval/milking was observed for the FHC (11 h) and FLC (12.8 h) treatment combinations.In conclusion, the study showed that allowing access to the robot between 6 to 8 h after the previous milking was sufficient (even with a minimal level of CS) to achieve acceptable milk production and milking performance in a pasture-based AMS.