Influence of vacuum level, pulsation ratio and rate on milking performance and udder health in dairy goats

Abstract

Fifty Alpine goats in early lactation were used in a 98-day experiment to determine optimal vacuum level, pulsation ratio and pulsation rate for machine milking. Treatments consisted of alternating vacuum levels (38, 45 and 52 kPa) with pulsation ratios (50:50, 60:40 and 70:30), and pulsation rates (60, 90 and 120 pulse/min). Higher vacuum levels increased average and maximum milking rates (linear, P<0.001), decreased milking time (linear, P<0.001), and elevated somatic cell counts (SCC) (linear, P<0.05). California Mastitis Test (CMT) scores were lowest in goats milked with 52 kPa. Increasing the pulsation ratio from 50:50 to 70:30 speeded-up average milking rate and decreased milking time (linear, P<0.05). Maximum milking rate was highest while CMT scores and SCC were lowest in goats milked with a 60:40 pulsation ratio. Increasing the pulsation rate from 60 to 90 increased average and maximum rate and decreased milking time. No further improvement in milking rate was observed when pulsation rate was increased to 120. Lowest CMT scores were found in goats milked with a pulsation rate of 90. Average and maximum milking rates were lower in goats than in cows on a per teat basis. Milking time per animal was shorter in goats (1.4 to 2.3 min) than in cows (4.9 to 5.8 min) and was related to level of production. Correlation coefficient was +0.42 between CMT scores and SCC. Vacuum level of 45 to 52 kPa, pulsation ratio of 60:40 and pulsation rate of 90 pulse/min appeared to be optimal for machine milking of goats.