Improved milking characteristics of teatcups fitted with non-return valves

The milking characteristics of conventional clusters were compared with individual teatcups or clusters fitted with valves in the short milk tubes without external air admission to the liners. Individual teatcups fitted with non-return valves had peak milk flow rates 13% higher than conventional teatcups. A daily cross-over experiment involving 36 cows compared clusters fitted with non-return valves to conventional clusters. Valved clusters milked 18% faster, showed significantly better teatcup stability and 3% higher machine milk yields, but 48% higher strip yields were recorded. Clusters with non-return valves were difficult to remove after milking because the valve closed when the vacuum supply was shut off, thereby maintaining the vacuum level under the teats. When the nominal plant vacuum level for teatcups with non-return valves was reduced by 10 kPa to compensate for the higher effective milking vacuum level, the valved teatcups had peak flow rates 20% lower than the conventional teatcups. Clusters fitted with a modified valve, which allowed some reverse flow when closed (a ‘leaky’ valve), milked significantly faster than conventional clusters, had 33% lower strip yields and were easy to remove after milking.