Effects of machine milking on udder health in dairy ewes

Abstract

• Milking machine settings that increase vacuum fluctuations under the teat must be avoided to reduce the intramammary infection risk. • Although a high milk pipeline causes higher vacuum fluctuations at teat level, no relation with bulk milk SCC have been found. • Milking machine settings that increase teat thickness would reduce the local defence mechanisms and should be avoided. • Post-milking teat disinfection, milking animals with intramammary infections last, and avoiding over-milking for longer than 2 min can affect mammary gland health status by reducing the incidence risk of mastitis. The aim of this article is to review factors associated with machine milking that would increase mastitis incidence risk and the effects of milking machine, milking management and routine in sheep. Machine milking settings that increase vacuum fluctuations under the teat or teat thickness and help to disseminate infectious agents would increase the risk of intramammary infection. Vacuum fluctuations are caused by a low effective reserve, low air and milk line diameters, low milk tube diameters, sudden air leakages caused by high milking cluster weight, teatcup slippage, excessive liner mouthpiece diameter or inadequate machine stripping. The milk line height (low vs mid line) has no relation with SCC if the rest of the settings are adequate, although higher vacuum fluctuations have been recorded in high line. The settings that increase teat thickness include an excessively high vacuum level, lack of effective massage on the teat (high pulsation ratio), liners too soft, hard, narrow or old, and overmilking for longer than 2 min. Regarding milking management, the reduction of milking frequency to 1 milking per day has an effect on yield and SCC due to a concentration effect, and some milking practices such as post-milking teat disinfection or milking animals with intramammary infections last, despite the drawbacks in overall farm management (identification and separation of infected animals), can lower the risk of mastitis incidence.