Effect of two milking systems on the milking characteristics, teat tissue changes and new infection rate of dairy cows.

摘要

Holstein-Friesian dairy cows (n=56) were assigned to either of two milking systems over a complete lactation. System WB consisted of a heavy cluster weight of 3.2 kg with a claw volume of 150 mL, wide-bore tapered liners (31.6-21.0 mm) and a simultaneous pulsation pattern. System NB used a light cluster weight of 1.65 kg with a claw volume of 275 mL, narrow-bore liners (25.0-21.0 mm) and an alternate pulsation pattern. All cows were managed as one herd and milked in an 80-degree side-by-side milking parlour, with a milk lift of 1.5 m above the cow standing. Comparison was made between systems for milking characteristics and intramammary infection. Ultrasonography was used to measure changes to various teat parameters and external teat condition was assessed visually. Mean milk yield, milking rate, peak milk flow-rate, gross milk composition, and somatic cell count were similar for both milking systems. However, milk yield tended to be higher (by 5.2%; P=0.09) at the morning milking with WB as compared to NB. There was a significant milking system x lactation stage interaction (P<0.01) for somatic cell count and for peak milk flow-rate at the morning milking. There was no difference between milking systems in the incidence of clinical or sub-clinical mastitis, teat texture or colour. There was a significant lactation stage interaction (P<0.001) for external teat diameter, cistern diameter and teat wall thickness. There was system x lactation stage interaction (P=0.08) for teat diameter with the WB system tending to be higher as compared to the NB system, however these changes did not result in higher infection rates or have any deleterious effect on teat condition. The two milking systems gave satisfactory milking performance..