Well-being linked to cluster type position
HEAVY clusters milk cows out more efficiently but increase tendency to overmilk, causing cows to be agitated.
This means milking with heavier clusters demands more attention, according to a Milk Dev-elopment Council-funded study reported that was presented at the conference by ADASs Ian Ohnstad.
The ADAS, SAC and Institute of Animal Health study, which observed milking in 20 new parlour installations, found that the relationship between cluster type and the cows well-being were complicated and involved many factors. Parlour indexing, backing gates, vacuum level, pulsation and operator routine affect the performance of cluster type, he told delegates.
Although heavy clusters – over 3.2kg – milk cows out better, especially when producing lower yields, there was more dunging and kicking at clusters. However, this may be due to a tendency to leave clusters on for longer or to have higher vacuum level. When the operator reduced overmilking to a minimum, cow behaviour improved.
Reductions in overmilking are helped when the parlour has a backing gate, improving cow entry and allowing the operator to spend more time in the pit, he added.
Good cluster position helps ensure even milking, but was usually best in indexed parlours when cows were well positioned.
Heavy clusters milk the cow more completely irrespective of postion, but didnt ensure adequate position. With lightweight clusters weighing about 2.4kg, milking completeness reduces as position deteriorates, he said.
"Cluster position was poor when long milk tubes were unsupported. Length was dictated by wash line level or when it pulled the claw back." This took weight off front teats, adding weight to back quarters or resulted in liners not hanging vertically, causing incomplete milking.
In the study, teat condition at the end of milking was measured by teat colour change, red or blue teats taken as a possible indicator of impaired circulation in the teat during milking, said Mr Ohnstad
Fewer than 50% of cows had red or blue teats after milking on 11 of the 12 farms with light clusters. But seven of the eight farms using heavy clusters recorded 76% to 100% of cows having red or blue teats after milking; on the eighth farm an efficient routine resulted in just 59% of cows showing teat discolouration. *