WHICH COWS ARE EARNING THEIR TIME IN THE ROBOT?

I have spent many hours, in many different farm offices, discussing the fate of top producing cows that take too much time in the robot. Maybe they dance and kick so attachment takes longer, or maybe their teats restrict milk flow. If they take twice as long as other cows, they need to produce a lot more milk than other cows to earn their time. You can balance production, speed, and behavior, with a weighted index, much like the genetic indexes for TPI or Net Merit.

Milk Production

Milk production needs to be projected beyond the current 7-day average. A seven-day average yield will penalize very early and very late lactation cows. If you don’t have access to a 305-day prediction, you can use milk per productive day. Subtract the age in days at calving from the total age in days to get productive days. Divide lifetime milk by productive days to get milk per productive day. I prefer to exclude cows under 50 days in milk – they will be at a disadvantage before peak production and they shouldn’t be candidates for voluntary culling anyway.

Milking Speed

Many of the cows with the shortest box time are the lowest producing cows and many of the cows with the longest box time are the highest producing cows. The index metric needs to include the flow rate, but it should also include the attach time. For DeLaval, harvest flow is the production per milking divided by the box time. For Lely, milk yield per box time is similar. Those metrics will combine milk yield and box time.

Behavior

One of my robotic milking mentors explained that he does not have time for the cows that damage his equipment. Cows that didn’t stand still didn’t have a place in his barn. A combination of kickoffs and incomplete milkings indicates which cows don’t behave in the robots or don’t have the right teat size and placement for efficient robotic milking. Incompletes are a bigger problem than kickoffs, so my behavior score uses incompletes multiplied by 5, plus kickoffs. Kickoffs waste time but the cow can still milk out if cups are reattached. Incompletes result in wasted time and lost milk production. You could argue that behavior is counted twice in the composite score, because incompletes and kickoffs result in longer box times.

Putting it all Together

Each trait is assigned a factor which determines its contribution to the index. A larger factor results in a bigger contribution. Higher incompletes and kickoffs should result in a lower score so the factor is a negative number – but a larger negative value still has a bigger contribution. The table below shows 2 cows with the same lifetime daily production. Flo ends up with a higher score because she milks faster and behaves better. I originally separated mature cows from heifers when I set this up in Excel, because I expected this index to favor mature cows. The average scores were almost the same for both groups so I  combined them and ranked the whole herd by composite score. Your final culling decision should also be based on age, health, and reproductive status.