Handling Fetch Cows for Optimal Herd Performance
A fetch cow is a cow that does not come to the robot voluntarily to be milked within a certain interval defined by the producer. The benchmark for fetch cows in a robot milked herd is less than 5% of milking cows. Some references use less than five fetch cows/robot/day. Here we will look at how lameness, social dominance, mastitis and feeding related aspects have an impact on the number of fetch cows.
The degree of lameness and how that affects the cow’s behaviour and mobility is important in AMS herds. Lameness is a major factor limiting turns through the robot, especially on robots with a free flow layout. Lame cows tend to lie down more, providing stalls are available, and for longer periods. They also tend to be lower in the social order and this will reduce the number of turns or reduce their willingness to go up to be milked. Cows and heifers considered lower in the social order include fresh cows, 1st lactation animals and lame cows.
Social Dominance and Other Factors
One study demonstrated that the higher ranked, more dominant cows waited an average of 3.5 minutes to be milked while the lower ranked cows waited for up to 67 minutes before entering the robot to be milked. The effect of lower ranked cows as well as lame cows is exaggerated by over-crowding in the barn. Other factors which will add to the cows that need to be fetched, at least temporarily include introducing new cows into the group. Cows that calved after having been on the robot previously tend not to be as big a problem and often resume milking with little or no training required. Some cows, even after a month (by which time 95% of the cows should have adapted), do not adapt to the robot, for whatever reason, and may need to be culled.
In a study of clinical mastitis, milking interval increased by two hours/day one month before treatment for the mastitis was initiated. This suggested that the infection altered the cows’ daily rhythms and the increased milking interval may have further contributed to the development of clinical mastitis in quarters with sub-clinical mastitis. In the week before clinical mastitis was diagnosed and cows were treated, failed milkings increased from 5 to 30% indicating that mastitis has a significant effect on milking routine. This serves to emphasize the importance of timely intervention in mastitis cases since this may also contribute to an increased number of fetch cows.
Partial Mixed Ration (PMR) feeding – the bunk mix
Dr. Greg Penner from the University of Saskatchewan indicates that the primary goals of the feeding program within an AMS system is to meet nutrient requirements while encouraging cows to voluntarily enter the AMS thereby promoting frequent milking, high milk flow/h harvested in the AMS, and minimizing labour associated with fetching cows. He goes on to say that feeding cows in an AMS system can be a challenge since cows are fed a partial mixed ration (PMR) at the feed bunk and are provided concentrate in the robot. The division of the feed components into two feeding locations is used so that the concentrate can function as an attractant to encourage voluntary attendance to the milking robot. This relies on accurate prediction of dry matter intake (including the prediction of concentrate and PMR intake), the quantity and type of concentrate provided in the AMS, the composition of the PMR, and the targeted nutrient intake. In addition, research seems to indicate that motivation to milk is not as strong as the motivation to eat so this balance between the ration at the feed bunk and the pellet in the robot is an important one.
In free flow traffic systems, if the partial mixed ration (PMR) is too high in energy or grain level relative to the requirements of late lactation cows then these cows have their requirements met by the PMR and don’t readily go to the robot to be milked, increasing fetch cows. The level of energy of the PMR is not the only aspect that may limit visits to the robot though. It is important to push up feed every one to three hours throughout the day. Research shows that a cow’s milking behaviour could be manipulated through delivering fresh feed or pushing up feed. Some herds, using a robot to push up feed, will feed first thing in the morning and then have the robot push up feed every hour starting at about 10 am through to six or seven am when the fresh feed is delivered. The additional benefit to this regular push up is that cows that are milked between about 10 pm and 6 am always have feed within reach after they have milked (provided we are not feeding to an empty bunk). Cows milking during this time include (but not exclusively) heifers, lower ranked cows and very high producing cows. Pushing up feed ought to increase cow activity in the barn, increase cow turns through the robot and reduce fetch cows.
Another aspect that may make balancing a diet in an AMS system more challenging is the days in milk (DIM) of the herd. The shorter the DIM (say 140 to 160) the easier it is to balance the diet since most cows are on the same phase of the lactation curve and so the nutrient requirements are more uniform. If the herd has long DIM (>180) then it may be more complicated to balance the diet, due to the risk that those lactation cows get too much energy from the PMR and/or get too much body condition, and are not willing to go to the robot. For this reason, it is important to keep a good reproductive performance on an AMS operation.