New employees receive training, why not train heifers for the milking parlor, too?
Imagine you are starting a new and unfamiliar job and, even though you were not told where to go or even what you are supposed to do, your new boss almost immediately starts getting restless and yelling at you for holding up everyone else. That sounds not only a bit crazy but also pretty stressful, right? Yet somehow this is similar to what can happen to freshly-calved heifers. We expect them to be as efficient in their new job as mature cows (often without any training) and there is commonly not much patience for their anxiety and jumpiness.
We forget that, on most farms, fresh-calved heifers have never been in the parlor and everything (sight, smell, sound) is new to them. On top of everything else, they are suddenly touched in places they have not been touched before. Understandably, this can be a bit overwhelming and stressful and can have more impact than we would expect.
Fight or flight?
The physiological reaction of the body to acute stress or fear is the release of adrenaline and cortisol to prepare the animal for a fight-or-flight response. The heart rate goes up and heifers react to parlor stress either by being petrified or they start defecating or kicking or trying to escape. Since cows are herd animals, the behavior of such a stressed heifer will directly impact the stress levels of its herd mates.
Besides these behavioral effects, the stress hormone cortisol also has receptors in an area of the brain (lateral amygdala) that is responsible for fear memories. Fear memories are long lasting and difficult to overwrite because, during evolution, it was important for survival to instantly recognize previously dangerous situations so that the animal had a chance to escape. Therefore, if heifers have a poor first experience in the milking parlor, they will perceive the parlor as a stressful place and they will be hesitant at future visits. It will take quite some time and effort to change their parlor association to anything but fear.
This is important, because stress impacts not only the behavior of cattle in the parlor, but it will decrease the cow flow into the parlor and impair milk production and the quality of the milk. For instance, urine of stressed animals contains alarm substances that warn other cows about a stressful area and will slow cow flow into the parlor, even after the stressed animal is gone. In addition, stress hormones impair the oxytocin release from the brain and adrenaline constricts the smooth muscles of the major milk ducts; both clearly impair milk let down. As if this were not bad enough, acute stress has been shown to increase somatic cell count in cattle (gently handled cattle had lower somatic cell counts).
The stress can start in the home pen. Preliminary data of a recent study showed that the frequency of handling errors and cow escape behaviors in the home pen affected cow behavior in the holding pen and parlor. The more errors were observed, the more cows turned away from the parlor entry or defecated in the parlor.
This stress around milking or through handling should be avoided. Ideally heifers would be exposed to the milking parlor prior to calving on several occasions. Cattle need more than a few exposures before they become fully used to something. Some herds successfully send their heifers through the milking parlor several times during the close-up period. For instance, they make heifers walk through the parlor, including a brief restraint, on the way to the foot bath. This gives the heifers the opportunity to become used to the parlor environment without the time pressure during a normal milking shift. Once the heifers are calm, some producers additionally apply teat dips – which gently acclimates the heifers to being touched at their udders. This has the added benefit of aiding in mastitis prevention.
Studies have shown that training heifers for the milking parlor or procedure does indeed reduce aversive behavior of heifers at their first milking. However, while the exposure of heifers to the milking parlor would be the gold standard, it is not always feasible. Therefore, other studies found that gentle interactions, such as the stroking or brushing of pre-fresh heifers in their home pen, also had a positive impact on the behavior of heifers after calving.
Regardless of the type of interaction with or training of the heifers, positive interactions resulted in positive behavior changes in the heifers at first milking in every study. Heifers were less likely to defecate or kick and showed better milk let down compared to the control heifers. Furthermore, it is safer and more comfortable for milkers to work with them.
In conclusion, dairy farms should try to find a way to positively interact with their heifers prior to calving to reduce the number of new stimuli for heifers going through the milking parlor. It will positively impact their cow flow, milk production and worker safety.