While overstocking lactation pens is a common practice on many dairy farms to optimize milk production and income, new research suggests it could be jeopardizing long-term cow health and putting more cows at risk.
Rick Grant, a dairy nutritionist at the William H. Miner Agricultural Research Institute in Chazy, N.Y. and fellow nutritionist Mac Campbell conducted research that shows higher stocking density and restricted feed access increase the risk of sub-acute rumen acidosis (SARA) with greater time spent below rumen pH of 5.8.
Tight economic conditions also mean farmers are feeding for fewer refusals in an attempt to reduce feed wastage. But the combination of overcrowding and feed restriction can have profound negative consequences on rumen pH. If cows are overcrowded and don’t have access to feed, they tend to eat less frequently but over-eat when they can reach feed. That can result in rumen upset.
If feed is not pushed up frequently or bunks are empty for more than three hours, cows may injure themselves as they attempt to reach for more feed. Research shows cows can exert 500 lb of force against a feed barrier in attempt to reach feed. Less than half that amount of force can cause tissue damage.
“Even more importantly, a feeding environment that chronically frustrates a cow’s drive to access feed may train her over time to become a less aggressive feeder,” says Grant.
Subordinate, low-ranking cows also don’t like feeding near dominate cows. A study done by Canadian and British researchers in 2012 showed that when given a choice of a highly palatable feed near a dominant cow or a low palatable feed further away, most subordinate cows chose to eat the low palatable feed alone.
Even when bunk space was 2’ to 2 ½’ per cow, 40% of the subordinate cows still chose to eat the poorer feed further away. “If you ask the cow based on research results, the answer is ‘no’, 2’ per cow of bunk space is insufficient for optimal feeding behavior,” says Grant.
If overstocking can’t be reduced, it’s critical that feed be readily available. Research shows that delivering freshly-mixed feed twice a day is preferable. One study showed a 3 lb increase in dry matter intake (and a 4.4 lb increase in milk production) with twice-a-day feeding.
“With 2X feeding of a TMR, more feed was available through out the day and there was less feed sorting,” says Grant. “The positive response to greater feeding frequency is more noticeable during heat stress conditions.”
Pushing up feed is also essential, he says. “When deciding a feed push up strategy, focus on ensuring that feed is easily within reach of the cow during the highly competitive two hours following feed delivery,” says Grant.
Ideally, feed should also be pushed up every three hours. Nighttime is critical. In another study, when feed wasn’t available from 8 p.m. to 6 a.m., feed intake dropped 3 lb and there were twice as many cow displacements at the bunk as cows competed for feed once it was delivered.