The Cost of More Milk
When evaluating sire EPDs, producers may be tempted to select for increased milk production in their herds based on the thinking that more milk equates larger calves and heavier weaning weights.
But how does selecting for increased milk production impact overall production costs?
This is a question that Assistant Professor and Range Cow Production System Specialist at the University of Nebraska-Lincoln, Travis Mulliniks, has been researching and presented on in last summer’s annual Beef Improvement Federation Research Symposium.
“When I think about milk production and calf size, I think about more than just the output,” Mulliniks explained. “You really have to think about the production system because once I make a change in my system—to a selection or management—it impacts the whole production system. So, whether or not we change calving season [or] we change selection for increased milk production or growth, we’re changing the whole system and how we manage around that system.”
Some changes that may result from selecting for increased milk production include the changes in forage intake, available nutrients, breed back/pregnancy rates, and the calf’s future feedlot needs.
“Forage intake is driven off of requirements. The two things that change intake is cow size and the level of milk production,” Mulliniks said. The more milk an animal produces, the more forage they’ll need to consume.
Hypothetically, if a producer were to select for increased milk production, their carrying capacity would be reduced due to higher consumption rates.
“Lactation is one of the first places that nutrients are used,” Mulliniks stated. This is “well before body weight or any reproductive trait.”
Increased forage intake to support lactation could cause cattle to be less resilient to drought conditions.
Mulliniks explained that “We’re running a bigger production risks when we start selecting for increased milk, specifically in areas that may have an increased occurrence of drought—we’re decreasing flexibility in those production systems”
Another issue from a nutrient and reproductive standpoint, is that many environments don’t have enough nutrients to support a positive energy balance throughout the entire breeding season or multiple reproductive cycles.
Mulliniks explained this net energy balance during breeding seasons in the Nebraska Sandhills in his presentation. The data he presented showed that for cattle calving in March, the available forage kept those cattle in a positive net energy balance for one cycle only. Cattle with a high level of milk production fell into a negative energy balance more quickly than moderate to low milk producing cattle. The cattle with a lower milk production had a positive net energy balance for a cycle and half, but then also fell into a negative energy balance. This trend would lead to producers seeing cattle breed back in the first cycle or not getting bred at all.
“Reproduction is five times more economically important than traits like milk production and calf growth,” Mulliniks stated.
This is an important factor to consider when selecting for milk because increased milk production can cause strain in other areas.
On the calf side of the equation, Mulliniks explained that a cow’s milk accounts for 85% of the calf’s energy levels at 45 days of age. Once they reach day 205 or weaning age, only 19% of their energy is coming from the cow’s milk. The rest of their energy requirements must be met by forage.
Some studies have shown that a cow’s level of milk production can continue to impact her calf once they reach the feedlot.
“Offspring from lower milking animals are more efficient from a growth aspect for post weaning than their counterparts,” Mulliniks said. “What’s driving that is offspring from high milking [cattle] have increased energy requirements. They have increased organ mass and size, so it’s increasing energy requirements.”
For milk production related studies researchers, like Mulliniks, use dairy milking machines to measure a cow’s output in a 24-hour time-period. This figure is labeled as pounds per day. However, without equipment, milk production is difficult to measure for producers.
If producers wanted to really assess milk production, they could use a weigh suckle weigh method which uses the calf as a milking machine, but even that would have variations in accuracy.
Mulliniks cautioned against simply equating udder size to milk production. A large udder could imply a higher milk producing animal, or a large udder could contain a deceitful amount of fat and actually be producing lower levels of milk.
Producers should also know that milk EPDs don’t match milk production exactly. In other words, it is not a one-to-one ratio or EPD point to pound of milk per day. EPD’s should be used as general guidelines, not an exact expectation.
As with any major production decision, it is important to weigh the costs and implications before making a selection.
[Milk production] is a very important topic that we have to be careful with because when we start selecting for things like milk, our selection today influences our production for several years,” Mulliniks explained.
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