Replacement heifers are vital to the future of a dairy herd, but keeping too many can be costly.
“Heifers are the second highest expense in dairies,” Michal Lunak, a Penn State Extension dairy educator, said in an Oct. 28 webinar.
Farmers pour $1,500 to $2,300 into a replacement heifer before she even starts producing milk. And heifers don’t usually pay for themselves till the second lactation, Lunak said.
Keeping only the heifers a farm needs can save time and money on feed, labor and fuel, and reduces the amount of manure the farm has to manage.
If herd expansion isn’t in the plans, extra heifers are best sold at 6 months of age or earlier.
Heifer prices are low right now, so farmers who hold on to their spare heifers too long won’t recoup their feed costs, Lunak said.
That advice assumes farmers are tracking the number of heifers they produce and know how many they need.
Lunak offered this equation to find out the number of cows they need to replace each year:
(Herd size including milking and dry cows) × (cull rate) × (age at first calving ÷ 24) × (1 + noncompletion rate for heifers)
The cull rate includes cows that die. The noncompletion rate covers heifers that are born alive but are sold or die before they calve.
Lunak uses this equation for the number of heifers produced:
Herd size × (12 ÷ calving interval) × (percent female calves) × (1 – calf mortality rate) × (24 ÷ age at first calving)
The calf mortality rate counts deaths in the first 48 hours after birth.
To choose which heifers to cull, farmers can look at age, genetic quality of the sire and dam, body condition, and health.
Respiratory, reproductive, and foot and leg issues are particular red flags.
Getting rid of heifers isn’t the only option, Lunak said.
If farmers want to keep the heifers but are short on space or time, they can consider sending the animals to a heifer raiser.