Heifers that become pregnant within the first 21 days of their first breeding season wean the equivalent of three-quarters of another calf during
their production lifetime, compared to heifers that didn’t conceive until after 21 days.
“We decided that from a production standpoint, the number one
thing we needed to select for was pregnancy,” Lamb says. He adds that
reproduction has four times the economic impact on herd economics
than any other trait.
Specifically, Lamb and his crew developed a set of non-negotiable
rules for cows to enter and remain in the herd. Every female must:
• Calve by the time she’s 2 years old.
• Calve every year.
• Calve without assistance—that includes replacement heifers and any
amount of assistance. Lamb explains that data indicates pregnancy
rates are 10% less in cows that require assistance of any kind.
• Provide sufficient resources for her calf to reach its genetic potential.
• Raise a calf genetically capable of performing to expectations. If a
heifer has a calf that doesn’t perform, the heifer is culled.
• Maintain the Body Condition Score for their conditions. That keeps
them away from having to manage more than one group of heifers
and cows in terms of nutrition.
• Be calm.
From a management standpoint, they followed these rules:
• Only heifers that become pregnant within the first 25 days of the
breeding season are considered as replacements.
• The breeding season will be tightened as much as possible.
• Every female is exposed to synchronization and artificial insemination
(AI). Rather than think of synchronization as way to get semen
in the cow or heifer, Lamb encourages producers to think of it as
reproductive technology that stimulates cycling.
With heifer selection and these rules in mind, Lamb emphasizes
their first criteria was breeding within the first 25 days. Rather than
select heifers and then hope enough of them get bred on time, they
synchronized and bred 90 heifers. Typically, 70-80 heifers were bred
on time. That left them 10-20 to cull based on other criteria in order
to arrive at the 60 needed replacements.
The results were stunning.
A higher percentage of cows and heifers calve within the first 30
days each succeeding year. After six years, calves were worth $169 per
head (price constant basis) more, much of it due simply to a higher
percentage of calves being born earlier in the season.
Reproduction has four times the economic impact on herd
economics than any other trait.
ABOUT THE AUTHOR: Wes Ishmael has been involved with
livestock publications since 1983. Wes grew up in Colorado and
has always been in and around the livestock business. He now lives
at Benbrook, Texas.
• JANUARY 2020
83