If the cow experiences
a nutritional deficiency at
any point in the gestational
period, the fetus receives a
metabolic signal through
blood flow to the placenta.
Fetal programming causes
the fetus to adjust to the
nutritional restriction. The
developmental process under
way in the fetus at the time of
the restriction may affect the
ability of the fetus to reach its
full genetic potential.
“Because muscle fiber
numbers do not increase
after birth, the fetal stage is
crucial for skeletal muscle
development,” says Funston.
“Because skeletal muscle is
a lower priority in nutrient
partitioning compared with
the brain, heart, or other
organ systems, it’s vulnerable
to nutrient deficiency.”
As a result, the calf may
be born with reduced
muscle mass, thus, express-
ing reduced performance in
growth and carcass develop-
PROGRAM CALVES TO DO WELL A COW’S DIET
DURING PREGNANCY INFLUENCES THE PERFORMANCE OF HER CALF.
C
utting corners on cow nutrition may save on feed costs
in the short term, but the long-range consequences could
be more costly and more far reaching than expected.
Research has shown that calves born to cows whose
diets were nutritionally restricted during gestation
experience long-term losses in performance, as compared
with progeny born to cows receiving 100% of their nutritional
requirements throughout gestation.
“Studies reported instances of compromised maternal nutri-
tion during gestation resulting in increased neonatal mortality,
intestinal and respiratory dysfunction, metabolic disorders, de-
creased postnatal growth rates, and reduced meat quality,” says
Rick Funston, University of Nebraska reproductive physiologist.
nutrition is important at every stage
I
dentifying the stage of gestation most nutritionally critical
for the fullest development of the fetus is more elusive than
nutritionists earlier thought. “Different systems develop at
different times in the fetus, so there’s the potential for these dif-
ferent systems to be affected by the dam’s nutrition at different
times during gestation,” says Funston.
Limb development, for instance, begins as early as day 25.
Sequential development of other organs soon follows, including
the pancreas, liver, lungs, thyroid, spleen, brain, and kidneys.
“Testicle development begins by day 45 in male calves, and
ovarian development begins in female calves between day 50
and 60,” he says. “Another important event in female gonadal
development occurs about day 80 of gestation, when follicles
are formed that after puberty affect what’s known as the ovar-
ian reserve. This can influence a heifer’s reproductive lifespan.”
Photography: Jody Korthaus
ment. The accumulation
of intramuscular fat can be
reduced, as well.
The fetal stage most
nutritionally important to
the development of muscle
mass is the second to seventh
months of gestation. The
third trimester is the most
critical for the development
of marbling in the offspring.
One study compared the
performance of calves born
to cows grazing native range
during the fourth to sixth
months of gestation with the
performance of calves from
cows grazing improved pas-
ture during the same period.
Calves born to the cows
grazing native range had
a weaning weight of 534
pounds, a hot carcass weight
(HCW) of 726 pounds, and a
marbling score of 420. Calves
born to cows on improved
pasture had a weaning
weight of 564 pounds, a
HCW of 768 pounds, and a
marbling score of 455.
Like steer performance,
the conception rate of heifers
suffered, too, from nutri-
tional restriction of dams,
according to another study.
The pregnancy rate of heif-
ers born to cows grazing
dormant range during the
last third of gestation was
only 80%. Conversely, heifers
born to cows supplemented
with protein under the same
conditions had a pregnancy
rate of 93%.
Cows appear to meet the
nutritional needs of the fetus
when they are maintained in
a body condition score of 5,
says Funston.
LEARN MORE
Rick Funston
308/696-6703
[email protected]
58 Successful Farming at Agriculture.com |August 2019
b e e f INSIDER
®
H E A LT H
By Raylene Nickel
