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| Earlier than normal snowfall this year may necessitate feeding cows earlier than normal. Body condition score at calving impacts calf vigor and health and cow breed back next year. Photo by Kari Lewis. |
Kari Lewis, MSU Extension – Glacier County
Recently
as I looked through our cows, I was concerned about some of the cows’ body
condition scores. There’s multiple
factors that have had a role in our herd’s body condition being lower than I
would like to see. First, this summer’s
drought resulted in less forage than normal, then the early October snowstorm
hit the cows hard as well. In addition,
our weaning date was later than it should have been, which meant the cows were
also lactating longer into the fall, using additional nutrients to support
their calf at side. Not surprisingly, it
is our youngest cows who are the thinnest, as they’ve also been trying to grow
in addition to supporting their calf and developing fetus.
As cows
receive nutrition, they first use it for maintenance, then allocate the remaining
nutrients to support fetal development, lactation, growth, and lastly,
rebreeding. Thus, if a cow is short on
nutrition, the first thing to be impacted is her ability to rebreed. Therefore, it’s critical that we provide
adequate nutrition now to ensure cows are in an acceptable body condition to rebreed
next summer.
A body condition score (BCS) describes
the relative fatness or body condition of a cow on a scale of 1 to 9. A score of 1 means the cow is extremely thin,
and a score of 9 indicates a very obese cow.
Each body condition score translates to approximately 70 pounds, so to
increase a BCS 4 cow (on December 1) to a BCS 6 cow (by March 1) would require
that cow to gain 1.6 pounds per day, not including the increasing weight of her
fetus.
Why is
body condition so critical? Simply, thin
cows take longer to rebreed, produce less colostrum, and give birth to less
vigorous calves. Those calves that are
born weak at birth take longer to nurse, have lower immunoglobin levels which
lessens their ability to overcome disease, and are ultimately less likely to
survive.
A cow’s BCS at calving is a large
indicator of how soon she will rebreed following calving. A cow that calves in a BCS 5 or 6 averages 55
days following calving until her first heat, while cows that calve in a BCS 3
or 4 average an 80-day post-partum interval.
Knowing that we want those cows to have one or two heat cycles prior to
when they are bred, it’s easy to see why thin cows fall out of the herd. Data from Spitzer et al., 1995 showed that
first calf heifers that calved in a BCS 4 had a 56% pregnancy rate after a 60-day
breeding season, whereas those heifers that were in a BCS 5 at calving had an
80% pregnancy rate, and there was a 96% pregnancy rate in the heifers that
calved at a BCS 6.
The
period after weaning (when nutrient requirements are decreased) and before the
third trimester begins (when nutrient requirements increase again) is the most
economical time to add body condition. By
providing adequate nutrition, a windbreak, straw during cold weather, and access
to clean, fresh water, we can add condition to the cowherd to meet our breed
back goals for next year.
Here at the MSU Extension office in
Glacier county, we can assist you in formulating a ration for your
cowherd. We have two hay probes that can
be checked out to sample your hay for a nutrient analysis, and can use ration
balancing software to formulate a ration that will meet your cows’ protein and
energy needs. Please call (406) – 873-2239
or e-mail kari.lewis@montana.edu with
questions, I’m happy to help!
