CONCEPTIONS Dairy route newsletter Nov Dec 2024
Mark Curry (989) 984- 7027 Route services and sales / Ov Synch AI by
appointment
Sue Palen (989) 277- 0480 Office manager, product sales
Greg
Palen (989) 277- 6031 “aAa” Breeding Guide / certified forage
seed specialist
Mich Livestock Service, Inc “For the Best in Bulls and High
Energy forages”
110 N Main St (PO Box 661) Ovid,
MI 48866 ***
phone (989) 834- 2661
email: greg@michiganlivestock.com website:
www.michiganlivestock.com
Why is it
mostly in the Holstein breed that we collect data on calving difficulty? The only way to explain it is to compare
with other breeds, and then to suggest the impacts of indexing as it culled
some bloodlines while multiplying others.
Comparing
familiar breeds. Holsteins and Brown Swiss have the largest
frames, also had the longest length of gestation (time a cow carries the calf
before birth). Historically, Brown
Swiss cows carry calves 288 days; a
Holstein cow 283 days; a Jersey cow 276
Days. For Jersey calves, they tend to
be born at 5% of mother’s mature
size. Thus they will weigh
around 50# when born (1000# mature size
x 5%: With 800# first calf heifers a 50# calf is
not an issue). Beyond the shorter
gestation (fewer days gaining weight inside the cow) Jersey calves also have
little to no fat reserve at birth
(their mothers provide it from higher butterfat% milk after birth)
(Jersey island has a very mild climate, so native Jerseys did not require extra
energy in winter at birth).
Smaller
frame size breeds (Jersey, Guernsey, Dutch Belted) tend to reach puberty
earlier, and also physically mature a year quicker than large frame
breeds: thus the first calf heifer is
more ready to have a calf at a younger age (many Jerseys calve successfully
prior to two years of age).
Holsteins,
in contrast, tend to be born at 7% of mother’s mature size. Thus they would weigh around 100# when born
(1500# mature size x 7%; with 1200# first calf heifers a 100# calf can be an issue). As
in all breeds, most of the calf weight growth comes in the third trimester, so rations
need to avoid being high energy to control calf size. Holstein calves will be born with a
significant body fat reserve (their origin in northern Europe by the North Sea
meant adaptation to cold weather climates, calves could stay warmer from
metabolizing the body fat). Holsteins
traditionally were slower to mature physically (mature cows usually 30% larger
than first calving heifers) so it was safer to breed them to calve their first
time after two years old.
Why do Brown
Swiss avoid calving issues in spite of longer gestation? They may be the oldest “pure” breed that
came to America. Originating in Alpine
mountain valleys, developed totally on grass for centuries, calving unassisted,
culled out hard calving lines before they came here.
How does
CDCI calculate “calving ease” today?
Geneticists are in essence mathematicians (data crunchers), not biologists
(good at observing behavior and seeking causes for effects). They were never happy with the “original”
calving ease data, because it depended on herdsman observation (did she calve by herself easily? Or did she calve safely with mild
assistance? Or was she going to die
calving without assistance?)
The first
enhancement to farmer observation was to calculate Stillbirth rates. If a calf is born dead, they assume she had
a “hard calving”. There were many “calving ease” bulls (I recall “Morty” and
“BW Marshall”) who lost their calving ease designation with this change. More importantly, they learned that calf
livability was genetically influenced.
The next
(and equally important) enhancement was the realization that Gestation length was genetically influenced too. Shorter gestation became used to enhance
calving ease (geneticists preferring a “statistic” over “observation”) and is
now a big part of the calculation.
At this
point, the hubris of CDCI (Council for Dairy Cattle Improvement, which
took over from AIPL- USDA Animal Improvement Programs Laboratory with
the introduction of Genomics) says “we have solved calving ease”. According to the data trends, average difficult births fell from 8.6% (pre
genomic) to 2.3% … Genomic procedures
have “identified the genes for calving ease”.
A word about
CDCI (an uneasy partnership between
purebred breed associations and invested AI bull studs focusing on Genomic
selection) -- their calculations for DPR
(daughter pregnancy rate) do not sort between “natural” conceptions and
“OvSynch” conceptions. Likewise their
calculations of “calving difficulty” do not sort between gender-selected calves
and conventional semen calves; but in herds that participate in DHIA data
collection, “OvSynch” reproduction and using “sexed” semen on virgin heifers is
the “norm”….
Feeding
for easier calving
What you feed your heifers in the third trimester (last three months of
gestation) when 75% of the calf growth occurs in utero has a big influence on birth weights and thus calving
difficulty. That calf is growing 2+
pounds per day in the last two weeks prior to birth. High starch energy TMRs (higher in corn,
oilseeds, commodity energy sources to force size into younger heifers) are
going to produce larger calves than you will get from heifers grown out on high
forage diets.
For crossbreeders,
if you are using any breed that originated in a region (like France?) where it
is not customary to feed corn and soybeans, you might get calves 40%
heavier from a corn based TMR than a forage based feed regimen; you may also see excessive fat deposits
in their udders as well as within the pelvis, making calving and then
rebreeding more difficult. It required
two decade of genetic selection to produce Holsteins and Jerseys in the USA
that could eat corn and oilseed-based rations and make milk, instead of getting
fat OR sick… the linear trait
system that CDCI champions was first designed to identify the physical
cow that would make milk from corn.
Genetic
selection affecting calving ease
Holstein USA
released a study several years ago indicating that the breed average Stature was
increasing at a rate of 2 inches per generation. Why would this happen? Before Genomics was introduced, the “TPI”
selection index favored Stature in type classification, and was more focused on
PTA Milk yield than the “Net Merit” index (focused on PTA Butterfat and
Protein).
Because PTA
milk yields were in “Mature Equivalent” rather than actual yield volumes, this
was giving an advantage to the faster maturing sire lines. These tend to have Tall features
(within “aAa” observation), a quality gene-linked
to the production of “growth hormone”.
Once we had DNA testing, and Genomic indexing put higher weights on
“health and fitness” traits, these sires tend to have Strong
features (within “aAa” observation).
The combined direction for the two qualities mentioned is to produce larger
cows at younger ages (outgrowing older facilities).
The biggest
genetic impact on calf size is (as suggested earlier) mother’s expected
mature size. Without selection
in favor of shorter gestation (and low energy density feed in third trimesters)
we would generally be seeing larger calves from Holstein heifers; thus there is risk in breeding Holstein
heifers to calve before two years of age.
The general “safety” rule is to wait to breed heifers until they are
55% of their expected mature weight. Measure your cows to figure it.
Breeding
for easier calving
Every
breed has difficult calving individuals (no single breed “insures” calvings will
always be easy—although Jerseys come pretty close). When we approach these cows using the “aAa”
breeding guide, we can identify what causes problems and identify the
kind of bull that prevents heifers having the same problems.
The “aAa” breeding
guide regulates the
frame proportions in your cows. This can really be
seen in the pelvic structures of cows produced from “aAa” matings. At Mark Yeazel’s “Ja Bob” herd dispersal one year ago, a
retired sire analyst (serving as a ringman) told me “I can always tell when a
dairyman has used “aAa”, their cows will have a correct Rump structure”. Herds
bred for Genomic “Net Merit” are showing tight hips, which
narrows rump width regardless of how “Open” the rear skeleton appears. (Over
multiple generations, basing selection purely on Genomic ranking might turn “dairy”
cows into beef-framed cows!).
Basically,
after three generations of Genomic selection based on a single selection index
without regard to physical mating, your herd will begin to show “inbreeding depression”. Research into inbreeding lists lost natural
fertility, more calving difficulty, and higher stillbirth rates as some of the
consequences. Single trait
selection is known to be the true cause of “inbreeding losses”. Because “aAa” guides you to a
“heterosis” physical mating, it is the industry’s most reliable and practical
method to avoid “inbreeding depression” effects, including difficult heifer
calving.
