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.
