Gestation Length

KEY PROFIT DRIVER!

Written by: Tim Weller Technical Sub Committee Gestation length (GL) can be defined as the period from the date of conception (i.e. when the female gets in calf) to when the subsequent calf is born. GL EBV is expressed in days shorter or longer than the average gestation. Shorter gestation length is generally associated with lighter birth weight, improved calving ease and improved re-breeding performance among dams. In addition, calves born with a shorter gestation length may be heavier at weaning due to more days of growth post-birth. “Breedplan website”

Fertility and maintaining a tight calving pattern are key profit drivers, and anything we can do to improve our chances of more calves born early in a calving period, giving the cow more days to recover and become pregnant, while producing a heavier weaner at weaning, all add dollars, especially at today’s market.

Alastair Rayner of Rayner Ag comments in his article “Advantages to a shorter gestation length” 20/7/21 to maintain a 365-day calving pattern, a cow only has 33 days to conceive, considering a typical 282-day gestation, and a 50 day recover period after calving.

In many of the presentations Dr Enoch Bergman of Esperance WA has given, he has promoted the fact of late calving heifers struggle to ever catch up in overall lifetime profitability and has proven the advantages of incorporating Fixed Timed AI programs with short gestation length bulls to gain kg’s of beef produced and more pregnant cows, creating more profitability.

Bob Bellows of Fort Keogh Research Center at the US Department of Agriculture has shown, that during that last 10 days of gestation, a calf can add 1-1.5 lbs/day (0.45-0.68kg/day), therefor the more days of gestation, the higher the chance of assisted births.

Currently the Speckle Park Breedplan data is extremely reliable for Birth Weight, compared to all other Breedplan traits including Gestation Length. Although both are very highly correlated, significant dollars of profit for the commercial beef producer are begging if we only concentrate on birth weight.

How do I record Gestation Length Information?

All that is required to be included is the mating date on either the excel form or ILROnline form when submitting calves for registration. Only matings from AI or hand bull mating’s when a known date is possible, and more than 2 calves are in a contemporary group are eligible to be included in Gestation Length data on Breedplan. We understand Speckle Park has a significant number of ET calves born, ET causes a significant variation in gestation length of +/-7 days and often longer, hence why ET calves are not included in Gestation Length EBVs.

Of the 3050 calves registered in 2021 only 398 where a result of AI, considering the disproportionate use of ET & natural service compared to other mainstream breeds, we have a limited ability to capture this data, so we need to make the most of every opportunity.

Afterall the first experience a new commercial breeder has with Speckle Park is the calves hitting the ground, so we best make sure those calves are born easily, and the safest way to provide assurance is having data, and good data.