Shortening Gestation Length

Our 2021 calving at Te Mooi has just begun and, as for all producers, it’s an exciting time. For us this year it is more exciting than usual, as we’re expecting the first big drop of commercial calves from our co-operator herds in the TE MOOI CARCASE CREW.


What the hell is the TE MOOI CARCASE CREW, you might ask?

The "Te Mooi Carcase Crew" is a group of commercial breeders who have introduced Speckle Park genetics into their programs, and are recording data and finishing their animals for the Coles Graze (grass-fed program) and the Coles Finest (grain-fed program). We are conducting AI programs and single sire joinings, so that we can track the performance of individual bulls. We currently have herds in North East Victoria and Gippsland, and will look to expand the program in the future.


Te Mooi Mojito Q6 with her Minnamurra Pageant P216 bull calf born at 277 days gestation


The first interesting data we are going to get back is on gestation length. Because we have AI dates we can measure gestation length - one of the traits that’s at the core of our breeding objective of reproductive efficiency. Gestation length has a significant effect on dystocia and on post partum anoestrus.


Bob Bellows, a researcher at the Fort Keogh Research Center of the US Department of Agriculture (USDA) states that, “During the last 10 days of gestation, 1 to 1½ pounds of birth weight can be added to the size of the foetus. This means that for a calf that had a five day extended gestation, you could be adding as much as 8 pounds to the birth weight. This might mean the difference between an unassisted birth or a dystocia situation.”


According to Sally Northcutt, director of genetic research for the American Angus Association, breeding to short gestation bulls can shorten the postpartum interval and assist in earlier breed-back of cows. Northcutt states that research clearly shows young cows, and cows that have difficult and slow deliveries, require additional days of postpartum interval to cycle and rebreed. Gestation length is thought to have a heritability between 0.25 and 0.5, so selection for it has a significant impact. Easier calving and quicker breed back time are very important in our program.


Te Mooi Jani P4 with her Caja Zeppelin heifer born at 283 days gestation.


As I mentioned earlier, one of our core breeding objectives at Te Mooi is reproductive efficiency. In real terms this centres around producing females that conceive quickly, to calve at two years of age, have calves arrive easily and unassisted and rebreed quickly. Reducing gestation length has a positive effect on calving ease and the time to rebreed. It also allows for shorter joining and calving periods, which are proven paths to improved returns and lower labour costs. For a trait that costs nothing to select for, it has serious benefits. Just a quick aside, we have some calves by Caja Zeppelin 1B in our stud program and interestingly, to date with 90 registered progeny on the herd book, not one has had its gestation length data collected.


In a program selecting for growth and growth alone, it doesn't take many adverse outcomes to eliminate the benefits of the genetic gain aimed for. Maungahina Legacy, for example, is the number 1 AI sire in the breed for 400 day growth. He is +53 and breed average is +22. This means that on average, his calves at 400 days in the same environment will be 15.5 kilograms heavier (53 - 22 = 31/2 = 15.5) than the calves by a bull with a breed average 400 day EBV. The difference between the two EBV’s (53 - 22 = 31) is divided by two, as the bull provides half the genetic material to his progeny. A loss of about 3% of calves to 400 days nullifies this benefit completely. Whether this be a failure to conceive or lost at birth, the effects of less saleable calves is significant.


Shortening gestation length has a significant impact on the bottom line, and it has a tremendous emotional impact. If you have ever experienced a difficult calving season you will know the trepidation of each calf arrival. Ron Torell of the University of Nevada writes that “There are several variables that contribute to calving ease other than gestation length. I feel that many of the calving ease sires are so partially because they are short gestation sires”. We are all about this at Te Mooi. We want our clients to have the easiest calvings possible. We want their calving season to be filled with joy, not dread.


A Minnamurra Pageant P216 calf born at 278 days gestation.


Unfortunately not all seed stock producers feel the same. Only 6% of Speckle Park breeders who registered calves in 2019 submitted data for the measurement of gestation length. This makes it difficult to find reliable, shorter gestation length sires. This is one of the core drivers of our Carcase Crew program. We test a number of sires and record their actual gestation length. This data cannot be submitted to breedplan under the current regulations, but there are ways that this, and other data, could be included, and hopefully SPI can consider these in the near future.


Minnamurra Plunderer P196 will get significant use at Te Mooi and in the Carcase Crew in 2021. He is in the 20% of the breed for Gestation Length.


The bulls with progeny in the 2021 Carcase Crew are,

  • Promised Land Eldorado

  • Minnamurra Pageant P216

  • Wattle Grove Project A

  • Te Mooi Poseidon

  • Te Mooi Quincy

  • Te Mooi Predator

These calves will be weighted and scanned as they progress through the system, and then we will receive the carcase data from the processors. We will use this information to refine our program and to achieve our breeding objectives.


Our 2021 joinings will see the addition of

  • JAD Quinella Q21

  • Maungahina Perfect Storm P197

  • Minnamurra Plunderer P196

  • Maungahina Quarry Q204.

In time we hope that the actual carcase data from these types of animals can be included into Breedplan for all breeders to benefit from. Until then, we will collect the data, crunch the numbers and pursue a better, more profitable product for our clients.