Actually a 7 year property takes 8 tax years to fully depreciate ... look at the chart at the bottom of the screen ... but the 10 year reference is for the class life per the IRS regs ... look at the CLADR table on page 101 :
The recovery period should be 7 yrs using GDS correct?
Yes ... look at the CLADR table page 101. But because of the 1/2 year convention it takes 8 tax years to depreciate a 7 year property.
dmertz had reported it as an error, and they are now working on correcting it in a future update.
https://ttlc.intuit.com/questions/3402243-incorrect-recovery-period-for-horse-depreciation
Caveat: I know essentially nothing about depreciation other than what I read in Pub 946 as suggested by Critter#2. However, I experiment with TurboTax extensively.
It looks to me as though TurboTax has this all messed up. Using the desktop version of TurboTax to examine the underlying forms after using step-by-step mode to make an entry of a farm-business asset of a breeding or work horse 12 years old or less at the time it is placed in service results in the asset class set to 7 years and the recovery period set to 10 years, which seems to be backwards. Additionally, TurboTax's depreciation bar-graph appears to show a depreciation schedule based on the value that it has determined for asset class instead of the value for the recovery period, even though TurboTax uses the value that it has determined for the recovery period to determine the depreciation when preparing the actual tax return.
A workaround to get online TurboTax to use the proper 7-year recovery period with a horse that is an asset of a farm business is to enter it as Other property -> Other asset type and set the asset class to 7-year.
I've revised my answer after learning that asset class is not class life, but is derived from class life. Because the horse has a class life of 10 years, it is classified as 7-year property.
This is probably a glitch in the new program that will be resolved in the upcoming updates ... don't remember this ever being an issue in the past.
It appears that this bug has been present ever since the functionality to specifically ask about horses as farm-business assets was introduced with 2013 TurboTax. All versions of TurboTax from 2013 on have the same behavior with regard to this. Prior to 2013 TurboTax, one had to make the entry as Other and manually enter the asset class and recovery period.
Breeding or work horses more than 12 years old when placed in service are also handled incorrectly. These are 3-year assets with a 3-year recovery period, but TurboTax also incorrectly produces a 10-year recovery period for these.