While genomic selection allows for more rapid genetic improvement, it also appears to be accelerating the level of inbreeding in Holsteins.
Some dairy geneticists had predicted this would occur. But others felt with genomics information available, A.I. bull studs would select only one bull from a flush of calves from a top sire and highly-pedigreed dam, and thereby reduce at least the slope of the inbreeding curve. (In the past, a number of bull studs might each take a bull from a specific flush because they only had pedigree information and had no idea which calf had inherited the best level of genetics.)
The current level of inbreeding in Holsteins calves born in 2019 is 8%, according to AgSource data. Eight percent is still considered to be a moderate level of inbreeding. “Inbreeding levels less than 3.15% is considered low while inbreeding levels over 12.5% are considered high,” explains Nicole Nehls, with AgSource Cooperative.
But averages don’t tell the whole story. “There has been a significant shift in distribution in only seven years,” she says. “The majority (76%) of Holstein cows born in 2011 fell in the low to moderate category of 3.15 to 6.25% inbred. However, Holstein calves born in 2018 now fall in the moderate to high category (82%), which is 6.25 to 12.5%.
“Avoiding inbreeding will become harder as selection of top cows and bulls in the Holstein population are made,” she says.
But there are things you can do to minimize the increase in inbreeding in your herd. The first is keeping good animal identification records. The second is consider using mating programs that are designed to minimize inbreeding. “More complex [mating program] versions can take actual genomic results and look at potential genes in common between sire and dam,” she explains.
Sidebar: It all starts with identification!
Source: AgSource
Animal identification is the first step in ensuring good, reliable data. Several steps should be followed to ensure the genetic information you receive from the Council on Dairy Cattle Breeding (CDCB) is accurate.
Step 1) The animal must be identified with a unique, official national animal ID. Animals with a herd management number will not qualify to receive a genetic evaluation.
Step 2) If you tag your animal, make sure to provide the official ID to your technician, or enter the complete official ID number in your herd management software as soon as possible.
Step 3) Enter the complete breeding information. For example, entering a partial NAAB code on a bull, or a bull’s short name, will result in a calf with a sire unknown. Also make sure to enter the correct stud code for conventional versus sorted semen.
Step 4) Ensure the cow’s official ID is transferred to her calf’s official Dam ID. If the official ID of the cow is not transferred to the calf record, it will result in a break in the animal’s pedigree – causing missing inbreeding and incomplete genetic information.
Step 5) If you genotype calves, it is key you enter the same official ID used to receive genomic results in your records and herd management program. If the official ID numbers are different, there is little possibility the animal’s genetic information will be updated and she will receive two different genetic evaluations.
For more on animal identification and inbreeding, go to: https://dairy.agsource.com/2019/07/18/genetics/?dm_i=5A8K,20ZB,13VMNU,6DAC,1
