McKenzie Ranch

08/07/2026

Finally came up with a way to display these signs

08/04/2026

In one commercial multi-sire ranch study, five of 27 natural-service herd bulls produced more than half the calves, while 10 bulls produced no progeny.

Putting several bulls in one breeding pasture does not mean each one contributes equally to the calf crop.

A Journal of Animal Science field study used DNA to examine paternity in a large commercial ranch setting.

Researchers collected blood or semen from 27 natural-service herd-sire candidates run together as one cohort, plus eight Angus and Hereford AI-sire candidates. A subset of cows had been artificially inseminated before exposure to the natural-service bulls. The researchers also sampled 625 yearling progeny.

The natural-service bulls ranged from 1 to 8 years old.

And every one of those herd bulls had passed a breeding soundness examination by a licensed veterinarian before the breeding season.

The DNA results still showed a huge difference in actual calf output.

Five of the 27 herd sires produced more than 50% of the calves.

At the other end:

10 natural-service bulls produced no progeny. Nine of those 10 were yearling bulls.

The study was conducted in one commercial herd, so those percentages are not a prediction for every multi-sire pasture. The paper also documented four paternal half-sib sire groups, calves for which the high-resolution panel found no qualifying sire, and substantial differences in parentage resolution between the high- and lower-exclusion-probability marker panels.

But the management lesson is hard to ignore: a bull can pass a breeding soundness exam and still contribute very differently from the bull standing beside him.

Without parentage data, a rancher may assume every bull is spreading genetics through the herd when the real sire distribution is far more uneven.

In your multi-sire pastures, do you know which bull is actually siring the calves?

07/20/2026

Adding a camera to the baler has been a game changer, not looking back over my shoulder all the time and can actually watch the net wrap go on

07/16/2026

Haying season is such a magical time of the year

07/03/2026

We spent the last two days getting all the bulls turned out

06/03/2026

Seman test day

05/30/2026

May always seems to fly by

05/25/2026

05/10/2026

Mother’s Day is here checking cows and checking for crocuses

04/24/2026

Half way through calving season and the rest of the crew waiting for me to get off the couch after dinner