A: The primary hormone of pregnancy for beef females is progesterone. Progesterone is produced by the corpus luteum that is on the ovary. Progesterone does not allow the cow to cycle. During mid to late gestation, there are hormones produced that come from the placenta. Some of those hormones are estrogen or estrogen like. So the answer to your question is yes, cows that are pregnant may have some riding activity caused by hormones that are estrogen-like that are being produced by the placenta.
What condition should my cows be in for breeding season?
Cows should be in an average body condition or a score of 3 (on a scale of 1 to 5) at calving time in order to maintain condition for the breeding season. Cows that are too thin will put all the nutrients into producing milk and maintaining their current condition. This will decrease their ability to rebreed, as cows that lose weight between calving and breeding are delayed in having their first heat and typically have lower conception rates. For example, a cow giving birth to a 75 lb calf will lose approximately 150 lb at calving, which includes the weight of the calf, placenta, and body fluids.
My cows are cycling, why are they not catching?
Just because cows are cycling doesn't mean they will always breed. Several research studies have shown that cows need to have 2 to 3 cycles after calving before they reach maximum fertility. Typically there is a 10-20% increase in first service conception rates between the first and third heat after calving. Also, to calve every 12 months, a cow must rebreed within 80 days after the birth of her calf; this level of performance makes it possible to reduce your cost per pound of weaned calf.
Can nutrition improve fertility?
Poor nutrition before calving can lengthen the interval from calving to first estrus and reduce the percentage of cows that cycle early in the breeding season. Poor nutrition after calving reduces overall pregnancy rates.
Cows need 25% more energy and 41% more protein after calving than in late gestation.
Do I need to vaccinate my cows and heifers before breeding season?
Replacement heifers should be immunized for respiratory diseases such as IBR and BVD. Typically yearling bulls and heifers will need two doses, 21 to 30 days apart, with the last dose given at least one month prior to breeding season.
For cows and mature bulls, boosters should be given for Vibrio, Lepto, IBR and BVD. Consult with a veterinarian on which vaccines and types are best for your operation.
How much bull power will I need?
Two-year-old bulls can be placed with 18 to 24 females and experience bulls should be able to breed 25 females (sometimes more if in smaller pastures). Yearling bulls (12 to 15 months old) can be placed with 10 to 15 females.
How do I evaluate the reproductiveness of my bulls?
It is important to have a veterinarian do a breeding soundness examination on all your bulls prior to breeding season. This allows enough time to find a replacement bull if needed. Give new bulls about a month prior to breeding season to adapt to their new environment.
Why should I breed my heifers ahead of the mature cows?
Two-year-old first calvers take longer to return to estrus after calving than mature cows. This allows time to watch and evaluate the bulls to ensure they know how to breed and/or that they are willing to breed. This is particularly important for young yearling bulls and older bulls. Breeding the heifers earlier allows for easier and closer management of the heifers at calving time, as they are most likely to need assistance at calving time.
Yearling replacement heifers should be bred about a month before the mature cows are bred. This allows for more time to recover and rebreed the following year.
What is the optimum length of the Breeding Season?
The length of the breeding season is an important factor in determining pregnancy rate. Late calving cows have lower weaning weights at weaning than early-calving cows. Reduced calving efficiency and long calving seasons typically results in poorer reproductive performance in beef cows. Shortening the breeding season from 150 days or even from 90 days to a 60 day season is an improvement.