Breeding Season - Frequently Asked Questions

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 What condition should my cows be in for breeding season?
Cows should be at a body condition score of 3 (on a scale of 1 to 5) after calving, and replacement heifers at 3.5. This is considered moderate body condition. Thin cows at calving tend to take longer to return to normal cycling, and thus a 10 to 20 percent lower conception rate than cows that are in moderate condition. Most of the nutrients a cow consumes go into maintenance and producing milk for her calf; weight gain is the last priority when all other bodily requirements are met. This is why it is usually difficult for lactating cows gain weight in the first few months after calving.

My cows are cycling, why are they not catching?
There are several reasons why cows are not catching even though they are apparently cycling. The breeding season should begin 2 or 3 months after first calving date, and not immediately after. This is to allow the cow's bodies to get back into normal estrus activity. Their reproductive hormones right after calving are not cycling normally like they would when they are not pregnant, plus the uterus needs time to shrink back to normal size. The first few estrous cycles are usually irregular in timing, and this is normal.

Other reasons cows are not catching is that there may be females with cystic ovaries in the herd. Cystic ovaries tend to allow cows to be in heat all the time, but no matter how long they are with a bull they do not catch. Cystic ovaries are often associated with over-conditioned cows.

Bulls may also need to be checked. If there is more than one bull in a corral with several females and these bulls are almost identical in size, regardless how many females are coming in heat, fighting is likely to occur. A bull may be suffering from an injury or malady that is affecting his ability to breed, from lameness to a broken penis. He may even turn out to be less fertile with poor sperm motility or abnormal sperm structure than first thought. A breeding soundness exam done by a veterinarian can rule most out these problems.

Can nutrition improve fertility?
Nutrition can either improve or ruin fertility in cattle. Cows receiving poor nutrition tend to take longer to reach their first heat period after calving, and are less likely to successfully conceive on time in the breeding season. Pregnancy rates suffer as a result, as does the subsequent calf crop.

Cows generally need more energy and protein during lactation than they do during pregnancy. The rule of thumb for cows is 7 percent protein in mid-pregnancy, 9 percent protein in late pregnancy, and 11 percent protein in lactation or post-calving. Energy requirements increase in a similar manner.

Bulls also need to have good nutrition to be able to successfully breed and produce a calf-crop. Since a bull is worth half of the entire cowherd, and they tend to pay more attention to females in the breeding season than to feed, it is very important that he is on a good nutritional program before and after the breeding season. After the breeding season he will have lost some condition, and will need to be on a good nutritional program so that he can build up that weight and maintain it in preparation for next season.

Should my cows, heifers, and bulls be vaccinated before breeding season? What should I vaccinate for?
Replacement heifers and cows will need to be immunized for Clostridial bacteria (8-way vaccine like Covexin Plus), BVD (Bovine Viral Diarrhea) types I and II, IBR (Infectious Bovine Rhinotracheitis), PI3 (Parainfluenza-3), BRSV (Bovine Respiratory Syncytial Virus), H. somnus bacteria, and a scour vaccine that protects against E. coli, corona virus and rotavirus. Vaccinations for leptospirosis and vibriosis may be needed, but not usually in Alberta. Talk to your bovine veterinarian to see what other diseases your breeding herd will need to be protected from.

Timing of vaccinations is very important. Cows and heifers should be vaccinated 8 to 10 weeks before calving for maximum immunity. Animals that have not been vaccinated previously need two shots: The first 3 or 4 months after breeding, and a booster 8 to 10 weeks before calving. The two injections need to be done at least 3 to 4 weeks apart.

Bulls will require the same vaccine protocol as the cowherd. Talk to your veterinarian about also vaccinating bulls for virbriosis and trichomoniasis.

How much bull power will I need for my herd?
Generally, one bull can service 20 cows in a breeding season. However, yearling bulls (10 to 15 months of age) will only be able to breed 10 to 15 females. Older and more experienced bulls (24 to 30 months of age or more) can run with 25 to 30 cows during the breeding season. A bull will breed less cows and heifers if in a large pasture over 10 or 20 acres because of the time needed to travel from servicing one female to go chase another. However, larger spaces may reduce rivalry incidences of similar-aged bulls that are of the same age and size as the other.

How do I evaluate the reproductiveness of my bulls?
Your bovine veterinarian will perform a bull breeding soundness exam on all your bulls, provided it is done 4 to 6 weeks before the breeding season. A BBSE will give you an evaluation of semen quality, sperm motility and structural composition, sperm count, body condition score, condition of the bull's reproductive organs, and measurement of scrotal circumference. A veterinarian can determine if a bull is ready for breeding or needs to be culled. When BBSEs are done on your bull battery at least a month before the start of breeding season, you have enough time to sell off the culls, and look for new bulls for your herd.

Why do I need to breed my heifers ahead of my mature cows, and how old should they be when bred?
Replacement heifers will need to be bred 21 to 30 days ahead of the main cowherd because they require a longer period of time to return to normal cycling activity and display heat after calving than mature cows. When heifers are bred before the main cowherd they will calve earlier in the season; this gives you a chance to watch your heifers for potential calving problems. First-calf heifers, after calving, should be cycling normally by the time the main cowherd is going into the breeding season the following year. At that time they will be bred at the same time as the rest of the mature cows.

The breeding season for heifers should be around 45 to 60 days long. Heifers should also be 65 to 70 percent of their potential mature weight by the time they are around 15 months of age.

What is the optimum length of the breeding season?
Ideally, the breeding season should be 45 to 60 days long, with at least 70 percent of the cowherd conceived within the first two weeks. Longer breeding seasons usually mean a longer calving season; and a longer breeding season gives less chance for late-coming calves from late-calving cows to reach target weight upon weaning time. Late-calving females tend to have lower weaning weights than early-calving cows; late-calving cows are more prone to wean younger, smaller calves than those cows that calved early in the calving season. Longer breeding seasons tend to hide those cows that have poorer reproductive performance, reducing their chances of being culled. Shortening the breeding season from 150 days down to 90 days over a couple years will reveal those females with poorer fertility, and enable you to tighten up and shorten the calving season considerably while improving pregnancy and conception rates, and give a more uniform calf-crop with improved weaning weights.

Prepared by Ag-Info Centre, Alberta Agriculture & Forestry 310-3276
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For more information about the content of this document, contact Barry Yaremcio.
This document is maintained by Brenda McLellan.
This information published to the web on April 6, 2004.
Last Reviewed/Revised on January 9, 2019.