The Cow-Calf Manager: Preparing for the Breeding Season, March 1998

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Often, it is hard to think about getting ready for the breeding season when we are swamped with all the activities of calving. However, there are only 80-90 days between the birth of the first calf and the start of breeding season. It's one of those important times that often is overlooked.

Nutrition. The first step in preparing for the breeding season is to keep the cowherd's nutritional program on target. Cows need 25% more energy and 41% more protein after calving than in late gestation. For most of the forages in VA that means energy should be the primary supplement with some protein supplementation as well. The only exception is new spring grazing which will meet the nutritional needs of the cow (as long as its plentiful). Cows that lose weight between calving and breeding are delayed in having their first heat and have lower first service conception rates (Table 1). It is important to feed early lactating cows the best forage you have available. A balanced mineral supplement is also critical as well as Vitamin A.

	% Pregnant

Weight Change - Calving to Breeding	From 1st service	After breeding 90 days	Cows not showing Heat, %

Losing weight	29	77	14

No change	57	95	0

Cows that calve in thin body condition will have lower conception rates and take longer to breed back than cows that calve in good body condition. It is important that thin cows gain weight from calving to breeding. Thin cows that gain weight during this period have a good chance of breeding back , but may breed late in the breeding season.

Vaccinations. Prebreeding vaccinations should be given 14 to 30 days before the start of the breeding season. For cows and mature bulls, a booster of Vibrio, Lepto, IBR/PI3, BRSV and BVD should be given. I usually advise a killed vaccine because some cows may not have calved when prebreeding vaccinations are given. However, you should check with your veterinarian on which vaccines and types are best for your region of Virginia.

Heifers and yearling bulls need two doses of these vaccines 21 to 30 days apart with the last dose given 14 to 30 days before the beginning of the breeding season. Heifers should have already been vaccinated for brucellosis.

Reproductive Examinations. Virgin heifers and all bulls should have a prebreeding reproductive exam. Heifers should have pelvic areas measured and palpated for reproductive tract scoring to identify heifers that should not be bred. Bulls need a breeding soundness exam to ensure a fertile bull is being placed with the cows.

Many ways and formulas have been printed for the use of pelvic areas. The best recommendation is to use pelvic areas as a culling tool not a selection tool. Heifers with pelvic areas less than 140-150 square centimeters at yearling or 150 -170 at breeding should be considered for culling. Culling on pelvic areas will eventually result in all heifers being above the minimum size. Selecting for large pelvic areas will lead to larger cows.

Reproductive tract scoring is a recent tool developed by researchers at Colorado State University. Many studies in several states have established that this is an excellent method for identifying heifers that are good candidates for breeding. The ovaries and uterus of the heifers is palpated much like in a pregnancy exam, except the development of the uterus and structures on the ovaries are noted. Heifers are given a score from 1 to 5 with 5 being a cycling heifer. Heifers that score a 4 or 5 are ready to breed and conception rates will be good. Heifers that score 3 will have a little lower conception rate. Heifers that score 1 or 2 should be considered for culling because they will either not breed or breed very late in the breeding season (Table 2).

Trait	1	2	3	4	5

	Reproductive Tract Score

Synch Estrus, %	46.3	76.6	80.4	90.7	89.4
Pregnant to Synch Estrus, %	2.6	22.6	39.5	54.6	55.0
Total Pregnant, %	28.2	74.2	76.2	94.1	85.0

From Odde et al., 1988

Breeding soundness exams for bulls involve a physical exam, a reproductive exam, semen evaluation and an estimate of libido. The physical exam consist of checking feet, legs and eyes for soundness. The reproductive exam checks both internal and external reproductive structures. The internal sex organs are palpated and checked to see if they are free of infection and defects. The penis and testicles are examined to see if they are normal and have not been injured. Scrotal circumference should measure at least 32 centimeters in yearling bulls and 36 centimeters or greater in mature bulls. The semen evaluation will look at % defects, % motility, and sperm concentration. An estimate of % normal sperm will be given and it should be above 70 %. Often the libido portion of the exam is not performed. Producers should observe bulls during the first few days of the breeding season to see if they are finding cows in heat and actually servicing them. Bulls that don't pass the breeding soundness exam or do their job should be replaced quickly.

Other Management Techniques. Bull exposure and temporary calf removal. Exposing heifers or cows to gomer (surgically infertile) bulls will reduce the interval from calving to first heat (postpartum interval). A great deal of research from Nebraska and Kansas shows this will reduce the postpartum interval by about 14 days. Fence line exposure will also work. I even knew a North Dakota rancher who positioned mud flaps on his bulls so they couldn't service cows. Surgically altered bulls are expensive to create and maintain especially for small herds. The other methods care a risk of cows getting bred to early. However, it is a management practice to consider.

Temporary calf removal (48 hours ) will increase the percentage of cows that are cycling. The removal to the suckling influence and presence of the calf is enough to "jump-start" some cows. It is especially helpful for 1st calf heifers or thin cows. It has been shown to increase the effectiveness of Syncro-mate-B. Research in Kentucky demonstrated no increased illness or decreased weaning weights of the temporarily weaned calves if they were given shelter, hay and water. It is labor intensive and takes good facilities. Care must be taken to ensure cows and calves "mother-up" after they are put back together. In most well nourished herd, it seems to be of little advantage.

Take stock of inventory. Prebreeding season is also the time to make that last minute check of artificial insemination supplies and semen. Make sure you order your supplies well in advance of breeding season as it is sometimes hard to get those items at the last minute. Make sure you have the vaccines you need on hand. Have I lined up the breeding soundness exam? Do I need another bull?

You should take stock of your herds genetic inventory as well. Are you using the right genetics for the industry? Are you giving up too much growth for calving ease? Would you be better to buy your replacements or breed your own? Is this the year for me to try A.I.?

So, between the mud and the chilled calves or while your waiting that extra 30 minutes to see if that heifer needs help or not, go through your pre-breeding check list and get ready for the next stage in the cow/calf yearly cycle.