Beef breeding season management

Introduction

In analyzing the cow-calf industry, the four factors that are more commonly used by producers as influencing profit are:

1. weaning weight of the calves
2. percent of cows weaning calves
3. annual cost of maintaining the cow
4. the price received for the calves

In evaluating research on cow efficiency, it is apparent that one of the more important factors influencing the overall productivity and efficiency of the beef cow herd is reproductive efficiency.

Reproductive Rate

Table 1. Miles City Study (Montana 14 yr).

If the percent calf crop is to be improved, the number of cows becoming pregnant must be increased and the losses near or shortly, after birth decreased.

Why Cows Do Not Become Pregnant

Much research has been done indicating that many cows fail to show heat early in the breeding season and also that conception rate at first service is low. If, however, proper management procedures are utilized the number of cows showing estrus the first 21 days of breeding as well as the conception rate at first service can be high.

Factors affecting the number of cows showing heat early in the breeding season and the number conceiving on first service are:

• Showing Heat First 21 Days of Breeding
  1. Time of Calving
  2. Body condition of cows at calving time
  3. Age of the cow
  4. Suckling
• Conception Rate at First Service
  1. Time of Calving
  2. Weight changes of cow near breeding time
  3. Bull fertility
  4. Bull to cow ratio

Time of Calving

Cows calving late in the calving season generally have a lower pregnancy rate because they do not have time to show estrus early in the breeding season.

Cows require adequate nutrition and rest post calving in order to cycle normally. Conception rate is higher in cows bred 60 days or more after calving.

Body Condition

Body condition is important in determining when a cow shows estrus following calving. Ninety-one percent of the cows in good body condition at calving had shown estrus by 60 days post-calving, as compared with 61 % of the cows in moderate condition and 46% of the cows in thin body condition.

Table 2. Body Condition at Calving and Heat after Calving

Ref: Wiltbank

Suckling

Cows that are suckled have longer intervals from calving to first estrus. Flushing and 48-hour calf removal can be helpful in improving reproductive performance. Neither practice alone is as beneficial as a combination of the two.

Removing calves for 48 hours can be a problem in some situations. The best way to accomplish this is to combine calf removal with working the calves. Calves must not nurse for 48 hours to get maximum results.

Weight Changes

Weight changes near breeding time affect pregnancy rate. Sixty-seven percent of the cows that held their weight from calving to breeding conceived on first service as compared with 43% in cows losing weight during this period. The pregnancy rate after 21 and 90 days of breeding was also higher in cows holding their weight as compared with cows losing weight.

Body Condition Scoring

As has been discussed, body condition of the cow at calving (moderate or good) and post calving to breeding will have a direct bearing on improved breeding efficiency.

Most scoring systems have been based on palpation of the back and hindquarters of the cow. Particular attention is given to the chine, loin. rump, tail head. hook bone and pin bone regions. Cows in one system are scored on a scale of 1 to 5. A score of 1 indicates severe under conditioning while a score of 5 is assigned to over conditioned obese cows.

Scoring System

• Score 1. Individual spinous processes have limited flesh cover; the ends are sharp to touch; they give a definite overhanging shelf effect to the loin region.
• Score 2. Transverse processes can be felt, but not prominent; rounded with some fat cover.
• Score 3. Transverse processes can be felt with firm pressure; processes appear smooth; the overhanging shelf effect is not noticeable.
• Score 4. Individual processes only felt with very firm pressure; rounded with no overhanging shelf effect; loin and rump appear flat; tail head and pins are rounded.
• Score 5. The structure of the transverse processes, hook and pin bone region is not apparent; fat deposition is obvious and prominent.

Ref: E.E. Wildman

Image

Figure 1. Body Condition Scores vs. Calving Interval (days).

It may not be necessary or practical to palpate all cows under most circumstances but an understanding of the scoring system and what is involved would allow eye-balling or visual appraisal of cows to evaluate condition.

Cows should be in moderate to good body condition at calving time to attain optimum reproductive performance.

Possible Scoring Use

1. Observe cows one or two months before calves are scheduled to be weaned. If cows are thin, supplement feed or wean calves.
2. Sort cows by body condition at weaning time - feed accordingly.
3. Prior to calving.
4. Middle of calving season (prior to breeding)

Suitable adjustments must be made to the feeding program to meet the target score if cows are indeed too thin.

The Bull

Condition and nutrition of the bull prior to breeding are equally important to breeding efficiency.

Unfortunately very few bulls undergo any thorough breeding soundness examinations prior to the breeding season.

A breeding soundness examination would involve:

1. Conformation
2. Physical Examination
   • scrotum and testicles
   • scrotal circumference
   • penis and prepuce
3. Semen Evaluation
   • volume
   • concentration
   • mortality and morphology

Scrotal Circumference

Research has documented that testicular and scrotal development is directly related to sperm production and fertility in bulls. Scrotal circumference measurement properly done provides an aid in selecting sires with normal testicular development and is of considerable importance, particularly in yearling bulls.

Factors Affecting Bull Reproductive Potential

1. Testicular and scrotal development.
2. Ability to physically breed females.
3. Semen quality and volume.
4. Libido or serving capacity.

All four are of equal importance and testing would be a recommended procedure where practical before a bull is used.

Table 3. Scrotal Circumference in Centimetres.*

*The average scrotal circumference will vary according to breed.

Bull to Cow Ratio

Table 4. Number of Cows per Bull.

These figures vary considerably with the condition of the pasture, the sex drive of the bull, the fertility level of the cow herd and the length of the breeding season.

Example Breeding Program (Tom O'Connor)

The O'Connor program involves five factors:

1. Sixty-day breeding.
2. Cows in moderate or good condition at calving time.
3. Cows gain in weight for three weeks before the start of breeding season and during breeding season.
4. Calves removed from cows for 48 hours at start of breeding season.*
5. Cows bred to fertile bulls.

* This factor may not be practical to the majority of commercial producers.

Eighty percent of the cows were pregnant after 30 days of breeding in the O'Connor herd that utilized these five factors. After 42 days of breeding, 87% were pregnant.

Length of Breeding Season

The length of the breeding season is an important factor in determining pregnancy rate. It has been shown that late-calving cows have smaller calf crops than do early calving cows. The only reliable method for making sure cows calve early in the calving season is to have a short breeding season.

A 60-90 day breeding season should be a goal of most cow-calf producers with 45 to 60 days being more desirable. This could be achieved by gradually reducing the breeding season each year by 2-3 weeks which would result in fewer open cows being culled within a given year. Adequate nutrition and management are essential to success.

Table 5. Effect of Shortening the Calving Season.

*Of cows calved. Ref: Spitzer

Advantages of a Shortened Breeding Season

1. More concentrated management (time and labor).
2. More uniform group of calves by age, size and weight to sell at weaning.
3. More uniform group of calves by age, size and weight to feed as a management group if calves are kept and fed.
4. Early calving cows usually wean heavier calves.
5. Nutrient requirements of the cow herd will be much easier to meet during the critical stages of the production cycle with all cows calving within a shorter period.
6. Eliminate cattle with low fertility from the breeding herd.

With shorter breeding seasons success will be dependent on feeding and breeding management. Adequate nutrition and rest are essentials to fertile and cycling cows. Equally important is the health, condition and fertility of the bull if natural service is used. During the breeding season it is important that the herd be checked routinely to observe breeding progress.

Breeding Replacement Heifers

When considering a shortened breeding season, heifer management at breeding will be of importance. Yearling replacement heifers should be bred 3 weeks prior to the breeding of the mature cow herd. Heifers will require a longer period of time to begin cycling and show heat after calving than mature females. Heifers bred before the main cow herd, will calve earlier in the season and will be cycling normally by the time the main cow herd is being bred the following year. If we want a heifer to be a good lifetime producer she must calve early. She must show heat and conceive early in the breeding season. Heifers calving late usually become late calving cows.

The lifetime production of beef females can be increased by calving at two years of age. This can be achieved by producers willing to provide the required nutrition and management.

Table 6. Reproductive Performance in Hereford Heifers as Influenced by Weight at Start of Breeding (Tom O'Connor).

Artificial Insemination (AI)

Those considering or using AI should ensure that the breeding season does not become lengthened in attempts to settle cows. Top breeding management is required for successful heat detection and high conception rates with AI.

A suggested practice would be to breed the top end of the herd AI the first 25-30 days of the breeding season and use a clean-up bull or bulls for the remainder of the breeding period.

A sound health program and good nutrition are requirements of any breeding program. They become even more important in an AI program.

Proper handling facilities are essential to an AI program. They can be very simple or elaborate. Anything that can be done to reduce handling stress will greatly increase conception rates.

Success with artificial insemination requires top management. Management must be willing to provide the additional labor which will always be above the requirements for natural mating.

Heat Detection

Individual cow identification visible from a distance and adequate records are essential components of a successful heat detection program.

Table 7. Heat Detection.

A higher detection rate of cows in heat has been observed before noon than during the afternoon and evening. Shortly after sunrise a special effort should be made to detect heat.

Heat Detection Aids

1. Kamar Patch - pressure sensitive devices glued to the rump of cows for heat detection.
2. Sterilized Bulls - surgically altered bulls.
3. Teaser Bulls
4. Hopped up Heifers - heifers treated with hormones.
5. Chin Ball Marker - detector animal fitted with this marker.

Insemination Methods

Cleanliness during all insemination procedures is essential and is a critical point for success or failure.

Estrus Synchronization

Injection of a natural or synthetic prostaglandin will induce heat in sexually mature and cycling females. Cattle which are not reproductively cycling must not be included in an estrus synchronizing program.

Estrus synchronization with prostaglandins has the potential to improve and increase artificial insemination (AI) programs with cattle.

Controlled breeding programs will reduce time and labor involved with heat detection and shorten both the breeding season and calving season. Total Cost factors would have to be considered.

With good management this program can be successful.

Pregnancy Examination

Pregnancy examination as a routine practice at the end of the breeding season can be an important tool in improving the efficiency within the beef cow herd. Identifying open cows which can be effectively marketed will reduce wintering costs and increase efficiency of production.

Pregnancy examination should take place 6 to 8 weeks after the end of breeding season.

Advantages of early pregnancy diagnosis in beef cattle are:

1. Gives warning of breeding problems (infertility and problem breeders)
2. Improved fertility - effective culling and marketing of problem breeders.
3. Reduced overhead costs - effective use of time, labor, facilities, etc.
4. Guarantee pregnancy in females for sale.

Monitoring Reproductive Efficiency

Records are essential to identify where losses occur in the reproductive cycle. This summary (Table 8) will permit calculation of reproductive performance indices that will enable you and your veterinarian to make breeding management decisions.

Records are essential to identify where losses occur in the reproductive cycle. The following summary will permit calculation of reproductive performance indices that will enable you and your veterinarian to make breeding management decisions.

Table 8. Monitoring Reproductive Efficiency.

Summary for Improved Reproductive Efficiency

1. Body condition score
2. Nutrition - bulls and cows
3. Breeding soundness examinations
4. Bull to cow ratio
5. Breed heifers - target age 14-15 months - 3 weeks before cows.
6. Breeding season 45-60 days
7. Calving season 45-60 days
8. Pregnancy Examination
9. Cull open or barren cows
10. Monitor performance.

A highly managed cow herd will be much more efficient and productive. Discuss your reproductive program with your local veterinarian, and/or AI company.

References

1. Beef Cow Efficiency Forum '84 L. Corah
2. Cattlemen's Library
3. Veterinary Clinics of North America. J.N. Wiltbank