Tips for a Successful Bull Season – Breeding Soundness Exams

Vet Tested. Kid Approved! Image via Jennifer Nielson from Fallon during 2015 Spring Bull Testing

Vet Tested. Kid Approved! Image via Jennifer Nielson from Fallon during 2015 Spring Bull Testing

By Dr. Megan Van Emon, Montana State Beef Cattle Extension Specialist

One of the most cost efficient methods of a successful breeding program is the breeding soundness exam (BSE) conducted on bulls.  Bulls are responsible for breeding 20 to 50 cows each breeding season while cows are responsible for one calf each year.  Having a BSE conducted on the bulls is crucial to a successful breeding program.

The BSE is an exam conducted by veterinarians that includes a physical exam, semen evaluation, and an internal and external exam of the reproductive tract.  Evaluating the feet, legs, teeth, eyes, flesh cover, and scrotal circumference and shape is included in the physical exam.  The semen evaluation includes semen normality and motility.  The BSE should be conducted 30 to 60 days prior to the beginning of breeding.  It is important to note that the bull’s sperm production cycle is approximately 60 days, and if illness, injury or other issue occurs, this could negatively impact the BSE and breeding capability of the bull and may need to be re-evaluated.  An additional BSE can be conducted at the end of the breeding season to determine if bull fertility decreased throughout the breeding season.

Body condition is crucial for bulls during the breeding season.  Having adequate flesh cover during the breeding season is needed to provide the extra energy required for breeding.  Body condition can be impacted by the number of cows the bull is expected to breed, the distance traveled to breed or eat, and nutrition during the breeding season.  A body condition score 6 or sufficient body condition that the ribs appear smooth across the bull’s side is the ideal flesh cover at the start of the breeding season.

Ensuring bulls are structurally sound in their feet and legs is needed to begin the breeding season.  Bulls with unsound feet and legs will have a difficult time walking and mounting for mating if a significant distance needs to be traveled for breeding.  General health of the bull is also needed to ensure bulls have adequate semen quality and the ability to mate.  Scrotal circumference is an essential measure because it is directly related to sperm production, sperm normality, and the onset of puberty.  The external and internal reproductive tract examinations ensure there is no inflammation, abscesses, warts, or penile deviations.

The semen evaluation includes the measurement of semen motility or the percentage of sperm cells moving in a forward direction.  The bulls needs to at least have 30% sperm motility to pass the BSE.  Sperm morphology, or the proper shape, is also determined and at least 70% of the sperm cells should have a normal shape.

If all of the minimum requirements are met, the bull will be classed as “satisfactory.”  However, if a bull does not pass one of the tests, they will be classed as “classification deferred.”  If a bull is classed as “classification deferred,” the bull should be tested again after 6 weeks.  If a mature bull fails the subsequent BSEs, they will be classified as “unsatisfactory.”  A young bull may be “classification deferred,” and pass the subsequent test.  Exercise caution when making bull culling decisions based on a single BSE.

Postpartum Interval and Fertility | Rancher Education

Rachel Endecott, Montana State University Extension Beef Cattle SpecialistBy Dr. Rachel Endecott, MSU Extension Beef Cattle Specialist

After calving, cows go through a period of temporary infertility known as postpartum anestrus. Cows will not experience estrous cycles during this time. Another common term associated with this phenomenon is postpartum interval, which is the time from calving to the subsequent conception. Postpartum interval plays an important role in determining a cow’s calving interval, or the number of days from calving date in one year to calving date the next year. To maintain a 365-day calving interval, a cow must have a postpartum interval of 80-85 days. If a shorter calving interval is desired to move the cow up in the calving cycle, she must have a postpartum interval of less than 80-85 days.

Several factors can influence the length of the postpartum anestrous period, including uterine involution, short cycling, suckling effects, and nutritional status. Uterine involution is the regression of the uterus—in both structure and function—to a status that is capable of carrying another pregnancy. This entails the uterus returning to a non-pregnant size, shape, and position, shedding all fetal membranes, and the repair of uterine tissues. This process is completed in approximately 20-40 days post-calving if no complications arise.

The first ovulation postpartum often occurs without visual signs of the cow being in heat, and is often followed by abnormal function of the corpus luteum (CL). Normal CL lifespan takes up 14-18 days of the typical 21-day estrous cycle of a beef cow. The short estrous cycles experienced by cows overcoming postpartum anestrus are characterized by a CL lifespan of 10 days or less. This is thought to be due to high levels of prostaglandin production and metabolism by the uterus during uterine involution. Prostaglandin is responsible for regression and death of the CL in a normal estrous cycle, but at the elevated levels described, that regression and death of the CL is premature. If fertilization of the egg from this ovulation were to occur, maternal recognition of pregnancy would fail as CL regression would take place too soon, and the embryo would be lost.

A nursing calf can be a factor in the length of time a cow takes to return to cyclicity. One might assume that the energy demand of lactation is the major issue at play in this case, but it is actually the suckling effect and presence of a calf. Suckling triggers a complex system of brain and hormone responses that result in lack of ovulation.  Frequency of suckling has shown to have a threshold influence on postpartum fertility. Suckling sessions of two or less per day promote return to cyclicity while sessions of greater than two per day tend to cause postpartum anestrus. It has been suggested that the maternal bond between the dam and calf plays an important role in this phenomenon as well. This may be due to the cow seeing, smelling, or hearing her calf or all of the above!

Plane of nutrition is an important part of cattle management throughout the production cycle. Pre-calving nutrition is probably more important than post-calving nutrition in impacting postpartum interval length. Cows with inadequate energy reserves typically have several follicular waves before a successful ovulation. Without ovulation, no CL forms and estrous cycles are not initiated. Due to the dramatic increases in nutrient requirements during late gestation and early lactation, intervention to improve cow condition during times of the year when nutrient requirements are lowest (post-weaning, for example) will result in the most efficient use of nutrients by the cow at a lower cost.

Many different factors interact to impact the postpartum anestrous period in beef cows. This post-calving period of temporary infertility can’t be avoided, but through an understanding of the systems at play, it can be managed to ensure reproductive success during the breeding season.

Reasons for Reproductive Failure in Cattle | 10 Things to Know

Let’s face it… Ranching is a business. To operate, a business must turn some kind of a profit. In the cattle business, reproduction is one of the most important economic traits. More important than growth, production, or carcass performance. If a cow fails to have a calf on the ground every year, something is missing.

Reproductive traits are some of the least heritable in the cow herd, meaning that we cannot rely on genetics along to improve program success. Fortunately, when there is failure in a breeding program, there are management tools we can utilize to build for success. Identifying the problems and opportunity for improvement are part of correcting the problem.

Top 10 Reasons for Reproductive Failure in Cows

She cycles like a ninja (silent heat)

Sperm and oocyte cannot meet (blocked oviducts)

Failure to launch (cystic follicle that will not ovulate)

Bad behavior (cortisol from stressed cow or bad handling)

She’s not feeling well (disease, manage that health and nutrition)

Exposure to environmental toxins

She’s too hot to handle (heat stress)

She has a mineral imbalance (pay attention to clinical and sub-clinical)

She lost her calf (embryonic or fetal loss)

She’s not eating her Wheaties (nutrition)

 Reasons Reproductive Failure Cows Bulls

Top 10 Reasons for Reproductive Failure in Bulls

Cows? What cows? (vision important to seeing estrus activity)

His penis looks strange and will not work (injury)

I’ve seen volcanoes cooler than this (heat stress, sperm quality, activity)

He’s not feeling well (disease, environmental toxins)

Scrotum looks a bit small (small testis – sperm factory)

The bull likes… Bulls? ( libido – requires observation to detect)

Shooting blanks (low sperm concentration, related to small testis or nutrition)

His sperm are weird shaped or have no tails (depleted reserves, poor morphology)

He needs a walker to get to the cows (foot and leg problems)

He carries a sign “Will breed for food” (under-fed and/or minerals)

This is just a short list of the issues we face when managing cattle and is adapted from a presentation by Dr. Neal Schrick at the University of Tennessee. More information about reproductive failure and how to manage those problems can be found from the Beef Reproduction Task Force.

What other issues when managing cattle reproductive problems do you encounter? Leave a comment below or email ryan@mtbeef.org. This is part of a month-long series of 10 Things to Know about Cattle. To read other posts in the series, click the image below.

Click this image to view all posts in the 30-day blogging series, 10 Things to Know About Cattle

Click this image to view all posts in the 30-day blogging series, 10 Things to Know About Cattle

Calculating Calving Distribution to Evaluate Reproductive Performance

Rachel Endecott, Montana State University Extension Beef Cattle SpecialistBy Dr. Rachel Endecott, MSU Extension, Beef Cattle Specialist

Calculating calving distribution is one way to evaluate the previous year’s reproductive performance for the cowherd. Calving distribution follows how cows are calving during the calving season, split into 21-day periods (the length of a cow’s estrous cycle). The starting date of the calving distribution can be determined in a couple different ways. The first is to add 283 days (average gestation length) to the breeding date or bull turnout date, and the second is to assign the starting date as the day when the third mature cow calves.

In herds where cow age can be identified along with calving date, calving distribution can be calculated for young cows separately from older cows, which may provide information about breed-up performance that might not otherwise be easily observed. Here is an example calving distribution from the Beef Improvement Federation Guidelines publication.

What is a good benchmark number for calving distribution? One example comes from the North Dakota Beef Cattle Improvement Association Cow Herd Appraisal Performance Software (CHAPS) program. The CHAPS benchmark for the first 21-day calving period is 63.4%. The benchmarks for 42 and 63 days are 88.8% and 95.6%, respectively.

table calving period evaluating calving performance

From this chart, do you see a group of cows you might be more concerned with compared to another? Perhaps the 3-year-olds? Check out a graph of this data for a more visual perspective.

Chart calving period for reproductive performance

In this format, the 3-year-old cows really jump out. All other age groups have the largest percentage of cows calving during the first 21 days, but the largest percentage of 3-year-olds calved during the second 21 days. Many beef cattle producers find that getting first-calf heifers to breed back well is a challenge. Some strategies to improve young cow reproductive performance include implementing proper heifer development and pre– and post-calving nutrition programs.

Some producers start the yearling breeding season 2-3 weeks ahead of the mature cows in an effort to give the heifers more time to recover before breeding season. On the other hand, some producers implement a shortened (say, 30-day) breeding season for yearling heifers in an effort to put selection pressure on reproduction. In this scenario, pregnancy rates will be lower than in a longer breeding season, so more potential replacement heifers may need to be kept back to ensure an appropriate replacement rate for the cowherd.

Keeping young cows separate from older cows before and after calving (if conditions allow) might also be a good young cow reproductive management strategy. Since young cows are still growing, their nutrient demands are higher than mature cows. Managing them separately allows for more targeted feeding to meet nutrient requirements. When managed together, feeding to meet mature cow requirements will result in a nutrient shortage for the young cows, while feeding to meet young cow requirements will result in overfeeding the mature cows, which could be a fairly expensive proposition.

Have you started planning for the 2014 breeding season? Or is it already well underway? An evaluation of calving distribution might give you some good insight on how last year’s management environment impacted cowherd reproductive performance.