Putting bull producers and veterinarians in a real conundrum.
The value of bull breeding soundness exams is well accepted and shown to have beneficial economic returns for the cow-calf producer. Bull breeders commonly have bull’s fertility evaluated prior to sale. This allows breeders to feel comfortable about selling sound bulls and buyers to believe they are receiving a bull that will perform well. Generally, the agreement is: these bulls all have had, and passed their fertility check. But what does that mean? Does it have the value it is perceived to have?
Yearling bulls are commonly sold at 12 -13 months of age. This may be prior to many of them reaching sexual maturity. It is also well known that as the bulls mature, a higher percent of bulls will produce satisfactory quality semen. At 12 months of age there is approximately 45%, at 14 months 75% and by 16 months of age most bulls will have satisfactory semen quality. (Barth, 2013, pp. 108 – 110) Sexual development occurs over several months. As bulls become more mature the percent of morphologically normal sperm will also increase.
While nutrition does have important effects on the onset of puberty and maturity to a satisfactory test, age appears to play a more significant roll with nutrition having only small to no significant effect. Nutrition is more important prior to weaning than it is after when striving to improve reproductive performance at an early age.
It is very likely that veterinarians and cattle producers have been conditioned to accept or believe that testing young bulls using sub-optimal equipment or techniques has no negative economic impact. The norm is to test young bulls less than 14 months of age and sell well over 90% as “fertility tested” and “passed” bulls. Historically, many veterinarians have not performed a complete semen evaluation and/or used poor procedures, inadequate equipment, and they receive little to no formal training. This has led to inconsistent results between veterinarians performing breeding soundness examinations. (Hopper, 2015) (Barth, 2013) It is not uncommon for veterinarians to feel pressured and loose business when “failure” rates are too high for the expectations of the bull producer. This can lead to strained veterinary-client relationships and does not encourage the veterinarian to take the time and expenses needed to obtain the best equipment, become better educated, and take the time to do a better job. (Robert S. Youngquist, 2007) The bull producer understandably wants to sell as many bulls as possible. They are usually also concerned about the reproductive ability of the bulls they sell but believe that well over 90% of their bulls are or will produce satisfactory semen. They seldom have any complaints from the bull buyer that the bulls they sold do not perform up to expectations. The losses occurring due to sub-fertility easily go unnoticed. Sub-fertile bulls are bulls who’s performance does not meet expectations, usually fewer cows pregnant during any one estrus cycle. This leads to fewer early calves and in many cases few pregnancies at the end of the breeding season.
See past blog:
Who Pays the Piper -The hidden cost of Sub-fertile Bulls
Reproductive efficiency is considered the most important economic trait for a cow-calf producer. This means that not only is there a high pregnancy rate, but also a high number of calves born in the first 21 days of the calving season. Over 50% of the calves should be born before day 17. Calves born early in the calving season are more valuable than those born later due to total weight of beef sold. (Howard, 1993) It would be very difficult to evaluate the exact cost of sub-fertile bulls to a cow-calf producer. But is costs a minimum of 41 pounds for every missed pregnancy during any one cycle. The purpose of a bull breeding soundness exam is to set a high standard for bulls and cull both infertile and sub–fertile bulls. When sub-fertile bulls are used in a herd the most common effect is more cows calving later in the calving season. If only 120 days (30 cows averaging a loss of 4 days = 120 days) was lost due to a sub-fertile bull and assuming 1.75lbs / day at a cost of $1.60 / lbs. will cost the producer $336 just for the first year. This number is then compounded where most of these cattle will continue to be late calving the following years. Assuming only half that cost for the next year and utilizing that bull for 5 years the cost exceeds $2520 and this cost is most likely very conservative depending on the extent of sub-fertility of the bull. It is unlikely cow-calf producers would be able to understand or recognize the losses seen from mildly sub-fertile bulls. Most losses from sub-fertile bulls are much greater.
Table showing the effects of bull sub-fertility
The value or purpose of performing a complete breeding soundness evaluation prior to 14 months of age should be seriously questioned. Many bulls at 12 months of age have not completed maturity and results can be as low as 33 – 45% of bulls with a high enough percent of morphologically normal spermatozoa to be considered satisfactory. At 14 months 60 – 75 % may be able to achieve that goal. An advantage of selecting bulls that early age is to select bulls for early maturity which can have positive economic advantage for a cattle herd. (Barth, 2013) However, we should not expect well over 80% to “pass” at this early age. Through the use of genetic selection we should expect the number of bulls to reach an earlier maturation to increase.
Many studies addressing yearling bull fertility continue to show the same conclusions.
(Spitzer, 2000)
Referring to the table above, Kastelic et al. stated: “Numerous studies of performance station bulls indicate drastic differences in semen quality according to age (Table 1); a few months can make a tremendous difference. Although most producers are unwilling to accept that less than 50% of their bulls will be judged satisfactory, if standards are rigorously applied, many young bulls will not meet the minimum standards, typically due to inadequate semen quality.” (Kastelic, 2012)
The ability of bull producers to accept this difficult conclusion is continually hampered due to normal human psychology. Scientific results are commonly dismissed when they challenge our world view. (Smith, 2016) It is much easier to believe that every bull sold or purchased is fertility sound. It is difficult to accept that mildly sub-fertile bulls are having a negative impact on the unsuspecting buyer. Having to deal with the fact that it is possible to have somewhere around 40 to 50% of bulls less than 14 months may not have satisfactory semen is painful. There is no question that many of these bulls will continue to mature, spring and summer are just around the corner, and the combination of both age and season will improve the outcome. The dilemma comes when faced with the fact that not all these bulls will become reproductively sound at standards to achieve optimal reproductive efficiency. How do we identify these bulls? How do we deal with the added expenses incurred due to the normal physiological maturation of bulls who just are not quite there yet and cull out the ones who never will be?
This responsibility should not fall on only one party such as the bull producer. Every individual from veterinary associations, individual veterinarians, bull producers, and the buyers need to share in the responsibilities. First and foremost is we all need to become educated. We need to apply rigorous standards to bull breeding soundness evaluations. We need to realize that a lower number of bulls than we would desire, likely are not going to meet these standards. We then need to use this as an opportunity to apply genetic pressure towards improved reproductive performance. With this information we can then do what is needed to help the cow-calf producer achieve a higher reproductive performance and reward bull producers for the work and expenses they put in to create a great product to achieve these goals. Currently, bull buyers need to retest every bull purchased regardless of the test results prior to purchase. A semen sample could be collected and sent to a certified lab for morphological analysis. This will help elevate the potential conflict of interest currently occurring when bull sellers hire veterinarians to test their bulls. Both parties should be actively protecting their interest. Bulls tested prior to sell that do not meet the minimum requirements should be designated as “differed pending full sexual maturity”.
Summary:
Today, we cannot expect a high percent (90+ %) of young bulls less than 14 months of age to be sexually mature enough to be classified as satisfactory potential breeders. Veterinarians need to use high quality equipment and technique to set a high standard in evaluation of semen. The use of accredited sperm morphologists could help to minimize the variation and subjectivity seen between veterinarians and eliminate the pressure put on veterinarians by bull producers to classify bulls as satisfactory. One option would be that bulls not sexually mature would not be excluded from sell but be designated as “currently sexually immature”. Bull buyers have the responsibility to test all purchased bulls prior to use and when sexually mature. Any tests where a satisfactory designation is not possible should be retested at least one time with in a few days of the first test as long as the bull is 16 – 18 moths old. When both tests fail to produce quality semen the bull seller and buyer should follow a pre-arranged agreement for fair trade. Waiting to sell bulls until the middle of April would lessen the difficulty surround early bull sales and sexually immature bulls.
References
Barth, A. D. (2013). Bull Breeding Soundness (Third ed.). Saskatoon, Saskatchewan, Canada: Western Canadian Association of Bovine Practitioners.
Hopper, R. M. (2015). Bovine Reproduction. Hoboken: Wiley Blackwell.
Howard, J. L. (1993). Current Veterinary Therapy 3 Food Animal Practice. Philadelphia: W.B. Saunders.
Kastelic, J. P. (2012). Bull BSE and semen analysis for predicting bull fertility. Society for Theriogenology 2012 (pp. 277 – 287). Reprinted in the IVIS website with the permission of the Society for Theriogenology.
Robert S. Youngquist, W. R. (2007). Large Animal Theriogenology. St Louis: Saunders.
Smith, A. C. (2016, March 28). 5 Reasons Why People Stick to Their Beliefs, No Matter What. Retrieved from Pyscology Today: https://www.psychologytoday.com/us/blog/true-believers/201603/5-reasons-why-people-stick-their-beliefs-no-matter-what
Spitzer, J. C. (2000, October 16). Bull Breeding Soundness Evaluation: Current Status. Retrieved from International Veterinary Information Service, Ithaca NY : http://www.ivis.org/advances/Repro_Chenoweth/spitzer/chapter.asp?LA=1