Support Your Bulls This Mating Season

As mating season approaches, there is often a large amount of focus on ensuring the heifers / cows are in good condition and cycling, and the bulls are often forgotten. However, failure to manage the bulls can easily result in a disappointing mating season. It is estimated that up to 10% of yearling bulls in a beef system are either sterile or sub-fertile, whilst 4% of proven sires can develop fertility problems between breeding seasons1. Some of these performance issues can be caused by poor nutritional management, and therefore understanding what nutritional support bulls require is essential; If sub-par bulls are used it can lead to financial impacts and herd management issues next season, in both dairy and beef systems.

Protein and Energy

Protein and energy play key roles in the reproductive performance of bulls, both during their pre-pubertal development, and their seasonal performance long term. 

Yearling Bulls

For young bulls, puberty is onset by body weight in relation to age, rather than by age itself2,3. And liveweight gain is directly related to dietary energy and protein intake. Therefore, providing sufficient protein and energy daily is key to aiding young bulls to reach puberty faster2,3. It also influences their reproductive hormone production, testicular development (scrotal circumference and testicle mass), and sperm production (volume and quality)3. Feeding bulls below their maintenance requirements can result in reduced scrotal circumference, less testicular mass, and a lower sperm count5. 

Mature Bulls

The energy and protein content of the diet remains important for bulls post-puberty also 2,3.
Bulls deficient in dietary protein and energy typically produce a smaller volume of semen, with a lower live sperm count per ejaculation. This is because protein plays a significant role in the production of the reproductive hormones which influence semen and sperm production2,3. They can also have a lower libido, which is thought to be energy related, due to less physical strength2. 

Trace Elements

There are several trace elements that are key to a bull’s reproductive performance. 
Iodine, manganese, cobalt and selenium are all important for the production and protection of semen and sperm, due to their roles in hormone regulation, and their anti-oxidative properties4,5. However, it is copper and zinc that are the main focus, due to their ability to significantly influence semen quality and quantity. 
Both zinc and copper play crucial roles in the regulation and production of reproductive hormones such as testosterone, luteinising hormone, and more. This means they have a strong influence on semen quantity and quality, and libido. It has been found that bulls supplemented extra copper and zinc have improved semen quality and quantity5. Meanwhile a deficiency in zinc and copper has been found to have damaged testicular tissue, impacted semen quality and quantity and reduced libido4. This, combined with the fact that a bulls ability to retain copper is reduced during hot humid weather4, making copper supplementation even more important in New Zealand dairy and beef systems due to the timing of mating.   

Forage Max Block

SealesWinslows Forage Max block is the idea tool to support your bulls this mating season.
This 22.5kg dehydrated molasses block ticks all the boxes: protein, energy, and trace elements. The dehydrated nature of this blocks, combined with the addition of soyabean oil, supplies 12MJME/kgDM in the form of readily available sugars and fat. The block also contains soyabean meal, providing 12% crude protein/kgDM. Lastly, the block contains macro minerals, vitamins, and trace elements, all formulated to complement typical New Zealand pastures, and support the trace element requirements of breeding bulls6.
For more information on how forage blocks may benefit your bulls, speak with your local TSR.

References
1. Beef + Lamb New Zealand. (2017). Managing beef cows prior to, and during mating.
2. Brown, B. (1993). A review of nutritional influences on reproduction in boars, bulls and rams. . Reprod Nutr Dev.
3. Singh, A., Kumar, P., Singh, A. K., Kerketta, S., Rk, Y., Rajak, S. K., & Yogi, R. K. (2018). Nutrition and bull fertility: A review. Journal of Entomology and Zoology Studies, 6(6), 635–643. https://www.researchgate.net/publication/329177644
4. Pal, R. P., Mani, V., Mir, S. H., & Singh, R. K. (2017). Importance of Trace Minerals in the Ratio of Breeding Bull-A Review Trace element research View project Feed additives for better productivity of ruminants View project. Article in International Journal of Current Microbiology and Applied Sciences. https://doi.org/10.20546/ijcmas.2017.611.026
5. Majumder, A., Thakur, M., Bhakat, M., Saha, M., Mohanty, K., & Mondal, G. (2020). Effect of Dietary Copper and Zinc Supplementation on Semen Quality of Murrah Bulls. RESEARCH ARTICLE Indian Journal of Animal Research, 54, 1260–1264. https://doi.org/10.18805/ijar.B-3887
6. National Research Council. (2000). Nutrient Requirements of Beef Cattle. In Nutrient Requirements of Beef Cattle. National Academies Press. https://doi.org/10.17226/9791