Breeding Tips for the Monjiro Lineage by Kenichi Ono
Table of Contents
* Note: This is not a direct translation of Kenichi Ono’s “Top 100 Famous Beef of Japan [Revised Edition]” but a summary that was written using it as a direct source.
Figure 1. Monjiro
Breeding Tips for Monjiro
Monjiro, the influential sire of Michifuku and Haruki II, and grandsire of Sanjirou and Shigeshigetani, is a cornerstone of Wagyu genetics both in Japan and internationally. His genetic legacy, particularly through his descendants, has been integral to establishing high-quality Wagyu herds worldwide. Breeding with Monjiro’s bloodline offers unique opportunities to optimize meat quality, marbling, and overall carcass traits, but also requires careful consideration to balance strengths and address weaknesses.
Here are some breeding tips for maximizing the genetic potential of Monjiro’s line:
1. Focus on Enhancing Marbling and Carcass Traits
Monjiro’s line, particularly through his sons Michifuku and Haruki II, is renowned for exceptional marbling and superior carcass quality. These traits carry through to Sanjirou and Shigeshigetani, who have become key foundation animals in global Wagyu herds. Michifuku was once the top marbling bull in the U.S. Wagyu Sire Summary, and Sanjirou consistently ranks high in marbling, ribeye area (REA), and yield.
To maximize marbling in future generations:
- Pair Monjiro descendants with cattle from the Kumanami family, which is renowned for its potent marbling genes (such as those from Shigeshigenami J10632).
- Use Tajima-line females that are known for their high marbling capacity, such as those from the Yasumi Doi J10328 lineage, which appears prominently in Michifuku, Haruki II, and their offspring.
2. Address Frame Size and Growth Potential
Monjiro’s line, while excelling in meat quality, tends to produce slightly smaller-framed offspring. This is especially true with Michifuku and Sanjirou, whose smaller frames can sometimes limit growth rates and overall yield.
To improve frame size and growth potential:
- Consider pairing with larger-framed Wagyu from the Shimane or Tottori lines, which are known for better growth capacity and overall size. Bulls like Dai-5 Natsufuji or Itohana could complement Monjiro’s line by improving size without sacrificing too much in terms of marbling.
- Avoid excessive inbreeding within the Tajima line, as this may exacerbate size limitations. Instead, aim for strategic outcrossing to balance frame size and meat quality.
3. Select for Ribeye Area and Yield
While Monjiro’s offspring typically show excellent marbling, ribeye area (REA) and yield can be moderate. Michifuku consistently ranked second in REA, and Sanjirou has performed exceptionally in terms of REA and yield rate. Shigeshigetani, Sanjirou’s half-brother, also shows promise for high REA and carcass yield.
To optimize ribeye size and yield:
- Choose females or sires from lines that emphasize size and muscle development, particularly those with thick ribs and high yield grades. Suzutani, the dam of Sanjirou and Shigeshigetani, is an excellent example of a female with strong genetic potential for REA, so look for similar bloodlines.
- Utilize bulls like Hokugoku 7-8 or Fukuou from Miyazaki to complement Monjiro’s genetics in producing larger ribeye sizes and higher overall yield.
4. Careful Mating Selection to Avoid Weaknesses
Monjiro’s primary weaknesses include relatively thin shoulder thickness, less depth in the lower limbs, and moderate adaptability to group feeding. Additionally, his line can sometimes produce offspring with white-tipped horns.
To counter these weaknesses:
- Select mating partners with strong shoulder width, depth, and adaptability, particularly those from Shimane or Tottori lines, which excel in these areas.
- Avoid inbreeding within the Hyogo line to prevent decreased growth rates. Instead, aim to diversify the genetic pool while maintaining key traits like marbling.
5. Strategic Linebreeding to Strengthen Desired Traits
Monjiro’s pedigree, rich in the Tajima line’s finest sires such as Yasumi Doi J10328, supports the use of strategic linebreeding to reinforce key traits like marbling and carcass quality. Sanjirou and Shigeshigetani are both linebred to Yasumi Doi J10328, further enhancing their marbling potential.
To strengthen desired traits through linebreeding:
- Utilize bulls or females that are linebred to Yasumi Doi J10328 or other notable sires from the Tajima line. This practice has already proven successful with Sanjirou and Shigeshigetani.
- Avoid excessive inbreeding that could lead to genetic weaknesses. Carefully plan matings to keep the inbreeding coefficient low while emphasizing key traits.
While Monjiro’s genetics are highly desirable, excessive linebreeding (inbreeding) within his bloodline can lead to a narrowing of the genetic pool, which may result in unwanted traits, such as reduced size or diminished fertility.
When planning a breeding program, it’s important to monitor the inbreeding coefficient to maintain genetic diversity and avoid the risks associated with inbreeding depression. Careful attention should be paid when linebreeding Monjiro or crossing with other heavily Tajima-influenced lines like Michifuku or Sanjirou. To reduce the risk of inbreeding issues, it’s advisable to outcross with cattle from strains like Shimane, Tottori, or Kagoshima that bring in fresh genetic material. This ensures genetic diversity while retaining the marbling and carcass quality traits.
Conclusion
Monjiro 11550 remains a cornerstone in Wagyu breeding, particularly for those focused on producing high-marbling, premium Wagyu beef.
His genetic legacy has been cemented through progeny like Michifuku, Haruki II, and grandsons Sanjirou and Shigeshigetani, all of whom have carried forward his valuable traits.
In summary, when breeding with Monjiro, the key focus should be on selecting mates from lines that strengthen his weaknesses in shoulder width and frame size while maintaining his extraordinary marbling qualities.
Careful attention to genetic diversity and the selection of lines with strong growth and physical traits will ensure a balanced, high-quality progeny ideal for both carcass quality and overall production efficiency.
References
小野健一. 日本名牛百選〔改訂版〕. 肉牛新報社.
