Long before function and performance were the main drivers of genetic selection, form (better known as “conformation”) was the driving method of genetic analysis. Many grew up hearing the age-old adages of “Form dictates function,” “Life’s too short to milk ugly cows,” or “Breed for type, feed for milk.” However, less than 1% of cows today leave the herd for udder problems or undesirable conformation. As the evolution toward function rather than form continues, what role should udders play in modern dairy selection criteria?
Current state of commercial udders
For most dairies in the U.S., the old swing bag cow of a bygone era is nearly extinct. Functionally correct udders have become commonplace in large, commercial dairies over the last 20 years. This is due in part to decades of prioritization, relatively high heritability for conformation traits and improved genomic selection. While many conformation traits could simply be de-emphasized today in favor of function and performance traits, the thought of migration entirely away from udder improvement feels foreign or risky to some. If conformation is viewed with function and performance in mind, what traits should be prioritized today?
What does an ideal, commercial udder look like?
Holstein Association USA Inc. published a study in 2022 called A Million Reasons Why Conformation Matters. This analysis provided a large-scale data analysis comparing conformation traits against several performance parameters including lifetime energy-corrected milk (ECM) production. From this analysis, several traits such as Teat Placement (RTP/FTP) and Teat Length (TL) were confirmed as traits best selected to a middle linear value (aka intermediate optimums).
Beyond this, two specific traits now appear to be new intermediate optimums: Udder Depth (UD) and Udder Cleft (UC). This makes sense since cows extreme in either direction do not function as well in commercial settings (UD – too shallow, too deep; UC – center support too strong, too weak; TP – too close, too far away; TL – too long, too short). Their research points to a higher ideal linear score for Fore Udder Attachment (FUA), Rear Udder Height and Width (RUH/RUW) when looking to maximize lifetime ECM.
How to select for the best commercial udders today
Like most genetic traits, a selection index or composite approach is the best way to prioritize multiple traits of importance all within one number. Unfortunately, the Holstein standard udder index, Udder Composite (UDC), does not reflect the current ideals supported by performance data – it still prioritizes UC and UD. Additionally, a look at the current top 200 NM$ active genomic bulls in the industry divided in half by UDC shows more commercially ideal udder traits in the bottom half for UDC (Table 1). This is a problem.
Since udder traits experienced such changes over the last couple of decades, it is time to rethink udder selection for commercial dairies. The American Jersey Cattle Association made a significant change to their udder index (JUI) in December 2023 as “emphasis was shifted in the JUI formula by making Udder Cleft, Udder Depth, Teat Placement, Rear Teat Placement (rear view), Rear Teat Placement (side view) and Teat Length two-way traits with an intermediate optimum. Fore Udder, Rear Udder Height and [Rear Udder] Width will now be capped at maximum value.” Perhaps other breed associations might benefit from following Jersey’s lead.
With the limitations of UDC in mind, what is the best way to select for modern, commercial udders? Three key items should be considered when designing udders for the next generation of commercial cows.
- Prioritize real udder issues on the dairy. Are teats too close or short? Are udders too shallow or too deep? Are cows leaving the herd because of poor udder conformation or teat positioning issues? Genetic selection should reflect the needs of the dairy today and not be stuck in the philosophies of the past.
- Sometimes zero is just right. Contrary to popular belief, not all linear traits should be to the right. The data suggests the bottom five udder traits (UD, UC, FTP, RTP and TL) should be selected to zero; extreme in either direction for these parlor traits are where herds are more likely to get in trouble today (Figure 1).
- Keep udder traits in perspective to the rest of the cow. Despite the milking facilities (robot, parallel parlor, rotary parlor, etc.), every herd still needs to get cows pregnant, efficiently produce large volumes of milk and keep cows healthy. Consider a selection index approach that reflects the broader needs of the dairy while prioritizing functional udder traits.
When it comes to designing ideal commercial udders, don’t forget that function is ultimately the top priority. If a cow makes lots of milk, carries it until the next milking and efficiently deposits it during her milking session, then she has an ideal commercial udder.
