Podcast Summary: Cattle Chat — Epigenetics and Udder Quality

Episode Date: January 16, 2026
Hosts: Dr. Brad White (A), Dr. Bob Larson (B), Dr. Phillip Lancaster (C)
Podcast: Beef Cattle Institute at Kansas State University (BCI Cattle Chat)

Episode Overview

This episode focuses primarily on two key topics:

1. Epigenetics and Bull Selection: The hosts tackle a listener's question about whether the differing development and management of two genetically identical bulls could impact their calves or their own longevity and fertility. They discuss genetic expression, epigenetic markers, and the complexities around DNA versus phenotype.
2. Udder Quality in Cow–Calf Management: The discussion shifts to udder quality—its importance, heritability, environmental effects (such as mastitis), and its real-world priority in selection and culling decisions.

The show’s tone is conversational and practical, geared toward beef producers and those interested in applied cattle genetics.

Key Discussion Points & Insights

1. Listener Question on Twin Bulls, Development, and Calf Outcomes

(03:01–16:27)

Scenario

• Two genetically identical (twin) bulls are raised differently:
  • Bull A: Goes into a commercial herd early (9 months), starts breeding cows younger, likely smaller, experiences less post-weaning growth.
  • Bull B: Is weaned, put on feed/test, does not breed until 24 months, likely larger at maturity.

Core Questions:

• Will their calves differ due to “nature” vs. “nurture”?
• Does the bull’s environment/nutrition affect their DNA or the genetics of their offspring?
• What about bull longevity and herd productivity?

Genetics vs. Epigenetics

• Traditional Viewpoint:

  • "Does that change the DNA in the semen that the bulls produce? ... the answer would be easily, no." —Dr. Larson (04:35)
  • DNA sequence is unchanged despite environmental influences.

• Modern Perspective & Epigenetics:

  • "...what's expressed could be different." —Dr. White (05:32)
  • Dr. Lancaster: Epigenetic markers (like methyl groups) can be passed on and influence gene expression, though the primary nucleotide sequence remains the same. Nutrition and stress especially in utero or early life can impact these markers.
  • "Those secondary molecules influence the expression of genes ... some of those are passed on." —Dr. Lancaster (06:29)
  • "There's some evidence that these secondary molecules, this epigenetic component, is heritable to some degree." —Dr. Lancaster (11:44)

• Male vs. Female Programming:

  • Female eggs are all formed before birth; epigenetic changes can originate in utero.
  • Sperm are produced continuously after puberty; environment and health during testicular development and spermatogenesis could matter.
  • "Every egg she will ever ovulate was made ... before she was born... That's not true for sperm." —Dr. Larson (07:13)

Notable Quotes

• "What I led with was, of course not. There's no difference in the bulls based on environment, their DNA is the same. That's kind of the old answer. The new answer is I'm not sure." —Dr. Larson (08:59)
• "I would be kind of surprised if there was a big difference, but I also wouldn't be surprised if there's a small difference." —Dr. Larson (08:59)

Longevity and Herd Performance

• Early breeding versus later breeding could impact bull body type and possibly longevity, but which scenario is “better” is unclear.
  • "It's not clear to me which of those bulls would have more [longevity]." —Dr. Lancaster (14:41)
• True impact may be herd-dependent and more related to nutrition and developmental timing, particularly pre-weaning.

Productivity Tradeoffs

• Early-starting bull gets a “redshirt year” (sports analogy): one more year of potential productivity, though overall longevity or performance could vary.
  • "Even if he stays in the herd a year less, he's still got those first year calves going." —Dr. White (16:08)

Practical Advice

• Focus management on keeping bulls in a moderate, healthy condition—not over- or undernourished—to maximize fertility and longevity.
  • "Monitor body condition, monitor the diet these bulls are given and kind of keep them in that window of pretty good body condition, but not over fat." —Dr. Larson (17:13)

2. Udder Quality: Heritability & Practical Selection

(17:27–22:13)

Why Udder Quality Matters

• Poor udder quality (large/balloon teats, poor attachment) is a management headache and directly affects calf health and access to milk.
  • "No producer, no calf wants to deal with a cow with poor udder quality." —Dr. Larson (18:05)

Heritability and Selection

• Udder traits (attachment and teat size) have measurable heritability:
  • "Heritability of udder attachment around 0.2 to 0.3 ... heritability of teat size at 0.5." —Dr. Lancaster (20:42)
  • Moderately heritable: Selection pressure can work if needed.
• Udder quality is usually a culling criterion rather than a rigorous selection trait, unless herd-specific problems arise.
  • "If I'm not having very many problems, it's not very high on my list of things to adjust. So I think it really is a herd by herd basis." —Dr. Larson (21:43)
  • "I'm not gonna keep heifers out of cows that have bad udders." —Dr. Lancaster (19:26)

Environmental Effects: Mastitis

• Environmental insults (like mastitis) can create poor udder/teat appearance, sometimes being confused for heritable traits.
  • "I think we underestimate how often mastitis could happen in beef cattle because we're not milking them every day. We don't have the ability to observe it." —Dr. White (19:58)

Real-World Priorities

• Udder quality is more frequently a matter for culling than for proactive heifer selection, unless persistent problems exist within a herd.
  • "I would not base ... selection [of] heifers [on] udder quality ... so low as to be inconsequential on my heifer selection." —Dr. White (20:08)

Notable Quotes & Memorable Moments

• On Genetics vs. Epigenetics:
  "The DNA hasn't changed. But does it affect their offspring? I'm going to lean towards probably not. Or if it does not much ..." —Dr. Larson (08:59)

• On Udder Quality Selection:
  "It's not a selection. It's a culling criteria." —Dr. Lancaster (19:31)

• On Environmental Influence:
  "That's not heritability, that's just environment." —Dr. Lancaster (21:05)

Timestamps for Key Segments

• Listener Question & Genetic/Epigenetic Discussion: 03:01–16:27
• Bull Longevity & Productivity: 13:02–16:27
• Udder Quality Discussion: 17:38–22:13

Summary: Takeaways for Producers

• Bull Development: While DNA is unchanged by postnatal environment, gene expression (epigenetics) might be slightly influenced but is unlikely to drastically change offspring growth or mature weight. Early-life nutrition, particularly pre-weaning, appears critical for long-term testicular health and fertility.
• Practical Bull Management: Keep bulls on a healthy, moderate plane of nutrition; avoid both overfeeding and underfeeding for best postseason and reproductive results.
• Udder Quality: Address serious udder/teat issues through culling rather than selection, unless major herd-wide problems arise. Both genetics and environment (injury, mastitis) can play a role, but real-world impact is usually herd-specific.

For more questions, listeners are encouraged to reach out to the hosts at bcis@ksu.edu.