Archive for Genetics

The Bullvine seldom talks about the processing of milk into product when it comes to writing about the breeding of dairy cattle. We expect it happens even less frequently that dairy cattle breeders consider the yield their processor obtains in products from the milk they ship. The different kappa casein genotypes found in today’s dairy cattle can have a significant effect on the volume and quality of cheese produced from milk. Here are some interesting details that we found from our research on this subject.

The Situation

Dairy cattle are evaluated for their ability to produce the percentage of protein in milk and the total protein yield.  Milk processors find that: 1) some milks clot quickly, its cheese is firm and produces the most cheese per unit of milk; 2) some milks clot, but not quickly, and have varying degrees of firmness and produces 10%-15% less cheese, and 3) some milks do not clot. Cheese makers are not prepared to buy milk that fits into the latter category. Studies from Europe and North America have found a strong association between the kappa casein genotype BB and milk that clots quickly, produces firm cheese and has a high volume of cheese yield.

The situation of poor or non-clotting milk came to international attention in the 1970’s when Italian cheese makers were no longer able to make their cheeses from the milk from certain farms. After studying the situation, it was determined that some daughters from North American Holstein sires produced milk that was not desirable for cheese making.  In-depth study identified the problem to be with the kappa casein produced by these non-Italian sires’ daughters.

Kappa Casein Alleles

At least nine alleles have been identified for kappa casein. Specifically, three alleles, A, B, and E, dominate in global dairy cattle populations. Initially, it was thought that two alleles, A and B, were the main ones present in dairy cattle. However, a third allele, E, was found to exist approximately 10% of the time. E is the allele associated with the milk that does not clot to make cheese.

Cheese Yield by Genotype

A synopsis of the published findings on kappa casein genotypes follows:

  • Cheese from the milk of BB cows’ clots 25% faster and is twice as firm as cheese made from AA cow’s milk.
  • Milk from BB cows produces 1.0- 1.5 lbs (about 10%) more cheese per cwt of milk than milk from AA cows.
  • Milk from AB cows is about midway between BB and AA cows for clotting speed, firmness, and yield.
  • Milk from EE cows does not clot and is not suitable for cheese making
  • Milk from AE cows is also considered by most cheese makers to be unsuitable.
  • The literature is not informative on the properties of milk from BE cows. There are suggestions that it may be similar to milk from AA cows when it comes to cheese making.
  • A 1985 study by Okigbo, Richardson, Brown and Ernstrom found that milk with impaired clotting properties was not improved by mixing it with an equal amount of well-clotting milk.

General Stat’s with respect to Kappa Casein

Initially, our focus was on kappa casein relative to North American dairy cows. However, we found interesting information from published studies in Italy, France, Estonia, The Netherlands, Scandinavia, and Turkey.  Milk for cheesemaking is important in these countries because from 40% to 75% (Italy) of the national milk is used to make cheese. Some additional facts include:

  • About 10% of North American Holsteins are BB.
  • North American Jerseys have a significantly higher percent BB than do Holsteins. Likely the result heavy use of two BB Jersey sires from twenty years ago.
  • Globally Brown Swiss are reported to be 35% BB.
  • Holsteins in Europe have between 15% and 23% BB
  • Water Buffalo are almost 100% BB. India, the world’s largest milk producing country, gets half its milk from Water Buffalo.

What About Current Holstein Sires?

Table 1 is the frequency of occurrence for the kappa casein genotypes for the top North American proven or most used Holstein sires.

Table 1 – Kappa Casein Genotype Profiles for North American Holstein Sires

Grouping Total Sires BB AB AA BE AE EE
Most Registered Daughters – USA* 20 2 6 4 4 4 0
Most Registered Daughters – Canada** 20 2 8 5 0 5 0
Top Proven TPI Sires *** 20 4 8 6 1 1 0
Top Proven NM$ Sires *** 20 2 7 6 2 3 0
Top Proven CM$ Sires *** 20 2 6 6 2 4 0
Top Proven LPI Sires *** 20 6 6 5 0 3 0
Top Proven Pro$ Sires *** 20 6 6 6 1 1 0
Average (%)   17% 34% 26% 7% 16% 0%

* For time period two weeks prior to April 03, 2017
** Based on registrations in 2016
*** April 2017 Proofs

Some points that should be noted from this table include:

  • The sires in Table 1 have a higher occurrence of BB (17%) than in the general cow population (10%).
  • There are no EE sires but the 16% level of AE should concern breeders and A.I studs when it comes to cheese firmness and lost potential yield in the future.
  • The frequency of BB & AB is higher in the Canadian sire proof groupings than in other groupings.
  • The overall 38% gene frequency of the B allele gives hope that genetic progress to eliminating E and reducing the A allele should be possible in the not too distant future.

Some BB daughter proven sires that topped or were near the top of the groupings in Table 1 are listed in Table 2.

Table 2 –  Leading BB Daughter Proven Sires

Sire NAAB Code Sire Stack Rank
Aikman 250HO01043 Snowman x Baxter x Goldwyn #2 LPI, #20 Pro$
Aikosnow 200HO03914 Snowman x Baxter x Goldwyn #4 Pro$, #14 LPI
Balisto 29HO16714 Bookem x Watson x Oman #20 TPI
Bob 7HO11752 Bookem x Oman x Manat #8 TPI
Camaro 250HO01109 Epic x Freddie x Lucky Star #9 LPI, #19 Pro$
Donatello 7HO11525 Robust x Planet x Elegant #14 US Registered, #14 CM$, #17 NM$
Dragonheart 7HO12111 Epic x Planet x Elegant #1 Pro$, #4 LPI
Facebook 200HO03753 MOM x Airraid x Shottle #20 CAN Registered
Impression 200HO00560 Socrates x Potter x Durham #1 CAN Registered
Living 200HO06573 Epic x MOM x Shottle #12 Pro$, #19 LPI
Punch 7HO11207 Boxer x Oman x Manat #13 Pro$, #18 LPI
Rookie 7HO11708 Bookem x Bronco x Shottle #9 TPI
Trenton 7HO13094 Sterling x Robust x Planet #9 CM$, #12 NM$

One BB genomically evaluated sire is in the top registered USA sire grouping in Table 1:

  • Jedi                       (7HO13250)                             (Montross x Supersire x Bookem)                #8 US Registered

What About Genomic Sires?

With over half of the semen being used coming from genomically evaluated sires it is important to consider this category. In some herds, only genomic sires are used. However, to summarize the kappa casein genotype frequency for this group is not reasonable as many of the top sires on the April 2017 listings are too young to have semen available yet. As well the usual cautions that The Bullvine gives apply do not overuse any one genomically evaluated sire as their indexes range from 55% to 75% REL. Moreover, take into consideration the future inbreeding coefficient of these sires as a breeder may already have those sires close up in their animals’ sire stacks.

Some genomically evaluated Holstein and Jersey sires that are BB for kappa casein that are worthy of breeder consideration include:

Table 3 – High Ranking BB Genomic Evaluated Sires

Sire NAAB Code Sire Stack          CM$          NM$      TPI/JPI          LPI         Pro$
Holstein              
Achiever 29HO18296 Yoder x Altafrido x Robust 1062 1023 2788 3332 2902
AltaCraig 11HO11749 Stoic x Supersire x Massey 842 806 2643 3188 2498
AltaForever 11HO11821 Silver x Freddie x Obrian 774 746 2642 3313 2767
Baylor 551HO03419 Delta x Bob x Uno 874 846 2735 3379 2722
Cam 7HO13592 Jedi x Moonray x Bookem 893 876 2727 3263 2709
Cardinals 200HO10668 Yoder x McCutchen x Robust 804 785 2682 3108 2155
Galahad 200HO10755 Penmanship x Jacey x McCutchen 732 678 2636 3377 2695
McGuffey 551HO03350 Montross x Robust x Mac 834 820 2683 3199 2657
Medley 29HO18343 Yoder x Balisto x O-Style 986 966 2779 3447 2962
Powerfull-PP 224HO04510 Powerball-P x Supersire x Colt-P 670 635 2462 2962 2225
Selfie 224HO04273 Supershot x Aikman x Larson 749 734 2561 3231 2561
Yale 7HO13328 Yoder x Altafrido x Robust 836 824 2683 3286 2654
Jersey              
AltaBlitz 11JE01320 Axis x Kilowatt x Karbala 619 593 173 1803 1701
Charmer 29JE04009 Chili x Dividend x T-Bone 630 588 178 2010 1824
Halt 29JE03989 Harris x Hendrix x Redhot 664 628 187 1911 1744
Joyride 200JE10011 Rufus x Paramunt x First Prize 152 139 48 2014 1712
Torpedo 250JE01456 Santana-P x Fastrack x Nathan 408 390 118 1823 1514
Tyrion 203JE01632 Hulk x Action 782 736 231 1755 1587

Take Home Ideas

The Bullvine offers the following ideas for breeders and breeding industry people to consider:

  • Cheese Making: In the future, it is entirely possible that cheese processors will not buy milk from Holstein herds that cannot guarantee that their cows are at least a high percentage are BB. Jersey herds and totally BB Holstein herds are likely to be paid a premium for this milk.
  • Niche or Mainstream: In the next five years breeding to increase the percent of BB females will be niche. However, as more and more milk is used to make cheese selection for the B allele and away from the E allele is likely to be mainstream. Selecting sires on total protein without regards to the kappa casein profile of those sires should become a practice from the past.
  • Breeding Animals: Breeders and breeding organizations would be well advised to commence selecting for the B allele when it comes to sire and ET donor selection. An achievable objective would be for A.I. studs to only enter BB and AB bulls into stud starting in 2019. Breeders are advised not to flush any females that are EE, AE and perhaps even BE starting in 2019 or before. Breeders need to ask their semen sales reps for a sire’s kappa casein profile before buying semen. Bull kappa casein profiles are not included in CDCB or CDN files but are most often included in A.I. stud electronic bull files or hard copy catalogs.
  • Research: More research is taking place in many countries of the impact of kappa casein genotype on cheese production. At the University of California (Davis) there are major projects underway on how to use genetic engineering to eliminate the E allele and to fast track changing Holsteins into being BB.

The Bullvine Bottom Line

One characteristic, like kappa casein, cannot rule the breeding, milk production and milk processing industries. However, with a higher and higher percentage of dairy cows’ milk being used to make cheese, breeding for animals with the BB kappa casein genotype can no longer be ignored or thought not to be important. Breeders are advised to ask their semen suppliers for the kappa casein profiles of sires before they purchase semen. Starting immediately sires with EE and AE profiles should be avoided and if the semen is already in the tank then even throwing it out may make good business sense. Because producing females that are EE or AE will delay when premiums may be possible for milk sold for making cheese.

 

 

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Categories : Genetics

Dairy breeders spend considerable time choosing the next round of bulls to use. That’s important because improvements in genetics has a significant influence on the generations that follow.  Nevertheless, future performance will depend on how epigenetics regulates the DNA acquired through breeding.  When epigenetics enters the picture,  breeders will need to re-consider how they breed and manage their dairy cattle.

What’s Epigenetics?

Epigenetics underlies processes that affect health, ­ fertility, longevity and many traits of dairy cattle. Epigenetic effects differ from direct genetic effects because the animal’s DNA sequence is not changed by epigenetic processes. Rather, epigenetic processes act by regulating whether genes within DNA sequences are “turned on” or “turned off” without any change in the DNA sequence. (Read more: FORGET GENOMICS – EPIGENOMICS & NUTRIGENOMICS ARE THE FUTURE)

Genetic and Epigenetic Differences

Traits such as milk yield, milk protein, conception rate, somatic cell count and udder conformation are heritable, meaning that differences among animals in these traits can be accounted for by family relationships among sires, dams and ancestors. Heritability ranges from around 3% to over 50% for various traits, therefore 3 to 50% of differences among animals are accounted for by differences in their DNA sequences.

The non-genetic variation in traits is included in what we refer to as environmental effects. Weather, feed, facilities, management practices and everything else that cattle are affected by in a herd fits into environmental effects.  Many responses of cattle to environmental effects are regulated by epigenetic or closely-related processes at the cellular level in animals.

Epigenetic effects do not change an animal’s DNA sequence (genome). Instead, epigenetic effects alter how individual genes or groups of genes are controlled or as geneticists say “silenced or differentially regulated” throughout an animal’s life. Originally, epigenetic effects were thought to represent only alterations that could be passed to the next generation without changing in the animal’s genetic code. More recently it seems that epigenetic effects may impact various tissues and organs during certain periods in the animal’s life, without being passed to the next generation.

Epigenetic Triggers

Animal scientists are using the term “developmental programming” to define practices that may trigger epigenetic effects. Developmental programming may act through epigenetic or similar pathways to influence almost any trait of interest in dairy cattle. For dairy farmers, it matters little whether the action occurs through one mechanism or another, as long as responses are predictable and repeatable.

Repeatability means that there is a fairly predictable pattern of an action causing a specific or response separated by weeks, months, years or generations. That makes it challenging to determine cause and effect, without careful observations, good records and repeated verification.

Epigenetic effects may be triggered by conditions associated with natural biological process or by adverse conditions such as negative energy balance, heat stress, exposure to toxins or other disturbances. Epigenetic effects can be either positive or negative, so as we learn more it will be useful to incorporate management practices that stimulate positive effects and limit negative ones.

Epigenetic Effect #1        Calf Feeding and Future Performance

One epigenetic or epigenetic-like effect is the latent response to feeding higher levels of milk or replacer to heifer calves. Calves fed at higher levels produce more milk in first lactation about 2 years later, so the response occurs beginning about 700 days after the action. Preliminary data suggest that heifers fed more milk develop more mammary epithelial cells that become milk-secreting cells when first lactation begins. This is the kind of epigenetic effect that one would see for stem cells that are dividing rapidly when the milk is being fed. The exact regulatory mechanism for this effect is yet to be determined.

Epigenetic Effect #2        Milking Frequency Immediately After Calving

Similar to the situation in calves fed more milk, it has been demonstrated that cows milked 4X daily during the first 3 weeks of lactation and then 2X daily thereafter produce considerably more milk than cows milked 2X from freshening. The 4X milking early in lactation apparently stimulates development of more milk-secreting cells and these then remain throughout lactation, even when milking frequency drops to 2X.

Epigenetic Effect #3        Embryo Survival

It is highly probable that negative epigenetic effects occur when eggs (oocytes) are developing within the ovary when a cow is under stressful conditions. Such can be the case for the egg ovulated by an energy and/or health stressed cow that comes into heat 80 days post calving. The egg ovulated at day eighty actually started growing as an oocyte within her ovary about 3 weeks before calving.

 Oocytes that develop under these stressful conditions have low survivability as embryos. Their fertilization rate is normal, but they degenerate and die at a higher rate in the first week after fertilization. This is a classical example of an adverse epigenetic effect. Our North Carolina State research team published the first report of this effect in 1992. It is referred to as the Britt Hypothesis and it has taken about 25 years for scientists to begin to understand this phenomenon at the DNA level.

Stay Tuned As We Learn More

There is a strong interest in understanding how epigenetics affect the developing fetus and how management of the pregnant cow influences the future long-term responses of the calf she is carrying. During fetal stages, tissues that will form muscles, mammary tissue, the immune system and all other systems undergo development.  We will see a lot of new discoveries about epigenetics in these areas in the years ahead and this will give us tools to support development of better calves during pregnancy.

Husbandry practices trigger many of the epigenetic effects, both good and bad.  Understanding how such effects are mediated will give us husbandry tools to improve both DNA-based genetics and ways to regulate the DNA in a beneficial manner.

The Bullvine Bottom Line

The Bullvine found that this information shared by Jack Britt assisted us in better understanding the topic of epigenetics.  Yes, epigenetics is yet one more piece of the puzzle that progressive breeders are likely to use in the future to both breed and manage their dairy herds.

 

 

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Categories : Genetics

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