Archive for July, 2008

Sex-sorted semen: What researchers have learned

By Dr. Joseph C. Dalton
University of Idaho

Sex selection is arguably one of the most sought after and misunderstood reproductive technologies in history.

More than 2000 years ago, Greek philosophers suggested that the right testis produced males, and the left testis produced females. Of course, this is not the truth, as there are two populations of sperm – called X-chromosome-bearing and Y-chromosome-bearing sperm.
In 1983, a collaborative group of researchers from Oklahoma State University, USDA, and Lawrence Livermore National Laboratory reported on the use of a flow cytometer to determine the difference in DNA (genetic material) content between X- and Y-chromosome-bearing sperm from cattle, sheep, pigs and rabbits.

Unfortunately, the initial procedure killed the sperm, and it wasn’t until the late 1980’s that USDA researchers refined the procedures to sex-separate live sperm via flow cytometry/cell sorting. The USDA patented the sperm-sorting technology in 1991.
During the late 1990’s, XY Inc., a Fort Collins, Colo.-based company working with researchers at Colorado State University, further developed technology and procedures that improved upon USDA’s work.

In early 2005, sex-sorted semen became commercially available in the United States. As data is accumulated by researchers and AI studs, the answers to the following questions are becoming clearer:
• What are the results following use in heifers?
• What results can you expect?
• What are the results following use in lactating cows?
• Why is there a lowered conception rate following the use of sex-sorted semen?

Results: Heifers

Sex-sorted semen research and commercial use has traditionally focused on heifers because well-managed heifers tend to have first-service conception rates (resulting from AI with frozen-thawed, unsexed semen) of up to 70%, compared to less than 40% in lactating cows. Nevertheless, nearly all of the early research trials in dairy heifers using a similar dosage (1.5 to 2.0 million sperm cells) to what is available today (2.1 million sperm cells) provide evidence of decreased conception rates following AI with sex-sorted semen as compared to unsexed, control semen.

As shown in Tables 1 and 2, the range in conception rate following AI with sex-sorted semen was 31% to 65%. Furthermore, the conception rate achieved following the use of sex-sorted semen, expressed as a percentage of the conception rate achieved using unsexed control semen, was 44% to 90%.

Lastly, there is no evidence that semen deposition into the uterine horns enhances conception rate as compared to deposition into the uterine body (Tables 1 and 2).
What about more recent data? In a retrospective study presented by Select Sires at the 2007 American Dairy Science Association Annual Meeting, 16,587 services to sex-sorted semen (2.1 million sperm per dose) were evaluated and the average conception rate was reported to be 44%.
Furthermore, the conception rate achieved following AI with sex-sorted semen averaged 85% of that achieved with unsexed, control semen at first service. In fact, 74% of herds achieved a conception rate ≥ 70% of that obtained with unsexed, control semen at first service. In the 25 herds that used ≥ 100 doses of sex-sorted semen, the conception rate to sex-sorted semen averaged 48% (range 38 to 72%), compared to a first-service conception rate to unsexed control semen of 54% (range 38% to 70%).

What can you expect?

There is ample data in dairy heifers to support the expectation of an average conception rate to sex-sorted semen of approximately 70% to 85% of the conception rate to unsexed control semen used at first service. Consequently, if you currently achieve a 65% conception rate at first service in your heifers with frozen-thawed, unsexed semen, you can expect to achieve (with good management) a conception rate between 46% to 55% with frozen-thawed, sex-sorted semen at first service. As can be seen from Tables 1 and 2 and the data in the preceding paragraph, there is large variation in conception rates following AI with sex-sorted semen. This is not surprising as the level of management plays a role in the success or failure of any new technology, and therefore must be considered.

Most reports describe an accuracy of approximately 90% in the predetermination of the sex of calves born. Furthermore, calves born as a result of the use of sex-sorted semen are normal, as no differences in neonatal death rates, birth weights, weaning weights, gestation length, or incidence of abnormalities have been reported by researchers.

Results: Lactating cows

Although the current recommended use for sex-sorted semen is in virgin heifers only, recent research has focused on use in lactating dairy cows. Researchers from Finland reported an average conception rate of 21% with sex-sorted semen (2.0 million sperm per dose) and 46% with conventional, unsexed semen (15 million sperm per dose) following first service in Holstein cows. No synchronization programs were used in this study. The conception rate achieved with sex-sorted semen was 45.6% of conventional, unsexed semen. No synchronization programs were used in this study.

In a study conducted by U.S. scientists, Holstein cows (lactation 1 to 4 and between 20 to 140 days in milk) received AI with sex-sorted semen or conventional, unsexed semen at natural heat, or after synchronization with prostaglandin or Ovsynch. The overall conception rates were 25% and 37.7% for cows in the sex-sorted semen and conventional, unsexed semen groups, respectively.

Positive conception figures

The conception rate achieved with sex-sorted semen was 66.3% of conventional, unsexed semen. Cows receiving AI with sex-sorted semen following a natural heat had a greater conception rate than cows that were synchronized with either prostaglandin or Ovsynch. Furthermore, conception rates following AI with sex-sorted semen at 100 days in milk (or more) were approximately 8 percentage points higher than earlier in lactation, and greater than 6 percentage points lower in older cows (third and fourth lactations) than younger cows.
Consequently, these researchers concluded that the highest conception rates following AI with sex-sorted semen may be achieved in first and second lactation cows exhibiting natural heat and greater than 100 days in milk.

Selecting ‘repro normal’ cows

Another study conducted by XY Inc. focused on the efficacy of selecting only “reproductively normal” lactating dairy cows for timed AI (Ovsynch) with sex-sorted semen. All cows (lactation 1 to 9) were initially enrolled in Presynch (two injections of prostaglandin 14 days apart). Ultrasonography was performed approximately 14 days after the second prostaglandin injection, and only those cows with normal ovarian and uterine status (55% of the total evaluated; average days in milk = 72) were enrolled in Ovsynch. Timed AI was performed 16-19 hours after the second GnRH injection of Ovsynch, and occurred, on average, at 82 days in milk.

The overall conception rates were 40.4% for cows inseminated with sex-sorted semen, and 55.6% for cows inseminated with conventional, unsexed semen. The conception rate achieved with sex-sorted semen was 72.6% of conventional, unsexed semen. Although the researchers concluded that conception rates of presynchronized, reproductively normal lactating cows following timed AI were acceptable, the researchers cautioned that the study was very small (115 animals) and should not be over-interpreted.

Why the lower rate?

Why is there a lowered conception rate following use of sex-sorted sperm?
The decreased conception rate following the use of sex-sorted sperm may be due to:

1. sperm injury during the process of staining prior to flow cytometry,

2. exposure of sperm to a powerful laser beam during sorting,

3. centrifugation to concentrate the sperm prior to filling straws, and

4. the current inability to determine before separation if a semen sample will be able to withstand sex separation, freezing and thawing, and retain acceptable fertility. It is widely known that sperm from different bulls differs in the ability to withstand freezing. Therefore, sex-sorted sperm from different bulls will most certainly differ in the ability to tolerate sexing and freezing.

Final thoughts

The inherent lower fertility of lactating cows makes the use of sex-sorted semen in cows more problematic than in heifers. Consequently, usage of sex-sorted semen in lactating dairy cows is still not recommended. The current recommendations for sex-sorted semen are:

• Use in well-grown, well-managed heifers.

• Administer AI approximately 12 hours after observation of heat.

• Thaw straws using warm water (95 to 98 degrees F) for a minimum of 45 seconds.

• Do not use sex-sorted semen in timed AI programs.

Accurate heat detection and well-trained inseminators will be mandatory to maximize fertility with sex-sorted semen. In general, herds with higher conception rates have a greater opportunity to reap a return on their investment as these herds may be able to tolerate a reduction in conception rate as compared to herds with marginal to low conception rates.

Overall management crucial

In addition, sex-sorted semen will most likely generate a greater return when heifer values are high and when it is used to inseminate the most genetically advanced heifers. Herds with poor management, inaccurate heat detection, and improper semen handling will likely experience plummeting conception rates while using sex-sorted semen.

FYI
■ To contact Joseph C. Dalton, University of Idaho Extension dairy specialist, Caldwell Research and Extension Center, call 208-459-6365 or e-mail jdalton@uidaho.edu

Nutrigenomics: Fine-tuning gene’s motor

By Ron Goble

LEXINGTON, KY – Dr. Ronan Power was recipient of the 2008 Scientific Medal of Excellence presented at Alltech’s 24th International Animal Health and Nutrition Symposium. Power was recognized for his work in advancing the use of nutrigenomics and gene expression profiling, as tools for improving nutritional strategies, animal health and production.
During his presentation, Power made it clear that nutrigenomics is not defined as genetics.
“We’re not altering the genetics of an animal. Nor are we genetically engineering the animal. What we are doing with carefully selected nutrients is fine-tuning the motor that is already there,” he explained. “Genes and DNA represent the motor that is present in every cell and every tissue of an animal. We are finding ways to tweak the activity of genes that are already present, and switch on good genes and keep bad ones switched down. For example, keeping stress response genes switched down with proper nutrition is a win-win situation. The animal is healthier, more productive and has a lot more possibility of improving efficiencies.
“We’ve also made significant strides in improving activity of genes that are involved in energy production pathways. So in that way the animal can produce more energy from a given diet. That means it is more effectively using its diet and less wasteful and more productive as a result,” the researcher said.
According to Power, there exists a fantastic range of opportunity out there for using this type of research for new product development and new nutritional strategies.

Turn gene switch on/off
“It has been discovered that genes can be switched on or off and affect performance significantly as a result. A strip – looking a lot like a supermarket bar code – represents the activity of a single gene involved in metabolism. Switching a gene on or off can impact the metabolism activity,” Power said.
After 2 1/2 hours of fasting, researchers begin to see differences emerge in the gene activity profile. In 5 1/2 hours, the differences are even more pronounced. After 24 hours they observed a totally different pattern than what they started with, indicating total metabolic reprogramming that has controlled the level of the gene, which occurs during the withdrawal of nutrients from an animal.
“Why is it important to understand this interaction between diet and genes?” he asks. “If you can alter gene expression by adding nutrients to the diet, then by extension, you can alter biological function. And in the relatively new science of genomics we seek to alter both gene expression and biological function in a positive manner.”
Using nutrigenomics allows researchers to move ahead faster. Because gene expression changes in a matter of hours or days, you can run these trials for a much shorter duration. Yet once you are finished, instead of having perhaps 40 or 50 data parameters, you can have literally thousands upon thousands of data points from one single experiment. That’s the great attraction of nutrigenomics.
“In fact, if there is one challenge with this approach, it actually can make managing and absorbing the absolute glut of data you get from every experiment that you run. At that point, it must be married with very powerful computational techniques and tools to process and analyze that huge volume of information,” Power says.
The bottom line is to use nutrigenomics to determine the real inside story on how a nutrient is working exactly in the cells and tissues of the animal species you are studying.
Practical applications of nutrigenomics are: The ability to replicate rapidly nutrients in the diet for their potential to improve or enhance animal health and production efficiency.
You can use nutrigenomics as an important tool to rapidly assess the potential impact of nutrition and diet on important quality parameters.
Power is currently the director of research and serves as director of the Nutrigenomics Center at Alltech’s North American Biosciences Center in Nicholasville, Ky. He also oversees work in Alltech’s European Biosciences Centre in Dunboyne, Ireland, and provides basic leadership for external molecular research programs around the world.
In recent years, Power has been the key architect of Alltech’s nutrigenomic research program, examining the effect of nutrition on gene expression. Through his work with collaborators, he has demonstrated the value of using Alltech’s Sel-Plex® as a source of selenium and differentiated it from supplemental sources in the form of selenomethionine and inorganic selenium salts.
He has also used a functional genomic approach to demonstrate the effects of organic forms of selenium on basic physiological processes associated with fertility in livestock and poultry, neurological degeneration, oxidative stress and energy metabolism. His work has provided clues into nutritional mechanisms that can be used to alter the aging process and has resulted in four provisional patents on applications of selenium yeast in altering key metabolic processes

FYI
■ For information on Dr. Ronan Power’s work on nutrigenomics, e-mail bfrey@alltech.com.

IDF global warming summit: the heat IS on

IDF Global Warming Summit: The heat IS on

Kees Gorter, a producer from the Netherlands, talks about the biogas plant on his dairy during a summit panel.By Susan Harlow, editor, Northeast DairyBusiness

 Just agreeing that climate change is real is a “fundamental” advance, pointed out one of the organizers of  the  International Dairy Federation’s (IDF) First Dairy Summit. Several hundred producers, government officials and journalists from 40 countries gathered in Edinburgh, Scotland, June 23-26, to talk about how climate change affects their industries, and dairy’s responsibility in the global warming issue.
 At the end, Paul Wolcott, a New York producer, urged other attendees to take what they had learned home with them and put it to work. “The best way to start is to be informed, including an understanding of consumer and environmental issues,” he said. “We need to ask consumers what they want and work hard to provide it. We will not get credit for just talking.”
 IDF and the summit’s sponsors, DairyCo, a British dairy organization, and Swedish milking equipment manufacturer DeLaval, set up a website to provide a forum for climate change. The website is www.sustainabledairyfarming.com.

 

 Dairy’s problem; dairy’s responsibility

Climate change isn’t just somebody else’s problem. If global temperatures rise by 1.8  to 4 C. over the next century, as projected, grain yields will drop 10% with each 1 C. increase, said John Gillland, chair of the Rural Climate Change Forum. Greater weather volatility will also hurt.
     The United Nation’s Food and Agriculture Organization (FAO) says 18% of greenhouse gas (GHG) emissions come from livestock, while a newly released  preliminary report by the International Farm Comparison Network (IFCN)  shows that 2% comes from dairy. Most GHG emissions from dairy are at the farm level, said Pierre Gerber, FAO livestock policy officer.
     But dry, desert countries are already feeling the changes. Those countries are “like canaries in a  coal mine,” said Tim Burfitt of New South Wales and Australia’s Department of Primary Industries. In Australia, where rainfall has declined 20% over the last decade, milk production has dropped by 2 billion liters since 2002 mainly because of climate change. Australian dairy farmers are moving away from pasturing to more intensive feeding concentrates.

If the public wakes up to the fact that Australian dairy, which exports most of its product, is essentially shipping water overseas, farmers will be hard-put to defend their industry, said Stephen Coats of Dairy Australia.
     In Egypt, where the vast majority of people live in the Nile Delta, Walid El-Sherbiny co-owns an 800-cow dairy with 65 workers. Water is the critical issue here, too. Groundwater is too salty for cows to drink; meanwhile, the country is losing arable land to a growing population – which, paradoxically, must be fed. A warmer climate will contaminate the Nile with salt water from the Mediterranean.
     As one strategy, Egypt is considering getting rid of its 6 million low-producing cows in exchange for one million Holsteins in order to ease pressures on water and land.
     El-Sherbiny’s dairy isn’t average for Egypt, where there are 1 million dairy farmers, but only 120 with milking parlors or more than 100 cows.  That shows the need for improving management around the globe. “How can we move 1 million farmers into the present? “ El-Sherbiny asked.

 The fallacy of the carbon sink

         Dairy can’t fall back on the defense that agriculture sequesters carbon, offsetting its GHG emissions, said Dutch researcher Theun Vellinga. Only grassland can be a true carbon sink, and that decreases as the sward ages. Meanwhile some soils, like peat, are releasing CO2, while grasslands plowed for crops also release more carbon. 

(More to come on IDF summit)

Reducing Dairy’s Carbon Footprint

U.S. dairy’s carbon footprint per pound of milk produced has shrunk nearly 70% in six decades. It will get even smaller in the years ahead.

By Mike Van Amburgh, Judith Capper and Dale Bauman

The dairy industry has made remarkable progress over the past 50 to 60 years in supplying adequate, safe and affordable dairy products to a growing and changing population. At the same time, the industry’s structure and geographical distribution has undergone huge changes. There is also an increased emphasis on “environmentally-friendly” food production.
A recent report from the United Nations’ Food and Agriculture Organization implicated livestock production as a global environmental threat, because of land erosion and production of greenhouse gases that contribute to global warming. Ruminant animals produce methane, carbon dioxide (CO2) and nitrous oxide, all of which have significant global warming potential (GWP).
It’s important to recognize that methane is 25 times more potent as a greenhouse gas than CO2; nitrous oxide is 298 times more potent. That means small amounts of each gas – methane and nitrous oxide – will still have significant impacts.

Giant strides
Given the media and public interest in the carbon footprint of various aspects of society, we examined the carbon footprint of dairy production as it has evolved during the past 60 years. This is an important exercise for the dairy industry, giving context to any GWP number. A snapshot of dairy production’s carbon footprint might unintentionally mislead a retailer or consumer, since few values exist for comparison.
A number of reports have been issued during the past several years, primarily from the United Kingdom and European Union, regarding the carbon footprint of various production strategies. In general, they showed an average value of 1.4 lbs. of CO2 equivalent per pound of milk produced. Many of these reports exclude the cow’s CO2 production, assuming that because cows are vegetarians and consume plant materials, their CO2 production is recaptured and recycled.

Fewer cows, more milk
Two of the biggest changes in the dairy industry since the mid-1940s have been the dramatic increase in the amount of milk produced per cow and the dramatic decrease in the number of cows required to produce a given amount of milk. Consider:
• In the mid-1940s, approximately 25 million cows averaged about 4,500 lbs. of milk per lactation. The U.S. population was 138 million people.
• Today, about 9 million cows produce approximately 20,000 lbs. of milk per lactation. The U.S. population is more than 300 million.
• That’s 2.2 times as many people, with 59% fewer cows.
What does this mean for the overall resources required to produce a given amount of milk? Our work shows that dairy production systems in 1944 required two-to-four times the amount of various resources and produced two-to-four times the amount of excreted nutrients and emissions compared to 2006. There were approximately 4.1 times as many cows producing milk for 57% fewer consumers. Those cows required 4.5 times as much land and produced 2.6 times more methane.
This is a significant change in resource allocation, and demonstrates the tremendous efficiency increase the dairy industry has made.

Bottom line footprint
In 1944, the calculated CO2 production was 10 lbs. per 1 lb. of milk. Compare that to 2006, when the calculated CO2 production was 3 lbs. per 1 lb. of milk, nearly a 70% decrease.
How have dairy producers achieved this reduction in the carbon footprint of dairy production? Most of it relates directly to all the things that have increased milk per cow: genetics and artificial insemination, forage quality, better nutrition, grouping strategies, improved heifer rearing and use of technologies such as recombinant bovine somatotropin and Rumensin. All these things have increased milk per cow and enabled production of more milk with fewer cows.
This is a remarkable achievement, but the dairy industry has opportunities to reduce its footprint even more through advances in nutritional strategies.

FYI
• Mike VanAmburgh is an associate professor, Judith Capper is a post-doctoral research associate and Dale Bauman is Liberty Hyde Bailey Professor in the Department of Animal Science at Cornell University.  Reach VanAmburgh via phone: 607-254-4910 or e-mail: mev1@cornell.edu. Contact Bauman via phone: 607-255-2262 or e-mail: deb6@cornell.edu.

Global warming study, lawsuits add to rbST debate

Those who thought the debate over recombinant bovine somatotropin (rbST) had cooled, it just got a little warmer. Make that hotter.
On June 30, the Proceedings of the National Academy of Sciences web site published a Cornell University study, “The Environmental Impact of Recombinant Bovine Somatotropin (rbST) use in Dairy Production,” which demonstrated that use of rbST reduces the carbon footprint of milk production.
The study’s authors include Cornell University professor Dale Bauman, post-doctoral research associates Jude Capper and Euridice Castandena-Gutierrez, and Monsanto scientist and Cornell alumnus Roger Cady. Citing a growing world population and increased food needs – combined with mitigating agriculture’s environmental impact – they said rbST markedly improved the efficiency of milk production while addressing “eutrophication and acidification, greenhouse gas emissions and fossil fuel use.” The most sustainable way to increase U.S. milk production is to improve production per cow, they wrote.
The study design included three models to predict the environmental impact of using rbST: one examining the impact of increased productive efficiency of individual cows in a producer’s herd; one examining industry-scale adoption of rbST-supplemented cows; and a third examining the environmental impact of achieving future increases in the future U.S. milk supply required to meet projected population growth and recently published USDA Dietary Guidelines using conventional, conventional with rbST, or organic production systems.
“The total reduction in the carbon footprint conferred by rbST supplementation of 1 million dairy cows is equivalent to removing approximately 400,000 family cars from the road, or planting 300 million trees,” they said. Further energy use reductions would result from decreases the energy needed from fossil fuels and electricity required for cropping and milk production.
The authors reported that 8% fewer cows are needed in an rbST-supplemented population, whereas organic production systems would require a 25% increase in cow numbers to meet future production targets.
For more information, including abstracts and summaries of the study, visit www.ansci.cornell.edu/bauman/envir_impact.

An article, authored by Cornell researchers Mike Van Amburgh, Judith Capper and Bauman – published in the June 2008 issue of Northeast DairyBusiness and July 2008 issue of Midwest DairyBusiness – said technologies that have helped boost milk production per cow reduced U.S. dairy’s carbon footprint per pound of milk produced nearly 70% in six decades. In 1944, the calculated carbon dioxide (CO2) equivalents was 10 lbs. per 1 lb. of milk produced. In 2006, the calculated CO2 production was 3 lbs. per 1 lb. of milk.

On the same day the Cornell study was published, the International Dairy Foods Association (IDFA) and Organic Trade Association (OTA) filed similar and simultaneous lawsuits against the State of Ohio over its dairy product labeling law. The suit, filed in the U.S. District Court, Southern District of Ohio, challenges regulations regarding the labeling of dairy products from cows that have not been supplemented with rbST. In the lawsuits, both OTA and IDFA said the Ohio rule interferes with the First Amendment right of its members to communicate truthful information to Ohioans, and with interstate commerce.
The complaint is the result of a dairy product labeling regulation that went into effect on May 22, with a 120-day implementation period.
Peggy Armstrong, IDFA communications director, said Ohio’s labeling regulation is cumbersome – especially for national and regional dairy manufacturers. She said the rule goes beyond the labeling guidance offered by the U.S. Food and Drug Administration (FDA), and is significantly different than most other states. As a result, dairy companies will have to create special labels just for Ohio, or be forced to drop information about rbST on package labels.
For more information, visit www.ota.com/news/breaking/ohiodairy.html or www.idfa.org.

The label debate didn’t end there. The American Farm Bureau Federation (AFBF) said it sent a letter to FDA, asking the agency to review guidance it issued in 1994 pertaining to milk and dairy products from cows not treated with rbST.
In the announcement, AFBF said all of the top U.S. grocery store chains restrict the sale of milk from cows supplemented with rBST. The milk – often labeled as “rbST-free” or “hormone-free,” typically sells at a premium compared to milk that is not labeled. As a result, AFBF told FDA, producers who sell to markets restricting the use of rbST are seeing lower production and profits during a time of record-high feed and fuel prices.

An organization born out of the rbST debate, the American Farmers for the Advancement and Conservation of Technology (AFACT), will hold a meeting, “The Power of Producer Advocacy: An AFACT Summit,” July 23-24, in Chicago. In addition, an “AFACT Advocate” training session is being planned in Pennsylvania, July 10. For more information, visit www.itisafact.org.

And finally, the American Farm Bureau’s quarterly “Marketbasket Survey” of retail milk prices found the average price for a half-gallon of regular whole milk, at $2.38, was down 2¢ from the first quarter of 2008. The average price for 1 gallon of regular whole milk was $3.88, up 7¢ from the previous quarter.
The average price for a half-gallon of “rbST-free” milk was $3.34, up 4¢ from the first quarter of 2008, and 96¢ higher (40%) than the current price for a half-gallon of regular milk. On a per hundredweight basis, the half gallon of “rbST-free” milk was marked up $24.00/cwt. compared to the regular milk, an increase of $1.50/cwt. from the previous quarter.
The average price for a half-gallon of organic milk was $3.67, up 4¢ compared to the previous quarter, and 50% more than a half-gallon of regular milk.

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