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♦ Revisiting the Benefits of 1/4 cc Straws
♦ Revisiting the Benefits of 1/4 cc Straws

Revisiting The Benefits of ¼ cc Straws

The ¼ cc straw has been utilized as the main storage device for cryopreserved semen on a world-wide basis for over 35 years. In fact, in an article written by Kaproth and Gilbert in the Dec. 2008 issue of Hoard's Dairyman, it was reported that 82 percent of all semen produced world-wide during that time was in ¼ cc packaging1.

It's been interesting to be involved with the Genex Cooperative, Inc., transition in semen package size for our dairy sire lineup, a change that took place almost three years ago. From that point on, all Genex dairy sires have had semen collected and stored in the ¼ cc package.

What Prompted the Change?
First, let's make clear the advantage the ¼ cc straw has over the ½ cc straw in terms of improved sperm livability during the freezing and rethawing process used today. With the surface area of the ¼ cc being much less, the ratio of volume (including sperm population) to surface area increases for the ¼ cc straw. This aids in creating a more uniform freezing and thawing opportunity for processed semen; and in the end, more viable, live sperm can be available at the time of semen deposit2,3.

To many in the U.S. artificial insemination (A.I.) industry, this change was significant. We had become ‘comfortable' with the ½ cc package which had been used for many years, and provided, in most opinions, acceptable performance. Back in 2008, many had experienced the ¼ cc straws with GenChoiceTM sexed semen, but the total usage was small compared to the ½ cc conventional straws used by most dairy herds.

Backed by Research
Genex announced the change to ¼ cc packaging after conducting two research studies. During both studies, a measurable difference in conception rates was realized when comparing the performance of the ¼ cc package to the ½ cc package (using the same ejaculate from a bull). The resulting conception benefit of the ¼ cc package was 1.6 percent better than the ½ cc package in the first study4.

A second study was initiated to confirm the performance results, partly because the purpose of the first study had not been to declare a difference in conception rates. This study involved a larger data set coming from a much wider range of herds and A.I. technicians. Again, there was a measurable advantage in the conception performance of the ¼ cc package. The ¼ cc package had a 2.1 percent conception advantage in the second study2.

These results influenced Genex to convert packaging of all dairy sire semen into the ¼ cc straw. This decision follows in the spirit of our mission statement, "To provide products and services as effectively as possible to maximize the profitability of members..."

Benefits for Producers
Let's focus on short-term savings realized from a two percent performance increase on conception. Using the Genex AchieveTM program, reproductive savings and expenses were analyzed for one year.

In the example below, a herd of 1000 cows and 400 replacement heifers was used. The average semen price was $8 per unit for cows and $10 per unit for heifers. The cow herd averaged a 13.1 calving interval, with a $2 value for each day open. Replacement heifers calved on average at 23.3 months, with a rearing cost of $2.36 per day ($70.80 per month).

Parameters included the following:


Current Situation

2% Increase in Conception


Cow Conception Rate




Heifer Conception Rate




Estimated services per conception: cows




Estimated services per conception: heifers




Total semen units per year




Total genetic Investment per year (G)




Ave. days open

130 Days

124 Days

(6 days)

Days open cost per year (D)




Heifers: birth/calving

9333.3 Months

9312 Months

(21 Months)

Heifer rearing costs (H)




Total Costs (G+D+H)




The savings in our example ($13,328.04) were only portion of the benefits. As shown above, the conception benefit impacted not only the cost of product purchased but also other factors of reproductive performance cited as indicated.

When looking at the use of ¼ cc straws as an investment, a $13,328.04 benefit of over 2,907 units was realized. For each ¼ cc straw used, an additional $4.58 in value was returned to the bottom line. Or, from the perspective of a Return on Investment (ROI), there is a return of $0.54 for each $1 spent on semen for the year - a very good return!

Important Handling Procedures
There are some important steps to remember when handling your genetic investment from the semen tank, regardless of package size. It's important to realize that all semen packaging types need to be handled in a way to ensure the maximum amount of live sperm are available over a period of time to improve the opportunity for fertilization. The basis for these points come from a recent set of procedures composed by Kristi Fiedler, Genex National Account Specialist Manager6:

• Do not allow the canister or cane to remain in the raised portion in the neck tube for more than 10 seconds. Genex packages ¼ cc straws in the bottom goblet to protect the semen during the removal process. If possible, position the semen tank so the user can look down into the neck tube. 

Use a tweezers to handle semen straws both when removing straws from the tank and from the warm water bath. Raise the canister and semen straws in the neck to the top of the frost line only.

• Thaw straws in a warm water bath for a minimum of 40 seconds at 90-95oF. Or, if using the Pocket ThawTM  method, place the straw in a paper towel for two to three minutes in your shirt pocket.

• Prevent direct straw to straw contact during pocket thaw or water thaw.

• Ensure the water temperature is maintained at a consistent temperature between 90-95oF while thawing the straw in the water bath.

• Position yourself, the tank and your equipment to best prevent exposure from direct sunlight, windy conditions and moisture.

These ‘at the tank' procedures are designed to aid in providing dairy producers a reproductive tool with the ability to provide a consistent, high fertility product. If you or your reproductive team have questions, don't hesitate to discuss these with Genex personnel. All Genex staff are trained in the correct use of the ¼ cc straw.

Other Important Factors
Factors such as animal health, adequate nutrition, cowside management, heat detection, A.I. technique, a sound management plan for achieving reproductive goals, and a commitment to excel all influence the ability of the dairy producer to benefit from a sound reproductive program.

Genex and other organizations are constantly looking for new methods, products or procedures that will benefit the dairy producers we serve. Product enhancement through the change to the ¼ cc straw is one example of Genex's commitment to member success.



Kaproth M., Gilbert, G. There's more to the 1/4cc straw story. Hoard's Dairyman. Dec. 2008, p. 776.
G. Gilbert (personal communication). January 8, 2011.
O'Connor M.L. Consideration for storing and handling frozen semen. Dairy Integrated Reproductive Management. Penn State Univ., IRM-11, p. 1-3.
Kaproth M.T., Rycroft H.E., Gilbert G.R., Abdel-Azim G., Putnam B.F., Schnell S.A., Everett R.W., Parks J.E. Effect of semen thaw method on conception rate in four large commercial dairy heifer herds. Theriogenology 2005; (63): 2535-49
Achieve- Genex Cooperative, Inc., Program.
Fiedler (personal communication). January 4, 2011

 March 2011