Newsletter – 2014 – September

Double Reproductive Trouble
Anovulation and endometritis often go hand-in-hand, and both conditions negatively impact reproductive performance. Researchers at the University of Florida recently explored the individual and combined effects of these costly issues. The results were published in the September Issue of the Journal of Dairy Science.

To do so, the researchers analyzed data from 1,569 cows in three different regions of the United States. Unsurprisingly they found that both anovulation and endometritis had a negative effect on time to pregnancy, and the negative effect was compounded if both conditions were present.

In fact, anovular cows with endometritis had median days open of 200 while healthy cows in the study had median days open of 121. Pregnancy rates were impacted. Cows that were anovular and diagnosed with endometritis had a significantly lower pregnancy rate than healthy cows.

In summary, both anovulation and endometritis negatively affect reproductive performance—when combined, they have an additive negative effect.

Access the abstract.

Are Small Calves More Prone to Problems?
Here’s another reason to make sure first-lactation heifers calve on time—not too early and not too late—and that mature cows have uneventful pregnancies. European researchers recently learned that poor prenatal growth resulting in small size at birth increases predisposition to metabolic diseases during later life.

The objective of the present study was to determine factors that are associated with birth size of Holstein calves. Results were published in the September Issue of the Journal of Dairy Science.

In addition to the recognized factors (calf sex, season of calving, gestation length, parity, length of the dry period and shape of the dam), the researchers discovered that age at calving in heifers and level of milk production during gestation in cows are significant factors that affect calf size at birth. This information may provide a basis for developing management interventions to improve long-term health and productivity of offspring.

Access the abstract.

Climate Affects Embryo Program Efficiency
A recent study in Brazil explored how climate variation and donor animal age impact the efficiency of embryo programs, as well as embryo survival following the transfer to recipient cows. The research was published in the July 15 issue of Theriogenology.

The research evaluated 1,562 multiple ovulation procedures (609 cows and 953 heifers) and 4,076 embryo transfers performed in two dairy herds.

Results showed:

• Donor cows had a greater number of corpus luteum and ova/embryos recovered compared with donor heifers.
• The fertilization rate and proportion of transferable embryos were lower in donor cows than heifers.
• Regardless of donor category, the proportion of freezable embryos was less during the hot season than in the cooler season (21.4% vs. 32.8%).
• Greater decline in the proportion of freezable embryos during the hot season was observed in cows (21.7% vs. 10.7%) compared with heifers (46.2% vs. 38.1%).

In contrast, the season during which the embryo was produced (hot or cool) did not affect pregnancy rate. Regardless of when the embryos were produced, embryonic survival after transferring embryos retrieved from donor cows was greater when compared with embryos from donor heifers.

The researchers conclude that embryo production efficiency decreased during the hot seasons both in cows and heifers; however, the decline was more pronounced in donor cows. Regardless of the embryo source, similar pregnancy rate was observed in the recipient, no matter the season. In addition, embryos originating from donor cows had higher embryonic survival when transferred to recipient cows than embryos originating from heifers.

Access the abstract.

What’s the Financial Impact of Improving Your Dairy’s Pregnancy Rate?
By Albert De Vries University of Florida Extension Dairy Economics Specialist

A myriad of choices exist when it comes to evaluating your dairy’s reproductive performance. You can track days to first service, days to conception, calving interval, services per conception, conception rate, estrus detection rate and pregnancy rate.

There are reasons for monitoring each of these parameters, but for on-farm purposes, pregnancy rate is a good overall measure of reproductive performance. As a result, it has become the reproductive focal point on most operations.

Pregnancy rate is calculated as the number of cows that got pregnant divided by the number of cows that were eligible to get pregnant. In other words, it is a measure of the speed at which cows get pregnant after the voluntary waiting period (VWP).

For example:
If 25 cows were confirmed pregnant out of 100 cows that were eligible to become pregnant over a 21-day period, the pregnancy rate is 25% (25 divided by 100 X 100 = 25%).

Economic Influence (And Caveats)
Realistic economic benefits of improved reproductive performance—i.e., higher pregnancy rates—are not simple to estimate. When reproductive performance improves, all changes in cash flows that result from the improvement must be accounted for in your examination.

For a good analysis, you need at least realistic estimates of lactation curves, feed intake, the risk of involuntary culling and prices—such as the cost for milk, feed, labor, semen, synchronization tools, calves, replacement heifers and cull cows.

One must also keep in mind that cows that become pregnant faster will spend on average more time in the early part of the lactation (higher milk sales) and are less at risk to be culled for reproductive failure. But these animals also have a higher percentage of dry period time per lactation and more often are at risk for involuntary culling due to fresh cow problems due to more frequent transition periods (because they calve more often).

This point does not assume longer dry periods per lactation but per unit of time, the percentage of time spent in the dry period increases with better reproduction. Initially this may seem counterintuitive, but the following case study explains why this is actually a more desirable outcome.

For example, if a cow becomes pregnant two months after calving, and has a two-month dry period the lactation looks like this: 2 + 9 – 2 = 9 months milking, with two months dry. The calving interval is 11 months, meaning she is dry 2/11 or 18% of the time.

If that same cow got pregnant five months after calving (because of poor reproductive performance) then her lactation is 5 + 9 – 2 = 12 months milking and two months dry. The calving interval is 14 months. She is dry 2/14 or 14% of the time.

Per unit of time, better reproduction resulting in shorter days open results in more calvings and cows going through the transition period more often. On the other hand, cows with longer days open have greater risks of culling around the time they calve again.

Furthermore, a farm’s voluntary culling policy (how long to keep breeding open cows) can have a significant economic effect. The performance of replacement heifers should be included in the analysis.

For these reasons, researchers have built and used computer programs and spreadsheets to integrate the effects of all these different factors and come up with the best possible economic estimates of improved reproductive performance.

Still, the economic estimates of improved reproductive performance from these studies differ due to variations in prices, lactation curves and feed intake, the risk of involuntary culling, insemination and voluntary culling policy, and method of calculation.

Model Results
Repeated results from a number of studies show that the economic value of a slight increase in pregnancy rate becomes smaller when pregnancy rates are higher.

Computer model simulations of four scenarios at the University of Florida observe these results.

The default situation assumed a number of factors, including: milk price of $16 per hundredweight (cwt.), a calf price of $112.5, cull price of $0.36 per pounds of body weight and a heifer price of $1,400. Bodyweight and feed intake were taken from the 2001 NRC recommendations. Lactation curves were estimated from Florida and Georgia DHIA data for first, second and later lactation cows. The default situation also assumed visual estrus detection with a 40% estrus detection rate and a 40% conception rate, resulting in a 16% pregnancy rate for all cows. Labor cost for open cows eligible to be bred was set at $18.24 per cow per month, based on 0.6 minutes visual estrus detection per cow per day and a $10 per hour labor cost. Direct cost per insemination was $10.83, including semen and labor. Open cows were eligible to be bred up to 456 days in milk if not involuntary or voluntary culled earlier in lactation. Voluntary waiting period was 60 days. The length of the dry period was two months.

The effects of changes in pregnancy rates were evaluated for four situations:

1. Default inputs: milk price $16 per cwt., do not breed (DNB) > 456 days open, and a default lactation curve persistency -0.07 lbs/day.
2. Lower milk price: milk price $14 per cwt.
3. No breeding later in lactation: DNB > 213 days open (7 months in milk).
4. Less persistent lactation curves: -0.14 lbs / day

Results showed that the highest value at a change in pregnancy rate from 11% to 12% is approximately $20 for the situations with the lower persistent lactation curves and do-not-breed open cows after 213 days.

The increase is then most valuable because additional days open are very costly in these situations: Cows later in milk produce increasingly less milk and open cows have less chance to get pregnant before 213 days in milk are reached. Both lead to increased culling of open cows and thus higher replacement costs.

The simulations offer additional lessons.

As expected, higher pregnancy rates lead to lower average days to conception. At a 9% pregnancy rate, the differences in average days to conception between the four situations are the largest. The two situations that were least favorable later in lactation (lower persistency and DNB > 213 days open) resulted in the lowest days to conception (144 and 123 days, respectively).

This looks good but it is not. The reason is that open cows in these situations will not remain in the herd late in lactation—they will get culled—whereas in the other situations more open cows still can get pregnant later in lactation and thus add to a higher average days to conception.

In general, in the scenarios outlined previously, days to conception decreased when the pregnancy rate increases. Average days to conception at are greater than 30% pregnancy rate are very similar for all four situations because most cows get pregnant quickly after the VWP, regardless of a lower persistent lactation curve or less breeding opportunity later in lactation.

In addition, consider that milk price and feed price should be taken into account together; it is income over feed cost (IOFC) that matters, not milk price. Current IOFC is probably better than what was considered in these simulations. That means that improving reproduction is even more valuable given the today’s economic situation.

Ultimately, the improved reproductive performance’s economic impact depends on a number of factors and is unique to each dairy’s situation. However, it’s indisputable that the most significant influence occurs when you begin with lower initial performance.

It is extremely helpful for dairies to tap into the computer models available and input their individual data to see where they can make the most significant improvements—from efficiency and economic perspectives—as they analyze the effectiveness of their reproductive programs and where potential changes should occur.

Dr. BJ Jones
Center Hill Veterinary Clinic
Darlington, Wisconsin
Member since 2009

I grew up on a diversified livestock farm in Southeastern Wisconsin. I have a bachelor’s degree in meat and animal science from the University of Wisconsin, a master’s in dairy cattle breeding/statistics from the University of Minnesota and a DVM from the University of Wisconsin.

Though we provide a full range of veterinary services, my main focus is dairy reproduction. I provide reproductive ultrasound services at weekly and biweekly intervals. My primary goals are early pregnancy detection, twin identification and fetal sexing. I have recently added embryo transfer services to the offering.

The Center Hill Veterinary Clinic is a full-service, mixed-animal practice in Darlington, Wisconsin. We have three large-animal veterinarians and one small animal veterinarian. Our primary focus includes reproductive ultrasound, fresh pen management and young stock development. We work with a wide variety of producers—from small Amish herds to modern facilities up to 2,500 cows.

Interest in Dairy Reproduction
A main focus on our dairies is to continually improve our pregnancy rates. Our goal is to increase the number of replacements to drive sustainability. Reproduction is the foundation for economic profitability.

I joined the Dairy Cattle Reproduction Council (DCRC) to improve my knowledge and skills. I feel DCRC has helped keep me on the cutting edge of new technology.

I believe two key challenges face the industry today:

• Managing the transition cow to optimize first-service pregnancy rates.
• Developing strategies to minimize pregnancy loss.

Lessons Learned?
I think DCRC has done a great job helping me sort through and optimize all the synchronization protocols available today.

The meetings have been invaluable to understand the physiology behind the protocols. The DCRC website also has practical protocol summaries that help me explain them to producers.

I also have enjoyed all the transition cow presentations at the meetings. They are pivotal in helping me increase my knowledge of new transition cow practices and products and the practical impact of fresh cow health on future reproductive performance.

• Ohio State University Farm Science Review, Sept. 16 — 18, London, Ohio.
• 75th Annual Minnesota Nutrition Conference, Sept. 17 — 18, Prior Lake, Minnesota
• American Association of Bovine Practitioners Annual Conference, Sept. 18 — 20, Albuquerque, New Mexico
• World Dairy Expo, Sept. 30 — Oct. 4, Madison, Wisconsin
• Southwest Dairy Day, Oct. 8, Friona, Texas.
• Pacific Northwest Animal Nutrition Conference, Oct. 8 — 9, Vancouver, British Columbia
• U.S. Animal Health Association 118th Annual Meeting, Oct. 16 — 22, Kansas City
• 76th Annual Cornell Nutrition Conference, Oct. 21 — 23, Syracuse, N.Y.
• IDF World Dairy Summit, Oct. 27 — 31, Tel Aviv, Israel
• Dairy Practices Council Annual Conference, Nov. 5 — 7, Kansas City, Mo.
• Pennsylvania Dairy Cattle Nutrition Workshop, Nov. 12 — 13, Grantville, Pa.
• 2014 DCRC Annual Meeting, November 13 — 14, Salt Lake City, Utah