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THURSDAY, AUG. 20, 2009 | VOL. 3, ISSUE 4

ANNUAL CONVENTION

Now's the time to register for the 2009 Regional Meetings. Learn more.

In this issue:

Fertility: The fundamental element of reproduction
Culling dairy cattle for reproduction
Reproductive statistics are improving on U.S. dairies
Shortened dry periods may improve reproductive performance
Heifer rearing influences fertility later in life
Welfare, behavior and disease
Reproductive ultrasonography
Pregnancy rates increase with five-day cosynch program and two doses of prostaglandins

WHAT'S NEW IN REPRODUCTION

Fertility: The fundamental element of reproduction
Fertility is the cause of many reproductive challenges producers face today. While fertility has begun to improve, it remains top-of-mind as producers continue to work toward improved herd reproduction. Learn how genetics, breeding and new technology all influence fertility and can help make improvements on the dairy. Read more.

Culling dairy cattle for reproduction: Considerations for dairy producers
Deciding whether to keep and treat, or cull a cow is one of the toughest decisions dairy producers must make. Studies show that 26.7 percent of dairy cattle are culled for reproductive issues, making it the most prevalent reason. This article presents the main considerations dairy producers should take into account when deciding to cull cows for reproductive reasons. Read more.

DCRC RESEARCH SHORTS

Reproductive statistics are improving on U.S. dairies
That's what new research using data from the USDA National Dairy Database is showing. Since 1995, the database has collected a multitude of reproductive statistics on Holstein and Jersey herds throughout the United States. This information allows trends to be seen over time relating to reproductive performance.
The following parameters have been measured over nearly 200 million breedings in more than eight million lactations of more than five million cows in 23,000 herds:

Days to first breeding after calving
70-day nonreturn rate
Conception rate
Number of breedings per lactation
Interval between first and last breeding during the lactation
Days to last breeding after calving
Pregnancy Rate
Calving interval
Interval between consecutive breedings

Research published in the July 2009 Journal of Dairy Science compared reproductive figures today with those from 10 years ago. A few statistics to highlight include:

Days to first breeding declined from 92 days to 85 days in Holsteins from 1996 to 2007.
First- and all-breeding 70-day nonreturn rate declined five to nine percentage units.
The number of breedings increased slightly over time but remained constant across parities for Holsteins; this figure increased for Jerseys.
Average pregnancy rate was highest in the Southwest at 28.3 percent; the lowest was in the Midwest and Southeast at 22.2 percent.

Researchers concluded the use of Timed Artificial Insemination has reduced days to first breeding, lowered conception rate and increased the number of breedings while reducing days to last breeding and calving interval. Since 2002, performance in multiple reproductive areas has improved, reversing the historical decline.
Click here to read more.

Shortened dry period may improve reproductive performance
To study the effects of dry period length on reproduction, researchers at the University of Wisconsin-Madison randomly assigned 781 cows into one of two treatments:

A traditional dry period of 55 days
A shortened dry period of 34 days

Throughout the trial all cows were fed the same diets. Actual days dry were 34 and 56 for the short and traditional dry periods, respectively. Results were reported in the July 2009 Journal of Dairy Science.
    At 70 days in milk, twice as many cows from the traditional dry period group were anovular compared to the short dry period group. Cows were bred when standing estrus was observed starting at 45 days in milk; the percent of cows confirmed pregnant by 70 days in milk tended to be greater for the short dry period group.
    Pregnancy rates in younger cows were similar across treatments. However, 30.3 percent of older cows in the short dry period group were pregnant compared to 10.6 percent in the standard dry period group. Average days open tended to be fewer in the short dry period group than the traditional dry period group.
    Researchers concluded shortening the dry period appeared to increase reproductive performance in older cows by shortening time to first ovulation, reducing the number of anovular cows in the group and improving fertility. Learn more about the study.

Heifer rearing influences fertility later in life
A recent study conducted by researchers at Royal Veterinary College in the United Kingdom investigated the effects of growth and metabolic indices during rearing on fertility. Heifers from 17 United Kingdom farms — representing a total of 428 animals — were involved in the study. Animals were measured at 30, 180 and 450 days of age for weight, height and girth, as well as metabolic indices including insulin-like growth factor-1 (IGF-1), insulin, glucose and urea.
    Fertility data collected included age at first breeding, number of services per conception, pregnancy rate and age at first calving.
    Researchers found the following in the study:

Average pregnancy rate to first A.I. was 67 percent.
Average age at first breeding was 473 days; average age at first calving was 791 days.
Body weight, girth, IGF-1 and skeletal growth increase were all associated with earlier age at first breeding.
Increased glucose concentrations at 180 days of age were associated with earlier age at first breeding.
No association between insulin and urea concentrations and fertility traits was identified.

Researchers concluded suboptimal growth associated with increased age at first calving can be improved through more intense heifer management during rearing.
Access the complete study by clicking here.

HIGHLIGHTS FROM DCRC 2008

Welfare, behavior and disease
Concerns about animal welfare can be roughly divided into three categories:

Biological functioning of the animal, such as its health or productivity.
How the animal is feeling, such as the amount of pain an animal feels.
The ability of the animal to live a natural life.

Many consumers are more concerned with the emotions of the animal, and focus upon whether an animal feels pain, fear or hunger. For other consumer groups, a key concern is whether the animal is able to live a relatively natural life.
    Dr. Wolfgang Heuwieser with The University of British Columbia notes that poor welfare isn't just a consumer issue — it can also lead to poor reproductive performance. For example, an over-crowded maternity pen with wet and poorly maintained bedding can increase the prevalence of acute metritis and endometritis, negatively influencing reproductive performance. In these circumstances, the observed increase in vaginal discharge and/or fever can be seen as an indicator of reduced welfare, but also negatively impact reproduction and milk production.
    The health status of the transition cow is a major welfare issue for dairy operations. While the discipline of animal behavior relating to reproductive health has been under-researched, we do know changes in behavior help identify animals at risk for disease. The increased availability of electronic technologies will enable future research efforts to focus on cowside tests to shorten diagnosis time.
     Consumer perceptions regarding hormone use will likely play a significant role in determining future dairy management practices. For example, more dairies are using A.I. protocols to get cows bred. The potential impact of consumer perceptions cannot be underestimated and may result in the industry finding alternative methodologies to maintain reproductive success.

Reproductive ultrasonography
Dr. Kevin McSweeney of Bovine Reproductive Specialists LLC, says everything we currently know about reproduction needs to be reconsidered in order for new strategies in reproductive management to pay big returns. Ultrasound, for example, is a tool available to dairy practitioners to improve herd reproduction. Incorporating ultrasound into timed A.I. programs requires a different mindset for managing cows.
    Conception rates vary greatly depending upon when synchronization programs are started in relation to the cow's estrous cycle. Research on Colorado dairies found a large percentage of cows at first service or diagnosed open were not within an optimal five to 12 day window to start synchronization programs. When these cows were enrolled in a synchronization program, conception rates were extremely low. A large percentage of these cows are acyclic, cystic, contain dead fetuses or have pyometras, which makes them poor candidates for enrollment in a synchronization program.
    An advantage ultrasound has over rectal palpation is being able to completely assess ovarian structures and better predict when cows fall into the optimum period to initiate or continue in synchronization programs (Sprecher et al., 1989). Most important in predicting the stage of a cow's estrous cycle is identifying the presence of an active corpus luteum. Ultrasound has been found to be far superior in predicting an active corpus luteum and high progesterone level.
    By using ultrasound, cows can be assessed properly and synchronization programs can be modified when cows fail to respond to the first dose of GnRH. Combining ultrasound with a synchronization program can be a powerful management tool to maximize estrous detection and conception rates, resulting in improved pregnancy rates.

To access the 2008 DCRC meeting proceedings, click here.

RESEARCH FROM OUR SPONSORS

Study shows that pregnancy rates increase with five-day cosynch program and two doses of prostaglandins
New research from the University of Florida and the University of California reinforces the concept that reducing follicle dominance in timed A.I. protocols improves pregnancy rates (PR) in dairy cows¹. Treatment with PGF on days 5 and 6 after GnRH resulted in high luteolysis and allowed for reducing the interval from GnRH to timed AI, which increased PR.

Study Design Experiment 1

164 Holstein cows were randomly assigned to 7d-Cosynch 72h (CoS72), 5d-Cosynch 72h (5dCoS1) with one dose of PGF or 5d-Cosynch 72h (5dCoS2) with 2 doses of PGF 24 hours apart (d 61 GnRH, d 66 and 67 PGF, d 69 GnRH + timed A.I.).
Blood was sampled at the first GnRH, first PGF, and at timed A.I. and assayed for progesterone (P4).
Ultrasound of the ovaries was performed to determine ovulatory responses to treatments.

Study Design Experiment 2

933 cows were randomly assigned to either CoS72 or 5dCoS2.
Blood was sampled at the first GnRH, first PGF, and at timed A.I. and assayed for progesterone (P4).
Ultrasound of the ovaries was performed to determine ovulatory responses to treatments.
Pregnancy was diagnosed on d 38 and 66 after timed A.I.

Experiment 1 Results
		Pregnancy Rate (%)
	7-day, 72-hour cosynch	5 day, 72-hour cosynch with 1 dose of PGF	5-day, 72-hour cosync with 2 doses of PGF
CL Regression	78%2	58.7%	95.8%

Experiment 2 Results
	Pregnancy Rate (%)
	7-day, 72-hour cosynch	5-day, 72-hour cosynch with 2 doses of PGF
% cows estrus detected @ TAI	30.9%	23.6%
PR for all cows	31.1%	37.7%
PR for cows that responded to PGF	34.2%	40.1%

Pregnancy rates of cows that showed estrus at timed artificial insemination (TAI) was much greater than cows that did not with rates of 46.0 and 31.9 percent, respectively.

Conclusions
Two treatments of PGF on days 5 and 6 after GnRH resulted in much higher CL regression. Even though a much higher percentage of cows showed estrus at TAI in the CoS72 group, it did not result in more cows getting pregnant. Across all cows, those that showed estrus at TAI had much higher PRs than those that did not show estrus at TAI. Reducing the interval between the first GnRH and PGF reduced follicle age and dominance results in higher pregnancy rates.

Chebel RC, Rivera F, Narciso C, Thatcher WW, Santos JEP. Effect of reducing the period of follicle dominance in a timed A.I. protocol on reproduction of dairy cows. J Anim Sci Vol. 86, E-Suppl. 2/J Dairy Sci Vol. 91, E-Suppl. 1

(This research was brought to you by Intervet/Schering-Plough Animal Health.)

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