Illini DairyNet Papers
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- Average days open for the top, middle and bottom third of Illinois dairy herds on DHIA in September 2000 were 172, 186 and 204 days, respectively.
- At a cost of $2.00 per day open after 115 days in milk, this amounts to annual losses per cow of $115, $136, and $179, respectively.
- Average pregnancy rates for Illinois DHIA dairy farms ranged from 14 to 17 percent.
- Breeding programs using reproductive hormones along with intensified heat detection or timed insemination have the most economic benefit when used in the first heat cycles after the voluntary waiting period.
The reproductive status of a dairy herd has a large impact on the productivity and profitability of that operation. Reproductive inefficiency results in excessively long lactations where milk production steadily declines or prolonged periods where no milk is produced at all (long dry periods). Both are costly to the dairy producer, but a long-term effect may be inadequate numbers of replacement heifers to maintain stable herd size. Purchased replacements increase the risk that new diseases will be introduced on the dairy operation, which may have even greater and more lasting impact on the productivity and profitability. This paper will explore some of the economic efficiencies that can be gained by following sound reproductive health programs.
Monitoring dairy herd reproductive programs involves analysis of herd-average parameters such as days in milk, days to first breeding, days open, length of the dry period, calving interval and age at first calving. DHIA parameters for Holstein herd herds in Illinois of September 2000 are shown below. The data was averaged for the bottom, middle and top third of herds based on rolling herd average milk production. Assuming most herds used a voluntary waiting period (VWP) of 60 days and that the cost of each day open after 115 days was $2.00, calculations for the average losses per cow were made.
|Parameter||< 18,000||18,001-22,000||> 22,000|
|Number of Cows||69||86||95|
|Age at 1st Calving||27.2||26.7||26.3|
|Average Days Open||204||186||172|
|Avg. Days to 1st Service||81||91||93|
|Services per Conception||5.00||3.23||2.86|
|Average Loss per Herd||$12,339||$12,428||$10,915|
|Average Loss per Cow||$179||$136||$115|
The economic impact of reproductive inefficiency on Illinois dairy operations was greater in the lower producing herds than the highest one third of herds. Annual losses for reproductive inefficiency were $179, $136 and $115 per cow for the lower third, middle third and top third of Illinois dairy herds, respectively. Across all herds, total herd economic losses, on average, ranged from $10,915 to $12,428 per year. With breakeven milk prices, lower producing herds can ill afford inefficient reproduction. For short periods of time, higher producing herds can offset some of the loss with more cost efficient milk production.
Reproductive failure accounts for 20-25% of the reason dairy cows are marketed for beef. Abortions may contribute to this figure, yet on average, less than 3% of cows abort each year (NAHMS Dairy 96). Infertility precludes the option of removing animals from the herd because they are inefficient milk producers. Not all cows are sold because they are infertile. Many cows simply have not been offered an adequate opportunity to express they ability to reproduce. Successful reproduction is a combination of the length of the voluntary waiting period (VWP), the proportion of cows bred due to detected heat or timed insemination (service rate), and the proportion of cows that conceive and carry a calf to term (conception rate). The pregnancy rate can then be defined as the proportion of cows presented for breeding that conceive (service rate times the conception rate).
Service rate, conception rate and pregnancy rate each have physiological and management factors that influence the rate. Changing physiological factors can prove difficult, while management factors can be altered by development of a consistent management program for regulating reproduction. Often, separating the physiological and management factors in an on-farm situation is difficult.
Using systems like HeatWatch, researchers have been able to determine duration and activity of standing heats in dairy cattle (Nebel, JDS 1997). On average, virgin Holstein heifers will exhibit standing heat for 11 hours with 18 mounting events while cows may only show standing heat for 7 hours and 7 mounts. Jersey cattle showed more activity with heifers standing for 14 hours and 30 mounts and cows standing for 8 hours and 10 mounts. The difference in duration of estrus between heifers and lactating cows is probably primarily due to physiological factors but has important management implications. Lactating dairy cows would require at least three attempts at heat detections per day to notice most of the cows during each estrous cycle. In contrast, heat detection could be at about 12 hour intervals in heifers. Traditionally, to be presented for service by artificial insemination, a cow or heifer must be detected "in heat." Factors that cause variation in service rate are numerous such as: number of heat detections during each day, timing and duration of heat detection, surface used for heat detection, individual doing heat detection, use of heat detection aids, and use of synchronization procedures.
Service rate can be increased in many ways. The first and most obvious is to increase the amount of time and the quality of the time spent in heat detection. Short but intensive heat detection at multiple times during the day is better than attempting a long time period once or twice per day. To approach 90% service rate with heat detection alone would probably require four, 15-20 minute heat detections per day at evenly spaced intervals. In addition, the time of day, activity of cows (feeding, milking etc.), and location of heat detection (slippery cement vs. pasture) can have substantial effects on the quality of heat detection.
There are numerous other aids to improve detection of heat. Heat mount detectors, paint, or chalk can be placed on the tail-head of selected cows to monitor mounting behavior. The tail-head must be checked at least daily to provide efficiency with these techniques. Tail-head chalk should be reapplied on a daily basis. Androgenized cows can be used within the herd to aid this approach.
Conception rate is affected by many factors that interact in a complex manner. Cow fertility is any factors within the cow that may alter her ability to become pregnant, including heat stress, nutritional deficiencies, infection, disease, etc. Bull fertility is related to the fertility of the semen that is used for AI. The accuracy of heat detection refers only to whether a cow was in actual heat (near the time of ovulation) and not to service rate or efficiency of heat detection. The AI efficiency refers to any aspect of the AI technique that may alter pregnancy rates such as thawing technique, semen placement, etc. On many farms bull fertility and AI efficiency are optimized with accurate heat detection. The problem is sub-par cow fertility. The cause of this low fertility is unknown, but it continues to be low even on well-managed farms with excellent nutrition and sound management programs.
Reproductive management programs using prostaglandins (PG) have been used on dairy farms throughout the world with good success. These programs increase service rate in three ways. First, the producer has an idea when to expect cows to be in heat and can watch intensively for these heats. Second, there can be a greater number of cows in heat or close to heat if several cows are given PG injections. This increases sexual activity and improves detection of heats. Third, cows will come into heat earlier than normal because PG will shorten the estrus cycle.
If PG injections are given at 7-8 days after the previous ovulation, nearly 100% of the cows will come into heat within 2-3 days after the injection. If PG shots are administered 10 days after a previous ovulation, subsequent heats will occur from 2-7 days after injection. Below is a PG program outlined by Dr. Milo Wiltbank of UW Madison. In one study, 82% of cows were serviced after the first two injections (46% after the first, 33% more after the second) and conception rates were 46% at each breeding period. The remaining 18% of the cows were insemination after 80 hours and only 4% of those cows conceived.
Difficulties have been reported with PG programs. First, heat detection is still required because timed insemination after PG has led to reduced pregnancy rates. In lactating dairy cows, timed AI decreases conception rates by 50% of normal. Second, PG does not appear to induce heat cycles in non-cycling cows. Anestrus should not be confused with lack of heat detection. On most dairy farms non-cycling cows are probably less than 10% of the total cows; however, in some situations a much greater proportion of cows be anestrus during the first 80 days of lactation. Third, cystic cows will not be effectively treated with PG treatment alone.
The Ovsynch protocol requires three injections as shown below. Use of these drugs must be done under the direction of a veterinarian since they are "extra-label use." GnRH is administered followed in seven days by a dose of PG. After the second injection of GnRH the cows are bred without regard to estrous behavior. In several studies, the conception rate with Ovsynch has been similar with cows that bred to a normal estrus. This program only synchronizes ovulation in about 70% of heifers as compared to about 90% synchronization of lactating dairy cows. Thus, this new protocol allows more effective management of reproduction in lactating dairy cows because cows can be bred at the correct time without continuous detection of estrus.
The service rate is dramatically improved after using this program. The primary disadvantage of Ovsynch is the cost of the hormones and labor to administer them. Improvements in reproductive efficiency most likely offset the increased costs, but each dairy should evaluate the economics independently. A second disadvantage is that the Ovsynch program only allows a normal conception rate and therefore there needs to be an effective method for detecting non-pregnant cows after Ovsynch. The most practical method is probably an intensive heat detection program at 18-25 days after the Ovsynch program using heat detection aid. Some veterinarians are becoming proficient with ultrasound to detect early pregnancies. Cows can then be re-enrolled in a program earlier than they would be otherwise.
The Ovsynch program removes the problem of cows not showing heat during times of low fertility. During hot summer months most cows will not show strong heat and therefore not be bred during this time of low fertility. With the Ovsynch program, many cows will continue to be bred during the summer even though heat stress will continue to cause early pregnancy losses. Therefore, careful attention must be paid to cow fertility with the Ovsynch program as with any reproductive management program.
The Ovsynch program has been successfully used on many dairy farms around the country in the last two years. Service rate can be dramatically increased resulting in improvements in pregnancy rates and overall reproductive efficiency. Interestingly, the Ovsynch program appears to be effective in non-cycling and cystic cows. This program was not designed for heifers and does not effectively synchronize ovulation in heifers.
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