A stillborn calf is not just a calf born dead; it’s calf that is either born dead or dies within the first 24 to 48 hours after birth. In the dairy industry it’s estimated that 7–10% of calves are born dead or die within that time frame. As expected, first-lactation heifer stillbirth rates are higher (11–15%) than mul-tiparous cows (5.7%), and some herds can even approach a 20% stillbirth rate. The National Animal Health Monitoring System Dairy Study 2007 indicates that of the calves born during 2006, 93.5% were alive at 48 hours, while 6.5% were either born dead or died prior to 48 hours of age. Almost one in five calves (17.2%) needed assistance during delivery.
Most dairies realize the value of a live heifer calf and the cost of having to buy replacement heifers. “Some, however, seem to view stillbirths as a ‘given’ and don’t address a tremendous opportunity to improve,” says Sheila McGuirk, DVM, PhD, University of Wisconsin. Achievable goals, McGuirk says, are to reduce the herd stillbirth rate to less than 8%. A critical part of achieving that goal is keeping first-lactation stillbirths below 10%.
The most important factors associated with stillbirths are dystocia and calving assistance. “First-calf heifers are more likely to require (or receive) calving assistance than second- or greater-lactation cat-tle, especially with bull calves,” McGuirk explains.
Increased body condition of first-calf heifers also carries a higher risk factor for stillbirths. “Heifers that calf for the first time at less than 22 months or over 26 months of age are at higher risk of having stillborn calves,” McGuirk says. “Presumably, it is the small stature of the less-than-22-month-old heifers and over-conditioning of the older heifers, but small, over-conditioned heifers can be in either age category.”
The relationship of stillbirths with dystocia, calving assistance, calving season, percentage of first-lactation animals in the herd, gestation length (293 days-carrying-calf) and high body condition score provides an opportunity for record review, prospective data collection like heifer growth charts to pinpoint specific herd factors, nutritional consultation, calving assistance guidelines, worker training and sire selection based on genetic ability to produce live calves to remedy the problem.
Dystocia and/or calving assistance rise to the top of the list of risks for stillbirths. On some farms, the assistance is disproportionate to the level of dystocia or the actual need for assistance, so McGuirk likes to analyze both risk factors separately. “The greater the percentage of first-lactation cows in the herd, the higher the stillbirth rate,” she says. “Body condition score ranks high as a risk factor. Our goal is to have fewer than 5% of calving cows >3.5 body condition score, with an average BCS of 3.0.” Gestation length is also an important factor. Stillbirth rates go up with short and long gestation rates. “Less than 275 and more than 289 days-carrying-calf are a problem.”
Keep detailed records
Good calving records can pinpoint problems to the appropriate lactation group and can tell whether the problem is dystocias, percent of bull calves, percent of first-lactation heifers or days-carrying-calf. “You can tell whether the twinning rate is 5% or less, like usual, or higher, which increases the risk,” McGuirk says. “Body condition scores of the close-up heifers and cows can be used to solve nutrition problems. If records aren’t there, they need to be put in place.”
Even without necropsies, recording whether the calf breathes, whether its eyes are cloudy when it is born, etc., can really help determine whether the cause is most likely infectious or non-infectious. McGuirk made a chart for one of the dairies she works with showing what samples to collect, how to store them and the submission process so they can satisfactorily rule out infectious causes of still-births.
“If the veterinarian isn’t actively engaged in reviewing and monitoring records, creating new records and using records to show oppor-tunities that have a positive cost-benefit effect, then the motivation for keeping records or trying to solve the problem will disappear,” McGuirk states. The veterinarian also needs to get out with the cows. “I had a herd where calving ease scores were surprisingly low for the rate of stillbirths. But, in examining the fresh cows, I found evidence of traumatic calving assistance. It turned out that cows/heifers were moved to the labor pen when feet were showing. Labor is delayed when that hap-pens, but the people watching the calving pens were not instructed to wait. Instead, they intervened within an hour if the calf wasn’t produced.”
To investigate stillbirths, it’s useful to separate out the risk factors and keep records of the different types of situations surrounding the event. Many computerized records will already be able to generate reports that help reveal the important stillbirth risks. McGuirk says the following data may be useful:
- All births counted by single or twins.
- Al single and twin births counted by calf gender.
- Counts of single and twin births by calf status (alive or dead).
- Calving ease and dystocia scores.
- Stillbirths by single or twin status.
- Stillbirths by calving ease and/or dystocia score.
- Stillbirths by calf gender.
- Stillbirths by lactation number.
- Stillbirths by dam’s previous days-carrying-calf.
- Stillbirths by month of calving.
- Stillbirths by dam’s age at first calving.
It’s important to rule out infectious causes of stillbirth such as Neospora caninum, Salmonella spp, Listeria monocytogenes, Q Fever, Campylobacter fetus venerealis, Chlamydophila, Brucella. My-cotoxins have also been incriminated.
To investigate infectious causes, necropsies and sample submissions are important. However, it must be noted that samples need to be taken from as fresh a dead calf as possible. Because each diagnostic lab may have different requirements for tissue type and fixing techniques, consult your lo-cal diagnostic lab.
Post-mortem examination and collection of a placenta sample, calf blood, abomasal contents, lung, liver, kidney or brain will help rule out these causes. “Decide the approach — collection of samples by trained farm labor, a veterinary technician or a veterinarian on call — and the procedure for getting appropriate samples submitted and the records recorded,” McGuirk suggests. “A diagnosis takes time and it doesn’t usually come from just one calf or cow. A commitment has to be made to reviewing, assessing and collating the results so that appropriate actions are taken.”
Reduce stillbirths in heifers
Your clients will probably never have a zero incidence of stillbirths, but you can reduce their stillbirth numbers with sound heifer management. “Monitor heifer growth and health very closely,” says Sheila McGuirk, DVM, PhD. “Resolve the health issues, particularly pneumonia, that result in slow growth and poor reproductive performance in heifers.”
Housing management that provides adequate feeding and resting space is important for optimal growth and reproductive performance in the entire group. Feed appropriate diets and monitor per-formance. “I like to see height and weight tape measurements taken at 12 months, 16 months and again at 20 months,” McGuirk suggests. At each of those times, lack of growth, over-conditioning or a dispersion in stature and weight can be addressed.
Small heifers can be picked out for a full examination and/or held back in a younger group of calves for catch up. Over-conditioned heifers or pens of heifers can be identified early, while diet, exercise or a combination of factors can be adjusted.
Sire selection for calving ease and calf survival are management tools that can be used effectively. “Recently, I have seen crossbreeding and the use of sexed semen as approaches to improve calving ease of the first-calf heifers,” McGuirk notes.
Finally, understanding, training and monitoring criteria and the protocols for assisting deliveries are essential. There are dystocias that truly need assistance, and there are longer deliveries that need time. It is the latter that can lead to big problems. First-calf heifers, for example, need quiet, uninter-rupted comfort to calve. “Turn off the lights and give first-calf heifers two hours and a comfortable place to deliver a calf,” McGuirk says.
And back off on assistance when it’s not needed. “Shift changes are not an excuse to pull a calf,” McGuirk says. “Few realize how important the mechanics of the delivery are to the survival of a calf. The feedback and stimulation from a strong delivery by the cow gives the calf stimulation to breathe, clear itself of its bodily fluid and adjust to post-uterine life. It is really important to emphasize that time spent in good labor, with strong contractions and slow but steady progression through the birth canal are the calf’s best stimuli to live. Don’t assist a cow that is progressing in labor just because she is taking too long.”
McGuirk adds that metabolic problems, stressful pain changes, poor comfort, cleanliness and over-crowded close-up groups may signal labor to start prematurely. “Short gestation lengths may be an indication of these types of problems. These events detract from a good delivery, and the rates of stillbirths are likely to go up.”