Producers have all sorts of ways of assessing calf vigour, yet subjective evaluations can be inconsistent and some signs of distress or trauma from hard births may not be obvious.
As part of her PhD research at the University of Guelph, Christine Murray developed a VIGOR scoring system to rate signs of distress in a newborn calf and decide on a course of action (see image further down).
The VIGOR score was developed along the lines of the APGAR system used to assess newborn babies on appearance (colour), pulse (heart rate), grimace (stimulation), activity (muscle tone), and respiration.
Similarly, VIGOR is an acronym for five observable and measurable signs of newborn calf trauma: visual appearance, initiation of movement, general responsiveness, oxygenation and rates (see scoring chart).
Sometimes the effects of a hard birth (dystocia) on a calf that survives are obvious, such as a broken leg bone, swollen nose and tongue, lack of gumption to get-up-and-go and/or sucking reflex to get the all-important first feeding of colostrum for immunity, energy and survival.
Other common consequences not easily picked up by observation alone include broken ribs and vertebra, internal bruising, bleeding in the brain, and liver ruptures. These injuries can heal with time but cause discomfort and reduce vitality, Murray says.
Trauma from dystocia also compromises a calf’s ability to regulate body temperature because it may weaken the shivering reflex and impair mobilization of fat for energy. This can decrease a calf’s motivation to stand and consume colostrum, especially in temperatures outside of its thermoneutral zone of 10 C to 25 C.
More subtle yet is hypoxia, or inadequate oxygen to cells and tissues when the umbilical cord detaches before the calf takes its first breath. Respiratory acidosis occurs as carbon dioxide builds up in the blood, Murray explains. Long and/or intensive labour exacerbates the condition because the calf has to rely on anaerobic glycolysis to get oxygen to the tissues and this leads to a state of metabolic acidosis.
Murray’s thesis project started with assessing how calving difficulties affect a newborn calf’s physical condition and behaviour at two hours, 24 hours, seven days and 14 days of age, and evaluating the extent to which those characteristics are associated with calf vitality, passive transfer of immunity and growth.
She monitored 45 calvings at the University of British Columbia’s Dairy Education and Research Centre from the first sign of contractions, recording everything from the first appearance of fetal membranes until two hours after birth when each calf received the same quality and quantity of colostrum replacer.
Calves born from a hard pull took significantly longer to rise and rest on the sternum and had significantly weaker sucking reflexes than those born unassisted.
Immunoglobulin concentration in the blood at 24 hours was adequate in all calves, indicating that calving difficulty in itself didn’t reduce the calf’s ability to absorb antibodies from colostrum. That said, had calves from hard pulls not been fed colostrum replacer, they may have lacked the motivation to stand and suckle on their own. In turn this could reduce colostrum intake and lead to failure of passive transfer of immunity.
Murray found that calving difficulty was significantly associated with VIGOR score. Bull calves had worse VIGOR scores than heifers, probably because of their larger size. Calves that had worse VIGOR scores were also more acidotic and had lower weight gains out to six weeks of age.
Meloxicam shows promise
It seemed reasonable that if a non-steroid anti-inflammatory drug (NSAID), such as Meloxicam, could reduce swelling and discomfort, the newborn may get off to a better start. The analgesic effect lasts for about three days, giving the calf time to get up, suckle colostrum and heal, Murray explains.
Two trials were set up to assess the VIGOR scoring system and the use of the NSAID Meloxicam to improve calf vitality, passive transfer, health and growth. One was a semi-intensive trial involving two dairy herds with 284 calves and the other was a field trial involving 10 dairy herds with 842 calves.
Farm staff recorded calving details and scored each calf using the VIGOR system before randomly assigning each calf to receive either a single one-millilitre injection of Meloxicam or a placebo solution. Calves in the semi-intensive trial were VIGOR scored again one to six hours after treatment with Meloxicam or the placebo.
For the semi-intensive trial, researchers visited the herds three times a week to measure blood gases at less than two hours of age, serum total protein, sucking reflex, rectal temperature, health scores, milk intake, weight and height up to eight weeks of age. The field trial involved weekly visits to record the same parameters with the exception of blood gases, sucking reflex and milk intake.
Murray says calves that received Meloxicam following birth had significantly improved VIGOR scores and sucking reflex from the first to the second assessment, significantly greater milk intakes during the first 30 days (from automated milk feeders typically used in dairy barns), and better overall health throughout the eight weeks compared to those that received the placebo.
While Meloxicam improved weight gain in the first week of life by 1.1 kilograms on average in assisted calves, the unassisted calves that received Meloxicam actually had reduced weight gains compared to the placebo-treated calves. The reason for the lower weight gain isn’t clear and will require further investigation.
Though her research indicates that Meloxicam therapy shows considerable promise to ease short-term challenges with newborn vigour, Murray advises checking with your veterinarian on using it for this purpose. It is approved in Canada to improve appetite and weight gains and pain relief following de-budding of young calves.
Murray is now the ruminant nutrition research scientist with Nutreco Canada at Guelph and can be reached by email.