Disease control practices used to prevent morbidity and mortality in preweaned beef calves

Calf morbidity and mortality negatively impact economic returns for cow-calf producers. Given this, preventing infectious diseases, including Neonatal Calf Diarrhea (NCD) and Bovine Respiratory Disease (BRD) is essential. However, recommended practices to attain this have not been recently summarized or updated. Therefore, the aim of this thesis was to study several aspects relevant to the implementation of disease control and update recommended practices. The objectives were to: i. summarize the scientific evidence on the effectiveness of practices in preventing health and mortality outcomes, ii. prioritize practices based on their usefulness in herds considering their effectiveness, ease of implementation, and economic feasibility, iii. assess the frequency of outbreaks, use of practices, the impact of practices on outbreaks across Canadian cow-calf herds, and the importance given to productivity parameters across regions, and iv. compile the evidence into a Calf Health Decision Tool to support discussions between producers and veterinarians and pilot it in Alberta, Canada. The work reported in Chapter 2 showed that the evidence of the impact of practices on mortality, regardless of the cause, was scarce. Only a few practices showed statistically significant associations. Herds that routinely intervened with colostrum or checked the fullness of the udder had a lower mortality risk than those not using these practices. Herds that calved early or during winter had a higher mortality risk than those calving later. Herds with longer calving seasons had a higher mortality risk than those with shorter seasons. Calves from herds that did not supplement with vitamin E and selenium at birth had higher odds of mortality than those from herds where this practice was used. Chapter 3 showed that most practices impacted both NCD and BRD. However, the evidence was of low and very low certainty. Chapter 4 found that veterinarians prioritized the effectiveness of a practice over its ease of implementation and economic feasibility. Vaccinating calves against clostridial disease and providing colostrum in case a calf had not nursed using an oesophageal tube or nipple bottle were practices considered always useful for all herds. Most practices were shown to have intermediate levels of usefulness in herds. Prophylactic and metaphylactic use of antibiotics were considered among the least useful. Yet, all practices that were considered at least very useful for some herds were deemed relevant enough to be included in a Calf Health Decision Tool. Chapter 5 found that over 40% of herds had at least one type of outbreak during the last three calving seasons. Also, it was demonstrated that eastern and western herds managed their cow-calf herds differently. Some frequently used practices were shown to increase the odds of having outbreaks. It was also found that western and eastern producers gave similar importance to several productivity parameters of their herds. In Chapter 5, it was revealed that the Tool was useful for facilitating discussions between producers and veterinarians regarding disease control. Responses showed that delaying the calving season for early calving herds was not feasible. Most herds could only follow only one of two recommended practices, either calving heifers before cows or calving seasons shorter than 80 days. Therefore, there might be an incompatibility between these recommendations. Most producers were willing to consider using some method to segregate calves by age. Given this, this could become a more widespread recommended practice. Only half of the herds vaccinated dams against NCD, and even one herd with a history of NCD outbreaks was not doing this. This may be because producers felt reluctant to manage pregnant dams in the chute. However, they were more willing to consider calf vaccination instead. The findings presented in this thesis reveal a general lack of consistent evidence proving the effectiveness, ease of implementation, and economic feasibility of practices. Overall, the work in this thesis showed that many commonly used practices make herds vulnerable to outbreaks, and thus, tailoring disease control practices to the operation is essential. Therefore, The Calf Health Decision Tool created may help support discussions between veterinarians and producers to implement this and prevent disease and mortality.

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