Evaluation of a refugia-based strategy for gastrointestinal nematodes on weight gain and fecal egg counts in naturally infected stocker calves administered combination anthelmintics.

Refugia-based strategies associated with a combination of anthelmintic drugs belonging to different drug classes are becoming more common management practices to mitigate anthelmintic resistance (AR) in gastrointestinal nematodes (GIN) in small ruminants. Though refugia-based strategies have been largely demonstrated in small ruminants, cattle veterinarians and producers are considering such management strategies in grazing cattle production systems. Implementing refugia-based strategies lowers the amount of anthelmintics used in the herd and therefore slows the progression of AR by allowing a proportion of worms to escape drug selection pressure. The objective of this study was to observe the effect of a refugia-based strategy on body weight (BW), average daily gain (ADG) and fecal egg counts (FEC) of trichostongyle-type nematodes in naturally infected beef calves over a 131-day grazing season when compared with a whole herd treatment strategy, using the same combination of drugs. Stocker calves (n = 160) were ranked by body weight within sex then allocated to 16 paddocks, which were randomly assigned to one of two treatment groups. All calves in Group 1 (n = 80) were administered treatment, while in Group 2 (n = 80) the steer with the highest FEC in eggs per gram (EPG) within the paddock was left untreated. Treated calves received an extended release injectable 5 % eprinomectin (LongRange®, Boehringer Ingelheim Animal Health USA Inc.; 1 mL/50 kg of BW) and a 22.5 % oxfendazole oral suspension (Synanthic®, Boehringer Ingelheim Animal Health USA Inc.; 1 mL/50 kg of BW). Fecal egg counts and BW were recorded on days (D) -35, 0, 21, 131, and 148 to calculate the average fecal egg count reduction (FECR) and ADG for both groups. Linear mixed models, with paddock as the experimental unit, were used for analyses. The EPG differed on D21 (p < 0.01) and D131 (p = 0.057) with Group 2 having a higher average FEC (15.2 EPG D21; 57 EPG D131) compared with Group 1 (0.4 EPG D21; 37.25 EPG D131). However, there was no significant difference in average BW or ADG between treatment groups throughout the study. Results suggest refugia-based strategies could be implemented without significant negative impacts on average BW and ADG across other calves in the herd.

Assessing the Role of Systems Thinking for Stocker Cattle Operations.

Bovine respiratory disease (BRD) is recognized as a complex multifactorial disease often resulting in significant economic losses for the stocker industry through reduced health and performance of feeder calves. Conventional approaches to manage BRD in stocker production systems can be challenged with a restricted view of the system, most importantly the structure, which drives the behavior of the system and fails to anticipate unintended consequences. The translation and implementation of systems thinking into veterinary medicine can offer an alternative method to problem-solving. Fundamental to the success of the systems thinker is the conceptualization of the Iceberg Diagram intended to identify root causes of complex problems such as BRD. Furthermore, veterinary and animal health professionals are well-positioned to serve as facilitators to establish creative tension, the positive energy necessary to identify high-leverage strategies. The interrelationships and interconnected behaviors of complex stocker systems warrant an understanding of various archetypes. Archetypes provide the systems thinker with a decision-making tool to explore tactics in a nonlinear fashion for the purpose of recognizing short- and long-term outcomes. Developing literacy in the discipline of systems thinking will further equip professionals with the skillset necessary to address the multitude of challenges ingrained in complex stocker cattle systems.

Bovine Respiratory Disease Considerations in Young Dairy Calves.

Raising young dairy calves presents many challenges for producers and veterinarians including losses attributable to BRD. This article will discuss several key concepts for practitioners to consider when applying evidence-based medicine for the control and treatment of BRD in young dairy calves. The authors review BRD complex, provide considerations for diagnostic approaches, and discuss research associated with the control and treatment of BRD.