Performing Department
Medicine & Epidemology
Non Technical Summary
Preweaning dairy calf health and survival depend on several factors including sufficient ingestion of high-quality colostrum (transfer of passive immunity), nutrition, the diagnosis and appropriate management of calfhood diseases, and reliable record keeping. Preweaned calves are at a higher risk for morbidity and mortality. In California, treatment of sick calves (90%) is the major reason for antimicrobial (AMD) use on conventional dairies. This suggests that several preweaning calf management factors are contributing to this high proportion of morbidity requiring AMD use in calves. To the investigators' knowledge, information on these factors driving AMD use in calves on California dairies is limited. Lack of information on these preweaning management factors affecting AMD use in calves severely limit assessment and recommendations to improve antimicrobial use and stewardship (AUS). Furthermore, the lack of information on AMD use in preweaned dairy calves hinders investigation and studies on bacterial antimicrobial resistance patterns when calves are exposed to AMDs via colostrum, milk/milk replacer, or parenterally via treatments. It is also important to note that there is limited anecdotal information on AMD and non-antimicrobial alternatives, and fate of preweaned calves when AMD are administered on organic dairies. The proposed study will generate data on preweaned calf management factors associated with morbidity, AMD use, and mortality on conventional and organic dairies in California. The data from this study will be used to fill in knowledge gaps on preweaning calf management factors affecting AMD use, form basis for future studies on antibiotic resistance (AMR), and improvement of AUS.
Animal Health Component
100%
Research Effort Categories
Basic
25%
Applied
70%
Developmental
5%
Goals / Objectives
Preweaning dairy calf health and survival depend on several factors including sufficient ingestion of high-quality colostrum (transfer of passive immunity), nutrition, the diagnosis and appropriate management of calfhood diseases, and reliable record keeping. Preweaned calves are at a higher risk for morbidity and mortality. In California, treatment of sick calves (90%) is the major reason for antimicrobial (AMD) use on conventional dairies. This suggests that several preweaning calf management factors are contributing to this high proportion of morbidity requiring AMD use in calves. To the investigators' knowledge, information on these factors driving AMD use in calves on California dairies is limited. Lack of information on these preweaning management factors affecting AMD use in calves severely limit assessment and recommendations to improve antimicrobial use and stewardship (AUS). Furthermore, the lack of information on AMD use in preweaned dairy calves hinders investigation and studies on bacterial antimicrobial resistance patterns when calves are exposed to AMDs via colostrum, milk/milk replacer, or parenterally via treatments. It is also important to note that there is limited anecdotal information on AMD and non-antimicrobial alternatives, and fate of preweaned calves when AMD are administered on organic dairies. The proposed study will generate data on preweaned calf management factors associated with morbidity, AMD use, and mortality on conventional and organic dairies in California. The data from this study will be used to fill in knowledge gaps on preweaning calf management factors affecting AMD use, form basis for future studies on antibiotic resistance (AMR), and improvement of AUS.Summary Goals:Data collection and knowledge of current preweaning calf management practices in conventional and organic dairies in California will improve the understanding of concerns regarding management, health, and productivity of preweaned heifer and bull calves which will help direct targeted improvements in management strategies with the goal of reducing antimicrobial use in preweaned calves on California dairies.Specific aims1. Collect data on preweaned dairy calf health management practices for heifer and bull calves on conventional and organic dairies including colostrum management, milk/milk replacer management, record keeping practices, morbidity and mortality, calf rearing practices, antibiotic and probiotic use, and determination of treatment protocols.2. Compare the preweaned management practices in Objective #1 between organic and conventional dairies.
Project Methods
Methods?Justification of numbers: This study consists of a survey questionnaire and analysis of samples collected from the enrolled farms. Using previously validated methods for survey sampling21, sample size calculation was based on mortality attributable to diarrhea and respiratory disease in preweaned calves in California (19-57%),18-20 an estimated number of at least 150 (which are fewer than conventional dairies) organic dairy farms in California, and a magnitude bound on the error of estimation of 0.1. A minimum sample of 46 farms is required. To account for a 20% dropout of farms, at least 56 farms will be enrolled. Using communications by the investigators with producers and veterinarians, a stratified random sample of at least 28 conventional and 28 organic dairies will be selected. Sampling will consider similar representation of small (30-99 cows), medium (100-499 cows) and large farms (≥500 cows). Assuming a recommended sample size of at least 12 randomly selected calves per farm22, at least 672 calves will be enrolled. Following identification of the farms, an in-person or telephone structured interview to record information on dairy geographical location, herd size, and breeds, and confirm participating in the research will be administered. A survey (Appendix II) will be completed by the enrolled farms and proctored in-person, or over the telephone depending on the preference by the producer. Regardless of the producers' preference, an in-person visit to the farm by one of the investigators to collect samples will be completed.Animals: Samples from cows (colostrum and milk) and serum from preweaned dairy calves.Sample collection: Colostrum fed to calves at each farm will be collected for immunoglobulin (IgG) and lactoferrin concentrations, and bacterial count analysis. Milk samples will be collected for protein, fat and lactoferrin concentrations, and bacterial culture and minimum inhibitory concentrations (MIC) analysis. Serum samples will be collected for IgG concentration measurement to assess passive transfer status in calves aged 1-7 days. Calves with serum IgG concentrations ≤2000 mg/dL will be considered to have FTPI.4 On farms where subjective methods such as color of colostrum or weight of first milking colostrum are currently used to assess colostrum quality, information on the thresholds used by the producers to define acceptable and non-acceptable colostrum samples will be recorded.Sample analysis: Serum IgG and lactoferrin concentrations will be analyzed in my lab at UC Davis using refractometry (Optic and Brix refractometry - farm adaptable methods) and radial immunodiffusion (reference method). Bacterial culture and MIC analysis in colostrum and milk will be analyzed at either at the VMTRC Milk Quality Laboratory (only provide bacterial culture test analysis with possibility to store isolates for later analysis at CAHFS, Davis) or at the CAHFS lab in Davis (pending their availability to add these samples to their work-flow). Milk protein and fat concentrations will be analyzed at a commercial milk processing laboratory (Tulare DHIA). In instances where producers collect minimal information or do not have records for preweaning health parameters (treatments, morbidity, mortality), a simplified paper or electronic individual calf health form for recording these events will be designed in collaboration with the California Department of Food and Agriculture (CDFA), AUS branch and provided to the producers to facilitate data collection. The calf health form will be finalized at end of farm enrollment stage and will be modified to suit data to be collected from enrolled farms. Follow-up with the farms via a phone call or a farm visit when necessary will be completed to check if the farms are using the calf health form. Assuming an 8-10-week preweaning period, 3 follow-ups (1 follow-up every 3 weeks) will be performed. To ensure that enrolled calves on each farm can be easily identified through the preweaning stage, adhesive hip tags with corresponding tags placed on calf hutches will be used.Farm level data collection: Data collected from the farms include calf-rearing practices, colostrum and preweaning calf management practices, and use of veterinary services. The data will be collected through a survey questionnaire (Appendix II).Data analysis: The data recorded from the survey questionnaire will be summarized as descriptive statistics. Other descriptive statistics including farms enrolled, calves enrolled, and proportion of calves with FPTI, morbidity events, and mortality will be reported. The minimum number (12) of calves enrolled for each farm will be the unit of analysis for FPTI, whereas farm will be the unit of analysis for assessing morbidity and mortality during the entire year (2023-2024). Comparison of variables between conventional and organic dairies associated with FPTI including colostrum IgG concentration, use of colostrum replacers, heat treatment of colostrum, colostrum storage practices, dam parity, age of calf at first colostrum feeding, feeding method, and total volume fed within the first 24 hours will be determined using multivariate mixed models. Predictor variables for mortality in conventional and organic dairies will be determined by a Cox proportional hazard model. Association between mortality and serum lactoferrin concentrations will be determined using interval likelihood ratios. Interval likelihood ratios >1 or <1 with 95% confidence interval excluding 1 and a corresponding P<0.05 will be considered significant. Data from this analysis will be depicted in charts, and diagrams that are applicable to the target audiences and will provide understanding of the current preweaned health management practices on organic and conventional dairies. The results from colostrum and milk bacterial cultures and the respective MICs will facilitate the understanding of AMR associated with the direct (oral, feed/milk or parenteral administration of AMDs), and indirect (saleable or non-saleable milk from cows) exposure of calves to AMDs.Intervention program on selected farms Based on the outcomes and fulfilment of the initial deliverables for this part of the study, 6-8 farms representing different management (organic and conventional) and farm size (large, medium, and small) will be selected to evaluate a preweaned calf health intervention program. Areas of intervention will be prioritized based on identifying core components (management deficits similar to all farms) and minor components (deficits specific to a farm) among farms which when improved will result in desired outcomes. Thus, the intervention program on a given farm will consist of core components and minor components for assessing intervention. Outcomes for the intervention program will be assessed using quantifiable improvements in parameters of interest such as improvements in record keeping, and frequency in assessing colostrum quality or passive transfer status following distribution of Brix refractometers.