# Systematic Assessment of Mortalities in Calves at Commercial Calf Ranches and the Association Between Cause of Death and Season

## TL;DR

This study examines the causes of death in calves raised at commercial calf ranches and finds that respiratory disease is the leading cause, with no significant seasonal or demographic patterns.

## Contribution

The study provides the first systematic assessment of calf mortalities in commercial calf ranches and identifies respiratory disease as the primary cause.

## Key findings

- Respiratory disease was the most common cause of death, accounting for 67.5% of cases.
- No significant associations were found between cause of death and season, sex, breed, or ranch.
- Most calves had only one diagnosis, with 86% lacking co-morbidities.

## Abstract

In the dairy industry, producers are using beef semen to produce beef–dairy calves, which has led to an increase in young calves being raised at off-site facilities known as calf ranches. However, little is known about the causes of death in these calves. In this study, researchers necropsied 243 calves that died on four ranches over a year to determine the main cause of death and whether diagnoses differed by season, sex, breed, or ranch. Each calf was carefully examined after death, and the causes were grouped as respiratory disease, digestive disease, septicemia, or other problems. Respiratory disease was the most common cause, accounting for more than two-thirds of deaths. Digestive diseases, septicemia, and other causes were much less common. Most calves only had one diagnosis, but about 10% had a secondary disease present. There were no significant differences in cause of death based on season, sex, breed, or ranch. These findings provide valuable insight into the health challenges faced by calves raised in commercial calf ranches and can help producers, veterinarians, and the industry develop better strategies to improve calf survival.

As breeding practices in dairy industry shift toward the use of beef semen, the number of calves sent off-site for rearing has increased. The limited literature describes mortalities by season, sex, or breed within calf ranches. The objectives were to identify primary and co-morbidities at necropsy in calf ranches and determine whether causes of death varied by season, sex, breed, or ranch. Systematic necropsies (n = 243) were performed monthly over 12 months at four ranches by technicians with diagnoses confirmed by veterinarians. Mortalities were classified as respiratory (RESP), gastrointestinal (GI), septicemia (SEPT), or other (OTH) based on gross necropsy findings. A subset from ranches with 12 months of necropsy data (n = 175) was analyzed using generalized linear and multinomial models to evaluate associations between RESP diagnoses or GI lesion locations and 4-month periods, sex, breed, and ranch. Respiratory disease was most common (67.5%), followed by GI (11.5%), SEPT (9.5%), and OTH (11.5%). Most (86.0%) lacked co-morbidities; RESP (7.0%) and OTH (3.7%) were the frequent primary diagnoses with co-morbidities. No significant associations were detected with time, sex, breed, or ranch (p ≥ 0.11 for RESP; p ≥ 0.13 for GI). Although inferences were limited by sample size, findings provide insight into calf mortalities and co-morbidities in commercial ranches.