Location: Livestock Issues Research
Project Number: 3096-32000-009-010-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 1, 2025
End Date: Apr 30, 2028
Objective:
The objective of this study is to determine if pre-weaning management influences
liver abscess prevalence and severity in weaned beef dairy crossbred cattle.
Approach:
On d 0, calves will be moved into individual pens within the LIRU Calf Building. At this time, calves will undergo a ration change consisting of more digestible starch content with high energy similar to a finishing ration for 3 d. On d 3, all calves will be switched back to the control starter ration for two days. This cycle will be repeated three more times. In the event of bloat, a tube (flexible tubing 0.95cm diameter x ~1.5 m long) will be passed orally (with or without the use of a speculum) into the rumen to relieve pressure. If bloat persists following two pressure releases, a sodium bicarbonate solution (~5%; ~500mL) will be administered intraruminally via a tube to buffer rumen pH. The tubing protocol slightly deviates from the LIRU Program of Veterinary Care for calves; however, given that we anticipate bloat in these calves, tubing is more likely to eliminate the bloat as compared to exercise and diet removal which could exacerbate acidosis when feed is returned.
On d 0, 5, and 10, calves will be lightly restrained in their pens or chute to allow for collection of rumen fluid and fecal samples. Samples will be collected from every animal in each treatment group. Additionally, calves will be administered the bacterial cocktail. For collection of rumen fluid and dosing of the bacterial cocktail, a flexible tube (~ 0.95 cm diameter x ~1.5 m long) will be passed through a speculum from the mouth to the rumen to facilitate sample collection and treatment administration. The bacterial cocktail will contain ~100 ml each of Salmonella Lubbock (~1.0 x 106 CFU), and Fusobacterium necrophorum (~1.0x 106 CFU) and will be administered by trained personnel. Following inoculation, the rumen tube will be flushed with ~100 ml of sterile saline or phosphate buffered saline. Immediately following inoculation, an aliquot of inocula will be diluted and spiral plated on selective media to determine actual inocula concentrations. Following the bacterial inoculation on d 10, calves will receive the acidotic ration for the remainder of the study.
On d 38 ± 3 days, calves will be weighed and humanely euthanized following the collection of blood samples for hematology, serum, and plasma as described above. Serum and plasma isolation will be used to determine complete blood cell counts, and blood chemistry. Upon harvest, livers will be collected and scored for abscesses and scars. Abscesses will be aseptically dissected, placed in a sterile sample container, and stored prior to evaluation and isolation of the inoculated bacterial strains. A sample from each liver as well as mesenteric and subiliac lymph nodes will be collected and shipped for bacterial quantification. Additionally, the rumen, lungs, ileum, and cecum will be cleaned and scored for abnormalities. Ruminal epithelial, liver and ileum tissues will be collected and placed in formalin for histological analysis. Rumen, ileum and cecum fluid will also be collected and stored for analysis.