How do you reap the advantages of raising calves in group pens on autofeeders without sacrificing their health?
Researchers at the University of Minnesota recently published a study in the Journal of Dairy Science that examined a range of management factors in group-housing, autofeeder rearing systems for preweaned calves, and how they impacted calf health. Lead researcher Marcia Endres said the team studied autofed calves on 38 farms in Minnesota, Wisconsin and Iowa, from November 2012 to May 2014.
The researchers visited each farm approximately every 60 days, and evaluated calf health factors including attitude; eye, ear and nasal health; and evidence of diarrhea (measured via hide cleanliness on the rear quadrant of the calves). They used a scoring range of 0 to 4 for each factor, with 0 being completely healthy and 4 being severely ill. Calves with a score of at least 2 in any area also had their body temperature assessed via rectal thermometer.
In addition, the team evaluated facilities, nutrition programs and feedstuffs, including bacteria levels in milk and milk replacer. Their most prominent findings included:
(1) Positive-pressure tube ventilation systems had a tremendous impact on calf health. Most of the farms in the study (86.8%) had these systems in place, regardless of whether their barns were mechanically or naturally ventilated. But the barns that did not have positive-pressure tubes had an 80.6% higher likelihood of at least one calf being detected with a fever on any given day of evaluation.
(2) Bacteria in milk increased illness incidence. In the study, high bacteria level in reconstituted milk replacer defined by a standard plate count (SPC) of greater than 100,000 cfu/mL. Feeding calves milk replacer that exceeded this bacterial threshold increased the incidence of poor attitude by 20.7%; a higher ear score by 31.8%; and calves being detected with fever by 81.5%.
“Most commercial milk replacer has very low bacteria counts coming out of the bag, but autofeeders contain several potential reservoirs of bacterial contamination,” shared Endres. Among them are the mixing tank and transfer tubing; milk powder storage area; and nipples from which the calves nurse. Endres added that many autofeeder machines are housed in heated rooms to prevent freezing. But this heat, combined with poor ventilation, can contribute to high bacteria counts. So, too, will installation errors that allow milk to pool in the mixing tank or tubing.
(3) More milk equaled less sickness. Calves that were allowed the greatest peak milk allowance had the lowest incidence of diarrhea as assessed via hide cleanliness. For each liter of increased daily milk allowance, there was a 12% decrease in odds of calves receiving a high score for hide dirtiness. “Previous studies have shown that nutritional insufficiency has a suppressive effect on immune function, which this study appeared to reinforce,” said Endres.
(4) Speed to peak milk allowance made a difference. Almost all of the recorded health scores were significantly impacted by the number of days it took to advance calves to their peak milk allowance. Those that hit peak milk faster were healthier. Each additional day it took to reach peak milk allowance resulted in increased odds of calves receiving a higher attitude score (1.3%), ear score (2.2%), eye score (2.2%), hide dirtiness score (1.95); and fever incidence (2.5%).
(5) Rectangular pens are preferred. Pen shape had an impact on calf health, with an association in the study found between eye score and pen shape. A rectangular pen shape (pens at least 2.5 times longer than they were wide) was associated with a 53.7% decrease in the odds of a higher eye score when compared with a square pen. “Longer, narrower pens -- particularly those with a positive pressure ventilation tube running above them -- may benefit from a greater effect of ventilation on airborne pathogen density,” noted Endres. “The distance fresh air is able to travel from a ventilation tube is limited to 3 to 5 meters on either side, so in certain circumstances a narrower pen design may help to ensure that the entire calf pen is properly ventilated.”
Endres said the two factors that appeared to have the most far-reaching impact on calf health were bacterial contamination of the liquid diet, and the speed at which calves reached their peak milk allowance. “As more farms adopt autofeeder and group housing systems to raise their calves, these and other management steps can help improve their success in raising healthy replacements,” she stated.