Failure of transfer of passive immunity (TPI) leads to greatly increased risk for disease and death in young dairy calves. Immunoglobulins (Ig) are greatly enriched in the cow´s first milk (colostrum) and are critical to assure TPI, which is defined by the serum concentration of IgG. Calves on most dairy farms are therefore hand-fed colostrum harvested from the cow to assure adequate colostrum intake rather than to allow direct suckling from the udder. Recommendations for the optimal volume of colostrum to feed each calf are lacking with most producers feeding a standard 4 L portion shortly after birth, regardless of the size of the newborn. As dairy calves do not voluntarily consume this much colostrum, it is often fed by oroesophageal tube (esophageal feeding). This practice is widespread with the belief that a large amount of colostrum within hours after birth delivers a high amount of total Ig to the calf. Despite this, the proportion of calves with failure of TPI and preweaning disease events remains unacceptably high and calls into question the practice of a standardized high volume. Our preliminary data suggest that smaller volumes lead to excellent TPI, possibly due to improved gastric emptying rates. Recently, concerns regarding the welfare implications of force-feeding a large volume of colostrum by esophageal feeder have been raised due to reports of colic behavior. However, data are not available to understand the behavior outcomes of colostrum feeding in calves. Our central hypothesis is that the volume of colostrum at first feeding alters the efficiency of IgG transfer, alters gastric emptying, and affects the behavioral response of newborn dairy calves.

In the 1-year funding period, we will address the following 2 independent aims in a randomized block design: Aim 1A: Measure the effects of colostrum volume as a % of birth body weight (BBW) given in a single feeding shortly after birth on the transfer efficiency of IgG. The transfer of IgG from the small intestine into circulation will be compared 24 h after colostrum feeding by esophageal feeder. We will compare differences in IgG concentration between the treatment groups fed either 6, 8, 10, or 12% of BBW (n = 21/group, total n = 84). Aim 1B: Analyze differences in gastric emptying. In a subset of 8 calves per group (n = 32 total), we will use acetaminophen as a marker of gastric emptying rate as previously described by our collaborator (Dr. Mike Steele, University of Guelph) and compare gastric outflow between the treatment groups.

Aim 2: Describe the behavioral response of newborn calves to oral administration of different volumes of colostrum based on % of BBW.

We will use continuous video and audio recording to score calf behavior in all 84 calves for 12 h after feeding using a pre-defined ethogram to investigate activity, vocalization, and indicators of abdominal pain to compare behavior scores between the groups.