- Animals: bovine
- Animal Production: animal protection and health, feed management
- Education and Training: extension, on-farm/ranch research
Domestic ruminants are born without a preestablished immune defense system. As such, neonatal calf survival is completely dependent on receiving antibodies/immunoglobulins (Ig) through drinking maternal colostrum (transfer of passive immunity; TPI). Current colostrum feeding practices are dictated by two factors: 1) “good quality” colostrum with a minimum of 200 grams of total IgG, and 2) feeding before ‘gut closure,’ or the time when the calf can no longer absorb IgG. Interestingly, we find these recommendations somewhat arbitrary as our recent work demonstrated that previous methods of quantifying IgG have reported a 3-fold underestimate of colostrum IgG content, in relation to farm-measured Brix % scores (50 g/L vs 155 g/L IgG). This called for a full re-evaluation of the IgG threshold necessary for optimal TPI. Equally surprising was our finding that mammary biopsies post-parturition indicated active IgG secretion, and contrary to current dogma, we discovered that a second-milking collected 16 hours post-parturition has substantial IgG content (~125 g/L). These findings highlight serious gaps to understanding, and the fact that current recommendations are not substantiated by direct and definitive measures consistent with cow and calf physiology, but rather weakly justified. Thus, we hypothesize that the spatial and temporal quantitative examination of immunoglobulin absorption machinery in the calf intestines will unravel the precise extent and duration of TPI preceding calf ‘gut closure’. In direct application, our findings would make physiology-based accurate recommendations that would allow for producers to maximize the benefits of colostrum feeding to improve calf health and overall farm profitability.
Project objectives from proposal:
As intestinal immunoglobulin receptor expression is the determining factor for immunoglobulin absorption and thus TPI, the window for neonatal gut closure needs to be completely re-evaluated and based directly on the expression of the intestinal immunoglobulin receptors. As recent data from our lab indicates that colostrum produced at 16 hours post parturition still contains elevated IgG levels (126 g/L). We also determined based on FcRN gene expression that the mammary gland actively secretes IgG during the post-partum period of lactation. These findings indicate that the currently accepted timing of gut closure (12 hours) could be inaccurate, and current colostrum feeding practices effectively truncate the physiological period of time in which immunoglobulin absorption can occur in the calf intestine. The following objectives will allow us to address this gap in our knowledge, and allow us to apply new information learned to help dairy producers with colostrum management: 1. Precisely and quantitatively determine the full window of time that a neonatal calf intestine can absorb colostrum immunoglobulins. We will use quantitative polymerase chain reaction (qPCR) to directly measure immunoglobulin receptor expression (mRNA) across the full length of the calf intestine (duodenum, jejunum and ileum). Samples will be collected within 0-30 hours after birth, with calves randomly assigned to one of six different sample collection time point groups: 0, 6, 12, 18, 24 and 30 hours after birth. Concurrently, we will examine for abomasal function (onset of pH and protein degrading enzymes) to determine the period of permissive conditions for IgG uptake. 2. We will develop a colostrum feeding protocol founded on calf intestinal physiology for maximum immunoglobulin absorption. Based on serum IgG measurements by quantitative Western blots, we will also redefine the threshold serum IgG levels that correlate with successful TPI, which will reformulate industry standards and targets for colostrum feeding programs.