COLOSTRUM REPLACER PRODUCTS: A PRELIMINARY SUMMARY OF 13 STUDIES
Colostrum management is the most important thing concerning calf health by provision of passive transfer of immunity (PTI). The concentration of serum IgG > 10 g/L at 24 hour of birth is widely used as the criteria for adequate PTI. Typically, feeding 3 to 4 L of high quality colostrum within 2 hours after birth will do a good job at achieving PTI. If you are testing with a colostrometer on-farm, a reading of > 70 g/L is generally a safe number ensuring at least 50 g/L of IgG in your colostrum.
Running short of colostrum may happen on many farms either due to seasonal calving, poor quality, or concerns about transmission of Johne’s disease. There are many brands of colostrum replacer products on the market that could be used as a source of IgG. Typically, these colostrum replacers can be categorized based on IgG source as either plasma-derived or colostrum-derived. Research with these colostrum replacers have produced mixed results regarding their efficacy. To better understand the data, I summarized 13 studies conducted after 2000 (12 published and 1 study with unpublished data from Miner Institute) with 48 treatments comprising 10 for maternal colostrum (MC), 22 for plasma-derived colostrum replacer (PDCR, containing at least 100 g of IgG per dose), 11 for colostrum-derived colostrum replacer (CDCR) and 5 for plasma-derived colostrum supplement (PDCS, containing < 50 g of IgG per dose). This preliminary summarization should give a holistic view of the effect of colostrum replacers from different sources on IgG absorption and relationship with serum total protein.
IgG absorption efficiency of colostrum replacers products
The big concern of using colostrum replacer products may be how much should be fed and how efficient the IgG will be absorbed. As shown in Figure 1, all treatments using PDCR or PDCS at the amount providing 100 g of IgG or less failed in PTI (10 g/L of serum IgG) and about half of the studies using CDCR providing ~100 g IgG were sufficient to achieve PTI. However, when IgG intake increased to > 150 g, all calves fed CDCR products had adequate PTI across studies, whereas calves from most studies feeding PDCR or PDCS had adequate PTI, but a relative lower serum IgG concentration than those fed CDCR and still had higher risk of failure PTI, which may be due to variations in management practices among studies. The data shown in Figure 2 indicated that PDCR products were associated with relatively lower IgG apparent efficiency of absorption (AEA) compared with CDCR when evaluated at the same amount of IgG intake. It seems that 30-40% of AEA is a decent level for most colostrum replacer products from both sources. Therefore, it seems feeding CDCR at the dose providing > 150 g IgG most likely to guarantee the successful PTI for your calves, but you may need to be more cautious if use PDCR at similar dose due to greater variation in performance.
Relationship between serum total protein and IgG when using colostrum replacers products
It is widely accepted in industry that a serum total protein concentration of more than 5.2 or 5.5 g/dL at 24 hour of birth is a good indicator for adequate PTI (serum IgG > 10 g/L). However, some studies showed that calves may already have adequate PTI at a lower level of serum total protein when colostrum replacer products are used rather than colostrum. As shown in Figure 3, if you draw a vertical line at the point of 10 g/L IgG on the X-axis, the cut-off value for maternal colostrum was around 5.5 g/dL serum total protein, which is consistent with common recommendations, but it was below 5.0 for both CDCR and PDCR. Based on regression equations (Table 1), serum total protein should be higher than 5.0 and 4.9 g/dL to achieve PTI for CDCR and PDCR products, respectively.
Besides total IgG mass, other factors that varied among several studies may also affect absorption efficiency including time, method, and volume of colostrum replacer feeding. These factors were not taken into account in the analysis, which was the limitation of this preliminary summary.
Figure 1. Relationship between IgG intake and serum concentration of IgG for CDCR, PDCR, and PDCS. Each symbol (either solid circle or triangle) represent the result of one treatment from 13 studies. A line of linear regression was simulated to predict the relationship for each category of product (A higher R-square indicates a better fit of the data.)
Figure 2. The distribution of apparent efficiency of IgG absorption (AEA) at 24 hour after birth for different amounts of IgG intake from colostrum replacer products.
Figure 3. The relationship between serum concentrations of IgG and total protein (TP) of calves when MC, CDCR, and PDCR were fed.
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