Heat treatment of bovine colostrum: II. Effects on calf serum immunoglobulin, insulin, and IGF-I concentrations, and the serum proteome.

In-depth analysis of colostrum components has identified hundreds of proteins, but data are sparse regarding their systemic uptake in the newborn calf. Moreover, heat treatment may influence these colostral components and their absorption. Our objectives were to describe the serum proteome of newborn calves before and after colostrum feeding and the possible effects of colostral heat treatment. Newborn Holstein heifer calves (n = 22) were randomized within pair and fed heat-treated (n = 11; 60°C, 60 min) or raw (n = 11) colostrum at 8.5% of birth body weight by esophageal feeder within 1 h of birth. After the single colostrum feeding, calves were not fed until after the 8-h time point, when milk was offered free-choice. Blood samples were taken immediately before feeding (0 h), as well as 4, 8, and 24 h after feeding. Whole blood packed cell volume (%), serum Brix percentage, and plasma glucose concentrations were determined for all time points. Plasma insulin and insulin-like growth factor-I concentrations were determined by radioimmunoassay for selected time points. Serum IgA and IgG were measured by radial immunodiffusion at 24 h. The serum proteome was analyzed using nano-scale reverse-phase chromatography and tandem mass spectrometry (nano LC-MS/MS) in 0- and 8-h samples. For proteomics analysis, ratios of results for 8-h to 0-h samples were analyzed with false discovery rate adjustment. For all other outcomes, repeated-measures ANOVA was performed with the fixed effects of group, time, and their interaction, and random effect of pair. Serum Brix percentage and glucose concentrations increased over time and were independent of colostrum treatment. Serum IgG and IgA concentrations at 24 h did not differ between groups. Nano LC-MS/MS identified a total of 663 unique proteins in serum, of which 261 increased in abundance, whereas 67 decreased in abundance after feeding in both groups. Among serum proteins that increased in abundance and that were previously identified in colostrum, many belonged to those involved in immune response, coagulation, the classical complement pathway, or the antimicrobial peptide class of cathelicidins. Serum proteins that decreased in abundance and that were identified in colostrum belonged to the alternative complement pathway and the membrane attack complex. Thirty-eight proteins differed in calves that were fed heat-treated colostrum compared with those fed raw colostrum. Decreased abundances in calves fed heat-treated colostrum included several enzymes involved in glycolysis or glycogenolysis, whereas the incretin gastric inhibitory polypeptide and serum insulin were increased in this group. Our findings point to important innate immune defense pathways associated with colostrum ingestion in newborn calves. Furthermore, calves fed heat-treated colostrum showed differences in serum proteins and enzymes associated with carbohydrate metabolism.

Heat treatment of bovine colostrum: I. Effects on bacterial and somatic cell counts, immunoglobulin, insulin, and IGF-I concentrations, as well as the colostrum proteome.

The objective of this study was to investigate the effects of heat treatment on colostral low-abundant proteins, IgG and IgA, insulin, and insulin-like growth factor I (IGF-I), as well as bacteria and somatic cells. First-milking colostrum samples >8 L and Brix % > 22.0 were harvested from 11 Holstein cows on a commercial dairy in New York State and split into 2 aliquots using single-use colostrum bags. One aliquot of each pair was cooled on ice immediately after harvest (raw, R; n = 11), and the other was heat-treated for 60 min at 60°C (heat, H; n = 11). All samples were analyzed for IgG and IgA via radial immunodiffusion assay and insulin and IGF-I concentrations by radioimmunoassay. Total bacterial counts and somatic cell counts (SCC) were determined using standard plate culture techniques and flow cytometry, respectively. Samples from a subset of 5 pairs (n = 10) were further analyzed by nano liquid chromatography-tandem mass spectroscopy, after ultracentrifugation at 100,000 × g for 60 min at 4°C to enrich the low-abundant protein whey fraction. Data were analyzed using either paired t-test or Wilcoxon signed-rank test or using an online software package to analyze proteomics data. Outcomes of proteomics analysis were fold change ≥1.5 between pairs, and paired t-tests with false discovery rate-adjusted P-value < 0.05. The median reduction of IgA concentrations was 8.5% (range: 0-38.0%) due to heat treatment, whereas IgG concentrations did not change due to treatment. Insulin concentrations decreased by a median of 22% (7-45%), and IGF-I decreased by 10% (0-18%) in H samples. Heat treatment was associated with a median reduction of SCC of 36% (0-90%) in paired samples, as well as a median reduction in total bacterial count of 93% (45-100%) in H versus R samples. Proteomics analysis identified a total of 328 unique proteins that were present in all 10 samples. Nine of the 25 proteins that decreased by at least 1.5-fold in H compared with R were identified as complement proteins. We conclude that heat treatment of colostrum is associated with a reduction in the concentration of bacterial counts and SCC, IgA, insulin, and IGF-I. In addition, proteomics analysis of colostral whey identified several complement components and other proteins that decreased in abundance due to heat treatment. Although IgG concentrations were unaffected and a reduction in bacterial counts was achieved, the change in several immunologically active proteins and growth factors may have biologically important effects on the developing immune system of the neonate fed heat-treated colostrum.