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

Abstract

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.

A Scoping Review of On-Farm Colostrum Management Practices for Optimal Transfer of Immunity in Dairy Calves

“…From these results we conclude that heating up until 60 • C results in a minimal reduction of colostral and calf serum IgG concentrations. Together with findings that total bacterial counts and coliform counts are diminished by heat treatment (47,52), pasteurization could provide protection against neonatal disease development (46,139,140). Feeding pasteurized colostrum and milk for a prolonged period (21 days) results in long term health effects, including reduced morbidity, increased body weight and increased milk production during the first lactation (141).…”

“…We summarized the results of the existing literature in Supplementary Table 1. The majority of studies show that colostral IgG concentration is not (41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53) or only slightly affected (54-57) by heating at <60 • C for either 30 or 60 min. In contrast, heating of colostrum above 60 • C frequently resulted in significant loss of colostral IgG (41-48, 50, 54, 58-60).…”

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

“…To address this knowledge gap, the objectives of this study were to compare the serum proteome of neonatal calves before and after colostrum feeding, to investigate changes in serum protein abundance after feeding, and to study whether serum protein abundance differed when colostrum was heat-treated before feeding. Furthermore, our companion work, investigating heat-treatment effects on colostrum, showed decreases in colostral IgA, insulin, and IGF-I concentrations in samples that were heat-treated (Mann et al, 2020). We therefore extended our current objectives to examine the possible heat-treatment effects on the circulating concentrations of these analytes in newborn calves fed either raw or heat-treated colostrum.…”

“…The study was performed between July and August 2018 on a commercial dairy farm in New York State. Harvest of colostrum samples and treatment before feeding are described in detail in our companion paper (Mann et al, 2020). In brief, colostrum of eligible cows was harvested in a 4-stall herringbone parlor (DeLaval International AB, Tumba, Sweden) according to farm protocol within 8 h following calving.…”

“…Tacoma et al (2017) investigated heat-treatment effects on the colostrum proteome of a single pooled sample, and showed that among the 62 proteins that differed between the heat-treated and the raw sample, 44 were reduced in abundance. In our companion paper, we identified and reported 45 proteins that were decreased by heat treatment of colostrum (Mann et al, 2020). The potential effects of these findings on the calf were not further investigated by Tacoma et al, (2017).…”