by Cari Reynolds, W.H. Miner Institute
As cooler weather sets in and the leaves begin to turn, we humans start to think about ‘sweater season’ and, perhaps even more importantly, ‘soup season’. The nip in the air invites thoughts of warm, hearty meals, and there are few things more inviting than a steaming bowl of soup on a chilly day. While the health benefits of a warm bowl of soup are anecdotal at best for humans (although homemade chicken noodle soup from one particular restaurant in my home region is my sworn go-to for kicking a cold), research continues to explore the impact of heat-treated colostrum on calf health. In fact, companion articles from Cornell University recently published in the Journal of Dairy Science provide new information on how heat treatment may affect other essential immunological components of colostrum and their contribution to calf development.
Colostrum management on farms is one area where cleanliness and quality are imperative. It is important to give the calf a good foundation for her immune system. High bacterial content in colostrum leads to a decrease in available immunoglobulin G (IgG), which lowers the amount available for absorption in the calf. Gut maturation and development are also supported by other complement components present in colostrum, such as growth factors, cytokines, hormones, enzymes, insulin, and insulin growth factor I (IGF-I). Many of these components and their mechanisms in colostrum have been understudied, but advancements in proteomics are allowing for further exploration of these components and their roles in immune and gut development. While it is well-documented that heat treatment reduces bacterial count and preserves IgG fractions, these two studies aimed to further explore what effects heat treatment may have on these other essential components and subsequent impact on the calf’s health and development.
First-milking colostrum from 11 Holstein cows, of which the average Brix percentage was 27%, were collected on one commercial dairy in New York State. Colostrum from each cow was collected 3x over one day post-parturition, homogenized, and divided into two 4-L (1 gallon) bags for a total of 22 paired batches. One bag was placed on ice for 30 min, then stored at 4°C (39° F) for up to 24 h. The second bag was heat treated at 60°C (140° F) for 60 min immediately after filling, placed on ice for 30 min, then stored at 4° C for up to 24 h. Samples from the raw and heat treated colostrum batches were analyzed for somatic cell count (SCC), bacterial contamination, IgG, IgA, complement components, proteins, insulin, and IGF-I. As exhibited in previous work, the heat treatment considerably improved the hygiene of the colostrum. Average SCC of the 11 raw colostrum samples was 470,000 (range 300,000-1,300,000); heat treatment reduced this count by 207,000 ± 68,000, or 36%, in comparison to their raw counterparts. Heat treatment also reduced bacterial counts by 93% in comparison to raw colostrum.
However, heat treatment reduced IgA (which is crucial to development of mucous membranes) by 8.5% when compared to raw colostrum, and reduced IgG by 6.6%. Heat treatment also decreased insulin by 22%, and IGF-I by 10.2%. A total of 328 distinct complement proteins were identified in the colostrum samples, many of which were decreased by heat treatment. While they may not be found in high concentrations, the presence of these complement components are important to the development of the neonatal immune system. The authors then sought to determine if whether or not a reduction in abundance of these components also translated to a biological impairment, or a reduction in their circulating concentrations.
Twenty-two Holstein calves were enrolled to be fed either the raw (R, n =11) or heat treated (H, n =11) colostrum at 8.5% of their body weight (0.87 and 0.91 gallons, respectively). Colostrum was placed in a 43°C (104° F) water bath for 20 min to warm to feeding temperature, and fed to calves within 1 hour of birth via an esophageal feeder. None of the calves received colostrum from their own dam. Calves were moved to a group pen (20 calves/pen) 8 h after feeding, where free-choice, heat-treated milk was offered ad libitum, and calves were treated similarly for the remainder of the preweaning period. Blood samples were collected from each calf immediately before colostrum feeding, and at 4, 8 and 24 h after feeding. Weaning weights were collected at a targeted 64 d.
Calves in both groups demonstrated successful passive transfer of antibodies, with serum IgG concentrations above 10 mg/mL. Weaning weights and average daily gain did not differ between the R and H groups, nor did the levels of serum IgA and IgG 24 h after feeding, despite the reduction of both by heat treatment. Insulin levels peaked at 4 h, but differed at 8 h as decline in insulin in group H was slower than that of group R. No differences in IGF-I were detected between groups. Insulin and IGF-I concentrations were of particular interest to the researchers due to the observed reductions in the heat-treated colostrum. 663 unique proteins were also identified in serum samples; a large number of these were noted to have changed in abundance between the 0 and 8 h timepoints, suggesting a change in the calf proteome following colostrum feeding. Of those serum proteins that were increased in abundance, 41% were also identified in the colostrum samples, and were classified as those involved in immune response and coagulation. These results suggest that many of these immunological factors are present in colostrum and help contribute to the establishment of the neonate immune system, and that lowered abundance in the heat-treated batches did not translate to diminished uptake or effect.
While more investigation of the calf proteome and the effects of heat treatment on complement components of the immune system is still necessary, this research continues to support the method of heat treatment for preservation of colostrum quality. Enhancing our understanding of these complement components and proteins, as well as their roles in development, will provide more opportunities to optimize calf health through management and nutrition strategies. Bring on the cold weather, and bring on those warm bottles!
Cari Reynolds earned a BS in Biology from the University of Scranton and a Master of Public Health from the University of Massachusetts – Amherst. After several years working in the public health sector, Cari returned to her agricultural interests and she is currently a research intern at W.H. Miner Institute. Cari is a Ph.D. student in Animal Science at the University of Vermont, where her research will focus on management and preventative strategies to mitigate diseases that impact both human and animal health. She can be reached at reynolds@whminer.com.
References
S. Mann, G. Curone, T. L. Chandler, P. Moroni, J. Cha, R. Bhawal, and S. Zhang. 2020. Heat treatment of bovine colostrum: I. Effects on bacterial and somatic cell counts, immunoglobulin, insulin, and IGF-1 concentrations, as well as the colostrum proteome. J. Dairy Sci. 103: 9368-9383.
S. Mann, G. Curone, T. L. Chandler, A. Sipka, J. Cha, R. Bhawal, and S. Zhang. 2020. Heat treatment of bovine colostrum: II. Effects on calf serum immunoglobulin, insulin, and IGF-I concentrations, and the serum proteome. J. Dairy Sci. 103: 9384-9406.
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