Impact of dry-off somatic cell count from cows on colostrum quality and composition, and on bacterial diversity, health and performance of dairy calves.

• Grant number: 22/04990-4
• Support Opportunities: Scholarships in Brazil - Doctorate
• Effective date (Start): October 01, 2022
• Effective date (End): February 28, 2025
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Carla Maris Machado Bittar
• Grantee: Cristiane Regina Tomaluski
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Due to the importance of health and performance during the initial phase of development and throughout the productive life of cattle, the production and supply of high-quality colostrum is essential for the success of this production chain. For this reason, understanding factors that may interfere with colostrogenesis or the process of passive immunity transfer is becoming increasingly necessary. The objective of this research is to evaluate the quality, the microbiome, the incidence of resistant pathogens, and the presence of antimicrobial residues in bovine colostrum from cows with different somatic cell counts (SCC) on drying, as well as the impact of consumption of this colostrum on the microbiome, health, metabolism, and performance of dairy calves during the lactation phase. For this study, two experiments will be carried out. In the first experiment, 60 cows will be divided into two groups: high (>500 thousand cells/mL) or low (<200 thousand cells/mL) CCS in drying. Once a month, during the three months before drying and on the day of drying, milk samples will be collected to monitor the animals' CCS and CTP values and distribution to the groups. Cows will undergo abrupt drying 60 days before the expected calving date. After parturition, colostrum samples and transitional milk (3rd day postpartum) will be collected to evaluate the immunological and microbiological quality, antimicrobial residues, antimicrobial-resistant microorganisms, and the microbiome (bacterial diversity). For the 2nd experiment, 40 calves from the cows used in experiment 1 will be used, blocked according to birth weight, date of birth, and sex. The calves will be fed fresh colostrum from their dams (high or low CCS on drying) and with high quality (> 50 mg/mL) in a volume of 10% of live weight within the first two hours and a further 5% within 6-8 hours after birth. After colostrum, all will be in the same conditions, receiving 6 L/day of whole milk and ad libitum access to water and starter concentrate. Blood samples will be collected at 0 and 24 hours to evaluate the transfer of passive immunity and apparent efficiency of absorption. At 0, 24, 48, and 72 hours, blood samples will be collected for erythogram, leukogram, and hematocrit determination, and the concentrations of glucose, protein, lactate, and non-esterified fatty acids. Likewise, weekly blood samples will be performed to trace the biochemical and metabolic profiles. Intestinal permeability test will be performed at weeks 1, 2, 3, and 4 to assess intestinal health and the occurrence of leak gut. Also, to assess intestinal health and its microbiome, five animals will be slaughtered per treatment for 1 day, and five more at 21 days of age for organ weighing, collection of segments, and intestinal contents. Stool samples will be collected at 1 and 21 days to evaluate bacterial diversity and microbial resistance. Consumption and fecal score will be monitored daily, while weekly weight gain will be assessed. Data will be analyzed using PROC MIXED of the SAS statistical package (version 9.0, SAS Institute Inc., Cary, NC).