Performance of Canchim calves naturally infested with Rhipicephalus microplus associated with histamine levels and bovine anaplasmosis

• Grant number: 25/04688-4
• Support Opportunities: Scholarships in Brazil - Master
• Start date: July 01, 2025
• End date: April 30, 2027
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Genetics and Improvement of Domestic Animals
• Principal Investigator: Rodrigo Giglioti
• Grantee: Geovana Menegão de Souza
• Host Institution: Instituto de Zootecnia. Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Nova Odessa , SP, Brazil
• Associated research grant: 22/16262-3 - Indicators of resistance to the Rhipicephalus microplus tick and babesiosis in Canchim cattle: new strategies., AP.R

Abstract

Infestations by the cattle tick Rhipicephalus microplus represent a major source of losses for Brazilian livestock. Additionally, this tick is responsible for transmitting Anaplasma marginale, which also directly impacts herd health and the economics of cattle farming. Therefore, the objective of this study is to evaluate, from weaning, 70 Canchim calves (approximately 35 males and 35 females) for their resistance and resilience to tick infestations, associated with performance measures (weight and weight gain), health (hematocrit), levels of infection by A. marginale, and histamine levels. The animals will be evaluated over a 12-month period (April 2025 to March 2026), with two observations each season, totaling six evaluations. During each evaluation, two tick counting methods will be used: counts of adult females (¿ 4.5 mm) on the left side of each animal and scoring (0 - 4), which considers all visible life stages of the tick for counting. Simultaneously with tick counts, the animals will be weighed on a digital scale, and blood samples will be collected for DNA and RNA extraction, and to determine the packed cell volume percentage. DNA samples will be subjected to quantitative PCR (qPCR) assays to detect and quantify the levels of infection by A. marginale, while RNA samples will be used to determine the levels of histamine gene expression, respectively. Performance and health measures (weight, weight gain, and packed cell volume) and histamine gene expression levels will be associated with anaplasmosis infection levels and tick counts using mixed regression models with repeated measures from the same animal. The influence of tick infestations, anaplasmosis levels, and histamine expression on animal performance will be assessed for resistance and resilience. This evaluation will allow the identification of individuals with superior traits, whose results can be incorporated into Canchim breed genetic improvement programs, as well as provide support for similar research in other cattle breeds. This project will be linked to the FAPESP Regular Aid process no. 2022/16262-3, entitled 'Indicadores de resistência ao carrapato Rhipicephalus microplus e às babesioses em bovinos da raça Canchim: novas estratégias'. (AU)