A time series analysis of bulk tank somatic cell counts of dairy herds located in Brazil and the United States

• Main Authors: Liz Gonçalves Rodrigues, Maria Helena Cosendey de Aquino, Márcio Roberto Silva, Letícia Caldas Mendonça, Juliana França Monteiro de Mendonça, Guilherme Nunes de Souza
• Format: Article
• Language: English
• Published: Universidade Federal de Santa Maria
• Series: Ciência Rural
• Subjects: bulk tank somatic cell counts; time series; bovine mastitis; Brazil; United States
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-84782017000400451&lng=en&tlng=en

ABSTRACT: Bulk tank somatic cell counts (BTSCC) is widely used to monitore the mammary gland health at the herd and regional level. The BTSCC time series from specific regions or countries can be used to compare the mammary gland health and estimate the trend of subclinical mastitis at the regional level. Three time series of BTSCC from dairy herds located in the USA and the Southeastern Brazil were evaluated from 1995 to 2014. Descriptive statistics and a linear regression model were used to evaluate the data of the BTSCC time series. The mean of annual geometric mean of BTSCC (AGM) and the percentage of dairy herds with a BTSCC greater than 400,000 cells mL-1 (%>400) were significantly different (P<0.05) according to the countries and the times series. Linear regression model used for the USA time series was statistically significant for AGM and the %>400 (P<0.05). The first and second USA time series presented an increasing and decreasing trend for AGM and the %>400, respectively. The linear regression model for the Brazil time series was not significant (P>0.05) for both dependent variables (AGM and %>400). The Brazil time series showed no increasing or decreasing trend for the AGM and %>400. Consequently, approximately 40 to 50% of the dairy herds from southeastern Brazil will not achieve the regulatory limits for BTSCC over the next years.