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Impact of subclinical mastitis detected in the first month of lactation on milk yield, fertility, and culling of dairy cows on USDA-certified organic herds.

L. Fernandes

Events

06-24-2020

Abstract:

388
Impact of subclinical mastitis detected in the first month of lactation on milk yield, fertility, and culling of dairy cows on USDA-certified organic herds.
L. Fernandes*1, I. Guimaraes1, N. Noyes2, L. Caixeta2, V. Machado1. 1Texas Tech University Lubbock, TX, 2University of Minnesota St. Paul, MN.

It is well established that subclinical mastitis (SCM), characterized by somatic cell count (SCC) > 200,000 cell/mL, has a negative impact on productivity, reproductive performance, and survivability of cows from conventional dairy herds. However, information about the detrimental impacts of SCM in dairy cows from organic herds is scarce. Therefore, our objective was to evaluate how SCM diagnosed during the first month of lactation impacts milk production, fertility and culling of cows on organic farms. Data from 2 USDA-certified organic dairy herds located in Texas and New Mexico were extracted from the farms' database software. A total of 2,716 cows that calved between June 2018 and May 2019 were included in the study. Cows with SCC >200,000 cells/mL in the first month of lactation were considered as having SCM. Statistical analysis was performed using SAS 9.4 (SAS Institute Inc., Cary, NC). Repeated measured ANOVA models were used to assess the effect of SCM on monthly milk production and SCC linear scores. Cox proportional hazards models were used to evaluate the effect of SCM on the risk of pregnancy and culling. The variables lactation group (1, 2, and 3 or greater), herd, twin parturition, and stillbirth were offered to all models. The prevalence of SCM in the first month of lactation was 32.8%. Subclinical mastitis decreased the milk yield during the first 10 mo of lactation. The average milk yield for cows with SCM and healthy counterparts was 33.1 kg/d and 31.8 kg/d, respectively (P < 0.01). Cows with SCM in the first month of lactation had elevated SCC throughout the entire lactation. The average SCC linear score was 4.2 and 2.6 for SCM and healthy cows. Risk of pregnancy was not impacted by SCM (P = 0.44). Cows that had SCM in the first month of lactation were 1.82 times more likely to be culled or die than healthy cows (P < 0.01). In conclusion, SCM in the first month of lactation impairs milk production, increases the risk of culling, but does not impact fertility of dairy cows under organic certified management.

Keywords: organic, subclinical mastitis, milk yield.

Biography: Leticia Martins Fernandes received her Veterinary Medicine degree at University of Sao Paulo, Brazil. She is currently pursuing her Master's degree at the Department of Veterinary Sciences at Texas Tech University and her field of study is mastitis, its risk factors and impacts on organic dairy herds.