MONITORING THYROID HORMONES, SOME OF OXIDATIVE STRESS MARKERS AND BIOCHEMICAL CHANGES DURING THE EARLY AND MID STAGE OF LACTATION IN DAIRY COWS

Ghada Mohamed ,Gaadee H.i M

doi:10.21608/avmj.2019.168922

Abstract

This study aimed to compare changes in biomarkers of nutrient metabolism, thyroid hormones and oxidative stress parameters present during the early (EL) and mid-lactation (ML) stages in dairy cows reared under the hot summer conditions at Assiut city, Upper Egypt. Blood serum of twenty nine multiparous clinically healthy lactating Holstein Fresien cows (16 early lactating and 13 mid lactating cows) belonged to a private farm located under the same temperatures and living conditions were used in this study.Cows of ML had significantly lower values (P 0.05). Similarly, non-significance differences (P> 0.05) were found between the two lactation stages for thyroid hormones (Triiodothyronine, Thyroxine). For oxidants/antioxidant parameters, ML cows had significantly decreased values (P 0.05) for Malondialdehyde concentrations and catalase activity. Pearson’s correlation coefficients between the metabolic parameters, thyroid hormones and oxidative indices in early and mid-stages of lactation showed different positive and also negative correlations. Can be concluded that this study gives evidence that the lactating cows undergo a substantial oxidative stress that related to metabolic and physiological adaptation during early lactation to mid lactation stages under the under the influence of high temperature conditions at Upper Egypt.

Highlights

The lactation periods in dairy cows are especially critical and present considerable physiological challenges to homeostasis by imposing significant metabolic stressors that may contribute to the onset of diverse disorders (Castillo et al, 2005)
Adaptation of the endocrine system during the lactation period, primarily the thyroid gland is the key factor in maintaining metabolic balance Since, thyroid hormones play an important role in the ketosis pathogenesis (Djokvic et al, 2014), their impairment is an indicative parameter for these metabolic stresses
Significance differences was shown between two stages of lactation, where the mid lactation stage had a lower values than the early lactation stage for glucose and total cholesterol concentrations (P

Summary

Introduction

The lactation periods in dairy cows are especially critical and present considerable physiological challenges to homeostasis by imposing significant metabolic stressors that may contribute to the onset of diverse disorders (Castillo et al, 2005). Lactation causes negative energy balance and high mobilization of lipids from body fat reserves immediately before and after parturition as well as during the first stage of lactation in dairy cows (Reist et al, 2002), either in ewes leading to decline in animal productive and reproductive performance (Morgante et al, 2012) Due to these metabolic stresses which severely influence animal welfare causing so called production diseases like ketosis, hypocalcaemia (Ceciliani et al, 2018) or fatty liver and lipogenesis in the liver (Šamanc et al, 2010) rather than imbalance in hepatic carbohydrate (Goff and Horst, 1997). Adaptation of the endocrine system during the lactation period, primarily the thyroid gland is the key factor in maintaining metabolic balance Since, thyroid hormones play an important role in the ketosis pathogenesis (Djokvic et al, 2014), their impairment is an indicative parameter for these metabolic stresses

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