The effect of high dose ascorbic acid and high dcad administration on oxidative stress and mammary gland function of dairy goat fed under tropical condition
Authors:   , Semsirmboon Sapon 
Published: September 2023

High ambient temperature (HTa) increased the respiration rate (RR) and rectal temperature (Tr) of dairy goats. The excess response resulted in acid-base imbalance, electrolyte imbalance, and systemic oxidative which could indirectly affect the mammary gland. Besides, HTa did directly alter cell function, and this has been proposed to be mediated by oxidative stress. We previously showed that high dietary cation and anion differences (DCAD) could decrease the HTa effect. In dairy cows, a high dose ascorbic acid (Asc) has been used to decrease oxidative stress. Then, It was hypothesized whether mammary gland function could be altered when the HTa was alleviated by DCAD and Asc supplements. This current study consisted of two main experiments. The first aimed to investigate the Asc supplement protocol in dairy goats while the second was planned to investigate the hypothesis. The first and second experiments were carried out on six non-lactating goats and twelve lactating goats, respectively. During these experiments, the ambient condition, RR, and Tr were measured three times a day, at 0600, 1300, and 1800. All samples were collected at 1500 of both experiments. In the first experiment, goats were intravenously supplemented with vehicle and Asc on the last two days of the experiment and only blood samples were used to analyze blood gas, electrolytes, and oxidative stress. In the second experiment, goats were randomly assigned to control and DCAD groups which were fed with the control diet and a high DCAD diet for 8 weeks. The protocol of Asc supplement was done on the last two days of the 4th and 8th weeks of the experimental period. On these supplemented days, blood and urine were collected to measure blood gas, electrolytes, and renal function, while both milk composition and plasma oxidative stress were measured only on the 8th of the experimental period. The ambient condition showed that all goats were fed under HTa, while an increased RR and Tr indicated heat dissipation. In the first experiment, Asc tended to decrease hematocrits which might be mediated by depleted oxidative stress. Then, this protocol was then used in the second experiment. On the 4th week of the second experiment, RR, blood pH and bicarbonate were higher in the DCAD group compared with the control group. These DCAD effects were no longer observed on the 8th week of this study when fraction excretion of electrolyte was increased in the DCAD group. The presence of both supplements synergistically depleted plasma creatinine and malondialdehyde. The depletion of plasma malondialdehyde was observed with the alteration of milk composition. Based on these data, the high DCAD and high dose Asc synergistically increased body water but decreased oxidative stress. The depletion of oxidative stress altered the mammary gland function of dairy goats. Therefore, the presence of high DCAD and high dose Asc supplement did synergistically alleviate the HTa effect on mammary gland function of lactating goat fed under tropical condition.