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Differential fates for gluconeogenic precursors in diverging Holstein genotypes.

M. Garcia-Roche

Events

06-23-2020

Abstract:

256
Differential fates for gluconeogenic precursors in diverging Holstein genotypes.
M. Garcia-Roche*1,2, G. Ca�ibe1, D. Talm�n3, A. Mendoza1, C. Quijano2, A. Cassina2, M. Carriquiry1. 1Departamento de Producci�n Animal y Pasturas, Facultad de Agronom�a, Universidad de la Rep�blica Montevideo, Uruguay, 2Departamento de Bioqu�mica, Facultad de Medicina, Universidad de la Rep�blica Montevideo, Uruguay, 3INIA La Estanzuela Colonia, Uruguay.

The aim of the study was to assess the effect of diverging Holstein genotypes in hepatic mitochondrial function and gene expression in a grazing system. Multiparous cows of New Zealand (NZH, n = 10) and North American origin (NAH, n = 10) (512 � 19 vs. 563 � 29 kg BW, 3.1 � 0.1 body condition score (BCS), fall calving) were evaluated during the Spring of 3 consecutive years (2017, 2018 and 2019) to ensure maximum pasture allowance. Cows grazed a mixed pasture of Medicago sativa and Dactylis glomerata (15.4 � 1.0 kg DM/d ha in 2 grazing sessions and were supplemented with 6.9 � 0.5 DM/d of concentrate). Liver biopsies were collected 180 � 17 d postpartum (DPP) and mitochondrial function was assessed measuring oxygen consumption rates using complex I (glutamate/malate: G/M) and complex II (succinate: succ) substrates; gene expression of pyruvate carboxylase (PC) and phosphoenolpyruvate carboxykinase (PCK) was measured by real-time PCR. Data were analyzed using a repeated model that included the genotype as the fixed effect and year and cow as random effects. In average, no differences were observed in solid-corrected milk yield (25.7 vs. 26.4 � 1.2; P = 0.38) or BCS did not differ between genotypes NZH vs. NAH (2.6 � 0.09, P = 0.18). The maximum respiratory capacity - related to the potential reserve capacity that could be used in cases of very high demands or insult - was higher for NZH than NAH (14.3 vs. 11.5 � 1.9, for G/M and 50.2 vs. 26.7 � 9.0 pmolO2/min/mg for succ respectively, P < 0.05). Similarly, oligomycin-sensitive respiration - representing ATP-linked respiration - was higher for NZH than NAH (6.1 vs. 4.3 � 1.9, for G/M and 9.3 vs. 5.2 � 1.1 pmolO2/min/mg for succ respectively, P < 0.05). Both parameters were 3-fold greater for succ than G/M-driven respiration. Both, hepatic PC and PCK mRNA were higher for NAH than NZH cows (1.4 vs. 0.6 � 0.15 and 1.79 vs. 0.74 � 0.24, P < 0.05). Negative correlations were found between succinate-driven respiratory parameters and expression of gluconeogenic genes (r ≥ −0.55, P < 0.05). These results indicate that gluconeogenic precursors may have different metabolic fates: ATP synthesis vs. gluconeogenesis in NZH and NAH cows, respectively.

Keywords: grazing, mitochondria.

Biography: My work is based on elucidating the molecular mechanisms underlying metabolic adaptations during the lactation of dairy cows. I work especifically with energy metabolism, including mitochondrial function, post-translational modifications, gene expression and enzyme activity.