Abstract

Temperamental cattle tend to yield carcasses of poorer quality, and Brahman cattle are reportedly more temperamental than non-indicus cattle breeds. A potential link between temperament and product quality may be mitochondrial activity. We hypothesized that mitochondrial measures would be greater in temperamental compared with calm heifers and that the relationships between temperament and mitochondria would persist as heifers age. Serum cortisol and skeletal muscle (longissimus thoracis [LT] and trapezius [TRAP]) mitochondrial profiles and antioxidant activities were quantified from the same calm (n = 6) and temperamental (n = 6) Brahman heifers at 8, 12, and 18 mo of age. Data were analyzed using a mixed model ANOVA in SAS (9.4) with repeated measures. Serum cortisol was greater in temperamental compared with calm heifers throughout the study (P = 0.02). Mitochondrial volume density (citrate synthase [CS] activity) increased over time (P < 0.0001) but was similar between temperament and muscle groups. Mitochondrial function (cytochrome c oxidase activity) was greatest in the temperamental LT at 8 mo of age (P ≤ 0.0006), greatest in the temperamental TRAP at 18 mo of age (P ≤ 0.003), and did not differ by temperament at 12 mo of age. Integrative (relative to tissue wet weight) mitochondrial oxidative phosphorylation capacity with complex I substrates (P_CI), P_CI plus complex II substrate (P_CI+II), noncoupled electron transfer system capacity (E_CI+II), and E with functional complex II only (E_CII) were greater in the TRAP than LT for calm heifers at all ages (P ≤ 0.002), but were similar between muscle groups in temperamental heifers. Overall, calm heifers tended to have greater intrinsic (relative to CS activity) P_CI and flux control of P_CI+II (P ≤ 0.1) than temperamental heifers, indicating greater utilization of complex I paired with greater coupling efficiency in calm heifers. Within the LT, integrative P_CI+II was greater (P = 0.05) and E_CI+II tended to be greater (P = 0.06) in temperamental compared with calm heifers. From 8- to 18-mo old, glutathione peroxidase (GPx) activity decreased (P < 0.0001) and superoxide dismutase activity increased (P = 0.02), and both were similar between muscle groups. The activity of GPx was greater in temperamental compared with calm heifers at 8 (P = 0.004) but not at 12 or 18 mo of age. These results detail divergent skeletal muscle mitochondrial characteristics of live Brahman heifers according to temperament, which should be further investigated as a potential link between temperament and product quality.

中文翻译：

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气质影响 8 至 18 个月龄婆罗门小母牛骨骼肌中的线粒体能力。

摘要

脾气暴躁的牛往往会产出质量较差的屠体，据报道，婆罗门牛比非印度牛品种更脾气暴躁。气质和产品质量之间的潜在联系可能是线粒体活动。我们假设，与平静的小母牛相比，气质小母牛的线粒体测量值更大，并且随着小母牛年龄的增长，气质和线粒体之间的关系将持续存在。对 8、12 和 18 个月时相同的冷静 ( n = 6) 和气质 ( n = 6) 婆罗门小母牛的血清皮质醇和骨骼肌（胸最长肌 [ LT ] 和斜方肌 [ TRAP ]）线粒体谱和抗氧化活性进行了量化年龄。使用 SAS (9.4) 中的混合模型方差分析并重复测量来分析数据。在整个研究过程中，与冷静的小母牛相比，脾气暴躁的小母牛的血清皮质醇更高（P = 0.02）。线粒体体积密度（柠檬酸合酶 [ CS ] 活性）随着时间的推移而增加 ( P < 0.0001)，但气质和肌肉群之间的情况相似。线粒体功能（细胞色素C氧化酶活性）在 8 个月龄时气质型 LT 中最高（P ≤ 0.0006），在 18 个月龄时气质 TRAP 中最高（P ≤ 0.003），并且在 12 个月时气质型 TRAP 中线粒体功能（细胞色素 C 氧化酶活性）没有差异。年龄。综合（相对于组织湿重）线粒体氧化磷酸化能力与复合物 I 底物 ( P _CI )、PC _I加复合物 II 底物 ( P _CI+II )、非偶联电子传递系统能力 ( E _CI+II ) 和 E 与功能性对于所有年龄段的平静小母牛，仅复合体 II ( E _CII ) 在 TRAP 中的值高于 LT ( P ≤ 0.002)，但在喜怒无常的小母牛的肌肉群之间相似。总体而言，平静的小母牛往往比脾气暴躁的小母牛具有更大的内在（相对于 CS 活动）P _{CI和 P CI+II}通量控制（P ≤ 0.1），这表明平静的小母牛对复合物 I 的利用率更高，耦合效率更高。在 LT 内，与平静的小母牛相比，气质小母牛的综合 P _CI+II更大（P = 0.05），E _CI+II往往更大（P = 0.06）。从8个月大到18个月大，谷胱甘肽过氧化物酶（GPx）活性下降（P <0.0001），超氧化物歧化酶活性增加（P= 0.02），并且肌肉群之间的情况相似。与平静的小母牛相比，8 岁时 GPx 的活性更高（P = 0.004），但在 12 或 18 月龄时则不然。这些结果根据气质详细描述了活婆罗门小母牛的不同骨骼肌线粒体特征，应进一步研究其气质与产品质量之间的潜在联系。