Mehaba Nabil, Salama Ahmed A K, Such Xavier, Albanell Elena, Caja Gerardo
Ruminant Research Group (G2R), Animal and Food Science Department, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
Animals (Basel). 2019 Aug 16;9(8):567. doi: 10.3390/ani9080567.
Heat stress causes significant losses in milk production, and nutritional strategies are needed to alleviate its effects. Endogenous carnitine synthesis is also reduced by heat stress (HS). Carnitine plays a central role in fatty acid oxidation and buffers the toxic effects of acyl groups. We hypothesized that carnitine supplementation would make up for any carnitine deficiencies during HS and improve lipid metabolism. The objective was to evaluate rumen-protected L-carnitine (CAR) supplementation in dairy goats under thermo-neutral (TN) or HS conditions. Four Murciano-Granadina dairy goats were used in a four × four Latin square design. Goats were allocated to one of four treatments in a two × two factorial arrangement. Factors were 1) diet: control (CON) or supplementation with CAR (1 g/d); and 2) ambient conditions: TN (15 to 20 °C) or HS (0900 to 2100 h at 35 °C, 2100 to 0900 h at 28 °C). Blood free-, acetyl-, and total-carnitine concentrations increased almost three times by supplementation. Despite this efficient absorption, CAR had no effect on feed intake, milk production or blood metabolites in TN or HS conditions. Heat stress increased rectal temperature and respiratory rate. Additionally, HS goats experienced 26% loss in feed intake, but they tended to eat longer particle sizes. Compared to TN, heat-stressed goats lost more subcutaneous fat (difference in fat thickness measured before and after each period = -0.72 vs. +0.64 mm). In conclusion, supplemented L-carnitine was efficiently absorbed, but it had no lactational effects on performance of goats under thermo-neutral or heat stress conditions.
热应激会导致产奶量显著下降，因此需要采取营养策略来减轻其影响。热应激（HS）还会降低内源性肉碱的合成。肉碱在脂肪酸氧化中起核心作用，并缓冲酰基的毒性作用。我们假设补充肉碱可以弥补热应激期间的任何肉碱缺乏，并改善脂质代谢。目的是评估在热中性（TN）或热应激条件下，给奶山羊补充瘤胃保护型L-肉碱（CAR）的效果。采用四×四拉丁方设计，选用了4只穆尔西亚-格拉纳迪纳奶山羊。山羊被分配到2×2析因排列的四种处理之一。因素包括：1）日粮：对照（CON）或补充CAR（1克/天）；2）环境条件：TN（15至20℃）或HS（0900至2100时为35℃，2100至0900时为28℃）。补充CAR后，血液中游离肉碱、乙酰肉碱和总肉碱浓度增加了近三倍。尽管吸收效率高，但在TN或HS条件下，CAR对采食量、产奶量或血液代谢物没有影响。热应激会提高直肠温度和呼吸频率。此外，热应激山羊的采食量减少了26%，但它们倾向于采食更长颗粒大小的饲料。与TN相比，热应激山羊的皮下脂肪损失更多（每个时期前后测量的脂肪厚度差异=-0.72对+0.64毫米）。总之，补充的L-肉碱吸收效率高，但在热中性或热应激条件下，对奶山羊的生产性能没有泌乳相关影响。
