Martín Alba, Giráldez F Javier, Cremonesi Paola, Castiglioni Bianca, Biscarini Filippo, Ceciliani Fabrizio, Santos Nuria, Andrés Sonia
Department of Nutrition and Production of Herbivores, Instituto de Ganadería de Montaña, CSIC-Universidad de León, León, Spain.
Institute of Agricultural Biology and Biotechnology, Italian National Research Council, Lodi, Italy.
Front Physiol. 2022 Feb 24;13:840065. doi: 10.3389/fphys.2022.840065. eCollection 2022.
Early feed restriction of lambs may program animals to achieve reduced feed efficiency traits as a consequence of permanent mitochondrial dysfunction. The hypothesis at the background of the present study is that dietary administration of L-Carnitine (a compound that promotes the activation and transportation of fatty acids into the mitochondria) during the fattening period of early feed restricted lambs can: (a) improve the biochemical profile of early feed restricted lambs, (b) improve feed efficiency, (c) modulate the ruminal and intestinal microbiota, and (d) induce changes in the gastrointestinal mucosa, including the immune status. Twenty-two newborn male Merino lambs were raised under natural conditions but separated from the dams for 9 h daily to allow feed restriction during the suckling period. At weaning, lambs were assigned to a control group being fed a complete pelleted diet during the fattening phase (CTRL, = 11), whereas the second group (CARN, = 11) received the same diet supplemented with 3 g of L-Carnitine/kg diet. The results revealed that even though L-Carnitine was absorbed, feed efficiency was not modified by dietary L-Carnitine during the fattening period (residual feed intake, > 0.05), whereas ruminal fermentation was improved [total short-chain fatty acids (SCFAs), 113 vs. 154 mmol/l; = 0.036]. Moreover, a trend toward increased concentration of butyrate in the ileal content (0.568 vs. 1.194 mmol/100 ml SCFA; = 0.074) was observed. Other effects, such as reduced heart weight, lower levels of markers related to muscle metabolism or damage, improved renal function, and increased ureagenesis, were detected in the CARN group. Limited changes in the microbiota were also detected. These findings suggest that L-Carnitine may improve ruminal fermentation parameters and maintain both the balance of gut microbiota and the health of the animals. However, the improved ruminal fermentation and the consequent greater accumulation of intramuscular fat might have hidden the effects caused by the ability of dietary L-Carnitine to increase fatty acid oxidation at the mitochondrial level. This would explain the lack of effects of L-Carnitine supplementation on feed efficiency and points toward the need of testing lower doses, probably in the context of animals being fed in excess non-protein nitrogen.
早期对羔羊进行限饲可能会使动物因永久性线粒体功能障碍而呈现出饲料效率降低的特征。本研究的假设是，在早期限饲羔羊的育肥期，日粮中添加L-肉碱（一种促进脂肪酸激活并转运至线粒体的化合物）能够：（a）改善早期限饲羔羊的生化指标；（b）提高饲料效率；（c）调节瘤胃和肠道微生物群；（d）引起胃肠道黏膜变化，包括免疫状态。22只新生雄性美利奴羔羊在自然条件下饲养，但在哺乳期每天与母羊分离9小时以实现限饲。断奶时，羔羊被分为两组，一组为对照组（CTRL，n = 11），在育肥期饲喂全价颗粒饲料；另一组（CARN，n = 11）接受相同的日粮，但每千克日粮添加3克L-肉碱。结果显示，尽管L-肉碱被吸收，但育肥期日粮添加L-肉碱并未改变饲料效率（剩余采食量，P＞0.05），然而瘤胃发酵得到改善[总短链脂肪酸（SCFAs），113对154毫摩尔/升；P = 0.036]。此外，观察到回肠内容物中丁酸盐浓度有增加趋势（0.568对1.194毫摩尔/100毫升SCFA；P = 0.074）。在CARN组中还检测到其他影响，如心脏重量减轻、与肌肉代谢或损伤相关的标志物水平降低肾功能改善以及尿素生成增加。微生物群也有有限的变化。这些发现表明，L-肉碱可能改善瘤胃发酵参数，并维持肠道微生物群平衡和动物健康。然而，瘤胃发酵改善以及随之而来的肌肉内脂肪积累增加可能掩盖了日粮L-肉碱在线粒体水平增加脂肪酸氧化能力所产生的影响。这可以解释补充L-肉碱对饲料效率缺乏影响的原因，并表明需要在动物过量摄入非蛋白氮的情况下测试更低剂量。
