Abstract
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 ad libitum a complete pelleted diet during the fattening phase (CTRL, n = 11), whereas the second group (CARN, n = 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, p > 0.05), whereas ruminal fermentation was improved [total short-chain fatty acids (SCFAs), 113 vs. 154 mmol/l; p = 0.036]. Moreover, a trend toward increased concentration of butyrate in the ileal content (0.568 vs. 1.194 mmol/100 ml SCFA; p = 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.
Highlights
The developed countries are implementing approaches for more efficient use of resources by the livestock sector, trying to reduce the “feed conversion rate” (FCR: the amount of feed needed to produce one unit of animal product) by improving feed efficiency of the animals under intensive production systems
The higher catabolism of proteins, together with a specific mitochondrial dysfunction causing hypertrophic cardiomyopathy of the heart and increased fat accumulation provoked by a reduction in β-oxidation of fatty acids were identified as likely mechanisms involved in the long-term effects caused by early feed restriction in suckling lambs (Santos et al, 2018b)
The concentration of creatinine decreased in a statistically significant way in the CARN group (0.838 vs. 0.788 mg/dl; p = 0.049), whereas creatine kinase trended toward significant increments (219 vs. 297 U/l; p = 0.062) when feeding carnitine during the fattening period
Summary
The developed countries are implementing approaches for more efficient use of resources by the livestock sector, trying to reduce the “feed conversion rate” (FCR: the amount of feed needed to produce one unit of animal product) by improving feed efficiency of the animals under intensive production systems. It is well known that the efficiency of converting nutrients into gain in sheep is partly under genetic control Still, other factors, such as health status, digestibility, body protein turnover, gain composition, or the rumen’s microbial community, can play a role (Cantalapiedra-Hijar et al, 2018; Santos et al, 2018a,b). Other factors, such as health status, digestibility, body protein turnover, gain composition, or the rumen’s microbial community, can play a role (Cantalapiedra-Hijar et al, 2018; Santos et al, 2018a,b) Many of these factors can be influenced by early nutritional events, giving rise to a new concept called nutritional, metabolic, or developmental programming, which may affect feed efficiency traits during the whole life of the animals (Chavatte-Palmer et al, 2018). The higher catabolism of proteins, together with a specific mitochondrial dysfunction causing hypertrophic cardiomyopathy of the heart and increased fat accumulation provoked by a reduction in β-oxidation of fatty acids were identified as likely mechanisms involved in the long-term effects caused by early feed restriction in suckling lambs (Santos et al, 2018b)
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