Over the last few decades, the reproductive performance of sows has improved considerably based upon advanced genetics, feed formulations and management techniques. The number of piglets born alive is one of the most important criteria, whilst the reduction of stillborn piglets is still an enormous challenge. The substantial increase of total born piglets is a potential productive advantage.
Nevertheless, it usually goes hand-in-hand with a greater birth weight variability and more small and non-viable piglets (0.8-1.1 kg and ≤0.8 kg body weight, respectively). The increase in prolificacy has not been accompanied by a proportional increase in the amount of colostrum, putting piglets with a lower birth weight at a disadvantage.
In recent years, L-carnitine has increasingly been used as a supplement in livestock animals. Trials consistenly demonstrate the beneficial effects of dietary L-carnitine supplementation on performance characteristics in several animal species (pigs, chickens, cattle, horses). Impressive effects of L-carnitine supplementation have been observed in the reproductive performance of sows.
Benefits of carnitine
Various metabolic processes take place in the liver and consequently make good liver function crucial for optimal performance. Carnitine and choline chloride are derived from dietary sources and endogenous synthesis is insufficient to meet the metabolic requirement during gestation.
Both compounds are essential for fat metabolism and transport of fatty acids into the mitochondria. These structures are considered to be the powerhouses of the cells and provide energy. L-carnitine supplementation to sows also stimulates glucose metabolism in the foetuses, providing extra energy for foetal development. This boost results in higher litter weight at birth.
Moreover, the higher milk production largely contributes to a better performance of the suckling piglets.
Improved foetal development
An enhanced efficiency of energy production in the foetus, besides an increased transfer of glucose through the placenta from maternal to foetal blood, contributes to an increase in birth weight. Significantly fewer stillborn, non-viable and small piglets are born following sow supplementation with L-carnitine.
During gestation, the supply of amino acids, glucose, minerals and fatty acids to the foetus from the mother via the placenta is crucial for its development. Elevated maternal carnitine plasma concentrations lead to increased carnitine concentrations in foetal tissues like the liver, skeletal muscle and the heart.
Studies indicate that the effects of carnitine supplementation during gestation could, at least in part, be mediated by alterations of the insulin-like growth factor system. This is a key hormone for intrauterine foetal development and enhances foetal muscle fibre development.
The rate of fatty acid oxidation in the foetus is low. However, immediately after birth, this process becomes extremely important because of the disruption to the supply of glucose and the rapid exhaustion of the glycogen store.
Piglets of sows supplemented with L-carnitine during gestation are able to switch on the oxidation of fatty acids quicker due to their better carnitine status versus the piglets of the control sows. This improves their energy production and in turn, increases suckling persistence during the first days after birth.
Furthermore, piglets born from sows supplemented with L-carnitine have a higher vitality at birth, also providing more vigour to suckle. An improved weight gain, higher litter weights at weaning and a lower pre-weaning mortality rate in piglets originating from sows supplemented with L-carnitine is noted. This favourable effect of L-carnitine supplementation is dose-dependent and is observed in sows across the whole range of parities.
Nutrition during foetal life and birth weights affect animal metabolism and performance in later life, which is also termed 'foetal programming'. Piglets of L-carnitine supplemented sows have more muscle fibres than those of control sows. It has been observed that low birth weights result in lower carcass weights and meat percentages at slaughter compared with high birth weights.
Increased milk production
Sows supplemented with L-carnitine produce more milk than control sows. The improved suckling behaviour of piglets (longer suckling time per day and more vigour) born to L-carnitine supplemented sows causes milk production to rise. Consequently, more energy and nutrients are transferred from the sow to the piglets, with the milk leading to increased litter weights at weaning and lower pre-weaning mortality.
Dietary L-carnitine supplementation of sows during lactation results in an increase of carnitine concentrations in plasma and milk. Milk concentration is important for the development of the suckling piglets because they have a low capacity for endogenous carnitine synthesis, particularly during the first days after birth.
However, in sows that were not supplemented with L-carnitine during gestation, L-carnitine supplementation during lactation did not influence litter weaning weights.
Complementary feed
Carnitol-L (Huvepharma) is a complementary feed. Its liquid and palatable formulation contains high concentrations of L-carnitine, choline chloride, sorbitol and selected plant extracts. These ingredients with hepatoprotective properties especially contribute by:
- boosting metabolic liver function and preventing fatty liver in sows
- optimising the efficiency of energy production from feed
- detoxifying and eliminating harmful waste products
- stimulating the appetite
As a result, Carnitol-L substantially optimises reproductive performance and has no withdrawal time.
Field trials
The benefits of the supplementation of Carnitol-L on the average number of live and stillborn piglets was investigated in a trial in a highly productive Danish sow herd (Table 1).
After entering the farrowing crates, sows received 40 ml Carnitol-L daily in the feed troughs for the last five days prior to farrowing. The daily dose per sow corresponded to 1.2 g L-carnitine, 1.5 g choline chloride and 11.4 g sorbitol. Therefore, a specially developed and adjustable drench fitting on the product container was used (Figure 2)
The average litter data of farrowings before (control) and after the supplementation were recorded and compared. Moreover, data was determined on an annual basis, taking the farrowing index into account.
Carnitol-L supplementation for the last five days before farrowing resulted in:
- An average increase of 0.4 live born piglets/sow/litter, corresponding to 0.95 (=0.4 x 2.38) live born piglets/sow/year (Figure 3)
- An average decrease of 0.37 stillborn piglets/sow/litter, corresponding to 0.88 (=0.37 x 2.38) stillborn piglets/sow/year (Figure 4)
The return on investment was 1:4.8 when comparing the control farrowings with the Carnitol-L supplemented farrowings.
The efficacy of Carnitol-L supplementation was also evaluated in two other trials in Danish sow herds:
- 120 mg L-carnitine/sow/day for the last four weeks of gestation resulted in a significant increase in piglet body weight at birth of 33 g/piglet.
- 60 mg L-carnitine/sow/day for the first 12 weeks of gestation in combination with 120 mg L-carnitine/sow/day for the last four weeks of gestation resulted in a significant reduction in the number of weak-born piglets (-0.75), lower pre-weaning mortality (-0.28 piglets) and higher body weight at weaning (+0.2 kg).
Conclusion
Studies reported in the literature and recent field trials consistently demonstrate that dietary L-carnitine supplementation during gestation increases the reproductive performance of sows. It was concluded that the supplementation of 40 ml Carnitol-L in the last five days prior to farrowing results in a substantial increase in the number of live-born piglets and a decrease in the number of stillbirths.
