Challenges in poultry nutrition
Today, commercial poultry nutrition no longer encompasses just the ‘pure’ delivery of the nutrients needed by the animals for their preservation, growth and health. It must also be flexible in adapting to changing statutory regulations and keeping up with increasing consumer demands – beginning with eliminating feed of animal origin by using carefully selected raw materials, reducing the use of drugs such as antibiotics, ensuring species-appropriate husbandry practices and, above all, promoting the health of the animals.
Healthy animals are not merely a consumer desire, but the essential starting point for optimal performance and meat quality.
Creatine (Cr, from the Greek ‘creas’, or meat) is a significant component of musculature and a recognised parameter for meat quality (Dahl 1963; Del Campo et al., 1998). By nature, birds eat a varied diet, originally subsisting on plants, grains, insects and small vertebrates. In evolutionary terms, therefore, creatine is a component in the diets of birds. Thanks to the modified composition of poultry feed, i.e. the switch to purely plant-based diets, poultry nutrition today is deficient in Cr. The positive results achieved in terms of the performance, quality and health of poultry using supplements of guanidinoacetic acid (GAA) demonstrate the importance of Cr in poultry nutrition.
The metabolic role of creatine
Cr is an essential molecule, of critical importance for energy balance in cells. It can be synthesised endogenously from the amino acids arginine, glycine and methionine. GAA is produced as an intermediary and immediate precursor in the endogenous Cr-synthesis.
Cr reaches target tissues via the bloodstream (primarily areas with high energy requirements, such as the skeletal muscles and the heart, but also macrophages and spermatozoa), where it is converted via ATP into phosphocreatine (PCr) by phosphorylation and saved as an instantly available anaerobic energy reserve in the cell (Wyss and Kaddurah-Daouk 2000).
When large amounts of energy are required, due to e.g. movement, growth, stress or lack of oxygen, expended adenosine triphosphate (ATP) can be immediately regenerated. The PCr-Cr system therefore works to counter ATP shortage, successive ATP reduction, the formation of free radicals and ultimate cell death effectively and with a high degree of sensitivity (Neumann 2007). On a plant-based diet lacking any Cr, the Cr necessary for muscle contractions and growth has to be covered by endogenous synthesis alone. This is particularly plain to see in those breeds with extremely high growth performance that are now commonplace. However, the Cr/PCr system does not just act as an energy-delivery system for the development of muscle mass; it also has an important function in protecting (muscle) cells (Tokarska-Schlattner et al., 2012).
Creatine in poultry nutrition
Khajali et al. (2020) report Cr levels in typical animal feeds. Cr levels are undetectable in grains, and while fish and meat meals do contain Cr as expected, the levels are lower than what would be expected judging by the raw materials. This is due to, among other things, the low heat resistance of Cr. In conditions such as those that prevail in modern feed production, a considerable loss of natural Cr content must therefore be assumed (Dobenecker and Braun 2015). A study of meat and fish meal (n=38 and 25 respectively) confirms the published values (0.2 g/kg and 1.1 g/kg), while the expected values as calculated from the Cr and water content of the source materials are significantly higher (16.7 g/kg in meat meal and 21.7 g/kg in fish meal (Tab. 1).
Modern, plant-based poultry feed therefore contains no Cr. If 5% fish meal is added, the feed contains just 50 mg Cr per kg of feed (Fig. 3).
Compared to Cr, the endogenous precursor GAA demonstrates high thermal stability (van der Poel et al., 2019 and Khajali et al., 2020), which is why it is established as a synthetic Cr source (Creamino) in animal nutrition. Adding 0.06 to 0.12% GAA provides a comparable Cr boost to feeds of animal origin containing native Cr (Braun 2020).
GAA supplements: improved performance via species-appropriate supply of creatine
It has been shown in a study by Michiels et al. (2012) that fish meal, in contrast to GAA, does not sufficiently increase Cr levels for broilers. ROSS 308 broilers were divided into four feeding groups (maize/soya based, pelletised, experimental duration 39 days): positive control (PC) with 6% fish meal (Cr content: 1.7 g/kg) in the starter phase and subsequently 3% in the grower and finisher phase, negative control (NC), 0.06% GAA and 0.12% GAA.
Results:It was not possible to effect a significant increase in the Cr reserve in breast muscle (Fig. 4) compared with the NC (+3%) using fish meal (PC). Using 0.06% and 0.12% GAA supplements, however, a significant improvement of muscle Cr concentration was achieved (+11% and +16% respectively). The 0.12% supplement also resulted in substantial feed conversion improvements – in the grower phase (p<0.05) in particular, and broadly across the period as a whole (P<0.1). Both GAA and fish meal resulted in an increase in final weight (2.639 kg in NC, 2.707 kg in the 0.12% GAA group and 2.706 kg in the fish meal group (PC). In the fish meal group, this can be attributed to cumulative feed consumption up to d26. The proportion of breast meat was significantly (p<0.05) increased by the GAA supplement (Fig. 5).
In sum, the results of the study can be used to show that the muscle Cr reserves are not in fact sufficiently maximised, and that growth is positively influenced by GAA as a Cr source.
Using carefully produced, Cr-rich food-grade fish meal instead of conventional fish meal improves both Cr levels in the breast muscles and feed intake. In a study involving ROSS 708 animals, this was already evident at 27 days (DeGroot et al., 2019). Specifically, a maize/soya diet (NC) was supplemented with either 7% salmon protein (PC II: Cr content: 14.6 g/kg), 0.12% synthetic creatine monohydrate (PC I), 0.06% or 0.12% GAA throughout the starter and grower phases. For better comparability, the Cr monohydrate diet (PC I) was combined with the negative control (NC) and the GAA groups (salmon protein from PC II unusable). Non-pelletised feed was used due to the heat sensitivity of Cr. PC I, PC II and 0.12% GAA achieved comparable levels of Cr in the feed.
Results: All treatments showed a significant (p<0.001) increase (+15% to 20%) of muscle Cr (Fig. 6) and PCr compared to the NC.
Daily growth (Fig. 7) and feed efficiency (Fig. 8) saw comparable improvement in both the GAA groups and in PC I. The effects in PC II were less pronounced due to lower cumulative feed consumption.
Compared to the results in Michiels et al. (2012), it is clear that muscle Cr can also be enriched using fish meal as a natural feed component, if that feed is produced carefully (limited heat treatment).
Improved muscle creatine: the potential to guard against muscle damage?
Muscular disorders are often characterised by low muscle Cr content (Kley et al., 2013) and Cr has been used to treat myopathies in humans since the late 1990s.
In the areas of animal health and meat quality, pectoral myopathies are more and more frequently becoming production and quality issues (Tasoniero et al., 2016). Intensive efforts to find a way of avoiding this condition have not yet been successful (Baldi et al., 2020). However, studies have shown that wooden breast (WB), white striping (WS) and spaghetti muscle (SM) can be characterised by reduced muscle Cr levels (Soglia et al., 2019). There are indications in current studies being performed by several research groups that GAA supplements can significantly reduce the probability and severity of WB myopathies (Oviedo-Róndon and Córdova-Noboa 2020). For example, Córdova-Noboa et al. (2018), in their study of very heavy (51 days) Ross 708 broilers, examined the influence of different diets (maize/soya or millet/soya) and GAA (0% or 0.06%) on growth and the occurrence of WB and WS myopathies.
Results: GAA supplements led to a significant improvement in terms of final weight and feed conversion; millet produced a lower final bodyweight (Fig. 9).
WB was evaluated on a scale from 1-4 (1: normal, 2: low, 3: moderate, 4: severe) (Fig. 10). An interaction between diet and GAA was identified for the low-grade WB (score 2). With the maize/soya diet, GAA considerably reduced the probability of moderate or severe cases of WB (scores 3 and 4). A score of 1 (no WB) was twice as likely with both types of feed, despite higher final bodyweight, with GAA supplements (p <0.05; Tukey’s test).
Conclusion
The Cr in feed comes from animal proteins, delivered via e.g. fish or meat meal. Modern poultry feed is increasingly deficient in animal proteins, and therefore Cr, thanks to the ever stronger trend towards plant-based poultry nutrition.
GAA makes up the Cr deficiency in feed and improves Cr levels in musculature. An optimal supply of Cr promotes healthy growth and high meat quality.
