MaxiFicient™ Boost GF in practice: A new way to drive lean gain in fatteners

Introduction

Today’s pigs grow faster, are leaner, eat less and reach heavier market weights than their predecessors.

These high-performance fatteners need precise nutrition to reach their full genetic potential, for two main reasons:

1. Modern breeds have a greater demand for phosphorus (P) to support lean muscle and bone.
2. Today’s pigs are continuously exposed to pathogens and immune-stimulating antigens (such as vaccines, ammonia and others) that can negatively impact on productivity. This is because pigs adapt by repartitioning nutrients away from growth towards immunity.

On the other hand, there is progressive societal pressure to mitigate the environmental impact of livestock – to reduce antibiotic usage, decrease gas emissions and reduce nutrient waste – at the same time as increasing animal welfare conditions. These factors highlight a need for nutritional programs that support optimal nutrient allocation to muscle deposition, immune competency and bone health – a concept known as adaptive functional nutrition.

This article focuses on the scientific basis of skeletal muscle growth in fatteners and the importance of tailored nutrition for lean muscle deposition. Nutritional strategies that influence skeletal muscle growth are presented, including how a new dsm-firmenich feed solution comprising vitamin D in the form of 25-OH-D3 combined with triterpenoids (MaxiFicient™ Boost GF) can support skeletal muscle growth.

Skeletal muscle

Skeletal muscle development (myogenesis) begins in the prenatal phase as embryonic myogenesis. This defines the number of primary myofibers that are available for postnatal muscle development.

Both pre- and postnatal myogenesis are influenced by specific genes whose expression regulates both the number and size of available myofibers and therefore affects muscle mass. Protein turnover in muscle is a key regulator of muscle mass and is itself regulated by specific genes, including genes involved in the MTOR pathway¹. Maintaining a favorable balance between muscle protein synthesis and breakdown to promote protein deposition is vital for promoting skeletal muscle growth.

Factors that affect muscle deposition

1. Genetics

As mentioned above, one of the main factors affecting muscle deposition is genetics. In the Large White pig population (Figure 1), there has been a strong genetic trend between 1969 and 2015 for increased leanness (+13%), increased growth rate (+200 g/d), reduced feed conversion ratio (-0.6 points) and reduced backfat thickness (-5 mm)².

Alongside these trends, limitations on nitrogen (N) retention have reduced, with <40% of N being retained by fatteners in 1999³ compared with an estimated 56% for high breeding/lean genotype pigs in 2021³.

2. Gender

Protein and muscle deposition are also influenced by gender. Less so in young pigs (< 20 kg) but above this weight both the size of muscle fibers and amount of protein deposited per day are higher in intact males than in gilts or barrows⁴. This is largely due to the effects of testosterone which promotes muscle protein synthesis⁵.

3. Birth weight

Low birthweight piglets have a lower number of primary muscle fibers⁶ resulting in lower prenatal muscle cell proliferation, differentiation and protein accretion during myogenesis. On the other hand, they have faster muscle fiber growth⁷. However, this is not necessarily advantageous because it can be associated with reduced meat quality⁸.

4. Health status

Poor health status, for example following an immune challenge, reduces feed intake and alters protein and energy metabolism. Cytokines involved in muscle breakdown (catabolism) are upregulated whilst those involved in muscle synthesis (anabolism) are downregulated⁹. As a result, nutrients are redirected away from muscle growth towards the immune response, affecting growth performance.

Nutritional strategies for promoting skeletal muscle growth

Nutritional strategies for promoting skeletal muscle growth need to take account of the above-mentioned changes in the growth profile of fatteners (increased feed efficiency and carcass leanness), because this has consequences for nutrient requirements.

This includes the change in amino acid requirements. There has been a delay in the point at which the genetic potential for maximum daily protein deposition (Pdmax) is reached, which now typically occurs beyond 70 kg body weight. This means that amino acid requirements for muscle deposition are now higher during the finisher phase.

Phosphorus availability is another key nutrient for optimizing skeletal muscle development, as illustrated by the direct relationship between whole-body P and N content⁴. This relationship might suggest that muscle deposition could be increased by increasing dietary P. However, environmental concerns over P excretion mean that this is not an option. Instead, phytase inclusion can be used for its proven efficacy in increasing the digestibility of P¹⁰, protein and amino acids¹¹ and enhancing growth performance. The latter includes increased muscle synthesis resulting from the upregulation of genes linked to the MTOR pathway¹².

Ensuring optimal calcium (Ca) availability and balance with P is also important for optimizing skeletal muscle growth. This is because of the key role of Ca in skeletal growth and its close relationship with P in maintaining mineral homeostasis. Excess Ca can compromise P digestibility, limiting muscle and lean deposition¹³, but equally a reduction in total Ca or in the ratio of available Ca to P can increase bone ash but reduce bone mineralization¹⁴, as illustrated in Figure 2.

Vitamin D is a further nutrient that can be used to optimize skeletal muscle growth. The important role of vitamin D in immunity is well described.¹⁵. However, the more recent discovery of vitamin D receptors (VDR) in skeletal muscle cells has led to research demonstrating its involvement in muscle development, strength, function and metabolism, including in protein synthesis¹⁶.

Data are still emerging but there is clear evidence that the more bioavailable form of vitamin D3 known as 25-OH-D3 (supplemented as Hy-D®) can support muscle growth both pre- and postnatally^18–20:

When supplemented to sows, 25-OH-D3 (vs. vitamin D3):

• Increases the number of muscle fibers during embryogenesis¹⁷
• Regulates transcription factors linked to muscle growth in piglets¹⁸
• Upregulates VDR in piglets¹⁹

When supplemented to wean-finish pigs, 25-OH-D3 (vs. vitamin D3):

• Increases average daily gain and final body weight²⁰
• Regulates transcription factors linked to muscle growth²⁰

Finally, triterpenoids that are naturally occurring plant phytochemicals may also be useful as a feed material for promoting skeletal muscle development. Triterpenoids represent an important group of > 20,000 compounds that have proven beneficial anti-inflammatory, antioxidant and antimicrobial effects²¹. In particular, they are used in the treatment and prevention of muscle atrophy in humans²² because they upregulate anabolism and downregulate catabolism in muscle²¹.

MaxiFicient™ Boost GF

dsm-firmenich have recently introduced a new feed solution for fattening swine that combines triterpenoids with 25-OH-D3 (in the form of Hy-D®) called MaxiFicient™ Boost GF. This new feed solution is illustrated in Figure 3. The product is designed to improve feed efficiency and has been shown to support skeletal muscle growth in fattener diets (with associated balancing of Ca and P).

MaxiFicient™ Boost GF when added to low Ca and P diets containing phytase:

• Increases average daily gain during grower-finisher phases and final body weight²⁴
• Tends to improve feed efficiency during finisher phase²³
• Maintains adequate vitamin D status for Ca and P metabolism and bone health²⁴

Conclusions

Tailored nutrition for lean muscle development requires consideration of the greater amino acid requirements of today’s fatteners, and accurate balancing of phosphorus and calcium giving consideration to the contributions from phytase. Vitamin D3 supplementation as 25-OH-D3 can be a useful tool, alongside phytase, for improving muscle growth and performance. In particular, MaxiFicient™ Boost GF, a novel combination of 25-OH-D3 and triterpenoids, is effective in low Ca and P diets containing phytase in supporting muscle growth, improving growth performance and maintaining vitamin D status in fatteners.