Nutrient Requirements for Optimal Growth in Broiler Chickens

Broiler chickens are among the fastest-growing farm animals in the world, reaching market weight in just 6-9 weeks. Achieving that rapid growth isn’t accidental – it depends on a precisely formulated diet that delivers the right nutrients at the right time. In India, the Bureau of Indian Standards (BIS) provides well-established guidelines for broiler nutrition, covering everything from energy and protein to vitamins, minerals, and feed additives. Understanding these requirements is fundamental for anyone involved in poultry production.

Two phases of broiler nutrition 🔗

Broiler production is divided into two key feeding phases, each with distinct nutritional requirements. The starter phase covers weeks 0-6, when chicks are growing rapidly and building muscle, bone, and organ tissue. The finisher phase spans weeks 7-9, when birds are adding final body weight before reaching market. According to BIS (1992), the recommendations for various nutrients differ between these phases to match the bird’s changing physiological needs. Getting the phase-specific balance right directly impacts feed conversion ratio (FCR), body weight gain, and overall flock health.

Energy requirements 🔗

Energy is the foundation of any broiler diet. It fuels movement, body temperature regulation, and above all, tissue growth. In broiler nutrition, energy is measured as metabolizable energy (ME) in kilocalories per kilogram of feed (kcal ME/kg).

BIS (1992) recommends energy levels of 2800 kcal ME/kg for the starter phase and 2900 kcal ME/kg for the finisher phase. The slightly higher energy in the finisher diet reflects the bird’s increased body mass and greater maintenance requirements at that stage. The primary energy sources in broiler feed are cereal grains, especially maize, which provides easily digestible carbohydrates. Fats and oils are also included to boost energy density without adding bulk to the feed.

Protein requirements 🔗

Protein is critical for muscle development, feather growth, enzyme production, and immune function. Since broilers are bred specifically for meat production, adequate dietary protein is non-negotiable for achieving target body weights.

BIS (1992) sets protein requirements at 23% for starter feeds and 20% for finisher feeds. The higher requirement during the starter phase reflects the intense muscle and tissue development happening in young chicks. As birds mature, protein requirements drop slightly because growth slows and energy for maintenance becomes a bigger priority.

It’s not just the total protein percentage that matters – amino acid composition is equally important. The concentrations of individual amino acids in broiler nutrition are critical to avoid both deficiency and toxicity. Soybean meal is the most widely used protein source because of its favorable amino acid profile. Fish meal and meat and bone meal are commonly used as complementary sources to fine-tune the amino acid balance.

Mineral requirements 🔗

Minerals may be present in tiny amounts in broiler feed, but their roles are far-reaching – from bone formation and nerve function to fluid balance and enzyme activity. The BIS guidelines specify precise requirements for the three most important dietary minerals in broiler production.

Calcium 🔗

BIS (1992) recommends a calcium level of 1.2% in broiler feed for both starter and finisher phases. Calcium is best known for its role in bone development, but it is equally important for muscle contractions, blood clotting, and nerve signal transmission. Inadequate calcium leads to weak, brittle bones, lameness, and reduced growth rates. Limestone (calcium carbonate) is the most economical and common calcium supplement used in feed formulation.

Phosphorus 🔗

BIS (1992) recommends available phosphorus at 0.5% during both the starter and finisher phases. Phosphorus works alongside calcium in bone formation, and maintaining the correct calcium-to-phosphorus ratio – typically around 2:1 to 2.5:1 – is essential for proper absorption of both minerals. An imbalance in this ratio can impair skeletal development even if total mineral levels appear adequate. Dicalcium phosphate and monocalcium phosphate are the standard phosphorus supplements used in commercial broiler diets.

Sodium chloride (common salt) 🔗

The BIS standard recommends sodium chloride at 0.6% of the diet. Sodium and chloride are essential electrolytes that maintain fluid balance within the bird’s body and support proper nerve impulse transmission and muscle contractions. Broilers are sensitive to both deficiencies and excesses of salt – too little impairs growth and feed intake, while too much causes excessive water consumption and wet litter problems.

Vitamin requirements 🔗

Vitamins are required in very small quantities, but their deficiency can cause severe, sometimes irreversible, health problems in broilers. Vitamins cannot be synthesized by poultry in sufficient amounts and must therefore be provided through the diet. Three vitamins are particularly critical in broiler nutrition: Vitamin A, Vitamin D3, and Vitamin B2 (Riboflavin).

Vitamin A 🔗

Vitamin A is essential for vision, maintenance of epithelial tissues lining the gut and respiratory tract, immune function, and overall growth. Vitamin A is important for eyesight, epithelium surface maintenance, immunological competence, growth, development, and reproduction in chickens. Deficiency leads to poor growth, increased disease susceptibility, and in severe cases, a condition called nutritional roup, where the eyes become crusty and infected. Vitamin A is typically supplemented as retinyl acetate or retinyl palmitate – stable forms that retain potency during feed storage and processing.

Vitamin D3 🔗

Vitamin D3 plays a central role in calcium and phosphorus metabolism. Vitamin D3 is required for the normal absorption and metabolism of calcium and phosphorus, and its deficiency can result in rickets in young growing chickens. Unlike outdoor birds that can synthesize some Vitamin D3 from sunlight, broilers reared in controlled indoor environments are entirely dependent on dietary supplementation. This makes it especially important that D3 levels in feed are carefully monitored. Ergocalciferol (Vitamin D2) is used with an efficiency of less than 10% of Vitamin D3 in poultry and should not be used as a supplement.

Vitamin B2 (Riboflavin) 🔗

Riboflavin is a water-soluble B vitamin that acts as a coenzyme in energy metabolism, helping broilers efficiently convert dietary carbohydrates and fats into usable energy. Given the high growth rates and energy demands of broilers, an adequate riboflavin supply is critical for maintaining good feed conversion efficiency. Riboflavin deficiency in broilers can cause curled-toe paralysis, where the toes curl inward and birds struggle to walk, directly affecting their access to feed and water. This condition, if left uncorrected, severely compromises growth performance and bird welfare.

It is worth noting that supplementing broiler feed with higher vitamin levels than the minimum recommendations results in better production performance, health, welfare, and carcass quality, particularly under commercial field conditions where birds face environmental stress, disease challenges, and variable feed quality.

Feed additives: antibiotics and probiotics 🔗

Beyond core nutrients, broiler diets often include feed additives designed to improve growth performance, feed efficiency, and gut health. Feed additives used in poultry feed include antibiotics, probiotics, oligosaccharides, enzymes, and organic acids, included in the diet for promoting growth through their potential effect in increasing feed intake.

Antibiotics as growth promoters 🔗

Antibiotics are widely used feed additives to enhance growth rate, feed conversion, poultry immunity, and productivity, besides preventing infections. Antibiotic growth promoters (AGPs) work by suppressing sub-clinical gut infections and reducing the energy the bird spends on immune responses, freeing up nutrients for growth. However, growing global concerns about antibiotic resistance have led many countries to restrict or ban their use as routine growth promoters. The use of antimicrobials in livestock feed has been identified as a major contributing factor in the emergence and spread of antimicrobial resistance.

Probiotics as a sustainable alternative 🔗

Probiotics are live, non-pathogenic microorganisms that support gut health when administered in adequate amounts. Probiotics are reported to improve growth, production performance, immunity, and digestibility, while safeguarding gut microflora and enhancing egg and meat quality traits. Common probiotic strains used in broiler feeds include Lactobacillus, Bacillus subtilis, and Bifidobacterium species.

Research supports their effectiveness. Probiotic feeding induced the highest level of growth performance and immunity response in broilers, while antibiotic feeding delayed maturation of intestinal microbiota. A study comparing probiotics and antibiotics in broilers found that body weight was significantly higher in the probiotic group at multiple time points during the rearing period. These findings position probiotics as a promising, science-backed alternative to antibiotic growth promoters in modern broiler production.

Putting it all together: practical feed formulation 🔗

Meeting BIS nutrient guidelines requires more than just knowing the numbers – it requires sourcing quality ingredients, maintaining consistent mixing ratios, and regularly testing finished feeds. The BIS nutrient requirements are guidelines, and professional veterinary advice should always be sought before finalizing a feed formulation. Key performance indicators such as daily weight gain, feed conversion ratio, and flock mortality rates serve as practical signals for whether the nutritional programme is on track. If FCR begins to decline or growth slows unexpectedly, a nutritional deficiency is often the first place to investigate.

Whether you are formulating feed at a commercial feed mill or managing a farm-level mixing operation, keeping the BIS framework as your baseline – and adjusting for local ingredient quality, environmental conditions, and bird genetics – remains the most reliable approach to cost-effective, high-performing broiler production.

What do you think? As antibiotic resistance becomes a growing concern in global food systems, how quickly do you think the Indian poultry industry will fully transition to probiotic-based feed programmes? And with broiler genetics improving every year, should the BIS nutrient guidelines be updated more frequently to reflect the needs of modern fast-growing strains?

References

1. https://archive.org/details/gov.in.is.9863.1992
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