Ram Singh Bibyan, Suruchi Damor, Aaishwarya C Javanjal, Leander Toijam, Sumit B Kundir, Vivek V Chandapure, Ashutosh, N Mahalle, Ankit Panwar and Bommana R Prasad
Animal Nutrition Division
ICAR- National Dairy Research Institute
Karnal-132001 (Haryana) India
Email: carirsingh@yahoo.co.in
+91-9457602079
The objective of scientific feeding of broiler chickens is to achieve good growth and feed conversion efficiency, good skeletal health and survivability and quality meat at shorter period of time as per nutrient requirements. A simple definition of dietary nutrient requirement is the daily amount of a nutrient necessary to meet a healthy animal’s needs for maintenance, activity, growth and reproduction without any change in body reserves. The term “requirement” suggests that there is a fixed amount of a nutrient required by an animal where no further increase in performance will occur when an animal is fed an additional amount of that nutrient. Although, nutrient requirement is expressed accurately in gram per kg of live weight, but in case of poultry group feeding is done and the nutrient requirement is expressed in terms of percent or per kg feed. The CP requirement is expressed as CP percentage and energy is expressed as Metabolisable Energy (ME) kilo calorie /per kg feed. ME is used to express energy requirement because it is easier to estimate the losses of energy through faeces and urine in combination since there is a common opening for faecal and urinary losses called as cloaca and it is difficult to separately estimate the faecal losses only. Feeding scientifically, broilers grow at a rapid rate and reaches to about 1.8 to 2.0 kg at 5 weeks of age with an average feed conversion of 1.5-1.8 kg at 2 kg live weight.
Growth phases of broiler chickens: The broilers are generally reared under three phases, i.e. 0-10/14d (pre-starting phase) and 10/14-21/24d (starter phase) and after 21/24d of age (finishing period) or even upto 8 weeks of age to produce larger broilers (roasters). The large broilers are suitable for production of different value added products. The basic purpose of phasing out is to provide nutrients as per need depending upon the growth rate and type of growth. During pre-starter and starter phases the growth is at fastest rate (about 15 to 20 times of initial body weight) and the growth is mainly due to deposition of protein and minerals. Thereafter, during finishing phase, the growth rate is about 2 to 3 times of its weight on 21st day and the growth is mainly due to protein, minerals and fat. After 6 weeks of age the growth of protein and minerals continues but their rate of deposition is decreased, while fat deposition rate is further increased. Therefore, more of protein, amino acids and minerals per unit energy is required during pre and starting phase, and with age their concentration in diet is decreased. The concentration of energy is rather increased with age. Feed conversion efficiency (FCE) is an important parameter in broiler production. FCE of the young chick (0 to 3 weeks of age) is largely dependent upon adequate amino acid nutrition, while in the older broilers (3-6/9 weeks of age) it is more dependent upon dietary ME. This is the reason that a gradual increase in dietary energy with increasing broiler age and body weight is advisable.
Energy in broiler diets: The poultry industry is a major consumer of energy in the form of cereals, protein cakes/meals and edible oils.Energy is the most expensive part of poultry diet and is also the most wasted. Therefore, accurate measurement of dietary energy is of economic importance to the poultry industry. As the broilers grow at rapid rate, the concentration of all the nutrients in their diets is higher to support conversion of feed nutrients to body tissues. They require high energy as carbohydrates and fat, and also protein. But to prevent utilization of protein for energy, energy to protein ratio should be maintained. Increasing the dietary energy level causes increased gain and improved feed efficiency. Increasing the dietary energy concentration does not affect total feed intake but increases total energy intake as long as the birds are responding positively to energy. However, meeting the energy requirement is the major limitation in broiler feeding. The reasonable energy levels in broiler diet range from 2800 to 3200 kcal ME per kg diet depending upon increased cost to meet energy requirement, ambient temperature, and type of meat required. At low level of dietary energy, the broilers are unable to meet requirement even by increasing feed intake to compensate energy intake resulting poor growth and feed conversion. High energy diet also leads to fat deposition in abdominal cavity, but the effect is more pronounced when energy to protein or limiting amino acids is wider. It means abdominal fat deposition is more in high energy and low protein diet. High density diet adequately balanced in energy and protein improves gain and feed conversion but may not increase abdominal fat pad.
Use of fats and oils in broiler diets: A starter diet with about 2850 kcal ME per kg and finisher diet with about 2950 kcal ME per kg can be formulated using maize-soybean meal without addition of fat. However, in order to increase the energy in diet beyond this limit it is necessary to add fat in diets. Moreover, to give a pleasant appearance in market broilers and to improve the meat quality, slight fat deposition is warranted. Replacement of one kg maize by fat or oil makes difference of about 50 kcal ME per kg diet. Addition of fat in diets reduces the heat increment, which is beneficial not only to reduce heat increment in extreme hot climate but also to compensate energy intake as ambient temperature is increased. However, the energy to limiting amino acids ratio should be adjusted to achieve good growth, feed conversion and welfare by reducing heat increment. The maximum effective level of fat in diet is 8% as upto this level it does not exert adverse effect on utilization of minerals and has extra-calorific effect. Generally, a total of 3 to 4 % fat comes from dietary origin and there is scope of adding 4 to 5% fat in broiler diets. However, the usefulness of fat is determined by the cost of production.
Protein and amino acids in broiler diets: The concentrations of essential amino acids are more important than protein as such. The dietary protein levels for broilers should be in between 21 to 23% during starting and 18-21% during finishing period at energy level of 3000 to 3200 kcal ME per kg in both the phases. Calorie-protein ratio must be maintained for effective utilization of protein as well as amino acids. Ambient temperature and age at marketing of broilers determine calorie-protein ratio. Faster growth is achieved when the protein level is increased i.e. at lower calorie to protein ratio. The specifications for energy to protein ratio for temperate climate is wider, while that for tropical climate it is narrower. The concentrations of amino acids especially of limiting amino acids are important. The first , second and third limiting amino acids in diets based on maize- soybean meal is methionine (or methionine plus cystine), lysine and threonine. While, these are in lysine, methionine, arginine and tryptophan in order of deficiency in groundnut meal-fish meal- maize based diets. The optimum lysine concentration varies from 1.10 to 1.30% in starting diets (0-3 weeks) and 1.00 to 1.20% in finisher diets (3-6 weeks). Thereafter (6-9 weeks) the requirement varies from 0.75 to 0.85% for optimum growth and feed conversion ratio. The requirements of methionine and methionine plus cystine for the corresponding phases are 0.48 –0.50% and 0.75-0.90%, 0.38-0.45% and 0.78-0.88%, and 0.32-0.35% and 0.60-0.72%. The threonine requirements are 0.75-0.80%, 0.60-0.70% and 0.59-0.68% for 0-3, 3-6 and 6-9 weeks of age, respectively. The amino acid arginine is though not limiting, but its concentration affects utilization of lysine. Thus, arginine concentration needs to be considered. The requirements of arginine are 1.18-1.25%, 0.97-1.10% and 0.83-1.0% for the corresponding phases of broiler growth.
Vitamin and mineral requirements: As diets of broiler chickens are higher in energy and proteins, the requirements of vitamins and minerals are also higher to support rapid growth including mineral growth, and metabolism of nutrients. Vitamin A, riboflavin and vitamin D3 are the most limiting vitamins in practical broiler diets. Other water soluble vitamins are also added as per requirements, however, their dietary supply may be reduced to half after 3 weeks of age when reared on litter (broilers are generally reared on litter). The requirements of calcium is 0.9 to 1.2%, while available phosphorus requirements are 0.45-0.50% during starting period, 0.40-0.45% during 21 to 42 days of age and 0.35% to 0.40% thereafter. Meeting the calcium and phosphorus requirement is critical as judicious use of calcium provides space to increase energy in diet, while phosphorus supplementation required costlier dicalcium phosphate. The cost of vitamins and minerals are about 5 to 8%.
Feed additives: Certain feed additives or growth promoters viz. antibiotics, coccidiostats, enzymes, probiotics, antioxidants etc. can be added in diets as per recommended dose depending upon need. Under commercial environment, the birds are always exposed to infection. Antibiotic feed additives (zinc bacitracin, verginiamycin, aureomycin, etc. which are not used for therapeutic/treament purpose) not only prevent birds from subclinical infection, but also promotes growth and reduce stress. These additives are beneficial only when the broilers are kept under poor hygienic condition and with diets marginally deficient in micronutrients. The antibiotic feed additive must be withdrawn from diet one week prior to sacrifice of the birds. A coccidiostat (amprolium, bifuran, neftin, madhuramycin, monensin and many more anticoccidial feed additives are available in market) is must in diet especially when the litter is moist. If the litter is perfectly dry, it may be omitted from diet. The antioxidants (ethoxyquin, BHT, BHA, etc.) are required when high energy diet is compounded adding fats or oils. Enzymes may be added in high fibre diets but their effect is always not consistent and are yet to be standardized.
Feeding of broilers: Broiler chicks are fed ad libitum from day-old to the age of sacrifice. Light is provided to encourage feed intake. Frequent feeding (two to three times) of broilers is beneficial not only to encourage feed intake but also to prevent feed wastage. A whole mash feeding or pellet/crumble feeding is followed. The birds grew faster (by about 10%) and have better feed utilization efficiency (by about 5-8%) when pellet feed is used. However, the birds become more prone to ascites when pelleted feed is offered.
Table.1 Nutrients requirements of broilers as percent or unit per kg of diet (90% DM basis) as suggested by NRC (1994) & modified at different energy levels (2900 & 3000 Kcal/kg):
| 0-3 weeks | 3-6 weeks | 6-8 weeks | ||||||
| Energy kcal | 3200 | 3000 | 2900 | 3200 | 3000 | 2900 | 3200 | 3000 |
| CP % | 23.0 | 21.56 | 20.84 | 20.0 | 18.75 | 18.10 | 18.0 | 16.9 |
| Arginine % | 1.25 | 1.17 | 1.13 | 1.10 | 1.03 | 1.00 | 1.0 | 0.94 |
| Lysine % | 1.10 | 1.03 | 1.00 | 1.00 | 0.94 | 0.91 | 0.85 | 0.80 |
| Methionine % | 0.50 | 0.47 | 0.45 | 0.38 | 0.36 | 0.35 | 0.32 | 0.30 |
| Meth + cyst % | 0.90 | 0.85 | 0.82 | 0.72 | 0.68 | 0.66 | 0.60 | 0.56 |
| Threonine % | 0.80 | 0.75 | 0.725 | 0.74 | 0.70 | 0.68 | 0.68 | 0.64 |
| Tryptophan % | 0.20 | 0.19 | 0.18 | 0.18 | 0.17 | 0.16 | 0.16 | 0.15 |
| Linoleic acid % | 1.00 | 0.94 | 0.91 | 1.00 | 0.94 | 0.91 | 1.0 | 0.94 |
| Calcium % | 1.00 | 0.94 | 0.91 | 0.90 | 0.84 | 0.81 | 0.80 | 0.75 |
| *NPP % | 0.45 | 0.42 | 0.41 | 0.35 | 0.33 | 0.32 | 0.30 | 0.28 |
| Sodium % | 0.20 | 0.19 | 0.18 | 0.15 | 0.14 | 0.14 | 0.12 | 0.11 |
| Chloride % | 0.20 | 0.19 | 0.18 | 0.15 | 0.14 | 0.14 | 0.12 | 0.11 |
| Copper mg | 8.0 | 7.50 | 7.25 | 8.0 | 7.5 | 7.3 | 8.0 | 7.5 |
| Iodine mg | 0.35 | 0.33 | 0.32 | 0.35 | 0.33 | 0.32 | 0.35 | 0.33 |
| Iron mg | 80 | 75 | 72.5 | 80 | 75 | 73 | 80 | 75 |
| Manganese mg | 60 | 56 | 54 | 60 | 56 | 54 | 60 | 56 |
| Selenium mg | 0.15 | 0.14 | 0.13 | 0.15 | 0.14 | 0.14 | 0.15 | 0.14 |
| Zinc mg | 40 | 37.5 | 36.25 | 40 | 38 | 37 | 40 | 37.5 |
| Vit A IU | 1500 | 1400 | 1360 | 1500 | 1400 | 1350 | 1500 | 1410 |
| VitD3 ICU | 200 | 190 | 180 | 200 | 190 | 185 | 200 | 188 |
| VitE IU | 10 | 9.5 | 9.0 | 10 | 9.5 | 9.2 | 10 | 9.4 |
| VitK mg | 0.50 | 0.47 | 0.45 | 0.50 | 0.47 | 0.45 | 0.50 | 0.47 |
| Thiamin mg | 1.80 | 1.70 | 1.60 | 1.80 | 1.70 | 1.64 | 1.80 | 1.69 |
| Riboflavin mg | 3.60 | 3.37 | 3.26 | 3.6 | 3.38 | 3.27 | 3.0 | 2.8 |
| Pyridoxine mg | 3.50 | 3.28 | 3.17 | 3.5 | 3.3 | 3.19 | 3.0 | 2.8 |
| Vit B12 mg | 0.01 | 0.009 | 0.009 | 0.01 | 0.01 | 0.01 | 0.007 | 0.007 |
| Biotin mg | 0.15 | 0.15 | 0.14 | 0.15 | 0.14 | 0.14 | 0.12 | 0.11 |
| Folic acid mg | 0.55 | 0.52 | 0.50 | 0.55 | 0.52 | 0.50 | 0.50 | 0.47 |
| Niacin mg | 35 | 33 | 32 | 30 | 28 | 27 | 25 | 23.5 |
| Pantothenic acid mg | 10 | 9.5 | 9.0 | 10 | 9.4 | 9.1 | 10 | 9.4 |
| Choline mg | 1300 | 1200 | 1180 | 1000 | 940 | 910 | 750 | 700 |
*NPP: non phytate phosphorus
Table 2: Nutrient requirements of broilers under Indian conditions (DM basis)
| Nutrients | BIS, 1992 | Suggested for Indian conditions* | |||
| Starter | Finisher | 0-3 wks | 3-6 wks | 6-9 wks | |
| ME Kcal/kg | 2800 | 2900 | 2950 | 3050 | 3100 |
| CP% | 23.00 | 20.00 | 22.00 | 19.50 | 18.70 |
| CF, max % | 6.0 | 6.0 | 6.0 | 6.0 | 6.0 |
| AIA max % | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 |
| Linoleic acid % | 1.0 | 1.0 | 1.0 | 0.9 | 0.9 |
| Lysine min | 1.2 | 1.0 | 1.2 | 1.05 | 0.98 |
| Methionine min % | 0.50 | 0.35 | 0.48 | 0.42 | 0.39 |
| Methionine+Cystine% | 0.90 | 0.7 | 0.86 | 0.76 | 0.70 |
| Threonine % | – | – | 0.75 | 0.65 | 0.60 |
| Tryptophan % | – | – | 0.20 | 0.18 | 0.17 |
| Arginine % | – | – | 1.24 | 1.05 | 0.01 |
| Isoleucine % | – | – | 0.80 | 0.70 | 0.65 |
| Calcium, min % | 1.2 | 1.2 | 1.0 | 0.9 | 0.8 |
| Available P, min % | 0.5 | 0.5 | 0.45 | 0.40 | 0.35 |
| NaCl, max % | 0.6 | 0.6 | 0.3 | 0.3 | 0.3 |
| Manganese, mg | 90 | 90 | 50 | 50 | 50 |
| Iodine, mg | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| Iron, mg | 120 | 120 | 50 | 50 | 50 |
| Zinc, mg | 60 | 60 | 50 | 50 | 50 |
| Copper, mg | 12 | 12 | 10 | 10 | 10 |
| Vitamin A, IU | 6000 | 6000 | 5000 | 5000 | 5000 |
| Vitamin D3, ICU | 600 | 600 | 400 | 400 | 400 |
| Vitamin E, IU | 15 | 15 | 15 | 15 | 15 |
| VitaminK, mg | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| Thiamin, mg | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 |
| Ribiflavin, mg | 6.0 | 6.0 | 6.0 | 6.0 | 6.0 |
| Pyridoxine, mg | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 |
| Pantothenic acid, mg | 15 | 15 | 15 | 15 | 15 |
| Nicotinic acid, mg | 40 | 40 | 40 | 40 | 40 |
| Biotin, mg | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 |
| Vitamin B12, mg | 0.015 | 0.015 | 0.015 | 0.015 | 0.015 |
| Filic acid, mg | 0.015 | 0.015 | 0.015 | 0.015 | 0.015 |
| Choline, mg | 1400 | 1000 | 1400 | 1000 | 800 |
| *based on work conducted at CARI, Izatnagar and elsewhere in India | |||||
The basic purpose of phase feeding is to provide nutrients as per need depending upon the growth rate and type of growth.The dietary protein levels for broilers should be in between 21 to 23% during starting and 18-21% during finishing period at energy level of 3000 to 3200 kcal ME per kg in both the phases. Calorie-protein ratio must be maintained for effective utilization of protein as well as amino acids. Ambient temperature and age at marketing of broilers determine calorie-protein ratio. Faster growth is achieved when the protein level is increased i.e. at lower calorie to protein ratio. The broiler chickens requirements for energy and proteins are higher, likewise, the requirements of vitamins and minerals are also higher to support rapid growth, and metabolism of nutrients. Further, poultry farmers are looking for ways to improve the nutrient utilization of feed: i) Adding fat slows down the feed passage in the gut resulting in increased digestion by digestive enzymes. ii) Conditioning and pelleting improves the utilization of certain nutrients. iii) Inclusion of dietary enzymes helps break down the poorly digested dietary components.iv) Proper proportions of saturated and unsaturated fats enhance fatty acid absorption. v) Optimum particle size to increase surface area results in efficient enzyme action and enhanced nutrient availability.vi) Using synthetic essential amino acids to have a balanced low protein diet reduces nitrogen excretion- an energy costly affair. These practices improve feed utilization of the bird by making nutrients more available.Thus, by balancing the feed as per nutrient requirements and feeding broilers scientifically, one can definitely run a profitable poultry farm.