Effect of Supplementing Microbial Phytase on Broiler Chicks Fed Low Di-calcium Phosphate Diets

After calcium (Ca) the second abundant mineral in animal body is phosphorus (P) and majority (80%) of the P is found in bones and teeth (NRC, 1994). The P is not only essential for bone development, growth, health, production and reproduction but it also aids in energy metabolism, synthesis of sugars and maintenance of acid-base balance in the body. However, the quantity and availability of dietary P is vital for growing animals. It is well established that phytate is the major source of P in plant based feedstuffs. Since birds are unable to produce any endogenous phytase, therefore their capability to utilize P from phytate is very limited (Woyengo et al., 2010).

Phytate is a ubiquitous component of plant sourced feed ingredients which encompasses approximately two-thirds of total plant P (Hughes et al., 2009). In poultry, phytate P is normally utilized with availability from 0 to 50%, depending on age and metabolic adaptation in critical circumstances. Therefore, to meet the P requirement, generally expensive inorganic P sources are added to poultry diets. This practice leads to non-utilization of a large portion of dietary P from feedstuff and its excretion in faeces (Hughes et al., 2008; Woyengo et al., 2010) which ultimately pollutes environment. Recently, microbial phytase supplementation in poultry diets has got remarkable attention to reduce negative impact of phytate p on environment and performance of birds (Ceylan et al., 2003; Francesch and Geraert, 2009). Since phytase efficiency in the digestive tract is influenced by various factors like phytase origin, type of birds and ambient temperature etc. Therefore, each phytase preparation for poultry must be tested on broilers/layers to ensure its efficacy (Hughes et al., 2008; Onyango et al., 2005). Information regarding effect of microbial phytase addition in broiler chicks’ diet having low DCP is limited. Therefore, current study was designed to asses the effect of microbial phytase supplementation in broiler chicks fed low DCP diets on growth, economic efficiency and P contents in serum and tibia bones.

The research work was carried out at Animal Nutrition Program, Animal Sciences Institute, National Agricultural Research Centre, Islamabad, Pakistan. One hundred ninety five (195) one day old mixed sex broiler chicks (initial mean body weight 43 ± 2 gm) were allocated randomly to three dietary treatments, each having five replicates with 13 birds per replicate. These birds were placed in separate battery cages (measuring 120 cm long × 94 cm wide × 73 cm height). Each cage was equipped with drinker and feeder adjusted inside of the cage. Water and experimental rations (in mash form) were offered ad libitum. During the trail all of the birds were kept under 24 h lighting regimens. All chicks were vaccinated against Newcastle disease, infectious bursal disease, infectious bronchitis, as per recommended schedule in Pakistan.

1R-I, positive control diet containing 0.83% di-calcium phosphate (DCP); R-II contained 50% less DCP (0.41%) than R-I without phytase and R-III contained R-II plus phytase Quantum® Blue.

2According to the producer’s declaration Quantum® Blue contains solid forms 5000 FTU/g and it was added to broiler rations @ 100 g/ton.

†Constant ingredients included corn ground 65%; corn gluten meal (60%) 1%; soybean meal 22%; fish meal 8%; vegetable oil 0.55%; lysine sulphate 0.50%; liquid-methionine 0.30%; threonine 0.08%; marble chips 1%; sodium chloride 0.15% and soda bicarb 0.15%.

Three iso-nitrogenous and iso-caloric rations were prepared at Islamabad Poultry Feeds, Islamabad as: Commercial ration with 0.83% DCP served as control (R-I) whereas similar as R-I was formulated but with 50% less DCP (0.41%) without (R-II) or with Quantum® Blue (6- phytase) supplementation (R-III). The composition of rations used during experimentation is given in Table I. Phytate P content in all rations was similar i.e., 0.21%. According to the producer’s declaration, Quantum® Blue contains solid forms 5000 FTU/g and it was added to broiler rations @ 100 g/ton. Phytate P of corn grains, corn gluten meal 60% and soybean meal were determined by Sibbald (1986) technique and diets were also analyzed for CP, CF, EE, total ash, Ca and total P according to AOAC (1990). Daily feed intake and weekly body weight gain (BWG) per replicate per pen were recorded. On 35th day, blood and tibia bone samples from 5 birds per treatment were collected. The left tibia from each bird was excised and stored in sealed plastic bagsat -20ºC until further analysis. At the time of analysis, meat and fat were gently removed from tibia bones. After overnight drying at 100ºC, the bones were extracted in ether for 6 h and burnt to ash in a Muffale furnace at 600ºC. The ash from each tibia was used for Ca and P analysis according to AOAC (1990).

All data were presented as means±SE. The data were analyzed statistically using the standard procedure of analysis of variance technique in completely randomized design as described by Steel et al. (1997) by using Minitab 15 software. For significant differences, means were compared using Duncan’s multiple range test at 5% level of probability.

Results regarding effects of microbial phytase (Quantum® Blue) supplementation to diets having low di-calcium phosphate (DCP) on growth performance in broiler chicks are given in Table II. The results showed that dietary DCP levels (0.83% and 0.41%) with or without Quantum® Blue supplementation did not influence feed intake and feed: gain ratio in chicks however, body weight gain (BWG) reduced significantly (P<0.05) on diet with 0.41% DCP without Quantum® Blue (R-II) compared to those fed diet with 0.83% DCP (R-I) or diet with 0.41 % DCP plus Quantum® Blue (R-III) up to 21 days of age. Whereas, feed intake in chicks fed diets having 0.41 % DCP without (R-II) or with Quantum® Blue (R-III) improved significantly (P<0.05) during 22-35 days of age and overall feeding period (1-35 days) compared to those fed diet having 0.83% DCP (R-I) however, difference between R-II and R-III was non-significant (P>0.05). Our results are partially supported by Boling-Frankenbach et al. (2001) who reported that dietary

a, bMeans with different superscript letters within rows are significantly different (P<0.05), BWG, body weight gain; FI, feed intake; SEM, standard error of mean. For detail of treatments, see Table I.

phytase supplementation did not affect feed intake during first 21 days of age whereas others reported improvement in feed intake (Cabahug et al., 1999; Denbow et al., 1995). The reason for these contrasting results might be due to number of factors i.e. phytase source (type and phytate content), and dietary characteristics (processing, Ca: P ratio) etc. (Ravindran et al., 1995).

Quantum® Blue supplementation to low DCP (0.41%) diet (R-III) resulted in improved (P<0.05) BWG as well as best feed: gain ratio in chicks during 22-35 days of age and overall feeding period (1-35 day) compared to chicks fed R-II, however, both rations did not differ from R-I diet. The lowest growth rate in broiler chicks fed diet R-II was may be due to lower availability of dietary P from phytic acid molecules of feedstuffs. But when Quantum® Blue added to diet with low DCP (R-III), presumably it liberated more P from phytic acid molecules of feedstuffs to satisfy the chicks requirement and ultimately improved BWG and feed: gain ratio that were comparable to those fed positive control diet (R-I) having 0.83% DCP. Similar findings were observed by Bozkurt et al. (2006) who reported comparable or even better growth rate and FCR in broilers fed diets with low-P plus microbial phytase than those fed the standard P diets. Viveros et al. (2002) explained that microbial phytase supplementation in poultry diets increases P availability, consequently improves growth performance and minerals (Ca, P, Mg and Zn) utilization in chicks. Better growth in phytase supplemented chicks may also be due to some positive effects of enzyme on utilization of metabolizable energy in chicks (Ravindran et al., 2001).

The concentration of Ca and P in serum and tibia bones of experimental birds are given in Table III. In blood serum and tibia bones, Ca and P contents were comparable between R-I and R-III but both were higher (P<0.05) than in R-II, presumably due to the added phytase that liberated P from phytic acid molecules to satisfy the broilers’ requirement for deposition of Ca and P in bones. This result is consistent with previous reports that phytase supplementation improved bone strength and mineralization in chicks fed low P diets (Dilger et al., 2004; Woyengo et al., 2010). Supplementation of diets with microbial phytase derived from Aspergillus niger increases availability and retention of phytate P and Zn in chicks as measured by ash content of bone (Ahmad et al., 2000; Qian et al., 1995; Sebastian et al., 1996).

For statistical details and treatment groups, see Table II.

Feed cost of live weight gain mainly relies on cost of feed and efficiency of feed utilization by animals (Nair et al., 2004). In this study, rate of one Kg of commercial diet was Rs. 46; Quantum® Blue Rs. 3000 and of DCP was Rs. 80. The maximum feed cost incurred per unit weight gain was recorded in broilers fed R-II diet (Rs. 84.10) followed by chicks on R-I (Rs. 80.04) and R-III (72.13) diets indicating that chicks on R-I and R-II ate more and gain less weights (Table IV). The total feed cost per unit weight gain of broilers fed R-III diet was numerically 14% and 9% less than the broilers fed R-II and R-I, respectively.

For details of treatment groups, see Table II.

Per kg cost of commercial diet was Rs. 46; Quantum® Blue Rs. 3000; Di-calcium phosphate Rs. 80.

It is concluded from results that supplementation of phytase (Quantum® Blue) to diet containing low DCP had positive effects on body weight gain; feed: gain ratio and economic efficiency as compared to chicks fed non-phytase supplemented diets.

The authors would like to acknowledge the Islamabad Poultry Co. Pvt. Ltd. Rawalpindi for preparation of experimental diets for this study.

The authors have no conflict of interest.