The objective of this work was to evaluate the comparative P bio-avalability of different sources of phosphate based on their effects on animal performance, bones mineralization and mineral retention in broilers. To achieve this goal, two experiments were conducted. In Experiment 1, twenty diets were prepared including five different phosphorus sources, either mono-calcium phosphate (MCP) or 4 different batches of di-calcium phosphate, to supplement non phytic P (NPP) levels at 3.0, 3.5, 4.0 and 4.5 g/kg in the diets. In Experiment 2, three treatments were used: the low MCP diet was deficient in NPP (3.1 g/kg for the starter phase and 2.8 g/kg for the grower phase); the high MCP diet and the high TCP (tri-calcium phosphate) diet included adequate levels of NPP (4.4-4.7 g/kg for the starter phase and 4.2-4.3 g/kg for the grower phase). Phytase was not added to experimental diets. Results of Exp. 1 indicated that an increase of NPP in the diet from 3.0 to 4.0 g/ kg increased weight gain and feed intake between d 1 and d 21 (Trial 1). Alternatively, tibia weight and ash percentage at d 21 responded up to the level of 4.5 g/kg and showed significant difference with birds of the 4.0 g/kg NPP group. In Trial 2, chickens fed with the high MCP and TCP had improved growth performances and bone mineralization. No differences were observed on the P availability among different mineral P sources. A level of 4.5 g/kg, NPP is recommended when phytase is not included to maximize both performance and bone mineralization in broiler chickens up to d 21.
Phosphorus (P) is one of the most expensive nutrients in poultry diets as well a source of environmental concerns regarding excessive P in ground water. In order to reduce the total dietary P, the use of exogenous phytase provides a more efficient use of dietary P and a reduced inclusion of feed phosphates. However, mineral sources of P in diets for broiler chickens are still a need to meet the requirement of poultry and prevent P deficiencies. The phosphate levels in the diets will depend on their P content; and P bio-availability is pivotal to formulate diets at a higher precision and avoid excessive P excretion.
Different P sources are mainly used in the poultry diets, such as di-calcium phosphate (DCP) and monocalcium phosphate (MCP). The MCP has a higher concentration of P (22.6%) than DCP (
Phosphorus is also a nutrient that linearly reduces growth performance and bone characteristics when levels below P requirements are applied (
Consequently, in this study we tested the hypothesis that different feed phosphates, varying in the amount of P and Ca, will affect the dietary P retention and overall productivity of broiler chickens. Two experiments were conducted to test this hypothesis and the objectives were to evaluate the effect of the P source provided at different levels in broiler diets on the availability of P and their effects on performance and bone mineralization for broilers. In the first experiment, P availability was compared between MCP and four different batches of DCP in broilers chickens up to d 21. In the second experiment, the inclusion of a source of TCP as a single source of Ca and P was compared to MCP in broiler diets with respect to their effects on performance, bone mineralization and P retention in broilers up to d 35.
All the animal experimentation procedures used in the two experiments were approved by the animal Ethics Committee of the Universitat Autònoma de Barcelona and were in compliance with the European Union guidelines for the care and use of animals in research (
Five hundred broiler male chickens (Ross 308) were included in the study. Animals were randomly distributed into twenty experimental groups according to the experimental treatment and continuously controlled for 21 days. Birds were individually weighed and distributed in 100 battery brooder cages (5 chicks per cage) to get a similar initial average body weight for each cage. Chicks were wing-tagged to record individual body weight as well the group body weight during the experimental period. The brooder temperature was maintained at 35ºC during the 4 first days post-hatch, and then was progressively reduced to 25ºC from d 14 to d 21. The light cycle was 24 h/d from d 1 to d 2, 23 h/d from d 3 to d 10 and 18 h/d from d 11 to d 21.
An identical basic mixture of ingredients (wheat, 250g/kg; corn, 287.2 g/kg; soybean meal, 248.8 g/kg; and soybean oil, 42.5 g/kg) was formulated and prepared to contain adequate levels of nutrients (ME (metabolizable energy), 2,960 kcal/kg; DM (dry matter), 882 g/kg; and CP (crude protein), 220 g/kg) to meet and exceed nutritional requirements in broilers (
Ninety-six male broiler chickens (Ross 308) were used in a growth performance study during 35 days. Animals were randomly distributed into three experimental groups according to the experimental treatment. Chicks were wing-tagged to monitor individual BW and distributed in 24 battery brooder cages (4 chicks per cage) to get a similar initial average body weight for each cage. The brooder temperature was maintained at 35ºC during the 4 first days post-hatch, and was progressively reduced to 25-22ºC on d 14 to d 35 day. The light cycle was 24h/d from d 1 to d 2, 23h/d from d 3 to d 10 and 18h/d from d 11 to d 35.
All diets met or exceeded the nutrient requirements for broilers (
Individual BW (body weight) as well as the group BW was monitored at the start (d 1) and d 7, d 14, d 21, d 28 and d 35 post-hatch. From these values the FI, WG and G:F ratio were determined. Feed intake was registered and excreta were collected from d 19 to d 21 and from d 33 to d 35 in order to determine the retention of Ca and P. At d 35, three chickens per cage were euthanized and the left tibia was collected for bone-ash determination.
Diets and excreta samples were analyzed for DM, Ca and P. Dry matter was determined by placing samples in a drying oven at 105ºC for 24h. Diets, excreta samples were digested in a nitric perchloric and fluorhydric acid mixture, and P and Ca concentrations were subsequently determined by performing inductively coupled, plasma-optical emission spectroscopy (ICP-OES) using an Optima 4300DV Perkin-Elmer optical emission spectrometer.
The tibias were defatted for 48 h in ethyl alcohol followed by a 48 h extraction in ethyl ether; they were then dried for 12 h at 110ºC and then ashed overnight at 550ºC (
Data were analyzed by using the Generalized Linear Model procedure of SAS software (SAS, 2008, vers 9.2). In Exp. 1, the main factors used in the model were P level (4 levels), sources (5 sources) and their interaction. In Exp. 2, the dietary treatments and the source of P were taking into account. The pen of the chicks served as the experimental unit. The results are presented as least square means. Probability was considered significant when
Animal performance along the experimental period is presented in
The effect of different sources and levels of P on bone mineralization (tibia weight and ash) and tibia weight/BW is reported in
The feed intake and growth performance responses of broiler chickens to different levels and sources of Ca and P are presented in
The effect of different treatments on bone mineralization (ash content, %), tibia weight (g, and % as total BW) are presented in
The retention of P and Ca expressed on a percent basis and g/day is shown in
Present results showed that feed consumption, bird performance and bone mineralization were decreased when low NPP levels (3.0 to 3.5 g/kg) were included in the diet as compared to 4 and 4.5 g P/kg. Similar results were observed by
In our experiment, no differences in animal performance were observed between broilers fed the 4.0 and 4.5 g NPP/kg diets. However, greater NPP levels, from 4.0 to 4.5 g/kg, increased tibia weight and tibia ash (mg/tibia).
Considering the differences on P solubility observed in the literature among different phosphate sources, and the likely interactions among minerals on P precipitation in the poultry digesta, we hypothesized that phosphate sources would differ on P availability. Therefore, our study focused on the comparison of the broiler performance and bone mineralization from MCP, DCP or TCP sources, as well as the comparison among different batches of DCP. Diets were prepared on a total P basis in order to allow that likely differences on their P availability (between MCP and DCP in Exp.1, and between MCP and TCP in Exp. 2) could promote differences on performance or bone mineralization.
Results indicated that no differences were observed among P sources (MCP, DCP and TCP) with respect to their effects on the productive performance and bone mineralization of broiler chicken at ages of 21 and 35 days.
Moreover,
No significant difference was either observed between high MCP and TCP in animal performance and bone mineralization in Exp. 2. However,
The results of this experiment also showed that the dietary P retention (% values) is increased when the levels of NPP are lower in the diet. However, the results were not affected by the P source (MCP, TCP). Result is consistent with
Our results allow us to conclude that despite the highly different physical structure and chemical properties among P sources (MCP, DCP and TCP), no evidences were observed of differences in their vivo P availability in growing broilers. Increasing the dietary P have a direct impact on performance and bone mineralization, but higher NPP levels are required in the broiler diets to optimize bone mineralization than to optimize growth performance.
We would like to acknowledge the farm staff of the Servei de Granges i Camps Experimentals of the UAB for their support and support and assistance during the above described experiments. This manuscript has been proof-read by Dr. Maurice Pitesky from the UC Davis School of Veterinary Medicine-Cooperative Extension, Department of Population Health and Reproduction. Manel Hamdi is also grateful to the Animal Nutrition and Welfare Service (SNiBA) for the provision of a research fellowship.