G.A. GOMES1, I.N. KANEKO2, M. RAMALHO LIMA 3 and F.G. PERAZZO COSTA4
1 AB Vista, Marlborough, UK. gilson.gomes@abvista.com;
2 Universidade Federal de Rondônia, Presidente Médici, RO, Brazil. isabelle_naemi@hotmail.com;
3 Universidade Federal Rural do Semi-Árido, Mossoró, RN, Brazil. mrlmatheus@ufersa.edu.br;
4 Universidade Federal da Paraíba, Areia, PB, Brazil. perazzo63@gmail.com.
Summary
The effect of zinc (Zn) source and Zn level were evaluated against varying doses of phytase on broiler performance and carcass traits to 42 days of age. A total of 1680 male day-old Cobb 500 broilers (49 g at placement) were allotted to one of 84 pens and split into 21 treatments in nested factorial design with 3 basal diets devoid of any Zn supplementation fed either 0, 500 or 1500 FTU/kg of phytase. The remainder of treatments comprised 3 Zn levels (50, 100 and 150 ppm), 3 phytase doses (0, 500 and 1500 FTU/kg), and 2 Zn sources (Zn-sulphate, 35% Zn; and Zn-glycinate, 26% Zn), which were used as nesting factor for the statistical analysis. Based on performance and carcass traits, the requirement for Zn-sulphate in this evaluation was between 50-100 ppm when fed at least 500 FTU/kg of phytase. Based on the same criteria (performance and carcass traits), the requirement for Zn-glycinate fell closer to 50 ppm when fed a minimum of 500 FTU/kg of phytase. Overall, phytase effect was not influenced by Zn source, and the magnitude of response of broilers to phytase was superior to that to Zn supplementation, with optimal performance and carcass traits observed at 1500 FTU/kg of phytase when supplemented to the diets (P < 0.05). Interestingly, diets containing 1500 FTU/kg of phytase without supplemental Zn showed better performance when compared to a standard dose of phytase (500 FTU/kg) and 150 ppm regardless of Zn source.
I. INTRODUCTION
Zinc (Zn) is an essential trace element with several roles in animal metabolism involving numerous metalloenzyme systems (Gaither and Eide, 2001). Most recently, attention has been brought to Zn utilization in Europe, after its ban at high dose levels. The concern was around higher Zn accumulations in soil and water bodies. Phytate present in the vegetable ingredients can be complex with divalent cations (including Zn) and render these unavailable to monogastric animals. Xu et al. (1992) showed that lower esters of phytate (IP4 and IP3, specifically), can still reduce Zn availability. In this context, the objective of this study was to evaluate the interactions of Zn level (ppm) and form (inorganic sulphate or organic glycinate) when fed with varying doses of phytase (FTU/kg), especially at higher phytase doses which degrade IP6 beyond the lower esters, on broiler performance and carcass traits to 42 days of age.
II. MATERIALS AND METHODS
The experimental protocol was approved by the Federal University of Paraiba Animal Ethics Committee. A total of 1680 male day-old Cobb 500 broilers (49 g at placement) were allotted to one of 84 pens and split into 21 treatments comprising of 3 Zn levels (50, 100 and 150 ppm), 2 Zn sources (Zn-sulphate, 35% Zn; and Zn-glycinate, 26% Zn), and 3 phytase doses (0, 500 and 1500 FTU/kg, Quantum Blue, AB Vista, Marlborough, UK). This study was a nested factorial design with 3 extra treatments devoid of any Zn supplementation fed either 0, 500 or 1500 FTU/kg of phytase. All other trace minerals were supplemented as recommended by the breed guidelines. All diets were offered as mash, corn and soybean-meal based, and fed ad libitum in three phases, from 1-10 d (starter), 11-25 d (grower) and 26-42 d (finisher). Basal diets were formulated taking into consideration the available phosphorus (avP) and calcium (Ca) contribution of 500 FTU/kg of phytase (0.15 and 0.165, respectively) and avP levels were formulated 10-15% higher than breed guidelines to avoid a severe P deficiency in treatments devoid of phytase. Body weight (BW) and feed intake were measured and feed conversion ratio corrected for mortality (mFCR) was calculated. At 42 d of age 5 birds per pen were sacrificed for determination of carcass weight and breast weight, with carcass yield being expressed as percentage of live weight (LW) and breast yield expressed as percentage of carcass weight (CW). Data was analyzed as a nested factorial design (JMP Pro 16.2) with Zn source used as the nesting factor {((Phytase, FTU/kg [0, 500, 1500] x Zn, ppm [50, 100, 150]) x Zn Source [Zn-sulphate, Zn-glycinate]) + No Zn added (0, 500 and 1500 FTU/kg phytase)}. Two-way nested ANOVA was first performed, and whenever an interaction was significant (P ≤ 0.05), means were then separated using Student’s t-test. Additionally, orthogonal polynomial contrasts (linear and logarithmical for both phytase and Zn, and quadratic for Zn levels) analysis was performed to determine the response behavior for phytase and Zn supplementation.
III. RESULTS AND DISCUSSION
No interaction for BW was observed at either 25 or 42 d of age (P > 0.10, Table 1). Phytase improved the BW of birds in a linear and logarithmical fashion, irrespective of Zn source (P < 0.01, Table 1). Although ANOVA showed significant differences for Zn levels at both 25 and 42 d, the source of Zn did not. For Zn-sulfate, BW was improved to 25 d in both a quadratic (P < 0.05) or linear (P < 0.10) fashion, while Zn-glycinate improved the BW of broilers at 25 and 42 d in a linear and logarithmical fashion (P < 0.01, Table 1). Zn-glycinate improved the BW of birds compared to that of Zn-sulphate fed birds and birds not supplemented with Zn at either age (P < 0.01).
Orthogonal Polynomial Contrasts for every zinc source on the trial: None: N; Sulphate: S; Glycinate: G; Linear (L), logarithmic (LN) and quadratic (Q) significance of Orthogonal Polynomial Contrasts .* P ≤ 0.01; † P ≤ 0.05; ‡ P ≤ 0.10
From 0-25 d of age, an interaction based on Zn source for mFCR was observed (P < 0.05, Table 2). In essence, the mFCR was improved when diets were supplemented with Zn-sulphate in the absence of phytase only, while Zn-glycinate improved mFCR independently of phytase supplementation. Phytase, from 0-25 d, improved mFCR irrespective of Zn source (P < 0.01). From 0-42 d, no significant interaction was observed for phytase (P > 0.10, Table 2). A significant main effect was observed on mFCR due to phytase dose (P < 0.01, Table 2). No effect was observed for Zn level on mFCR from 0-42 d(P>0.10), however, when comparing Zn sources Zn-glycinate improved the mFCR beyond that of the Zn-sulfate fed birds, while Zn-sulfate fed birds had better mFCR than those birds fed diets devoid of supplemented Zn at either age (P < 0.01, Table 2).
No interaction was observed for carcass yield as a g/kg of LW (CY) in birds at 42 days of age (P > 0.10, Table 1). Phytase improved CY of birds in a linear and logarithmical fashion, with Zn source (P < 0.01) significantly improving CY compared to diets devoid of supplemental Zn (P < 0.10, Table 3). Zn supplementation was significant for CY (P < 0.05) with linear and logarithmic improvements for both Zn-sulphate and Zn-glycinate (P < 0.01) and quadratic for Zn-glycinate alone (P < 0.01, Table 3). An interaction was observed for breast yield, g/kg CW, (BY, P < 0.05). Phytase dose significantly improved BY in diets devoid of Zn in a linear and logarithmic fashion (P < 0.01). In the absence of phytase, Zn appeared to have a clearer response, while 1500 FTU of phytase muted Zn response from 50 ppm onwards, irrespective of Zn source (P < 0.05, Table 3).
In summary, based on performance and carcass traits, the Zn-sulphate requirement for the current trial was around 50-100 ppm in diets with at least 500 FTU/kg of phytase, while for
Zn-glycinate the requirement to obtain the best performance and carcass traits were usually attained with supplementation levels of around 50 ppm, when birds were fed at least 500FTU/kg of phytase. In general, phytase effect was not influenced by Zn source, and the magnitude of response of phytase was superior to that of Zn supplementation, with optimal performance and carcass traits observed when 1500 FTU/kg of phytase was supplemented to the diets (P < 0.05). In fact, 1500 FTU/kg of phytase in diets devoid of supplemental Zn showed better performance than that of broilers fed 500 FTU/kg with either 150 ppm of Zn-sulphate or Zn-glycinate.
