Phytate as an Anti-nutrient. Sonia Yun Liu & Peter H Selle Poultry Research Foundation within The University of Sydney

Transcription

1 Phytate as an Anti-nutrient Sonia Yun Liu & Peter H Selle Poultry Research Foundation within The University of Sydney

2 14 billion years ago Big Bang phosphorus 320 million year ago germinating seeds phytate myo-inositol hexaphosphate Hartig (1855) detected phytate Suzucki et al (1907) detected phytase Jones and Csonka (1925) detected [unwittingly] protein-phytate complexes Hill & Tyler (1954) The significance of the protein phytate complex in the digestive tract of animals has not yet been determined; whether this is associated with a low absorption of protein as amino acids is by no means certain Simons et al (1990) Improvement of phosphorus availability by microbial phytase in broilers and pigs British Journal of Nutrition (1990), 64,

3 Fundamentally, a phytase feed enzyme was developed to reduce P levels in excreta from pigs and poultry to reduce P pollution of the environment by intensive animal production However, the so-called extra-phosphoric effects of phytase, apparently unrelated to increased phytate-p bioavailability, have usurped centre-stage Nevertheless, the biggest impact of exogenous phytase is to increase P digestibility - Or is it?

4 A far larger environmental issue: A potential phosphate crisis Phosphate is a crucial component of DNA, RNA, ATP, and other biologically active compounds. Microbes, plants and animals including humans cannot exist without it. Rocks containing phosphate have been discovered and are being mined at minimal cost. But resources are limited, and phosphate is being dissipated. Philip Hauge Abelson Future generations ultimately will face problems in obtaining enough to exist. Abelson (1999)

5 Peak Phosphorus circa 2040? (Cordell and White, 2011)

6 The polyanionic phytate molecule: Mg 3 -K 6 -IP % P content (Lott et al. 2000) P Mg K 6 P 1 2 P 5 Mg K K K 4 P P 3 P Mg Potentially, IP 6 phytate carries 12 negative charges as six HPO 4 2 moieties K K

7 Exogenous phytase degrades phytate and liberates phytate-bound P in a step-wise manner The actual extent of phytate degradation is complicated by endogenous, mucosal phytase activity P In theory, complete dephosphorylation of phytate IP 6 + phytase six P moieties + inositol 6 P 1 2 P 5 4 Mucosal phytase activity is very largely dependent on dietary Ca levels and de novo formation of Ca-phytate complexes P P 3 P THE PHOSPHORIC EFFECT

8 THE EXTRA-PHOSPHORIC EFFECTS Protein-Phytate complexes are fundamental Polyanionic phytate binds proteins that are positively charged at less than ip of protein via basic amino acid residues Vaintraub and Bulmaga (1991) Protein-phytate aggregates are refractory to pepsin digestion which interferes with the initiation and the regulation of protein digestive processes Protein-phytate aggregates or complexes trigger compensatory secretions of HCl and pepsin and countersecretions of NaHCO 3 and mucin David Cosgrove (1966) Bye et al. (2013) J. Agric. Food Chem. 61,

9 Percentage increases in proximal jejunal digestibility coefficients of 16 amino acids to 500 FTU/kg phytase (Truong et al. 2015) Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Valine 31.0% 50.3% 53.9% 47.7% 24.0% 21.4% 41.5% 72.8% 64.8% Alanine Aspartic cid Glutamic acid Glycine Proline Serine Tyrosine 50.3% 62.7% 37.6% 73.1% 65.1% 54.7% 118.4% FTU/kg = 49.7% response

10 Phytase (1000 FTU/kg) increased Na digestibility coefficients by an average of 51.4% ( versus ) in four small intestinal segments of broilers offered wheat-based diets (Truong et al. 2014) PJ DJ PI DI Mean % 39.7% 48.9% 38.0% 51.4% -3

11 Phytase (500 FTU/kg) increased Na digestibility coefficients by an average of 41.0% ( versus ) in four small intestinal segments of broilers offered maize-based diets (Truong et al. 2015) PJ DJ PI DI Mean % 34.1% 47.8% 36.1% 41.0% -3.6

12 Linear relationship (r = 0.736; P = 0.010) between Na coefficients and starch in the distal ileum Truong et al. (2015) Na digestibility was significantly related to starch and protein digestibility Linear relationship (r = 0.825; P = 0.002) between Na digestibility coefficients and protein (16 amino acids) in the distal ileum

13 Phytase (500 FTU/kg) increased Na digestibility coefficients by an average of 35.5% ( versus ) in four small intestinal segments of broilers offered maize-based diets (Truong et al. 2016) -0.3 PJ DJ PI DI Mean % 31.0% 39.8% 28.7% 35.5% -4.8

14 Correlations between Na digestibility coefficients in four small intestinal segments and key performance parameters (Truong et al. 2016) Item PJ DJ PI DI Gain r = P < r = P < r = P = r = P = FCR r = P < r = P = r = P = r = P = Protein digestibility r = P = r = P = r = P < r = P < Starch digestibility r = P = r = P < r = P = r = P < 0.001

15 x % Impacts of dietary Na on sodium pump (Na + /K + -ATPase) activity in jejunum of broiler chickens g/kg Na mmole*protein/minute and FCR at 13 days g/kg Na

16 NaHCO 3 HCl Duodenum PJ DJ PI DI Truckloads of NaHCO 3 are dumped into the duodenum ex pancreas, liver, gut lining to buffer HCl and Na is then retrieved along the small intestine by phytase

17 Cytoplasmic concentrations of Na+ within enterocytes are the most important determinant of sodium pump activity (Therein & Blostein, 2000) Na + Na +

18 Systemic depletion of Na as NaHCO 3 is hyper-secreted into the duodenum to buffer excess HCl + pepsin secretion triggered by the presence of pepsin-refractory, binary protein-phytate complexes Crop Proventriculus Gizzard Small intestine NaHCO 3 NaHCO 3 is dumped into the duodenum ex Pancreas Liver Gut lining Protein Formation of protein-phytate complexes Phytate Reduction of sodium pump activity from systemic depletion of Na Compromised glucose and amino acid uptakes Refractory to pepsin digestion Compensatory outputs of pepsin and HCl Protective secretion of NaHCO 3 and mucin

19 The co-absorption of Na and glucose from the gut lumen into enterocytes is largely via SGLT-1 transport systems and is driven by the electrochemical gradient maintained by the sodium pump (Na +,K + -ATPase) However, phytate has been shown to decrease sodium pump activity and glucose absorption in rats (Dilworth et al. 2005) and phytase has been shown to increase sodium pump activity and glucose absorption in broiler chickens (Ning Liu et al. 2008) How does phytate decrease/phytase increase sodium pump functionality along the small intestine? Re-phosphorylation of the Na pump? Cell-signaling by lower IP esters within enterocytes? Depletion of Na concentrations within enterocytes?

20 Digestive Dynamics or Bilateral bioavailability of starch and protein

21 The phytate-phytase axis in the context of digestive dynamics of broiler chickens Sonia Y. Liu, Ha H. Truong, Amy F. Moss, Christine Sydenham and Peter H. Selle Poultry Research Foundation, Camden NSW

22 Apparent starch and protein (N) digestibility along small intestine in sorghum-based diets Duodenum Proximal jejunum Distal jejunum Proximal ileum Distal ileum Starch Protein (N)

23 20% of incoming dietary energy is consumed by the gastrointestinal tract in the digestion and absorption of nutrients (Cant et al., 1996) Slower and incomplete apparent digestion Degradation of dietary amino acids: a major source of energy for gut function. (Fuller and Reeds, 1998) Dietary Amino Acids Endogenous amino acids: digestive enzymes, mucin Protein synthesis for muscle growth

24 Starch/glucose The small intestine consumes relatively little energy derived from starch/glucose Glucose triggers insulin secretion which may prevent deamination of amino acids and prompts net protein deposition Glucose is the energy source for protein deposition Pelley, 2009

25 Dynamics of starch and protein digestion influence growth performance in broilers [sorghum-based diets as a model] Meta-analysis on 33 treatments Six sorghum varieties Hammer-milling screen size (6.0, 3.2, 2.0 mm) Steam-pelleting temperatures (65, 70, 80, 85, 90, 95 C) Feed additives (exogenous feed enzymes, sodium metabisulphite) Feed forms (mash, intact pellets, pellets reground mash)

26 FCR (g/g) Ileal digestibility was NOT related to feed conversion efficiency R² = R² = Starch digestibility in distal ileum Nitrogen digestibility in distal ileum

27 FCR (g/g) Jejunal digestibility WAS related to feed conversion efficiency (P < 0.05) R² = R² = Starch digestibility in proximal jejunum Nitrogen digestibility in proximal jejunum

28 FCR (g/g) Feed conversion ratio WAS related to digestion rates of starch and nitrogen R 2 = 0.76 Se ** P < Slowly digested nitrogen 1.7 Rapidly digested starch 1.6 Mediumly digested nitrogen Mediumly digested starch 1.4 Rapidly digested nitrogen 1.4 Slowly digested starch Starch digestion rate (x 10-2 min -1 ) Nitrogen digestion rate (x 10-2 min -1 )

29 Comparative weight gain of broiler chickens offered diets with different protein and starch digestive dynamics as determined by Box-Behnken response surface design Corn starch (0, 10, 20%); Fishmeal (0, 8.75, 17%); Access to feed (6, 15, 24 hours)

30 Comparative FCR of broiler chickens offered diets with different protein and starch digestive dynamics as determined by Box-Behnken response surface design

31 Phytate and Phytase Phytate binds protein through binary or ternary complexes according to gut ph and protein ip Phytate may bind starch directly, or indirectly through starch granule associated protein Thompson (1988). Food Technology 42:

32 Phytate, endogenous N flow and glucose 80% of dietary glucose is actively absorbed by Na + -dependent transport systems The secretion of mucin, which is glycosylated protein, is an effective loss of amino acids and glucose Phytase may improve balance of starch and protein digestive dynamics by enhancing glucose absorption, increasing digestion of dietary protein, decreasing endogenous AA flows, and enhancing AA absorption

33 Phytase increased starch disappearance in small intestine 0FTU/kg 500FTU/kg Proximal jejunum Distal jejunum Proximal ileum Distal ileum P = P = P = P = Truong et al. (2015) Animal Feed Science and Technology 209,

34 Truong et al. (2015) Animal Feed Science and Technology 209, Phytase increased protein disappearance in small intestine to a larger extent FTU/kg FTU/kg Proximal jejunum Distal jejunum Proximal ileum Distal ileum P < P < P = P = 0.002

35 Truong et al. (2015) Animal Feed Science and Technology 209, Phytase narrowed the ratio of disappearance rates in the small intestine 0FTU/kg 500FTU/kg Proximal jejunum Distal jejunum Proximal ileum Distal ileum P = P = P < P = 0.015

36 Conclusions FCR may be influenced by the relative rates of protein and starch digestion and protein digestion is more influential than starch digestion. The substrate phytate has the capacity to impede digestion of protein and absorption of amino acids and, probably to a lesser extent, starch and glucose, thereby impacting on digestive dynamics. Phytase may improve the synchrony of protein and starch digestion, amino acids and glucose absorption via influencing Na +,K + -ATPase activity Liu SY, Selle PH (2015) A consideration of starch and protein digestive dynamics in chicken-meat production. Worlds Poultry Science Journal 71,

37 Acknowledgements