D.M.S.S. Vitti

Phosphorus and calcium utilization and requirements in farm animals.

Dietary calcium (Ca) and phosphorus (P) are never fully utilized by animals as some may be in an unavailable form, lost during normal digestive and metabolic processes, or their absorption negatively infl uenced by several dietary and/or non-dietary factors. Thus, meeting the requirements for these elements for the various classes of farm animals depends on their bioavailability in the feedstuffs used. Furthermore, formulating diets on bioavailable calcium Ca and P basis minimizes their output in the manure, which has economic and ecological consequences. The bioavailability of Ca and P from feedstuffs is determined either as digestible P or as available P, using digestibility or the slope ratio assays, respectively. Except for legume forages, vegetable feedstuffs are very low in Ca content and therefore provision of adequate dietary Ca supply is almost entirely achieved through the use of animal-based and inorganic feedstuffs whose Ca bioavailability is > 66%. Vegetable feedstuffs have very variable P content (cereals and their by-products, 2–27, oilseed meals, 6–12 g/kg dry matter), the majority (> 65%) of which is phytate-bound and unavailable to the animal without enzymatic dephosphorylation. Phytase, the requisite enzyme to hydrolyse phytate, is insuffi cient in avian and mammalian intestinal secretions, present in some feedstuffs and ubiquitous in microbial systems. As a consequence, P bioavailability in vegetable feedstuffs is higher for ruminant than for non-ruminant species. Research and commercial efforts to increase utilizable P in vegetable feedstuffs for non-ruminants include dietary inclusion of microbial phytase, use of low phytate and higher intrinsic phytase grains and oilseed meals, and the development of phytase-secreting transgenic animals. Phosphorus in most of the animal-based and inorganic feedstuffs is highly available (> 50%). Determination of Ca and P bioavailability in feedstuffs is infl uenced by many factors, including experimental, dietary and animal, and as result a given feedstuff may be assigned different bioavailability w w w .a lk ot t b. co m

A model on biological flow of phosphorus in growing pigs

Ten crossbred barrows weighting 20kg were allocated in five groups fed and on diets consisted of different total phosphorus (P) levels: 0.30%, 0.40%, 0.51%, 0.65%, and 0.73%. The animals were intravenously injected 7.4MBq of radioactive P (32P) and after seven days they were slaughtered for further analysis. The evaluated parameters were intake, excretion, specific activities, and flow of P in compartments (1-gut, 2-blood, 3-bone, and 4-soft tissue). Besides fecal losses, the kidneys played an import role in P regulation. The flows of P from tissue and gut to the blood were affected by P intake.

Rumen phosphorus metabolism in sheep.

The objective of the present study was to examine the effect of the level of phosphorus (P) intake on ruminal P kinetics in sheep. Twelve Santa Ines male sheep (average body weight 36 kg) were fed a basal diet consisting of roughage (coast cross hay), concentrate mixture (cassava meal, soya bean meal and urea) and a mineral premix. The treatments consisted of the basal diet supplemented with 0, 1·5, 3 or 4·5 g/kg dry matter (DM) of mono-ammonium phosphate to provide increasing P levels representing treatments T0, T1, T2 and T3, respectively. The P content of experimental diets was 1·5; 2·0; 2·5 and 3·0 g P/kg DM, and considered highly deficient, deficient, adequate and in excess, re- spectively, compared with standard recommended allowances. Animals were injected with 32 P and thereafter samples of blood were collected over 7 days, while samples of rumen fluid and saliva were collected 4 and 6 days after injection. Phosphorus intake affected P concentration in ruminal fluid, whereas P concentration in saliva was not affected. The values for P turnover time in the rumen were 1-42, 1·23, 1·18 and 1·04 days, whereas values of endogenous P entry into the rumen were 1·05, 1·37, 1·53 and 1·91 g/day for T0, T1, T2 and T3, respectively, both affected by P intake. The specific activity (SA) of P in saliva, rumen and plasma were also all affected by P intake. The relationship between saliva and rumen SA emphasizes that most endogenous P in the rumen came from saliva. The possibility of an extra P source besides saliva contributing to endogenous P in the rumen is discussed. It is concluded from the results that, regardless of P intake, the flow of endogenous P into the rumen contributes to ensure a minimum supply of this essential element, which may be important in matching the requirements of the rumen microbes.

Composição química de diferentes fontes de fósforo e deposição de metais pesados em tecidos de suínos

One hundred twelve pigs averaging weight of 28.68kg, were allotted to a completely randomized blocks with seven replicates of two animals per box. The treatments consisted in factorial 8×2 (eight phosphorus sources x two sexes). The experimental diets were formulated based on corn and soybean meal and the phosphorus was supplemented through phosphate dicalcium (FBC), monodicalcium (MBC), triple superphosphate (ST), simple superphosphate (SS), Catalao rock (ROCHA), mixture of sources (MIST), and phosphoric acid (AcF) in addition to a control diet without supplemental phosphous (CONT). Samples of phosphorus sources available in the market were evaluated for particle size and chemical composition. The MBC, FBC and AcF showed a low level of heavy metal contamination, but a variation in the heavy metal composition for ST was observed. Swines fed on CONT diet showed lead and zinc accumulation in the liver. Swines fed on triple superphosphate and mixture of sources diets showed cadmium accumulation in the liver. Swine fed on ST diet showed copper accumulation in the muscles. Swine diets formulated with alternative and less elaborated sources of phosphorus caused liver and muscles deposition of minerals.

Modelos matemáticos para o estudo do fluxo biológico do fósforo em suínos alimentados com dietas suplementadas com níveis crescentes de fitase

The biological flow of P was evaluated among the physiologic or the anatomical compartments of pigs fed diets with increasing phytase levels, using P-32 as tracer. The experimental design was completely randomized. Treatments consisted of phytase levels in diets (253, 759, 1265, and 1748UF/kg). The evaluated variables were: feed intake, excretion, specific activities and flow of P in the compartments (gut, blood, bone, and soft tissus). Phytase level did not interfere with fecal and urinary excretion, specific activities, incorporation and resorption of bone, and soft tissue P and in the bidirectional flow of gut and blood, but linearly affected P absorption and bone P retention. The best response was observed with the lowest phytase levels.

Biodisponibilidade e perdas endógenas mínimas de P em dietas com níveis crescentes de fitase para suínos em crescimento pela técnica de diluição isotópica

The objective of this study was to evaluate diets containing increasing levels of phytase (253, 759, 1265 and 1748 PU/kg of diets), by mean of bioavailability and minimum endogenous P losses. Twenty crossbred barrow weighting 32.19+2.17 kg were used in a randomized block design experiment, with five treatments and four replicates. The animals were kept in metabolic cages for a ten-day adaptation period and seven days for total collection of feces and urine. Blood samples were taken for seven days. At the first day of the collection period, each animal was injected intravenously with 7.4 MBq of 32P. At the end of the experimental period the animals were slaughtered and tissues of the muscle, heart, liver, kidneys and bones were collected for further studies. The levels of phytase enzyme did not affect the urinary P, retained P, plasma P and bioavailability, but a quadratic effect was observed for levels of phytase on P in feces and endogenous P. The minimum endogenous losses of P was more efficient than bioavailability to evaluate the effect of the phytase enzyme. The best utilization of the organic phosphorus occurs on the level 759 PU.

Impacto ambiental provocado pelo P em dietas suplementadas com enzima fitase e proteína ideal para suínos em crescimento: estudo do fluxo do P no metabolismo animal

Avaliou-se a possibilidade de reducao da concentracao do fosforo inorgânico em dietas formuladas para suinos de acordo com o conceito de proteina ideal, utilizando-se um modelo experimental para o estudo do fluxo do P no metabolismo animal. Utilizaram-se 20 suinos machos castrados em delineamento em blocos ao acaso, com cinco tratamentos e quatro repeticoes. Os tratamentos corresponderam a adicao de 0, 250, 500, 750 e 1000UF/kg de dieta. No primeiro dia da fase experimental, os animais receberam, por via endovenosa, uma solucao radioativa com 7,4MBq de 32P. No final do periodo experimental, os animais foram sacrificados e coletaram-se amostras de tecidos do musculo Longissimus dorsi, coracao, figado, rins e ossos. Pode-se reduzir em 50% a suplementacao de P em dietas para suinos em crescimento adicionando-se 750UF/kg de dieta, em racoes a base de milho e farelo de soja, balanceadas de acordo com o conceito de proteina ideal, diminuindo-se significativamente a excrecao de P nas fezes.

Fluxo do fósforo de diferentes fontes de fosfatos em bovinos

The experiment was designed to evaluate the phosphorus (P) flow from different phosphate sources, in cattle. The mathematical evaluation of P changes between the physiologic or anatomical compartments, was based on model with digestive tract, blood and bones plus soft tissue. It was concluded that P from dicalcium phosphate in cattle was better absorbed than P from Patos de Minas and Tapira phosphates. Dicalcium, Patos de Minas and Tapira phosphates did not interfere with P accretion in bone and soft tissues, and the bi-directional P flow from digestive tract for the central pool in cattle increased with P absorption.

Calcium and phosphorus utilization in growing sheep supplemented with dicalcium phosphate

The objective of the current study was to evaluate the utilization of calcium (Ca) and phosphorus (P) in growing sheep consuming increasing amounts of dicalcium phosphate. Eighteen growing sheep, aged 8 months, were fed a basal diet supplemented with 0, 12·5 and 25 g of dicalcium phosphate/day. During the experiment, animals were injected intravenously with 7·4 MBq of 45Ca and 32P and samples of plasma, faeces and urine were subsequently taken daily for 1 week after injection. Rumen fluid was sampled on days 4-7 after injection. Specific radioactivity in plasma and in faeces were used to determine true absorption of Ca and P, whereas plasmatic and ruminal specific radio-activities were used to determine endogenous P flow into the rumen and turnover time of rumen P. Increasing dicalcium phosphate intake led to linear increases in faecal excretion of endogenous Ca and P (P<0·05), suggesting that surpluses of ingested Ca and P were voided through secretion to the gut. True absorption coefficients for 0, 12·5 and 25 g of dicalcium phosphate ingested daily were 0·54, 0·41 and 0·38 for Ca, and 0·66, 0·62 and 0·64 for P, respectively. Flows of endogenous P into the rumen increased linearly and ruminal turnover time of P decreased linearly (P<0·01) as P intake was increased. Concentrations of Ca and P in bone were not affected by the increased amounts of these minerals ingested (P<0·05). In conclusion, increasing ingestion of dicalcium phosphate increases faecal excretion of Ca and P, thus decreasing the efficiency of utilization of both minerals. Moreover, increasing levels of dietary P increased endogenous P excretion, contributing to the amount of P disposed of in the environment.

Application of a kinetic model to describe phosphorus metabolism in pigs fed a diet with a microbial phytase

R. S. DIAS , S. LOPEZ *, J. A. MOREIRA , M. SCHULIN-ZEUTHEN , D. M. S. S . VITTI 2, E. KEBREAB 4 AND J. FRANCE 1 1Centre for Nutrition Modelling, Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada Animal Nutrition Laboratory, Centro de Energia Nuclear na Agricultura, Caixa Postal 96, CEP 13400-970, Piracicaba, SP, Brazil 3 Instituto de Ganaderia de Montana (IGM), Universidad de Leon – Consejo Superior de Investigaciones Cientificas (CSIC), Departamento de Produccion Animal, Universidad de Leon, E-24007 Leon, Spain Department of Animal Science, University of California, Davis, CA 95616, USA