Desempenho e parâmetros ósseos de bovinos nelore submetidos ou não à suplementação fosfórica durante o período de confinamento
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Data
2016-02-29
Autores
Souza, Vinícius Carneiro de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Este estudo avaliou o efeito da suplementação fosfórica (SP) sobre o consumo de nutrientes, desempenho, parâmetros ósseos, qualidade de carne e a utilização do fósforo (P) por bovinos Nelores, durante o período de confinamento. Para tanto, utilizou-se 42 novilhos com peso médio inicial de 296±25 kg distribuídos em delineamento inteiramente casualizado com 3 tratamentos e 14 repetições. A dieta era formada por bagaço de cana (200g/kg na MS) e concentrado (800g/kg na MS). Os tratamentos dietéticos foram: sem a adição de P suplementar (T1), núcleo mineral comercial (T2) e fosfato bicálcico (T3). Os teores porcentuais de P na MS foram 0,24; 0,42 e 0,50, respectivamente. Foram avaliados os consumos de MS, PB, FDN, Ca, P e Mg, bem como a absorção aparente, retenção, excreção fecal e urinária de P, o desempenho animal e as características da carcaça. As avaliações da qualidade óssea consistiram na determinação da composição química óssea, densidade mineral óssea (DMO) e densidade em água (DA), além dos valores séricos de cálcio (Ca), P, magnésio (Mg), paratormônio (PTH), fosfatase alcalina (FA) e a concentração de P na saliva e no líquido ruminal. Os consumos de MS, PB e FDN foram similares entre os grupos que receberam ou não a SP (P>0,05). As ingestões de Ca e Mg foram superiores nos tratamentos em que se adicionou o núcleo comercial ou o fosfato bicálcico (P<0,05). O consumo, a retenção e a excreção de P foram influenciados pelo aumento do teor de P nas dietas experimentais (P<0,05). O desempenho e as características de carcaça não foram afetados pelo teor de P na dieta (P>0,05). A suplementação com P aumentou significativamente a excreção de P através das fezes e da urina e os custos da dieta. Os animais submetidos ou não à suplementação fosfórica, tiveram teores de Ca, relação Ca:P e DMO da 12ª costela semelhantes (P>0,05). No entanto, os animais dos tratamentos T1 e T3 tiveram redução dos teores de magnésio nas costelas ao longo do estudo (P<0,05). Os animais do tratamento sem fósforo suplementar tiveram menor espessura da cortical dos metacarpos (P<0,05), sem comprometer a sua resistência e rigidez (P>0,05). Durante todo o período experimental, nenhum animal foi positivo no teste da agulha realizado nos processos transversos das vértebras lombares. Não houve efeito da suplementação fosfórica sobre a concentração de Ca e P no soro dos animais (P>0,05). Porém, a inclusão de núcleo mineral no tratamento T2 resultou em maior concentração de Mg no soro (P>0,05). A suplementação fosfórica alterou de forma significativa os níveis de paratormônio (PTH) e fosfatase alcalina (FA) no soro (P<0,05) e os animais do tratamento T1 tiveram as menores concentrações circulantes destes hormônios. Nas condições brasileiras, bovinos confinados ingerindo elevadas quantidades de concentrados não necessitam de suplementação com P e o teor de P (0,24 % na MS), utilizado no tratamento sem P suplementar foi suficiente para atender as exigências dietéticas dos animais. Menores teores de P podem até serem adequados, mas não foram testados neste estudo. A suplementação com P aumentou consideravelmente a excreção de P através das fezes e urina e os custos com alimentação dos animais.
The present study was conducted to evaluate the effect of phosphorus supplementation (PS) on nutrient intake, performance and phosphorus (P) utilization by Nellore steers in a feedlot. Forty-two animals with an initial body weight of 296±25 kg were distributed in a completely randomized design consisting of 3 treatments and 14 replicates. The diet on a DM basis was comprised of sugarcane bagasse (200 g/kg) plus concentrate (800 g/kg). The treatments were without supplementary P (T1), commercial mineral supplement specific for feedlot cattle (T2) and dicalcium phosphate (T3) with 0.24, 0.42 or 0.50 % P, respectively. The DM, CP and NDF intakes were similar between the groups with or without the PS (P>0.05). The highest intakes of Ca and Mg were observed in the treatments with commercial mineral supplement or dicalcium phosphate. Intake, retention and excretion of P were influenced by the increase in P content in the experimental diets (P<0.05). Performance and carcass characteristics were not affected by P content in the diet (P>0.05). Supplementation with P significantly increased the excretion of P in the feces and urine and the feeding cost. Therefore, under Brazilian conditions, there is no justification for supplementing P in feedlot rations. The animals submitted or not to phosphorus supplementation had a similar content of Ca, Ca:P ratio and bone mineral density (BMD) at the 12th rib (P>0.05). However, animals of the T1 and T3 treatments had significant reductions in magnesium contents in the rib throughout the study (P<0.05). The animals from treatment without phosphorus supplement had lower cortical thickness of the metacarpal bone (P<0.05), without compromising its resistance and stiffness (P>0.05). Throughout the trial period, no animals were positive in the needle test in the transverse processes of the lumbar vertebrae. There was no effect of phosphorus supplementation on the concentration of Ca and P in the serum of animals (P>0.05). However, the inclusion of commercial mineral supplement in T2 treatment resulted in higher Mg concentration in serum of animals (P>0.05). The phosphorus supplementation significantly changed the levels of parathyroid hormone (PTH) and alkaline phosphatase (AP) levels (P<0.05) and the animals of the T1 treatment had smaller circulating concentrations of these hormones. Under Brazilian conditions, feedlot beef cattle do not appear to require P supplements and a value of P (2.4 g/kg DM), as used in the control diet, appears adequate. Lower values may also be appropriate but were not tested here. Phosphorus supplementation significantly increased the feeding costs, P excretion in the feces and urine and therefore resulted in economic losses.
The present study was conducted to evaluate the effect of phosphorus supplementation (PS) on nutrient intake, performance and phosphorus (P) utilization by Nellore steers in a feedlot. Forty-two animals with an initial body weight of 296±25 kg were distributed in a completely randomized design consisting of 3 treatments and 14 replicates. The diet on a DM basis was comprised of sugarcane bagasse (200 g/kg) plus concentrate (800 g/kg). The treatments were without supplementary P (T1), commercial mineral supplement specific for feedlot cattle (T2) and dicalcium phosphate (T3) with 0.24, 0.42 or 0.50 % P, respectively. The DM, CP and NDF intakes were similar between the groups with or without the PS (P>0.05). The highest intakes of Ca and Mg were observed in the treatments with commercial mineral supplement or dicalcium phosphate. Intake, retention and excretion of P were influenced by the increase in P content in the experimental diets (P<0.05). Performance and carcass characteristics were not affected by P content in the diet (P>0.05). Supplementation with P significantly increased the excretion of P in the feces and urine and the feeding cost. Therefore, under Brazilian conditions, there is no justification for supplementing P in feedlot rations. The animals submitted or not to phosphorus supplementation had a similar content of Ca, Ca:P ratio and bone mineral density (BMD) at the 12th rib (P>0.05). However, animals of the T1 and T3 treatments had significant reductions in magnesium contents in the rib throughout the study (P<0.05). The animals from treatment without phosphorus supplement had lower cortical thickness of the metacarpal bone (P<0.05), without compromising its resistance and stiffness (P>0.05). Throughout the trial period, no animals were positive in the needle test in the transverse processes of the lumbar vertebrae. There was no effect of phosphorus supplementation on the concentration of Ca and P in the serum of animals (P>0.05). However, the inclusion of commercial mineral supplement in T2 treatment resulted in higher Mg concentration in serum of animals (P>0.05). The phosphorus supplementation significantly changed the levels of parathyroid hormone (PTH) and alkaline phosphatase (AP) levels (P<0.05) and the animals of the T1 treatment had smaller circulating concentrations of these hormones. Under Brazilian conditions, feedlot beef cattle do not appear to require P supplements and a value of P (2.4 g/kg DM), as used in the control diet, appears adequate. Lower values may also be appropriate but were not tested here. Phosphorus supplementation significantly increased the feeding costs, P excretion in the feces and urine and therefore resulted in economic losses.
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Palavras-chave
Carcaça, Fósforo, Nelore, Qualidade óssea, Suplementação, Carcass, Phosphorus, Nellore, Bone quality, Supplementation