Phosphorus Influence on Growth and Reproduction of Beef Cattle

Abstract

Ninety-six 7-month-old Hereford heifers (two replicates of 48, one year apart) were individually fed for 2 years a basal ration containing .14% phosphorus on an "as fed" basis, which approxiamted 66% NRC recommendations. Forty-eight of the animals were limited to this low phosphorus (P-) diet. The other 48 (P+) received sufficient monosodium phosphate, top dressed on the basal ration, to elevate phosphorus intake to .36% on an "as fed" basis (174% NRC recommendations). The average daily weight gain for all groups was .45 kg. Feed efficiency was similar for the two groups. There was no evidence of lack of appetite or depraved appetite in either group; nor was there a difference in age of puberty. The P-cattle had a 96% pregnancy rate with 91% live calves compared to 100% and 93%, respectively, for the P+ cattle. These differences were not significant. After 9 months on trial (approximately 16 months of age) no difference in rib bone morphology was discernable from microradiographs. Blood and serum levels of phosphorus temporarily increased in the P+ cattle, but at 16 months of age were comparable to the less fluctuating values in the P-cattle. The phosphorus levels for bone and muscle were similar each year and for each treatment. Urine and fecal phosphorus excretion was significantly higher in the P+ than in the P-cattle.

Phosphorus requirement of finishing feedlot calves

“…The NRC (1996) recommendations on P requirements are higher than data from this experiment and other published work (Call et al, 1978;Erickson et al, 1999). Three possible reasons exist for disagreement between experimental data and NRC (1996) recommendations.…”

“…Dietary P fed to yearlings in that study ranged from 0.14 to 0.34% of diet DM, with individual intakes of 16 to 36 g/d equating to a range of 71 to 162% of NRC recommendations (Erickson et al, 1999). Similarly, Call et al (1978) fed growing heifers 66 or 174% of NRC-predicted requirements for P during a 2-yr study without adverse effects on gain, BW, or reproduction. Few data are available for beef cattle weighing between 250 and 600 kg fed high-energy finishing diets.…”

Effect of dietary phosphorus on finishing steer performance, bone status, and carcass maturity.

“…The authors concluded that the P required for gain of 1.3 kg/d was .25% P, despite the fact that plasma concentrations were similar in cattle fed each treatment. Long et al (1956) fed growing, yearling beef heifers P levels of .07, .11, and .15% of DM and reported linear improvements in intake, gain, and plasma P. However, Call et al (1978) fed growing heifers primarily hay diets at either 66 (10.3 g/d) or 174% (26.1 g/d) of NRC-predicted P requirements (NRC, 1978) for 2 yr and observed no differences between dietary treatments in gain, body weight, intake, or calving performance.…”

Avaliação de níveis de fósforo na dieta de novilhos Nelore em crescimento: efeitos no desempenho

“…A deficiência de fósforo está associada a uma série de sintomas inespecíficos, como baixo ganho de peso, consumo reduzido, depravação de apetite e falha reprodutiva (UNDERWOOD, 1981). As concentrações de fósforo indicadas para dietas de bovinos de corte foram aparentemente superestimadas em algumas situações (CALL et al, 1978(CALL et al, , 1986LITTLE, 1980;MARGON et al, 1982;e EZEQUIEL et al, 1988). Comparando as recomendações do NATIONAL RESEARCH COUNCIL -NRC de 1984 e 1996, nota-se que os requisitos para mantença foram reduzidos em cerca de 30%, enquanto para ganho de peso foram aumentados (devido à redução do coeficiente de absorção utilizado [0,68 vs 0,85]) na versão mais recente.…”