Effects of Benzoic Acid and Dietary Calcium:Phosphorus Ratio on Performance and Mineral Metabolism of Weanling Pigs

Abstract

In a 2×2 factorial experiment the hypotheses tested were that the metabolic acid load caused by benzoic acid (BA) added to the feed affects bone mineralization of weanling pigs, and that a wide dietary calcium (Ca) to phosphorus (P) ratio in phytase-supplemented feeds with a marginal P concentration has a positive effect on bone mineralization. The four experimental diets, which contained 0.4% P and were supplemented with 1,000 FTU phytase/kg, contained either 5 g BA/kg or no BA and either 0.77% Ca or 0.57% Ca. The 68 four-week-old Large White pigs were fed the experimental diets ad libitum for six weeks and were then slaughtered. Benzoic acid increased feed intake (p = 0.009) and growth rate (p = 0.051), but did not influence the feed conversion ratio (p>0.10). Benzoic acid decreased the pH of the urine (p = 0.031), but did not affect breaking strength and mineralization of the tibia (p>0.10). The wide Ca:P ratio decreased feed intake (p = 0.034) and growth rate (p = 0.007) and impaired feed the conversion ratio (p = 0.027), but increased the mineral concentration in the fat-free DM of the tibia (p = 0.013) without influencing its breaking strength (p>0.10). The observed positive effect of the wide Ca:P ratio on bone mineralization may be attributed, at least in part, to the impaired feed conversion ratio, i.e. to the higher feed intake and consequently to the higher mineral intake per kg BW gain. The negative impact on animal performance of the wide dietary Ca:P ratio outweighs its potentially positive effect on bone mineralization, precluding its implementation under practical feeding conditions.

Effect of dietary calcium level and source on mineral utilisation by piglets fed diets containing exogenous phytase

“…The results of this experiment illustrate the importance of dietary calcium in optimising P utilisation in piglets fed low P diets (2.9 dP/kg diet) including exogenous phytase. According to the combined data from the present and the previous (Gutzwiller et al., ) experiments, a low dietary Ca (<5 g Ca/kg) was beneficial for growth performance, but limited the metabolic use of P for bone mineralisation. On the other extreme, a high dietary Ca level (>8.5 g/kg) led to P deficiency.…”

“…In a previous experiment to the present one, Gutzwiller et al. () reported that, in a diet containing 2.9 g dP/kg and including exogenous phytase, 7.7 g Ca/kg impaired growth performance, but improved bone mineralisation relative to 5.6 g Ca/kg.…”

“…The three dietary Ca levels (4, 7 and 10 g Ca/kg diet) covered a Ca:dP range from 1.4:1 to 3.2:1 using a diet providing adequate amount of dP and low in total P. Combined with the CaCO 3 data from a prior experiment conducted under identical conditions (5.6 and 7.7 g Ca/kg diet; Ca:dP of 1.9:1 and 2.6:1; Gutzwiller et al., ), the linear and quadratic Ca dose–response model (Table ), the graphical interpretation indicates that the metabolic use of P for bone mineralisation begun to be limited with a dietary Ca below <5.0 g/kg (Ca:dP ratio of <1.8:1) due to increasing P losses over urine. On the other extreme, a dietary Ca level exceeding 8.5 g/kg (Ca:dP ratio of > 2.9:1) led to P deficiency (serum p < 2.5 mmol/l).…”

“… The model was based on the data from the present experiment using CaCO 3 ( n of observations = 36; n of animal block = 12) and from Gutzwiller et al. () ( n of observations = 68; n of animal block = 17). Y xy = a + a x + b × Ca xy + c × Ca 2 xy + e xy , where Y xy is the response variable, x is the experimental animal block, y is the level of the independent variable Ca from CaCO 3 treatments only, a is the intercept, a x is the effect of x on the intercept a , b is the linear coefficient of Ca, c is the quadratic coefficient of Ca and e xy is the residual error. …”

“…The aim of this experiment was to extend, under identical conditions, the dietary Ca range (5.6 and 7.7 g/kg) used by Gutzwiller et al. () to evaluate the effects of three dietary Ca levels (from expected Ca deficiency to Ca excess), using two Ca sources (CaCO 3 and Lithothamnium calcareum ) on growth performance, stomach mineral solubility, mineral ATTD and mineral status in piglets fed a diet low in P and supplemented with phytase.…”