| The experiment was to investigate the effects of dietary calcium level on growth performance,tibia quality and hematological parameters of three-way crossbred(Duroc×Landrace×Yorkshire)swines weighting30～60kg, and to estimate the requirement of dietary calcium for growth of pigs weighting30～60kg. A total of30pigs, there have be similar weight(34.2±2.1kg) and randomly allotted into5treatments with6replicates in each treatment, with1pig in each replicate. Throughout the experimental period of35days, included the prepare trial period was7d, the trial period was28d. The basal diet was mainly composed of corn and soybean. Pigs were fed five levels of dietary Ca(0.45%、0.50%、0.55%、0.60%0.65%)in a single factorial arrangement. Contents of other nutrients in diets were consistent. Feed and water were provided adlibitum during experimental stage of28days on fermentation bed. Results showed that:1There was significant effects of dietary calcium level on the average daily feed intake and the average daily gain of pigs (P<0.05), but no significant effect on feed conversion (P>0.05), and average daily gain and average daily feed intake showed a strong positive correlation, with feed conversion correlation is weak. Compared with each experimental group, average daily gain and feed intake of0.65%calcium level group were better, and the feed conversion rate of0.55%calcium level group was better. Integrated growth performance considerations, dietary calcium level of0.55%, growing pigs get the better growth performance.2There was no significant effects on content of calcium and phosphorus in serum (P>0.05), but. dietary calcium levels were from0.45%to0.65%, serum calcium and phosphorus concentrations had a tendency to be increased and then to be decreased, and to reach the extreme values with the0.55%calcium level group. While there was had significant effects on AKP in serum(P<0.05),0.45%,0.50%and0.65%calcium level groups were significantly higher than0.55%and0.60%calcium level groups.3Dietary calcium levels had no significantly effect on fresh weight of tibia, the lengh of tibial and the relative of tibial(P>0.05), but had significantly effects on mineral density and ash weight of tibia, degreased tibia weight, content of calcium and phosphorus in tibia ash(P<0.05). And there was a strong positive correlation between bone mineral density and blood indicators of calcium and phosphorus metabolism, which means that the indicators in the blood can reflect the bone mineral density.4There were significant effects on content of CaBP and BGP in serum (P<0.05). With the increased of dietary calcium levels, content of CaBP in serum had a tendency to be increased and then to be decreased, the maximum value was0.60%calcium level group as25.904ng/mL;but content of BGP in serum were increased, the minimum and maximum values were78.963pg/ml and86.137pg/mL respectively.5Dietary calcium levels had no significantly effect on serum VD3activity and content of PTH in serum(P>0.05),but had significantly effect content of CT in serum(P<0.05). While dietary calcium levels were increased, serum VD3activity and content of CT in serum had a tendency to be increased and then to be decreased the maximum value was0.60%calcium level group,but content of PTH in serum had atendency to be decreased, and maximum and minimum values were6.766pg/L and3.702pg/L, respectively.Taking the results above into account, based on criteria including growth performance and tibia quality, the requirement of calcium for growth of pigs weighting30～60kg were0.55%and0.60%, respectively. Because of that pigs were growing, the calcium level of0.60%was better. |
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