Search

The influence of feed or protein depletion-repletion on phosphorus balance, and bone characteristics was studied on 70 growing pigs from 90 to 168 d of age. During depletion period (90-118 d of age), C pigs were fed semi ad libitum (95% ad libitum intake) on control diet; FR pigs (feed-restricted group) consumed 40% less of control diet compared to C pigs; PR pigs (protein-restricted group) were fed semi ad libitum a low-protein diet containing 40% less protein than control diet. During repletion period (119-168 d of age), daily allowances for C pigs were equal of 95% ad libitum intake. Remaining pigs consumed a control diet at the same amount as C pigs. Pigs were slaughtered at 90 d of age ("zero" animals, n = 7), following seven animals from each group at d 118, 146 and 168  of age. At 118 d of age, phosphorus content in the body was lower (p < 0.001) in FR than C and PR pigs. Lower phosphorus deposition and utilisation was observed in FR animals. Humerus in FR pigs was lighter, had lower mineral content and density, but had greater stiffness than in PR and C pigs. During repletion period, FR pigs deposited more phosphorus and had better phosphorus utilisation than C and PR pigs. Humerus mineral density was greater in FR and PR than in C pigs. Humerus strength was the highest in PR pigs, and the lowest in FR pigs. Humerus stiffness was greater in PR than in C and FR pigs. In conclusion, during depletion period feed restriction affects bone growth more than protein restriction, and bone strength is less sensitive, than other bone characteristics, to feed restriction. Reductions in measured bone indices observed after lower feed intake can be fully compensated during the repletion period and resulted mainly from better utilisation of minerals.

Sixteen female piglets (58 d of age, 16.8 ± 0.8 kg body weight [BW]) were assigned to two groups (n = 8) and received until day 100 of age (50.3 ± 1.2 kg BW) ad libitum either a diet with a standard (diet C) or low (diet L) total phosphorus (P) content (5.38 and 4.23 g/kg, respectively). Diet C was supplemented with mineral P (1.15 g/kg) and did not contain microbial phytase. Diet L did not contain any inorganic P but 750 FTU/kg of microbial phytase. Despite these treatments, both diets were composed with the same ingredients. Body mineralisation of each gilt was assessed by determining the bone mineral content (BMC), area bone mineral density (BMD) by the dual-energy X-ray absorptiometry (DXA) at days 58, 72, 86 and 100 of age. Feeding diet L caused a higher P digestibility (p = 0.008) measured from days 72 to 86 of age and at 100 days of age a higher BMC and BMD (p ≤ 0.01). Furthermore, the gilts of group L deposited more minerals in the body than control pigs (by 2.4 g/d, p = 0.008). It was found that BMD and BMC were positively correlated with body lean mass and digestible P intake. The results indicated that, even for very young pigs, the addition of microbial phytase instead of inorganic P increases the amount of digestible P covering the requirements of piglets for proper bone mineralisation. Furthermore, it was proved that the DXA method can be successfully applied to measure body fat and lean mass contents as well as bone mineralisation of growing pigs using the same animals.

Abstract: Forty-eight gilts were used to investigate the effects of a 30% restriction of feed (groups F) or protein (group P) in the period from 90 to 118 days of age on performance and on bone growth and mineralization between 119 and 168 days of age, when all of the pigs were fed an adequate diet at approximately 95% of ad libitum, with the exception of those in one of the previously feed-restricted groups, which were offered the same diet ad libitum (F1). During the entire experiment, control pigs (C) were fed according to a semi ad libitum scale. Half of the pigs from each treatment were slaughtered at the end of periods 1 and 2, and the femur and the third and fourth metacarpal and metatarsal bones were removed and weighed. Bone mineral content (BMC) and density (BMD) were determined using a DXA scanner (NORLAND). Pigs subjected to the feed and protein restrictions in period 1 were 17% (P<0.001) and 7% (P<0.001) lighter, respectively, at 118 days of age than their control counterparts. The femur and other bones of feed-restricted pigs were also significantly lighter, and their BMC and BMD significantly lower at 118 days than those of the controls. Protein restriction had no significant effect, however, on bone weight or mineralization at 118 days of age. After 118 days of age, F1 pigs grew significantly faster than pigs on all of the other treatments and were heavier at 168 days of age than control, P-, and F-treatment pigs. At 168 days, F-treatment pigs grew faster and were of a similar weight (P>0.05) as controls, whereas P pigs exhibited similar growth as controls. There were no significant differences in bone weight or BMC between treatments at 168 days of age, but BMD was significantly higher in the femur and fourth metatarsal bones of F- and P-treatment pigs compared with control animals. The results indicate that young pigs subjected to short-term deficiency of protein and energy intake were able to recover and even surpass the parameters of bone/skeletal mineralization compared with adequately fed pigs. [Copyright &y& Elsevier]