Three experiments involving 162 pigs were conducted to assess the efficacy of phytase (Natuphos; BASF, Mount Olive, NJ) in low-P, corn-soybean meal-based diets. The phytase was produced by a recombinant Aspergillus niger. The phytase supplement contained 5,000 phytase units (PTU)/g. In Exp. 1 (66 pigs) and 2 (60 pigs), growing-finishing pigs were fed fortified corn-soybean meal diets formulated to be adequate (.50%), marginal (.425%), or inadequate (.35%) in P during the growing phase (23 to 60 kg BW) followed by adequate (.40%), marginal (.35%), or inadequate (.30%) P, respectively, during the finishing phase (to 104 kg BW). Dicalcium phosphate was the source of supplemental P. In addition, the low-P sequence (.35/.30% P) was supplemented with phytase at 250, 500, or 1,000 PTU/kg. Rate and efficiency of gain decreased linearly (P < .01) and bone breaking strength decreased quadratically (P < .01) as the concentration of P was decreased in the diets. Responses in growth and bone traits to increasing levels of phytase activity in the low-P diet were linear (P < .01). The highest level of phytase in the low-P diet restored growth rate and bone breaking strength to levels that approached or met those of pigs fed the adequate P diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Dehulled soybean meal prepared from genetically modified, herbicide (glyphosate)-tolerant Roundup Ready soybeans containing the CP4 EPSPS protein and near-isogenic conventional soybeans were assessed in an experiment with growing-finishing pigs. The soybeans were grown in the yr 2000 under similar agronomic conditions except that the Roundup Ready soybeans were sprayed with Roundup herbicide. Both were processed at the same plant. The composition of the two types of soybeans and the processed soybean meal were similar. Corn-soybean meal diets containing conventional or Roundup Ready soybean meal and fortified with minerals and vitamins were fed to 100 cross-bred pigs from 24 to 111 kg BW. Diets contained approximately 0.95% lysine initially and were reduced to 0.80 and 0.65% lysine when pigs reached 55 and 87 kg BW, respectively. There were 10 pens (five pens of barrows and five pens of gilts) per treatment with five pigs per pen. All pigs were scanned at 107 kg mean BW and all barrows were killed at the end of the test for carcass measurements and tissue collection. Rate and efficiency of weight gain, scanned backfat and longissimus area, and calculated carcass lean percentage were not different (P > 0.05) for pigs fed diets containing conventional or Roundup Ready soybean meal. Gilts gained slower, but they were more efficient and leaner (P < 0.05) than barrows. Responses to the type of soybean meal were similar for the two sexes with no evidence of a diet x sex interaction for any of the traits. In most instances, carcass traits of barrows were similar for the two types of soybean meal. Longissimus muscle samples from barrows fed conventional soybean meal tended (P = 0.06) to have less fat than those fed Roundup Ready soybean meal, but water, protein, and ash were similar. Sensory scores of cooked longissimus muscles were not influenced (P > 0.05) by diet. The results indicate that Roundup Ready soybean meal is essentially equivalent in composition and nutritional value to conventional soybean meal for growing-finishing pigs.

The local mean-field equations are solved for XY spins on a square lattice with competing nearest-neighbor interactions. For a model with randomly chosen frustrated sites, on lowering the temperature one finds the following sequence of phases: paramagnet; nonuniform ferromagnet; noncollinear, nonuniform ferromagnet; reentrant spin-glass. The reentrant transition occurs via the mechanism of frustrated-spin "melting." For randomly chosen negative bonds it is more difficult to obtain reentrance and to provide a physical explanation.PACS numbers: 75.50. Kj, 75.30.Kz There is a well established yet rapidly growing experimental literature on the phenomenon known as "reentrance" (of the magnetization), which is associated with disordered magnets. Briefly, one finds that at high temperatures the system is a paramagnet; below a "Curie" temperature T c the system is a nonuniform ferromagnet; and below a somewhat illdefined reentrant temperature T r the system begins to show irreversibility and to lose its magnetization, as it enters a spin-glass (SG) state. 1 For random exchange systems, the infinite-range model with both ferromagnetic and random exchange 2 -in the replicasymmetry-breaking solution of Gabay and Toulouse (GT) 3 -yields a sequence of phase transitions in agreement with experiments sensitive to the transverse spin components, but does not include the reentrant phenomenon. It is the purpose of the present paper to discuss a simple model which, within local mean-field theory, yields (and provides an explanation for) reentrance.The sequence found by GT is as follows: on lowering the temperature, one goes from the paramagnetic phase (P) to a ferromagneticlike phase (F); then to a mixed phase (Ml) with both a magnetization and nonzero transverse spin components (equivalently, the Ml phase is noncollinear, or canted); and on further lowering of the temperature, the solution develops replica-symmetry breaking (interpreted as the onset of irreversibility), as one enters a phase (M2) which, like Ml has a magnetization and is noncollinear. 4 This sequence is observed experimentally if, in addition to magnetization measurements, one also employs techniques which are sensitive to the transverse spin components, such as small-angle neutron scattering, Mossbauer effect, or nuclear orientation studies. 5 In particular, a transition to a noncollinear state occurs at a temperature T K < T c , and at an even lower temperature (T r ) one sees the onset of irreversibility. Nevertheless, the infinite-range model does not yield the observed decrease in magnetization at the onset of irreversibility.We have undertaken local mean-field calculations on a simple model in order to shed some light on the reentrant phenomenon. We find that, as in the experiments and in the GT theory for the infinite-range model, there are what appear to be three phase transitions, but in the present model the lowest-temperature transition appears to be associated both with the onset of multiple solutions (irreversibility) and with reentrance. It is pos...

The onset of spin canting due to the interaction of defect bonds has been studied by numerical calculation, continuum theory, and discrete lattice theory. This model is relevant to the problem of canting in amorphous ferromagnets. For a square lattice with a nearest-neighbor host exchange constant J, the onset of canting has been studied for the following disordering influences: a single negative bond of strength J', a single site with two bonds J' opposite and adjacent to one another, and two bonds J' at arbitrary separation and relative orientation. In the case of interacting bonds it is convenient to think of the system as having dipole sources that can interact via a host ferromagnet: Indeed, both the continuum theory and the discrete lattice theory in the large separation limit give an effective interaction of two-dimensional dipolar form. When the system goes noncollinear, the nonlinear effects that occur at the impurity site are taken to provide the dominant self-limiting terms that keep the distortion small. When the effects of the periodic boundary conditions are taken into account, reasonable agreement is found between the numerical calculations and the theoretical predictions. Local mean-field theory has been employed throughout, and is used to obtain the temperature at which the relatively weak canting energy is overcome by the thermal energy, and canting disappears. These results are relevant to what we call "weak" defects in the magnetic alloying process: Individual impurities cannot cause canting, but the effective dipolar interaction is long range, and at a high enough impurity concentration should lead to a canted state with transverse "pseudo-" or "semi-" spin-glass order. A general discussion of experimental systems is given, in light of our results. the general behavior when a canted spin ("canted local state") interacts with an otherwise magnetically ordered system. This work also pointed out the possibility of a "semi-spin-glass" in which a ferromagnetic component coexists with spin-glass-like transverse components.Reference 6 considered both interstitial canted spins and substitutional canted spins, and their effective interactions due to distortions they induce in the host lattice. In the 6rst case, the system consisted of an antifer-38 11 718

The onset of canting for a ferromagnet with one and two antiferromagnetic defect bonds has been studied analytically. For individual negative defect bonds which are unable to cause canting, there is a long-range effective dipolar-like interaction which determines whether or not the system will cant. An effective Hamiltonian is obtained which applies more generally. A canted state at low temperatures, but a collinear state at somewhat higher temperatures, can be expected on the basis of this effective Hamiltonian.