Associations of feed efficiency with circulating IGF-1 and leptin, carcass traits and meat quality of lambs.

The aim of this study was to investigate the effects of feed efficiency classifications on live animal measurements, circulating IGF-1 and leptin concentrations, and carcass, non-carcass and meat quality traits of lambs. One-hundred and two lambs approximately 70 days-old with initial live weight of 24.6 ± 3.71 kg (mean ± SD) were individually fed for 56 days to determine residual feed intake (RFI) and residual feed intake and gain (RIG). Lambs were then classified as phenotypically Low-, Medium- or High-RFI and Low-, Medium- or High-RIG phenotypes. Circulating leptin and IGF-1 concentrations were higher in more efficient lambs (Low-RFI or High-RIG). Variation in RFI and RIG did not affect meat redness or tenderness, but High-RIG lambs had darker meat. These findings show that the phenotypically more efficient Low-RFI and High-RIG lambs produced carcasses with similar characteristics and meat quality as the less efficient High-RFI and Low-RIG lambs but have a strategic advantage of lower feed intake to achieve similar production outcomes.

Rapidly forming, slowly evolving, spatial patterns from quasi-cycle Mexican Hat coupling.

Alattice-indexed familyof stochasticprocesses hasquasi-cycle oscillationsif itsotherwise-damped oscillations are sustained by noise. Such a family performs the reaction part of a discrete stochastic reaction-diffusion system when we insert a local Mexican Hat-type, difference of Gaussians, coupling on a one-dimensional and on a two-dimensional lattice. Quasi-cycles are a proposed mech-anism for the production of neural oscillations, and Mexican Hat coupling is ubiquitous in the brain. Thus this combination might provide insight into the function of neural oscillations in the brain. Im-portantly, we study this system only in the transient case, on time intervals before saturation occurs. In one dimension, for weak coupling, we find that the phases of the coupled quasi-cycles synchronize (es-tablish a relatively constant relationship, or phase lock) rapidly at coupling strengths lower than those required to produce spatial patterns of their amplitudes. In two dimensions the amplitude patterns form more quickly, but there remain parameter regimes in which phase synchronization patterns form with-out being accompanied by clear amplitude patterns. At higher coupling strengths we find patterns both of phase synchronization and of amplitude (resembling Turing patterns) corresponding to the patterns of phase synchronization. Specific properties of these patterns are controlled by the parameters of the reaction and of the Mexican Hat coupling.