Broiler industry has been bridging the gap between the supply and demand of high quality protein foods such as meat for the ever increasing human population worldwide. However, the overall expenditure on broiler diets remains between percent of the total cost of broiler production. Therefore, the broiler industry has been striving to reduce the cost of production through improved feed utilisation by the broilers. For this purpose, exogenous enzymes have been claimed to improve the utilization of feeds by maximising the conversion of dietary nutrients into broiler meat, for example. Enzymes not only help in formulating more balanced diets for broilers by increasing the choice of ingredients such as cereals and other agro-industrial by-products but also by increasing their e ciency of utilisation by enhancing the digestibility of fibrous materials. The enzymes can also be beneficial as growth promoters instead of antibiotics which are banned in the European Union. Enzymes have been tried alone and in combinations with other additives such as organic acids to maintain health and production of broilers. Although the role of enzymes in improving feed utilisation, growth, meat quality and economics has been well reported, their quality, consistency and reproducibility have been questioned by many researchers. This article reviews the role of enzymes alongside organic acids in broiler diets and their future potential to maintain bird health and e cient broiler production which has desirable impacts on the environment.
The origin and evolution of spectral curvature in blazar spectral energy distribution (SED) is still unclear. Since the observed SED curvature is related to an intrinsic curvature in emitting electron energy distribution (EED), we study this question by employing a log-parabolic EED with a curvature parameter and peak energy to model the quasi-simultaneous broadband SEDs of selected blazars in the Fermi-LAT Bright AGN Sample using synchrotron and inverse Compton (IC) processes. We find that the log-parabolic IC model can successfully explain the emission in all blazars in our sample. On average, FSRQs have higher magnetic field, Doppler factor, and curvature than BL Lac objects. The BL Lac objects show an anticorrelation between the curvature parameter of the EED and its peak energy, which is a signature of stochastic acceleration. FSRQs do not manifest such correlation and rather show a mild positive relationship between these parameters. This suggests that the evolution of spectral curvature in the BL Lac objects is dominated by a strong stochastic acceleration component, whereas the curvature in FSRQs evolves in a cooling dominated regime due to an additional external Compton component. The strong cooling in FSRQs not only restricts the electron peak energy but also adds extra curvature to the high energy tail of emitting EED. Since the curvature decreases from FSRQs toward high peak BL Lac objects (HBLs), opposite to peak energy, the curvature parameter can be considered a third parameter of the blazar sequence in addition to peak frequency and luminosity.
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