Proteins choice feeding

Cowan,P.J.andMichie,W. (1978a) Environmental temperature and turkey performance The use of diets containing increased levels of protein and use of a choice-feeding system. Annals of Zootechnology 17,175-180. 

Large, generalist marine grazers such as fishes and urchins attempt to choose foods that maximize nutritional input (e.g., protein, lipids, and carbohydrate) (Mattson 1980 Choat and Clements 1998) and minimize intake of secondary metabolites (Hay 1991). The untested assumption underlying these optimal foraging decisions is that detoxification and excretion rates are a constraint on toxin intake and thus drive feeding choice (Freeland and Janzen 1974). However, we have virtually no information on such constraints in marine herbivores, because it requires an understanding of the metabolic fate of secondary metabolites. 

There is considerable discussion in the medical literature on the relative merits of enteral or parenteral feeding. For enteral feeding, the choice is between elemental (or monomeric) preparations, which contain glucose and amino acids, or polymeric preparations which contain protein and... 

This chapter concentrates on the possibility of producing SCP from petrochemical feed stocks, such as n-paraffin, methane, or methanol. Between 1960 and 1980, the idea to produce SCP from crude oil sources found a lot of attention and several large-scale plants with capacities of several 100,00 tons/year were built, for instance in southern Italy. Hopes were high at the time, but the development made only slow progress. One of the reasons could be the choice of the location, which is far away from both, the source of the feedstock and the consumers of the product. Another is that oil and natural gas are expensive feed stocks, because they also have other uses. Anyway, the technology for protein production from chemicals exists and may be applied with more success in other areas of the world, where more favorable starting conditions exist. 

NPY-treated animals have been reported to show strong preference for carbohydrate when pure macronutrient diets are available, with little or no effect on fat or protein intake (Stanley etal., 1985b Tempel and Leibowitz, 1990). This had led to the suggestion that NPY may be involved in mediating the consumption of carbohydrate, which is the macronutrient of choice at the start of the active feeding period in rats (Tempel et al., 1989). Indeed, peak levels of NPY are detected in the hypothalamus at this time (Jhanwar Uniyal et al., 1990 McKibbin et al., 1991b). Others have failed to reproduce this carbohydrate selection in food preference studies, and it is possible that palatability and caloric content of diets may account for reported effects on macronutrient selection. 

In conclusion, plastid-based expression systems provide for potentially higher expression levels than the majority of nuclear expression systems, and with a higher level of transgene containment, but the platform provides limited post-translational processing choices. Also, despite reports of successful plastid transformation of new species beyond Nicotiana, the choice of production host is stiU predominantly restricted to the Nicotiana family. However, this hmita-tion does not present a serious drawback for production of pharmaceutical proteins (except perhaps for edible vaccines ) since tobacco is a non-feed/non-food crop with a weU-estabhshed agriculture. 

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