Effect of food intake on energy and protein metabolism in the skin of Romney sheep

Abstract

Sheep fed on either a low (500 g lucerne (Medicago sativa) chaff/d; L) or high (1 100 g lucerne chaffld; H) intake had measurements made, using arterio-venous techniques, of blood flow and energy metabolite and cysteine utilization in the skin. Sheep on the H intake had significantly increased skin blood flow (P = 0.014) and oxygen uptake (P = 0.05). Although the H sheep had higher skin blood flow they showed no difference in skin uptake of either glucose or acetate compared with the L sheep, but the €5 sheep had a significantly lower output of lactate (P = 0.014). Animals in each group had either ['4C]glucose or ['4C]acetate infused into the skin which showed that acetate was the predominant precursor of skin sterol and fatty acid synthesis in the H sheep while L sheep skin used both glucose and acetate. The H sheep showed an increase in the net uptake of cysteine by the skin (P = 0.053), and in the uptake of cysteine for protein synthesis (P = 0.078), relative to the L sheep and this increase was of a comparable magnitude to the increase in blood flow to the skin. Although blood flow, protein synthesis and energy supply increased in the skin of the H sheep by 200-300 %, wool production would only have increased by 10-20%, suggesting that nutrient flux changes are not the sole level of regulation of wool production.Skin energy metabolism: Cysteine: Feed intake: Sheep Regulation of metabolism in the skin of sheep is of productive significance in two ways; first, and directly, because of the significant role of wool production within skin metabolism, second because of the potential for partitioning nutrient supply to the skin, away from other body tissues. Such partitioning could result either in the skin sparing metabolites for use by other tissues or, alternatively, retaining metabolites to the detriment of other tissue function.Studies of protein metabolism in the skin of sheep (Lobley et al. 1992) and preruminant lambs (Attaix et al. 1988) suggest that in early life skin has a similar protein fractional synthesis rate (FSR; g protein synthesis/d per g tissue protein) to that of muscle. However, by adult life skin has a higher FSR than that of muscle and makes almost an equal contribution to total body protein synthesis. The results of Lobley et al. (1992) also demonstrated that skin FSR was sensitive to the level of feed intake, but the study was not able to discriminate the processes by which skin regulates these responses to intake. For example, intake-sensitive changes in FSR could be via a modification of blood supply (and thus flux of nutrients to the skin) or through a change in the uptake rate of Iimiting amino acids by the skin cells. Blood flow to the skin is itself subject to rapid and large changes consequent on the requirements of thermoregulation. These influences can confound measurements of intake responses.The role of energy metabolites in regulation of skin metabolism is unclear. Harris et al. (1989) in a preliminary arterio-venous-difference study of skin metabolism found that * For reprints...

Effects of restricted feeding and re-feeding of Barbarine lambs: intake, growth and non-carcass components

“…Our results on restricted lambs did not validate the positive relationship between the weights of reticulo-rumen, intestine and liver on the one hand, and intake on the other hand, clearly established elsewhere in underfed growing animals (Ferrell et al, 1986;Drouillard et al, 1991;Kabbali et al, 1992) and in adults (Nozière et al, 1999;Atti et al, 2000). Conversely, the weight of skin was higher for sheep in H group than for restricted ones (L and M), since skin is a metabolic organ (Harris et al, 1994). There was a close relationship between level of feeding and the weight of some non-carcass components, namely metabolic organs (Koong et al, 1982;Drouillard et al, 1991).…”

Three‐Axis Anisotropic Exchange Coupling in the Single‐Molecule Magnets NEt4[MnIII2(5‐Brsalen)2(MeOH)2MIII(CN)6] (M=Ru, Os)

“…However, the difference between the two groups (0.08, or 8%) is not as large as the difference in diet might have suggested. This is in accordance with the conclusions of Harris et al 19. These authors fed sheep a low or high intake and showed that although blood flow, protein synthesis and energy supply increased by 200–300% in the skin of sheep fed a high intake, wool production only increased by 10–20%, suggesting that nutrient flux changes are not the only level of regulation of wool production.…”

“…The present experiment was designed to test the effect of age and level of food intake on the kinetics of incorporation of the dietary carbon signal in wool from sheep raised under controlled laboratory conditions. Wool growth is markedly influenced by plane of nutrition and the major limiting nutrients are essential amino acids, and in particular sulfur‐containing amino acids 17–19. The effect of age on the growth of wool remains unclear.…”

Digestive and metabolic adaptations of ruminants to undernutrition, and consequences on reproduction

“…A lower intake results in a slight decrease in the fractional protein synthesis rate in the digestive tract, which could explain in part weight changes, whereas fractional synthesis rate does not vary in the liver [73] [60].…”