Effects of changes in the intakes of protein and non-protein energy on whole-body protein turnover in growing pigs

Abstract

1. The relationships between the intakes of protein and of non-protein energy (NPE), nitrogcn retention and body protein synthesis have been studied in female pigs weighmg 30 and 35 kg.2. Four animals were assigned to three regimens and given a conventional (basal) diet supplemented with fat, carbohydrate or protein. After 1 week, measurements of N excretion in urine and faeces (7 d collection) and gaseous exchange (3-4 d) were made. At the end of the balance period a solution of [l-14C]leucine was infused at a constant rate. Body protein synthesis was then calculated as the difference between the apparent irreversible loss of blood leucine and the loss of "C in expired air.The animals were then offered the basal diet without supplement for 10 d and the measurements of N retention, energy retention and protein synthesis were repeated.3. The intakes of metabolizable energy (ME; MJ/kg body-weight (W)0'76 per d) were 1.75 for fat, 1.58 for carbohydrate, 1-25 for protein and 1.18 for the basal diet; corresponding intakes of apparently digestible N (ADN; g N/kgWo'6 per d) were 2.30,2.31,4.35 and 2-17. Daily N retention, which during the period of basal feeding was 13.6 g was increased by between 3.4 and 7.2 g by the supplements. Daily fat deposition was also increased in the animals that received the diets supplemented with carbohydrate and fat.4. The rate of leucine catabolism was significantly reduced in the animals receiving the diets that were supplemented with W E and increased by the addition of protein to the diet.5. When based on the spec& radioactivity of blood leucine both the synthesis and breakdown of body protein (per unit metabolic body-weight) were increased by 30% in the animals receiving the high-protein diet but the increases in protein synthesis associated with the addition of carbohydrate (+ 14%) and fat (+ 12%) were much less marked. Consideration of these results together with previous observations (Reeds et uf. 1980) suggested that body protein synthesis (g N/d) increased by 0.88 for each g increase in daily ADN and by 0.93 for each MJ increase in daily ME intake. 6. Comparison of the results obtained with the animals given high-carbohydrate diets and those given high-protein diets suggested an increase in heat production of 14 KJ/g of additional fat deposition. A similar comparison of animals receiving the high-protein and basal diets suggested a heat increment of 233KJ/g additional protein deposition. The changes in heat production and protein synthesis in the animals given the protein supplement were compatible with a heat increment of 5.3 KJ/g additional protein synthesized. Because of the large proportion of heat production associated with the deposition of fat this could not be confirmed with either of the other supplements, but it is possible that the energy cost of protein accretion varies with the relative proportions of protein and NPE in the diet. In growing pigs (Reeds et al. 1980) and children (Golden et al. 1977) increases in N retention associated with increases in food intake a...

Determinação da energia metabolizável e balanço de nitrogênio de dietas com diferentes teores de proteína bruta para frangos de corte

“…Deve-se levar em consideração que o aumento do suprimento de proteína está diretamente associado com um maior turnover proteico (Reeds et al, 1981;Roth et al, 1999;van Milgen et al, 2001) e que o aumento do peso das vísceras (Noblet et al, 1987) se relaciona com o subsequente aumento da produção de calor. Com isso, a utilização de dietas de baixa proteína leva à diminuição da desaminação e produção de calor pelos animais devido aos excessos de proteína, além da menor produção e excreção de nitrogênio pela urina.…”

Nutrient-hormone signals regulating muscle protein turnover in pigs

“…In pigs, results of experiments published at the beginning of the 1980s can be used to estimate the proportion of heat production attributable to whole-body protein synthesis in a 35 kg growing pig. The estimate given by Reeds & Fuller (1983) was 20 % on the basis of an energy cost of 5.32kJ/g protein synthesized (Reeds et al 1981), with a marginal increase in protein synthesis rate of 2.2g/g deposited protein (Reeds et al 1980). The minimal value calculated for the energy cost of protein synthesis using the stoichiometric approach is 3.56 kJ/g (Waterlow et al 1978).…”

Effect of intake on whole body plasma amino acid kinetics in sheep

“…The advantages include limited surgical invasion, use of longitudinal studies and lower tracer costs compared with the large dose procedure [8,9]. This technique is, however, subject to some limitations [10], especially when a single AA is monitored (such as leucine or phenylalanine [11][12][13]), which may, or may not, be distributed similarly between the different metabolic routes (protein synthesis, oxidation or synthesis of metabolites: [5,9,14]). To date, there have been relatively few comparisons between kinetic data obtained with a number of different AA (e.g.…”