The influence of protein:energy value of the ration and level of feed intake on the energy and nitrogen metabolism of the growing pig

Abstract

1. The heat losses and energy and nitrogen balances of thirty-six individually-housed, entire male pigs (initial body-weight 18-30 kg) were measured over 7 d periods, when they were fed on rations containing 153, 201 and 258 gcrude protein (nitrogen x 6.25; CP)/kgdry matter (DM). The rations also contained 16,29,16,96 and 17.24 MJ metabolizable energy (ME)/kg DM so that the CP: ME values were 9-4, 1 1.8 and 15.0 g CP/MJ ME respectively. Each ration was given at three levels, 20, 35 and 50 g feed/kg body-weight per d, thus giving nine dietary treatments.The experiments were carried out at an environmental temperature of 22 (k 1)O. 2.Heat loss ( H ) increased significantly ( P < 0.01) with increase in ME intake. The rate of increase in H was not, however, influenced by the protein content of the ration. Thus, energy retention (ER) at any given level of ME intake was independent of the ration offered. From the relationship between ER and ME, estimates of the maintenance energy requirement (ME,) and the partial efficiency of energy utilization (k) were determined. ME, varied within the range 494-568 kJ/kg b~dy-weighto'~ per d, while k vaned from 0.70 to 0.76.3. Both energy and protein intakes had a significant influence upon the rates ofprotein (P) and fat ( F ) deposition, and hence body-weight gain. At any given level of feed intake P was higher and F lower the higher the protein content of the ration. However, when compared at similar levels of protein intake, both P and F were reduced the higher the protein content of the ration.4. From the multiple regression equations relating P and F to ME, individual estimates Of ME, and the energetic efficiencies of protein (kp) and fat (kF) depositions were determined. Using an overall mean k , value of 0.86, it was calculated that ME, ranged from 462 to 525 kJ/kg b~dy-weight~''~ per d while k p varied from 0.48 to 0.55. The significance of these estimates of k p are discussed in the light of their derivations and in relation to theoretical values.In assessing the energy requirements of farm animals it has been customary to partition the metabolizable energy (ME) intake into that required for maintenance (ME,) and that for production ME^). The productive component can be further partitioned into a requirement for protein deposition and a requirement for fat deposition. This procedure allows separate estimates for the energetic efficiency of protein (k,) and fat (kF) deposition to be calculated. Estimates of ME,, k , and kF are usually calculated from regression analyses where ME or ME, is related to the quantities of protein and fat deposited. Using these techniques it has been found in the pig, maintained under thermally-neutral conditions, that while values for k , remain relatively constant and close to those calculated on theoretical grounds, those for both ME, and k , vary considerably, the latter being generally lower than theoretical calculations indicate (Kielanowski, 1976;Pullar & Webster, 1977;Close, 1978;Fowler et al. 1980;Webster, 1980). These authors have prop...

Physiological aspects of compensatory growth in pigs

“…As mentioned earlier one of the responses of animals to restriction of their daily allowance (energy) is reduced growth of metabolically active organs (Kong et al, 1982;Close et al, 1983;Bikker, 1994;Skiba, 2000) and consequently reduced maintenance requirements, as the size of those organs directly influences these requirements (Noblet et al, 1997). Although the cost of maintenance (ME m ) is clearly defined (Wenk et al, 2001), it is very difficult to measure, especially in growing (producing) animals, as energy accretion or production are physiological processes occurring in a young organism.…”

“…The main differences concern fat and protein stores in the body as well as the size of entrails. Pigs that consume less feed have a lower entrail weight, especially of those metabolically highly active organs like the liver, kidneys, large and small intestines (Kong et al, 1982;Close et al, 1983;Skiba et al, 2001), and lower fat but higher protein stores. Whereas those that consume low protein but the same amount of energy as adequately fed animals have higher fat and lower protein stores in the body and their entrails do not differ from adequately fed pigs (de Greef, 1992;Skiba et al, 2001).…”

Limitations of conventional models and a conceptual framework for a nutrient flow representation of energy utilization by animals

“…zero RE. There is, however, convincing evidence for significant catabolism of body lipid and positive protein retention at very low ME intakes in growing pigs (Fuller et al 1976;Close et al 1978Close et al , 1982Kyriazakis & Emmans, 1992;Kyriazakis et al 1993). Reported levels of protein retention at zero energy balance are also quite variable.…”

Water in Pig Nutrition: Physiology, Allowances and Environmental Implications

“…Various nutritional factors affect the rate of water consumption and therefore urine production by pigs (Wahlstrom et al 1970;Hagsten & Perry, 1976;Friend & Wolynetz, 1981;Close et al 1983;Patience et al 1987;Pfeiffer, 1991).…”