Effect of dietary energy restriction on retention of protein, fat and energy in broiler chickens

Abstract

1. Broiler chickens were fed 60-100% of recommended energy intakes to study the effects of energy restriction on protein and fat retention. 2. At an energy retention of 179 kJ/kg W0.75 d, only protein was retained. At higher energy intakes, each increment in retention had a rather constant composition: about 85% energy in fat and 15% in protein. At lower energy intakes body fat was mobilised whereas protein was deposited. 3. The efficiencies of energy retention in protein and fat were estimated to be 0.66 and 0.86 respectively. 4. The rather constant composition of additional retained energy after additional energy supply provides an explanation for a linear relationship between energy intake and energy retention.

Effect of energy intake on performance and carcass composition of broiler chickens from two different genetic groups

“…Thus, the lower the dietary energy: protein ratio, the leaner the carcass. This find is consistent with Summers et al (1992) and Boekholt et al (1994), who also found a reduction in fat deposition due to a decrease in dietary energy: protein ratio.…”

“…The fact that higher energy consumption promotes better weight gain is well established (Boekholt et al, 1994;Lesson et al, 1996); however, why dietary energy level does not affect broiler feed intake in some cases remains unanswered. In fact, the nutritional factors involved in broiler feed intake control mechanisms are not completely understood, and seemingly other macronutrients than energy influence feed behavior.…”

“…Energy intake is considered a fundamental factor in broiler production, not only because it affects growth rate and carcass characteristics (Boekholt et al, 1994;Leeson et al, 1996), but also because it is indirectly involved in metabolic diseases, such as ascites (Leeson et al, 1995). Therefore, finding the optimal point between economic and physiological optimal dietary energy level for broilers has been the goal of many researchers.…”

Growth characteristics of commercial broiler and native chickens as predicted by different growth functions

“…Such a trend was not found in the native birds, however (Table 6). Metabolizable energy intake affects BW and composition (Boekholt et al, 1994;Wiseman and Lewis, 1998). Geneticists have selected broilers for many years to grow faster and achieve a bigger size sooner (Havenstein et al, 2003).…”

Breeding for efficiency in the broiler chicken: A review

“…The energy retained in the body as protein and lipid can be quantified based on their heats of combustion, i.e. 23.8 and 39.6 MJ kg −1 , respectively (Boekholt et al 1994;Emmans 1994). These combustion heat values vary slightly throughout literature, probably due to differences in the proportions of the components on which the average properties are determined; however, it cannot be expected that the chemical structure of proteins and lipids (and therefore their combustion heat values) could be altered via artificial selection and so these values were kept constant in our calculations.…”