Nitrogen maintenance requirements and potential for nitrogen retention of pullets in growth phase

Abstract

Experiments were conducted to estimate daily N maintenance requirements (NMRs) and the genetic potential for daily N retention (NRmaxT) of pullets in growth phase. Three nitrogen balance trials were conducted, and a total of 48 Hy‐line W‐36 pullets were used in each trial in age periods (starter: 14–28, grower: 56–70 and developer: 98–112 days). The treatments consisted of six graded levels of nitrogen in the diets (L1 = 8, L2 = 16, L3 = 24, L4 = 32, L5 = 40 and L6 = 48 g N/kg of feed), formulated using the dilution technique. The regression analyses between nitrogen intake and nitrogen excretion were performed to fit the exponential function and to determine the NMR. The daily NMRs that were estimated at 294, 331 and 355 mg/BWkg0.67 for the initial, grower and developer periods, respectively, were applied for further calculation of NRmaxT as the threshold value of the function between N intake and daily N balance. The NRmaxT was estimated by a statistical procedure following several iteration steps by the Levenberg–Marquardt algorithm until the sum of the squares of the residual was minimized. The NRmaxT was estimated at 3,200, 2,633 and 1,826 mg/BWkg0.67 for starter, grower and developer periods respectively. The determined model parameters were the precondition for modelling of the amino acid requirement based on an exponential N‐utilization model and depended on performance and dietary amino acid efficiency. This procedure will be further developed and applied in the subsequent study.

Effects of dietary protein levels on performance, nitrogen excretion, and odor emission of growing pullets and laying hens

“…In this study, N excretion was linearly decreased as the dietary CP levels decreased in pullets (phase 1) and laying hens (phase 2). Our findings are in line with previous studies ( Novak et al, 2006 ; Soares et al, 2019 ; Alfonso-Avila et al, 2022 ). Decreasing N excretion with decreasing CP levels in diets can be attributed to either low N intake ( Table 9 ).…”

Alternative procedure for determining lysine maintenance requirement in poultry

“…Moreover, the fat deposition ratio of males and females are different (Sakomura et al, 2005). The change in body fat content represents a difficulty in the estimation of the maintenance requirement using traditional methods because there is little or no demand for amino acids for the maintenance of lipid reserves (Siqueira et al, 2011;Lima et al, 2016;Soares et al, 2019). As the amino acid requirement is more related to body protein deposition and given that at same body weight the birds could have different chemical body composition, Lys maintenance requirements are expressed more appropriately relative to body protein than to body weight (Lima et al, 2016).…”

“…The concept of maintenance has been defined as the state of balance between the intake of nutrients and their inevitable losses (Siqueira et al, 2011;Silva et al, 2014;Soares et al, 2019). That contributes to an understanding of the differences in responses between individuals of a population and enhances the requirements concept.…”