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The ideal essential amino acid ratio for laying hens in growth and production

Full text
Author(s):
Letícia Soares
Total Authors: 1
Document type: Doctoral Thesis
Press: Jaboticabal. 2018-09-28.
Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
Defense date:
Advisor: Nilva Kazue Sakomura
Abstract

The traditional dose-response method used to determine the ideal essential amino acid ratio (IAAR) is based on the response of the bird to the gradual increase of the test amino acid concentration in the diets, since it is considered very costly, since a test is required for each amino acid. On the other hand, by the deletion method, only one assay is required to determine IAAR, so it is faster and practical. Thus, the aim of this thesis was to determine the ideal amino acids ratio for pullets and laying hens using the deletion method. The first study was conducted to estimate daily N maintenance requirements (NMR) and the genetic potential for daily N retention (NRmaxT) of pullets in growth phase. Three nitrogen balance trials were conducted, a total of 56 Hy-line W-36 pullets were used in each trial in age periods (starter: 14 to 28, grower: 56 to 70 and developer: 98 to 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. It was estimated the daily NMR as 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 in 3200, 2633, and 1826 mg/BWkg0.67 for starter, grower, and developer periods, respectively. The determined model parameters were the precondition for modeling 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. In the second study, the aim was to apply the efficiency data and amino acid requirements obtained from nitrogen balance assays for the essential amino acids and to determine the ideal ratio between them for growing pullets. Three nitrogen balance trials were conducted, a total of 96 Hy-line W-36 pullets were used in each trial (starter: 14 to 28, grower: 56 to 70 and developer: 98 to 112 days). Twelve treatments with eight replicates and one bird per cage were used. A balanced diet (BD) was formulated to meet the IAAR and the requirement of other nutrients for pullets. To formulate the deficient diets, the BD was diluted with corn starch to reduce 30% of the dietary amino acid content. The diets were again supplemented with vitamin, mineral, fiber, energy, and industrial amino acids sources to achieve the same levels of the BD, except for the amino acid to be evaluated in the treatment, which remain reduced in 30%. In each trial, the data of nitrogen intake, excretion, deposition and retention were obtained in a balance trial. The b values were estimated by b=(ln(NRmaxT)-ln(NRmaxT-NR))/(NI)). Also, these data were used to calculate the requirements by the equation: Requirement=(EAA)BDx(2-DEL-(NDEAA/NDBD)). The bc-1 values were obtained dividing b by the dietary AA concentration. The IAAR by Goettingen approach was obtained by dividing the bc-1 from lysine by the bc-1 value from each other AA in each trial. The relation between the AA requirements with Lys requirements provided de IAAR by Louvain approach. The IAAR determined by Goettingen approach were Lys 100; Met+Cis 86, 88, 81; Trp 17, 22, 22; Thr 77, 67, 68; Arg 103, 111, 109; Val 75, 80, 84; Ile 64, 67, 75; Leu 101, 121, 124; Phe+Tir 112, 126, 130; Gly+Ser 81, 130, 112; His 35, 35, 36% from14 to 28 days, 56 to 70 days and 98 to 112 days, respectively. The IAAR determined by Louvain approach were Lys 100, Met+Cys 73, 80, 67; Trp 18, 20, 22; Thr 67, 68, 69; Arg 108, 108, 108; Val 77, 80, 84; Ile 70, 75, 77; Leu 113, 117, 129; Phe+Tir 121, 125, 131; Gly+Ser 78, 133, 124; His 37, 38, 39% from 14 to 28 days, 56 to 70 days and 98 to 112 days, respectively. The third study aimed to determine daily N maintenance requirements (NMR), the genetic potential for daily N retention (NRmaxT) and ideal amino acids ratio for laying hens. One nitrogen balance trial was conducted, a total of 56 Hy-line W-36 laying hens from 28 to 30 weeks. The treatments consisted of six graded levels of nitrogen in the diets (N1=8; N2=16; N3=24; N4=32; N5=40 and N6=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= 292 mg/BWkg0.67 that was applied for further calculation of NRmaxT=1883 mg/BWkg0.67. A second nitrogen balance trial was conducted, a total of 96 Hy-line W-36 laying hens were used in the same period. Twelve treatments with eight replicates and one bird per cage were used. A balanced diet (BD) was formulated to meet the IAAR and the requirement of other nutrients for pullets. To formulate the deficient diets, the BD was diluted with corn starch to meet 45% of the amino acid requirement. The diets were again supplemented with vitamin, mineral, fiber, energy, and industrial amino acids sources to achieve the same levels of the BD, except for the amino acid to be evaluated in the treatment, which remain reduced in 55%. In each trial, the data of nitrogen intake, excretion, deposition, and retention were obtained in a balance trial. The b values were estimated by b=(ln(NRmaxT)-ln(NRmaxT-NR))/(NI)). Also, these data were used to calculate the requirements by the equation: Requirement=(EAA)BDx(2-DEL-(NDEAA/NDBD)). The bc-1 values were obtained dividing b by the dietary AA concentration. The IAAR by Goettingen approach was obtained by dividing the bc-1 from lysine by the bc-1 value from each other AA in each trial. The relation between the AA requirements with Lys requirements provided de IAAR by Louvain approach. The IAAR determined by Goettingen approach were Lys 100; Met+Cis 88, Trp 21, Thr 69, Arg 109, Val 90, Ile 75, Leu 127, Phe+Tir 110, Gly+Ser 73 e His 29%. A IAAR determinada pelo método de Louvain foi Lys 100, Met+Cys 88, Trp 21, Thr 69, Arg 104, Val 91, Ile 78, Leu 121, Phe+Tir 119, Gly+Ser 77 e His 29%. (AU)

FAPESP's process: 16/00536-6 - Determination of the ideal essential amino acid ratio for laying hens by deletion method
Grantee:Letícia Soares
Support Opportunities: Scholarships in Brazil - Doctorate