Determining the digestible lysine requirement of 22 to 47 week-old Lohmann laying hens using two requirement titration methodologies

digestible lysine;laying hens;broken line regression;quadratic polynomial regression

Spangler, Haley Lynn ; Parsons ; Carl M.

关键词: digestible lysine;    laying hens;    broken line regression;    quadratic polynomial regression;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/88101/SPANGLER-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Over the past 15 to 40 years, genetic improvements have been made to obtain higher egg production for commercial laying hens. In addition to genetic progress, there have been substantial changes in environmental management, cage density and feed ingredient quality. These changes have resulted in more efficient bird, and there is evidence that their nutrient requirements may have changed. Lysine (Lys), is an essential and usually the second limiting amino acid (AA) in poultry diets and its requirement is especially important because it is used as the reference AA when utilizing the ideal protein concept in feed formulation. When using this method, it is very important that the Lys requirement be accurate; failure to do so may result in errors in requirements for all other AAs included in the diet. Therefore, a study was conducted in order to determine the digestible Lys (DLYS) requirement of modern day laying hens using two different titration methods. One thousand six hundred and eighty Lohmann LS Lite caged hens were allotted to 15 dietary treatments using increasing crude protein (CP) or constant CP DLYS titration methodologies from 22 to 47 weeks of age. From Week 0 to 11 for the increasing CP series, the dietary DLYS and CP levels increased from 0.565 to 0.980% and 13.8 to 21.7%, respectively. At Week 12, DLYS levels were decreased to .468to.845% and CP levels were decreased to 12.2 to 19.3%; these levels were fed for the remainder of the experiment. For the constant CP series, DLYS levels increased from 0.565 to 0.980% while CP remained relatively constant at 16%. Again, at Week 12 of the trial, DLYS levels were decreased to range from 0.468 to 0.845%, with a constant CP at 14%. An industry control diet with a DLYS level of 0.807% and 18.5% CP was fed for Weeks 0 to 11. At Week 12, the DLYS and CP levels were adjusted to 0.688% and 15.3%, respectively. Increasing DLYS had a significant effect (P< 0.05) on egg production, egg weight, egg mass and feed efficiency for both titration methods. However, increasing DLYS generally had no significant effect on percentage of egg yolk, white and solids. Broken line regression, the maximum of the quadratic polynomial (QP max) regression, and the intercept of the broken line and QP were calculated and used to estimate the DLYS requirement for egg production, egg mass, and feed efficiency. Broken line regression consistently yielded the lowest requirements and QP max regression yielded the highest, with the intersection of the broken line and QP max method yielding an intermediate requirement estimate. For example, when using the increasing CP titration method, the DLYS requirements for egg mass were 655, 817 and 706 mg/hen/d for the broken line, QP max, and the intercept of the broken line and QP regression methods, respectively. The DLYS for egg production was generally lower than that for egg mass and feed efficiency. When using the constant CP titration method, the DLYS requirements for egg mass were 703, 863 and 772 mg/hen/d for the broken line, QP max, and the intercept of the broken line and QP regression methods, respectively. The DLYS requirement estimated using the constant CP titration method were more variable and less precise than the requirements estimated using the increasing CP titration method.