| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
* Department of Animal Science, University of Tennessee, Knoxville 37996-4588; and
and
Louisiana State University Agricultural Center, Baton Rouge 70803
2 Corresponding author: krobbins{at}utk.edu
We evaluated and compared various broken-line regression models and SAS (SAS Inst. Inc., Cary, NC) procedures for estimating nutrient requirements from nutrient dose response data. We used the SAS (Version 9) procedures NLIN and NLMixed and the response data of Parr et al. (2003), who evaluated the isoleucine requirement of growing swine. The SAS NLIN was used to fit 2 different broken-line regression models: a simple 2 straight-line, one-breakpoint model and a quadratic broken-line model in which the response below the single breakpoint was quadratic; there was a plateau above the breakpoint. The latter was fit using 2 different approaches in NLIN. We also used SAS NLMixed to fit 3 different broken-line models: the 2 straight-line, one-breakpoint model that included a random component for the plateau; the quadratic broken-line model that included a random component for the plateau; and the quadratic broken-line model that included random components for both the plateau and the slope of the curve below the requirement. The best fit (greater adjusted R2; least log likelihood) was achieved using SAS NLMixed and the quadratic model with a random component for asymptote included in the model. Model descriptions, SAS code, and output are presented and discussed. Additionally, we provide other examples of possible models and discuss approaches to handling difficult-to-fit data.
Key Words: nonlinear regression • nutrient requirement
This article has been cited by other articles:
|
|
 |
|
  W. A. Dozier III, A. Corzo, M. T. Kidd, and M. W. Schilling Dietary Digestible Lysine Requirements of Male and Female Broilers from Forty-Nine to Sixty-Three Days of Age Poult. Sci., July 1, 2008; 87(7): 1385 - 1391. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. P. Fan, M. Xie, W. W. Wang, S. S. Hou, and W. Huang Effects of Dietary Energy on Growth Performance and Carcass Quality of White Growing Pekin Ducks from Two to Six Weeks of Age Poult. Sci., June 1, 2008; 87(6): 1162 - 1164. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Q. Zebeli, J. Dijkstra, M. Tafaj, H. Steingass, B. N. Ametaj, and W. Drochner Modeling the Adequacy of Dietary Fiber in Dairy Cows Based on the Responses of Ruminal pH and Milk Fat Production to Composition of the Diet J Dairy Sci, May 1, 2008; 91(5): 2046 - 2066. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Bregendahl, S. A. Roberts, B. Kerr, and D. Hoehler Ideal Ratios of Isoleucine, Methionine, Methionine Plus Cystine, Threonine, Tryptophan, and Valine Relative to Lysine for White Leghorn-Type Laying Hens of Twenty-Eight to Thirty-Four Weeks of Age Poult. Sci., April 1, 2008; 87(4): 744 - 758. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Simard, F. Guay, C. L. Girard, A. Giguere, J.-P. Laforest, and J. J. Matte Effects of concentrations of cyanocobalamin in the gestation diet on some criteria of vitamin B12 metabolism in first-parity sows J Anim Sci, December 1, 2007; 85(12): 3294 - 3302. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. C. Kendall, A. M. Gaines, B. J. Kerr, and G. L. Allee True ileal digestible tryptophan to lysine ratios in ninety- to one hundred twenty-five-kilogram barrows J Anim Sci, November 1, 2007; 85(11): 3004 - 3012. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. N. Dilger, T. A. Garrow, and D. H. Baker Betaine Can Partially Spare Choline in Chicks but Only When Added to Diets Containing a Minimal Level of Choline J. Nutr., October 1, 2007; 137(10): 2224 - 2228. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. N. Dilger and D. H. Baker Oral N-acetyl-L-cysteine is a safe and effective precursor of cysteine J Anim Sci, July 1, 2007; 85(7): 1712 - 1718. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
