J. Anim Sci.
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J. Anim. Sci. 2003. 81:1772-1780
© 2003 American Society of Animal Science

An evaluation of the NRC (1998) growth model in estimating lysine requirements of barrows with a lean growth rate of 348 g/d1,2

R. Wei3 and D. R. Zimmerman

Department of Animal Science, Iowa State University, Ames 50011

3 Correspondence:
Harvard School of Public Health, Department of Nutrition, 1633 Tremont Street, Boston, MA 02115.

Two experiments were conducted to evaluate the NRC (1998) growth model in predicting lysine requirements of high lean gain barrows by using plasma urea nitrogen as a rapid response criterion. In Exp. 1, 20 PIC barrows with an initial BW of 19.1 kg were used to estimate total lysine requirements at approximately 30 and 50 kg of BW in two separate randomized complete block designs. Another set of 20 PIC barrows with an initial BW of 59.0 kg was used to estimate total lysine requirements at about 70, 90, and 110 kg of BW in three separate, completely randomized designs. Pigs were individually penned and had free access to feed and water. Results indicated that total lysine requirements at 33, 52, 72, 93, and 113 kg of BW were 0.96 ± 0.01, 0.85 ± 0.02, 0.76 ± 0.05, 0.66 ± 0.03, and 0.49 ± 0.21% of the diet (18.6 ± 0.2, 20.1 ± 0.5, 22.6 ± 1.5, 18.7 ± 0.8, and 16.8 ± 7.2 g/d), respectively. The precision of the estimation decreased when pigs reached 70 kg of BW. To increase the precision, Exp. 2 was conducted in which 20 PIC barrows with an initial BW of 45.2 kg were repeatedly used in Latin square designs to estimate total as well as true ileal digestible lysine requirements at BW ranges of from 60 to 80, 80 to 100, and 100 to 120 kg, respectively. During the three BW range periods, the individually penned pigs were limited in feed intake to 2.6, 2.8, and 3.0 kg/d, respectively, and fed once daily. The estimated requirements in the three BW ranges were 21.8 ± 0.5, 18.8 ± 0.5, and 20.2 ± 0.7 g/d in total lysine and 19.9 ± 0.6, 17.0 ± 0.5, and 18.1 ± 0.6 g/d in true ileal digestible lysine, respectively. Total lysine requirements at approximately 30, 50, 70, 90, and 110 kg of BW were about 102, 98, 106, 92, and 99% of the NRC (1998) recommendations, respectively. The close agreement validated the NRC growth model in predicting lysine requirements of high lean gain barrows over the growing-finishing period.

Key Words: Growth Models • Lysine • Nutrient Requirements • Pigs






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