Use of plasma urea nitrogen as a rapid response criterion to determine the lysine requirement of pigs2

Abstract

Five experiments were conducted to evaluate the potential use of plasma urea N (PUN) concentrations as a rapid response criterion to determine amino acid requirements. A preliminary experiment (Exp. 1) indicated that a 3-d feeding time was required to re-equilibrate PUN concentrations after a change in the dietary concentration of lysine. In Exp. 2, 3, and 4, PUN was used to estimate the lysine requirement of growing pigs at different specific BW. Thirty individually penned crossbred pigs weighing 32 and 44 kg in Exp. 2 and 3, respectively, were assigned to five dietary treatments (.60, .70, .80, .90, and 1.00% lysine) for 5 d. The PUN decreased quadratically (P < .05) to increasing dietary lysine. A two-slope, broken-line regression model estimated the requirement at .85% in Exp. 2 and at .76% in Exp. 3. In Exp. 4, 60 crossbred pigs (30 barrows and 30 gilts) weighing 70 kg were assigned to five dietary lysine concentrations: .50, .60, .70, .80, and .90% for 4 d. Increasing lysine caused PUN to decrease quadratically (P < .01). The estimated requirements were different (P < .05) between sexes: .69% for barrows and .75% for gilts. In Exp. 5, the validity of using PUN as a rapid response criterion was verified by comparing the estimated lysine requirement based on PUN with the requirement determined in a 7-d N balance. Twenty crossbred barrows averaging 19 kg were used. Dietary lysine concentrations were .60, .75, .90, 1.05, and 1.20%. A quadratic response was observed in PUN (P < .05) and N retention (NR) (P < .01) with increasing lysine. The estimated lysine concentrations that maximized rates of NR and minimized PUN (1.03 vs. 1.05) were not different (P > .10). Therefore, PUN concentrations can be used in short-term trials to accurately estimate the dietary lysine required to maximize total N utilization in pigs at a specific BW. In addition, the two-slope broken-line regression model had the highest R2 and the lowest mean square error compared with three other models as means for estimating lysine requirement from PUN concentrations.

Lysine requirement of starting barrows from two genetic groups fed on low crude protein diets

“…PUN generally shows a high variance (Coma et al, 1995) and in some studies, PUN was not efficient to determine the lysine requirement (Fontes et al,.1999;Gasparotto et al, 2001;Hannas et al, 2000;Moreira et al, 2002. In this trial, the CCGG showed greater values of standard deviation for PUN than DLGG (Table 2).…”

“…The PUN, the result of amino acid catabolism, indicates the capacity of utilization of intake nitrogen by the animal (Brown and Cline, 1974). It's used for amino acid requirement determinations (Coma et al, 1995). In this trial, the DLGG showed quadratic response of the PUN (P=0.05).…”

Estimation of α-tocopherol concentration necessary to optimise lamb meat quality stability during storage in high-oxygen modified atmosphere using broken-line regression analysis

“…This indicates that the concentration of 2.26 mg a-tocopherol/kg meat would be the maximum concentration obtained most efficiently. Broken-line regression analysis has been used satisfactorily to estimate the requirements of nutrients in some species such as lysine in pigs (Coma et al, 1995), isoleucine in pigs (Robbins et al, 2006) and vitamin E in fish (Shiau and Shiau, 2001;Lin and Shiau, 2005). The only reference found concerning the application of broken-line regression analysis to determine the optimum dietary supplementation of vitamin E in lambs was in Lopez Bote et al (2001).…”

Exigência de Lisina, com Base no Conceito de Proteína Ideal, para Suínos Machos Castrados de Dois Grupos Genéticos, na Fase de Crescimento

“…O mesmo comportamento foi obtido por COMA et al (1995), que, trabalhando com suínos de 32 a 36 kg de peso vivo, obtiveram efeito quadrático dos níveis de lisina sobre a concentração de NUP, com menor nível em 0,85% de lisina na ração, portanto inferior àquele estimado no presente experimento.…”