血液化學(xué)指標(biāo)和體溫結(jié)果表明豬只處于免疫應(yīng)激狀況（P＜0.03）。所有免疫應(yīng)激組蘇氨酸線性提高了蛋白沉積（P＜0.01）。從線性方程的斜率可以看出，蛋白沉積利用的標(biāo)準(zhǔn)可消化蘇氨酸的邊際利用效率不受免疫應(yīng)激狀態(tài)的影響。但是，從線性方程的截距來(lái)看，免疫應(yīng)激大幅度的提高了SID蘇氨酸的維持需要量（對(duì)照組VS應(yīng)激組，-11.2 VS -56.3， SE13.2； P＜0.05）。
Immune system stimulation increases dietary threonine requirements for protein deposition in growing pigs
Whitney D McGilvray, Hailey Wooten, Amanda R Rakhshandeh, Amy Petry, Anoosh Rakhshandeh
Previous studies have reported an increase in the utilization of threonine (Thr) during immune system stimulation(ISS). However, increased utilization of an AA during ISS may not reflect an increased dietary requirement, as endogenous sources may supply AA to meet the need for enhanced utilization. The current study evaluated the impact of ISS on components of dietary Thr requirements, i.e., maintenance requirement and the efficiency of Thr utilization. Thirty-nine gilts (initial BW 32 ± 2.1 kg) of commercially relevant genetics were individually housed in metabolism crates and fed one of six experimental diets in which Thr was the first limiting among other AA. Three levels of dietary Thr were tested within each ISS group: 70%, 90%, and 110% of daily Thr requirements, which were estimated based on the potential of each ISS group for protein deposition (PD). Following adaptation to the experimental diets, pigs from each dietary treatment group were injected with either increasing amounts of Escherichia coli lipopolysaccharide (ISS+; 25and 35 μg/kg BW) or saline (ISS−). Injections were given 48-h apart and whole-body nitrogen balance was measured for 72-h following the first injection. Body temperature (BT) was monitored and blood samples were collected 24 h after initiation of ISS and evaluated for measures of blood chemistry. Blood chemistry and BT results indicated an effective ISS in pigs (P < 0.03). Threonine intake increased PD in a linear fashion in both ISS groups (P < 0.01). The marginal efficiency of standardized ileal digestible (SID) Thr utilization for PD, represented by the slope, was not affected by ISS. However, ISS substantially increased the extrapolated maintenance SID Thr requirements, represented by the intercept at zero PD (ISS−vs. ISS+, −11.2vs. −56.3SE 13.2; P < 0.05). Collectively, our results indicated that the physiological changes associated with ISS increased the dietary SID Thr requirements for PD due to an increase in maintenance requirements.