A study was conducted to evaluate the effects of divergent genetic selection for residual feed intake (RFI) on nitrogen (N) metabolism and lysine utilization in growing pigs. Twenty-four gilts (body weight [BW] 66 ± 5 kg) were selected from generation nine of the low RFI (LRFI; n = 12) and high RFI (HRFI; n = 12) Iowa State University Yorkshire RFI selection lines. Six pigs from each genetic line were assigned to each of two levels of lysine intake: 70% and 100% of estimated requirements based on the potential of each genetic line for protein deposition (PD) and feed intake. For all diets, lysine was first limiting among amino acids. Using isotope tracer, N-balance, and nutrient digestibility evaluation approaches, whole-body N metabolism and the efficiency of lysine utilization were determined for each treatment group. No significant interaction effects of line and diet on dietary N or gross energy digestibility, PD, and the efficiency of lysine utilization for PD were observed. The line did not have a significant effect on PD and digestibility of dietary N and GE. An increase in lysine intake improved N retention in both lines (from 15.0 to 19.6 g/d, SE 1.44, in LRFI pigs; and from 16.9 to 19.8 g/d, SE 1.67, in HRFI pigs; P < 0.01). At the low lysine intakes and when lysine clearly limited PD, the efficiency of using available lysine intake (above maintenance requirements) for PD was 80% and 91% (SE 4.6) for the LRFI and HRFI pigs, respectively (P = 0.006). There were no significant effects of line or of the line by diet interaction on N flux, protein synthesis, and protein degradation. Lysine intake significantly increased (P < 0.05) N flux (from 119 to 150, SE 8.7 g/d), protein synthesis (from 99 to 117, SE 10.6 g of N/d), and protein degradation (from 85 to 100, SE 6.6 g of N/d). The protein synthesis-to-retention ratio tended to be higher in the LRFI line compared with the HRFI line (6.5 vs. 5.8 SE 0.62; P = 0.06), indicating a tendency for the lower efficiency of PD in this group. Collectively, these results indicate that genetic selection for low RFI is not associated with improvements in lysine utilization efficiency, protein turnover, and nutrient digestibility.

中文翻译：

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剩余饲料摄入量的不同选择对生长猪氮代谢和赖氨酸利用的影响。

进行了一项研究，以评估不同的遗传选择残留饲料摄入量（RFI）对生长猪的氮（N）代谢和赖氨酸利用的影响。从爱荷华州立大学约克郡RFI选择系的低RFI（LRFI; n = 12）和高RFI（HRFI; n = 12）的第9代中选出二十四头母猪（体重[BW] 66±5 kg）。每个遗传系的六头猪被分配到两个水平的赖氨酸摄入量：根据每个遗传系对蛋白质沉积（PD）和饲料摄入量的潜力，估计需求量的70％和100％。对于所有饮食，赖氨酸首先是氨基酸中的限制。使用同位素示踪，氮平衡和养分消化率评估方法，确定每个治疗组的全身氮代谢和赖氨酸利用效率。没有观察到家系和日粮对日粮氮或总能量消化率，PD和赖氨酸利用PD效率的显着影响。该品系对日粮氮和日粮的PD和消化率没有显着影响。赖氨酸摄入量的增加改善了两个品系中的氮保留（LRFI猪从15.0克/天，SE 1.44，SE 1.44； HRFI猪从16.9克/天，SE 1.67，SE 1.67； P <0.01）。在低赖氨酸摄入量和当赖氨酸明显限制PD时，LRFI和HRFI猪对PD使用可用赖氨酸摄入量（高于维持要求）的效率分别为80％和91％（SE 4.6）（P = 0.006）。品系或品系之间的饮食相互作用对氮通量，蛋白质合成和蛋白质降解均无显着影响。赖氨酸摄入量显着增加（P <0。05）氮通量（119至150，SE 8.7 g / d），蛋白质合成（99至117，SE 10.6 g N / d）和蛋白质降解（85至100，SE 6.6 g N / d ）。与HRFI品系相比，LRFI品系的蛋白质合成保留率趋于更高（6.5 vs. 5.8 SE 0.62； P = 0.06），表明该组中PD效率较低的趋势。总的来说，这些结果表明，低RFI的遗传选择与赖氨酸利用效率，蛋白质更新和营养物质消化率的提高无关。表明该组中PD效率较低的趋势。总的来说，这些结果表明，低RFI的遗传选择与赖氨酸利用效率，蛋白质更新和营养物质消化率的提高无关。表明该组中PD效率较低的趋势。总的来说，这些结果表明，低RFI的遗传选择与赖氨酸利用效率，蛋白质更新和营养物质消化率的提高无关。