INRA, UMR1079 Systèmes d'Elevage, Nutrition Animale et Humaine, F-35590 Saint-Gilles, France.
J Anim Sci. 2010 Jun;88(6):2062-72. doi: 10.2527/jas.2009-2395. Epub 2010 Feb 12.
Genetic selection on residual feed intake (RFI) can be used as an alternative method to G:F to improve feed efficiency in pigs. The objective of this study was to determine the effects of selection for RFI on digestive and metabolic utilization of energy in 2 lines of purebred French Large White castrated male pigs obtained from a divergent selection experiment over 6 generations. The RFI(+) (high RFI) line consumed more feed than predicted from performance compared with the RFI(-) (low RFI) line. Digestibility of energy and nutrients, total heat production (HP), HP related to physical activity, and energy and N balance were measured in respiration chambers for a 6-d period in pigs offered feed ad libitum. Pigs remained in the chamber for an additional day and did not receive any feed to estimate the fasting HP and calculate the thermic effect of feeding. Five pairs of 2 littermates from the same farrowing batch were used in each line. Because 2 respiration chambers were available for the trial, pigs were measured regularly during the 25- to 95-kg growing period. Two pigs per chamber were used until pigs reached 45 kg of BW, and 1 pig per chamber was used thereafter. Individual feed intake and BW gain were measured continuously from weaning to the end of the trial. Pigs were fed 3 diets with decreasing CP contents during the 25 to 45 (period 1), 45 to 65 (period 2), and 65 to 95 (period 3) kg of BW periods. Average daily feed intake was greater in RFI(+) pigs than in RFI(-) pigs between 25 and 65 kg of BW (2,128 vs. 1,891 g/d; P < 0.01) and G:F was 8% greater in RFI(-) pigs compared with RFI(+) pigs (P < 0.01). There was no line effect on digestibility coefficients or N retention, irrespective of the experimental period studied. Nitrogen retention was 31.2, 28.7, and 20.8 g/d at periods 1, 2, and 3, respectively (P < 0.001). The HP was greater in RFI(+) pigs than in RFI(-) pigs (1,497 vs. 1,383 kJ.kg of BW(-0.60).d(-1); P < 0.01), with no subsequent line effect on energy retention. The activity-related HP tended to be greater in RFI(+) pigs than in RFI(-) pigs (250 vs. 218 kJ.kg of BW(-0.60).d(-1); P = 0.09), and the fasting HP was 10% greater (P = 0.04) in RFI(+) pigs than in RFI(-) pigs (846 vs. 771 kJ.kg of BW(-0.60).d(-1)). The thermic effect of feeding, expressed as a percentage of ME intake, was the same for both lines of pigs (average, 14.7%). In conclusion, the RFI(+) pigs are energetically less efficient because of their greater HP related to physical activity and basal metabolic rate.
遗传选择对残余采食量（RFI）的影响可以作为改善猪饲料效率的替代方法。本研究的目的是确定选择 RFI 对 2 个源自 6 代分歧选择试验的纯法裔大白去势公猪的能量消化和代谢利用的影响。与 RFI(-)（低 RFI）线相比，RFI(+)（高 RFI）线的采食量超过了性能预测。在自由采食的条件下，用呼吸室测量了 6 天的能量和养分消化率、总产热（HP）、与体力活动相关的 HP 和能量及氮平衡。猪在呼吸室中再停留一天，不喂食以估计空腹 HP 并计算饲料的热效应。每条线使用 5 对来自同一分娩批次的同窝 2 头仔猪。由于有 2 个呼吸室可供试验使用，因此在 25-95kg 生长期内定期测量猪的体重。每间房使用 2 头猪直到猪达到 45kg 的 BW，此后每间房使用 1 头猪。从断奶到试验结束，连续测量每头猪的饲料摄入量和体重增加量。在 25-45kg（第 1 期）、45-65kg（第 2 期）和 65-95kg（第 3 期）BW 期间，猪分别喂食 3 种 CP 含量逐渐降低的日粮。在 25-65kg BW 期间，RFI(+)猪的平均日采食量高于 RFI(-)猪（2128 比 1891g/d；P < 0.01），G:F 也比 RFI(-)猪高 8%（P < 0.01）。无论研究的实验期如何，在消化系数或氮保留方面均未观察到系间效应。氮保留分别为第 1、2 和 3 期的 31.2、28.7 和 20.8g/d（P < 0.001）。RFI(+)猪的 HP 高于 RFI(-)猪（1497 比 1383kJ.kg BW(-0.60).d(-1)；P < 0.01），随后的能量保留方面没有系间效应。与体力活动相关的 HP 似乎在 RFI(+)猪中高于 RFI(-)猪（250 比 218kJ.kg BW(-0.60).d(-1)；P = 0.09），并且 RFI(+)猪的空腹 HP 高 10%（P = 0.04）（846 比 771kJ.kg BW(-0.60).d(-1)）。以 ME 摄入量的百分比表示的饲料热效应在两条猪线上相同（平均为 14.7%）。总之，由于 RFI(+)猪与体力活动和基础代谢率相关的 HP 较高，因此其能量效率较低。
