Paganoni B, Rose G, Macleay C, Jones C, Brown D J, Kearney G, Ferguson M, Thompson A N
J Anim Sci. 2017 Sep;95(9):3839-3850. doi: 10.2527/jas2017.1499.
The Australian sheep industry aims to increase the efficiency of sheep production by decreasing the amount of feed eaten by sheep. Also, feed intake is related to methane production, and more efficient (low residual feed intake) animals eat less than expected. So we tested the hypothesis that more efficient sheep produce less methane by investigating the genetic correlations between feed intake, residual feed intake, methane, carbon dioxide, and oxygen. Feed intake, methane, oxygen, and carbon dioxide were measured on Merino ewes at postweaning (1,866 at 223 d old), hogget (1,010 sheep at 607 d old), and adult ages (444 sheep at 1,080 d old). Sheep were fed a high-energy grower pellet ad libitum for 35 d. Individual feed intake was measured using automated feeders. Methane was measured using portable accumulation chambers up to 3 times during this feed intake period. Heritabilities and phenotypic and genotypic correlations between traits were estimated using ASReml. Oxygen (range 0.10 to 0.20) and carbon dioxide (range 0.08 to 0.28) were generally more heritable than methane (range 0.11 to 0.14). Selecting to decrease feed intake or residual feed intake will decrease methane (genetic correlation [] range 0.76 to 0.90) and carbon dioxide ( range 0.65 to 0.96). Selecting to decrease intake ( range 0.64 to 0.78) and methane ( range 0.81 to 0.86) in sheep at postweaning age would also decrease intake and methane in hoggets and adults. Furthermore, selecting for lower residual feed intake ( = 0.75) and carbon dioxide ( = 0.90) in hoggets would also decrease these traits in adults. Similarly, selecting for higher oxygen ( = 0.69) in hoggets would also increase this trait in adults. Given these results, the hypothesis that making sheep more feed efficient will decrease their methane production can be accepted. In addition, carbon dioxide is a good indicator trait for feed intake because it has the highest heritability of the gas traits measured; is cheaper, faster, and easier to measure than feed intake and has strong phenotypic and genetic correlations with feed intake. Furthermore, selection for feed intake, feed efficiency, methane, and carbon dioxide can be done early in sheep at postweaning age or hoggets. This early selection reduces the generation interval for breeding, thereby increasing response to selection.
澳大利亚养羊业旨在通过减少绵羊的采食量来提高养羊生产效率。此外，采食量与甲烷排放有关，生产效率更高（剩余采食量低）的动物采食量低于预期。因此，我们通过研究采食量、剩余采食量、甲烷、二氧化碳和氧气之间的遗传相关性，来检验更高效的绵羊产生更少甲烷这一假设。在断奶后（223日龄的1866只美利奴母羊）、育成羊（607日龄的1010只羊）和成年羊（1080日龄的444只羊）阶段，对美利奴母羊的采食量、甲烷、氧气和二氧化碳进行了测量。给绵羊自由采食高能生长颗粒饲料35天。使用自动喂食器测量个体采食量。在采食期内，使用便携式累积室测量甲烷，最多测量3次。使用ASReml估计性状之间的遗传力以及表型和基因型相关性。氧气（范围为0.10至0.20）和二氧化碳（范围为0.08至0.28）的遗传力通常高于甲烷（范围为0.11至0.14）。选择降低采食量或剩余采食量将减少甲烷（遗传相关性[]范围为0.76至0.90）和二氧化碳（范围为0.65至0.96）。选择降低断奶后绵羊的采食量（范围为0.64至0.78）和甲烷（范围为0.81至0.86），也会降低育成羊和成年羊的采食量和甲烷排放量。此外，选择降低育成羊的剩余采食量（=0.75）和二氧化碳（=0.90），也会降低成年羊的这些性状。同样，选择提高育成羊的氧气含量（=0.69），也会提高成年羊的这一性状。鉴于这些结果，可以接受让绵羊提高饲料效率会降低其甲烷产量这一假设。此外，二氧化碳是采食量的一个良好指示性状，因为在所测量的气体性状中，它具有最高的遗传力；比采食量更便宜、测量速度更快且更容易测量，并且与采食量具有很强的表型和遗传相关性。此外，可以在断奶后绵羊或育成羊阶段早期对采食量、饲料效率、甲烷和二氧化碳进行选择。这种早期选择缩短了育种的世代间隔，从而提高了选择反应。
