de Gois Renata Brandão, do Prado Paim Tiago, Peres Rogério Fonseca Guimarães, Leão Karen Martins, Dos Santos Camila Alves, Bocchi Adriana Luize, Ferreira Josiel
Instituto Federal de Educação, Ciência E Tecnologia Goiano, Rio Verde, GO, 75901-970, Brazil.
Foco Consultoria Pecuária, Caçu, GO, 75816-000, Brazil.
Trop Anim Health Prod. 2025 Mar 1;57(2):88. doi: 10.1007/s11250-025-04342-6.
Residual feed intake (RFI) is one of the most used measure to assess feed efficiency. Animals with a negative RFI are considered more efficient, as they consume less feed than predicted for the observed weight gain. The RFI measures are commonly adjusted for subcutaneous fat thickness, however the energy efficiency detected by RFI may arise from reduced accumulation of visceral fat, an important energy storage for females during the reproductive cycle. Thus, the hypothesis evaluated here is that more efficient Nelore heifers have a lower body energy reserve, harming your reconception after the first calving as early primiparous (close to 24 months of age). Therefore, the present study aimed to evaluate whether there is a relationship between RFI adjusted for subcutaneous fat thickness and the reconception ability of early primiparous Nelore females and the relationships between growth, carcass traits, and reproduction according to RFI classification. Low and not significant correlations (phenotypic and genetic) were observed between RFI and reproductive traits, such as days to first conception (DFC), days to second conception (DSC), first gestation length (FGL), second gestation length (SGL), probability of second conception (PSC) and probability of second parturition (PSP). Reproductive traits exhibited low heritability (< 0.15), indicating limited potential for genetic selection in a tropical environment. In addition, the RFI classification had no influence on reproductive aspects. The results observed suggest that selection for more efficient animals did not affect the reconception of early primiparous females in the evaluated environment. However, these results can be affected by the environmental challenge imposed on these females. Therefore, obtaining similar data in other rearing environments would be interesting to explore the genotype by environment interaction in these traits' relationships. These findings are specific to the tested tropical environment, and the low heritability of reproductive traits may limit the potential for genetic improvement.
剩余采食量（RFI）是评估饲料效率最常用的指标之一。RFI为负值的动物被认为效率更高，因为它们消耗的饲料比根据观察到的体重增加所预测的要少。RFI测量通常会根据皮下脂肪厚度进行调整，然而，RFI检测到的能量效率可能源于内脏脂肪积累减少，内脏脂肪是雌性动物在生殖周期中的重要能量储存。因此，本研究评估的假设是，更高效的内罗牛小母牛身体能量储备较低，这会损害它们首次产犊后（作为早期初产母牛，接近24月龄）的再次受孕能力。因此，本研究旨在评估根据皮下脂肪厚度调整后的RFI与早期初产内罗牛雌性的再次受孕能力之间是否存在关系，以及根据RFI分类评估生长、胴体性状和繁殖之间的关系。在RFI与繁殖性状之间观察到低且不显著的相关性（表型和遗传相关性），如首次受孕天数（DFC）、第二次受孕天数（DSC）、首次妊娠期长度（FGL）、第二次妊娠期长度（SGL）、第二次受孕概率（PSC）和第二次分娩概率（PSP）。繁殖性状表现出低遗传力（<0.15），表明在热带环境中进行遗传选择的潜力有限。此外，RFI分类对繁殖方面没有影响。观察到的结果表明，在评估环境中选择更高效的动物不会影响早期初产雌性的再次受孕。然而，这些结果可能会受到施加在这些雌性动物身上的环境挑战的影响。因此，在其他饲养环境中获得类似数据，以探索这些性状关系中的基因型与环境相互作用，将是很有意义的。这些发现特定于所测试的热带环境，繁殖性状的低遗传力可能会限制遗传改良的潜力。
