Bioscience Methods 2025, Vol.16, No.6, 299-307 http://bioscipublisher.com/index.php/bm 3 00 This research focuses precisely on these key points. We will start from scratch to review the prevalence of gastrointestinal parasites in goats and their impact on production performance, to see exactly what are the major drawbacks of traditional drug control, and then shift our focus to genetic resistance to systematically assess its potential as a long-term solution. More importantly, we will identify and sort out the important genetic markers that have been discovered so far, and analyze their application value in actual breeding. This study aims to enhance the understanding of these resistance genetic mechanisms, promote more effective breeding strategies, improve the health of goats, increase production efficiency, and also provide a more stable and long-term path for the breeding system of small ruminants. 2 Immunological and Genetic Basis of Goat Resistance to Gastrointestinal Parasites 2.1 Immune response mechanisms of goats to major parasites Not all goats will show the same reaction when encountering Haemonchus contortus. Even if the immune system takes prompt action, it doesn't necessarily mean that the effect is equally good. Two types of immunoglobulins, IgA and IgE, are often mentioned. The level of the former is related to the number of parasites in the body, while the latter is more involved in the response to larvae (De La Chevrotiere et al., 2012; Shaw et al., 2023). Interestingly, some antigens seem to be targeted simultaneously by multiple stages of immune responses without a clear stage division. Goats that are more "resistant" usually have more prominent indicators - high levels of IgA and IgE, more eosinophils, and lower FEC. It can basically be seen that their ability to control parasites is indeed stronger. But this immune "tactic" does not rely solely on antibodies to function. Immune cells such as T cells, B cells and monocytes will also be mobilized. The transcriptome data also revealed some "operational pathways" behind this, such as the activation of inflammation-related signaling pathways like Th1/Th2 differentiation and NOD-like receptors (Figure 1) (Wang et al., 2024; Ndaba et al., 2025). In other words, the entire immune response is a multi-link linkage reaction rather than a single link fighting alone. 2.2 Overview of the genetic basis of resistance and susceptibility traits Relying on one gene to "carry the banner"? It is basically impossible for goats to resist parasites. It is a typical polygenic trait - immune regulation, stress response, and metabolic pathways all have to be involved to some extent. A group of genes such as CD1D, ITGA9, IL12A, IL13RA1, CD86, TGFB2 and TLR4 have been pointed out to play a role in responding to H. contortus infection (Estrada-Reyes et al., 2019; Mpofu et al., 2022). The problem is that the effects of each of these genes are not significant, so it might be too ideal to expect a significant improvement in resistance through just one round of breeding. For phenotypic indicators such as FEC and PCV, their heritability is between 0.1 and 0.4. They can be selected, but patience is required (Heckendorn et al., 2017). In recent years, genetic screening methods have indeed advanced significantly. Methods such as SNP typing and transcriptome analysis have become increasingly "handy" in identifying resistant alleles and have provided more precise technical tool support for the breeding process (Rocha et al., 2023). But for it to be truly put into use in production, it still needs to be carried out and iterated simultaneously. 2.3 Phenotypic indicators of resistance traits When it comes to determining whether a goat is resistant to parasites, apart from looking at the actual infection situation, several phenotypic indicators are also very valuable for reference. The most commonly used is FEC. The lower the value, the stronger the resistance. Some genetics studies show that its range is between 0.14 and 0.40. The FEC of well-performing goats can be about half lower than that of susceptible goats (Tsukahara et al., 2021). PCV is also an important indicator, especially for H. contortus with blood transfusion. A high PCV indicates less blood loss and strong resistance. The two are usually negatively correlated (Onzima et al., 2017), and a PCV lower than 20% suggests possible anemia problems. Another underestimated indicator is the weight recovery rate - goats that can stabilize or quickly regain weight during infection tend to be more disease-resistant. In addition, the antigenic reactions of IgA and IgE cannot be ignored, especially the targeting reactions to parasites. If the levels are high, it can basically be determined that the animal has strong resistance. Other hematological parameters such as hemoglobin content and mean corpuscular hemoglobin concentration are also negatively correlated with FEC, which plays an auxiliary role in identifying drug-resistant individuals (Mpofu et al., 2020).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==