RESUMO
Morada Nova is a Brazilian hair sheep breed that is well adapted to the country's mainly tropical climate and has good potential for meat and leather production. This breed is reported to be resistant to Haemonchus contortus infection, a highly desired characteristic due to the large impact of this parasite on sheep farming. Therefore, the present study aimed to characterize 287 recently weaned Morada Nova lambs and 123 ewes in relation to their resistance against H. contortus. The animals were dewormed and 15 days later artificially infected with 4000 H. contortus L3 (D0). They were individually monitored by periodic assessment of fecal egg count (FEC), packed cell volume (PCV), and live weight (LW). On D42, the sheep were again dewormed and submitted to a new parasitic challenge, following the same scheme. The animals of each category (lambs and ewes) were ranked according to individual mean FEC values, and classified as resistant (R, 20%), intermediate (I, 60%), or susceptible (S, 20%) to H. contortus infection. At weaning, high FEC were observed in all three phenotypes (P > 0.05). After the artificial infections, there was a significant difference (P < 0.05) among the three lamb phenotypes for the mean FEC (R < I < S), PCV (R > I > S), and LW (R = I > S). The infection levels (FEC) were negatively correlated with PCV (r = -0.66; P < 0.001), and LW (r = -0.30; P < 0.001). Despite this, the lambs were resilient, since more than 88% of these animals maintained the PCV above 24%, even when heavily infected. The importance of selective parasite control before weaning to reduce the negative impact on slaughter weight was evidenced, taking into account the high positive correlation between LW at weaning and final LW (r = 0.73; P < 0.001). The ewes, in turn, were strongly resistant to the parasite. Despite highly significant differences (P < 0.001) for mean FEC between phenotypes (R < I < S), 98% of the ewes maintained FEC below 4000 EPG. Their health was not affected, since PCV and LW did not differ between phenotypes, and these parameters were not significantly correlated with FEC (P > 0.05). With the phenotypic characterization performed here, it is possible to introduce procedures for parasite control in Morada Nova flocks, facilitating the target-selective treatment approach. The results of this study can also support improvement of meat production by the Morada Nova breed.
RESUMO
Morada Nova is a Brazilian hair sheep breed that is well adapted to the country's mainly tropical climate and has good potential for meat and leather production. This breed is reported to be resistant to Haemonchus contortus infection, a highly desired characteristic due to the large impact of this parasite on sheep farming. Therefore, the present study aimed to characterize 287 recently weaned Morada Nova lambs and 123 ewes in relation to their resistance against H. contortus. The animals were dewormed and 15 days later artificially infected with 4000 H. contortus L3 (D0). They were individually monitored by periodic assessment of fecal egg count (FEC), packed cell volume (PCV), and live weight (LW). On D42, the sheep were again dewormed and submitted to a new parasitic challenge, following the same scheme. The animals of each category (lambs and ewes) were ranked according to individual mean FEC values, and classified as resistant (R, 20%), intermediate (I, 60%), or susceptible (S, 20%) to H. contortus infection. At weaning, high FEC were observed in all three phenotypes (P>0.05). After the artificial infections, there was a significant difference (P<0.05) among the three lamb phenotypes for the mean FEC (RI > S), and LW (R=I > S). The infection levels (FEC) were negatively correlated with PCV (r = -0.66; P<0.001), and LW (r = -0.30; P<0.001). Despite this, the lambs were resilient, since more than 88% of these animals maintained the PCV above 24%, even when heavily infected. The importance of selective parasite control before weaning to reduce the negative impact on slaughter weight was evidenced, taking into account the high positive correlation between LW at weaning and final LW (r=0.73; P<0.001). The ewes, in turn, were strongly resistant to the parasite. Despite highly significant differences (P<0.001) for mean FEC between phenotypes (R0.05). With the phenotypic characterization performed here, it is possible to introduce procedures for parasite control in Morada Nova flocks, facilitating the target-selective treatment approach. The results of this study can also support improvement of meat production by the Morada Nova breed.
RESUMO
Due to the great economic impact of Haemonchus contortus on sheep farming, there is an increasing number of studies addressing host resistance against this nematode, including identification of directly related immune mechanisms. In this context, relative gene expression by RT-qPCR have been largely used, due to its rapidity, high sensitivity, specificity, and reproducibility. Although, appropriate reference gene selection is crucial for accurate interpretation of results. In this study, five reference genes (GAPDH, G6PDH, YWHAZ, ACTB, and B2M) were tested for expression stability in abomasum (fundic and pyloric regions) and abomasal lymph nodes of Morada Nova sheep classified as resistant (n = 5) or susceptible (n = 5) to H. contortus infection in a flock of 151 animals. GAPDH combined with YWHAZ were selected as reference genes for abomasal fundic region and abomasal lymph nodes, whereas YWHAZ was the most stable gene for abomasal pyloric region. These genes presented the lowest intra- and inter-group variations and, consequently, highest stability. In contrast, expression of G6PDH was the least stable in all tissues. The impact of reference gene selection was demonstrated by relative quantification of a pro-inflammatory cytokine (TNFα) in abomasal fundic region. Significant differences in TNFα expression levels between resistant and susceptible groups were only observed when the most stable genes (GAPDH combined with YWHAZ) or GAPDH were used as reference genes, whereas no significant differences were observed when other tested reference genes were used. It was demonstrated that normalization of expression data using inappropriate reference genes may significantly influence interpretation results.
Assuntos
Resistência à Doença , Haemonchus/imunologia , Reação em Cadeia da Polimerase em Tempo Real/normas , Ovinos/genética , Animais , Feminino , Marcadores Genéticos , Masculino , Especificidade de Órgãos , Reação em Cadeia da Polimerase em Tempo Real/veterinária , Padrões de ReferênciaRESUMO
ABSTRACT The tick Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Acari: Ixodidae) causes large economic losses to cattle breeders and its control is hampered by problems of resistance to the main commercial synthetic acaricides and the risk of residues in animal products. Alternative controls are important for the sustainability of cattle breeding in tropical regions, principally for organic milk production. This study evaluated the efficacy of a homeopathic preparation to control natural tick infestations. The evaluations were conducted with 24 taurine dairy cows during 12 months. The homeopathic medicine (30 CH + Sulfur 30 CH) was administered in a proportion of 1:100 (v/w) in a formulation with sugar, added to 30 kg of mineral salt. This preparation was supplied along with concentrated feed (2 kg/animal/day). The control group received the same feed mixture without the medicine. The groups were kept in separate paddocks. Data were collected on body weight, packed cell volume and number of engorged female ticks on each animal. Temperature, relative humidity and rainfall were recorded. Engorged females were collected from each group for in vitro comparison of reproductive parameters, and semi-engorged ticks for morpho-histological analysis. The mean results of body weight, packed cell volume and tick number were not statistically different between the control and treated groups: 616.5 kg and 618.6 kg; 27.9% and 27.3%; and 12.19 and 13.58 ticks, respectively. In the in vitro analyses, the average weights of the ticks (0.18 and 0.17 g) and eggs (0.07 and 0.06 g), larval hatching rate (70.1 and 76.6%) and reproductive efficiency index (54.3 and 60.6%) of the control and treated groups, respectively, also were not statistically different. Furthermore, no alteration in the ovaries was detected by microscopic analysis. Therefore, the homeopathic medicine was ineffective to control R. (B.) microplus, although the inclusion of agro-ecological practices might enhance its effect of homeopathy in controlling tick infestations.