Publications by authors named "Sérgio Novita Esteves"

16 Publications

  • Page 1 of 1

Ovine β-globin gene: A new qPCR for rapid haplotype identification and association with susceptibility to Haemonchus contortus infection.

Vet Parasitol 2021 Jun 27;294:109434. Epub 2021 Apr 27.

Embrapa Pecuária Sudeste, Rodovia Washington Luiz, Km 234 s/n, Fazenda Canchim, PO Box 339, 13560-970, São Carlos, SP, Brazil.

Two β-globin allelic haplotypes (A and B) were identified in domestic sheep, wherein animals which are homozygous for β allele (BB haplotype) have a deletion of pre-adult β-globin and consequently are less tolerant to anemia and hypoxia. Since Haemonchus contortus infection, is associated with severe anemia, studies performed from 1960s to 1990s investigated the association between β-globin haplotype and resistance against this parasite. However, the findings were controversial, pointing out from increased resistance in animals harboring the β allele to inexistence of association. Thus, our study aimed to develop a qPCR for β-globin haplotype identification, and to evaluate the association between β-globin haplotype and resistance against H. contortus in a group of sheep submitted to artificial infection with this parasite. A total of 286 lambs of Morada Nova breed were experimentally challenged with 4000 H. contortus L3 and monitored for 112 days from weaning. Significantly improved (p < 0.05) phenotypic profiles (lower fecal egg counts, higher packed cell volume and birthweight) were observed for AA haplotype animals, especially when compared to BB animals, while AB animals were similar to BB. This is the first report of a qPCR assay for ovine β-globin haplotype identification. In view of significant differences of phenotypic profiles between haplotype groups, the developed qPCR may constitute an important tool for sheep producers to improve genetic selection of parasite resistant animals.
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http://dx.doi.org/10.1016/j.vetpar.2021.109434DOI Listing
June 2021

Anthelmintic resistance of Haemonchus contortus from sheep flocks in Brazil: concordance of in vivo and in vitro (RESISTA-Test©) methods.

Rev Bras Parasitol Vet 2021 3;30(2):e025120. Epub 2021 May 3.

Embrapa Pecuária Sudeste - CPPSE, São Carlos, SP, Brasil.

This study evaluated the resistance status of Haemonchus contortus from sheep flocks in the state of São Paulo, Brazil, through comparison between the fecal egg count reduction test (FECRT) and the larval development test (LDT). For the FECRT, 35 sheep were selected in each of five flocks and divided into groups treated with: benzimidazole, levamisole, ivermectin, monepantel and control. Feces were collected for EPG and fecal cultures. The LDT was performed using thiabendazole (TBZ), levamisole (LEV), ivermectin aglycone (IVM-A) and Zolvix (ZLV). Resistance to all drugs was detected using FECRT in 100% of the flocks, except in relation to ZLV (40% resistant and 20% suspected of resistance). LDT indicated resistance to TBZ and IVM-A in all flocks, to LEV in 80% of flocks and to ZLV in 10%. Total agreement was obtained between the two tests for TBZ and IVM (k = 1.0), while for LEV (k = 0.8) and ZLV (k = 0.9), substantial and almost perfect agreement were obtained, respectively. The concordance between the tests was significant, thus showing that it is possible to use the outcome of the LDT to predict the FECRT, and hence validating the former as a fast diagnostic test for use by sheep farmers in Brazil.
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http://dx.doi.org/10.1590/S1984-296120201093DOI Listing
May 2021

NonSurgical Embryo Recovery from Estrus-Synchronized or Superovulated Morada Nova Ewes: A Feasible Strategy for Sheep Embryo Banking.

Biopreserv Biobank 2021 Mar 25. Epub 2021 Mar 25.

Embrapa Caprinos e Ovinos, Coronel Pacheco, Brazil.

This study assessed the feasibility of embryo production and nonsurgical embryo recovery (NSER) in Morada Nova ewes (an endangered native Brazilian breed of sheep) subjected to different estrus synchronization and/or superovulation protocols. Ewes received intravaginal sponges soaked with 60 mg medroxyprogesterone acetate (MAP), which were kept in place for six (G6;  = 12), nine (G9;  = 12), or 12 (G12;  = 12) days. Half of the ewes in each group remained estrus synchronized only () and the other half was superovulated () with 133 mg porcine follicle-stimulating hormone (pFSH). There were no differences ( > 0.05) in antral follicle counts determined with ultrasonography 60 hours before MAP sponge removal (or at the time of the first pFSH dose) among G6 (6.4 ± 0.9), G9 (6.2 ± 0.7), and G12 (5.5 ± 0.6). Estrus responses and NSER success rates did not vary ( > 0.05) among the three progestin-treatment groups of ewes for either estrus-induced or superovulated animals. The onset of estrus occurred 10-12 hours later ( < 0.01) in G9 ewes compared with G6 and G12 and the duration of estrus was ∼19 hours greater ( < 0.01) in G9 than in G6. The average duration of the NSER procedure was 32.6 ± 1.3 minutes. At least one structure was recovered in 85.7% of synchronized and in 87.5% of superovulated ewes. Viable embryo recovery rates were also similar ( > 0.05) for G6 (1.0 ± 0.3 and 2.5 ± 1.5), G9 (1.3 ± 0.5 and 4.8 ± 2.0), and G12 groups (1.0 ± 0.3 and 4.8 ± 2.3; estrus-synchronized and superovulated ewes, respectively). In conclusion, progestogen pretreatment of different durations and NSER can be employed in Morada Nova ewes, resulting in reasonable viable embryo recovery rates in both estrus-synchronized and superovulated animals. Therefore, both techniques are suitable for use in commercial settings as well as small ruminant conservation programs.
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http://dx.doi.org/10.1089/bio.2020.0125DOI Listing
March 2021

Luteotropic effects of human chorionic gonadotropin administered 7.5 days after synchronous estrous induction in Morada Nova ewes.

Anim Reprod Sci 2020 Dec 2;223:106644. Epub 2020 Nov 2.

Department of Pathobiology and Veterinary Theriogenology, School of Agricultural and Veterinarian Sciences, São Paulo State University, Jaboticabal, SP, Brazil; Embrapa Caprinos e Ovinos, Rodovia MG 133, Km 42, Cep 36.155-000, Coronel Pacheco, MG, Brazil. Electronic address:

This study was conducted in ewes to assess effects of human chorionic gonadotropin (hCG) administration after imposing an estrous induction treatment regimen. Ewes (n = 115) were treated with a 60 mg medroxyprogesterone-intravaginal-sponge for 6 d plus 200 IU of equine chorionic gonadotropin (eCG) im and 37.5 μg d-cloprostenol im 36 h before sponge removal (Day 0). After natural mating, ewes having at least one corpus luteum (CL; n = 108) were administered either 1 mL of saline (G-Control; n = 53) or 300 IU of hCG (G-hCG; n = 55) on Day 7.5 after sponge removal (Day 0). Ovarian ultrasonography and blood collection were performed on Days 7.5, 13.5, 17.5, 21.5, and 30.5. Accessory CL (aCL) were observed in 81.5 % (G-hCG) and 0.0 % (G-Control) of ewes (P = 0.0001). Diameter, area, and volume of luteal tissue were greater (P < 0.05) in G-hCG from Day 13.5 to 30.5. Progesterone (P) concentrations were greater (P < 0.05) on Days 13.5, 17.5, 21.5 and 30.5 for ewes of the G-hCG group. Pregnancy percentage was similar (P = 0.25) between groups [47.1 % (G-control) compared with 60.0 % (G-hCG)], although total number of lambs produced by estrous synchronized ewes was greater (P = 0.005) in ewes of the G-hCG group (90.9 % compared with 66.0 %). In conclusion, hCG administration 7.5 days after sponge removal from Morada Nova ewes during the non-breeding season is an effective treatment to induce aCL formation, improve luteal tissue biometry and P4 concentrations, and to enhance the total number of lambs born.
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http://dx.doi.org/10.1016/j.anireprosci.2020.106644DOI Listing
December 2020

Morada Nova sheep breed: Resistant or resilient to infection?

Vet Parasitol X 2019 Nov 9;2:100019. Epub 2019 Oct 9.

Embrapa Pecuária Sudeste, Rodovia Washington Luiz, Km 234 s/n, Fazenda Canchim, PO Box 339, CEP 13560-970, São Carlos, SP, Brazil.

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 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 . The animals were dewormed and 15 days later artificially infected with 4000 L (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 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.
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http://dx.doi.org/10.1016/j.vpoa.2019.100019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7458387PMC
November 2019

Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes.

Parasite Immunol 2020 12 18;42(12):e12790. Epub 2020 Sep 18.

Embrapa Pecuária Sudeste, São Carlos, Brazil.

Aims: Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes were evaluated.

Methods And Results: Lambs were ranked through faecal egg counts (FEC) after two parasitic challenges with 4,000 H.contortus L . After the second challenge, the lambs underwent a third artificial infection and were euthanized 7 days later. Immune-related genes were quantified locally in abomasal mucosa and lymph nodes (CD4, IFNγ, IL4, IL5, IL13, IL2RA and MS4A2) and systemically in the whole blood (IL4 and IL13). Anti-H. contortus IgG and IgA antibodies and eosinophils and mast cells counts were also investigated. Resistant animals presented higher systemic IgG and IgA titres, both negatively correlated with FEC. Susceptible animals had higher blood levels of IL4 transcripts. At the local level, resistant lambs had higher eosinophils counts and superior MS4A2 levels in abomasal fundic mucosa, besides higher IgA levels in abomasal mucus, while susceptible lamb had superior IL4 expression in abomasal lymph nodes.

Conclusion: These data indicate that resistant lambs had an immune response mediated by antibody-mediated cytotoxicity. Also, the systemic humoral profile, particularly IgA isotype, seems to be a good resistance marker for Morada Nova sheep, as we found differences between groups even when FEC did not differ.
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http://dx.doi.org/10.1111/pim.12790DOI Listing
December 2020

Innate Immune Responses Associated with Resistance against in Morada Nova Sheep.

J Immunol Res 2019 11;2019:3562672. Epub 2019 Nov 11.

Embrapa Pecuária Sudeste, Rodovia Washington Luiz, Km 234, Fazenda Canchim, 339, 13560-970 São Carlos, SP, Brazil.

The immune response against infections is primarily associated with the Th2 profile. However, the exact mechanisms associated with increased sheep resistance against this parasite remains poorly elucidated. The present study is aimed at evaluating mediators from the innate immune response in lambs of the Morada Nova Brazilian breed with contrasting . resistance phenotypes. Briefly, 287 lambs were characterized through fecal egg counts (FEC) and packed cell volume (PCV) after two independent experimental parasitic challenges with 4,000 H. L. 20 extreme resistance phenotypes (10 most resistant and 10 most susceptible) were selected, subjected to a third artificial infection with 4,000 L, and euthanized 7 days later. Tissue samples were collected from abomasal fundic and pyloric mucosa and abomasal lymph nodes. Blood samples were collected at days 0 and 7 of the third parasitic challenge. RNA was extracted from tissue and blood samples for relative quantification of innate immune-related genes by RT-qPCR. For the abomasal fundic mucosa, increased and expression levels ( < 0.05) were found in the susceptible animals, while resistant animals had superiorly expressed ( < 0.05). Higher levels ( < 0.05) of and were found in the abomasal pyloric mucosa of resistant animals. was at higher levels ( < 0.05) in the blood of susceptible lambs, at day 0 of the third artificial infection. The exacerbated proinflammatory response observed in susceptible animals, at both local and systemic levels, may be a consequence of high . parasitism. This hypothesis is corroborated by the higher blood levels of before the onset of infection, which probably remained elevated from the previous parasitic challenges. On the other hand, resistant lambs had an enhanced response mediated by TLR recognition and complement activation. Nevertheless, this is the first study to directly associate sheep parasitic resistance with IL33, an innate trigger of the Th2-polarized response.
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http://dx.doi.org/10.1155/2019/3562672DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6877983PMC
April 2020

Extreme-QTL mapping of monepantel resistance in Haemonchus contortus.

Parasit Vectors 2019 Aug 14;12(1):403. Epub 2019 Aug 14.

Instituto de Biociências de Botucatu, Universidade Estadual Paulista (UNESP), Rua Prof. Dr. Antônio Celso Wagner Zanin, 250, Distrito de Rubião Junior, Botucatu, SP, CEP 18618-689, Brazil.

Background: Haemonchus contortus, a gastrointestinal nematode parasite of sheep, is mainly controlled by anthelmintics; the occurrence of anthelmintic resistance leads to treatment failures and increases economic burden. Because molecular mechanisms involved in drug resistance can be elucidated by genomic studies, an extreme quantitative trait locus (X-QTL) mapping approach was used to identify co-segregation of the resistance phenotype with genetic markers to detect the genome-wide variants associated with monepantel resistance in H. contortus.

Methods: A cross between H. contortus isolates using parental susceptible (Par-S) males and monepantel resistant (Par-R) females resulted in SR progeny, while reciprocal cross resulted in RS progeny. Pools (n = 30,000) of infective larvae (L3) recovered from Par-R, and from SR and RS populations in the F3 generation, collected both before (unselected group) and 7 days after (selected group) selection with monepantel treatment in sheep hosts, were subjected to genome sequencing (Pool-Seq). Pairwise comparisons of allele frequencies between unselected and selected groups were performed for each population by Fisher's exact test (FET) and for both populations combined by a Cochran-Mantel-Haenszel (CMH) test.

Results: Mapping rates varied from 80.29 to 81.77% at a 90.4X mean coverage of aligned reads. After correction for multiple testing, significant (P < 0.05) changes in allele frequencies were detected by FET for 6 and 57 single nucleotide polymorphisms (SNPs) in the SR and RS populations, respectively, and by the CMH test for 124 SNPs in both populations. The significant variants located on chromosome 2 generated a selection signal in a genomic region harboring the mptl-1, deg-3 and des-2 genes, previously reported as candidates for monepantel resistance. In addition, three new variants were identified in the mptl-1 gene.

Conclusions: This study expands knowledge on genome-wide molecular events underlying H. contortus resistance to monepantel. The identification of a genome region harboring major genes previously associated with monepantel resistance supports the results of the employed X-QTL approach. In addition, a deletion in exon 11 of the mptl-1 gene should be further investigated as the putative causal mutation leading to monepantel resistance.
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http://dx.doi.org/10.1186/s13071-019-3663-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6693152PMC
August 2019

Comparison of the intravenous and intravaginal route of oxytocin administration for cervical dilation protocol and non-surgical embryo recovery in oestrous-induced Santa Inês ewes.

Reprod Domest Anim 2019 Sep 25;54(9):1230-1235. Epub 2019 Jul 25.

Embrapa Caprinos e Ovinos, Sobral-CE, Brazil.

This study compared the effects of intravaginal and intravenous routes of oxytocin (OT) administration in 46 oestrous-induced Santa Inês ewes (6-day treatment with progestin-releasing intravaginal sponges and a single injection of 200 IU of eCG at the time of sponge removal) that underwent transcervical embryo recovery 6-7 days after oestrous onset and mating. All ewes received 37.5 μg of d-cloprostenol via latero-vulvar route, and 1 mg of oestradiol benzoate i.m. 16 hr before and 50 IU of OT 20 min before non-surgical embryo recovery (NSER), with OT being administered intravenously (n = 21) or intravaginally (n = 21). An overall oestrous response was 95.6% (44/46), and adequate cervical retraction could be accomplished in 78.6% (33/42) of ewes. The percentage of successful NSER procedures was 57% (24/42) or 72.7% (24/33) of animals with sufficient cervical retraction. The duration of NSER procedure averaged 28 min (range: 17-40 min) and ~96% of flushing fluid could be recovered (range: 85%-100%). Out of 18 ewes that could not undergo NSER, 12 (66.6%) presented various anatomical barriers, whilst the other 33.4% did not present these barriers and still could not be traversed. Excluding the ewes with those anatomical features, the overall success rate of NSER was 80% (24/30). The route of OT administration had no effect on NSER efficiency or the ease with which transcervical embryo flushing was performed. Both routes of OT administration can be used for cervical dilation protocol. Discarding ewes with anatomical features precluding cervical penetration is highly recommended to increase the efficacy of NSER in sheep.
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http://dx.doi.org/10.1111/rda.13499DOI Listing
September 2019

Productive performance and reproductive characteristics of Morada Nova male lambs fed with high-energy diet.

Trop Anim Health Prod 2019 Nov 13;51(8):2481-2491. Epub 2019 Jun 13.

Laboratory of Animal Reproduction, Brazilian Agricultural Research Corporation, Embrapa Southeast Livestock/Embrapa Pecuária Sudeste (CPPSE/Embrapa), Rod. Washington Luiz, km 234, São Carlos, 13560-970, Brazil.

Morada Nova breed sheep are without wool, tropicalized, small-sized animals, known for their high-quality meat and skin. Their body development naturally depends on the genetic potential and adequate nutritional support, which suggests that the offer of high-energy density diets positively influences their productive indicators. Thus, the present study investigated the effect of a high-energy diet for the Morada Nova lambs on body development and testicular function, considering their histomorphometric characteristics and seminal quality. Forty-two males (19.2 weeks, 20.7 ± 3.5 kg) were equally divided into two groups and fed with 2.05 Mcal (G7, n = 21) or 2.37 Mcal (G24, n = 21) of metabolizable energy/day, equivalent to 7% and 24% above the minimum for growing lambs. The animals were confined for 23 weeks (W0 to W23). Weight and body score differed significantly from the W1 (P < 0.05). From the W5, thoracic perimeter, body length, wither height, and rump attributes were higher in G24 (P < 0.05). The scrotal circumference and testicular volume were higher in G24 from the W3 (P < 0.05). Although testosterone levels were not affected (P = 0.05), the highest energy intake increased the diameter of the seminiferous tubules and the development of the epididymal epithelium (P < 0.05). This positively influenced the seminal quality and reduced the minor defects (21.87% vs. 17.13%) and the total spermatic defects (26.34% vs. 21.78%, P < 0.05). Thus, it is possible to employ higher levels of dietary energy for Morada Nova young males to express higher productive efficiency and earlier reproductive attributes of interest.
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http://dx.doi.org/10.1007/s11250-019-01969-0DOI Listing
November 2019

Morada Nova sheep breed: Resistant or resilient to Haemonchus contortus infection?

Vet Parasitol 2019 9;276S:100019. Epub 2019 Oct 9.

Embrapa Pecuária Sudeste, Rodovia Washington Luiz, Km 234 s/n, Fazenda Canchim, PO Box 339, CEP 13560-970, São Carlos, SP, Brazil. Electronic address:

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 L (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.
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http://dx.doi.org/10.1016/j.vpoa.2019.100019DOI Listing
October 2019

Differences in the thermal sensitivity and seminal quality of distinct ovine genotypes raised in tropical conditions.

Theriogenology 2019 Jan 29;123:123-131. Epub 2018 Sep 29.

Laboratory of Animal Reproduction, Brazilian Agricultural Research Corporation, Embrapa Southeast Livestock (CPPSE/Embrapa), São Carlos, SP, Brazil. Electronic address:

For different ovine breeds to maximize their reproductive capacity in countries with tropical climate, it is important to evaluate their potential for thermal resilience and consequences on their reproductive traits. Therefore, the objective of this study was to evaluate the effect of thermal environment temperatures of climate seasons in a tropical climate region on the surface temperatures of the scrotum, testicular biometric characteristics, seminal quality and serum testosterone concentration of rams of different genotypes. Breeders of four different genotypes (Dorper, n = 8, Texel, n = 8, Santa Inês, n = 9 and Morada Nova, n = 8) were used throughout the four climate seasons. Higher thermal challenge was recorded in the spring and summer. In the summer increase in scrotal surface temperature was detected by infrared thermography (P < 0.05), mainly in the regions of the distal testicular pole and tail of the epididymis. The animals of the Texel genotype had higher rectal temperature in the summer. In spring, this genotype also had the highest testicular pole (32.2 ± 0.5 °C; P < 0.05) and distal (29.9 ± 0.4 °C; P < 0.05) temperatures and a higher mean testicular temperature (31.7 ± 0.4 °C; P < 0.05). The Morada Nova genotype showed a higher surface temperature gradient between testicular poles (2.96 ± 0.1 °C; P < 0.05), especially in spring. Genotype-dependent thermal sensitivity was detected for the thermal gradient between the testicular poles, reflecting the seminal quality. There was a positive correlation of the thermal gradient between testicular poles with sperm membrane integrity and negative correlation with total sperm defects. The Texel genotype showed less progressive motility and higher percentage of sperm defects. There was no difference in testosterone concentration between genotypes and in the different seasons (P > 0.05). Thus, the indigenous genotypes showed a greater capability to maintain the scrotum-testicular thermoregulation. Dorper animals resembled the indigenous sheep genotypes, in terms of seminal characteristics, unlike Texel animals, which showed lower adaptability and lower seminal quality.
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http://dx.doi.org/10.1016/j.theriogenology.2018.09.037DOI Listing
January 2019

Thermoregulation of male sheep of indigenous or exotic breeds in a tropical environment.

J Therm Biol 2017 Oct 8;69:302-310. Epub 2017 Sep 8.

Laboratory of Biotechnology and Animal Reproduction, Empresa Brasileira de Pesquisa Agropecuária, Embrapa Pecuária Sudeste, Rod. Washington Luiz, km 234, São Carlos 13560-970, Brazil. Electronic address:

Climate change has intensified the frequency of heat waves in the world, thereby exposing farm animals to stressful conditions. For better productive performance it is important to identify the most resilient genotypes. Thus, our objective was to evaluate the thermoregulatory responses of rams of tropical indigenous (Morada Nova and Santa Inês) and exotic breeds (Dorper and Texel), by monitoring the environmental and physiological indicators related to heat tolerance. The experiment was carried out in a tropical climate region (Cwa), in Brazil, for twelve months, which comprised spring, summer, autumn and winter. Thirty-three rams were divided into groups: Morada Nova (MN; n=8, red-coat), Santa Inês (SI; n=9, black-coat), Dorper (DO; n=8, white-coat) and Texel (TX; n=8, white-coat). The microclimatic variables were monitored, and the THI and BGHI comfort indices were calculated. Coat thickness and body surface temperatures were measured monthly, and serum triiodothyronine-T3 measurements and complete blood tests were performed. The physiological variables were evaluated every fifteen days and skin micro-biopsies were performed in the summer and winter for histological evaluation. During the warmer seasons, the THI and BGHI reached values that indicated thermal discomfort. TX showed higher coat thickness throughout the year, increased physiological variables related to thermolysis, and reduced T3 (P < 0.05). The internal temperature was permanently lower in the MN, SI and DO (P < 0.05). The body surface temperatures were affected by the coat characteristics and wool length. Hematological parameters varied in the seasons with the highest thermal conditions (P < 0.05). The MN showed larger sweat glands, while the area occupied by the sweat glands was higher in the SI. The DO showed higher hair density in the summer and winter (P < 0.05). The results indicated that the MN, SI and DO breeds overcome the thermal challenge more easily throughout the seasons due to specific adaptive morphological and physiological characteristics.
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http://dx.doi.org/10.1016/j.jtherbio.2017.09.002DOI Listing
October 2017

High systemic and testicular thermolytic efficiency during heat tolerance test reflects better semen quality in rams of tropical breeds.

Int J Biometeorol 2017 Oct 11;61(10):1819-1829. Epub 2017 May 11.

Embrapa Southeast Livestock (CPPSE), Brazilian Agricultural Research Corporation, Sao Carlos, SP, Brazil.

This study aimed to assess the capacity of Morada Nova (MN) and Santa Inês (SIN) rams to maintain body and testicular homeothermy under thermal challenge. For 5 days in the summer, 16 males (SIN = 7 and MN = 9) underwent a heat tolerance test, i.e., period 1-animals maintained in the shade (11 to 12 h); period 2-animals exposed to sunlight (12 to 13 h); and period 3-animals returned to the shade (13 to 14 h). The respiratory rate, heart rate, rectal temperature, and infrared surface temperatures (IRT) of the trunk, back, eyeball, and testicles were assessed in each period. The index of capacity of tolerance to insolation (ICTI), which indicates the animals' level of adaptability, was calculated for each animal. Semen quality and testicular parenchyma integrity were assessed before and after the thermal challenge. Statistical analyses were performed at 5% significance. In period 1, the variables had baseline values for both genotypes. In period 2, the variables involved in thermolysis significantly increased (P < 0.05), which matches a thermal discomfort situation. In period 3, the variables returned to baseline values and some values were lower than those in period 1. Semen quality and testicular parenchyma integrity suffered no negative effects with the thermal challenge. IRT ocular and IRT testicular were positively correlated (P < 0.05). It is concluded that MN and SIN rams had efficient thermolytic mechanisms that favor preserving gonadal functionality. The animals were considered resilient to a thermal challenge. In addition, infrared thermography was an efficient tool to verify body and testicular thermoregulation.
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http://dx.doi.org/10.1007/s00484-017-1367-4DOI Listing
October 2017

Piper aduncum against Haemonchus contortus isolates: cross resistance and the research of natural bioactive compounds.

Rev Bras Parasitol Vet 2016 Oct-Dec;25(4):383-393. Epub 2016 Dec 1.

Embrapa Pecuária Sudeste, São Carlos, SP, Brasil.

The anthelminthic activity of the essential oil (EO) of Piper aduncum L. was tested in vitro on eggs and larvae of resistant (Embrapa2010) and susceptible (McMaster) isolates of Haemonchus contortus. The EO was obtained by steam distillation and its components identified by chromatography. EO concentrations of 12.5 to 0.02 mg/mL were used in the egg hatch test (EHT) and concentrations of 3.12 to 0.01 mg/mL in the larval development test (LDT). Inhibition concentrations (IC) were determined by the SAS Probit procedure, and significant differences assessed by ANOVA followed by Tukey's test. In the EHT, the IC50 for the susceptible isolate was 5.72 mg/mL. In the LDT, the IC50 and IC90 were, respectively, 0.10 mg/mL and 0.34 mg/mL for the susceptible isolate, and 0.22 mg/mL and 0.51 mg/mL for the resistant isolate. The EO (dillapiole 76.2%) was highly efficacious on phase L1. Due to the higher ICs obtained for the resistant isolate, it was raised the hypothesis that dillapiole may have a mechanism of action that resembles those of other anthelmintic compounds. We further review and discuss studies, especially those conducted in Brazil, that quantified the major constituents of P. aduncum-derived EO.
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http://dx.doi.org/10.1590/S1984-29612016073DOI Listing
May 2018

Target selected treatment with levamisole to control the development of anthelmintic resistance in a sheep flock.

Parasitol Res 2016 Mar 28;115(3):1131-9. Epub 2015 Nov 28.

Embrapa Pecuária Sudeste (CPPSE), Rod. Washington Luiz, km 234, CP 339, CEP 13560-970, São Carlos, SP, Brazil.

Levamisole phosphate, chosen based on its 100 % efficacy demonstrated by a previous fecal egg count reduction test (FECRT), was used as the exclusive anthelmintic treatment in the Embrapa Southeast Livestock sheep flock from 2009 to 2014 in a target selected treatment scheme. In the present study, the effectiveness of this nematode control scheme was evaluated after 5 years by FECRT, larval development test (LDT), and a molecular test to assess the development of levamisole resistance in Haemonchus contortus. Animals were submitted to treatments with albendazole, levamisole, closantel, ivermectin, moxidectin, and monepantel. Eggs per gram of feces (EPG) counts and fecal cultures were performed, and anthelmintic efficacy was calculated by the RESO 4.0 program. The helminths of the flock (GIN Embrapa2014) were compared to susceptible (McMaster) and resistant (Embrapa2010) H. contortus isolates in the LDT to estimate the LC50 and LC90 of levamisole and in a molecular test to evaluate the 63-bp indel in the acr8 gene associated with levamisole resistance. In the FECRT, parasites were susceptible to monepantel (99.6 %) and closantel (98.3 %), but resistant to moxidectin (93.8 %), levamisole (70.4 %), ivermectin (48.1 %), and albendazole (0 %). In the coproculture on D14, and the control group presented 80 % H. contortus and 20 % Trichostrongylus sp., while in the monepantel group L1 were observed as well as Oesophagostomum sp. L3. LDT and resistance factors provided good separation between susceptible and resistant parasites. The genotypic frequencies of the 63-bp insertion in the acr8 gene in H. contortus were 11.9, 6.7, and 0 % in GIN Embrapa2014, Embrapa2010, and McMaster isolates, respectively. After 5 years of exclusive use, the nematodes developed resistance to levamisole, detected by FECRT and by increase in LC50 and LC90 for levamisole in the LDT. The 63-bp indel was not confirmed as a molecular marker of levamisole resistance in our isolates. The target selected treatment scheme was effective to control helminths in the sheep flock for 5 years, when levamisole's inefficacy was perceived because of no change in the clinical situation of treated animals. Through this scheme, it was possible to promote reversion towards susceptibility or increase of efficacy for other chemical classes. Thus, this is a valid recommendation to control worms and to delay the development of resistance, preserving other anthelmintic classes for future use.
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http://dx.doi.org/10.1007/s00436-015-4844-xDOI Listing
March 2016
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