Bos Taurus Breeds Research Articles

Assessing introgression of Sahelian zebu genes into native Bos taurus breeds in Burkina Faso

A total of 350 samples were analyzed to estimate zebu gene proportions into two different taurine cattle breeds of Burkina Faso (Lobi and N'Dama) using 38 microsatellites and various statistical methodologies. West African and East African zebu samples were sequentially used as reference parental populations. Furthermore, N'Dama cattle from Congo, the composite South African Bonsmara cattle breed and a pool of European cattle were used successively as second parental populations. Independently of the methodology applied: (a) the use of West African zebu samples gave higher admixture coefficients than the East African zebu; (b) the higher zebu proportions were estimated when the European cattle was used as parental population 2; and (c) the use of the N'Dama population from Congo as parental population 2 gave the more consistent zebu proportion estimates for both the Lobi and the N'Dama breeds. In any case, the zebu admixture proportions estimated were not negligible and were always higher in the N'Dama cattle than in the Lobi cattle of Burkina Faso. This suggested that the introgression of Sahelian zebu genes into the taurine cattle of Southern West Africa can follow a complex pattern that can depend on local agro-ecological features. The current research pointed out that the estimation of admixture coefficients is highly dependent on both the assumptions underlying the methodologies applied and the selection of parental populations. Our analyses suggest that either too high or nil genetic identity between the parental and the expectedly derived populations must be avoided.

FASN gene polymorphism in indigenous cattle breeds of Turkey.

The aim of this study was to determine the variants of the thioesterase (TE) beta-ketoacyl reductase (KR) domains of the Fatty Acid Synthase (FASN) gene, in the East Anatolian Red (EAR) and South Anatolian Red (SAR) cattle breeds. It has been suggested that the FASN gene is effective on fatty acid composition of meat in cattle. In this study, the genotype and allele frequencies of g.17924 A>G, g.18440 G>A and g.16024 G>A, g.16039 T>C in TE and KR domains, respectively, were detected by using polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) method. The g.18663 T>C polymorphism of the TE domain was determined by direct sequencing. The GG genotype of the g.17924 A>G polymorphism, which affects unsaturated fatty acid composition positively, has a high frequency in EAR and SAR breeds. The frequencies of the two haplotypes g.16024 G>A and g.16039 T>C in the KR domain were found to be significantly high in both breeds. These haplotypes also have positive effects on unsaturated fatty acid composition. The AA genotype of the g. 18440 G>A polymorphism, which is suggested to be absent in Bos taurus breeds, was detected in SAR and EAR breeds with frequencies close to those in Bos indicus breeds. In conclusion, we suggest that SAR and EAR cattle breeds have an advantage in terms of genotype and haplotype distribution of the polymorphisms in TE and KR domains of the FASN gene. Additionally g.18440 G>A polymorphism might be a potential marker for breed discrimination.

Expression of immune response genes in peripheral blood of cattle infested with Rhipicephalus microplus.

The bovine tick Rhipicephalus microplus is responsible for severe economic losses in tropical cattle production. Bos indicus breeds are more resistant to tick infestations than are Bos taurus breeds, and the understanding of the physiological mechanisms involved in this difference is important for the development of new methods of parasite control. We evaluated differences in the transcript expression of genes related to the immune response in the peripheral blood of cattle previously characterized as resistant or susceptible to tick infestation. Crossbreed F2 Gir x Holstein animals (resistant, N = 6; susceptible, N = 6) were artificially submitted to tick infestation. Blood samples were collected at 0, 24, and 48 h after tick infestation and evaluated for transcript expression of the CD25, CXCL8, CXCL10, FoxP3, interleukin (IL)-10, and tumor necrosis factor alpha (TNFα) genes. Gene expression of CD25 (6.00, P < 0.01), IL-10 (31.62, P < 0.01), FoxP3 (35.48, P < 0.01), and CXCL10 (3.38, P < 0.05) was altered in the resistant group at 48 h compared with samples collected before infestation. In the susceptible group, CXCL8 (-2.02, P < 0.05) and CXCL10 (2.20, P < 0.05) showed altered expression 24 h after infestation. CXCL8 (-5.78, P < 0.05) also showed altered expression at 48 h after infestation when compared with samples collected before infestation. We detected a correlation between T γδ cell activity and the immunological mechanisms that result in a higher resistance to R. microplus in cattle.

Comparison of tick resistance of crossbred Senepol × Limousin to purebred Limousin cattle

The comparison of resistance to natural tick infestation by Rhipicephalus microplus (Canestrini, 1887) of crossbred Senepol × Limousin and purebred Limousin cattle was investigated. The Senepol breed, originated from St Croix Island in the Caribbean is considered as a Bos taurus breed adapted to tropical conditions. Despite its B. taurus genetic background, it is believed to have a good tick resistance, but this resistance has never been assessed previously. Tick counts under natural infestation were carried out to investigate the difference of susceptibility between crossbred Senepol × Limousin and purebred Limousin cattle. Mixed-effect models were used to assess the effect of the breed on the number of ticks. Results show that Senepol × Limousin are five times less infested by ticks than purebred Limousin. These results underline the opportunity to use Senepol cattle for crossing with susceptible B. taurus breeds in tick infested areas, to combine tick resistance with beef production abilities.

Effect of heat stress on the expression profile of Hsp90 among Sahiwal (Bos indicus) and Frieswal (Bos indicus × Bos taurus) breed of cattle: A comparative study

We evaluated the effect of thermal challenge on the expression profile of heat shock protein 90 (Hsp90) among Sahiwal (Bos indicus) and Frieswal (Bos indicus×Bos taurus) breeds of cattle. The present investigation was focused on the comparative studies on Hsp90 expression among Frieswal and Sahiwal under in vitro and environmental heat stress. Measured immediately after the in vitro heat shock to the peripheral blood mononuclear cells (PBMCs), the relative expression of Hsp90 mRNA was significantly (P<0.05) higher in Sahiwal compared to those in Frieswal. In later intervals of time, the differences in the expression levels between the two breeds become negligible coming down towards the basal level. A similar pattern was observed in the protein concentration showing significantly (P<0.05) higher levels in Sahiwal compared to those in Frieswal. The second sets of experiments were undertaken during summer months (March to May) when temperature peaked from 37 to 45°C. During these months, Frieswal cows consistently recorded higher rectal temperatures than the Sahiwal breed. Further during this peak summer stress, Sahiwal showed significantly higher levels of mRNA transcripts as well as protein concentration compared to the Frieswal breed. Our findings also interestingly showed that, the cell viability of PBMC are significantly higher among the Sahiwal than Frieswal. Taken together, the experiments of both induced in vitro and environmental stress conditions indicate that, Sahiwal may express higher levels of Hsp90 then Frieswal to regulate their body temperature and increase cell survivality under heat stressed conditions.

112 OVARIAN FOLLICLE RESERVE IN NELLORE AND ANGUS HEIFERS WITH LOW AND HIGH FOLLICLE COUNT

Cattle from Bos indicus breeds recruit and develop more follicles per oestrous cycle compared with cattle from Bos taurus breeds. The number of antral follicles in the ovaries is a decisive factor for the success of reproductive technologies such as ovum pick-up and embryo transfer. The reasons why indicine cattle recruit and develop more follicles are not known. Our objectives were to evaluate the ovarian reserve of Nellore and Angus heifers and determine at which stage of follicle development Nellor ovarian reserve differs from Angus ovarian reserve. To determine if animals were in the low or high follicle count group (LFC or HFC), antral follicles (≥3 mm) were scanned with an ultrasound device (US; Mindray Vet DPS 2200, Sao Paulo, Brazil) equipped with a 7.5-MHz probe Day 1 after ovulation (Day 0) for 3 consecutive oestrous cycles. Eighteen Nellore heifers (11 LFC and 7 HFC) and 25 Angus heifers (12 LFC and 13 HFC) were used in the experiment. Oestrous cycles were synchronized with 2 doses of PGF2α ± 11 days apart. Animals were slaughtered ~24 h after ovulation of the third oestrous cycle. Ovulation was determined by oestrous observation, absence of the dominant follicle on the ultrasound, and presence of the corpus luteum after slaughter. One ovary from each animal was used for histology. The ovary was sliced longitudinally in 6 parts, fixed in 10% paraformaldehyde for 24 h, and stored in 70% ethanol until processing. Two longitudinal slices were blocked in paraffin. One section (8 μm thick) was stained after every 50 sections, totaling 10 sections per longitudinal slice of ovarian tissue. Sections were stained using eosin and hematoxylin. Follicles were counted and classified under a stereo microscope with a 40× objective; only follicles with a visible nucleus were counted. Follicles were classified as primordial, primary, and secondary. The area of each section was measured using the hand tool on the ImageJ software. Area measurements were expressed as pixels squared. The density of each follicle classification was calculated as follicle/log10 [pixel2]. Data were analysed using PROC GLM procedure of SAS 9.2 considering the effects of breed and group (LFC or HFC). Angus heifers had more primordial follicles (P &lt; 0.02) when compared with Nellore heifers, but there was no difference within groups. There was no difference in the number of primary follicles within breeds or groups. Secondary follicle numbers tended to be higher (P = 0.09) in Nellore heifers when compared with Angus heifers and was higher within groups (P &lt; 0.02), with HFC Angus and Nellore heifers having more follicles than LFC heifers. It is possible that HFC heifers have a mechanism that is developing more follicles beginning at the secondary stage, especially Nellore heifers. The development of more secondary follicles may contribute to the depletion of primordial follicles observed in Nellore heifers. This research is funded by Sao Paulo Research Foundation (FAPESP) grant #2011/50964-0. Scholarships for Favoureto, Queiroz, Loureiro, Ereno, and Pupulin are also from FAPESP.

Detection of quantitative trait loci in Bos indicus and Bos taurus cattle using genome-wide association studies

BackgroundThe apparent effect of a single nucleotide polymorphism (SNP) on phenotype depends on the linkage disequilibrium (LD) between the SNP and a quantitative trait locus (QTL). However, the phase of LD between a SNP and a QTL may differ between Bos indicus and Bos taurus because they diverged at least one hundred thousand years ago. Here, we test the hypothesis that the apparent effect of a SNP on a quantitative trait depends on whether the SNP allele is inherited from a Bos taurus or Bos indicus ancestor.MethodsPhenotype data on one or more traits and SNP genotype data for 10 181 cattle from Bos taurus, Bos indicus and composite breeds were used. All animals had genotypes for 729 068 SNPs (real or imputed). Chromosome segments were classified as originating from B. indicus or B. taurus on the basis of the haplotype of SNP alleles they contained. Consequently, SNP alleles were classified according to their sub-species origin. Three models were used for the association study: (1) conventional GWAS (genome-wide association study), fitting a single SNP effect regardless of subspecies origin, (2) interaction GWAS, fitting an interaction between SNP and subspecies-origin, and (3) best variable GWAS, fitting the most significant combination of SNP and sub-species origin.ResultsFitting an interaction between SNP and subspecies origin resulted in more significant SNPs (i.e. more power) than a conventional GWAS. Thus, the effect of a SNP depends on the subspecies that the allele originates from. Also, most QTL segregated in only one subspecies, suggesting that many mutations that affect the traits studied occurred after divergence of the subspecies or the mutation became fixed or was lost in one of the subspecies.ConclusionsThe results imply that GWAS and genomic selection could gain power by distinguishing SNP alleles based on their subspecies origin, and that only few QTL segregate in both B. indicus and B. taurus cattle. Thus, the QTL that segregate in current populations likely resulted from mutations that occurred in one of the subspecies and can have both positive and negative effects on the traits. There was no evidence that selection has increased the frequency of alleles that increase body weight.

Prevalence of bovine genital campylobacteriosis and trichomonosis of bulls in northern Nigeria

BackgroundA survey was conducted to determine the prevalence of campylobacteriosis and trichomonosis, and their concurrence with brucellosis, in cattle in three states of northern Nigeria.MethodsA total of 602 preputial samples was collected from bulls in 250 herds and tested using culture and identification. Various indigenous and exotic breeds were studied and four major management systems were encountered. Age of the cattle was estimated using dentition, farm records or cornual rings.ResultsThe estimated true animal-level prevalence of Campylobacter fetus infection was 16.4% (95% CI: 13.0-20.7), of which 18.5% was C. f. fetus and 81.5% was C. f. venerealis. Of the latter, 92% were C. f. venerealis biovar intermedius strains. Animal-level prevalences in Adamawa, Kano and Kaduna states were 31.8%, 11.6% and 8.3% respectively, and were highest in bulls >7 years old (33.4%) and in the Gudali breed (28.8%). Of the 250 herds, 78 (25.5%, 95% CI: 19.4-32.7) had at least one infected bull, and herd prevalence was highest in the pastoral management system (43.5%). After adjustment for confounding using multivariable analysis, the odds of C. fetus infection were highest in Adamawa state (P < 0.01), in the pastoral management system (P < 0.01), and in bulls >7 years old (P = 0.01), and tended to be higher in Bos taurus breeds (P = 0.06). There was a strong positive association between the presence of campylobacteriosis and brucellosis (P < 0.01), both within bulls (OR = 8.3) and within herds (OR = 16.0). Trichomonosis was not detected in any herds.ConclusionBovine genital campylobacteriosis is prevalent particularly in the pastoral management system in northern Nigeria, with C. f. venerealis biovar intermedius as the major aetiology. There was a strong positive correlation between the occurrence of campylobacteriosis and brucellosis. No evidence of trichomonosis was found in herds in this study.

Ancient mtDNA Analysis of Early 16th Century Caribbean Cattle Provides Insight into Founding Populations of New World Creole Cattle Breeds

The Columbian Exchange resulted in a widespread movement of humans, plants and animals between the Old and New Worlds. The late 15th to early 16th century transfer of cattle from the Iberian Peninsula and Canary Islands to the Caribbean laid the foundation for the development of American creole cattle (Bos taurus) breeds. Genetic analyses of modern cattle from the Americas reveal a mixed ancestry of European, African and Indian origins. Recent debate in the genetic literature centers on the ‘African’ haplogroup T1 and its subhaplogroups, alternatively tying their origins to the initial Spanish herds, and/or from subsequent movements of taurine cattle through the African slave trade. We examine this problem through ancient DNA analysis of early 16th century cattle bone from Sevilla la Nueva, the first Spanish colony in Jamaica. In spite of poor DNA preservation, both T3 and T1 haplogroups were identified in the cattle remains, confirming the presence of T1 in the earliest Spanish herds. The absence, however, of “African-derived American” haplotypes (AA/T1c1a1) in the Sevilla la Nueva sample, leaves open the origins of this sub-haplogroup in contemporary Caribbean cattle.

5′Cis regulatory polymorphisms in candidate genes in Bos taurus and Bos indicus

Knowledge about the 5′ regulatory region variation of candidate genes may help to improve breeding and preserve genetic diversity in ruminant species and reveal insights about their evolutionary history. Cis-regulatory regions of candidate genes involved in lipid metabolism and related to energy homeostasis were sequenced in 3 Bos taurus breeds and 1 Bos indicus breed to identify potentially functional polymorphism in non-coding regions. Searching for promoter variability in Fatty Acid Synthase (FASN), Stearoyl-CoADesaturase (SCD), Perilipin (PLIN), Glycerol-3 phosphate acyltransferase mitochondrial (GPAM) and Melanocortin-4 receptor (MC4R), 42 polymorphisms were found. Forty one of them were reported for the first time in B. taurus and B. indicus species. Through in silico analysis we noticed that many of them fall within putative binding sites for transcription factors closely involved in the regulation of the expression of adipogenic genes.A higher nucleotide diversity was found in B. indicus for FASN, SCD, PLIN and MC4R, whereas GPAM was the only more polymorphic promoter in B. taurus. The lower diversity in the B. taurus breeds may reflect their population history with a stronger selection pressure for some economic and productive traits. Alternatively, the ancestors of the indicine breed may have had a high genetic diversity. This research underlines the significance of local breeds for preserving genetic diversity for a sustainable agriculture. The domestication history of ruminant species and the critical role of the analyzed genes in lipid metabolic processes, make these putatively regulatory polymorphisms important targets in breeding and in genetic diversity studies.

Comparison of random regression models to estimate genetic parameters for milk production in Guzerat (Bos indicus) cows

Random regression models have been widely used to estimate genetic parameters that influence milk production in Bos taurus breeds, and more recently in B. indicus breeds. With the aim of finding appropriate random regression model to analyze milk yield, different parametric functions were compared, applied to 20,524 test-day milk yield records of 2816 first-lactation Guzerat (B. indicus) cows in Brazilian herds. The records were analyzed by random regression models whose random effects were additive genetic, permanent environmental and residual, and whose fixed effects were contemporary group, the covariable cow age at calving (linear and quadratic effects), and the herd lactation curve. The additive genetic and permanent environmental effects were modeled by the Wilmink function, a modified Wilmink function (with the second term divided by 100), a function that combined third-order Legendre polynomials with the last term of the Wilmink function, and the Ali and Schaeffer function. The residual variances were modeled by means of 1, 4, 6, or 10 heterogeneous classes, with the exception of the last term of the Wilmink function, for which there were 1, 3, 6, or 10 classes. The models gave similar hereditability estimates, ranging from 0.20 to 0.33. Genetic correlations between adjacent records were high values (0.83-0.99), but they declined when the interval between the test-day records increased, and were negative between the first and last records. The model employing the Ali and Schaeffer function with six residual variance classes was the most suitable for fitting the data.

Imputation of microsatellite alleles from dense SNP genotypes for parentage verification across multiple Bos taurus and Bos indicus breeds

To assist cattle producers transition from microsatellite (MS) to single nucleotide polymorphism (SNP) genotyping for parental verification we previously devised an effective and inexpensive method to impute MS alleles from SNP haplotypes. While the reported method was verified with only a limited data set (N = 479) from Brown Swiss, Guernsey, Holstein, and Jersey cattle, some of the MS-SNP haplotype associations were concordant across these phylogenetically diverse breeds. This implied that some haplotypes predate modern breed formation and remain in strong linkage disequilibrium. To expand the utility of MS allele imputation across breeds, MS and SNP data from more than 8000 animals representing 39 breeds (Bos taurus and B. indicus) were used to predict 9410 SNP haplotypes, incorporating an average of 73 SNPs per haplotype, for which alleles from 12 MS markers could be accurately be imputed. Approximately 25% of the MS-SNP haplotypes were present in multiple breeds (N = 2 to 36 breeds). These shared haplotypes allowed for MS imputation in breeds that were not represented in the reference population with only a small increase in Mendelian inheritance inconsistancies. Our reported reference haplotypes can be used for any cattle breed and the reported methods can be applied to any species to aid the transition from MS to SNP genetic markers. While ~91% of the animals with imputed alleles for 12 MS markers had ≤1 Mendelian inheritance conflicts with their parents' reported MS genotypes, this figure was 96% for our reference animals, indicating potential errors in the reported MS genotypes. The workflow we suggest autocorrects for genotyping errors and rare haplotypes, by MS genotyping animals whose imputed MS alleles fail parentage verification, and then incorporating those animals into the reference dataset.

Genetic Variation and Differentiation of Bison (Bison bison) Subspecies and Cattle (Bos taurus) Breeds and Subspecies

The genetic relationship of American plains bison (Bison bison bison) and wood bison (Bison bison athabascae) was quantified and compared with that among breeds and subspecies of cattle. Plains bison from 9 herds (N = 136), wood bison from 3 herds (N = 65), taurine cattle (Bos taurus taurus) from 14 breeds (N = 244), and indicine cattle (Bos taurus indicus) from 2 breeds (N = 53) were genotyped for 29 polymorphic microsatellite loci. Bayesian cluster analyses indicate 3 groups, 2 of which are plains bison and 1 of which is wood bison with some admixture, and genetic distances do not show plains bison and wood bison as distinct groups. Differentiation of wood bison and plains bison is also significantly less than that of cattle breeds and subspecies. These and other genetic data and historical interbreeding of bison do not support recognition of extant plains bison and wood bison as phylogenetically distinct subspecies.

Indel mutation of the ADD1/SREBP-1c gene in the South Anatolian Red and East Anatolian Red cattle breeds

The present study was designed to determine genotypes of adipocyte determination and differentiation-dependent factor 1 (ADD1)/sterol regulatory element-binding protein-1c (SREBP1c) in South Anatolian Red (SAR) and East Anatolian Red (EAR) cattle. Fifty cattle from the SAR breed and 43 cattle from the EAR breed were used. Intron 7 of the ADD1/SREBP1c gene containing an 84 bp indel mutation was amplified by polymerase chain reaction (PCR). The number of SS genotyped individuals with the 84 bp deletion associated with fatty acid composition and growth traits were very low in both breeds. The frequency of the LL genotype with the 84 bp insertion was significantly higher. The 2 cattle populations were in Hardy-Weinberg equilibrium. The SS genotype was observed in the SAR and EAR breeds. As a result, we can conclude that determination of ADD1/SREBP1c genotype distribution in a great number of cattle breeds of Bos taurus and Bos indicus would allow us to observe more SS genotypes.

Massive screening of copy number population-scale variation in Bos taurus genome

BackgroundCopy number variations (CNVs) represent a significant source of genomic structural variation. Their length ranges from approximately one hundred to millions of base pair. Genome-wide screenings have clarified that CNVs are a ubiquitous phenomenon affecting essentially the whole genome. Although Bos taurus is one of the most important domestic animal species worldwide and one of the most studied ruminant models for metabolism, reproduction, and disease, relatively few studies have investigated CNVs in cattle and little is known about how CNVs contribute to normal phenotypic variation and to disease susceptibility in this species, compared to humans and other model organisms.ResultsHere we characterize and compare CNV profiles in 2654 animals from five dairy and beef Bos taurus breeds, using the Illumina BovineSNP50 genotyping array (54001 SNP probes). In this study we applied the two most commonly used algorithms for CNV discovery (QuantiSNP and PennCNV) and identified 4830 unique candidate CNVs belonging to 326 regions. These regions overlap with 5789 known genes, 76.7% of which are significantly co-localized with segmental duplications (SD).ConclusionsThis large scale screening significantly contributes to the enrichment of the Bos taurus CNV map, demonstrates the ubiquity, great diversity and complexity of this type of genomic variation and sets the basis for testing the influence of CNVs on Bos taurus complex functional and production traits.

Influence of climate factors on spatial distribution of Texas cattle breeds

This paper investigates the spatial distribution of cattle breeders in Texas to quantify how climate factors influence cattle breed selection. A multivariate probit model is employed to examine the county-level binary choices of Bos taurus, Bos indicus and composite breeds derived from cattle breed association membership data. The estimation results suggest that summer heat stress is a significant factor for breed selection: positive for Bos indicus and negative for Bos taurus and composite breeds, with the average marginal effects on breed membership probability being 9.7 %, −26.5 % and −7.9 %, respectively. The intensity of the summer heat impacts can lead to noteworthy changes in spatial distributions of Texas cattle breeds in the event of climate change.

176 EXPRESSION OF INSULIN-LIKE GROWTH FACTOR FAMILY MEMBERS AND GROWTH DIFFERENTIATION FACTOR 9 ON NELORE AND ANGUS HEIFERS WITH A LOW AND HIGH OVARIAN FOLLICLE COUNT

Members of the IGF family are key intra-ovarian regulators of follicle growth, selection, and atresia. Growth differentiation factor 9 (GDF9) induces follicular somatic cells to undergo mitosis and differentiation during follicular development. Cattle from Bos indicus breeds are slower to reach sexual maturity and have longer calving intervals when compared with Bos taurus breeds (Luna-Nevarez et al. 2011). On the other hand, indicine cattle have greater number of ovarian follicles recruited per oestrous cycle when compared with taurine breeds (Alvarez et al. 2000). Our objective was to evaluate the expression of IGF1, IGFR1, IGF2, and GDF9 genes in follicles dissected from Nelore and Angus heifers with high (HFC) and low (LFC) follicle counts. Eighteen Nelore heifers and 22 Angus heifers (≈24 months old) were kept on Brachiaria brizantha grass and fed with a mix of grains with minerals and water ad libitum. Oestrous cycle was synchronized with 2 doses of PGF2α 11 days apart. Heifers were scanned with an ultrasound device (US; Mindray Vet DPS 2200, São Paulo, Brazil) with a 7.5-MHz probe 1 day after ovulation for 3 consecutive oestrous cycles. Animals were slaughtered ≈24 h after ovulation of the third cycle; 3 follicles from 2 to 4 mm in diameter were dissected from the ovary contralateral to the CL. Total RNA was extracted using the RNeasy Microarray Tissue Mini Kit (Qiagen, Valencia, CA, USA). Gene expression was evaluated using oligo-dT reverse transcription, Sybr Green Master Mix and Step One Plus (AB, Foster City, CA, USA) Real-Time PCR Detection System. Samples were analysed in duplicates and CT values were normalized to the housekeeping gene PPIA using the ΔCT method. Results were analysed using the PROC MIXED procedure of SAS with follicle as the repeated measure and cow as the subject. Individual differences were analysed using contrast (SAS 9.2). The effects of group (LFC × HFC), breed, and follicle diameter on mNRA abundance were tested. Follicle LSmean was higher (P &lt; 0.05) in Nelore heifers (32 ± 3.1; LFC = 18; HFC = 52) when compared with Angus heifers (20 ± 2.6; LFC = 10; HFC = 27). Follicle diameter did not differ between breeds or groups. Expression of IGF1 and GDF9 was not different between follicles from Nelore and Angus heifers or between groups. Expression of IGFR1 was higher in follicles from Angus heifers (fold change 1.74; P &lt; 0.04) when compared with follicles derived from Nelore heifers but not different between HFC and LFC groups within each breed. Expression of IGF2 mRNA was also higher (fold change 1.70; P &lt; 0.04) in Angus heifers but not different between HFC and LFC groups within each breed. In conclusion, the higher expression of IGFR1 and IGF2 in Angus early antral follicles might be involved in important reproductive traits commonly observed in Bos taurus breeds. However, expression of IGF1, IGFR1, IGF2, and GDF9 in the follicle are not involved in the mechanisms determining different number of follicle recruited through the oestrous cycle in the same breed. This research and scholarship for Loureiro, Ereno, Favoureto, and Pupulim was from FAPESP.

172 P450 AROMATASE GENE EXPRESSION, ESTRADIOL PRODUCTION, AND DOMINANT FOLLICLE DEVIATION IN BOS TAURUS AND BOS INDICUS DAIRY HEIFERS

It is well documented that the size of the dominant follicle at deviation is smaller in Bos indicus compared with in Bos taurus breeds. The physiological mechanisms underlying this difference, however, are unknown. The aim of the present study was to evaluate the dynamic of oestradiol production during follicle development close to the expected moment of deviation in Bos taurus and Bos indicus dairy heifers. Intrafollicular concentration of oestradiol (E2) and P450 aromatase gene expression in granulosa cells (GC) were evaluated in Gir (n = 10) and Holstein (n = 10) heifers. Follicular waves were synchronized with an intravaginal progesterone device (1 g, Sincrogest, Ourofino Agropecuária, São Paulo, Brazil) and benzoate oestradiol (2 mg im, Sincrodiol, Ourofino Agropecuária). Ultrasonography evaluations (MyLab30 Vet Gold, Esaote, Genova, Italy, with a 7.5-MHz transducer) were performed every 24 h to detect the emergence of the new follicular waves. The largest follicle of each wave was individually aspirated by ovum pickup before, at the expected diameter, or after deviation in both Gir (4.6 ± 0.2, 6.3 ± 0.2, and 8.5 ± 0.6 mm, respectively) and Holstein heifers (6.0 ± 0.5, 8.6 ± 0.4, and 10.2 ± 0.2 mm, respectively), as previously described (Arashiro et al. 2012 Reprod. Fertil. Dev. 24, 175). Follicular fluid (FF) samples were centrifuged and the supernatant stored at –20°C until E2 and progesterone (P4) determination by RIA. The pellet of GCs was washed twice with PBS, kept in RNAlater, and frozen at –20°C until RNA extraction and reverse transcription. Relative transcript quantification was performed by real-time PCR. The β-actin gene was used as control. Samples of FF with E2:P4 ratio &lt;1 or presenting contamination by theca cells (detected by the expression of 17α-hydroxylase) were not used for statistical analyses. Concentration of E2 in FF was evaluated between breeds and among follicle size classes by ANOVA and differences among means compared by Student t-test or Tukey’s test, respectively. Within breeds, relative gene expression was accessed by pair-wise fixed reallocation randomization test (software REST®). Results are shown as mean ± SEM. In both breeds, concentration of E2 in FF progressively increased with follicular diameter (P &lt; 0.05). Intrafollicular concentration of E2 (ng mL–1) was greater (P &lt; 0.05) in Holstein than in Gir before (58.5 ± 11.7 v. 8.8 ± 2.0), at expected (226.0 ± 49.9 v. 78.9 ± 21.0), and after follicle deviation (579.1 ± 45.0 v. 185.0 ± 34.9). Interestingly, however, follicles with similar diameters (~6 or 8 mm) showed similar (P &gt; 0.05) E2 concentrations between Holstein and Gir. Moreover, in both breeds, the relative expression of P450 aromatase gene in GC first increased (3.9 ± 2.4 and 67.5 ± 52.8 for Holstein and Gir, respectively; P &lt; 0.05) at the same stage of follicular development (8 mm). The present results suggest that the smaller size of follicles at deviation in Bos indicus is not related to an earlier increase in intrafollicular E2 production. CNPq, CAPES, and Fapemig (CVZ APQ 02863/09).

Effect of superstimulatory treatments on the expression of genes related to ovulatory capacity, oocyte competence and embryo development in cattle

Multiple ovulation (superovulation) and embryo transfer has been used extensively in cattle. In the past decade, superstimulatory treatment protocols that synchronise follicle growth and ovulation, allowing for improved donor management and fixed-time AI (FTAI), have been developed for zebu (Bos indicus) and European (Bos taurus) breeds of cattle. There is evidence that additional stimulus with LH (through the administration of exogenous LH or equine chorionic gonadotrophin (eCG)) on the last day of the superstimulatory treatment protocol, called the 'P-36 protocol' for FTAI, can increase embryo yield compared with conventional protocols that are based on the detection of oestrus. However, inconsistent results with the use of hormones that stimulate LH receptors (LHR) have prompted further studies on the roles of LH and its receptors in ovulatory capacity (acquisition of LHR in granulosa cells), oocyte competence and embryo quality in superstimulated cattle. Recent experiments have shown that superstimulation with FSH increases mRNA expression of LHR and angiotensin AT(2) receptors in granulosa cells of follicles >8 mm in diameter. In addition, FSH decreases mRNA expression of growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) in oocytes, but increases the expression of both in cumulus cells, without diminishing the capacity of cumulus-oocyte complexes to generate blastocysts. Although these results indicate that superstimulation with FSH is not detrimental to oocyte competence, supplementary studies are warranted to investigate the effects of superstimulation on embryo quality and viability. In addition, experiments comparing the cellular and/or molecular effects of adding eCG to the P-36 treatment protocol are being conducted to elucidate the effects of superstimulatory protocols on the yield of viable embryos.

Partial selective treatment of Rhipicephalus microplus and breed resistance variation in beef cows in Rio Grande do Sul, Brazil

Rhipicephalus microplus infestation causes heavy losses in cattle. The majority of farmers control the cattle tick by using long-acting drugs throughout the year, which evidently increases selection pressure for drug resistance. Partial selective treatment (PST) may be used to directly reduce selection pressure by treating only the portion of the herd that is most infested. The objective of this work was to determine the effect of PST in two herds of beef cows and the effect of breed tolerance. The Santiago (n=306 animals) and the São Francisco de Assis (n=204 animals) herds were composed of up to eight pure breeds of Bos taurus and Bos indicus and their crosses and were evaluated during the first and second (8 months) tick generations. Ticks larger than 4.5mm were counted on one side of the animal, and the animals were treated when numbers exceeded 20 ticks per host. On both farms, the tick-tolerant breeds with a high proportion of B. indicus (Braford, Brangus, and Nellore) consistently carried fewer ticks than Charolais. The economical evaluation showed an average profit margin in the use of PST of 674.25% and 1394.5% on the Santiago and São Francisco de Assis farms, respectively, in comparison to all-herd treatment. These results indicate that PST is a reliable tool for health management and may be used as a standard protocol for tick control with significant economic benefits on farms. In addition, the maintenance of the highest possible tolerant/resilient breeds is also an essential factor that should be considered in today's more sustainable animal production systems.