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The bovine high fecundity allele, Trio, causes overexpression in granulosa cells (GCs) of SMAD6, an inhibitor of BMP15-activated SMAD signalling. Furthermore, the Trio allele results in antral follicles that develop slower, acquire ovulatory capacity at smaller sizes, and have three-fold greater ovulation rate compared to half-sib non-carriers. The present study was designed to determine preantral follicle numbers and size in Trio carrier and non-carrier cattle testing the hypothesis that inhibition of SMAD signalling would alter preantral follicle activation and/or growth. Ovarian tissues from Trio carrier (n = 12) and non-carrier (n = 12) heifers were obtained by laparotomy after follicle wave synchronization. Follicle numbers and dimensions were determined for each stage of development (primordial, transitional, primary, and secondary) from paraffin-embedded sections. There were no differences in the number of primordial, transitional, or secondary follicles or in antral follicle count, circulating AMH, or ovarian volume between carriers and non-carriers. Trio carriers had ~2.5-fold greater (P < 0.01) number of primary follicles than non-carriers, and transitional and primary follicles were larger (~1.2-fold; P < 0.1) in Trio carriers. Oocyte volume of primordial and transitional follicles was not different between genotypes; however, oocytes were larger (P < 0.05) in primary (~1.3-fold) and secondary (~1.8-fold) follicles for Trio carriers. Granulosa cell numbers were not different (P > 0.3) between carriers and non-carriers, irrespective of the stage of development. These results suggest that, after primordial follicle activation, follicles in Trio carrier cattle have slower progression through the primary stage, hence the larger oocyte and greater number of primary follicles. [ABSTRACT FROM AUTHOR]

Cattle are generally considered a monovular species; however, recently, a bovine high fecundity allele, termed the Trio allele, was discovered. Carriers of Trio have an elevated ovulation rate (3-5), while half-sibling noncarriers are monovular. Carriers of the Trio allele have overexpression in granulosa cells of SMAD6, an inhibitor of oocyte-derived regulators of granulosa cell proliferation and differentiation. In experiment 1, follicle size was tracked for each follicle during a follicular wave. Follicle growth rate was greater before vs after follicle deviation in both carriers and noncarriers. Additionally, follicle growth rate was consistently less in carriers vs noncarriers. In experiment 2, we collected granulosa cells from follicles before and after deviation for evaluation of granulosa cell gene expression. Granulosa cell proliferation was less in carriers vs noncarriers and after vs before follicle deviation (decreased expression of cell cycle genes CCNB1 and CCNA2). The decreased granulosa cell proliferation in noncarriers after deviation was associated with increased SMAD6 expression. Similarly, in experiment 3, decreased expression of SMAD6 in granulosa cells of noncarriers cultured in vitro for 60 h was associated with increased expression of cell cycle genes. This suggests that SMAD6 may not just be inhibiting follicle growth rate in carriers of Trio but may also play a role in the decreased follicle growth after deviation in noncarriers. The hypotheses were supported that (1) follicle growth and granulosa cell proliferation decrease after deviation in both carriers and noncarriers and that (2) granulosa cell proliferation is reduced in carriers compared to noncarriers. [ABSTRACT FROM AUTHOR]

The objective of this study was to identify genomic regions associated with postweaning average daily gain (ADG) in swine. Two families were produced using sires obtained from the cross of lines divergently selected for high and low growth rate. Sires were mated to 29 unrelated dams that produced 124 and 115 offspring. Average daily gain was recorded for every individual; mean ADG was .593 [+ or -] .007 kg/d and .619 [+ or -] .009 kg/d in the two families. Selective genotyping was performed as a prescreening procedure to identify genomic regions potentially associated with ADG. A total of 75 genetic markers were used between both families. Markers identified as nominally significant (P < .05) in an individual marker analysis were subsequently typed in all individuals. Markers still nominally significant (P < .05) after analysis with the complete family were then reevaluated together with flanking markers in an interval mapping analysis. A single region on chromosome 3, flanked by markers Sw2429 and Sw251, for the second family had a logarithm of the odds score of 2.9, which is suggestive of linkage with a quantitative trait locus for ADG. Differences were .033 [+ or -] .009 kg/d between individuals inheriting alternative paternal alleles for Sw251, which was the most significant marker. Key Words: Pigs, Genetic Mapping, Genetic Markers

Paratuberculosis (Johne’s disease), an enteric disorder in ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP), causes economic losses in excess of $200 million annually to the US dairy industry. To identify genomic regions underlying susceptibility to MAP infection in Jersey cattle, a case-control genome-wide association study (GWAS) was performed. Blood and fecal samples were collected from ∼5,000 mature cows in 30 commercial Jersey herds from across the US. Discovery data consisted of 450 cases and 439 controls genotyped with the Illumina BovineSNP50 BeadChip. Cases were animals with positive ELISA and fecal culture (FC) results. Controls were animals negative to both ELISA and FC tests that matched cases on birth date and herd. Validation data consisted of 180 animals including 90 cases (positive to FC) and 90 controls (negative to ELISA and FC), selected from discovery herds and genotyped by Illumina BovineLD BeadChip (∼7K SNPs). Two analytical approaches were used: single-marker GWAS using the GRAMMAR-GC method and Bayesian variable selection (Bayes C) using GenSel software. GRAMMAR-GC identified one SNP on BTA7 at 68 megabases (Mb) surpassing a significance threshold of 5×10−5. ARS-BFGL-NGS-11887 on BTA23 (27.7 Mb) accounted for the highest percentage of genetic variance (3.3%) in the Bayes C analysis. SNPs identified in common by GRAMMAR-GC and Bayes C in both discovery and combined data were mapped to BTA23 (27, 29 and 44 Mb), 3 (100, 101, 106 and 107 Mb) and 17 (57 Mb). Correspondence between results of GRAMMAR-GC and Bayes C was high (70–80% of most significant SNPs in common). These SNPs could potentially be associated with causal variants underlying susceptibility to MAP infection in Jersey cattle. Predictive performance of the model developed by Bayes C for prediction of infection status of animals in validation set was low (55% probability of correct ranking of paired case and control samples). [ABSTRACT FROM AUTHOR]

High fecundity genotypes in sheep are a valuable model to study the physiological mechanisms underlying follicle selection and the control of ovulation rate. Similar genotypes in cattle had not been described until the recent identification of a major bovine allele, termed Trio, which had a large effect on ovulation rate. The present study was designed to evaluate ovulation rate, antral follicle count (AFC), circulating ant-müllerian hormone (AMH), and the association among these measures in unstimulated and superstimulated Trio carrier cattle. We hypothesized that AFC and AMH would be variable among individual cows but would be similar between Trio carriers and non-carrier control cows and that there would be no association between these measures of follicle numbers and ovulation rate. In experiment 1, ovulation rate was determined during 4 consecutive estrous cycles in Trio carriers (n = 34) and non-carrier controls (n = 27). Ovulation rate, on average, was greater (P < 0.01) in Trio carriers (3.5 ± 0.2) compared to non-carrier controls (1.1 ± 0.1) with ∼70% of carrier cycles (n = 136) having 3–4 ovulations while only ∼5% had single ovulations. In contrast, non-carrier cycles (n = 108) were mostly single ovulation (89%) with none having more than two ovulations. In experiment 2, AFC, determined at wave emergence, was not different (P = 0.54) between Trio carriers (24.5 ± 1.3; n = 45) and non-carrier controls (23.1 ± 0.9; n = 37), and no correlation was found between AFC and mean ovulation rate in either genotype (r = −0.009 and r = −0.07; P > 0.70, respectively). In Experiment 3, circulating AMH was also not different between genotypes (P = 0.65) while correlations were found between AFC and AMH in Trio carriers (r = 0.43; P = 0.05; n = 27) and non-carrier controls (r = 0.78; P < 0.01; n = 19). In experiment 4, AFC and AMH were determined in Trio-carriers (n = 9) in relation to a synchronized follicular wave which was unstimulated or stimulated with exogenous FSH. Stimulation with FSH increased ovulation rate, compared to unstimulated Trio carriers, however no association was found between AFC or AMH and ovulation rate regardless of whether superstimulation with exogenous FSH was used. In conclusion, the novel high fecundity bovine genotype Trio, results in consistent multiple ovulations despite having similar AFC and AMH. Therefore, our results suggest that differences in antral follicle numbers during the final stages of follicle development are not a key component of the mechanism underlying multiple ovulations in Trio carriers. [ABSTRACT FROM AUTHOR]

Twin birth in dairy cattle is generally unfavorably associated with reproductive performance and calf survival in dairy cows. Genetic selection to reduce twinning rate in dairy cattle may be desirable, provided there are no undesirable correlated responses in other traits. The current study was undertaken to characterize the genomic architecture of twinning rate in the Irish Holstein-Friesian population, and to quantify the genetic relationship of twinning with other reproductive traits and milk yield. Calving records from the years 1996 to 2022 were used together with pedigree information to generate breeding value estimates for twinning rate. Genome-wide association analyses of twinning rate, calving interval, cow survival and age at first calving were conducted using de-regressed breeding values estimates for 2,656 Holstein-Friesian sires. Full genome sequence data imputed from approximately 50,000 single nucleotide polymorphisms were available for all sires. The heritability of twinning rate was 0.0118 ± 0.0010. Twinning rate was very weakly genetically correlated with both milk yield (0.13) and the reproductive traits (-0.26 to 0.14). Genomic analyses detected an association with twinning rate at 31.1 Mb on BTA11 in close proximity to genes for follicle-stimulating hormone receptor and luteinizing hormone-chorionic gonadotropin receptor, supporting previous studies. The most significant SNP in this region was not associated with milk yield, indicating the potential for selection to reduce twinning rate without detrimentally affecting milk yield. Novel SNP associations with age at first calving on BTA27 and from a meta-analysis of calving interval and age at first calving on BTA29 were also identified and are candidates for future validation and study., (© 2025, The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)