The mammary hair of Monodelphis domestica and homology of the mammary pilosebacous unit.

The unitary mammary gland is a synapomorphy of therian mammals and is thought to have evolved from the pilosebaceous organ in the mammalian stem lineage from which the lactogenic patch of monotremes is also derived. One of the key lines of evidence for the homology of the nipple and the lactogenic patch is that marsupials have retained a transient hair associated with developing mammary glands. However, these structures have not been documented since the early 20th-century drawings of Ernst Bresslau. In this study, we examine the developing mammary organs of Monodelphis domestica and document the presence of mammary hairs in 12-week-old females, as well as their absence after 18 weeks of age. Histochemical staining for cystine confirms the structures as keratinized hairs. Milk ducts of both juvenile and adult nipples show a division between KRT18+ luminal epithelium and KRT14+ ACTA2+ myoepithelium. These patterns match those in eutherians and suggest a conserved ductal morphology and mechanism of milk expulsion. Finally, PTHLH, a peptide hormone which promotes homeotic transformation of hairy skin into hairless nipples in the mouse, was detected in the Monodelphis milk duct during the mammary hair stage, suggesting that the mutual exclusivity of "hairless nipple" and "hair" organ identity is derived in eutherian mammals. These results reveal shared characteristics of the M. domestica nipple with both the eutherian nipple and the pilosebaceous organ, consistent with the evolutionary derivation of the mammary gland from an ancestral hair organ via developmental individualization of pilosebaceous and mammary identities.

Genetic parameters for udder conformation traits derived from Cartesian coordinates generated by robotic milking systems in North American Holstein cattle.

Udder conformation is directly related to milk yield, cow health, workability, and welfare. Automatic milking systems (AMS, also known as milking robots) have become popular worldwide, and the number of dairy farms adopting these systems has increased considerably over the past years. In each milking visit, AMS record the location of the 4 teats as Cartesian coordinates in an xyz plan, which can then be used to derive udder conformation traits. Because AMS generate a large amount of data for individual cows per milking visit, they can contribute to an accurate assessment of important traits such as udder conformation without the addition of human classifier errors (in subjective scoring systems). Therefore, the primary objectives of this study were to estimate genomic-based genetic parameters for udder conformation traits derived from AMS records in North American Holstein cattle and to assess the genetic correlation between the derived traits for evaluating the feasibility of multitrait genomic selection for breeding cows that are more suitable for milking in AMS. The Cartesian teat coordinates measured during each milking visit were collected by 36 milking robots in 4,480 Holstein cows from 2017 to 2021, resulting in 5,317,488 records. A total of 4,118 of these Holstein cows were also genotyped for 57,600 SNPs. Five udder conformation traits were derived: udder balance (UB, mm), udder depth (UD, mm), front teat distance (FTD, mm), rear teat distance (RTD, mm), and distance front-rear (DFR, mm). In addition, 2 traits directly related to cow productivity in the system were added to the study: daily milk yield (DY) and milk electroconductivity (EC; as an indicator of mastitis). Variance components and genetic parameters for UB, UD, FTD, RTD, DFR, DY, and EC were estimated based on repeatability animal models. The estimates of heritability (± SE) for UB, UD, FTD, RTD, DFR, DY, and EC were 0.41 ± 0.02, 0.79 ± 0.01, 0.53 ± 0.02, 0.40 ± 0.02, 0.65 ± 0.02, 0.20 ± 0.02, and 0.46 ± 0.02, respectively. The repeatability estimates (± SE) for UB, UD, FTD, RTD, and DFR were 0.82 ± 0.01, 0.93 ± 0.01, 0.87 ± 0.01, 0.83 ± 0.01, and 0.88 ± 0.01, respectively. The strongest genetic correlations were observed between FTD and RTD (0.54 ± 0.03), UD and DFR (-0.47 ± 0.03), DFR and FTD (0.32 ± 0.03), and UD and FTD (-0.31 ± 0.03). These results suggest that udder conformation traits derived from Cartesian coordinates from AMS are moderately to highly heritable. Furthermore, the moderate genetic correlations between these traits should be considered when developing selection subindexes. The most relevant genetic correlations between traits related to cow milk productivity and udder conformation traits were between UD and EC (-0.25 ± 0.03) and between DFR and DY (0.30 ± 0.04), in which both genetic correlations are favorable. These findings will contribute to the design of genomic selection schemes for improving udder conformation in North American Holstein cattle, especially in precision dairy farms.

Ultrasonographic, endoscopic and radiographic examinations of the dromedary mammary glands and teats.

The aim of the present study was to examine the mammary gland of dromedary camels using ultrasonography, endoscopy and radiography. These techniques are easy to perform in the field and feasible to diagnose pathological conditions of the mammary gland. Udders of 49 slaughtered and 26 adult dromedary camels submitted for necropsy were used for the examinations. Additionally, 11 lactating female dromedary camels were selected for the ultrasonographic udder examination. The transition from the milk ducts into the udder cistern, the teat cistern and the teat canals were examined in individual udders. Teat cistern length, teat end width, teat wall thickness, teat cistern width and middle cistern wall thickness were measured using ultrasonography. The measurements resulted in mean values of the teat cistern length of 37.3 mm, the teat end width of 2.0 mm, the teat wall thickness of 4.4 mm, the teat cistern width of 8.2 mm and the cistern wall thickness of 3.5 mm. The teat wall was differentiated into three layers, a hyperechoic outer layer, a hypoechoic middle layer and a hyperechoic inner layer. The mid cistern wall was hyperechoic. Endoscopic examination is an easy to perform and practicable method for examining the inner structures of the teats of dead animals; however, the feasibility has not been shown in lactating animals yet. Ring-like folds were present in the teat cistern, which protruded horizontally into the lumen. It was also possible to visualize the branchlike transition of the teat cistern into the larger milk ducts. Radiographic examination using barium sulfate contrast medium showed that the teat cistern ends in a network of initially wide but branching and narrowing milk ducts. The two teat canals and cisterns are completely independent of each other and there is no communication between the glandular tissue of the two canals and cisterns.

Gross anatomy of vascular supply and drainage of mammary fat pads in mice models.

This work extensively studied the vasculature of mice mammary fat pads (BALB/c and C57BL/6) with special reference to haematogenous drainage routes. Mammary fat pads were five pairs (first cervical, second and third thoracic, fourth abdominal and fifth inguinal), bilaterally symmetrical, extending laterally and continuously with the subcutaneous fascia. The superficial cervical artery and vein primarily accomplished the blood vasculature of the first mammary fat pad, while the lateral thoracic and external thoracic arteries and veins supplied the second and third mammary fat pads. The superficial cervical vein (found parallel to the superficial cervical artery) drained into the external jugular vein. The lateral thoracic artery and external thoracic artery branched almost at the same level as the axillary artery (branch of subclavian artery), the latter being more medial in position. However, in some specimens, the branching of both arteries appeared to be at the same level, and their origins were indistinguishable. The lateral thoracic vein that was parallel to the lateral thoracic artery drained to the axillary vein close to the drainage of the external thoracic vein. The lateral thoracic, superficial caudal epigastric, iliolumbar and external thoracic arteries and veins vascularized the fourth mammary fat pad and displayed anastomosis among themselves. The iliolumbar vein (found parallel to the iliolumbar artery) drained into the inferior vena cava. The superficial caudal epigastric vein (found parallel to the superficial caudal epigastric artery (SCaEA)) drained into the femoral vein. Unlike humans, the internal thoracic artery and vein did not participate in the vasculature of mammary fat pads. The SCaEA and vein supplied blood and drained the fifth mammary fat pad. The anatomical continuity of the fourth and fifth mammary fat pads provided common drainage for both mammary fat pads. The BALB/c and C57BL/6 mice strains studied did not differ in topography and size of mammary fat pads. The vascular supply and drainage of the mammary fat pads also did not differ in the strains studied. Only minor variations could be noted in the small veins draining into the lateral thoracic vein. Lateral tributaries seen in the terminal end of the lateral thoracic vein were absent in the C57BL/6 mice.

An ovine model for investigation of the microenvironment of the male mammary gland.

The specific biology of the male breast remains relatively unexplored in spite of the increasing global prevalence of male breast cancer. Delineation of the microenvironment of the male breast is restricted by the low availability of human samples and a lack of characterisation of appropriate animal models. Unlike the mouse, the male ovine gland persists postnatally. We suggest that the male ovine mammary gland constitutes a promising adjunctive model for the male breast. In this study, we evaluate the male ovine mammary gland microenvironment, comparing intact and neutered males. Assessment of the glandular histo-anatomy highlights the resemblance of the male gland to that of neonatal female sheep and confirms the presence of rudimentary terminal duct lobular units. Irrespective of neutered status, cell proliferation in epithelial and stromal compartments is similarly low in males, and cell proliferation in epithelial cells and in the intralobular stroma is significantly lower than in pubertal female sheep. Between 42% and 72% of the luminal mammary epithelial cells in the male gland express the androgen receptor and expression is significantly reduced by neutering. Luminal epithelial cells within the intact and neutered male gland also express oestrogen receptor alpha, but minimal progesterone receptor expression is observed. The distribution of leukocytes within the ducts and stroma is similar to the mammary gland of female sheep and females of other species. Both macrophages and T lymphocytes are intercalated in the epithelial bilayer and are more abundant in the intralobular stroma than the interlobular stroma, suggesting that they may have a protective immunological function within the vestigial glandular tissue of the male sheep. Mast cells are also observed within the stroma. These cells cluster near the glandular tissue and are frequently located adjacent to blood vessels. The abundance of mast cells is significantly higher in intact males compared to neutered males, suggesting that hormone signalling may impact mast cell recruitment. In this study, we demonstrate the utility of the male ovine mammary gland as a model for furthering our knowledge of postnatal male mammary biology.

The association between teat shape and bimodal milk ejection in Holstein dairy cows.

Our objectives were to investigate the association of teat shape with (1) bimodality, (2) incremental milk flow rates (average flow rates during the first 15 s, 15-30 s, 30-60 s, and 60-120 s of milking), and (3) peak milk flow rate in Holstein dairy cows milked 3 times/d. In this prospective cohort study, we analyzed 220,928 milking observations that were collected from 2,520 cows from a single dairy herd over a period of 31 d. Teat shape was visually assessed and classified into 1 of 4 categories as follows: (1) triangular barrel and pointed teat end (TP), (2) square barrel and round teat end (SR), (3) square barrel, round teat end, and flat in the area of the teat orifice (SRF), and (4) square barrel and flat teat end (SF). Individual cow-level milk flow rates were obtained using electronic on-farm milk meters. We considered bimodality to be present if any of the incremental milk flow rates (flow rates during 15-30 s, 30-60 s, or 60-120 s) were lower than any of the previous rates (flow rates during the first 15 s, 15-30 s, or 30-60 s). The frequency distribution of cows with different teat shapes was as follows: TP, 96 (3.8%); SR, 1,751 (69.5%); SRF, 617 (24.5%); and SF, 56 (2.2%). A generalized linear mixed model revealed differences in the odds of bimodality among cows with different teat shapes. Compared with cows in category SR, the odds (95% CI) of bimodality of cows in other categories were as follows: TP, 0.68 (0.48-0.97); SF, 1.96 (1.21-3.19); and SRF, 1.46 (1.23-1.72). General linear mixed models indicated an association between teat shape and all incremental milk flow rates, with higher milk flow rates being present for cows with teat shapes in the SRF and SF categories. The general linear mixed model for the dependent variable peak milk flow rate indicated an association between teat shape and peak milk flow rate. Least squares means and 95% CI were 5.1 (4.9-5.3) kg/min for TP, 5.8 (5.5-6.1) kg/min for SF, 5.6 (5.5-5.7) for SRF, and 5.3 (5.3-5.4) for SR, respectively. We conclude that in this study cohort, bimodality is more likely to occur in cows with flat teat ends compared with those with a round teat ends. We attribute this relationship to the difference in milking speed across cows with different teat shapes. Teat shape may serve as a useful phenotype to identify cows that are more likely to exhibit bimodality. Because our study population was unique, future studies considering different circumstances such as breed, milking system, and milking routine are needed before results can be extrapolated.

Assessing teat canal morphology in the dry period and during lactation by high-resolution ultrasound.

Our objectives were to quantify the dimensions of a fully 'closed' teat canal in dry cows and to describe recovery of the teat canal between milkings in lactating cows to assess whether and when full closure is attained, since this is an important determinant of udder health. Using an ultrasound scanner, teat canal length and diameter (proximal, midpoint and distal), teat cistern width, teat end width, whole teat width and teat wall thickness in 77 dry and 39 lactating dairy cows were measured. The dry cows represented a cross section of the dry population, with days since dry off ranging from 0 to 69 (median: 27). Data from lactating cows were recorded just before milking, and every 3 h post-milking. To control for location a cross-over (parlour vs. barn) study design was used. In dry cows, teat canal length and diameter did not vary by quarter or days since dry off, but multiparous cows had significantly wider teat canals than primiparous cows. The dry cow measurements can be used as baseline for dimensions for closed teats. In lactating cows, all teat dimensions except teat end width changed significantly during the 12-h milking cycle. Location (parlour vs. barn) did not affect the measurements, except teat end width and teat wall thickness. Teat canal length increased after milking and returned to pre-milking values by 9 h. Proximal and midpoint teat canal diameters decreased slightly just after milking and then progressively increased to above the pre-milking values by 9 h. Distal teat canal diameter increased after milking, partially contracting by 9 h. We found that during the dry period the teat canal is in a steady state, but its diameter is not zero, while during the lactation, the teat canal is in a near constant state of remodelling.

Teat morphology across five buffalo breeds: a multi-country collaborative study.

The buffalo (Bubalus bubalis) is a species of worldwide importance, raised to produce milk, meat, and hides, and often used as a working animal in rural contexts with low access to hi-tech solutions. In the present study, 100 lactating buffaloes (50 primiparous and 50 pluriparous) of five popular breeds were recruited to characterize and compare teat morphology. In particular, the focus was put on the Nili Ravi, Mediterranean, Egyptian, Bulgarian Murrah, and Azeri buffaloes raised in Pakistan, Italy, Egypt, Bulgaria, and Iran, respectively. In all countries, a longitudinal cross-section ultrasound was obtained before the milking to measure teat parameters at individual level: overall, teat canal length (TCL) averaged 24.13 mm, teat diameter (TD) 30.46 mm, cisternal diameter (CD) 17.80 mm, and teat wall (TW) 7.12 mm. The most variable trait across breeds was TCL which was positively correlated with CD and TD and negatively with TW, regardless of the teat position (front/rear or left/right). A strong negative correlation was found between TW and CD (- 0.43). The analysis of variance revealed that the fixed effect of breed significantly affected all the traits except TD. In fact, Bulgarian Murrah, Azeri, and Egyptian buffaloes presented the greatest estimate of TCL, whereas NR the smallest (14.70 mm). The TW was maximum in Nili Ravi, Egyptian, and Mediterranean buffaloes, with estimates equal to 8.19, 7.59, and 8.74 mm, respectively. Nili Ravi also showed the greatest TL (82.39 mm). In terms of CD, the lowest least square mean was that of Mediterranean buffaloes (12.14 mm). Primiparous and pluriparous buffaloes differed in terms of TD, TW, and TL, with older animals presenting the highest least square mean. In terms of position, instead, significant differences were observed for TD, CD, and TL when comparing front and rear teats, as left and right teats did not differ. Teat anatomy includes a set of heritable morphological features and is therefore breed-dependent. Differences presented in this study could be attributed to the divergent breeding objective and selective pressure across the five breeds; e.g., in some cases such as Mediterranean buffalo, selection for decades was oriented to improve milk production and milkability and achieve optimal conformation for mechanical milking. A better understanding of the mammary gland anatomical descriptors can be informative of the history of a breed and could provide useful insights to guide possible selection.

Evaluation of type traits in relation to production, and their importance in early selection for milk performance in dairy buffaloes.

Type traits (TTs) can contribute to breeding animals with good economic traits such as production, longevity, fertility, and profitability. Dairy buffaloes are the second largest source of milk supply in the world, and their TTs should be taken into consideration in future dairy buffalo breeding programmes. However, the relationship between TTs and milk production traits in buffalo remains largely unknown. The study aimed to establish an early selection method for buffaloes with desirable milk performance by TTs. Using 1 908 records from 678 buffaloes, the relationship between TTs and milk production traits was analysed and the optimal growth curves of TTs related to milk production traits were constructed. We examined the correlations between 45 TTs (33 body structural, 12 udder and teat morphological traits) and three milk production traits (milk yield (MY), milk fat percentage (MF), and milk protein percentage (MP)). The results showed that the highest correlation was found between MY and udder circumference (r = 0.438), teat length (r = -0.380) or heart girth (r = -0.341). The teat distance and teat circumference exhibited a significant negative correlation with MF and MP. Rump length was the only trait that had a significant positive correlation with milk production traits, suggesting that milk performance could be comprehensively improved by including rump length in the selection procedure. Notably, we found that high milk production traits was obtained from the buffaloes with short teats (<6 cm), small heart girth (<200 cm), large udder circumference (>104 cm), long rump (>39 cm), and small distance between teats. Moreover, an early selection method for buffaloes with excellent milk performance was developed based on the non-linear models. Brody model exhibited the best fitting effect for heart girth and rump length, while the Logistic model displayed the best fitting effect for teat length. Our findings provide theoretical basis for the early selection of buffaloes with desirable milk performance.

Investigating mammary glands of lactating goats for the presence of tertiary lymphoid organs.

Ectopic tertiary lymphoid organs (TLOs) have been identified in many organs, such as the lungs, nasal cavities, and kidneys of both mice and humans. Although lymphocyte aggregates have been observed in the mammary glands of ruminants, the details remain unclear. In this study, we investigated the mammary glands of lactating goats for the presence of TLOs. The localization of CD20 (B cells), CD3 (T cells), MECA79 (high endothelial venules), CD40 (follicular dendritic cells), BCL6 (germinal center), and IgA was examined by immunohistochemistry. The concentrations of IgG, IgA, lactoferrin, ß-defensin-1, cathelicidin-2, cathelicidin-7, S100A7, and S100A8 in milk were measured by ELISA. The localization and amount of tight junction (TJ) proteins (claudin-3 and claudin-4) were examined using immunofluorescence and western blotting. We found that 19 out of 30 udders contained lymphocyte aggregates, which showed positive reactions against CD20, CD3, CD40, and MECA79. In addition, large-sized aggregations showed separate localization of B cells and T cells and a positive reaction against BCL6, although BCL6 was sparsely localized in the aggregations. These results indicate that mammary glands of lactating goats contain TLOs. The IgG and IgA concentrations in the milk of TLO-positive goats and the number of IgA-positive cells were higher than those in negative goats. Furthermore, claudin-4 was localized in the TJ region and the amount was higher in TLO-positive mammary glands than that in the negative group, indicating the presence of leakages at TJs. In conclusion, a majority of lactating goat udders have TLOs, which contribute to local immunity by producing immunoglobulins.

Udder and teat morphometry in relation to clinical mastitis in dairy cows.

The present study was undertaken to explore the association of occurrence of clinical mastitis with udder and teat morphometry in cattle. The relationship of nine udder and eight teat morphometric traits with the occurrence of clinical mastitis was analysed using a binomial logistic regression model. A significant association of the udder and teat morphometric traits with the occurrence of mastitis was observed both in Karan Fries and Sahiwal cattle. The rear udder height, rear udder width, udder width and fore udder attachment were found to be the important udder morphometric traits associated with the occurrence of mastitis. In both groups, mastitic animals had broader rear udder width, lower rear udder height and loose fore udder attachment with lengthy and thicker teats. The inclusion of udder and teat morphometric traits in the selection and breeding program of Karan Fries and Sahiwal cattle may help in selection of animals for mastitis resistance.

Genome-Wide Association Study Candidate Genes on Mammary System-Related Teat-Shape Conformation Traits in Chinese Holstein Cattle.

In the dairy industry, mammary system traits are economically important for dairy animals, and it is important to explain their fundamental genetic architecture in Holstein cattle. Good and stable mammary system-related teat traits are essential for producer profitability in animal fitness and in the safety of dairy production. In this study, we conducted a genome-wide association study on three traits-anterior teat position (ATP), posterior teat position (PTP), and front teat length (FTL)-in which the FarmCPU method was used for association analyses. Phenotypic data were collected from 1000 Chinese Holstein cattle, and the GeneSeek Genomic Profiler Bovine 100K single-nucleotide polymorphisms (SNP) chip was used for cattle genotyping data. After the quality control process, 984 individual cattle and 84,406 SNPs remained for GWAS work analysis. Nine SNPs were detected significantly associated with mammary-system-related teat traits after a Bonferroni correction (p < 5.92 × 10-7), and genes within a region of 200 kb upstream or downstream of these SNPs were performed bioinformatics analysis. A total of 36 gene ontology (GO) terms and 3 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were significantly enriched (p < 0.05), and these terms and pathways are mainly related to metabolic processes, immune response, and cellular and amino acid catabolic processes. Eleven genes including MMS22L, E2F8, CSRP3, CDH11, PEX26, HAL, TAMM41, HIVEP3, SBF2, MYO16 and STXBP6 were selected as candidate genes that might play roles in the teat traits of cows. These results identify SNPs and candidate genes that give helpful biological information for the genetic architecture of these teat traits, thus contributing to the dairy production, health, and genetic selection of Chinese Holstein cattle.

Determination of factors affecting milk yield, composition and udder morphometry of Hair and cross-bred dairy goats in a semi-intensive system.

In this Research Communication we report milk yield, milk composition and udder morphometry of Hair, Alpine × Hair F1 (AHF1), and Saanen × Hair F1 (SHF1) cross-bred goat genotypes managed in a semi-intensive system. The SHF1 genotype had significantly higher lactation milk yield, fat yield, protein yield, and electrical conductivity than other genotypes, whilst AHF1 was intermediate. The milk fat, protein, lactose, solids-non-fat and total solids contents as well as pH and density of the Hair goat milk were significantly higher than the corresponding values of the cross-bred genotypes. The highest correlation amongst udder characteristics and production was between lactation milk yield and udder volume (P < 0.01; r = from 0.63 to 0.77). The results of this study suggest that crossbreeding can have a positive effect on the milk production characteristics of local goats, thereby reducing the pressure on the ecosystem, and suggest that udder measurements, especially volume, can be a helpful tool for estimating milk yield.

Genome scanning reveals novel candidate genes for vertebral and teat number in the Beijing Black Pig.

Porcine vertebral and teat numbers are variable and important economic traits in pig production. However, the quantitative trait loci (QTL) and candidate genes for both of these traits in the Beijing Black Pig are not yet known. In the present study, number of vertebrae and number of teats were obtained for 891 individuals of the Beijing Black Pig and genotyped using the Illumina Porcine 50 K BeadChip. Genome scanning was performed to detect associated variants and candidate genes for both traits using a genome-wide association study by tassel software. For vertebral number, 15 significant SNPs were located on SSC7. According to linkage disequilibrium analysis on SSC7, a haplotype block of 221 kb from 97.4 to 97.6 Mb was shown to contain a good candidate gene ABCD4. Interestingly, on SSC12, we recorded a novel QTL containing three significant SNPs and 34 annotated genes from 24.0 to 25.7 Mb for vertebral number. Of the 34 genes, nine Hox family genes (HOXB 1-7, 9, and 13) were found to be good candidate genes. Using the 34 genes, a gene ontology analysis was performed to detect enrichment of anterior/posterior pattern specification. For teat number, a novel chromosome-wide significant QTL was identified on SSC10. In this QTL region, one significant SNP was identified. The nearest gene, NTRK2, was regarded as a candidate gene. The present results expanded the QTL for vertebral and teat numbers and provided useful molecular markers for breeding in the Beijing Black Pig population.

A genome-wide association study for the number of teats in European rabbits (Oryctolagus cuniculus) identifies several candidate genes affecting this trait.

In the European rabbit (Oryctolagus cuniculus), a polytocous livestock species, the number of teats indirectly impacts the doe reproduction efficiency and, in turn, the sustainable production of rabbit meat. In this study, we carried out a genome-wide association study (GWAS) for the total number of teats in 247 Italian White does included in the Italian White rabbit breed selection program, by applying a selective genotyping approach. Does had either 8 (n = 121) or 10 teats (n = 126). All rabbits were genotyped with the Affymetrix Axiom OrcunSNP Array. Genomic data from the two extreme groups of rabbits were also analysed with the single-marker fixation index statistic and combined with the GWAS results. The GWAS identified 50 significant SNPs and the fixation index analysis identified a total of 20 SNPs that trespassed the 99.98th percentile threshold, 19 of which confirmed the GWAS results. The most significant SNP (P = 4.31 × 10-11 ) was located on OCU1, close to the NUDT2 gene, a breast carcinoma cells proliferation promoter. Another significant SNP identified as candidate gene NR6A1, which is well known to play an important role in affecting the correlated number of vertebrae in pigs. Other significant markers were close to candidate genes involved in determining body length in mice. Markers associated with increased number of teats could be included in selection programmes to speed up the improvement for this trait in rabbit lines that need to increase maternal performances.

A genome-wide association analysis for body, udder, and leg conformation traits recorded in Murciano-Granadina goats.

Morphological traits are of great importance to dairy goat production given their effect on phenotypes of economic interest. However, their underlying genomic architecture has not yet been extensively characterized. Herein, we aimed to identify genomic regions associated with body, udder, and leg conformation traits recorded in 825 Murciano-Granadina goats. We genotyped this resource population using the GoatSNP50 BeadChip (Illumina Inc., San Diego, CA) and performed genome-wide association analyses using the GEMMA software. We found 2 genome-wide significant associations between markers rs268273468 [Capra hircus (CHI) 16:69617700] and rs268249346 (CHI 28:18321523) and medial suspensory ligament. In contrast, we did not detect any genome-wide significant associations for body and leg traits. Moreover, we found 12, 19, and 7 chromosome-wide significant associations for udder, body, and leg traits, respectively. Comparison of our data with previous studies revealed a low level of positional concordance between regions associated with morphological traits. In addition to technical factors, this lack of concordance could be due to a substantial level of genetic heterogeneity among breeds or to the strong polygenic background of morphological traits, which makes it difficult to detect genetic factors that have small phenotypic effects.

Confirmed effects of candidate variants for milk production, udder health, and udder morphology in dairy cattle.

BACKGROUND: Over the last years, genome-wide association studies (GWAS) based on imputed whole-genome sequences (WGS) have been used to detect quantitative trait loci (QTL) and highlight candidate genes for important traits. However, in general this approach does not allow to validate the effects of candidate mutations or determine if they are truly causative for the trait(s) in question. To address these questions, we applied a two-step, within-breed GWAS approach on 15 traits (5 linked with milk production, 2 with udder health, and 8 with udder morphology) in Montbéliarde (MON), Normande (NOR), and Holstein (HOL) cattle. We detected the most-promising candidate variants (CV) using imputed WGS of 2515 MON, 2203 NOR, and 6321 HOL bulls, and validated their effects in three younger populations of 23,926 MON, 9400 NOR, and 51,977 HOL cows. RESULTS: Bull sequence-based GWAS detected 84 QTL: 13, 10, and 30 for milk production traits; 3, 0, and 2 for somatic cell score (SCS); and 8, 2 and 16 for udder morphology traits, in MON, NOR, and HOL respectively. Five genomic regions with effects on milk production traits were shared among the three breeds whereas six (2 for production and 4 for udder morphology and health traits) had effects in two breeds. In 80 of these QTL, 855 CV were highlighted based on the significance of their effects and functional annotation. The subsequent GWAS on MON, NOR, and HOL cows validated 8, 9, and 23 QTL for production traits; 0, 0, and 1 for SCS; and 4, 1, and 8 for udder morphology traits, respectively. In 47 of the 54 confirmed QTL, the CV identified in bulls had more significant effects than single nucleotide polymorphisms (SNPs) from the standard 50K chip. The best CV for each validated QTL was located in a gene that was functionally related to production (36 QTL) or udder (9 QTL) traits. CONCLUSIONS: Using this two-step GWAS approach, we identified and validated 54 QTL that included CV mostly located within functional candidate genes and explained up to 6.3% (udder traits) and 37% (production traits) of the genetic variance of economically important dairy traits. These CV are now included in the chip used to evaluate French dairy cattle and can be integrated into routine genomic evaluation.

Predicting milk yield in Pelibuey ewes from the udder volume measurement with a simple method.

In this research communication we describe the creation of an equation for the prediction of milk yield (MY) from udder volume (UV). A total of 280 measurements were collected between 5 and 15 d postpartum (pp) from 36 multiparous Pelibuey ewes. Study variables were measured between 2 and 9 weeks pp and MY was measured by manual milking, UV prior to and following milking was measured using the technique of making moulds from aluminium foil. The MY ranged from 0.09 to 0.83 kg/d, meanwhile UV prior and following milking ranged from 155 to 1940 and 90 to 1520 cm3, respectively. Measurements of UV had a moderate to high (P < 0.01; 0.58 ≤ r ≤ 0.78) correlation with MY. The UV prior to milking was the best prediction model for MY, which explained 62% of the variation in MY. This equation presented moderate precision (r2 = 0.61) and high accuracy (bias correction factor = 0.94), confirming a good reproducibility index (concordance correlation coefficient = 0.73). Modelling efficiency (MEF = 0.59) showed moderate concordance between observed and predicted values. In conclusion, MY in lactating Pelibuey ewes could be predicted in a moderate way using the predictor variable UV measured with the technique of moulds made with aluminium foil.

Genome-wide association study for mammary structure in Canadian Angus cows.

Functional and enduring mammary structure is pivotal for producer profitability, and animal health and welfare in beef production. Genetic evaluations for teat and udder score in Canadian Angus cattle have previously been developed. The aim of this study was to identify genomic regions associated with teat and udder structure in Canadian Angus cows thereby enhancing knowledge of the biological architecture of these traits. Thus, we performed a weighted single-step genome wide association study (WssGWAS) to identify candidate genes for teat and udder score in 1,582 Canadian Angus cows typed with the GeneSeek® Genomic Profiler Bovine 130K SNP array. Genomically enhanced estimated breeding values (GEBVs) were converted to SNP marker effects using unequal variances for markers to calculate weights for each SNP over three iterations. At the genome wide level, we detected windows of 20 consecutive SNPs that explained more than 0.5% of the variance observed in these traits. A total of 35 and 28 windows were identified for teat and udder score, respectively, with two SNP windows in common for both traits. Using Ensembl, the SNP windows were used to search for candidate genes and quantitative trait loci (QTL). A total of 94 and 71 characterized genes were identified in the regions for teat and udder score, respectively. Of these, 7 genes were common for both traits. Gene network and enrichment analysis, using Ingenuity Pathway Analysis (IPA), signified key pathways unique to each trait. Genes of interest were associated with immune response and wound healing, adipose tissue development and morphology, and epithelial and vascular development and morphology. Genetic architecture from this GWAS confirms that teat and udder score are distinct, polygenic traits involving varying and complex biological pathways, and that genetic selection for improved teat and udder score is possible.

Genome-wide association studies for the number of teats and teat asymmetry patterns in Large White pigs.

The number of teats is a morphological trait that influences the mothering ability of the sows and thus their reproduction performances. In this study, we carried out GWASs for the total number of teats and other 12 related parameters in 821 Italian Large White heavy pigs. All pigs were genotyped with the Illumina PorcineSNP60 BeadChip array. For four investigated parameters (total number of teats, the number of teats of the left line, the number of teats of the right line and the maximum number of teats comparing the two sides), significant markers were identified on SSC7, in the region of the vertnin (VRTN) gene. Significant markers for the numbers of posterior teats and the absolute difference between anterior and posterior teat numbers were consistently identified on SSC6. The most significant SNP for these parameters was an intron variant in the TOX high mobility group box family member 3 (TOX3) gene. For the other four parameters (absolute difference between the two sides; anterior teats; the ratio between the posterior and the anterior number of teats; and the absence or the presence of extra teats) only suggestively significant markers were identified on several other chromosomes. This study further supported the role of the VRTN gene region in affecting the recorded variability of the number of teats in the Italian Large White pig population and identified a genomic region potentially affecting the biological mechanisms controlling the developmental programme of morphological features in pigs.