Genetic improvement of dairy cow reproductive performance

Effect of Age at First Calving on the Reproduction Parameters, Metabolic Profile, and Fatty Acid Composition of Polish Holstein Friesian (PHF) and Crossbreds PHF × Swedish Red (SRB) Cattle

BACKGROUND

The high dairy production of Polish Holstein Friesian (PHF) cows determines high energy requirements in the early stages of lactation. Unfortunately, it is very often difficult to meet this demand through feedstuffs; therefore, homeostasis may be disturbed and metabolic diseases may occur, causing a majority of cows' health problems. Breeders are, therefore, looking for alternatives to the PHF breed using crossbreeding.

METHODS

This experiment involved 30 PHF cows and 30 PHF × Swedish Red (SRB) crossbred hybrid cows, divided into two age groups, <2 years and >2 years, at first calving. Milk and blood samples were collected at 35 ± 5 days postpartum for analysis. Data on reproductive performance were also analyzed.

RESULTS

This study revealed lower milk production for the crossbreds hybrid (27.44 kg compared to 32.08 kg), with a higher basic composition content than PHF cows (fat: 3.97% compared to 3.83%, protein: 3.53% compared to 3.27%). The heifers of the crossbreds hybrid reached sexual maturity earlier but did not affect the lower age at first calving. Dividing the cows into age categories provided a more detailed perspective of the impact of genotypic differences on reproductive and metabolic profiles in PHF and PHF × SRB cattle. The findings highlight the importance of considering age-specific effects when assessing the performance and health of dairy cattle with diverse genotypes.

CONCLUSIONS

The choice between PHF and PHF × SRB should depend on the specific goals and priorities of the cattle farming operation. Factors such as overall milk yield requirements, market demands, reproductive management strategies, and health considerations should be carefully evaluated to determine the most suitable breed for a given farming context.

Exploration of the Polymorphism Distribution of Bovine HMGA2 Gene in Worldwide Breeds and Its Associations with Ovarian Traits

The high-mobility group AT-hook 2(HMGA2) gene has been widely studied in the context of cancer and animal growth. However, recently, several studies have uncovered its critical role in cell proliferation. A genome-wide association study (GWAS) further suggests that the HMGA2 gene is a candidate gene in fertility, indicating its connection not only to growth traits but also to reproduction, specifically ovarian traits. Thus, this study aimed to analyze the distribution of the HMGA2 gene in 54 bovine breeds worldwide, identify important short fragment variants (indels), and investigate the relationship between HMGA2 and ovarian development. The dataset included genotypic information from a bovine population of 634 individuals (n = 634). After genotyping and analyzing four selected loci, we found that one out of four loci, rs133750033 (P4-D22-bp), was polymorphic. Our results also reveal that this indel of HMGA2 is significantly associated with certain ovarian traits (p < 0.05). Specifically, it has connection with ovarian length (p = 0.004) and ovarian height (p = 0.026) during diestrus. Additionally, we discovered a higher expression of the HMGA2 gene in Asian cattle breeds. In summary, this study suggests that HMGA2 has the potential to serve as an animal fertility testing marker gene. Moreover, these findings contribute to a more promising outlook for the bovine industry.

Quantitative trait loci exploration and characterization of gestation length in Holstein cattle

Gestation length (GL) is a moderately heritable trait in cattle with economic and management implications. This study aimed to characterize the gestation length of an Argentinian Holstein cattle population, understand contributing factors, and explore the GL effect on production performance. Further objectives were to estimate direct and maternal heritabilities for this trait and to identify genomic regions affecting it. Data consisted of GL records from 45,738 births corresponding to 17,004 Holstein cows and heifers. The effects of age and calving season over GL were analyzed using a Student's t-test for homoscedastic samples. The effects of the GL category (GL shorter than 1.5 SD, within ±1.5 SD, and longer than 1.5 SD from the mean) on production performance were studied by analysis of variance. A single-step genome-wide association study was performed using the BLUPF90 suite of programs with genotypes from 654 Holstein animals on 40,339 SNP. The results showed that the younger the age at calving, the shorter the GL. Moreover, gestations ending in warmer seasons were, in general, statistically shorter than those ending in colder seasons for both heifers and cows. Regarding the effect of GL on production performance, cows with gestation periods within ±1.5 SD from the population mean exhibited the highest 305-day cumulative milk, fat, and protein productions. Direct and maternal heritabilities for GL were 0.42 and 0.03, respectively. We detected a SNP suggestively associated with direct gestation length at 57.7 Mb on Bos taurus autosome 18, a locus included in a region described in the literature as associated with the trait. The information obtained on the environmental and genetic factors affecting GL in Argentinian Holstein cows contributes to characterizing the population in pursuit of improving the performance of national dairy cattle breeding systems.

Metabolomic evolution of the postpartum dairy cow uterus

High rates of early pregnancy loss are a critical issue in dairy herds, particularly in seasonal, grazing systems. Components of the uterine luminal fluid (ULF), on which the early embryo depends for sustenance and growth, partly determine early pregnancy losses. Here, changes in ULF from early to mid-postpartum in crossbred dairy cows were explored, linking them with divergent embryo development. For this, the uteri of 87 cows at Day 7 of pregnancy at first and third estrus postpartum were flushed to collect ULF. Eighteen metabolites (chiefly organic acids and sugars) significantly varied in abundance across postpartum, indicating a molecular signature of physiological recovery consistent of the upregulation of pyrimidine metabolism and glycerophospholipid metabolism, and downregulation of pentose phosphate and taurine metabolism pathways. Joint pathway analysis of metabolomics data and a previously generated proteomics data set on the same ULF samples suggests key links between postpartum recovery and subsequent successful embryo development. These include upregulation of VEGFA and downregulation of metabolism, NRF2, T-cell receptor, which appear to improve the ULF's capacity of sustaining normal embryo development, and a putative osmo-protectant role of beta-alanine. These relationships should be further investigated to develop tools to detect and reduce early pregnancy loss in dairy cows.

SWATH-MS Analysis of Blood Plasma and Circulating Small Extracellular Vesicles Enables Detection of Putative Protein Biomarkers of Fertility in Young and Aged Dairy Cows

The development of biomarkers of fertility could provide benefits for the genetic improvement of dairy cows. Circulating small extracellular vesicles (sEVs) show promise as diagnostic or prognostic markers since their cargo reflects the metabolic state of the cell of origin; thus, they mirror the physiological status of the host. Here, we employed data-independent acquisition mass spectrometry to survey the plasma and plasma sEV proteomes of two different cohorts of Young (Peripubertal; n = 30) and Aged (Primiparous; n = 20) dairy cows (Bos taurus) of high- and low-genetic merit of fertility and known pregnancy outcomes (ProteomeXchange data set identifier PXD042891). We established predictive models of fertility status with an area under the curve of 0.97 (sEV; p value = 3.302e-07) and 0.95 (plasma; p value = 6.405e-08). Biomarker candidates unique to high-fertility Young cattle had a sensitivity of 0.77 and specificity of 0.67 (*p = 0.0287). Low-fertility biomarker candidates uniquely identified in sEVs from Young and Aged cattle had a sensitivity and specificity of 0.69 and 1.0, respectively (***p = 0.0005). Our bioinformatics pipeline enabled quantification of plasma and circulating sEV proteins associated with fertility phenotype. Further investigations are warranted to validate this research in a larger population, which may lead to improved classification of fertility status in cattle.

The anogenital ratio as an indicator of reproductive performance in dairy heifers

The anogenital distance (AGD) is considered a marker for prenatal androgen exposure and fertility in multiple species including humans. In dairy cattle, it is described as the length between the center of the anus and the clitoral base (AGDc). However, in other species, the distance from the center of the anus to the dorsal commissure of the vulva (AGDv) is also considered to be a predictor for fertility traits, as well as the anogenital ratio (AGR, defined as [AGDv/AGDc]*100). The primary aim of the present study was to assess whether AGDv and AGR can be used as an indicator for reproductive performance in dairy heifers. Additionally, the relation between AGDv and AGDc and the correlation with other body measurements were explored. Data of 656 Holstein Friesian heifers at an age of 13.5 ± 1.08 months were analyzed. Respective means of 62.9 ± 8.20 mm (AGDv) and 107.6 ± 9.27 mm (AGDc) were recorded. The mean AGR ratio was calculated as 58.6 ± 6.75%, varying from 37.3 to 79.6%. The age of the heifers was not associated with any of the AGD measurements nor the ratio. Except for a very low correlation between heart girth and AGDc (r = 0.09, P < 0.05), both AGDs were largely uncorrelated with other body measurements. Linear regression models revealed that AGDc was not associated with any of the recorded fertility parameters. However, results revealed a negative association between AGDv and AGR and reproductive performance: heifers with a short AGDv and small AGR were younger at first AI (P ≤ 0.003) and at conception (P = 0.004). Based on ROC curve analyses, AGDv was the best indicator for pregnancy to first AI, with a threshold estimated at 65.3 mm. The pregnancy rate at first AI was 72.4% in heifers with a short AGDv (<65.3 mm, n = 413) compared to 61.7% in heifers with a long AGDv (≥65.3 mm, n = 243). Hence, short-AGDv heifers had 63% higher odds to conceive at first AI compared to their long-AGDv counterparts (P = 0.004). Additionally, an AGR threshold of 59,6% was determined: heifers with a small AGR (<59.6%) had 44% higher odds to be pregnant at first AI compared to heifers with an AGR ≥59.6%. Results of the present study suggest to consider AGDv and AGR as potential indicators for reproductive performance in dairy heifers. The latter implies that it is relevant to measure both AGDc and AGDv in future studies. The absence of correlation between body- and AGD-measurements furthermore suggests that AGD sizes are rather pre-than postnatally determined.

C-X-C motif chemokine ligand 12 improves the developmental potential of bovine oocytes by activating SH2 domain-containing tyrosine phosphatase 2 during maturation†

In vitro maturation of mammalian oocytes is an important means in assisted reproductive technology. Most bovine immature oocytes complete nuclear maturation, but less than half develop to the blastocyst stage after fertilization. Thus, inefficient in vitro production is mainly caused by a suboptimal in vitro culture process, in which oocyte quality appears to be the limiting factor. In our study, a potential maternal regulator, C-X-C motif chemokine ligand 12, was identified by analyzing transcriptome data. C-X-C motif chemokine ligand 12 supplementation promoted the developmental potential of oocytes by improving protein synthesis and reorganizing cortical granules and mitochondria during in vitro maturation, which eventually increased blastocyst formation efficiency and cell number after parthenogenesis, fertilization, and cloning. All these promoting effects by C-X-C motif chemokine ligand 12 were achieved by activating SH2 domain-containing tyrosine phosphatase 2, thereby promoting the mitogen-activated protein kinase signaling pathway. These findings provide an in vitro maturation system that closely resembles the maternal environment to provide high-quality oocytes for in vitro production.

The interaction between the environment and embryo development in assisted reproduction

It can be assumed that the natural processes of selection and developmental condition in the animal provide the best prerequisites for embryogenesis resulting in pregnancy and subsequent birth of a healthy neonate. In contrast, circumventing the natural selection mechanisms and all developmental conditions in a healthy animal harbors the risk of counteracting, preventing or reducing the formation of embryos or substantially restricting their genesis. Considering these facts, it seems to be obvious that assisted reproductive techniques focusing on early embryonic stages serve an expanded and unselected germ cell pool of oocytes and sperm cells, and include the culture of embryos outside their natural habitat during and after fertilization for manipulation and diagnostic purposes, and for storage. A significant influence on the early embryonic development is seen in the extracorporeal culture of bovine embryos (in vitro) or stress on the animal organism (in vivo). The in vitro production per se and metabolic as well as endocrine changes in the natural environment of embryos represent adequate models and serve for a better understanding. The purpose of this review is to give a brief presentation of recent techniques aimed at focusing more on the complex processes in the Fallopian tube to contrast in vivo and in vitro prerequisites and abnormalities in early embryonic development and serve to identify potential new ways to make the use of ARTs more feasible.

Exploring molecular dynamic indicators associated with reproductive performance of Bos indicus cattle in blood plasma samples through data-independent acquisition mass spectrometry

Improving reproductive performance of cattle is of paramount importance for sustainable dairy farming. Poor reproduction performance (RP) hinders the genetic improvement of important Bos indicus cattle breeds. It is well known that incorporation of molecular information along with conventional breeding method is far better than use of conventional method alone for the genetic improvement of reproductive performance traits in cattle. Therefore, the present study sought to investigate the plasma proteome of the Deoni cows in cyclical (n = 6) and pregnant (n = 6) reproductive phases with varying reproductive performance (high and low). High-throughput data independent acquisition (DIA) based proteomics was performed to understand corresponding proteome. We identified a total of 430 plasma proteins. Among cyclic cows, twenty proteins were differentially regulated in low RP as compared to high RP. BARD1 and AFP proteins were observed upregulated in cyclical cows whose upregulation reported to affect reproductive performance in cattle. Among the pregnant cows, thirty-five proteins were differentially regulated, including the downregulation of FGL2 and ZNFX1 that modulates the maternal immune response mechanism which is required for successful implantation of the embryo. Also, proteins such as AHSG, CLU and SERPINA6 were upregulated in the pregnant cows whose upregulation reported to reduced reproductive performance. The results of this study will be helpful in establishing a framework for future research on the aspect of improving reproductive performance in Bos indicus cattle breeds. SIGNIFICANCE: The Indian subcontinent is the center of domestication for Bos indicus cattle breeds and they are known for their disease resistance, heat tolerance, ability to survive in low input regime and harsh climatic conditions. In recent times, population of many important Bos indicus breeds including Deoni cattle is declining due to various factors, especially due to reproductive performance. Traditional breeding methods are not sufficient enough to understand and improve the reproductive performance traits in important Bos indicus cattle breeds. Proteomics approach is a promising technology to understand the complex biological factors which leads to poor reproductive performance in cattle. The present study utilized DIA based LC- MS/MS analysis to identify the plasma proteins associated with reproductive performance in cyclical and pregnant cows. This study if improved further, can be used to develop potential protein markers associated with reproductive performance which is useful for the selection and genetic improvement of important Bos indicus breeds.

Keeping profitable cows in the herd: A lifetime cost-benefit assessment to support culling decisions

Increasing the productive lifespan of dairy cows is important to achieve a sustainable dairy industry, but making strategic culling decisions based on cow profitability is challenging for farmers. The objective of this study was to carry out a lifetime cost-benefit analysis based on production and health records and to explore different culling decisions among farmers. The cost-benefit analysis was conducted for 22 747 dairy cows across 114 herds in Quebec, Canada for which feed costs and the occurrence of diseases were reported. Costs and revenues related to productive lifespan were compared among cohorts of cows that left their respective herd at the end of their last completed lactation or stayed for a complete additional lactation. Hierarchical clustering analysis was carried out based on costs and revenues to explore different culling decisions among farmers. Our results showed that the knowledge of lifetime cumulative costs and revenues was of great importance to identify low-profitable cows at an earlier lactation, while only focusing on current lactation costs and revenues can lead to an erroneous assessment of profitability. While culling decisions were mostly based on current lactation costs and revenues and disregarded the occurrence of costly events on previous lactations, there was variation among farmers as we identified three different culling decision clusters. Monitoring cumulative costs and revenues would help farmers to identify low-profitable cows at an earlier lactation and make the decision to increase herd productive lifespan and farm profitability by keeping the most profitable cows.

Oocyte aneuploidy rates in river and swamp buffalo types (Bubalus bubalis) determined by Multi-color Fluorescence In Situ Hybridization (M-FISH)

Aneuploidy is one of the main causes of fetal and embryonic mortality in mammals. Nonetheless, its incidence in domestic ruminants has been investigated little. Indeed, no incidence data have ever been reported for water buffalo. To establish the incidence of aneuploidy in this species, we analysed in vitro matured metaphase II (MII) oocytes with corresponding first polar bodies (I PB) of the river (2n = 50) and swamp (2n = 48) buffaloes. For the first time, six river type probes (corresponding to chromosomes 1–5 and heterosome X), were tested on swamp buffalo metaphases using Multicolor-Fluorescent In Situ Hybridization (M-FISH) before their use on oocytes MII metaphases. Of the 120 total Cumulus Oocyte Complexes (COCs, 60 for each buffalo type) subjected to in vitro maturation, 104 reached the MII stage and were analysed by M-FISH. Haploid chromosome arrangement and visible I PB were observed in 89 of the oocytes (45 in river and 44 in swamp type). In the river type, the analysis revealed one oocyte was disomic for the chromosome X (2.22%). In the swamp type, one oocyte was found to be nullisomic for chromosome X (2.27%); another was found to be nullisomic for chromosome 5 (2.27%). We also observed one oocyte affected by a premature separation of sister chromatids (PSSC) on the chromosome X (2.27%). In both buffalo types, no abnormalities were detected in other investigated chromosomes. Based on merged data, the overall aneuploidy rate for the species was 3.37%. Oocytes with unreduced chromosomes averaged 1.92% across the two types, with 1.96% in river and 1.88% in swamp. The interspecies comparison between these data and cattle and pig published data revealed substantial difference in both total aneuploidy and diploidy rates. Reducing the negative impact of the meiotic segregation errors on the fertility is key to more sustainable breeding, an efficient embryo transfer industry and ex-situ bio-conservation. In this respect, additional M-FISH studies are needed on oocytes of domestic species using larger sets of probes and/or applying next generation sequencing technologies.

Impact of Veterinary Herd Health Management on German Dairy Farms: Effect of Participation on Farm Performance

German dairy farming has intensified markedly in recent years, and the demand for Veterinary Herd Health Management (VHHM) is rising. To protect farms from epidemics, ensure food safety, and prevent developing of antibiotic resistance, VHHM has been anchored in EU law since April 2021. Via an online survey, distributed by different farmers' organizations, dairy farmers were asked about the cooperation with their veterinarian. The aim was to evaluate farm performance as a function of participation in VHHM. From 216 analyzed questionnaires, 106 respondents participated in VHHM. Results showed that farmers who make use of VHHM and consult their veterinarian in decision-making frequently have the highest 305-day milk yield (305dMY), the lowest bulk tank somatic cell counts, and the lowest age at first calving (AFC). However, these farmers tended to have higher replacement rates and a higher mortality of cows in the period up to 60 days in milk (MORT60DIM). Furthermore, respondents who defined VHHM as “evaluation of herd data, strategic planning” had the highest 305dMY compared with those who defined VHHM through one of the different options given (“pregnancy checks and support in reproduction”/“problem solving”). In the multifactorial regression model, VHHM participating farms had a 660-kg higher 305dMY and 1 month less in AFC, compared with farms not participating in VHHM. However, within the VHHM participants, no association between VHHM practices and performance parameters was found. Further research is needed, to find out if tailored advice of the VHHM approach may show effect herein.

Indel mutations within the bovine HSD17B3 gene are significantly associated with ovary morphological traits and mature follicle number

Given the intensive selection for increased milk production, it is imperative that the problem of declining fertility in dairy cows be reversed. In female mammals their reproductive traits and functioning is controlled by a finely tuned process balancing estrogens and androgens, in which androgens (e.g., testosterone) as a precursor substance can participate in estrogen synthesis by activating 17β-hydroxysteroid dehydrogenase (17betaHSD). Being a key catalyst for testosterone synthesis, we hypothesized HSD17B3 gene is involved in the ovary's development and thereby capable of influencing cows' fecundity. Herein, to investigate the relationship between polymorphisms of the HSD17B3 gene and cow fertility, we characterized three insertion/deletion (indels) polymorphisms of this gene in 1110 healthy bovine ovaries. Their respective minimum allelic frequency (MAF) ranged from 0.180 to 0.482. For the ovary morphological traits, correlations revealed that both P1-D_15-bp and P4-D_19-bp demonstrated significant associations with ovarian height (P = 0.007 and 0.004, respectively), while P5-I_5-bp was found to be significantly associated with the ovarian weight (P = 0.024). For ovarian volume, a significant correlation was uncovered between it and both polymorphisms of P4-D_19-bp (P = 0.036) and P5-I_5-bp (P = 0.045). Cows with either the DD genotype of P4-D_19-bp or P5-I_5-bp tended to have greater ovarian volume, a result consistent with their relationship to ovarian weight (P5-I_5-bp) or height (P4-D_19-bp). For the mature follicle traits, polymorphisms of P4-D_19-bp were found significantly associated with the number of mature follicles (P = 0.045). Furthermore, expression levels of HSD17B3 differed significantly between the maximal and minimum groups of ovarian weight or volume, and the transcription factors GATA-1 and USF were predicted to bind P1-D_15-bp and P4-D_19-bp, respectively. This suggested the detected intron mutations could affect HSD17B3's transcription by regulating the binding of transcription factors, thereby affecting ovarian weight and other reproductive traits. As a potential effective molecular marker loci significantly related to traits of ovary and follicle, these three indels could be used in practical molecular marker-assisted selection (MAS) breeding programs, to optimize female fertility and enhance economic efficiency in the dairy cow industry.

Genetic consequences of terminal crossbreeding, genomic test, sexed semen, and beef semen in dairy herds

The development of breeding tools, such as genomic selection and sexed semen, has progressed rapidly in dairy cattle breeding during the past decades. In combination with beef semen, these tools are adopted increasingly at herd level. Dairy crossbreeding is emerging, but the economic and genetic consequences of combining it with the other breeding tools are relatively unknown. We investigated 5 different sexed semen schemes where 0, 50, and 90% of the heifers; 50% of the heifers + 25% of the first-parity cows; and 90% of the heifers + 45% of the first-parity cows were bred to sexed semen. The 5 schemes were combined in scenarios managing pure-breeding or terminal crossbreeding, including genomic testing of all newborn heifers or no testing, and keeping Swedish Red or Swedish Holstein as an initial breed. Thus, 40 scenarios were simulated, combining 2 stochastic simulation models: SimHerd Crossbred (operational returns) and ADAM (genetic returns). The sum of operational and genetic returns equaled the total economic return. Beef semen was used in all scenarios to limit the surplus of replacement heifers. Terminal crossbreeding implied having a nucleus of purebred females, where some were inseminated with semen of the opposite breed. The F₁ crossbred females were inseminated with beef semen. The reproductive performance played a role in improving the benefit of any of the tools. The most considerable total economic returns were achieved when all 4 breeding tools were combined. For Swedish Holstein, the highest total economic return compared with a pure-breeding scenario, without sexed semen and genomic test, was achieved when 90% sexed semen was used in heifers and 45% sexed semen was used for first-parity cows combined with genomic test and crossbreeding (+€58, 33% crossbreds in the herd). The highest total economic return for Swedish Red compared with a pure-breeding scenario, without sexed semen and genomic test, was achieved when 90% sexed semen was used in heifers combined with genomic test and crossbreeding (+€94, 46% crossbreds in the herd). Terminal crossbreeding resulted in lower genetic returns across the herd compared with the corresponding pure-breeding scenarios but was compensated by a higher operational return.

The Intergenerational Impacts of Paternal Diet on DNA Methylation and Offspring Phenotypes in Sheep

Knowledge of non-genomic inheritance of traits is currently limited. Although it is well established that maternal diet influences offspring inheritance of traits through DNA methylation, studies on the impact of prepubertal paternal diet on DNA methylation are rare. This study aimed to evaluate the impact of prepubertal diet in Polypay rams on complex traits, DNA methylation, and transmission of traits to offspring. A total of 10 littermate pairs of F0 rams were divided so that one ram was fed a control diet, and the other was fed the control diet with supplemental methionine. Diet was associated with earlier age at puberty in treatment vs. control F0 rams. F0 treatment rams tended to show decreased pubertal weight compared to control rams; however, no differences were detected in overall growth. A total of ten F0 rams were bred, and the entire F1 generation was fed a control diet. Diet of F0 rams had a significant association with scrotal circumference (SC) and weight at puberty of F1 offspring. The paternal diet was not significantly associated with F1 ram growth or age at puberty. The DNA methylation of F0 ram sperm was assessed, and genes related to both sexual development (e.g., DAZAP1, CHD7, TAB1, MTMR2, CELSR1, MGAT1) and body weight (e.g., DUOX2, DUOXA2) were prevalent in the data. These results provide novel information about the mechanisms through which the prepubertal paternal diet may alter body weight at puberty and sexual development.

Polymorphic variants of bovine ADCY5 gene identified in GWAS analysis were significantly associated with ovarian morphological related traits

The reproductive performance (e.g. fertility) of dairy cows, which declined over past few decades due to the intense and intensive selection, needs to be improved. Previous genome-wide association study (GWAS) of female Holstein screened the Adenylate cyclase 5 (ADCY5) as the candidate gene for cow fertility. As a member of the adenylyl cyclases family, adenylate cyclase 5 (ADCY5) is famous for regulating extrapyramidal motor system related various neuropsychiatric diseases, and its genetic variant is reported to associate with lower birth and placenta weight which leads to asymmetric fetal growth restriction. It was hypothesized that ADCY5 may affect the fertility of cows by regulating the processes of ovarian development. Herein, genomic DNA from 768 ovaries samples of healthy unrelated Holstein cow were used to screen potential insertion/deletion (indel) mutations using eight pairs of primers, and we found three novel polymorphic indel variants, namely, rs385624978 (P3-D_11-bp), rs433028962 (P5-I_19-bp) and rs382393457 (P8-D_19-bp). The minor allelic frequencies (MAF) of P3-D_11-bp, P5-I_19-bp and P8-D_19-bp loci were 0.188, 0.365 and 0.06, respectively, and there were 7 different haplotypes. Additionally, linkage disequilibrium analysis demonstrated no linkage among them. Importantly, P3-D_11-bp locus was significantly related to both ovarian width (P = 1.0E-6) and corpus luteum diameter (P = 0.015); P5-I_19-bp locus had a significant relation with corpus albicans diameter (P = 0.030) and ovaries with mutational homozygous genotype produced a superior corpus albicans diameter than those with other genotypes. Briefly, three novel indel mutations of bovine ADCY5 gene were identified and two of them were uncovered to be significantly correlated with ovarian phenotypic traits or corpus luteum or albicans traits. These findings contributed to the application of molecular marker-assisted selection (MAS) in improving female fertility in cattle, which could accelerate the development of the cattle industry.

The relationships among sire's predicted transmitting ability for daughter pregnancy rate and cow conception rate and daughter's reproductive performance in Canadian Holstein cows

The objectives of this study were to (1) characterize the variability for sire's predicted transmitting ability (PTA) for daughter's pregnancy rate (DPR) and cow conception rate (CCR), (2) determine the relationships among sire's PTA for DPR, sire's PTA for CCR, daughter's parity, and daughter's 305-d mature-equivalent (ME) milk production, and (3) evaluate the associations among sire's PTA for DPR and CCR and daughter's reproductive performance [pregnancy to first artificial insemination (P/AI), pregnancy by 150 d in milk (PR150) and pregnancy loss (PL) after first AI] in Canadian Holstein cows. The data were obtained from 822 lactating Holstein cows from 10 commercial dairy herds located in Alberta. Overall mean (range) for sire's PTA for DPR and CCR was -0.09 (-9.6 to 8.2) and -0.05 (-9.9 to 7.4), respectively. Sire's PTA for DPR was strongly and positively associated with sire's PTA for CCR (r = 0.89; P < 0.01). Sire's PTA for DPR and CCR were weakly and negatively associated with parity (r = -0.15 and -0.17, respectively; P < 0.01); however, the amount of phenotypic variation in sire's PTA for DPR and CCR explainable by parity was small (coefficient of determination; R² = 0.02). The daughter's 305-d ME milk production tended to be weakly but positively associated with sire's PTA for DPR (r = 0.06; P = 0.07) and CCR (r = 0.06; P = 0.10); however, the amount of phenotypic variation in daughter's 305-d ME milk production explainable by changes in sire's PTA for DPR or CCR was small (R² = 0.004 and 0.003, respectively). Overall P/AI, PR150 and PL were 38, 65 and 12%, respectively. Sire's PTA for DPR tended to be associated with P/AI (P = 0.08) but was significantly associated with PR150 (P = 0.03). For every unit increase in sire's PTA for DPR, the estimated probabilities for P/AI and PR150 increased by 6.2 and 7.5%, respectively. Sire's PTA for CCR was not associated with P/AI or PR150. Neither sire's PTA for DPR nor CCR were associated with PL. In summary, sire's PTA for DPR and CCR were highly variable and positively correlated. Sire's PTA for DPR was associated with daughter's P/AI and PR150, but sire's PTA for CCR was not associated with any of the measured reproductive outcomes. Therefore, selecting sires with high PTA for DPR has the potential to improve the reproductive efficiency of Canadian dairy herds.

A Genome-Wide Association Study for Calving Interval in Holstein Dairy Cows Using Weighted Single-Step Genomic BLUP Approach

The aim of the present study was to identify genomic region(s) associated with the length of the calving interval in primiparous (n = 6866) and multiparous (n = 5071) Holstein cows. The single nucleotide polymorphism (SNP) solutions were estimated using a weighted single-step genomic best linear unbiased prediction (WssGBLUP) approach and imputed high-density panel (777 k) genotypes. The effects of markers and the genomic estimated breeding values (GEBV) of the animals were obtained by five iterations of WssGBLUP. The results showed that the accuracies of GEBVs with WssGBLUP improved by +5.4 to +5.7, (primiparous cows) and +9.4 to +9.7 (multiparous cows) percent points over accuracies from the pedigree-based BLUP. The most accurate genomic evaluation was provided at the second iteration of WssGBLUP, which was used to identify associated genomic regions using a windows-based GWAS procedure. The proportion of additive genetic variance explained by windows of 50 consecutive SNPs (with an average of 165 Kb) was calculated and the region(s) that accounted for equal to or more than 0.20% of the total additive genetic variance were used to search for candidate genes. Three windows of 50 consecutive SNPs (BTA3, BTA6, and BTA7) were identified to be associated with the length of the calving interval in primi- and multiparous cows, while the window with the highest percentage of explained genetic variance was located on BTA3 position 49.42 to 49.52 Mb. There were five genes including ARHGAP29, SEC24D, METTL14, SLC36A2, and SLC36A3 inside the windows associated with the length of the calving interval. The biological process terms including alanine transport, L-alanine transport, proline transport, and glycine transport were identified as the most important terms enriched by the genes inside the identified windows.

UFL1 Alleviates LPS-Induced Apoptosis by Regulating the NF-κB Signaling Pathway in Bovine Ovarian Granulosa Cells

Ubiquitin-like modifier 1 ligating enzyme 1 (UFL1) is an E3 ligase of ubiquitin fold modifier 1 (UFM1), which can act together with its target protein to inhibit the apoptosis of cells. Lipopolysaccharides (LPS) can affect the ovarian health of female animals by affecting the apoptosis of ovarian granulosa cells. The physiological function of UFL1 on the apoptosis of bovine (ovarian) granulosa cells (bGCs) remains unclear; therefore, we focused on the modulating effect of UFL1 on the regulation of LPS-induced apoptosis in ovarian granulosa cells. Our study found that UFL1 was expressed in both the nucleus and cytoplasm of bGCs. The results here demonstrated that LPS caused a significant increase in the apoptosis level of bGCs in cows, and also dramatically increased the expression of UFL1. Furthermore, we found that UFL1 depletion caused a significant increase in apoptosis (increased the expression of BAX/BCL-2 and the activity of caspase-3). Conversely, the overexpression of UFL1 relieved the LPS-induced apoptosis. In order to assess whether the inhibition of bGCs apoptosis involved in the nuclear factor-κB (NF-κB) signaling pathway resulted from UFL1, we detected the expression of NF-κB p-p65. LPS treatment resulted in a significant upregulation in the protein concentration of NF-κB p-p65, and knockdown of UFL1 further increased the phosphorylation of NF-κB p65, while UFL1 overexpression significantly inhibited the expression of NF-κB p-p65. Collectively, UFL1 could suppress LPS-induced apoptosis in cow ovarian granulosa cells, likely via the NF-κB pathway. These results identify a novel role of UFL1 in the modulation of bGC apoptosis, which may be a potential signaling target to improve the reproductive health of dairy cows.

Estimation of the Genetic Parameters for Semen Traits in Spanish Dairy Sheep

Simple Summary

The limited studies addressing the estimation of genetic parameters for ram semen traits in different breeds show a wide variation, highlighting the importance of studying these traits for individual breeds. Therefore, this work aimed to estimate genetic parameters for traits related to semen production and quality in five dairy sheep breeds. For that, ejaculates of rams from Assaf, Churra, Latxa Cara Negra, Latxa Cara Rubia, and Manchega breeds were analyzed. Estimates of the genetic covariance structure were obtained with multiple-trait animal models using the average information REML (restricted maximum likelihood) method in the BLUPF90 family of programs. Repeatability estimates for all the traits were also calculated. Heritability estimates were of low to moderate magnitude, although the estimates differed among the breeds. The estimated genetic correlations among the three semen traits showed adequate precision only in the Manchega (MAN) breed. The heritability estimates reported here suggest that improvement of these traits may be achieved by genetic selection.

Abstract

This work aimed to estimate genetic parameters for traits related to semen production and quality in Spanish dairy sheep breeds. For that, ejaculates of rams from Assaf, Churra, Latxa Cara Negra, Latxa Cara Rubia, and Manchega breeds were analyzed to measure volume, semen concentration, and motility. Estimates of variance components were obtained with multiple-trait animal models using the average information REML method in the BLUPF90 family of programs. Repeatability estimates for all the traits were also calculated, with values ranging from 0.077 to 0.304 for the motility and the semen concentration traits, respectively. Heritability estimates were of low to moderate magnitude, ranging from 0.014 (motility in Latxa Cara Rubia) to 0.198 (volume in Churra), although the estimates differed among the breeds. The estimated genetic correlations among the three semen traits showed adequate precision only in the MAN breed. The heritability estimates for the semen traits reported in the present paper suggest an adequate response to selection. The practical extension of these results to the other breeds studied here will be secondary to the estimation of more reliable genetic correlations in these breeds.

Review: Recent advances in bovine in vitro embryo production: reproductive biotechnology history and methods

In vitro production (IVP) of embryos and associated technologies in cattle have shown significant progress in recent years, in part driven by a better understanding of the full potential of these tools by end users. The combination of IVP with sexed semen (SS) and genomic selection (GS) is being successfully and widely used in North America, South America and Europe. The main advantages offered by these technologies include a higher number of embryos and pregnancies per unit of time, and a wider range of potential female donors from which to retrieve oocytes (including open cyclic females and ones up to 3 months pregnant), including high index genomic calves, a reduced number of sperm required to produce embryos and increased chances of obtaining the desired sex of offspring. However, there are still unresolved aspects of IVP of embryos that limit a wider implementation of the technology, including potentially reduced fertility from the use of SS, reduced oocyte quality after in vitro oocyte maturation and lower embryo cryotolerance, resulting in reduced pregnancy rates compared to in vivo-produced embryos. Nevertheless, promising research results have been reported, and work is in progress to address current deficiencies. The combination of GS, IVP and SS has proven successful in the commercial field in several countries assisting practitioners and cattle producers to improve reproductive performance, efficiency and genetic gain.

Symposium review: Challenges and opportunities for evaluating and using the genetic potential of dairy cattle in the new era of sensor data from automation

Sensor data from automation are becoming available on an increasingly large scale, and associated research is slowly starting to appear. This new era of sensor data from automation leads to many challenges but also new opportunities for assessing and maximizing the genetic potential of dairy cattle. The first challenge is data quality, because all uses of sensor data require careful data quality validation, potentially using external references. The second issue is data accessibility. Indeed, sensor data generated from automation are often designed to be available on-farm in a given system. However, to make these data useful-for genetic improvement for example-the data must also be made available off-farm. By nature, sensor data often are very complex and diverse; therefore, a data consolidation and integration layer is required. Moreover, the traits we want to select have to be defined precisely when generated from these raw data. This approach is obviously also beneficial to limit the challenge of extremely high data volumes generated by sensors. An additional challenge is that sensors will always be deployed in a context of herd management; therefore, any efforts to make them useful should focus on both breeding and management. However, this challenge also leads to opportunities to use genomic predictions based on these novel data for breeding and management. Access to relevant phenotypes is crucial for every genomic evaluation system. The automatic generation of training data, on both the phenotypic and genomic levels, is a major opportunity to access novel, precise, continuously updated, and relevant data. If the challenges of bidirectional data transfer between farms and external databases can be solved, new opportunities for continuous genomic evaluations integrating genotypes and the most current local phenotypes can be expected to appear. Novel concepts such as federated learning may help to limit exchange of raw data and, therefore, data ownership issues, which is another important element limiting access to sensor data. Accurate genome-guided decision-making and genome-guided management of dairy cattle should be the ultimate way to add value to sensor data from automation. This could also be the major driving force to improve the cost-benefit relationship for sensor-based technologies, which is currently one of the major obstacles for large-scale use of available technologies.

Association of plasma microRNA expression with age, genetic background and functional traits in dairy cattle

A number of blood circulating microRNAs (miRNAs) are proven disease biomarkers and have been associated with ageing and longevity in multiple species. However, the role of circulating miRNAs in livestock species has not been fully studied. We hypothesise that plasma miRNA expression profiles are affected by age and genetic background, and associated with health and production traits in dairy cattle. Using PCR arrays, we assessed 306 plasma miRNAs for effects of age (calves vs mature cows) and genetic background (control vs select lines) in 18 animals. We identified miRNAs which were significantly affected by age (26 miRNAs) and genetic line (5 miRNAs). Using RT-qPCR in a larger cow population (n = 73) we successfully validated array data for 12 age-related miRNAs, one genetic line-related miRNA, and utilised expression data to associate their levels in circulation with functional traits in these animals. Plasma miRNA levels were associated with telomere length (ageing/longevity indicator), milk production and composition, milk somatic cell count (mastitis indicator), fertility, lameness, and blood metabolites linked with body energy balance and metabolic stress. In conclusion, circulating miRNAs could provide useful selection markers for dairy cows to help improve health, welfare and production performance.

Conserved and variable: Understanding mammary stem cells across species

Postnatal mammary gland development requires the presence of mammary stem and progenitor cells (MaSC), which give rise to functional milk-secreting cells and regenerate the mammary epithelium with each cycle of lactation. These long-lived, tissue-resident MaSC are also targets for malignant transformation and may be cancer cells-of-origin. Consequently, MaSC are extensively researched in relation to their role and function in development, tissue regeneration, lactation, and breast cancer. The basic structure and function of the mammary gland are conserved among all mammalian species, from the most primitive to the most evolved. However, species vary greatly in their lactation strategies and mammary cancer incidence, making MaSC an interesting focus for comparative research. MaSC have been characterized in mice, to a lesser degree in humans, and to an even lesser degree in few additional mammals. They remain uncharacterized in most mammalian species, including "ancient" monotremes, marsupials, wild, and rare species, as well as in common and domestic species such as cats. Identification and comparison of MaSC across a large variety of species, particularly those with extreme lactational adaptations or low mammary cancer incidence, is expected to deepen our understanding of development and malignancy in the mammary gland. Here, we review the current status of MaSC characterization across species, and underline species variations in lactation and mammary cancer through which we may learn about the role of MaSC in these processes. © 2017 International Society for Advancement of Cytometry.

Genetic trends for fertility, udder health and protein yield in Swedish red cattle estimated with different models

The aim of this study was to estimate and compare genetic trends in Swedish Red cattle using a full multiple-trait (MT) model and trait-group-wise models for female fertility, udder health and protein yield. Field data for maiden heifers from 1989 and cows with a first and second lactation between 1990 and 2007 were included. (Co)variance components were estimated prior to prediction of breeding values. The estimated genetic trends were clearly favourable for protein yield and udder conformation, and in most cases neutral to favourable for clinical mastitis and calving to first insemination. In maiden heifers, the trends were neutral for number of inseminations per service period. Unfavourable genetic trends were estimated for number of inseminations in the first two lactations, but the trends seemed less unfavourable from evaluations within trait groups compared with when using the full MT model. Excluding maiden heifer data affected genetic trends less than using trait-group-wise analyses instead of a full MT model. Unfavourable genetic trends in functional traits may be missed unless the traits are evaluated in a MT model including traits under strong selection.

Effect of energy balance profiles on metabolic and reproductive response in Holstein and Swedish Red cows

This study examined the effect of two feeding levels during the antepartum and postpartum period on reproductive performance and blood metabolites (glucose, non-esterified fatty acids (NEFA), insulin) in primiparous Holstein and Swedish Red (SRB) cows, in order to identify possible differences in the way these breeds respond to negative energy balance after calving. A total of 44 cows (22 Holstein, 22 SRB) kept in a loose housing system were included in the study. The control group (HE, n = 23) was fed a diet for high-producing cows (target 35 kg/d energycorrected milk, ECM). A lower feeding intensity (LE, n = 21) was achieved by giving -50% concentrate to target 25 kg/d ECM. Diets were implemented 30 days before expected calving and the cows were monitored for 120 days postpartum. Milk yield and composition, dry matter intake (DMI), live body weight and body condition score (BCS) were assessed to calculate the weekly energy balance (residual feed intake). Blood sampling started before diet implementation and was repeated every 2 weeks until Day 60 postpartum and then once monthly until Day 120. Plasma was kept at -20 °C until analysis for glucose, insulin and NEFA concentrations. Mixed linear models were used to analyse data (SAS 9.3; PROC MIXED). Holstein cows had lower mean energy balance than SRB cows (-4.7 ± 1.4 and -0.9 ± 1.4 MJ, respectively; p = 0.05). SRB cows had higher (p<0.001) BCS (3.3 ± 0.1) than Holstein cows (2.7 ± 0.1) and also higher plasma glucose concentrations from Day -30 to Day 120 relative to parturition (4.1 ± 0.1 and 4.2 ± 0.1 log ; mg/100 ml, respectively; p < 0.05). Overall, breed or diet had no effect on NEFA blood plasma concentrations. However, plasma NEFA concentration levels tended to be higher (p = 0.09) in SRB cows than in Holsteins at Day -14 before calving, indicating higher mobilisation of lipid from adipose tissue already before calving. In contrast, Holstein cows had higher NEFA at Day 14 postpartum than SRB cows (p < 0.05). There were no significant effects of diet or breed on reproductive performance (% pregnant at first AI, days open). However, commencement of luteal activity within 21d postpartum was affected (p < 0.05) by the interaction of breed and diet. These results suggest that Holstein cows prioritise milk production to a larger extent than SRB cows, resulting in a less balanced metabolic profile.

Comparative analysis of SNP candidates in disparate milk yielding river buffaloes using targeted sequencing

River buffalo (Bubalus bubalis) milk plays an important role in economy and nutritious diet in several developing countries. However, reliable milk-yield genomic markers and their functional insights remain unexposed. Here, we have used a target capture sequencing approach in three economically important buffalo breeds namely: Banni, Jafrabadi and Mehsani, belonging to either high or low milk-yield group. Blood samples were collected from the milk-yield/breed balanced group of 12 buffaloes, and whole exome sequencing was performed using Roche 454 GS-FLX Titanium sequencer. Using an innovative approach namely, MultiCom; we have identified high-quality SNPs specific for high and low-milk yield buffaloes. Almost 70% of the reported genes in QTL regions of milk-yield and milk-fat in cattle were present among the buffalo milk-yield gene candidates. Functional analysis highlighted transcriptional regulation category in the low milk-yield group, and several new pathways in the two groups. Further, the discovered SNP candidates may account for more than half of mammary transcriptome changes in high versus low-milk yielding cattle. Thus, starting from the design of a reliable strategy, we identified reliable genomic markers specific for high and low-milk yield buffalo breeds and addressed possible downstream effects.

Risk factors associated with dystocia in a tie stall dairy herd

The aims of the study were to: (1) investigate factors affecting calf birth weight (CBW) and gestation length (GL); and (2) determine risk factors associated with dystocia in 1019 Holstein heifers and cows in a tie stall dairy herd. Calf sex (CS), sire, and GL were related to CBW in primiparous and multiparous cows, with no significant effect of season, age of primiparous cows (AGE) or days in milk (DIM) of multiparous cows at conception. Gestation length was affected by CS in primiparous, with a shorter GL for female versus male calves (275.7 ± 0.5 vs. 278.3 ± 0.4; P < 0.001). Also, GL was shorter in multiparous cows that calved during the cold season compared to those that calved in mild or warm seasons. Primiparous cows had a higher prevalence of dystocia compared to multiparous cows (32.1 vs. 8.5%; P < 0.001), but it was highly variable depending on sire (24.4%–60.0% for primiparous and 0%–21.1% for multiparous). In conclusion, CS, sire, and GL were related to CBW, whereas GL was affected by CS in primiparous and season in multiparous. The CBW was the major factor affecting dystocia in primiparous cows, whereas sire and twin pregnancies were factors related to dystocia in both primiparous and multiparous cows.

Novel approaches to genetic analysis of fertility traits in New Zealand dairy cattle

The fertility of dairy cattle in New Zealand is well below industry targets, and the current New Zealand fertility breeding value (BV) could potentially be improved using additional information and traits. Data from 169 herds were analyzed to determine the benefits of using alternative phenotypic measures in the calculation of the fertility BV. The heritability of calving season day (CSD; calving season day as an integer day of the year) and the probability of an animal calving within 42 d of the planned start of calving (CR42) increased modestly (from 0.0206 to 0.0213 and 0.0087 to 0.0092, respectively) after accounting for the use of intravaginal progesterone-releasing devices for treatment of anestrous cows (anestrum treatment) and induced calvings. Incidence of either anestrum treatment or calving induction as a single binomial trait (AT/IND) had a heritability of 0.0223 and showed moderate genetic correlation with the probability of an animal being mated within 21 d of the planned start of mating (PM21; -0.4473), but much higher with CSD (0.8445). The use of pregnancy diagnosis data allowed fertility information that would otherwise be discarded to be included in analyses; when used to assign a prolonged CSD and a value of 0 for CR42 to animals that failed to calve, it increased the heritabilities of both of these traits (to 0.0278 and 0.0114, respectively). Because CSD was found to be more than twice as heritable as its binary counterpart, it shows potential to replace CR42 as the calving trait used in the fertility BV. Postpartum anestrous interval (PPAI), derived using incomplete premating estrous recording in some herds, had a heritability of 0.0813 and hence has potential as a trait to be included in genetic improvement programs but would require more rigorous recording of estrous during the premating period to be an effective trait. Based on selection index theory, the modifications made to current selection criteria using novel fertility traits increased the accuracy of prediction of fertility merit by more than 12%. Because of the increasing economic importance of fertility traits, and low heritabilities requiring large numbers of recorded daughters to get accurate fertility BV predictions on sires, data recorded on farm will become increasingly important in the genetic improvement of fertility.

Genetic analysis of leg problems and growth in a random mating broiler population

Improvement in growth has been widely reported as the cause of increased incidence of leg problems in broiler chickens. We report herein the genetic relationship between growth and leg problems in a random mating broiler control population. The traits studied were valgus (VL), varus (VR), and tibial dyschondroplasia (TD), which were expressed on a binary scale of 0 (normal) and 1 (abnormal); growth rates from 0 to 4 wk (BWG 0-4) and from 0 to 6 wk of age (BWG 0-6); and residual feed intake from 5 to 6 wk of age (RFI 5-6). A threshold-linear mixed model was employed for the joint analysis of the categorical and linear traits. Incidences of VL, VR, and TD were 26, 4, and 2%, respectively. Heritability of leg problems ranged from 0.11 to 0.13. Phenotypic correlations alluded to an unfavorable relationship between growth and leg problems; however, the genetic relationship between growth and leg problems was extremely weak, ranging from 0.01 to 0.08. There is, therefore, a basis for genetic improvement in leg problems. However, improved management practices would also be important to reduce incidence of leg problems in broiler chickens.

Sire effect on early and late embryonic death in French Holstein cattle

We investigated the effect of maternal sire on early pregnancy failure (between D0, day of insemination and D90) in their progeny during the first and second lactations (n=3508) in the Holstein breed. The estimated breeding value (EBV) for cow fertility of 12 bulls (reliability⩾0.95) was used to create the following three groups: low, medium and high EBV (EBV from -0.7 to 1 expressed as genetic standard deviation relative to the mean of the breed). In their daughters (93 to 516 per bull), progesterone measurement was carried out on the day of artificial insemination (AI; D0) to check whether the cows were in the follicular phase and on D18 to 25 to assess non-fertilisation-early embryonic mortality (NF-EEM). Late embryonic mortality (LEM) and early foetal death (FD) were determined by ultrasonography on D45 and D90 and by the return to oestrus after the first AI. Frequencies of NF-EEM, LEM, FD and pregnancy were 33.3%, 11.7%, 1.4% and 48.5% and incidences were 35.1, 19.0, 2.7 and 51.1, respectively. Sire EBV was significantly related to the incidences of pregnancy failure between D0 and D90, fertilisation failure-early embryonic mortality (FF-EEM) and LEM but not to the incidence of FD between D45 and D90 of pregnancy. The relative risk (RR) of FF-EEM was significantly higher (RR=1.2; P<0.05) for the progeny group of low EBV bulls when compared with high EBV bulls. The same effect was observed when comparing LEM of the progeny groups from the low EBV bulls to those from moderate and high EBV bulls (RR, respectively, of 1.3 and 1.4; P<005). The incidence of FF-EEM was significantly higher when cows were inseminated before 80 days postpartum compared with later, and for the extreme values of the difference between milk fat and protein content measured during the first 3 months of lactation. FF-EEM was also significantly related to the year of observation. The incidence of LEM was higher for the highest producing cows and was influenced by interaction between milk yield×lactation rank and milk yield×milk protein content. In conclusion, this study showed large differences in early pregnancy failure between progeny groups and highlights the interest of accurate characterisation of embryonic death in order to identify potential candidate genes for female fertility.

Invited review: Genetic considerations for various pasture-based dairy systems

Pasture-based dairy systems use grazing to supply significant percentages of the dry matter intake of cows and heifers. Such systems vary from those for which pasture is used only as a supplemental feed for cows primarily fed a total mixed ration to those for which pasture is the primary source of dry matter for the herd. Cows that are optimal in a pasture system share many general characteristics with cows that are appropriate for a nonpasture system, including feed efficiency, maintenance of body condition, reproductive fitness, udder health, longevity, and the ability to adapt to various management systems. However, in such divergent feeding systems, the relative importance of various traits can differ. In pasture systems where cow nutrient demand intentionally coincides with seasonal forage availability, the focus of selection has emphasized fertility and other fitness traits, as well as yields of milk or milk components. Breeds or strains with higher yields of protein and fat typically have advantages in grazing systems that supply milk to solids-based or cheese markets. Holstein cows with high percentages of North American ancestry can work well in grazing systems that include supplemental concentrates or partial mixed rations, particularly if calving intervals are less restrictive. Crossbred cows can be selected for use in specific grazing systems as well as for specific milk markets, with the added advantage of heterosis. Breeds and crosses with high fertility are important for seasonal breeding and calving. The ability of cattle to both milk and maintain sufficient body condition for reproduction is important for any dairy production system but is critical in a seasonal system. Dairy farms that depend on pasture for most of dry matter for cows typically have lower production per cow than nongrazing dairies but have the potential to be economically competitive because of lower operating and overhead costs. Although the principles of selection are similar across a variety of pasture-based and nonpasture systems, we document from studies and observations covered herein that optimal breeds, breed strains, and selection strategies can differ based on varying management constraints and objectives.

Husbandry factors and the resumption of luteal activity in open and zero-grazed dairy cows in urban and peri-urban kampala, Uganda

Contents

The study investigated the influence of selected husbandry factors on interval to resumption of post-partum cyclicity among dairy cows in urban and peri-urban Kampala. A prospective study of 85 day post-partum period of 59 dairy cows in open (n = 38) and zero grazing (n = 21) systems was conducted on 24 farms. Cows of parity 1–6 were recruited starting 15–30 days post-partum. Progesterone (P4) content in milk taken at 10–12 day intervals was analysed using ELISA. The cow P4 profiles were classified into ‘normal’ (< 56 days), ‘delayed’ (> 56 days), ‘ceased’ or ‘prolonged’ (if started < 56 days but with abnormal P4 displays) resumption of luteal activity and tested for association with husbandry and cow factors. Of the 59 cows, luteal activity in 81.4% resumed normally and in 18.6%, delayed. Only 23.7% maintained regular luteal activity, while the others had ceased (10.2%), prolonged (37.3%) or unclear luteal activity (20.3%). There were no differences between open and zero-grazed cows. Milk production was higher (p < 0.05) in zero than open grazing, in urban than peri-urban and in cows fed on brew waste (p < 0.001) compared with mill products and banana peels. Results suggest that luteal activity resumes normally in a majority of cows, although only a minority experienced continued normal cyclicity once ovulation had occurred, in the two farming systems irrespective of feed supplements or water, and that supplementing with brew waste is beneficial for milk production.

Reaction norm of fertility traits adjusted for protein and fat production level across lactations in Holstein cattle

A total of 304,001 artificial insemination outcomes in up to 7 lactations from 142,389 Holstein cows, daughters of 5,349 sires and 101,433 dams, calving between January 1995 and December 2007 in 1,347 herds were studied by a reaction norm model. The (co)variance components for days to first service (DFS), days open, nonreturn rate in the first service (NRFS), and number of services per conception were estimated by 6 models: 3 Legendre polynomial degrees for the genetic effects and adjustment or not for the level of fat plus protein (FP) production recorded at day closest to DFS. For all traits and type of FP adjustment, a second degree polynomial showed the best fit. The use of the adjusted FP model did not increase the level of genetic (co)variance components except for DFS. The heritability for each of the traits was low in general (0.03-0.10) and increased from the first to fourth calving; nevertheless, very important variability was found for the estimated breeding value (EBV) of the sires. The genetic correlations (rg) were close to unity between adjacent calvings, but decreased for most distant parities, ranging from rg=0.36 (for DFS) to rg=0.63 (for NRFS), confirming the existence of heterogeneous genetic (co)variance components and EBV across lactations. The results of the eigen decomposition of rg shows that the first eigenvalue explained between 82 to 92% and the second between 8 to 14% of the genetic variance for all traits; therefore, a deformation of the overall mean trajectory for reproductive performance across the trajectory of the different calving could be expected if selection favored these eigenfunctions. The results of EBV for the 50 best sires showed a substantial reranking and variation in the shape of response across lactations. The more important aspect to highlight, however, is the difference between the EBV of the same sires in different calvings, a characteristic known as plasticity, which is particularly important for DFS and NRFS. This component of fertility adds another dimension to selection for fertility that can be used to change the negative genetic progress of reproductive performance presented in this population of Holstein cows. The use of a reaction norm model should allow producers to obtain more robust cows for maintenance of fertility levels along the whole productive life of the cows.

A deletion in the bovine FANCI gene compromises fertility by causing fetal death and brachyspina

Fertility is one of the most important traits in dairy cattle, and has been steadily declining over the last decades. We herein use state-of-the-art genomic tools, including high-throughput SNP genotyping and next-generation sequencing, to identify a 3.3 Kb deletion in the FANCI gene causing the brachyspina syndrome (BS), a rare recessive genetic defect in Holstein dairy cattle. We determine that despite the very low incidence of BS (<1/100,000), carrier frequency is as high as 7.4% in the Holstein breed. We demonstrate that this apparent discrepancy is likely due to the fact that a large proportion of homozygous mutant calves die during pregnancy. We postulate that several other embryonic lethals may segregate in livestock and significantly compromise fertility, and propose a genotype-driven screening strategy to detect the corresponding deleterious mutations.

Identification of goat mammary stem/progenitor cells

Goat mammary gland epithelial cells have been used to establish primary and permanent cell lines, but to date, no data have been available regarding mammary stem cells (MaSCs) in this species. The detection and characterization of goat MaSCs is an important task for a better understanding of the cyclic character of mammary gland development, which will also offer the potential for manipulation of lactation yield and persistency. The objective of the present study was to demonstrate that a subpopulation of goat MaSCs resides in the goat mammary gland. Mammary tissue from lactating Saanen goats (Capra hircus) was dissociated and processed to a single-cell suspension. Using an in vitro colony-forming assay, we demonstrated that distinct colony types, which expressed specific lineage markers, arose from unipotent progenitors. Using two different growth media, we showed that the frequencies of caprine clonogenic progenitors differed according to growth conditions. Goat epithelial cells were transplanted under the kidney capsule of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice, where they formed organized, bilayered structures. Our results indicate the presence of goat MaSCs in the caprine mammary gland. To our knowledge, these data represent the first description of the tissue hierarchy of the goat mammary gland and demonstrate the regenerative potential of adult goat MaSCs.

Effect of polymorphisms at the STAT5A and FGF2 gene loci on reproduction, milk yield and lameness of Holstein cows

The objective of this study was to investigate the association of polymorphisms at the STAT5A and FGF2 gene loci with fertility, lactation milk yield and lameness in dairy cattle. Five hundred and eighteen primiparous Holstein cows were included in the study. Several reproductive traits were considered including conception rate (0/1) at first insemination, conception rate (0/1) in a 305-day lactation, number of inseminations per conception, interval (days) from calving to conception for cows that conceived in the first 305 days of lactation and age at first calving. Milk yield and lameness incidence were also recorded. Genotyping was performed using PCR-RFLP. The effect of allele substitution at each gene locus on reproductive traits, milk yield and lameness was assessed with single-trait mixed linear models. No significant associations were found between reproduction traits and any of the studied polymorphisms, apart from age at first calving, for which STAT5A polymorphism had a suggestive effect (P = 0.077). In addition, no significant effect of any polymorphism on lameness was found. Replacement of the C by G allele at the STAT5A locus was associated with a significant (P<0.05) increase in lactation milk yield, suggesting that this locus could be considered in gene assisted selection for the genetic improvement of milk production.