Fertility Of Cows Research Articles

Validating the female fertility estimated breeding value in Australian commercial dairy herds

We conducted a retrospective cohort study to validate the efficacy of the Australian multitrait fertility estimated breeding value (EBV). We did this by determining its associations with phenotypic measures of reproductive performance (i.e., submission rate, first service conception rate, and early calving). Our secondary aim was to report the associations between these reproductive outcomes and management and climate-related factors hypothesized to affect fertility. Our study population included 38 pasture-based dairy herds from the northern Victorian irrigation region in Australia. We collected records for 86,974 cows with 219,156 lactations and 438,578 mating events from the date on which managers started herd recording until December 2016, comprising both fertility-related data such as insemination records, calving dates, and pregnancy test results, and systems-related data such as production, herd size, and calving pattern. We also collected hourly data from 2004 to 2017 from the closest available weather station to account for climate-related factors (i.e., temperature humidity index; THI). Multilevel Cox proportional hazard models were used to analyze time-to-event outcomes (days to first service, days to cow calving following the planned herd calving start date), and multilevel logistic regression models for binomial outcomes (conception to first service) in the Holstein-Friesian and Jersey breeds. A 1-unit increase in daughter fertility EBV was associated with a 5.4 and 8.2% increase in the daily hazard of calving in the Holstein-Friesian and Jersey breeds respectively. These are relative increases (i.e., a Holstein-Friesian herd with a 60% 6-wk in-calf rate would see an improvement to 63.2% with a 1-unit increase in herd fertility EBV). Similar results were obtained for submission and conception rate. Associations between 120-d milk yield and reproductive outcome were complicated by interactions with 120-d protein percentage and calving age, depending on the breed and outcome. In general, we found that the reproductive performance of high milk-yielding animals deteriorated faster with age than low milk-yielding animals, and high protein percentage exacerbated the differences between low and high milk-yielding animals. Climate-related factors were also associated with fertility, with a 1-unit increase in maximum THI decreasing first service conception rate by 1.2% for Holstein-Friesians but having no statistically significant association in the Jersey breed. However, THI had a negative association in both breeds on the daily hazard of calving. Our study validates the efficacy of the daughter fertility EBV for improving herd reproductive performance and identifies significant associations between 120-d milk and protein yields and THI on the fertility of Australian dairy cows.

Effect of Timing of Artificial Insemination on Fertility of Cows and Calf Sex Ratio in Arsi Cows

An on-station study was conducted to investigate the effect of the interval between artificial insemination (AI) and the beginning of estrus on the fertility and sex ratio of offspring in Arsi cows. Standing to be mounted was considered the beginning of estrus, and artificial inseminations were made 6 h (Group 1), 12 h (Group 2), 18 h (Group 3) and 24 h (Group 4) after the onset of estrus in the cows. Overall, 50 cows with parity between 2 and 4, body weight ranging from 250 to 300 kg were used for the purpose of this study. Ovulation was synchronized by administration of PGF2α hormone. Pregnancy diagnosis was performed by rectal palpation at 90 to 120 days post AI. Pregnancy rates were 60%, in each of the Groups 1, 2, 3 and 50% in group 4. The highest female to male ratio (P=0.041) of calves was obtained in Group 1. Whereas the highest male to female ratio was recorded in group 4. The number of artificial inseminations per pregnancy was within the economical limits in all groups. In conclusion, the results of this study indicated that the variation in time interval between the onset of estrus and artificial insemination alters the sex ratio of offspring in Arsi cows without affecting fertility parameters.

GnRH dose at initiation of a 5-day CO-Synch + P4 for fixed time artificial insemination in suckled beef cows

The objective of the present study was to evaluate the effect of GnRH dose administered at initiation (GnRH-1) of a 5-day CO-Synch + P4 protocol on ovulatory response, expression of estrus, and fertility in suckled beef cows. Suckled beef cows (n = 1101) at four locations were randomized to receive either 100 or 200 µg of gonadorelin acetate at initiation (D-8) of a 5-day CO-Synch + P4 protocol concurrently with insertion of an intravaginal progesterone (P4) device. On D-3 the P4 device was removed, two doses of prostaglandin F2α were administered concurrently and a patch was applied to evaluate expression of estrus. Artificial insemination was performed 72 h after P4 device removal (D0) simultaneously with the administration of 100 µg of gonadorelin acetate (GnRH-2). Increasing GnRH dose at initiation of a 5-day CO-Synch + P4 did not enhance ovulatory response (P = 0.57) to GnRH-1, expression of estrus (P = 0.79), nor pregnancies per AI (P/AI; P = 0.91). Both follicle size (quadratic) and circulating P4 (linear) affected (P < 0.01) ovulatory response to GnRH-1 independent of dose. Cows that had ovulation to GnRH-1 had smaller (P < 0.001) follicle size on D-3 and reduced (P = 0.05) expression of estrus compared to cows that did not have ovulation to GnRH-1, however, P/AI did not differ (P = 0.75). In conclusion, increasing the dose of GnRH-1 in the 5-day CO-Synch + P4 protocol did not enhance ovulatory response, expression of estrus, or P/AI in suckled beef cows.

Effect of subclinical endometritis and flunixin meglumine administration on pregnancy in embryo recipient beef cows

Fertility of recipient beef cows with subclinical endometritis (SCE) that did or did not receive flunixin meglumine (FM) treatment were compared following transfer of d 7 embryo. The study population comprised of 600 Angus cross cows that expressed estrus following Select-Synch + CIDR (Controlled Internal Drug Release) estrus synchronization protocol. At the time of embryo transfer, approximately 3 wk after sampling for subclinical endometritis, cows were randomly allocated either to receive FM treatment (500 mg of Banamine®; n = 300) or not (Control; n = 300). The effect of subclinical endometritis (at ≥ 1% PMN on endometrial cytology by cytobrush method) and FM treatment on pregnancy/embryo transfer (P/ET, %) were evaluated by mixed model. Of the 600 cows, 323 (53.8%) became pregnant; 55.0% (165/300) cows that received FM treatment vs. 52.7% (158/300) control cows (P > 0.1), and 55.9% (266/476) normal vs. 46.0% (57/124) subclinical endometritis cows (P < 0.05). There was a trend for treatment by subclinical endometritis for P/ET (P = 0.09). Pregnancy was recorded in 55.3% (134/242) of normal and 53.4% (31/58) of subclinical endometritis cows that received FM treatment, and in 56.4% (132/234) of normal and 39.4% (26/66) of subclinical endometritis cows that did not receive FM treatment (P = 0.09). In conclusion, subclinical endometritis in recipient beef cows resulted in lower P/ET. Though not significant in cows with subclinical endometritis, FM treatment resulted in 14.0% points more pregnancy compared with control.

Reproduction in Domestic AnimalsEarly View CORRIGENDUMFree Access This article corrects the following: Posters Volume 57Issue S4Reproduction in Domestic Animals pages: 65-106 First Published online: September 27, 2022 First published: 19 February 2023 https://doi.org/10.1111/rda.14299AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Correction to Proceedings of the 25th Annual Conference of the European Society for Domestic Animal Reproduction (ESDAR), 28 September–2 October 2022, Thessaloniki, Greece | Poster Abstracts The authors wish to bring the readers' attention to the missing Poster abstracts below: P106 Association of post-partum rumen contraction score with fertility in Holstein dairy cows G. Valergakis1, N. Siachos1, A. Kougioumtzis1, N. Panousis2 and V. Tsiamadis1 1Laboratory of Animal Husbandry, School of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece, 2Clinic of Farm Animals, Faculty of Veterinary Medicine, School of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece. The study dataset included 719 cows from 9 farms. Rumen contraction score (RCS) was assessed with auscultation of the left paralumbar fossa, once, 2 hours after the morning feeding, at days 0, +2, +4 and +8 relative to calving; RCS was considered as a binary trait (RCS1: 0–1 contraction/2 min, RCS2: 2 or more contractions/2 min). Time from calving to: a) first artificial insemination (AI) by 120 days in milk (DIM) (1stAI_120, n = 502), b) positive pregnancy outcome at 1st AI by 120 DIM (PPREG_1stAI_120, n = 155) and c) positive pregnancy outcome by 200 DIM (PPREG_200, n = 313), were recorded. Kaplan–Meier time-to-event and Cox-proportional hazard regressions (hazard ratio, HR) analyses were performed for the above reproductive traits, with SPSS.25. No associations were detected between RCS and the traits considered, either at 0d or at +2d. Several trends were identified at +4d; for cows with RCS1 and RCS2, mean (±se) time to: a) 1stAI_120 was 101.1 ± 3.2d vs. 93.7 ± 1.0d (P = 0.081) and b) PPREG_1stAI_120 was 109.8 ± 3.7d vs. 101.0 ± 1.3d (P = 0.077). Cows with RCS2 tended to have a higher PPREG_200 hazard ratio compared to RCS1 ones (HR 1.8; 95% CI: 0.9–3.6, P = 0.09). At +8d, for cows with RCS1 and RCS2, mean (±se) time to: a) 1stAI_120 102.1 ± 2.6d vs. 93.3 ± 1.0d (P = 0.012), b) PPREG_1stAI_120 was 109.3 ± 2.8d vs. 101.0 ± 1.3d (P = 0.05) and c) PPREG_200 was 174.9 ± 5.0d vs. 157.7 ± 2.2d (P = 0.02). Cows with RCS2 had a higher PPREG_200 hazard compared to RCS1 ones (HR 2.0; 95% CI: 1.2–3.2, P = 0.005). Cows with RCS1 and RCS2 did not differ in hazard for 1stAI_120 and PPREG_1stAI_120, either at +4d or at +8d. Early post-calving RCS merits research as a warning tool for future reproductive performance. The organizers of the meeting would like to apologize for this error and any confusion it may have caused. Reference Proceedings of the 25th annual conference of the European Society for Domestic Animal Reproduction (ESDAR), 28. September – 2. October 2022, Thessaloniki, Greece. Reproduction in Domestic Animals, (2022). 57(S4), 65– 106. https://onlinelibrary.wiley.com/doi/epdf/10.1111/rda.14244 Early ViewOnline Version of Record before inclusion in an issue ReferencesRelatedInformation

Gene substitution effect of bovine heat shock protein beta-1 gene polymorphism on age at calving in Indian dairy cattle

The study was planned with objective to screen single nucleotide polymorphisms (SNPs) in bovine HSPB1 gene and to find its effect on age at calving in Karan-Fries (Bos taurus × Bos indicus) and Sahiwal (Bos indicus) breeds of cattle. Genomic DNA was extracted from whole blood of 180 cows of both breeds. Based on publically available bovine HSPB1 gene sequence, one primer set was used for polymerase chain reaction amplification of the target region. Further DNA sequencing revealed a transition of thymine to cytosine at SNP rs208395876 in 5’UTR and a silent transversion of guanine to thymine at SNP rs723061520 in first coding sequence of bovine HSPB1 gene in both the studied breeds. Effect of individual SNP genotypes of bovine HSPB1 gene with age at calving (months) was analyzed separately in both breeds via regression using a repeated gene substitution MIXED model and least-squares means.The overall observed heterozygosity in both breeds and the F-Statistics values indicated that there was lesser genetic diversity in studied genomic region of bovine HSPB1 gene in Bos indicus compared to crossbred cattle. Association analysis revealed that SNP rs208395876 significantly delayed age at calving in Karan-Fries cows. In conclusion, the studied genomic region of bovine HSPB1 gene is polymorphic. In addition, these polymorphisms were informative with regard to age at calving of crossbred cows. Therefore, this gene is an important candidate for cow fertility.

Estimation of the Genetic Components of (Co)variance and Preliminary Genome-Wide Association Study for Reproductive Efficiency in Retinta Beef Cattle.

In this study, we analyzed the variation of reproductive efficiency, estimated as the deviation between the optimal and real parity number of females at each stage of the cow's life, in 12,554 cows belonging to the Retinta Spanish cattle breed, using classical repeatability and random regression models. The results of the analyses using repeatability model and the random regression model suggest that reproductive efficiency is not homogeneous throughout the cow's life. The h2 estimate for this model was 0.30, while for the random regression model it increased across the parities, from 0.24 at the first calving to 0.51 at calving number 9. Additionally, we performed a preliminary genome-wide association study for this trait in a population of 252 Retinta cows genotyped using the Axiom Bovine Genotyping v3 Array. The results showed 5 SNPs significantly associated with reproductive efficiency, located in two genomic regions (BTA4 and BTA28). The functional analysis revealed the presence of 5 candidate genes located within these regions, which were previously involved in different aspects related to fertility in cattle and mice models. This new information could give us a better understanding of the genetic architecture of reproductive traits in this species, as well as allow us to accurately select more fertile cows.

Assessment of influence of duration of the service period on the milk yield of cows

The Ural type of the Russian Black-and-White mottled breed features high rates of milk yield, good suitability for industrial milking technology, but the duration of their productive longevity is 2.4–2.6 lactations only. The decline in productive longevity is associated, in particular, with qualities of reproductive system. As a result of the conducted researches, it was found that due to elongation of lactation (over 305 days), more milk was obtained by 847–890 kg, or by 9.5–10.0%. At the same time, there is a decrease in MFF and MFP in milk for 305 days of lactation: by 0.01–0.02% for fat and by 0.02% for protein. The highest average daily milk yield was recorded in lactation duration of 305 days. The daughters of all assessed servicing bulls had the same service period of 132–134 days. It is 52–54 days higher than optimal indicators, or by 65–68%. The fertility index of cows exceeds 48%, so we can say that the fertility of cows is good. The fertility potential of the livestock is good and decrease of service period duration will increase the efficiency of dairy cattle breeding in the farm.

Deterioration of mitochondrial biogenesis and degradation in the endometrium is a cause of subfertility in cows.

To investigate possible causes of reproductive failure, we conducted global endometrial gene expression analyses in fertile and subfertile cows. Ingenuity pathway analysis showed that RICTOR and SIRT3 are significant upstream regulators for highly expressed genes in fertile cows, and are predicted to be activated upstream regulators of normal mitochondrial respiration. Canonical pathway analysis revealed that these highly expressed genes are involved in the activation of mitochondrial oxidative phosphorylation. Therefore, in subfertile cows, the inactivation of RICTOR and SIRT3 may correlate with decreased capacity of mitochondrial respiration. Furthermore, the expression levels of most mitochondrial DNA genes and nuclear genes encoding mitochondrial proteins were higher in subfertile cows. The mitochondrial DNA copy number was significantly higher in the endometrium of subfertile cows, whereas the ATP content did not differ between fertile and subfertile cows. Quantitative reverse transcription-PCRanalysis demonstrated that the expression of PGC1a, TFAM, MFN1, FIS1, and BCL2L13 were significantly lower in subfertile cows. In addition, transmission electron microscopy images showed mitochondrial swelling in the endometrial cells of the subfertile cow. These results suggest that poor-quality mitochondria accumulate in the endometrium owing to a reduced capacity for mitochondrial biogenesis, fusion, fission, and degradation in subfertile cows, and may contribute to infertility.

Milk fatty acids as indicators of delayed commencement of luteal activity in dairy cows in early lactation.

Excessive mobilization of adipose reserves due to severe negative energy balance in early lactation may be detrimental to dairy cow fertility at individual and herd level. Reproductive efficiency is one of the main factors influencing herd profitability and a strategy for early detection and management of cows with delayed resumption of cyclicity will result higher conception rate, decreased proportion of cows with extended lactation, fewer inseminations per conception and lower culling rates due to reproductive disorders. Using two groups of dairy cows (Holstein n=37, Swedish Red breed [SRB] n=49), we investigated potential differences between cows with different commencement of luteal activity (CLA) and the feasibility of using milk fatty acids (MFAs) as predictors of delayed CLA. Milk samples for progesterone analysis were collected twice weekly during the first six weeks in milk. The concentrations of the MFAs C14:0, C16:0, C18:0 and C18:1 cis-9 in milk (g/100 g milk) and in milk fat (g/100 g fat) were analysed by Fourier transform infrared spectroscopy and individual MFA profiles were calculated by weeks in milk. Commencement of luteal activity was defined as the first day with milk progesterone concentrations >3ng/ml at two successive measurements. The study population was categorized as early (n=42) or late (n=44) CLA, using the median value of 21 DIM as the cut-off. Analysis of the data revealed that CLA was correlated with the proportion of some specific MFAs, where cows with delayed CLA had lower IGF-1 (92.9 ± 7.9 vs. 114.1 ± 7.9ng/ml; p=.05) and C14:0 levels (10.4 ± 0.2 vs. 11.5 ± 0.2g/100 fat; p < .01) and higher C18:0 (9.6 ± 0.2 vs. 8.9 ± 0.6g/100 fat; p < .01) and C18:1 cis-9 levels (24.9 ± 0.4 vs. 23.5 ± 0.4g/100 fat; p < .05). Delayed CLA (mean 34 days) was predictable for approximately 80% of cows based on C18:0 or C18:1 cis-9 concentrations in week 2 postpartum. Overall, MFAs (C18:0 and C18:1 cis-9) as biomarkers were better indicators than beta-hydroxybutyrate or non-esterified fatty acids in early detection of cows with delayed or normal CLA. The MFA concentrations in milk samples from cows in early lactation can thus be used as a non-invasive method to identify cows at risk of delayed CLA, acting as potential biomarkers for future reproductive performance.

ВЛИЯНИЕ «СТИМУЛИНА» И «ФЕРРАМИНОВИТА» НА СОСТАВ КРОВИ, ПОКАЗАТЕЛИ РЕЗИСТЕНТНОСТИ И СПЕРМОПРОДУКЦИИ У БЫКОВ-ПРОИЗВОДИТЕЛЕЙ

Cattle breeding is one of the most knowledge-intensive and dynamically developing industries, occupying one of the leading places in the agro-industrial complex of Russia. An increase in the intensity of cattle breeding technology, in general, leads to a decrease in the overall resistance and immune status of animals. Against this background, metabolic processes and changes in the reproductive system of breeding bulls decrease. The high reproductive capacity of producers ensures high fertilization and fertility of cows, thereby increasing the efficiency of cattle breeding as an industry. Balanced feeding and active exercise are necessary to ensure the safety of health, sexual activity and high quantitative and qualitative indicators of sperm of breeding bulls. As a result of the conducted biochemical studies, significant violations of metabolic processes in breeding bulls were revealed. By making adjustments to their diets, it was not possible to stabilize metabolism and resistance indicators. As a result of the use of injections of complex drugs "Stimullin" and "Ferraminovit" in the body of bulls, the content of molon dialdehyde, liver enzymes AST and ALT, sodium decreased several times, and the amount of glucose increased. The adjustment of diets and the use of drugs contributed to an increase in the indicators of natural resistance and the cellular composition of animal blood: BASC increased by 19.9%, LASC - by 12.4%, FA-11%, FI-14.9%, the functional activity of neutrophils in the spontaneous and stimulated test increased by 38.4% and 36.1%, the reserve index by 13.2%; the coefficient of metabolic activity increased – by 2 times The number of ejaculates in 5 months became higher in bulls with normal biochemical parameters – 36 versus 26 in bulls with metabolic disorders. The use of complex drugs "Stimullin" and "Ferraminovit" contributed to an increase in metabolic processes, indicators of natural resistance and sperm production.

Using mid-infrared spectroscopy to identify more fertile cows for insemination to sexed semen

Context Broader applications of milk mid-infrared spectral data could add value to milk-recording data. One such application is to rank cows on the probability of conception to first service (MFERT) which could help prioritise cows for insemination with dairy sexed semen (SS). Aims This study compared the use of MFERT estimates against two other approaches, to (1) identify most and least fertile dairy cows and (2) prioritise cows predicted to be most fertile for first service insemination with SS. Methods Mid-infrared spectral data from first herd test after calving was used to generate 13 379 MFERT predictions for 76 cohorts. Reproduction records were used to calculate reproductive parameters, calf numbers and net benefit, i.e. calf values minus mating costs, for two breeding programs. Breeding program 1 used SS and conventional dairy semen, while Breeding program 2 used SS, conventional dairy and beef semen. Three semen-allocation approaches were compared, namely, allocation via MFERT, calving date (CDATE) or assignment via random number generator (RANDOM). Key results MFERT significantly outperformed (1) RANDOM in identifying cows most and least likely to calf after first insemination (P &lt; 0.05), and (2) both CDATE and RANDOM in identifying cows most and least likely to calf overall (P &lt; 0.05). This resulted in up to 1.5 and 4.5 more dairy heifer calves, in Breeding programs 1 and 2 respectively, and up to six fewer dairy-beef calves in Breeding program 2. Differences in net benefit among semen-allocation approaches were modest, although generally favoured MFERT. Few significant differences between MFERT and CDATE were found. However, significant net benefit differences among all three semen-allocation approaches were seen in Breeding program 2. Conclusions MFERT outperformed CDATE and RANDOM in identifying most and least fertile cows. Realised net benefits of semen allocation by MFERT over other approaches were modest. Given the impact of semen type and dairy-beef calf prices value proposition will vary. Implications Our study confirmed that MFERT can add value to milk recording data by identifying the most and least fertile cows. As MFERT value is sensitive to individual farm parameters, incorporation alongside other fertility parameters into a decision support tool is desirable.

Improving Fertility in Friesian Cows by Synchronization of Fixed Time Insemination

Improving Fertility in Friesian Cows by Synchronization of Fixed Time Insemination

Temporal trends in estimated breeding values for daughter fertility in Holstein and Jersey cows in the Australian dairy industry

Context Milk yield and fertility are negatively genetically correlated in dairy cows, so selection for milk yield would be expected to result in genetic deterioration in fertility unless there is concurrent selection for fertility. Aim The main study aim was to describe temporal trends in estimated breeding values (Australian Breeding Values, ABVs) for daughter fertility for Holstein and Jersey cows in Australian dairy herds. Methods A retrospective descriptive study was conducted using milk recording and ABV data from cows in commercial dairy herds. Calvings and lactations from 1980 to 2022 were used, along with ABVs for cows that calved over that period and for sires of those cows. Herd-year mean estimated breeding values were calculated for each breed as the means for cows of that breed that calved in the herd that year. Key results Daughter fertility ABVs declined (i.e. deteriorated) markedly in Holsteins in the Australian dairy industry, commencing before 1980. Rates of decline were most rapid in sires, less rapid in cows and least rapid at herd level. Selection pressure for cows with higher daughter fertility ABVs due to cow culling decisions was probably occurring within Australian herds but any such effect was minimal. The decline in cow daughter fertility ABVs is being reversed, but recovery of herd means in the study population has been slow. The rate of decline in daughter fertility ABVs in Jersey cows was less than for Holsteins. Conclusions Over a period of genetic deterioration, then recovery for a trait, genetic trends in sires are not closely related to genetic trends at herd level. The rapid decline in daughter fertility ABVs for sires probably resulted in substantial reductions in herd reproductive performance and cow longevity in Holstein herds in the Australian dairy industry. Under current trends, it will be a considerable time before the adverse effects of the decline in daughter fertility ABVs are fully reversed. Implications An important ongoing task for animal breeding is to identify and monitor traits that may become important for farmers and community in future but may be declining genetically under current selection decisions.

Variability of fertility indicators in Ayrshire firstcalf heifers under the influence of early lactation

The basic value for optimizing the reproduction of the herd in dairy cattle breeding is the ability of cows to procreate offspring - fertility. It is a complex feature, characterized by many indicators and due to a complex of factors. The goal of our work was to reveal and to study these indicators and factors. The studies were carried out on Ayrshire cows of the Megrega breeding farm (the Republic of Karelia). The average milk yield per cow is over 9,000 kg of milk per year. Fertility indicators were taken into account for 5 years according to the data of 3866 lactations. The following fertility indicators were analysed: the indifference period; the period of insemination; the service period; fertilization from the first insemination; conception index (number of inseminations per conception); early embryonic death. We have analysed the relationship of these indicators with age, the amount of milk yield in general for lactation and during the early lactation period. An increase in the level of milk yield of cows during the current lactation up to 10,000 kg of milk or more was accompanied by a decrease in fertilization after the first insemination from 78.1 to 33.6%, as well as a significant deterioration in other main indicators of reproduction. The study established the relationship between the level of productivity of first-calf heifers during the early lactation period and fertility indicators. The greatest influence on fertility indicators during the early lactation period and insemination was exerted by the level of milk yield in the 1st month of the first lactation. The worst reproductive abilities were shown by first-calf heifers with an average daily milk yield of 34 kg or more. The results obtained can be used in further research on the development of selection indices, selection according to which can provide a high genetic trend in milk yield while maintaining and developing the progressive fertility of dairy cows.

Administração de prostaglandina F2 alfa no momento da inseminação artificial não afeta a produção de embriões bovinos

ABSTRACT: Treatment with prostaglandin F2α (PGF) induces ovulation and increases conception rates in cows, while improving embryo production in buffalos. However, its effect on superovulated cows is unknown. This study verified whether single PGF administration concurrent with artificial insemination (AI) improves fertilization and embryo production rates in superovulated cows. In each replicate, embryo donor cows were equally allocated to two groups: the untreated control and PGF groups. The latter of which received 482 µg of cloprostenol concurrent with the first AI. Each cow (n = 35) was subjected to two superovulations (SOV) in a crossover design (total = 70 embryo collections). In the control and PGF groups, respectively, the observed responses were [median (95% CI)]: 12 (10-18) and 15 (12-18) total structures, 9 (7-11) and 7 (6-10) viable embryos, 1 (0-1) and 1 (1-3) degenerated embryos, and 1 (0-3) and 2 (0-5) oocytes (P &gt; 0.05). In conclusion, single PGF treatment concurrent with the first AI did not affect embryo production in superovulated cows.

Heat stress effects on fertility and reproductive health problems of dairy cows in a selected area of Bangladesh

Rifat J. Sumi, Ziban C. Das, Mohammad N. Hoque, Abu N. M. A. Rahman, Mohammad T. Islam and Anup K. Talukder. Journal of Animal Reproduction and Biotechnology 2022;37:266-75. https://doi.org/10.12750/JARB.37.4.266

Bioclimatic interference in fertility in cows in the Amazon biome

The objective was to evaluate the correlation between environmental temperature-humidity index (THI), rectal temperature (RT), plasma cortisol concentration and pregnancy rate in embryo recipient cows in the Amazon biome. Embryo recipients (n=235) underwent estrus synchronization via simplification of the P36 protocol for Fixed-Time Embryo Transfer (TETF). On days zero (D0), eight (D8) and day 16 (D16), the rectal temperature of the recipient cows was measured, as well as the ambient temperature and relative humidity. On the 16th day after the start of the synchronization protocol (D16), each recipient received an embryo transferred after being diagnosed with a corpus luteum (CL) in one of the ovaries by ultrasonography (US) and, from each of them, a blood sample was collected by venipuncture of the coccygeal vein, in tubes with ethylenediaminetetraacetic acid (EDTA) as an anticoagulant to obtain blood plasma, where cortisol was measured by radioimmunoassay (RIA) in solid phase, using commercial kits. It was found that in the group of pregnant cows, the mean values of the parameters RT, plasma cortisol and THI (P &lt; 0.05) were lower than those presented in the group of non-pregnant cows. Moreover, between the two groups there were positive and significant correlations between RT and THI (P &lt; 0.05), as well as in relation to plasma cortisol parameters and THI (P &lt; 0.05). It is concluded that it is possible to validate the use of RT and THI as an auxiliary tool for estimating plasma cortisol concentrations.

The influence of Holstein crossbreeding on the reproductive qualities of Black-and-White cows

The purpose of the research was to study the main indicators of the reproductive ability of Black-and-White cows, depending on the proportion of Holstein genes. As the material for the research there were taken the data of breeding and zootechnical records of cows of Black-and-White breed of CJSC Semenovsky Breeding Plant of the Mari El Republic. The results of the research showed that with an increase in the proportion of thorough-bredness on the Holstein breed the reproductive ability of cows improved. Thus, the first-calf heifers with a low proportion of Holstein genes (up to 12.5 %) had the latest age of the first fruitful insemination and the first calving (21.9 months and 32.3 months). With an increase in thorough-bredness up to 87.6 % and more, the age for the first insemination decreased by 7.7 months (31.8 %), the age of the first calving - by 7.4 month (21.8 %), fertility index increased by 5.8 (14.6 %). At the same time, the duration of the service period in high-blooded animals increased by 18.8-26.4 days (15.8-23.8 %). The duration of the calving interval in all genetic groups exceeded the optimal time and changed in accordance with the change in the service period. The longest calving interval was in cows with the thorough-bredness degree of 87.6 % (13.8 months), which was 0.1-0.7 months longer than in animals of other genetic groups. There was a low coefficient of reproductive ability of the studied animals of all genetic groups ‒ 0.91-0.93. The significant influence of Holstein genes on the age for the first fruitful insemination (ɳ2 = 9.57 %), the first calving (ɳ2 = 8.80 %) and the fertility of cows (ɳ2 = 1.98 %) (P≤0.05) was established. The effect of the genotype on the duration of the service period and calving interval was weak (ɳ2 = 0.09 % and ɳ2 = 0.26 %) and unreliable.

Peripartum supplementation of nutrients in Gir cows improves the feed intake, blood metabolic profile and postpartum fertility

The study evaluated the effect of supplementation of rumen protected choline (RPC) and fat (RPF) alone and in combination, and injection Vit-E + selenium on feed intake, blood metabolic profile and postpartum fertility in transition Gir cows. Forty advanced (8 months) pregnant cows were divided into five equal groups (T1 to T5, n=8) and were managed individually from 30 days prepartum till 60 days postpartum. Cows in T1 group were fed basal diet, those in T2 to T5 groups received additional oral supplements of RPC @ 45 g/d (T2), RPF @ 80 g/d (T3), RPC + RPF as above (T4) and injection Vit-E 500 mg + Se 15 mg fortnightly (T5). The mean fortnightly dry matter intake increased significantly by days 0, 15 and 45 of lactation with higher overall value in T2 than other groups. The blood glucose levels were significantly higher on day of calving and dropped suddenly around day 15 postpartum in all groups. Plasma total cholesterol was significantly lower in T5 and T2, and higher in T4, and it declined significantly from 30 days prepartum till day of calving with lowest values on day 15 postpartum, which increased gradually till day 60 postpartum. The TAG and VLDL concentrations dropped 15-20 fold on day 0 and 15 postpartum over prepartum values, and again increased 5-10 fold on days 30 and 45 postpartum in most groups with higher values in T3, T4 and T5 than in T1 and T2 groups. BHBA levels were significantly increased on day 15 postpartum over day of calving or prepartum values, declined by day 45 postpartum, and were significantly higher in T2 and lower in T5 as compared to other groups. The uterine involution, first estrus postpartum and conception rates were significantly enhanced with all nutrient supplements, and T5 in particular.