Reproductive Performance Of Dairy Cattle Research Articles

Faktor-Faktor yang Mempengaruhi dilakukannya Praktek-Praktek Manajemen Reproduksi Sapi Perah "Suatu penelitian yang bertujuan untuk menentukan prioritas materi penyuluhan bidang manajemen reproduksi sapi perah, kasus di Pennsylvania, USA"

The primary purpose of this research was to provide information for Perm State cooperative Extension personnels in designing extension program in the area of dairy reproductive management. The study focused on factors influencing the use of practices in five areas of reproductive management, including reproductive health, feeding management, calving and post partum management, heat detection, and artificial insemination (AI). Considering that a dairy farm profit is influenced greatly by its reproductive status, these research results could be used as a technical comparison in the efforts to increase the reproductive performance of dairy cattle in Indonesia. Research results identified several reproductive management practices which had not been used by a relatively large proportion of dairy producers. In this respect, Penn State Cooperative Extension personnels may help dairy producers to increase the reproductive efficiency of their herds by emphasizing areas where dairy producers need most help. Further, results of multiple regression analysis revealed eight factors were related significantly to the use of reproductive management practices. Those factors are: (1) dairy producers' knowledge of reproductive management, (2) DHIA (Dairy Herd Improvement Association) membership, (3) the frequency of receiving information from cooperative extension sources, (4) farmers' attitudes towards dairy farming, (5) herd size, (6) years of experience in dairying, (7) frequency of receiving information from feed company personnel, and (8) the frequency of receiving information from farm management consultant.

Major factors influencing the reproductive performance of dairy farms in Mekelle City, Tigray, Ethiopia

The study was conducted from November 2011 to April 2012 with the objective of assessing major factors influencing the reproductive performance of dairy cattle in selected farms of Mekelle city. Thirty two dairy farms; 19 from private, 11 from cooperative and 2 from government were randomly selected. Total number of dairy cattle were 798; of which, 380 were from private farm, 373 were from cooperatives and 45 were from governmental. Data were collected by using questionnaire survey and observational study through regular visit during the study periods with the interval of once per week. According to the collected data from the respondents, 203 (25.44%) Repeat breeder, anestrus, retained fetal membrane, abortion and dystocia were the major reproductive disorders with the prevalence rate of 27.2%, 18.2%, 15.8%, 13.3% and 8.7%, respectively; whereas metritis, uterine prolapse and vaginal prolapse prevalence rate were 6.9%, 5.9% and 3.9%, respectively. According to the data collected from respondents and observational study, there were variations in feeding, watering, housing, hygienic and reproductive management practices. Hence, in addition to reproductive disorders, managemental practices had an effect on the reproductive performance of dairy cattle.

Uterine disease and its effect on subsequent reproductive performance of dairy cattle: a comparison of two cow-side diagnostic methods

The aim of this study was to compare vaginal mucus scoring and ultrasonographic assessment of uterine content as predictors of future reproductive performance of dairy cows. Holstein-Friesian cows (n = 493) from seven commercial dairy farms were enrolled in this study. All cows received one prebreeding examination (PBE) between 21 and 38 days after parturition. During the PBE, vaginal mucus was scored (MS) and the transrectal ultrasonographic examination of the uterus to assess content (UTS) took place. The MS was scored on a scale of 0 to 3 using a Metricheck device and appearance of the uterus on transrectal ultrasound was scored on a scale of 0 to 4 based on the presence and consistency of intraluminal fluid. Other data collected from each cow included the farm ID (F_ID), conception rate to first service, length of breeding window, lactation number, calving month, body condition score (BCS) at calving, BCS loss after calving, BCS at PBE, days in milk at PBE, 305 day milk yield, economic breeding index (EBI), EBI fertility subindex and EBI health subindex. For each cow these parameters were analyzed using univariate Cox proportional hazard model to evaluate the effect of variables on the reproductive performance, measured as positive pregnancy status (PS) at the end of the breeding season. Receiver-operating characteristic analysis of the diagnostic tests compared with each other took place as well. Cows with positive UTS were 7.75 times more likely to have a positive MS as well (P < 0.01). The PS hazard ratios for cows with UTS0, 1, 2, 3, and 4 were 1; 0.84; 0.53; 0.78; 0.28, respectively (P < 0.001). For the cows with MS0, 1, 2, and 3, the PR hazard ratios were 1; 1.02; 0.51; 0.75; respectively (P = 0.01). Conception rate to first service, breeding window, and PS were significantly better for the cows with UTS0, 1 and 2 compared with the cows with UTS3–4 and MS2+3 (68%; 18%, [P = 0.020]; 29; 75 days, [P = 0.001]; 95%; 55%; [P = 0.010], respectively). There was a significant effect of days in milk at PBE in relation to the subsequent PS (P = 0.04). Cows in lactation number 5 or more were less likely (r = 0.69) to get in calf before the end of the breeding season than cows in their first lactation. Cows that calved later in the season were less likely to become pregnant before the end of the breeding season (P < 0.03). Younger cows (lactation <5) and cows with MS and UTS scores of 0 and −1 had significantly better reproductive performance (P < 0.04). Receiver-operating characteristic analysis showed that MS did not always reflect UTS, but cows with positive UTS were 7.75 times more likely to have a positive MS (P < 0.01) and a high UTS had a larger negative effect on time to PS than a high MS (P < 0.05). In conclusion, both prebreeding vaginal mucus evaluation with the Metricheck device and an ultrasound scan of the uterus serve as a good predictor of the subsequent PS. There is overlap between the two systems, but the best predictor for future reproductive outcome of the cow is a combination of both.

Additive genetic, non-additive genetic and permanent environmental effects for female reproductive performance in seasonal calving dairy females

AbstractExcellent reproductive performance (i.e. 365-day calving interval) is paramount to herd profit in seasonal-calving dairy systems. Reproductive targets are currently not being achieved in Irish dairy herds. Furthermore, most research on the genetics of reproductive performance in dairy cattle has focused primarily on lactating cows and relatively few studies have attempted to quantify the genetic contribution to differences in reproductive performance in nulliparae. The objective of the present study was to estimate the contribution of both the additive and non-additive genetic components, as well as the permanent environmental component, to phenotypic variation in the reproductive traits in nulliparous, primiparous and multiparous seasonal-calving dairy females. Reproductive phenotypes were available on up to 202,525 dairy females. Variance components were estimated using (repeatability where appropriate) linear animal mixed models; fixed effects included in the mixed models were contemporary group, parity (where appropriate), breed proportion, inter-breed specific heterosis coefficients and inter-breed specific recombination loss coefficients. Heritability of the reproductive traits ranged from 0.004 (pregnancy rate to first service) to 0.17 (age at first service in nulliparae), while repeatability estimates for the reproductive traits in cows ranged from 0.01 (calving interval) to 0.11 (pregnant in the first 42 days of the breeding season). Breed-specific heterosis regression coefficients suggest that, relative to the parental mean, a first-cross Holstein–Jersey crossbred was almost 7 days younger at first calving, had a 9-day shorter calving interval, a 6 percentage unit greater pregnancy rate in the first 42 days of the breeding season and a 3 percentage unit greater survival rate to next lactation. Heifer calving rate traits were strongly genetically correlated with age at first calving (–0.97 to –0.66) and calving rate in the first 42 days of the calving season for first parity cows (0.77 to 0.56), but genetic correlations with other cow reproductive traits were weak and inconsistent. Calving interval was strongly genetically correlated with the majority of the cow traits; 56%, 40%, and 92% of the genetic variation in calving interval was explained by calving to the first service interval, number of services and pregnant in the first 42 days of the breeding season, respectively. Permanent environmental correlations between the reproductive performance traits were generally moderate to strong. The existence of contributions from non-additive genetic and permanent environmental effects to phenotypic differences among cows suggests the usefulness of such information to rank cows on future expected performance; this was evidenced by a stronger correlation with future reproductive performance for an individual cow index that combined additive genetic, non-additive genetic and permanent environmental effects compared to an index based solely on additive genetic effects (i.e. estimated breeding values).

Effect of Age at First Calving on Productive and Reproductive Performance in Dairy Cattle

This retrospective study evaluated the effect of age at first calving on the productive and reproductive performance in Holstein dairy cattle. Data were collected on 2,297 lactations from 19 dairy farms, including dates of birth, insemination, pregnancy, calving, and lactation and milk production (305-day milk yield at first lactation and lifetime milk yield). Lactation data were grouped based on age at first calving into the early ( 28 months, n = 615) groups. The 305-day milk yield at first lactation was higher (p < 0.005) in the late group (8,461.9 kg) than in the early (8,130.8 kg) and moderate (8,261.9 kg) groups. Lifetime days in milk were shorter (p < 0.01) in the early group (1,045.7) than in the moderate (1,143.1) and late (1,110.7) groups, whereas the lifetime milk yield was higher (p < 0.05) in the moderate group (34,171.8 kg) than in the early group (31,791.6 kg). The second calving interval (days) differed (p < 0.0001) between the early (416.9), moderate (438.9), and late (455.3) groups. The culling rate at the first and second lactations tended to be higher (p = 0.08) in the early group (31.2%) than in the moderate group (26.0%), whereas it was intermediate in the late group (29.3%). In conclusion, dairy heifers aged 24-28 months at first calving showed a higher productive performance through an increased lifetime milk yield and a decreased culling rate.

The effect of subclinical ketosis on activity at estrus and reproductive performance in dairy cattle

Our aims were to investigate the influence of subclinical ketosis (SCK) on physical activity at estrus using a neck accelerometer device and on future reproductive performance. Two hundred three Holstein-Friesian cows were studied on 3dairy farms in Northwest England between September 2013 and March 2014. Seventeen percent (35 of 203) of the enrolled cows were affected with SCK between 7 and 21d in milk, defined as a blood β-hydroxybutyrate concentration of 1.2 to 2.9mmol/L. Time to event analyses and multivariable regression analyses were used to assess the effect of SCK on reproductive performance and activity at estrus. The SCK cows exhibited a lower peak activity (measured as the number of standard deviations above mean activity) and shorter duration in activity clusters associated with first estrus and first insemination postpartum, compared with non-SCK cows. Peak activity and cluster duration associated with the insemination that led to a pregnancy were not different between SCK and non-SCK cows. Calving to first estrus, calving to first insemination, and calving to pregnancy intervals were prolonged in SCK cows. First insemination was 4.3 times (95% confidence interval=1.6 to 15.0) less likely to be successful in SCK cows compared with non-SCK cows. Adjusted mean number of inseminations per pregnancy was 2.8 for SCK cows and 2.0 for non-SCK cows. The current study confirms the long-lasting effects of SCK on reproductive efficiency. Furthermore, it is indicated that physical activity around estrus is reduced by SCK in early lactation, but this negative effect appears to diminish as cows progress through lactation.

The Effect of Intravenous Butaphosphan, B12 and C Vitamins on Metritis, Mastitis Prevalence and Reproductive Performance of Dairy Cattle

AbstractThree groups of Holstein Friesian cows were used to test the effect of two intravenous solutions on metritis, mastitis prevalence and reproductive performance. The first solution containing 3000 mg Butaphosphan (100 mg/ml) and 1.5 mg B12 Vitamin (0.05 mg/ml) was administered to BB12 group in the first 3 days after parturition and the second solution containing 3000 mg Butaphosphan (100 mg/ml), 1.5 mg B12 Vitamin (0.05 mg/ml) and 7 g of C vitamin (0.1 g/ml) was administered to BB12C group in the same period. The control group (C) didn’t receive any intravenous solution. The Tukey-Krammer multiple comparison tests were used to compare the results. The prevalence of clinical metritis, puerperal metritis and clinical mastitis was lower in the BB12C group (p&lt; 0.05), compared to BB12 and C groups. Regarding the prevalence of metritis and mastitis no differences was observed in the BB12 group, compared with the C group (p&gt;0.05). However, no difference was observed in the prevalence of the clinical endometritis (p&gt;0.05) for the all three groups of cows. Also, the BB12C group registered the best calving to first insemination interval and calving to conception interval (p&lt; 0.05). In conclusion, the intravenous cocktail containing Butaphosphan, B12 and C Vitamin can reduce the prevalence of some uterus and udder infection in the first 7 days after parturition in dairy cows.

Risk Factors for Metritis and Its Effect on Productive and Reproductive Performance in Dairy Cattle and Buffaloes

The present study evaluated the risk factors for metritis and effects of metritis on productive and reproductive performance in cattle (crossbred and Zebu) and buffaloes. Milk production and reproduction data of crossbred (n = 2549 lactations), Zebu (n = 1609 lactations), and Murrah buffaloes (n = 1604 lactations), spread over 12 years, were utilized for the study. Overall incidence of metritis was 22.56, 10.32, and 9.66 %, in crossbred cattle, Zebu cattle, and Murrah buffaloes, respectively. Estimated odds ratio (OR) for risk factors of metritis in crossbred cattle were dystocia (OR = 5.39), abortion (OR = 3.64), dead calf (OR = 4.10), retention of fetal membrane (RFM) (OR = 106.90), low calf BW (OR = 1.41), and shorter gestation length (OR = 4.12). In Zebu cattle, dystocia (OR = 3.15), abortion (OR = 2.98), dead calf (OR = 3.62), RFM (OR = 49.33), high calf BW (OR = 2.31), and shorter gestation length (OR = 2.81) were significant risk factors for metritis. Odds of metritis in buffaloes increased significantly (P < 0.05) after dystocia (OR = 6.12), abortion (OR = 11.87), dead calf (OR = 4.37), RFM (OR = 125.42), shorter gestation length (OR = 6.57), calving during summer (OR = 1.92), and lower calf BW (OR = 2.31). Metritis negatively affected milk production in cattle (P < 0.05) but not in buffaloes. Although, metritis had an inconsistent effect on days to first insemination, service period, and number of services/conception, calving interval was consistently extended in affected animals. The study identified abnormal calving, particularly RFM as potential risk factor for metritis which subsequently prolonged calving interval in both cattle and buffaloes. Milk production was negatively affected by metritis in cattle but not in buffaloes.

Invited review: Recommendations for reporting intervention studies on reproductive performance in dairy cattle: Improving design, analysis, and interpretation of research on reproduction

Abundant evidence from the medical, veterinary, and animal science literature demonstrates that there is substantial room for improvement of the clarity, completeness, and accuracy of reporting of intervention studies. More rigorous reporting guidelines are needed to improve the quality of data available for use in comparisons of outcomes (or meta-analyses) of multiple studies. Because of the diversity of factors that affect reproduction and the complexity of interactions between these, a systematic approach is required to design, conduct, and analyze basic and applied studies of dairy cattle reproduction. Greater consistency, clarity, completeness, and correctness of design and reporting will improve the value of each report and allow for greater depth of evaluation in meta-analyses. Each of these benefits will improve understanding and application of current knowledge and better identify questions that require additional modeling or primary research. The proposed guidelines and checklist will aid in the design, conduct, analysis, and reporting of intervention studies. We propose an adaptation of the REFLECT (Reporting Guidelines for Randomized Controlled Trials for Livestock and Food Safety) statement to provide guidelines and a checklist specific to reporting intervention studies in dairy cattle reproduction. Furthermore, we provide recommendations that will assist investigators to produce studies with greater internal and external validity that can more often be included in systematic reviews and global meta-analyses. Such studies will also assist the development of models to describe the physiology of reproduction.

Modulation of post-partum reproductive performance in dairy cows through supplementation of long- or short-chain fatty acids during transition period.

Thirty-six cross-bred cows were used to study the effect of long-chain (flaxseed) or short-chain (butyric acid) fatty acid supplementation on metabolic status, ovarian function and reproduction performance during transition period. Control cows received a routine feed of transition diet, while the cows in two treatment groups were supplemented with either 750-g crushed flaxseed or 250 g butyric acid per cow per day. Ovarian activity was monitored by transrectal ultrasonography on 10th, 20th and 30th days post-partum. Blood samples were collected by jugular venipuncture into heparinized polystyrene tubes; plasma was prepared and stored under -20 °C until analysis. Results indicated that cows in flaxseed group were in positive energy balance as indicated by lower NEFA and Beta hydroxy Butyrate and higher glucose concentrations. Uterine involution was completed well within 30 days post-partum in all the cows in flaxseed fed group compared to 76.9% in butyric acid supplemented and 61.5% in control groups. The size of dominant follicle and corpus luteum was significantly higher (p < 0.05) for flaxseed group compared to control group, which in turn resulted in higher concentrations of plasma progesterone. Cows fed on diets supplemented with flaxseed exhibited post-partum heat earlier and bred sooner (p < 0.05) than control cows. It has been noticed that supplementation of flaxseed and butyric acid enhanced involution of uterus, early resumption of cyclicity and thereby early breeding. However, in view of the encouraging results obtained for flaxseed supplemented group, its organic nature and easier availability at farmer's gate, we concluded that flaxseed can be safely included in transition diet to modulate reproductive performance of dairy cattle.

Evaluation of norgestomet Crestar® on oestrus synchronization and reproductive performance of dairy cows in Algeria

Abstract Objective To evaluate the effectiveness of norgestomet Crestar® for synchronization of oestrus and its effect on pregnancy rate in cows. Methods after a waiting period (∼90 days postpartum), Holstein-Frisian females kept in different dairy farms were inseminated for the detection of estrous behavour ( n =133). Females were allocated randomly to treated ( n =69) or control ( n =64) groups. The treated animals received the Crestar® treatment during 9–10 days. After implant removal, the treated animals were artificially inseminated (AI) for the detection of standing estrous behaviour. Blood samples were collected on Days 0, 21 and 30 after service. Plasma progesterone (P4) and pregnancy-associated glycoprotein (PAG) levels were determinate by radioimmunoassay. Results the study showed a higher rate of heat synchronization in the treated group (94%) compared to the control group (86%). Out of 133 cows inseminated, thirteen (4 treated and 9 control) had a plasma progesterone concentrations higher than 1.0 ng/mL at service. The plasma PAG levels at Day 30 after AI were significantly lower in the treated group (7.13 ± 2.29) compared to the control group (8.37 ± 2.30). Pregnancy rate was 28% (16/57) and 42% (23/54) for treated and untreated group, respectively. There were no significant differences in the pregnancy rates of different parity in both groups. Conclusion The norgestomet Crestar® treatment carried out during 9–10 days did not improve reproductive performance in dairy cattle. However, these data demonstrate that this hormonal protocol can be used to obtain high oestrus cow rates to initiate correct timing of insemination.

Effect of Obstetrical Manipulation on the Survival Rate and Reproductive Performance of Dairy Cattle Following the Successful Correction of Uterine Torsion

乳牛における子宮捻転整復後の産科処置の違いが生存率及び繁殖成績に及ぼす影響を調査した．子宮捻転整復に成功したホルスタイン種乳牛112頭を，胎子娩出状況別に無処置・軽度牽引群（48頭），中・重度牽引群（48頭），帝王切開群（16頭）の3群に分けて成績を比較した．その結果，無処置・軽度牽引群は母牛生存率（1カ月後）97.9％，最終受胎率（1年後）89.4％であった．中・重度牽引群は無処置・軽度牽引群と比較して最終受胎率が67.4％と有意に低下していた．また，帝王切開群は母牛生存率75.0％と有意な低下がみられたが繁殖成績に差は認められなかった．以上より，子宮捻転整復後に重度牽引や産道損傷を伴うことは，その後の繁殖成績を低下させるため，捻転整復後の産科処置の選択が重要である．

Use of herd management programmes to improve the reproductive performance of dairy cattle

There has been a long history of herd health and production management programmes in many dairy industries around the world, but evidence for the efficacy of such programmes is limited. In response to a perceived decline in fertility of dairy cows, a herd reproductive management programme (InCalf) was introduced in New Zealand in 2007. This programme uses a management cycle approach that includes an assessment of the current herd status, identification of areas for improvement, development of a plan, implementation of this plan and finally a review process. The programme uses facilitators who work with farmers either in a one-to-one manner or in a formalised group setting that involves a series of meetings over a 12-month period (the farmer action group). The hypothesis that involvement in a reproductive management programme would improve herd reproductive performance was tested using a herd-level controlled randomised study (the National Herd Fertility Study) involving herds in four geographic regions of New Zealand over 2 years. Within each region, herds were ranked on the basis of the 6-week in-calf rate (i.e. the proportion of the herd pregnant in the first 6 weeks of the seasonal breeding programme) in the year preceding commencement of the study and then randomly assigned to be involved in a farmer action group or left as untreated controls. The key outcome variable of the study was the 6-week in-calf rate. Pregnancy diagnosis was undertaken at 12 weeks after the start of the seasonal breeding programme, which allowed determination of conception dates and hence calculation of the 6-week in-calf rate. Additional measurements including heifer live weight and body condition score (pre-calving and pre-mating) were undertaken to test whether treatment resulted in measurable changes in some of the key determinants of herd reproductive performance. Involvement in the farmer action group of InCalf resulted in a 2 percentage point increase in the 6-week in-calf rate (P=0.05). The following additional observations were made in herds involved in the farmer action group relative to control herds: heifers had live weight closer to target; the pre-mating body condition score of cows was higher; and oestrous detection rates were higher. It was concluded that involvement in this herd reproductive management programme improved reproductive outcomes in this New Zealand study. However, to achieve substantial improvements in herd reproductive performance at the regional or national level a greater response to the programme and a high uptake of such programmes is required, as well as use of other industry-level tools such as genetic management programmes.

Milk fat saturation and reproductive performance in dairy cattle

Unsaturated fatty acids (UFA) cannot be synthesized by mammalian cells due to a lack of desaturase enzymes. Combined with their limited supply to the small intestines, UFA have been proposed as nutraceuticals to ameliorate dairy cow fertility. However, field studies based on a large number of animals are lacking on this subject. Therefore the aim of the present study was to analyze a large dataset containing individual cow fertility records from dairy herds and link fertility key-performance-indicators like conception rate to first insemination (CRFI), days in milk to first insemination (DIMFI) and days in milk to conception (DIMCONC), to the level of UFA in bulk tank samples, the latter being a proxy for the dietary fatty acid profile on these herds. Within the two year study period, information from 15,055 lactations and 35,433 bulk tank milk samples was collected on 90 herds. The multilevel logistic regression model used, revealed a decreased CRFI on herds with a higher bulk tank UFA level. The decrease in CRFI was larger for higher producing herds. Increased bulk tank UFA was furthermore associated with higher DIMFI which, together with the lower CRFI, subsequently increased DIMCONC. Interestingly, higher variability in UFA, expressed by an increased coefficient of variation, was associated with an increased CRFI and decreased DIMFI and DIMCONC. In conclusion, the present study demonstrates that increasing the UFA content of milk should not be a goal as such when supplementing UFA to dairy cows as higher bulk tank UFA are associated with worsened fertility results.

Behavioral and physiological effects of a short-term feed restriction in lactating dairy cattle with different body condition scores at calving

Body condition score (BCS) around calving, and the typical BCS loss for up to 100 d after parturition, is associated with both production and reproductive performance of dairy cattle. In addition, there is public concern that thin cows may have impaired welfare, particularly in early lactation where feed demand exceeds pasture growth, and a lag exists between peak milk energy requirements and intake. The aim of this experiment was to determine how BCS at calving influences behavioral and physiological responses to a short-term feed restriction at 47 DIM. Body condition score (on a 10-point scale) at calving was manipulated by modifying the diets in the previous lactation of healthy dairy cattle to generate 3 treatment groups: low BCS (3.4; n=17), medium BCS (4.6; n=18), or high BCS (5.4; n=20). Cows were tested in 4 groups for 8 consecutive days; testing consisted of different levels of feed allocation (d 1 and 2: 100%; d 3 and 4: 75%; d 5: 50%; d 6 to 8: 125%), where 100% was 15kg of DM/cow per day. All BCS groups had similar and marked behavioral and physiological responses to feed restriction. For example, they increased vocalization, time spent eating silage and grazing, aggressive behavior, and fat metabolism (as measured by concentrations of β–hydroxybutyrate and nonesterified fatty acids), and reduced milk production. Body condition affected some of these responses. Fewer cows with low BCS engaged in aggressive interactions in a feed competition test (trough filled with silage that could be consumed in 15 min) on the first day of feed restriction (low: 32%; medium: 74%; high: 64%; standard error of difference=15.4%). High BCS cows had greater concentrations of β–hydroxybutyrate and nonesterified fatty acids throughout the experimental period, which suggests more fat mobilization; however, plasma leptin and fecal glucocorticosteroid metabolite concentrations were unaffected by BCS. Whereas cows demonstrated marked responses to feed restriction, the results suggest that a BCS of 3.4, 4.6, or 5.4 in healthy cows at calving does not overwhelmingly influence this response at 47 DIM.

Therapy of bovine endometritis with prostaglandin F2α: A meta-analysis

The objective of the conducted meta-analysis was to assess the efficacy of the treatment of bovine endometritis with PGF2α by statistical means. Postpartum uterine infections have a high prevalence and a very negative effect on reproductive performance in dairy cattle. Because of a wide discordance between research results, a meta-analysis of the efficacy of the treatment of bovine endometritis with PGF2α was conducted. A comprehensive literature search was performed using online databases to reveal a total of 2,307 references. In addition, 5 articles were retrieved by reviewing citations. After applying specific exclusion criteria and evaluating specific evidence parameters, 5 publications, comprising 6 trials, were eligible for being analyzed by means of meta-analysis. Data for each trial were extracted and analyzed using meta-analysis software Review Manager (version 5.1; The Nordic Cochrane Centre, Copenhagen, Denmark). Estimated effect sizes of PGF2α were calculated on calving to first service and calving to conception interval. Prostaglandin F2α treatment of cows with chronic endometritis had a negative effect on both reproductive performance parameters. Heterogeneity was substantial for calving to first service and calving to conception interval [I2 (measure of variation beyond chance)=100 and 87%, respectively]; therefore, random-effects models were used. Sensitivity analysis as well as subgroup analysis showed that the performance of randomization was influential in modifying effect size of PGF2α treatment. The funnel plot illustrated a publication bias toward smaller studies that reported a prolonged calving to conception interval after a PGF2α treatment. We conclude that the investigation of this subject by means of meta-analysis did not reveal an improvement of reproductive performance of cows with endometritis after treatment with PGF2α. Furthermore, there is a shortage of comparable high quality studies investigating reproductive performance after PGF2α treatment of cows with chronic endometritis.

Melatonin Treatment at Dry‐off Improves Reproductive Performance Postpartum in High‐producing Dairy Cows under Heat Stress Conditions

The aim of this study was to determine the effect of melatonin treatment during the early dry-off period on subsequent reproductive performance and milk production in high-producing dairy cows under heat stress conditions. In experiment I, addressing the pharmacokinetics of melatonin treatment in lactating dairy cows, doses of untreated, 3, 6, 9 or 12 implants/animal (18-mg melatonin each implant) were given as subcutaneous implants on gestation day 120-20 multiparous lactating dairy cows (four cows/dose group). Experiment II was performed during the warm season on 25 heifers and 114 high milk-producing Holstein-Friesian cows. Animals were randomly assigned to a control (C) or melatonin group (M). Animals in the M group received nine implants (heifers) or 12 (cows) of melatonin on day 220 of gestation. In experiment I, cows in the 12 implants group showed a higher maximum melatonin concentration (Cmax ) and area under the concentration curve from treatment day 0 to day 49 (AUC0-49d ) than those in the remaining groups, among which there were no significant differences in this variable. In experiment II, the likelihood of repeat breeding syndrome (<3 vs ≥4 AIs per cow) and pregnancy loss (first trimester) were 0.36 and 0.19 times lower in treated than control animals, respectively. Plasma prolactin levels decreased significantly (p=0.01) after melatonin treatment and recovered during the postpartum compared to control cows. No significant effects on milk production were observed in the subsequent lactation. Significant differences in days open between groups (means 123±71.9 and 103±43, respectively, for C and M; p=0.02) were registered. In conclusion, melatonin treatment in the early dry-off period improves the reproductive performance of dairy cattle, reducing the number of days open, repeat breeding syndrome and pregnancy loss.

Genetic evaluation of reproductive performance in Canadian dairy cattle

A new genetic evaluation system for the reproductive performance of dairy cattle has been developed in Canada. The evaluation system includes all traits related to reproductive performance, namely age at first service as a heifer trait, interval from calving to first service for cows and 7 traits each for both heifers and cows (56-days non return rate, interval from first service to conception, number of services to conception, gestation length, direct and maternal calving ease, direct and maternal calf survival and direct and maternal calf size). The model of analysis is a 16-trait animal model with different fixed effects according to the analyzed trait. Two indices for daughter fertility and calving performance have been developed. The impact of including the two indices in the national selection index was assessed.

Effect of supplementation with different fat sources on the mechanisms involved in reproductive performance in lactating dairy cattle

Supplementary fat positively influences reproductive performance in dairy cattle, although the mechanisms involved are not clearly defined. Our objective was to determine the effects of four different fat supplements on follicle development, plasma steroid hormone concentrations and prostaglandin (PG) synthesis in lactating dairy cattle. Forty-eight early lactation Holstein-Friesian cows (21 primiparous, 27 multiparous) were used in a completely randomized block design. Cows were fed the same basal TMR diet and received one of four fat supplements: (i) palmitic acid (18:0 fatty acid; Control), (ii) flaxseed (rich in 18:3 n-3 fatty acid; Flax), (iii) conjugated linoleic acid (a mixture of cis-9, trans-11 and trans-10, cis-12 isomers; CLA), and (iv) fish oil (rich in 20:5 and 22:6 n-3 fatty acids; FO). All lipid supplements were formulated to be isolipidic; palmitic acid was added as necessary to provide a total lipid supplement intake of 500 g/day. Cows were synchronized to be in estrus on Day 15 of dietary treatment. All antral follicles were counted, and dominant follicles, subordinate follicles and corpora lutea were measured daily via transrectal ovarian ultrasonography for one complete estrous cycle. Blood samples were collected daily, and selected samples were analyzed for progesterone, estradiol, insulin-like growth factor-1, insulin, cholesterol and non-esterified fatty acids. Estrus was synchronized a second time, and liver and endometrial biopsies were collected on Day 7 of the estrous cycle. Gene expression was evaluated for a number of genes involved in prostaglandin synthesis (endometrium) and fatty acid uptake and utilization (liver). Fat supplementation had little effect on follicle development. Cows receiving supplementary n-3 fatty acids had lesser plasma progesterone (P4) and smaller corpora lutea than cows receiving the CLA or Control supplements. Effects of fat supplementation on the endometrial expression of genes involved in PG synthesis were minor. Hepatic expression of SREBF1, ASCL1 and FABP1 was reduced by FO supplementation. Reduced plasma P4 in n-3 supplemented cows may lead to a suboptimal uterine environment for embryo development and hence reduced fertility compared to cows receiving the control or CLA supplements.

Evaluation of Reproductive Tract Infection During Early Post‐Partum Period and Its Relationship with Subsequent Reproductive Performance in High Milk Producing Dairy Cows

Clinically normal Holstein-Friesian cows (n = 43) were used to establish a relationship between the evaluations of the uterine condition by vaginoscopy, Metricheck, endometrial cytology (EC) and ultrasonography (US) during post-partum period (pp), and subsequent reproductive performance. The uterine status of the selected cows was evaluated by EC, Metricheck, US and vaginoscopy on a weekly basis from the third week (W3) to the seventh week (W7) pp. The animals were bred after a voluntary waiting period of 45-60 days pp and diagnosed for pregnancy status at 45 days after breeding by US. First service conception rate (FSCR) of bred animals was 32.6% (14/43). There was no significant difference in polymorphonuclear leucocyte percentage between conceived and non-conceived cows during different weeks post-partum. First service conception rate in animals with normal vaginal discharge as detected by Metricheck was significantly low when compared to those of abnormal discharge during W3 (2.3% vs 30.3%; p < 0.001) and W4 (4.7% vs 29.7%; p < 0.01) post-partum. Using US, the number of pregnant cows having fluid in uterus (FIU) during W6 (p < 0.01) and W7 (p < 0.001) post-partum was significantly lower (2/34, 4.7% and 1/43, 2.3%, respectively) than those that had no FIU (12/43, 27.9% and 13/43, 30.3%, respectively). Using vaginoscopy, FSCR in animals having abnormal discharge was significantly (p < 0.01) low when compared to that of normal discharge (2.4% vs 30.2%) during W5 and W6 post-partum. In conclusion, Metricheck during W3 and W4 and detection of FIU by US and vaginoscopy during W6 and W7 pp can be used as good predictive tools to anticipate the future reproductive performance of dairy cattle.