Calving To Conception Interval Research Articles

Genetic parameters for milk yield and reproductive traits in Honduran Holstein cattle.

The aim of this study was to estimate the (co)variance components and genetic parameters for milk yield adjusted to 305d (MY305), calving-to-conception interval (CCI), number of services per conception (NSC) and calving interval (CI) of Honduran Holstein cows, by fitting a bivariate animal model using Maximum Restricted Likelihood procedures. Model included the fixed effects of calving number, the contemporary calving group (farm-season-year of calving and the cow age as covariate). The estimated means and standard deviations for MY, CCI, NSC and CI were, 5098.60 ± 1564.32kg, 168.27 ± 104.71 days, 2.46 ± 1.69 services, and 448.73 ± 109.16 days, respectively; and their estimated heritabilities were 0.21 ± 0.05, 0.03 ± 0.028, 0.02 ± 0.024 and 0.06 ± 0.04, respectively. The genetic correlations between MY305 and CCI, NSC and CI were positive and antagonist, with values of 0.64 ± 0.52, 0.99 ± 0.56, and 0.32 ± 0.24 respectively. Even though moderate to low heritability was estimated for MY305, systematic selection for milk yield, with a reduction in reproductive efficiency, if considered as the only selection criterion is important to be considered. By including reproductive traits and considering permanent environment effects into the breeding program, might yield a slow, but constant and permanent improvement over time.

Comparative productive performance of cows born through embryo transfer, artificial insemination and natural mating in dairy and dual-purpose herds raised in tropical conditions.

A populational, observational and longitudinal-retrospective study with records of 28 dairy specialized and dual-purpose farms, was carried out to compare the productive performance of cows born by embryo transfer (ET), artificial insemination (AI), and natural mating (NM), using the database of Centro Regional de Investigación para la Producción Animal Sostenible (CRIPAS) of cattle herds in Costa Rica. Herds (system × altitude), conception method (ET, AI and NM), genetic background (DSpB: specialized dairy breeds (Bos taurus) and crosses, GYR×HOL: Gyr × Holstein Crossbred and DSpB×BI: crosses between dairy breeds and Bos indicus), year of birth (or at calving), lactation number and days in milk were evaluated for the productive parameters age at first calving (AFC), calving to conception interval (CCI) and lactation milk yield (LMY) using a GLIMMIX procedure on SAS. The AFC, CCI, and LMY were affected (P<0.0001) by all factors considered in each parameter. ET has lower (P<0.0001) AFC in months (33.1) than AI (35.2) and NM (36.44). NM had lower (P=0.004) CCI (110 d) than AI or ET (121 d) values which were similar (P>0.05). The higher LMY (P<0.0001) was observed in ET (4140 kg), compared to AI (3706 kg) and NM (3595 kg). There was no difference between AI and NM. In conclusion, the method of conception in calves affected their future reproduction and production during puberty, postpartum, and lactation. The effects on management decisions will require a rigorous economical study to discern whether ET would be a cost-effective alternative to AI or NM.

Exploring the role of milk yield in the first week of lactation on the association between hyperketonemia and reproductive performance in dairy cattle

The objective of this retrospective cohort study was to investigate whether the association of hyperketonemia (HYK) with reproductive performance differs based on milk production during the first week of lactation (wk 1). Data between calving and 150 d in milk (DIM) from 2,091 Holstein dairy cows from 5 commercial dairy herds in Minnesota were collected. The concentration of β-hydroxybutyrate (BHB) was measured twice between 3 and 10 DIM in whole blood to diagnose HYK (defined as BHB ≥1.2 mmol/L). The average wk 1 milk yield was classified into 3 levels (low = lower 25th percentile; mid = 25th to 75th percentile; high = upper 75th percentile) according to parity and herd. Log-binomial regression, Cox-proportional hazard regression, and linear regression models were used to investigate the association of HYK with pregnancy to first insemination, pregnancy by 150 DIM, and calving-to-conception interval (CCI) between groups, respectively. To describe the differences in these estimates between each wk 1 milk yield level, an interaction term of HYK and stratified levels of wk 1 milk yield was added. The incidence of HYK between 3 to 10 DIM was 14.2% (4.6% in primiparous cows and 19.4% in multiparous cows). In the study population, the effect of HYK on reproduction was greater in cows with low milk yield. Among cows with low milk yield levels, HYK was associated with lower risk of pregnancy to first insemination [risk ratio = 0.62; 95% confidence interval (CI): 0.39–0.98], lower risk of pregnancy up to 150 DIM (hazard ratio = 0.70; 95% CI: 0.51–0.96), and extended days of CCI (mean difference = 13.0; 95% CI: 5.1–20.9). In contrast, among cows with mid and high wk 1 milk yield levels, hyperketonemic (HYK+) cows had a similar reproductive performance to non-HYK (HYK−) cows. Our results suggest that early-lactation milk yield plays a role in the association of hyperketonemia with reproductive performance. These results merit further investigation to determine the role that early milk yield has in the association of hyperketonemia with health and productivity outcomes.

Bovine viral diarrhea virus (BVDV) infection: Effect on reproductive performance and milk yield in dairy herds

The impact of an outbreak of bovine viral diarrhea (BVD) on reproductive performance and milk production was investigated in 28 Spanish dairy herds using an observational study design. Mean calving to conception interval (CCI), mean number of inseminations per conception (AI/P) and mean daily milk yield were recorded from herds affected by outbreaks. Infection was confirmed by evidence of viral transmission to young stock (heifers 9–24 months) and persistently infected animals, after previous BVD-free status. Fifteen herds did not use vaccines (G1) whereas the remaining 13 received modified live BVD virus (BVDV) vaccines (G2). In G1 herds, a significant increase in CCI (13.8 days; 95% CI, 0.4–27.3 days; P = 0.050) was observed during the BVD outbreak compared to the year before the outbreak. In G2 herds, there was a not a significant increase in CCI (3.0 days; 95% CI, −1.2–7.2 days; P = 0.558). Changes in AI/P between periods were not significant in any of the herds. In G1 herds, there was an increase of 0.09 units (P > 0.05) during the outbreak, whereas in G2 herds, AI/P decreased 0.08 units (P > 0.05). Compared to milk production in the year before the BVD outbreak, there was no significant change in G1 herds throughout the study period (P > 0.05), but there were significant increases in G2 herds over the study period (P1–P2, 1.4 kg/day increase, P = 0.019; P1–P3, 2.0 kg/day increase, P = 0.007). These results indicate that BVDV infection affected reproductive performance, which is critical in maintaining dairy herd profitability.

Early postpartum treatment with carprofen in a dairy herd with high incidence of clinical metritis – a case study

ABSTRACT This study evaluated the early treatment with carprofen over the incidence of clinical metritis (CM) and subsequent reproductive parameters on a commercial dairy farm without health interventions for this disease. Late-gestation pluriparous cows (n = 62) were enrolled at the beginning of the close-up period and randomly assigned to treatments at parturition. Cows received either no treatment (control) or subcutaneous carprofen (1.4 mg/kg of BW) 12–48 h postpartum. Clinical metritis diagnoses were performed weekly starting on days 3–21 postpartum. Reproductive data included conception rate at first service (CRFS), pregnancy rate (PR), calving to first service interval (CFSI), calving to conception interval (CCI) and services per conception (SC). Cows with CM had the CCI increased by 32 days (P = 0.035), the SC by 0.92 (P = 0.048) and a higher risk of non-pregnancy (HR = 0.48, 95% CI = 0.25–0.93, P = 0.03) compared to healthy animals. Carprofen treatment decreased the incidence of CM by 29.5 percent points (P = 0.03), decreasing the risk of developing CM by 3.4 times (95% CI = 1.07 – 10.66, P = 0.04), and shorted the median time for 50% of cows to become pregnant at first service after day 60 by 9 days (P = 0.03), but did not affect any other reproductive performance parameter evaluated. Clinical metritis had a marked effect on reproductive performance. However, the use of carprofen during the early postpartum improved uterine health and the fertility to the first service.

Prevalence of Subclinical Mastitis and its Effects on Reproductive Performance in Dairy Cows during the Postpartum Period in Gasabo District, Rwanda

Mastitis is one of the most important diseases affecting production and reproductive efficiency of dairy cows. The objective of this study was to estimate the prevalence of subclinical mastitis (SCMA) and its effects on reproductive performance in postpartum dairy cows. In a cross-sectional survey, sample cows (n = 200) within their 10-40 days in milk from smallholder farms (n = 159) were selected and tested for SCMA using California Mastitis Test. They were classified into two groups: cows with SCMA (SCMA group, n = 101) and cows without SCMA (WSCMA group, n = 99). Reproductive performance including calving-to-first-oestrus interval (CFOI), calving-to-first service interval (CFSI), calving-to-conception interval (CCI), cows that remained non-pregnant, postpartum anoestrus, and total number of services per conception were recorded for 150 days in milk. The overall prevalence of SCMA recorded was 50.5%. The mean number of days for CFOI was significantly longer (p

Associations between On-farm Welfare, Milk Production, and Reproductive Performance in Dairy Herds in Northwestern Spain

ABSTRACT This study was conducted to evaluate the relationship between on-farm welfare, milk production, and reproductive performance in dairy herds in northwestern Spain. Data on the welfare status from 31 herds were collected using the Welfare Quality® protocol. Linear regression was applied to assess associations between WQ criteria/principle scores on farm average 305-d milk production and calving to conception interval (CCI). Results indicated that milk production was associated with the absence of prolonged hunger criterion (average increase of 22.33kg per unit score). Each one unit increase in the score for good feeding was also associated with a26.49kg increase in milk production. A10 unit increase in the scores for the absence of pain (by management procedures), expression of social behaviors, and absence of injuries was associated with reductions in CCI by 1.77, 0.8, and 0.29 days. CCI also decreased by 1.08 and 0.53 days when the principles of good health and appropriate behavior increased by 10 units. This study points out associations which can help encourage the dairy cattle sector to adopt practices that promote animal welfare.

The Effect of Abnormal Reproductive Tract Discharge on the Calving to Conception Interval of Dairy Cows.

Prolonged calving-to-conception interval (CCI) can increase economic loss in cattle. We investigated the effect of post-calving abnormal reproductive tract discharge (ARTD) on CCI in dairy cows and quantified the relationship of ARTD and associated risk factors with CCI. The source population was dairy cows that calved in the study period on three pasture-based, year-round calving farms in the Riverina, NSW, Australia. Farm records and records from veterinarians' visits were analyzed. ARTD was defined as the presence of reproductive tract discharge according to the following classification: per vaginum purulent discharge ≥21 days post-calving or mucopurulent discharge >26 days post-calving. The incidence of ARTD was calculated. A Kaplan-Meier survivor function was used to estimate median time to conception post-calving dependent on the presence or absence of ARTD. Mixed effects Cox-proportional hazard models were used to estimate the direct and indirect effects of ARTD, and other potential risk factors on CCI such as body condition score (BCS), ambient temperature, and milk yield. Model structures were guided by a directed acyclic graph of potential risk factors for ARTD. The incidence of ARTD in lactations was 16% (95% CI 13.8–18.5%) and did not differ significantly between the three farms (P > 0.05). The median CCI was 176 and 118 days for lactations with and without ARTD, respectively (P < 0.01). The rate of pregnancy following calving in cows with ARTD was significantly decreased relative to the rate of pregnancy in cows without (total effect hazard ratio = 0.62, se = 0.18, P = 0.01). High peak milk yield (>32 L) and parity >2 also significantly extended CCI. We did not observe an effect of BCS or ambient temperature on CCI. The incidence of ARTD in the current study was consistent with clinical endometritis (considered a major source of ARTD) reported in other studies. In contrast—and despite regular veterinary assessment and treatment of on the farms in this study—ARTD extended CCI. Evaluation of the economic impact of ARTD on dairy farms in this region is warranted, and methods to identify high risk cows and develop effective interventions are required.

Association of polymorphisms in the IGF-I, GHR and STAT5A genes with serum IGF-I concentration and reproductive performance of Holstein dairy cows

This study was conducted to evaluate associations of polymorphisms in the genes for the growth hormone receptor (GHR), insulin-like growth factor I (IGF-I) and signal transducer and activator of transcription 5A (STAT5A) with serum concentrations of IGF-I, reproductive performance and milk production of postpartum Holstein dairy cows. Days from calving to first ovulation (DTO) and calving to conception interval (CCI) were evaluated in 95 Holstein cows. Serum concentrations of IGF-I and β-hydroxybutyrate (BHBA) were quantified in samples collected in sequential blood collections. Genotyping of the IGF-I and STAT5A genes was performed. The IGF-I polymorphism distribution was 35.9% CC, 46.1% CT and 18% TT. The IGF-I concentrations in circulation were greater in cows of the TT compared with both the CT and CC groups (P < 0.05). Genotype had a linear association (P < 0.05) with DTO and CCI, which were less for cows of the TT group. There was no association of STAT5A BstEII on serum IGF-I or reproductive variables (P> 0.05). When combining the GHR AluI T allele, obtained in a previous study, and the IGF-I SnaBI T allele from the current study, for the same cows, there were additive associations of both with serum IGF-I, BHBA, number of services per conception, DTO and CCI (P < 0.05). Thus, the IGF-1 SnaBI TT appears to be associated with fewer DTO and lesser CCI of lactating dairy cows and had an additive association with the GHR AluI T allele on indicators for improvement of fertility.

Negative effects of occurrence of clinical mastitis from calving to end of the voluntary waiting period on reproduction in Holstein cows

The objective was to evaluate the effects of clinical mastitis (CM) on reproductive performance in high-milk?producing cows before the service period. The data of Holstein Friesian cows (n = 550) in a commercial farm was retrospectively evaluated. The diagnosis of CM was made by the presence of visible abnormalities in milk or symptoms of inflammation of one or more of the quarters. Cows were checked to detect CM prior to each milking. Calving to first service interval (CFSI), calving to conception interval (CCI), and services per conception (SC) were evaluated as reproductive parameters. Calving to first service interval (83.68 ± 3.18 vs. 74.57 ± 1.08; P < 0.05) and CCI (168.48 ± 8.59 vs. 132.86 ± 3.44; P < 0.001) were prolonged by 11.77% and 26.81%, respectively, and the number of SC (3.16 ± 0.21 vs. 2.42 ± 0.09; P < 0.001) was increased by 30.58% in cows experiencing CM. The culling candidate rate in nonpregnant cows was higher in the mastitis group (4.35%; 6/132) than in the healthy group (0.48%; 2/418). Calving season, time period of CM, and lactation number were not associated with the negative effects of mastitis in reproductive performance (P > 0.05). In conclusion, CM in early lactation has an adverse impact on reproductive performance in high-milk?producing dairy cows. The negative effects of CM on CFSI, CCI, and SC were not interrelated with calving season, the timing of CM, or parity.

Short communication: Meta-analysis on therapy of bovine endometritis with prostaglandin F2α—An update

The objective of the study was to update a prior meta-analysis on the efficacy of the treatment of bovine endometritis with PGF2α. Clinical endometritis in cattle is defined as the presence of a purulent or mucopurulent vaginal discharge after 20 or 26 d, respectively, postpartum. Although the prevalence and impact of this disease are well known, the questions of whether and how to treat endometritis are still controversially discussed. Hence, to ensure timeliness of scientific results, we updated an existing meta-analysis published in 2013 that showed no treatment effect of PGF2α in cases of bovine endometritis. As in the prior meta-analysis, a comprehensive literature search was conducted. After applying specific inclusion and exclusion criteria, 3 trials remained that could be added to the 6 trials in the initial meta-analysis. Data for each trial were analyzed using the meta-analysis software Review Manager (version 5.3; The Nordic Cochrane Centre, Copenhagen, Denmark). Estimated effect sizes of PGF2α were calculated on calving to first service interval (CFSI) and calving to conception interval (CCI). As revealed by the initial meta-analysis, PGF2α treatment still had no effect on both reproductive parameters. Heterogeneity remained substantial for CFSI and CCI and even increased for CCI compared with the initial meta-analysis. Subgroup analysis, however, did not reveal a source of heterogeneity. In updating the meta-analysis, publication bias for trials reporting CCI became even more pronounced, suggesting that studies with higher standard error (i.e., usually smaller studies) that reported a prolonging effect on CCI after a PGF2α treatment were less likely to be published. Finally, although the number of trials published on the chosen topic and their comparability are still limited, this update of our meta-analysis now provides results that are based on approximately twice the number of included cows. The overall outcome, however, has not substantially changed and a positive effect of a PGF2α treatment in case of clinical endometritis could not be shown. Therefore, we do not recommend a treatment of bovine endometritis with PGF2α as a means to improve reproductive performance.

Reproduction performance and blood biochemical parameters in dairy cows: Relationship with oxidative stress status.

Background and Aim:During the last decades, reproduction performances declined dramatically worldwide, but little is known concerning the involvement of oxidative stress as a causative factor. Oxidative stress may act at different levels, with negative impacts on cell membrane integrity and other active molecules with potential subsequent effects on reproduction. The aim of the current study was to investigate the oxidative stress status in cows according to their reproductive performances.Materials and Methods:Peripheral blood concentration of two oxidative stress biomarkers, glutathione S-transferase (GST) and malondialdehyde (MDA), and other biochemical parameters (glucose, total lipids, cholesterol, triglycerides, albumin, total proteins, calcium, urea, creatinine, direct bilirubin, alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase) were determined in 40 healthy cows. Body condition score (BCS), calving to first service interval (FSI), calving to conception interval (CCI), and the number of service per conception (SPC) were simultaneously recorded for each cow.Results:Concerning FSI, three groups were established: Group 1 (from 44 to 60 days), Group 2 (from 60 to 70 days), and Group 3 (from 70 to 80 days). For CCI, two groups were considered: Group 1 (<110 days) and Group 2 (>110 days). MDA showed significant high values only in cows with the lowest BCS (1.5) compared to cows with BCS note of 2.5 and 3.5. No significant difference was observed in cows oxidative stress status (MDA and GST) according to reproductive performances (FSI, CCI, and SPC) in all studied groups.Conclusion:The results revealed relatively altered oxidative stress status in cows with abnormal reproductive performances; however, no significant difference was recorded whatever the considered reproductive parameter.

Temporal effect of maternal heat stress during gestation on the fertility and anti-Müllerian hormone concentration of offspring in bovine

Ovarian reserve has been suggested as an important contributing factor of reproductive success in bovine. Size of ovarian reserve is determined during fetal period and it could be altered by environmental factors, with which the dam is exposed. Maternal heat stress could impair placental function and fetal development; however, there is limited information on the impact of prenatal heat stress on fertility and ovarian reserve in the offspring. Therefore, a retrospective study was conducted, in which fertility parameters and AMH concentration, as a reliable marker of ovarian reserve in bovine, were studied in the offspring of dams that had been exposed to heat stress during the first (FTE), second (STE) or third (TTE) trimester of gestation and the offspring of dams unexposed to heat stress (US). Additionally, postpartum exposure of offspring with heat stress was considered in the model to adjust the statistical analysis in this regard. Days to first service (DFS) and calving to conception interval (CCI) were prolonged in exposed than unexposed cows (P < 0.05). Days to first service and CCI were also longer in STE compared with FTE cows (P < 0.05). First service conception rate was lower in TTE than UN cows (P < 0.05). The proportion of repeat breeders was higher in exposed compared with unexposed cows (P < 0.05). Service per conception was higher in STE and TTE than UN cows (P < 0.05). Culling rate between different periods of lactation was also higher in exposed than unexposed cows (P < 0.05). Finally, AMH concentration was lower in STE and TTE than UN cows (P < 0.05); moreover, it was lower in STE compared with FTE cows (P < 0.05). In conclusion, the present study revealed detrimental effects of maternal heat stress on fertility, productive longevity and ovarian reserve in the offspring. In this context, the second and third trimesters appeared to be more critical periods.

Major Reproductive Disorder and Performances of Small Holder Dairy Farms in and around Fitche Town, North Shoa Zone of Oromia Regional State, Central Ethiopia

A study was conducted to identify and estimate the prevalence rate of reproductive disorder and to assess the possible risk factors and reproductive performances of smallholder dairy cattle in and around Fitche town from December 2013 to June 2014. Eighty one dairy farms (average herd size=4.8) were visited and data on reproductive performance indicator, cow attributes, type of mating, body condition score and general farm management were collected. The overall mean value for Calving to Conception Interval (CCI) (n=66) and Duration After Last Calving (DALC) (n=56) for pregnant and non-pregnant cattle were 169 and 264 days respectively. The least squares mean CCI was higher (p Keywords: Smallholder Dairy Farms; Reproductive Performance; Fitche; Reproductive Disorder

Efecto de la edad al primer parto sobre parámetros reproductivos en la primera lactancia de vacas Holstein y Jersey de Costa Rica

Se realizó un estudio retrospectivo en 28 367 animales raza Jersey puro y 46 029 Holstein puras, de lecherías especializadas de distintas zonas ecológicas de Costa Rica, en el periodo comprendido entre los años 2000 y 2010, con el fin de cuantificar el efecto provocado por la edad al primer parto (EPP) sobre los parámetros reproductivos durante la primera lactancia. Se incluyeron los datos de vacas, registrados en el programa VAMPP Bovino 3.0, en el Centro Regional de Informática para la Producción Animal Sostenible (CRIPAS), de la Escuela de Medicina Veterinaria de la Universidad Nacional de Costa Rica. Los datos fueron analizados por medio de estadística descriptiva y un modelo lineal mixto. Hubo efecto significativo de la EPP sobre el intervalo parto concepción (IPC) en la raza Holstein (P&amp;lt;0.0001), con -13 y -6 días para las hembras con EPP &amp;lt;26 meses y EPP 26-33meses, respectivamente. El IPC no se vio afectado, significativamente, por la EPP en la raza Jersey (P=0.25). Asimismo, los servicios por concepción (SPC) correspondieron a 1.44 (D.E. 0.83/IC95%: 1.44 – 1.44) para vacas Holstein y 1.48 (D.E. 0.93/IC95%: 1.46 – 1.49) para Jersey. Este parámetro se vio influenciado significativamente por la EPP en ambas razas (P&amp;lt;0.0001); en donde se presentaron 1.1 y 0.6menos SPC aquellos animales con EPP baja y media, en comparación a los de alta EPP, en la raza Holstein y Jersey respectivamente. De ese modo, el incremento en la EPP, ajustada por variables ambientales, de manejo e intrínsecas de la vaca, tuvo efecto negativo sobre el IPC de la primera lactancia de las vacas Holstein, pero no en Jersey; del mismo modo, hubo un efecto negativo de la EPP sobre los SPC en ambas razas.

Prävalenz von Lahmheiten unterschiedlichen Grades in der Frühlaktation von Milchkühen und deren Einfluss auf Fruchtbarkeitsparameter

To examine the impact of different degrees of lameness on the fertility of dairy cows. Seven dairy herds housed in free stall barns with cubicles were visited at 4-week intervals and all cows were examined for locomotion characteristics using a locomotion scoring system. The cows received scores from 1 (normal gait) to 5 (severely lame). During the study period of 18months, 893 cows in the first month of lactation and 944 cows in the second, third and fourth months of lactation were evaluated. Reproductive measures between non-lame cows (score1), mild lame cows (score2) and cows with clear lameness (score≥3) were compared. Independent of parity and herd effects, cows with scores ≥3 in the first month of lactation displayed a 6days longer calving to first service interval (CFSI) (86.2±35.6 vs. 80.2±34.1 days; p=0.002) and a 16days longer calving to conception interval (CCI) (119.7±51.4 vs. 103.8±55.5 days; p=0.048) than non-lame cows. Additionally, the risk for non-conception was significantly higher in cows suffering from lameness in the first month of lactation (odds ratio: 2.1, 95% confidence interval: 1.095, 4.040; p=0.026). Cows affected by mild lameness in the third month of lactation had a 4 days longer CFSI (84.7± 35.6 vs. 80.1±30.5 days; p=0.026) and a 18 days longer CCI (120.1±55.4 vs. 102.3±47.6 days; p=0.016) than non-lame cows, while the CSFI in distinct lame cows was extended by 7 days compared to non-lame cows (87.2±34.9 vs. 80.1±30.5 days; p=0.002). Cows with the score1 in the first month and score3 in the third month of lactation showed the longest CSFI (94.3±33.9 vs. 76.5± 16.0 days in non-lame cows; p=0.046). This study suggests that both distinct and mild lameness in early lactation lead to a decline in reproduction in dairy herds. A regular determination of the lameness prevalence in dairy herds and optimizing claw health management, including early treatment of lame cows, will enhance animal welfare and reproduction efficiency.

Effects of diagnostic low-volume uterine lavage shortly before first service on reproductive performance, culling and milk production

The objective was to evaluate if uterine sampling by low-volume uterine lavage, done shortly before the end of the voluntary waiting period, affected reproductive performance, milk production, or culling. Approximately 20 cows (40 and 60 d postpartum) were sampled in each of 38 herds (total, 752 cows), whereas all remaining cows concurrently between 40 and 60 d were a non-sampled reference cohort (n = 2,252 cows). There was an interaction between parity and sampling for first-service conception, calving to conception interval, and milk production. When stratified by parity, there was a tendency for impaired reproductive performance in sampled primiparous cows compared with non-sampled primiparous cows (Odds Ratio for pregnancy to first-service = 0.78 (95% C.I. 0.58–1.04). The Hazard Ratio for pregnancy in sampled primiparous cows was 0.89 (95% C.I. 0.77–1.04) compared to non-sampled primiparous cows. Sampling did not affect first-service conception rate (Odds Ratio for pregnancy Odds ratio (OR) for pregnancy = 1.03; 95% C.I. 0.80–1.33) or calving-to conception interval in multiparous cows (Hazard Ratio = 1.04; 95% C.I. 0.91–1.18). Sampling did not affect culling risk (Hazard Ratio HR = 0.92; 95% C.I. 0.77–1.11) after accounting for covariates. After stratification by parity, milk production was not affected by sampling except in fourth- and fifth-parity cows where sampled cows produced more milk than non-sampled cows after controlling for first test-day milk production and days-postpartum at first test-day. In conclusion, sampling by low-volume uterine lavage did not have significant detrimental effects on reproduction, culling, or milk production. However, there was a tendency for lower first-service conception in sampled primiparous cows, but the procedure appeared to be benign in multiparous cows.

Phenotypic and genetic parameters of reproductive traits in Tunisian Holstein cows

Various factors influencing reproduction in dairy Holstein cows were routinely evaluated and genetic parameters were estimated for four traits for assessing fertility of artificially inseminated cows: Calving to first service interval (CFSI), calving interval (CI), calving to conception interval (CCI), and number of services per conception (NSC). Data used in this investigation consisted of records of insemination and calving events on Tunisian Holstein cows. Records were registered from 1994 to 2003 in 150 herds to study the effects of non-genetic factors and estimate the heritabilities of those fertility traits. The factors examined were: month and year of calving, herd, parity, and year-month of calving. The effect of month and year of calving (or insemination), herd, parity and year-month of calving were included in the model and were significant (P &lt; 0.01) except for the number of lactations that does not have an effect on the number of services per conception. A decreasing efficiency in cow fertility was observed over the last years, with a longer day for first service interval. Heritability for fertility traits was low ranging from 0.027 for NSC to 0.067 for CI. The results suggested that more attention should be paid to herds with too low fertility traits and that monitoring/alert and intervention schemes should be tested in research/action approaches.

Longitudinal observation on reproductive and lactation performances of smallholder crossbred dairy cattle in Fitche, Oromia region, central Ethiopia

A two-year longitudinal study was conducted to assess the reproductive and lactation performances of smallholder crossbred dairy cattle in Fitche, central Ethiopia. Twenty-four smallholder dairy farms were monitored and data on reproductive, breeding, lactation and management aspects of crossbred dairy cows (n=69) were collected and analysed. Moreover, milk samples were collected and analysed for progesterone. The overall Least-squares means for calving interval (CI), calving to conception interval (CCI) and first observed oestrus after calving were 516, 253 and 141 days, respectively. Suckling significantly prolonged these intervals. The mean first onset of luteal activity (OLA) after calving was 52 days, while 67.4% n=43) had a delayed (>55 days) return to cyclicity after calving. Suckling and parity number significantly (p < 0.05) influenced the OLA. The mean lactation length was 54.4 weeks. The overall daily mean milk yield for the first 43 weeks of lactation after calving was 11.7 L/day. The estimated daily milk yield increased slowly and reached peak (13.8 L/day) around the 11th week post partum and declined gradually and steadily. Suckling status, season of calving and parity number significantly influenced the estimated daily milk yield. In conclusion, the present study indicated that the smallholder crossbred dairy cows in the study area had prolonged intervals to first oestrus after calving, to conception and to the next calving, and thus their reproductive performance is unsatisfactory. Delayed first onset of luteal activity (postpartum anoestrus) contributed to these extended intervals. Further detailed investigation is suggested to examine the effects of other relevant factors on the reproductive and lactation performances of smallholder crossbred dairy cows for appropriate intervention.

Relationships Among Milk Production, Energy Balance, Plasma Analytes, and Reproduction in Holstein-Friesian Cows

Associations were examined between components and indicators of early lactation energy balance (EB) and measures of fertility in Holstein cows. Milk production, dry matter intake (DMI), body condition score (BCS), and endocrine and metabolite data from 96 cows were analyzed using multivariate logistic regression and survival analysis. Fertility variables investigated were interval to commencement of luteal activity (C-LA), calving to conception interval (CCI), and conception rate to first service (CON1). Mean daily EB, milk protein content, and DMI during the first 28 d in milk were associated positively with CON1. Cows having poorer BCS (≤2.25) at first service had a lower CON1. Positive associations were identified among EB, milk protein content, DMI, and the likelihood of a shorter interval to C-LA. Cows having greater DMI and a more positive EB had an increased likelihood of a shorter CCI, whereas a lower nadir BCS was associated with an increased likelihood of a longer CCI. Milk yield was not associated with any of the fertility variables investigated. A greater plasma concentration of insulin-like growth factor I (IGF-I) during the first 2 wk of lactation was associated with a greater CON1 and an increased likelihood of a shorter interval to C-LA. In conclusion, we identified DMI as the principal component of EB influencing subsequent fertility. Furthermore, results indicate that milk protein content and plasma IGF-I concentration in early lactation may be useful indicators of reproductive efficiency.