Genetic correlations between production and disease traits during first lactation in Holstein cows

The aim of this study was to estimate genetic correlations between milk yield, somatic cell score (SCS), mastitis, and claw and leg disorders (CLDs) during first lactation in Holstein cows by using a threshold–linear random regression test-day model. We used daily records of milk, fat and protein yields; somatic cell count (SCC); and mastitis and CLD incidences from 46 771 first-lactation Holstein cows in Hokkaido, Japan, that calved between 2000 and 2009. A threshold animal model for binary records (mastitis and CLDs) and linear animal model for yield traits were applied in our multiple trait analysis. For both liabilities and yield traits, additive genetic effects were used as random regression on cubic Legendre polynomials of days on milk. The highest positive genetic correlations between yields and disease incidences (0.36 for milk and mastitis, 0.56 for fat and mastitis, 0.24 for protein and mastitis, 0.32 for milk and CLD, 0.44 for fat and CLD and 0.31 for protein and CLD) were estimated at about the time of peak milk yield (36 to 65 days in milk). Selection focused on early lactation yield may therefore increase the risk of mastitis and CLDs. The positive genetic correlations of SCS with mastitis or CLD incidence imply that selection to reduce SCS in the early stages of lactation would decrease the incidence of both mastitis and CLD.     

Effect of timing of first clinical mastitis occurrence on lactational and reproductive performance of Holstein dairy cows

Objectives of this study were to determine the influence of timing of first clinical mastitis case occurrence on lactational and reproductive performance in high producing lactating dairy cows during the first 320 days in milk (DIM). Holstein cows, 1001, from two commercial dairy farms in California were retrospectively divided into four treatment groups according to timing of first clinical mastitis case caused by environmental pathogens: control with no recorded clinical cases of mastitis (C; n=501); first clinical mastitis prior to first postpartum AI (MG1; n=250); first clinical mastitis between first postpartum AI and pregnancy diagnosis (MG2; n=147); and first clinical mastitis after diagnosed pregnant (MG3; n=103). Clinical cases of mastitis were identified at every milking by the herd personnel based on abnormal milk or swelling of the mammary gland. A fore sample of milk was aseptically collected from every clinical case for microbiological culture. Mastitis decreased yields of milk, 3.5% fat-corrected milk, and milk components, but the effect was only observed for MG1 and MG2. Cows in the control group had lower linear somatic cell count (SCC) score throughout the lactation. Culling was increased by mastitis, and cows in the mastitis groups left the study earlier than controls. Conception rate at first postpartum AI and pregnancy rate at the end of the study were both decreased by mastitis prior to or after first AI, and MG1 and MG2 cows had extended days open. Furthermore, cows experiencing mastitis during lactation had a higher incidence of abortions. The negative effects of mastitis on reproduction were observed regardless of clinical case being caused by either Gram positive or negative bacteria. Mastitis either prior to or after first postpartum AI impairs lactation performance, increases culling, and decreases reproductive efficiency in high producing Holstein dairy cows.     

Genetic analysis for mastitis resistance and milk somatic cell score in French Lacaune dairy sheep

Genetic analysis for mastitis resistance was studied from two data sets. Firstly, risk factors for different mastitis traits, i.e. culling due to clinical or chronic mastitis and subclinical mastitis predicted from somatic cell count (SCC), were explored using data from 957 first lactation Lacaune ewes of an experimental INRA flock composed of two divergent lines for milk yield. Secondly, genetic parameters for SCC were estimated from 5 272 first lactation Lacaune ewes recorded among 38 flocks, using an animal model. In the experimental flock, the frequency of culling due to clinical mastitis (5%) was lower than that of subclinical mastitis (10%) predicted from SCC. Predicted subclinical mastitis was unfavourably associated with the milk yield level. Such an antagonism was not detected for clinical mastitis, which could result, to some extent, from its low frequency or from the limited amount of data. In practice, however, selection for mastitis resistance could be limited in a first approach to selection against subclinical mastitis using SCC. The heritability estimate of SCC was 0.15 for the lactation mean trait and varied from 0.04 to 0.12 from the first to the fifth test-day. The genetic correlation between lactation SCC and milk yield was slightly positive (0.15) but showed a strong evolution during lactation, i.e. from favourable (-0.48) to antagonistic (0.27). On a lactation basis, our results suggest that selection for mastitis resistance based on SCC is feasible. Patterns for genetic parameters within first lactation, however, require further confirmation and investigation.     

长江下游地区中国荷斯坦奶牛生乳中菌落总数的影响因素分析

【背景】随着人们生活水平和健康意识的提高,作为部分乳制品的原料,生乳的质量安全问题显得尤为重要。【目的】检测长江下游地区某集约化牧场中国荷斯坦奶牛生乳中菌落总数、总大肠菌群数的真实水平,同时对影响其变化的生理因素和环境因素进行探讨。【方法】以中国荷斯坦奶牛生乳为研究对象,用乳房炎快速诊断剂检测乳房炎感染情况,菌落总数、总大肠菌群数和环境细菌数的检测方法参照国家标准。对采集的生乳样本进行细菌常规分离鉴定,同时收集乳成分变化数据。【结果】多因素方差分析结果表明,不同泌乳阶段和不同产奶量对荷斯坦奶牛生乳中菌落总数的影响显著(P0.05)和极显著(P0.01);体况、泌乳阶段、胎次、产奶量及乳区对大肠菌群数均无显著影响(P0.05)。夏季生乳的菌落总数、大肠菌群数均极显著地高于其他季节(P0.01);场区内各牛舍的不同卫生环境及细菌数对菌落总数、大肠菌群数的影响均在显著以上(P0.05)。不同乳房炎的感染程度对菌落总数影响极显著(P0.01)。细菌鉴定结果是葡萄球菌属和杆菌属感染居多,链球菌属感染几乎没有。菌落总数的变化对乳蛋白率影响不显著(P0.05),对乳脂率的影响极显著(P0.01)。【结论】随机采样泌乳牛群的不同生理和病理状况、外界不同饲养条件及卫生环境对生乳中菌落总数和大肠菌群数有不同程度的影响,生乳的乳脂率与细菌总数变化负相关。     

Bacterial Analysis of Breast Milk: A Tool to Differentiate Raynaud’s Phenomenon from Infectious Mastitis During Lactation

Lactational Raynaud’s syndrome may be misdiagnosed as infectious mastitis on the basis of the breast pain. The objective of this work was to elucidate if microbiological analysis of milk may contribute to the differentiation of both conditions. Ten lactating women clinically diagnosed by Spanish lactation consultants were included in the study. Of these, five suffered from mastitis and the remaining five suffered from Raynaud’s syndrome. Breast milk samples were inoculated on diverse culture media. Seventy isolates were selected and identified by 16S rDNA PCR sequencing. Parallel, PCR-DGGE and quantitative real-time PCR were used to assess the presence of bacterial DNA in the samples. Neither bacteria nor yeasts could be detected in the milk samples provided by the women suffering from Raynaud’s syndrome. In contrast, large numbers of bacteria were isolated from those with infectious lactational mastitis. Globally, the levels of bacterial DNA were significantly higher in the milk of mastitis-suffering women. Bacteriological analysis of milk can be an useful tool to facilitate the differential diagnosis between the infectious mastitis and Raynaud’s syndrome during lactation.     

The effect of out-wintering pad design on dirtiness score, somatic cell score and mastitis incidence in dairy cows

This study aimed to compare three woodchip out-wintering pad (OWP) designs, and indoor cubicle housing with regard to cow dirtiness scores during the winter housing period, and udder health during both the winter period and the following lactation, for spring-calving dairy cows. The treatments were: an uncovered (UP) and covered (CP) OWP with a concrete feed apron; an uncovered OWP with self-feed silage pit provided directly on the woodchips (SP); and indoor cubicle housing (IC). Data were compared during 2 years: year 1 was a case study while year 2 was an experimental study. In year 1, treatments were UP (space allowance = 12 m2/cow), CP (6 m2/cow) and IC. In year 2, all three OWP designs (12 m2/cow) were compared with IC. Animals were assigned to treatments at the end of lactation in the autumn, and remained there while dry until calving the following spring. Subsequently, all cows were at pasture during lactation. Outcome measures for analysis were cow dirtiness score, somatic cell score (SCS) and incidence of clinical mastitis during the dry period and during lactation. Quarter milk samples were also taken at drying off, calving and 3 weeks post partum both years, and at approximately 113 days in milk in year 2. Samples were analysed for presence of mastitis-causing agents and SCS was determined. Sub-clinical mastitis was diagnosed when cows had an SCS greater than 200 000, or California mastitis test greater than 1 in at least one quarter. In year 1, cows in CP were dirtier than cows in the other two treatments. These animals also had the highest SCS during lactation and tended to have more mastitis-causing agents isolated from quarter milk samples. In year 2, when all cows were stocked at the same density, cows in the sheltered OWP (i.e. CP) had similar dirtiness scores to cows in cubicles and significantly lower dirtiness scores than cows in the unsheltered OWP designs, i.e. UP and SP. However, there were no effects on SCS or quarter sample results. Cleaning of OWP's stocked at 12 m2/cow reduced cow dirtiness scores. However, cleaning of CP in year 1 when cows were stocked at 6 m2/cow had no effect on dirtiness scores. We conclude that dry cows stocked at 12 m2/cow on OWP's are unlikely to have udder health problems in the subsequent lactation. Furthermore, provision of shelter and cleaning of the woodchips are management factors that help to keep cows clean on OWP's.     

Short communication: Variance and autocorrelation of deviations in daily milk yield are related with clinical mastitis in dairy cows

Daily milk production, and fluctuations therein, can provide information on health and resilience of dairy cows. We studied variance and autocorrelation of deviations in daily milk yield in relation to the occurrence of clinical mastitis (no, early or later in lactation). Individual lactation curves were fitted to 305-d lactations of 414 dairy cows using quantile regression. Log-transformed variance (lnVar) and autocorrelation of the quantile residuals of daily milk yield (predicted – observed) were evaluated for intervals until 30 and until 305 days in milk (DIM). Cows were classified as having no mastitis (n = 249), early mastitis that first occurred before 30 DIM (n = 29); or later mastitis (n = 136). Subsequently, linear models were used to assess effects of mastitis and parity class (primiparous or multiparous) on lnVar and autocorrelations; and logistic regression analyses were performed to predict mastitis from lnVar or autocorrelation and parity. From 10 to 30 DIM, lnVar was greater for cows with early mastitis than for cows with no or late mastitis, and autocorrelation tended to be lower for cows with early mastitis than for cows with no mastitis. The lnVar and autocorrelation from 10 to 30 DIM were not predictive of late mastitis. From 10 to 305 DIM, lnVar was greater and autocorrelation was lower for both cows with early and late mastitis than for cows with no mastitis; and both were predictive of having mastitis in the 305-d lactation. Primiparous cows had lower lnVar than multiparous cows. In cows without mastitis, autocorrelation values were positively correlated with lnVar. Results confirm that increased lnVar is associated with clinical mastitis.     

Relation of Milk Production Loss to Milk Somatic Cell Count

Milk production loss was studied in relation to increased somatic cell count (SCC). Available data were weekly test-day milk yields and SCC (in 1,000 cells/ml), and mastitis incidences. In total, 18,131 records from 274 cows were used. Production loss was determined for test-day kg milk, kg protein, and kg energy-corrected milk. Least-squares analysis of variance was used to estimate the direct effect of Log10(SCC) on production. The recorded measures of production were first corrected for fixed effects, with adjustment factors estimated from a healthy data-set. The average daily milk yield was 19.7 kg/day in first lactation and 22.0 in later lactations. The geometric mean of SCC was 63.1 in first lactation and 107.2 in later lactations. The incidence of clinical mastitis treated by a veterinarian was 19.8% of the lactations-at-risk. Linear relationships were found between the production parameters and Log10(SCC). Quadratic and cubic effects were evaluated, but were found to contribute little to the overall fit of the models. The individual milk yield loss was 1.29 kg/day for each unit increase in Log10(SCC) for cows in first lactation. Milk yield decreased by 2.04 kg/day per unit Log10(SCC) for older cows. Corresponding values for protein yield were 0.042 and 0.067 kg/day for first and later lactations, respectively.     

Estimation of Mineral and Trace Element Profile in Bubaline Milk Affected with Subclinical Mastitis

The milk samples from buffaloes of Murrah breed at mid lactation stage, reared at an organised dairy farm, were screened for subclinical mastitis based on bacteriological examination and somatic cell count following International Dairy Federation criteria. Milk samples from subclinical mastitis infected and healthy buffaloes were analysed to evaluate physicochemical alterations in terms of protein, fat, pH, electrical conductivity, chloride, minerals (sodium, potassium and calcium) and trace elements (iron, zinc, copper and selenium). In the present study, protein, fat, zinc, iron, calcium and selenium content was significantly lower (P < 0.001), while pH and electrical conductivity were significantly higher in mastitic milk as compared to normal milk. Concentration of electrolytes mainly sodium and chloride significantly increased with higher somatic cell count in mastitic milk and to maintain osmolality; potassium levels decreased proportionately. Correlation matrix revealed significantly positive interdependences of somatic cell count with pH, electrical conductivity, sodium and chloride. However, protein, fat, calcium and potassium were correlated negatively with elevated somatic cell count in mastitic milk. It is concluded that udder infections resulting in elevated somatic cells may alter the mineral and trace element profile of milk, and magnitude of changes may have diagnostic and prognostic value.     

Diagnostic Alternatives Used by Veterinary Surgeons for the Recording of Udder Diseases in the Norwegian Health Card System for Cattle

A questionnaire, in which 7 cases of udder disease were described, was distributed to 890 veterinarians in Norway. They were requested to classify the cases according to the diagnostic alternatives listed in the Norwegian Health Card System for Cattle (NHCSC). The NHCSC recordings are used for progeny testing of bulls, for disease monitoring, and for research purposes. The aim of this study was to evaluate the quality of the recordings for udder diseases. The questionnaire was answered by 633 veterinary surgeons. Four cases of clinical mastitis (CM) with abnormal secretion as well as other clinical signs of inflammation were correctly classified as CM by almost 100% of the veterinary surgeons. A cow in the final stage of lactation, showing no clinical signs except for clots in the milk, was considered not to be a clinical case by more than 25% of the veterinary surgeons. A typical case of subclinical mastitis (SM) was reported as SM by 83% of the veterinary surgeons, and as CM by 16%. A subclinical case with a recent history of clots in the secretion was classified as SM by 66% of the veterinary surgeons, but almost 40% either reported CM as their sole diagnosis or considered the case to be CM in combination with SM. Of the clinical cases, those exhibiting marked local signs of inflammation and a systemic reaction were correctly classified as acute clinical mastitis (ACM) by 96%–98% of the veterinary surgeons. In the NHCSC, the diagnostic alternatives for cases of CM are ACM and chronic clinical mastitis (CCM). One case, for which the diagnosis subacute clinical mastitis was appropriate according to standard definitions, was classified as CCM by 66%), and as ACM by 6%. Based on the information given in the questionnaire, the diagnosis for 2 of the clinical cases could have been either ACM or CCM, and for both cases each of these 2 alternatives was reported by more than 43% of the veterinary surgeons. A teat lesion, which was present together with ACM in one cow, was reported by 91% of the veterinary surgeons.     

Effects of continuous lactation and short dry periods on mammary function and animal health

The dry period is required to facilitate cell turnover in the bovine mammary gland in order to optimize milk yield in the next lactation. Traditionally, an 8-week dry period has been a standard management practice for dairy cows based on retrospective analyses of milk yields following various dry period lengths. However, as milk production per cow has increased, transitioning cows from the nonlactating state to peak milk yield has grown more problematic. This has prompted new studies on dry period requirements for dairy cows. These studies indicate a clear parity effect on dry period requirement. First parity animals require a 60-day dry period, whereas lactations following later parities demonstrate no negative impact with 30-day dry period or even eliminating the dry period when somatotropin (ST) is also used to maintain milk yields. Shortened dry periods in first parity animals were associated with reduced mammary cell turnover during the dry period and early lactation and increased numbers of senescent cells and reduced functionality of lactating alveolar mammary cells postpartum. Use of ST and increased milking frequency postpartum reduced the impact of shortened dry periods. The majority of new intramammary infections occur during the dry period and persist into the following lactation. There is therefore the possibility of altering mastitis incidence by modifying or eliminating the dry period in older parity animals. As the composition of mammary secretions including immunoglobulins may be reduced when the dry period is reduced or eliminated, there is the possibility that the immune status of cows during the peripartum period is influenced by the length of the dry period.     

A microtiter plate assay for N-acetyl-beta-D-glucosaminidase using a fluorogenic substrate

We describe a simple endpoint method for the determination of N-acetyl-beta-D-glucosaminidase (NAGase; EC 3.2.1.30). NAGase uses a fluorogenic substrate, 4-methylumbelliferyl-N-acetyl-beta-D-glucosaminide, at pH 4.6, liberating the fluorescent 4-methylumbelliferone. The method is reproducible and fast both at room temperature and at 37 degrees C. The procedure developed can be used, e.g., in the diagnosis of bovine subclinical mastitis, where elevated NAGase activities are found in raw milk samples. The assay procedure has a high capacity and high sensitivity and several hundred milk samples can be screened per hour using 96-well microtiter plates and an automated fluorescence reader. In addition to its use in mastitis diagnosis, the assay can be used in the diagnosis of some diseases of human origin.     

Genetic parameters for serial, automatically recorded milkability and its relationship to udder health in dairy cattle

Serial measurements of three milkability traits from two commercial dairy farms in Germany were used to estimate heritabilities and breeding values (BVs). Overall, 6352 cows in first, second and third lactations supplied 2 188 810 records based on daily values recorded from 1998 to 2003. Only the records between day 8 and day 305 after calving were considered. The estimated genetic correlations between different parities within the three milkability traits ranged from rg = 0.88 to 0.98, i.e. they were sufficiently high to warrant a repeatability model. The resulting estimated heritability coefficients were h2 = 0.42 for average milk flow, h2 = 0.56 for maximum milk flow and h2 = 0.38 for milking time. We analysed the genetic correlation between milkability and somatic cell score (SCS) and between milkability and the liability to mastitis, respectively, as the optimum milk flow for udder health is not well defined. There were 66 146 records with information on somatic cell count. Furthermore, 23 488 days of medical treatment for udder diseases were available, resulting in 2 600 302 days of observation in total. Heritabilities for the liability to mastitis, estimated with a test-day threshold model, were h2 = 0.19 and h2 = 0.13, depending on the data-recording period (first 50 days of lactation and first 305 days of lactation, respectively). With respect to the relationship between milkability and udder health, the results indicated a slight and linear correlation insofar as one can assume: the higher the milk flow, the worse the udder health. For this reason, bulls and cows with high BVs for milk flow should be excluded from breeding to avoid a deterioration of udder health. The establishment of a special data-recording scheme for functional traits such as milkability and mastitis on commercial dairy farms may be possible according to these results.     

Differential protein composition of bovine whey: a comparison of whey from healthy animals and from those with clinical mastitis

During clinical mastitis in dairy cows, the quantity of milk produced decreases and the composition of the milk is altered. As the severity of inflammation associated with the disease increases, the chemical composition of milk approaches that of blood as a consequence of increased permeability of the blood mammary barrier, or de novo intramammary synthesis, as has been suggested for mammary associated serum amyloid A3. A better understanding of these events may provide new approaches for the diagnosis and treatment of mastitis. The objective of this study was to document the changes in the protein composition of milk during clinical mastitis using a proteomic approach, with the objective of identifying new diagnostic markers of mastitis. Whey from dairy cows with clinical mastitis was compared to whey from healthy animals by two-dimensional gel electrophoresis (2-DE) with colloidal Coomassie staining and matrix-assisted desorption/ionization mass spectrometry. Increases in the concentrations of proteins of blood serum origin, including serotransferrin and albumin, were identified in mastitic whey compared to normal whey, while concentrations of the major whey proteins alpha-lactalbumin and beta-lactoglobulin were reduced in mastitic whey. Mass spectrometry subsequently confirmed the location of albumin, alpha-lactalbumin and beta-lactoglobulin on the 2-DE gels at M(r)/pI of 69 294/5.8, 14 200/4.5 and 19 883/4.9 respectively.     

Identification of SNPs in Interferon Gamma,Interleukin-22, and Their Receptors and Associations with Health and Production-Related Traits in Canadian Holstein Bulls

Genetic variants in a number of immunoregulatory genes have been previously associated with health and production traits in dairy cattle. Therefore, in the following study, the genes coding interferon gamma (IFNG), IFNG receptor 1 and 2 domains, interleukin-22 (IL22), and IL22 receptor alpha 1, were investigated for single nucleotide polymorphisms (SNPs) in Holstein bulls. These SNPs, along with SNPs previously identified in IL10, IL10 receptor, and transforming growth factor beta 1 (TGFB1) genes, were evaluated for statistical associations to estimated breeding values for milk somatic cell score (SCS), a trait highly correlated to mastitis incidence, and various production-related traits, including milk yield, protein yield, fat yield, and lactation persistency. While no significant associations were found between these SNPs and SCS, SNPs in IL10 receptor beta subunit showed a significant effect on protein yield and lactation persistency. While there is evidence that IL10 plays an important role during lactation, it is also likely that the effects of SNPs in IL10 receptor beta subunit on protein yield and lactation persistency are due to linkage disequilibrium with a neighboring QTL.     

Activation of nuclear factor kappa B in mammary epithelium promotes milk loss during mammary development and infection

We investigated whether nuclear factor kappa B (NF‐κB), which exhibits a regulated pattern of activity during murine mammary gland development, plays an important role during lactation and involution, when milk production ceases and the gland undergoes apoptosis and re‐modeling. We generated a doxycycline inducible transgenic mouse model to activate NF‐κB specifically in the mammary epithelium through expression of a constitutively active form of IKK2, the upstream kinase in the classical NF‐κB signaling cascade. We found that activation of NF‐κB during involution resulted in a more rapid reduction in milk levels and increased cleavage of caspase‐3, an indicator of apoptosis. We also found that activation of NF‐κB during lactation with no additional involution signals had a similar effect. The observation that NF‐κB is a key regulator of milk production led us to investigate the role of NF‐κB during mastitis, an infection of the mammary gland in which milk loss is observed. Mammary gland injection of E. coli LPS resulted in activation of NF‐κB and milk loss during lactation. This milk loss was decreased by selective inhibition of NF‐κB in mammary epithelium. Together, our data reveal that activation of NF‐κB leads to milk clearance in the lactating mammary gland. Therefore, targeting of NF‐κB signaling may prove therapeutic during mastitis in humans and could be beneficial for the dairy industry, where such infections have a major economic impact. J. Cell. Physiol. 222:73–81, 2010. © 2009 Wiley‐Liss, Inc.     

Identification of SNPs in interferon gamma, interleukin-22, and their receptors and associations with health and production-related traits in Canadian Holstein bulls

Genetic variants in a number of immunoregulatory genes have been previously associated with health and production traits in dairy cattle. Therefore, in the following study, the genes coding interferon gamma (IFNG), IFNG receptor 1 and 2 domains, interleukin-22 (IL22), and IL22 receptor alpha 1, were investigated for single nucleotide polymorphisms (SNPs) in Holstein bulls. These SNPs, along with SNPs previously identified in IL10, IL10 receptor, and transforming growth factor beta 1 (TGFB1) genes, were evaluated for statistical associations to estimated breeding values for milk somatic cell score (SCS), a trait highly correlated to mastitis incidence, and various production-related traits, including milk yield, protein yield, fat yield, and lactation persistency. While no significant associations were found between these SNPs and SCS, SNPs in IL10 receptor beta subunit showed a significant effect on protein yield and lactation persistency. While there is evidence that IL10 plays an important role during lactation, it is also likely that the effects of SNPs in IL10 receptor beta subunit on protein yield and lactation persistency are due to linkage disequilibrium with a neighboring QTL.     

Trans-Generational Effect of Maternal Lactation during Pregnancy: A Holstein Cow Model

Epigenetic regulation in mammals begins in the first stages of embryogenesis. This prenatal programming determines, in part, phenotype expression in adult life. Some species, particularly dairy cattle, are conceived during the maternal lactation, which is a period of large energy and nutrient needs. Under these circumstances, embryo and fetal development compete for nutrients with the mammary gland, which may affect prenatal programming and predetermine phenotype at adulthood. Data from a specialized dairy breed were used to determine the transgenerational effect when embryo development coincides with maternal lactation. Longitudinal phenotypic data for milk yield (kg), ratio of fat-protein content in milk during first lactation, and lifespan (d) from 40,065 cows were adjusted for environmental and genetic effects using a Bayesian framework. Then, the effect of different maternal circumstances was determined on the residuals. The maternal-related circumstances were 1) presence of lactation, 2) maternal milk yield level, and 3) occurrence of mastitis during embryogenesis. Females born to mothers that were lactating while pregnant produced 52 kg (MonteCarlo standard error; MCs.e. = 0.009) less milk, lived 16 d (MCs.e. = 0.002) shorter and were metabolically less efficient (+0.42% milk fat/protein ratio; MCs.e.<0.001) than females whose fetal life developed in the absence of maternal lactation. The greater the maternal milk yield during embryogenesis, the larger the negative effects of prenatal programming, precluding the offspring born to the most productive cows to fully express their potential additive genetic merit during their adult life. Our data provide substantial evidence of transgenerational effect when pregnancy and lactation coincide. Although this effect is relatively low, it should not be ignored when formulating rations for lactating and pregnant cows. Furthermore, breeding, replacement, and management strategies should also take into account whether the individuals were conceived during maternal lactation because, otherwise, their performance may deviate from what it could be expected.