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Shortening or omitting the dry period to improve the energy balance in early lactation have the trade-offs of reduction in milk production and loss of opportunity for dry-cow therapy (DCT; i.e., intramammary antibiotic use at dry-off). Customized dry-period strategies (i.e., deciding upon DCT and dry-period length per cow) could mitigate negative effects of short or no dry periods on milk production and udder health and simultaneously retain benefits from improved energy balance and fertility. In this study, we evaluated 3 decision trees to customize dry-period strategies for individual cows. In the control tree (CT), all cows had a 60-d dry period, with DCT if somatic cell count (SCC) was >150,000 cells/mL before dry-off. In decision tree 1 (T1), parity 1 and parity >1 cows were assigned DCT if SCC was ≥150,000 cells/mL and SCC ≥50,000 cells/mL, respectively; whereas in decision tree 2 (T2), the threshold for DCT was SCC ≥200,000 cells/mL for all animals. In T1 and T2, cows with DCT were assigned a 60-d dry period, whereas cows without DCT were assigned a 30-d or 0-d dry period if their milk production remained >12 kg/d at 67 and 37 d before calving, respectively. Cows were monitored from 8 wk before to 14 wk after calving. Milk production and composition, SCC, body condition score, body weight, and occurrence of treatment for disease (related to calving and start of lactation) were compared between CT (n = 61 cows), T1 (n = 59 cows), and T2 (n = 63 cows). Effects of decision trees (CT, T1, T2) and of dry-period strategies (60-d dry with or without antibiotics, 30-d dry, or 0-d dry) on measured variables were analyzed separately with mixed models, effects on udder-health status with a logistic regression, and occurrence of treatment for diseases with a Pearson chi-squared test. In T1, 36% of cows qualified for 30-d and 2% for 0-d dry periods, whereas in T2 this was 51% and 30% for 30-d and 0-d dry periods, respectively. Compared with CT, cows in T1 and T2 on average produced more milk in the 8 wk before calving (0.2 vs. 3.9 vs. 7.1 kg/d in CT vs. T1 vs. T2), and less in the 14 wk after calving (40.0 vs. 37.0 vs. 35.2 kg/d in CT vs. T1 vs. T2). There was no difference in udder-health status in the transition period among decision trees. In the first 14 wk after calving, recovery of body weight was greater for T2 than CT and T1. Overall, 30-d and 0-d dry periods reduced milk revenues, but this might be financially compensated by improved cow health with customized dry-period strategies.

Medicina : monthly medical journal of Lithuanian Medical Association, Kaunas University of Medicine and Vilnius University 57(9), 884 (2021). doi:10.3390/medicina57090884 special issue: "Special issue "Hip and fragility fracture management" / special issue editor: Matthias Knobe, guest editor", Published by Kaunas Univ. of Medicine, Kaunas

Numerous methods and devices are available for implant fixation in anterior cruciate ligament (ACL) reconstruction. Biomechanical data indicate high variability in fixation stability across different devices. This study aims to provide a better insight into measuring the structural characteristics and mechanical behavior of ACL implant fixations. Fourteen human tibial specimens with reconstructed ACLs were subjected to progressively increasing dynamic loading until failure. The motions of the tibia, the proximal and distal graft ends, as well as the testing frame and actuator, were continuously recorded via a motion tracking system. Significantly higher displacements of the machine actuator (1.0 mm at graft slippage onset, and 12.2 mm at ultimate load) were measured compared to the displacements of the proximal (0.8 and 4.3 mm, respectively) and distal graft (0.1 and 3.4 mm, respectively) ends. The displacements measured at different sites showed significant correlations. The provided data suggest significant and systematic inaccuracies in the stiffness and slippage of the fixation when using machine displacement, as commonly reported in the literature. The assessment of the distal graft displacement excludes the artifactual graft elongation, and most accurately reflects the graft slippage onset indicating clinical failure. Considering the high displacement at the ultimate load, the ultimate load could be used as a standardized variable to compare different fixation methods. However, the ultimate load alone is not sufficient to qualitatively describe fixation stability.

Earlier studies indicated that the inflammatory status of dairy cows in early lactation could not be fully explained by the negative energy balance (NEB) at that moment. The objective of the present study was to determine relationships between inflammatory biomarkers and oxidative stress with uterine health in dairy cows after different dry period lengths. Holstein–Friesian dairy cows were assigned to one of three dry period lengths (0-, 30-, or 60-d) and one of two early lactation rations (glucogenic or lipogenic ration). Cows were fed either a glucogenic or lipogenic ration from 10-d before the expected calving date. Part of the cows which were planned for a 0-d dry period dried themselves off and were attributed to a new group (0 → 30-d dry period), which resulted in total in four dry period groups. Blood was collected (N = 110 cows) in weeks −3, −2, −1, 1, 2, and 4 relative to calving to determine biomarkers for inflammation, liver function, and oxidative stress. Uterine health status (UHS) was monitored by scoring vaginal discharge (VD) based on a 4-point scoring system (0, 1, 2, or 3) in weeks 2 and 3 after calving. Cows were classified as having a healthy uterine environment (HU, VD score = 0 or 1 in both weeks 2 and 3), nonrecovering uterine environment (NRU, VD score = 2 or 3 in week 3), or a recovering uterine environment (RU, VD score = 2 or 3 in week 2 and VD score= 0 or 1 in week 3). Independent of dry period length, cows with NRU had higher plasma haptoglobin (P = 0.05) and lower paraoxonase levels (P < 0.01) in the first 4 weeks after calving and lower liver functionality index (P < 0.01) compared with cows with HU. Cows with NRU had lower plasma albumin (P = 0.02) and creatinine (P = 0.02) compared with cows with a RU, but not compared with cows with HU. Independent of UHS, cows with a 0 → 30-d dry period had higher bilirubin levels compared with cows with 0-, 30-, or 60-d dry period (P < 0.01). Cows with RU and fed a lipogenic ration had higher levels of albumin in plasma compared with cows with NRU and fed a lipogenic ration (P < 0.01). In conclusion, uterine health was related to biomarkers for inflammation (haptoglobin and albumin) and paraoxonase in dairy cows in early lactation. Cows which were planned for a 0-d dry period, but dried themselves off (0 → 30-d dry period group) had higher bilirubin levels, which was possibly related to a more severe NEB in these cows. Inflammatory biomarkers in dairy cows in early lactation were related to uterine health in this period.

Metabolic status of dairy cows in early lactation can be evaluated using the concentrations of plasma β-hydroxybutyrate (BHB), free fatty acids (FFA), glucose, insulin, and insulin-like growth factor 1 (IGF-1). These plasma metabolites and metabolic hormones, however, are difficult to measure on farm. Instead, easily obtained on-farm cow data, such as milk production traits, have the potential to predict metabolic status. Here we aimed (1) to investigate whether metabolic status of individual cows in early lactation could be clustered based on their plasma values and (2) to evaluate machine learning algorithms to predict metabolic status using on-farm cow data. Through lactation wk 1 to 7, plasma metabolites and metabolic hormones of 334 cows were measured weekly and used to cluster each cow into 1 of 3 clusters per week. The cluster with the greatest plasma BHB and FFA and the lowest plasma glucose, insulin, and IGF-1 was defined as poor metabolic status; the cluster with the lowest plasma BHB and FFA and the greatest plasma glucose, insulin, and IGF-1 was defined as good metabolic status; and the intermediate cluster was defined as average metabolic status. Most dairy cows were classified as having average or good metabolic status, and a limited number of cows had poor metabolic status (10-50 cows per lactation week). On-farm cow data, including dry period length, parity, milk production traits, and body weight, were used to predict good or average metabolic status with 8 machine learning algorithms. Random Forest (error rate ranging from 12.4 to 22.6%) and Support Vector Machine (SVM; error rate ranging from 12.4 to 20.9%) were the top 2 best-performing algorithms to predict metabolic status using on-farm cow data. Random Forest had a higher sensitivity (range: 67.8-82.9% during wk 1 to 7) and negative predictive value (range: 89.5-93.8%) but lower specificity (range: 76.7-88.5%) and positive predictive value (range: 58.1-78.4%) than SVM. In Random Forest, milk yield, fat yield, protein percentage, and lactose yield had important roles in prediction, but their rank of importance differed across lactation weeks. In conclusion, dairy cows could be clustered for metabolic status based on plasma metabolites and metabolic hormones. Moreover, on-farm cow data can predict cows in good or average metabolic status, with Random Forest and SVM performing best of all algorithms.

A 1-yr calving interval (CInt) is usually associated with maximized milk output, due to the calving-related peak in milk yield. Extending CInt could benefit cow health and production efficiency due to fewer transition periods per unit of time. Extending CInt can affect lactation performance by fewer days dry per year, delayed pregnancy effect on milk yield, and greater milk solid yield in late lactation. This study first investigated the effects of 3 different voluntary waiting periods (VWP) from calving until first insemination on body weight, body condition, milk yield, and lactation persistency. Second, individual cow characteristics in early lactation were identified that contributed to milk yield and persistency of cows with different VWP. Holstein-Friesian dairy cows (n = 154) within 1 herd were blocked for parity, calving season, and expected milk yield. Cows were randomly assigned within the blocks to 1 of 3 VWP (50, 125, or 200 d: VWP50, VWP125, or VWP200, respectively) and monitored through 1 complete lactation and the first 6 wk of the subsequent lactation, or until culling. Minimum and mean CInt (384 vs. 452 vs. 501 d for VWP50 vs. VWP125 vs. VWP200) increased with increasing VWP, but maximum CInt was equal for the 3 VWP. Fat- and protein-corrected milk yield (FPCM) was analyzed weekly. Milk yield and FPCM were also expressed per day of CInt, to compare yields of cows with different VWP. Persistency was determined between d 100 and d 200 of the lactation, as well as between d 100 and dry-off. Values are presented as least squares means ± standard error of the mean. During the first 44 wk of lactation, VWP did not affect FPCM yield in both primiparous and multiparous cows. The VWP did not affect milk yield per day of CInt. The VWP did not affect FPCM yield per day of calving interval for primiparous cows. Multiparous cows in VWP125 had FPCM yield per day of CInt similar to that of VWP50. Multiparous cows in VWP200 had lower FPCM yield per day of CInt compared with VWP50 (27.2 vs. 30.4 kg/d). During the last 6 wk before dry-off, cows in VWP125 had lower yield compared with cows in VWP50, which could benefit their udder health in the dry period and after calving. Persistency was better for cows in VWP200 compared with cows in VWP50 (-0.05 vs. -0.07 kg/d). Body weight was not different among VWP groups. Multiparous cows in VWP200 had a higher body condition score in the last 3 mo before dry-off and the first 6 wk of the next lactation, compared with multiparous cows in VWP125 and VWP50. The VWP could be extended from 50 d to 125 d without an effect on daily yield per day of calving interval. Extending VWP until 200 d for primiparous cows did not affect their daily milk yield, but multiparous cows with a 200-d VWP had a reduced milk yield per day of calving interval and an increased body condition in late lactation and the subsequent lactation, compared with multiparous cows with a 50-d VWP.

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.

Dairy cows can experience a negative energy balance (NEB) in early lactation when feed intake is too low to meet the energy requirements for body maintenance and milk production. Metabolic changes occur in mammary gland cells of animals experiencing a negative energy balance. We studied these metabolic changes in milk samples from dairy cows in relation to energy balance status using liquid chromatography-mass spectrometry (QQQ-LC-MS) and nuclear magnetic resonance (1H NMR). NMR and LC-MS techniques are complementary techniques that enabled a comprehensive overview of milk metabolites in our study. Energy balance and milk samples were obtained from 87 dairy cows. A total of 55 milk metabolites were reliably detected, of which 15 metabolites were positively correlated to energy balance and 20 were negatively correlated to energy balance. Cows in NEB produced more milk with increased milk fat yield and higher concentrations of citrate, cis-aconitate, creatinine, glycine, phosphocreatine, galactose-1-phosphate, glucose-1-phosphate, UDP-N-acetyl-galactosamine, UDP-N-acetyl-glucosamine, and phosphocholine but lower concentrations of choline, ethanolamine, fucose, N-acetyl-neuraminic acid, N-acetyl-glucosamine, and N-acetyl-galactosamine. During NEB, we observed an increased leakage of cellular content, increased synthesis of nucleic acids and cell membrane phospholipids, an increase in one-carbon metabolic processes, and an increase in lipid-triglyceride anabolism. Overall, both apoptosis combined with cellular renewal is paramount in the mammary gland in cows in NEB. doi: 10.1021/acs.jproteome.9b00706 ispartof: Journal of Proteome Research vol:19 issue:8 pages:2942-2949 ispartof: location:United States status: published

Negative energy balance in dairy cows in early lactation is related to alteration of metabolic status. However, the relationships among energy balance, metabolic profile in plasma, and metabolic profile in milk have not been reported. In this study our aims were: (1) to reveal the metabolic profiles of plasma and milk by integrating results from nuclear magnetic resonance (NMR) with data from liquid chromatography triple quadrupole mass spectrometry (LC-MS); and (2) to investigate the relationship between energy balance and the metabolic profiles of plasma and milk. For this study 24 individual dairy cows (parity 2.5 ± 0.5; mean ± standard deviation) were studied in lactation wk 2. Body weight (mean ± standard deviation; 627.4 ± 56.4 kg) and milk yield (28.1 ± 6.7 kg/d; mean ± standard deviation) were monitored daily. Milk composition (fat, protein, and lactose) and net energy balance were calculated. Plasma and milk samples were collected and analyzed using LC-MS and NMR. From all plasma metabolites measured, 27 were correlated with energy balance. These plasma metabolites were related to body reserve mobilization from body fat, muscle, and bone; increased blood flow; and gluconeogenesis. From all milk metabolites measured, 30 were correlated with energy balance. These milk metabolites were related to cell apoptosis and cell proliferation. Nine metabolites detected in both plasma and milk were correlated with each other and with energy balance. These metabolites were mainly related to hyperketonemia; β-oxidation of fatty acids; and one-carbon metabolism. The metabolic profiles of plasma and milk provide an in-depth insight into the physiological pathways of dairy cows in negative energy balance in early lactation. In addition to the classical indicators for energy balance (e.g., β-hydroxybutyrate, acetone, and glucose), the current study presents some new metabolites (e.g., glycine in plasma and milk; kynurenine, panthothenate, or arginine in plasma) in lactating dairy cows that are related to energy balance and may be of interest as new indicators for energy balance.

The average life span of dairy cows in the Netherlands is 5.8 years. The main reasons for involuntary culling in dairy cows are infertility, mastitis and locomotion disorders. These disorders often start during the first weeks of lactation due to the inability of the cow to cope with the metabolic changes of the new lactation. The main objective of the present study was to determine the value of the Fourier-transform infrared spectroscopy (FTIR) mid-infrared profile of milk samples taken from dairy cows in the first weeks of lactation 1) as an indicator of the metabolic state in early lactation; and 2) as a predictor of dairy cow’s survival to next lactation. Results showed that cows that reach the next lactation have a higher blood NEFA concentration and a higher milk production with less variation between days. In conclusion, survival of the complete lactation was related with milk performance and metabolic status of dairy cows in early lactation. De gemiddelde levensduur van melkkoeien in Nederland is 5,8 jaar. De voornaamste redenen voor onvrijwillige afvoer van melkvee zijn onvruchtbaarheid, mastitis, en klauw- en beenproblemen. Deze gezondheidsproblemen hebben vaak ook een relatie met de eerste weken van de lactatie vanwege een moeilijke lactatiestart of problemen bij de koe om zich aan te passen aan de nieuwe lactatie met stofwisselingsstoornissen als gevolg. Het doel van deze studie was om de waarde te bepalen van Fourier-transform infrared spectroscopy (FTIR) profielen van melk in begin lactatie voor 1) indicatie van metabole status van de koe in begin lactatie; en 2) als voorspeller van het succesvol afronden van de lactatie. De resultaten laten zien dat koeien die de volgende lactatie bereikten aan het begin van de lactatie een hogere concentratie vetzuren in het bloed hadden en een hogere melkproductie met minder variatie tussen dagen.

This study aimed to (1) investigate effects of reducing postpartum dietary energy level for cows after a 0-d dry period (DP) on resumption of ovarian cyclicity and reproductive performance, (2) relate days open with other reproductive measures, and (3) relate onset of luteal activity (OLA) and days open with metabolic status in early lactation. Holstein-Friesian dairy cows were randomly assigned to 1 of 3 transition treatments: no DP and low postpartum dietary energy level from 22 days in milk( DIM )onwards (0-d DP (LOW)) (n = 42), no DP and standard postpartum dietary energy level (0-d DP (STD)) (n = 43), and a short DP and standard postpartum dietary energy level (30-d DP (STD)) (n = 43). Milk progesterone concentration was determined three times per week until 100 DIM. Plasma metabolite and hormone concentrations were measured weekly until week 7 postpartum. Reducing postpartum dietary energy level in older cows (parity &ge, 3) after no DP and 22 DIM did not affect milk production but prevented a positive energy balance and shortened the interval from calving to OLA. In addition, services per pregnancy and days open were reduced in cows of parity &ge, 3 on 0-d DP (LOW), compared with cows of parity &ge, 3 with 0-d DP (STD), but not in cows of parity 2.

Drying-off, calving, and start of lactation are critical transition events for a dairy cow. As a consequence, most animal health issues occur during these periods. By extending the voluntary waiting period for first insemination after calving, calving interval (CInt) can be extended, with possible positive effects for fertility and health. Some cows might be better suited for an extended CInt than others, due to differences in milk yield level, lactation persistency, or health status, which would justify a customized CInt based on individual cow characteristics. This study aims to investigate 13 farms with customized CInt, with respect to calving to first service interval (CFSI), accomplished CInt, services per conception (SC), conception rate at first artificial insemination (CR1AI), peak yield, lactation persistency, 305-d yield, and effective lactation yield. In total, 4,858 complete lactations of Holstein Friesian cows between 2014 and 2019 from the 13 farms were grouped by parity (1 or 2+) and CFSI (CFSI class; CFSI-1 < 84; 84 ≤ CFSI-2 < 140; 140 ≤ CFSI-3 < 196; 196 ≤ CFSI-4 < 252, CFSI-5 ≥ 252 d) or CInt (CInt class; CInt-1 < 364; 364 ≤ CInt-2 < 420; 420 ≤ CInt-3 < 476; 476 ≤ CInt-4 < 532, CInt-5 ≥ 532 d). Cow inseminations, available for 11 out of 13 farms (3,597 complete lactations), were grouped by parity (1 and 2+) and CFSI class or CInt class. The fertility and milk production characteristics were analyzed with generalized and general linear mixed models. The CFSI class was not associated with SC, but extended CInt class was associated with increased SC (CInt-1–5; 1.11–3.70 SC). More than 50% of cows in the CFSI class 364 d), showing that these cows were not able to conceive for the desired CInt. More than 50% of cows in CInt classes 3 and higher (CInt ≥ 420 d) had an earlier first insemination before successful insemination (CFSI class 1

From calving, dairy cows are typically milked for about a year, and subsequently managed to have a non-lactating or ‘dry period’ (DP) before next calving. However, the use of a DP may reduce cow welfare because typical DP management involves the cow changing groups and ration. Also, the DP results in a severe negative energy balance after calving. Shortening or omitting the DP may have beneficial effects on cow welfare through fewer changes in management before calving, and a lower milk yield after calving. Our objective was to assess the effects of no DP and a short DP (30 days) with associated management on feeding, lying, and number of steps of dairy cows in late gestation and early lactation. Feeding behaviour was recorded by computerized feeders for 122 periods (42 with a short DP and 80 with no DP) from week −6 to week 7 relative to calving. Steps and lying behaviour of 81 of these cows (28 with a short DP and 53 with no DP) were recorded with accelerometers in week −4 and in week 4 relative to calving only. Effects of DP treatment and parity on behaviour were analysed with mixed models. Before calving, cows with a short DP were fed a DP ration, and moved to a dry cow group. During this time, cows with a short DP spent more time lying (13.7 vs. 12.6 h per day; P = 0.01) and feeding (240 vs. 209 min per day; P < 0.01), and stepped less (663 vs. 1130 steps per day; P < 0.01) than cows with no DP. After calving, all cows were fed the same lactation ration and were housed in the same herd. Cows with a short DP, however, had a lower feed intake (35.7 vs 39.1 kg per day; P < 0.01), and spent less time lying (10.7 vs. 11.6 h per day; P = 0.03) after calving than cows with no DP. Milk yield was negatively correlated with daily lying time (r: −0.22; P < 0.05), but was not correlated with daily feeding time. Also, less time was spent on both lying and feeding after calving than before calving. These results indicate that lying time was not constrained by feeding time. Lying time was positively correlated with energy balance (r: 0.28; P < 0.01). Compared with a short DP with associated ration and group changes, no DP reduced lying time and increased the number of steps in late gestation, and resulted in a higher feed intake and longer lying time in early lactation.

The objectives of this study were (1) to evaluate if hyperketonemia in dairy cows (defined as plasma β-hydroxybutyrate ≥1.0 mmol/L) can be predicted using on-farm cow data either in current or previous lactation week, and (2) to study if adding individual net energy intake (NEI) can improve the predictive ability of the model. Plasma β-hydroxybutyrate concentration, on-farm cow data (milk yield, percentage of fat, protein and lactose, fat- and protein-corrected milk yield, body weight, body weight change, dry period length, parity, and somatic cell count), and NEI of 424 individual cows were available weekly through lactation wk 1 to 5 postpartum. To predict hyperketonemia in dairy cows, models were first trained by partial least square discriminant analysis, using on-farm cow data in the same or previous lactation week. Second, NEI was included in models to evaluate the improvement of the predictability of the models. Through leave-one trial-out cross-validation, models were evaluated by accuracy (the ratio of the sum of true positive and true negative), sensitivity (68.2% to 84.9%), specificity (61.5% to 98.7%), positive predictive value (57.7% to 98.7%), and negative predictive value (66.2% to 86.1%) to predict hyperketonemia of dairy cows. Through lactation wk 1 to 5, the accuracy to predict hyperketonemia using data in the same week was 64.4% to 85.5% (on-farm cow data only), 66.1% to 87.0% (model including NEI), and using data in the previous week was 58.5% to 82.0% (on-farm cow data only), 59.7% to 85.1% (model including NEI). An improvement of the accuracy of the model due to including NEI ranged among lactation weeks from 1.0% to 4.4% when using data in the same lactation week and 0.2% to 6.6% when using data in the previous lactation week. In conclusion, trained models via partial least square discriminant analysis have potential to predict hyperketonemia in dairy cows not only using data in the current lactation week, but also using data in the previous lactation week. Net energy intake can improve the accuracy of the model, but only to a limited extent. Besides NEI, body weight, body weight change, milk fat, and protein content were important variables to predict hyperketonemia, but their rank of importance differed across lactation weeks.

Natural autoantibodies (NAAb) have been found in plasma and milk of dairy cows. Natural autoantibodies maintain homeostasis and may prevent infections. The objective of this study was to evaluate the relationship between concentration of plasma free fatty acid (FFA) and the levels of NAAb in plasma binding glutamate dehydrogenase (GD) and carbonic anhydrase (CA) in cows 2 weeks after calving. In total, 55 Holstein-Friesian dairy with 60-d dry period lengths and fed 2 early lactation diets (glucogenic or lipogenic). Blood was sampled at week 1 and 2 after calving. Result showed that from week 1 and 2 relative to calving, levels of IgG and IgM binding CA were positively related with concentration of FFA in plasma. Levels of IgM binding GD were negatively related with concentration of FFA in plasma. It is concluded that IgG and IgM binding CA in plasma might be an indicator for energy status and reflect metabolic status in dairy cows 2 weeks after calving.

Blood metabolite and hormone concentrations are indicative of metabolic status, but blood sampling and analysis is invasive and time-consuming. Monitoring behavior can be done automatically, and behaviors may also be used as indicators of metabolic status. The aim of this study was to analyze the relationships between metabolic status and feeding behavior, lying behavior, motion index and steps of dairy cows in week 4 postpartum. Behavioral data from 81 Holstein-Friesian cows were collected using computerized feeders and accelerometers, and blood samples were collected for analysis of free-fatty acid (FFA), β-hydroxybutyrate (BHB), glucose, insulin, IGF-1 and growth hormone (GH) concentrations. First, cluster analysis was performed to categorize cows as having poor, average, good or very good metabolic status based on their plasma FFA, BHB, glucose, insulin, IGF-1 and GH concentration. Subsequently, the performance and behavior of cows in clusters with poor, average and good metabolic status were compared using GLM. Cows with a poor or average metabolic status tended to have greater fat-and-protein-corrected milk yield than cows with good metabolic status. Furthermore, cows with a poor metabolic status had a lower energy balance and dry matter intake (DMI) than cows with an average or good metabolic status and had a lower number of meals than cows with good metabolic status. Daily number of visits to the feeder and lying time tended to be positively related with metabolic status. Feeding rate (kg/min), daily meal time (min/day), number of lying bouts per day, steps and motion index were not related with metabolic status. In conclusion, better metabolic status in dairy cows in early lactation was associated with a greater DMI, increased feeding activity and a tendency to more time spent lying, compared with poor metabolic status. These results suggest that compromised metabolic status is reflected in altered cow's behavior in week 4 of lactation.

The transition period is the most critical period in the lactation cycle of dairy cows. Extended lactations reduce the frequency of transition periods, the number of calves and the related labour for farmers. This study aimed to assess the impact of 2 and 4 months extended lactations on milk yield and net partial cash flow (NPCF) at herd level, and on greenhouse gas (GHG) emissions per unit of fat- and protein-corrected milk (FPCM), using a stochastic simulation model. The model simulated individual lactations for 100 herds of 100 cows with a baseline lactation length (BL), and for 100 herds with lactations extended by 2 or 4 months for all cows (All+2 and All+4), or for heifers only (H+2 and H+4). Baseline lactation length herds produced 887 t (SD: 13) milk/year. The NPCF, based on revenues for milk, surplus calves and culled cows, and costs for feed, artificial insemination, calving management and rearing of youngstock, was kEuro174 (SD: 4)/BL herd per year. Extended lactations reduced milk yield of the herd by 4.1% for All+2, 6.9% for All+4, 1.1% for H+2 and 2.2% for H+4, and reduced the NPCF per herd per year by kEuro7 for All+2, kEuro12 for All+4, kEuro2 for H+2 and kEuro4 for H+4 compared with BL herds. Extended lactations increased GHG emissions in CO2-equivalents per t FPCM by 1.0% for All+2, by 1.7% for All+4, by 0.2% for H+2 and by 0.4% for H+4, but this could be compensated by an increase in lifespan of dairy cows. Subsequently, production level and lactation persistency were increased to assess the importance of these aspects for the impact of extended lactations. The increase in production level and lactation persistency increased milk production of BL herds by 30%. Moreover, reductions in milk yield for All+2 and All+4 compared with BL herds were only 0.7% and 1.1% per year, and milk yield in H+2 and H+4 herds was similar to BL herds. The resulting NPCF was equal to BL for All+2 and All+4 and increased by kEuro1 for H+2 and H+4 due to lower costs for insemination and calving management. Moreover, GHG emissions per t FPCM were equal to BL herds or reduced (0% to -0.3%) when lactations were extended. We concluded that, depending on lactation persistency, extending lactations of dairy cows can have a positive or negative impact on the NPCF and GHG emissions of milk production.

Shortening or omitting the dry period improves the energy balance and metabolic status of dairy cows in early lactation. Metabolic, behaviour and welfare effects throughout lactation, however, are unclear. The current paper reviews long-term metabolic and welfare consequences of short and no dry period, as well as feeding strategies and individual cow characteristics that could support in optimising management of cows with a short or no dry period. The paper will conclude with impacts of short and no dry periods at herd level and in practice. Energy balance after no or a short dry period is more positive during the complete subsequent lactation. After the initial improvement in early lactation, cows after no dry period tend to fatten and may have a too low lactation persistency to be continuously milked until the onset of the subsequent lactation. Reducing dietary energy level for cows with no dry period reduced fattening during the complete lactation but did not improve lactation persistency. Feeding a more lipogenic diet for cows with a short or no dry period did not affect the energy balance or lactation persistency during the complete lactation, although a lipogenic diet resulted in lower plasma insulin and IGF-1 concentration and greater plasma growth hormone concentration, compared with a glucogenic diet. Effects of dry period length on udder health are ambiguous, whereas short and no dry periods improved fertility in most studies. Omission of the dry period changed behaviour of cows both before and after calving, with a longer lying time and greater feed intake after calving, suggesting a better adaptation to a new lactation. Individual cow characteristics like parity, genotype, prepartum body condition score, and milk yield level determined the metabolic response of cows to a short or no dry period. In conclusion, short or no dry periods increase the energy balance in the complete lactation. Feeding strategies can be used to limit fattening of cows with no or short dry period, but the studied feeding strategies did not increase lactation persistency. Improved fertility and behavioural changes around calving suggest a better adaptation to a new lactation in case of no dry period. Customised dry period lengths for individual cows could improve metabolic status of cows at risk of a severe negative energy balance while minimising milk losses.

Natural autoantibodies (NAAb) have a role in maintaining physiological homeostasis and prevention of infections, and have been found in mammalian species tested so far. Albeit NAAb levels rise with age, little is known about the origin, function, regulation and initiation of NAAb in young animals. The present study addressed the presence of IgM and IgG NAAb binding glutamate dehydrogenase (GD), carbonic anhydrase (CA), myosin (MYO) and transferrin (TRANS) from before drinking colostrum until the first 12 weeks of life in plasma of female calves. In addition, NAAb to these four self-antigens were also measured in colostrum and in plasma of their mothers during three weeks before calving. Titers of NAAb binding GD, CA, MYO and TRANS were detected in plasma of cows before calving, in colostrum, and in plasma of calves before and after drinking of colostrum. Levels of NAAb in colostrum were positively related with levels of NAAb in plasma of cows. Before colostrum intake, levels of NAAb in plasma of calves were not related with levels of NAAb in plasma of their mother but were influenced by parity of their mother. After colostrum intake, levels of NAAb in plasma of calves in the first week of life were positively related with levels of NAAb in colostrum. Low NAAb levels in colostrum were related with low NAAb in plasma of calves in the first week of life, but after two weeks of life the relation between colostrum and plasma of calves was absent. In conclusion, NAAb are already present in the unborn calf, and levels of neonatal NAAb during the early weeks of life are affected by levels of maternal NAAb obtained via colostrum.

To compare milk yields between cows or management strategies, lactations are traditionally standardized to 305-d yields. The 305-d yield, however, gives no insight into the combined effect of additional milk yield before calving, decreased milk yield after calving, and a possible shorter calving interval in the case of a shortened dry period. We aimed to develop a measure that would enable the comparison of milk yield between cows with different dry period (DP) lengths. We assessed the importance of accounting for additional milk yield before calving and for differences in calving interval. The 305-d yield was compared with a 365-d yield, which included additional milk yield in the 60 d before calving. Next, an effective lactation yield was computed, defined as the daily yield from 60 d before calving to 60 d before the next calving, to account for additional milk yield before calving and for differences in calving interval. Test-day records and drying-off dates of 15 commercial farms were used to compute the 305-d, 365-d, and effective lactation yields for individual cows. We analyzed 817 second-parity lactations preceded by no DP, a short DP (20 to 40 d), or a conventional DP (49 to 90 d). Compared with cows with a conventional DP, the 305-d yield of cows with no DP was 7.0 kg of fat- and protein-corrected milk (FPCM) per day lower, and the 305-d yield of cows with a short DP was 2.3 kg of FPCM per day lower. Including additional milk yield before calving in the 365-d yield reduced this difference to 3.4 kg of FPCM per cow per day for cows with no DP and to 0.9 kg of FPCM per cow per day for cows with a short DP. Compared with cows with a conventional DP, median days open were reduced by 25 d for cows with no DP and by 18 d for cows with a short DP. Accounting for these differences in calving interval in the effective lactation yield further decreased yield reductions for cows with no DP or a short DP by 0.3 kg of FPCM per cow per day. At the herd level, estimated 365-d yield losses for cows with no DP or a short DP differed from effective lactation yield losses by 0.4 to -0.8 kg FPCM per cow per day. Accounting for additional milk yield before calving had a major and consistent effect on yield comparisons of cows with different DP lengths. The effect of correcting for calving interval was more variable between farms and will especially be important when calving interval is affected by DP length.

In early lactation, dairy cows typically have a negative energy balance which has been related to metabolic disorders, compromised health and fertility, and reduced productive lifespan. Assessment of the energy balance, however, is not easy on the farm. Our aims were to investigate the milk metabolic profiles of dairy cows in early lactation, and to obtain models to estimate energy balance from milk metabolomics data and milk production traits. Milk samples were collected in week 2 and 7 after calving from 31 dairy cows. For each cow, the energy balance was calculated from energy intake, milk production traits and body weight. A total of 52 milk metabolites were detected using LC-QQQ-MS. Data from different lactation weeks was analysed by partial least squares analysis, the top 15 most relevant variables from the metabolomics data related to energy balance were used to develop reduced linear models to estimate energy balance by forward selection regression. Milk fat yield, glycine, choline and carnitine were important variables to estimate energy balance (adjusted R2: 0.53 to 0.87, depending on the model). The relationship of these milk metabolites with energy balance is proposed to be related to their roles in cell renewal. ispartof: Scientific reports vol:8 issue:1 pages:1-11 ispartof: location:England status: published

The aim of this study was to assess the potential of milk fatty acids as diagnostic tool for hyperketonemia of 93 dairy cows in a 3×2 factorial arrangement. Cows were fed a glucogenic or lipogenic diet and originally were intended to be subjected to a 0-, 30-, or 60-d dry period. Nevertheless, some of the cows, which were intended for inclusion in the 0-d dry period group, dried off spontaneously. Milk was collected in wk 2, 3, 4, and 8 of lactation for milk fat analysis. Blood was sampled from wk 2 to 8 after parturition for β-hydroxybutyrate (BHBA) analysis. Cases were classified into 2 groups: hyperketonemia (BHBA ≥1.2mmol/L) and nonhyperketonemia (BHBA

The first objective of this study was to evaluate effects of dry period (DP) length and dietary energy source on ovarian activity, uterine health status, pregnancy rate, and days open in dairy cows in the second subsequent lactation after implementation of DP length and dietary treatments. The second objective was to determine relationships of uterine health status with ovarian activity, milk yield, energy balance (EB), and metabolic status in dairy cows. Holstein-Friesian dairy cows (n = 167) were assigned randomly to 1 of 3 DP lengths (0-, 30-, or 60-d) and 1 of 2 early lactation diets (glucogenic or lipogenic diet) for 2 subsequent lactations. Milk samples were collected three times a week. At least two succeeding milk samples with concentration of progesterone ≥2 ng/mL were used to indicate the occurrence of luteal activity. Vaginal discharge was scored in wk 2 and 3 after calving to evaluate uterine health status and cows were classified as having a healthy uterine environment [HU, vaginal discharge score (VDS) = 0 or 1 in both wk 2 and 3], a recovering uterine environment (RU, VDS = 2 or 3 in wk 2 and VDS = 0 or 1 in wk 3), or a non-recovering uterine environment (NRU, VDS = 2 or 3 in wk 3). Cows were monitored for milk yield, dry matter intake (DMI), and blood was sampled weekly to determine metabolic status from calving to wk 3 postcalving. Dry period length was not related with uterine health status in early lactation, pregnancy rate, or days open in dairy cows. Independent of DP length, feeding a glucogenic diet shortened the interval from calving to onset of luteal activity (25.3 vs. 31.0 d, P = 0.04), but decreased pregnancy rate compared with a more lipogenic diet (68.2 vs. 78.1 d, P = 0.03). In the first 3 wk after calving, cows with a NRU had lower milk yield (36.8 vs. 36.8 vs. 32.4 kg for cows with a HU, RU, or NRU, respectively; P < 0.01) and lower DMI than cows with a HU or RU. Cows with a RU had lower plasma glucose and insulin concentrations than cows with a NRU or HU. In conclusion, DP length did not influence fertility measures and uterine health status in the second subsequent lactation after implementation of DP length treatments. Independent of DP length, feeding a glucogenic diet leaded to earlier ovulation postcalving, but decreased pregnancy rate compared with a more lipogenic diet. In addition, a healthy uterine environment was related to greater milk yield and better metabolic status, independent of DP length.

Shortening or omitting the dry period (DP) can improve the energy balance of dairy cows in early lactation through a decrease in milk yield after calving. Little is known about the effect of a short or no DP on milk yield over multiple lactations. Our objectives were (1) to assess the effect of DP length over multiple lactations on milk yield, and (2) to assess if the prediction of milk yield in response to DP length could be improved by including individual cow characteristics before calving. Lactation data (2007 to 2015) of 16 Dutch dairy farms that apply no or short DP were used to compute cumulative milk yield in the 60 d before calving (additional yield) and in the 305 d after calving (305-d yield), and the mean daily yield over the interval from 60 d before calving to 60 d before next calving (effective lactation yield). The DP categories were no (0 to 2 wk), short (3 to 5 wk), standard (6 to 8 wk), and long (9 to 12 wk). The effect of current DP and previous DP on yields was analyzed with mixed models (n = 1,420 lactations). The highest effective lactation yield of fat-and-protein-corrected milk (FPCM) was observed for cows with a standard current DP (27.6 kg per day); a daily decrease was observed of 0.6 kg for a long DP, 1.0 kg for a short DP, and 2.0 kg for no DP. Previous DP did not significantly affect the effective lactation yield. Thus, cows can be managed with short or no DP over consecutive lactations without a change in quantity of milk losses. Cows that received no DP for consecutive lactations had a lower additional yield before calving (−172 kg of FPCM), but a higher 305-d yield (+560 kg of FPCM), compared with cows that received no DP for the first time. This could lessen the improvement of the energy balance in early lactation when no DP is applied a second time compared with the first time. For the second objective, a basic model was explored to predict effective lactation yield based on parity, DP length, and first-parity 305-d yield (n = 2,866 lactations). The basic model was subsequently extended with data about recent yield, days open, and somatic cell count. Extending the model reduced the error of individual predictions by only 6%. Therefore, the basic model seems sufficient to predict the effect of DP length on effective lactation yield. Other individual cow characteristics can still be relevant, however, to make a practical and tailored decision about DP length.

Breeding values for dry matter intake (DMI) are important to optimize dairy cattle breeding goals for feed efficiency. However, generally, only small data sets are available for feed intake, due to the cost and difficulty of measuring DMI, which makes understanding the genetic associations between traits across lactation difficult, let alone the possibility for selection of breeding animals. However, estimating national breeding values through cheaper and more easily measured correlated traits, such as milk yield and liveweight (LW), could be a first step to predict DMI. Combining DMI data across historical nutritional experiments might help to expand the data sets. Therefore, the objective was to estimate genetic parameters for DMI, fat- and protein-corrected milk (FPCM) yield, and LW across the entire first lactation using a relatively large data set combining experimental data across the Netherlands. A total of 30,483 weekly records for DMI, 49,977 for FPCM yield, and 31,956 for LW were available from 2,283 Dutch Holstein-Friesian first-parity cows between 1990 and 2011. Heritabilities, covariance components, and genetic correlations were estimated using a multivariate random regression model. The model included an effect for year-season of calving, and polynomials for age of cow at calving and days in milk (DIM). The random effects were experimental treatment, year-month of measurement, and the additive genetic, permanent environmental, and residual term. Additive genetic and permanent environmental effects were modeled using a third-order orthogonal polynomial. Estimated heritabilities ranged from 0.21 to 0.40 for DMI, from 0.20 to 0.43 for FPCM yield, and from 0.25 to 0.48 for LW across DIM. Genetic correlations between DMI at different DIM were relatively low during early and late lactation, compared with mid lactation. The genetic correlations between DMI and FPCM yield varied across DIM. This correlation was negative (up to -0.5) between FPCM yield in early lactation and DMI across the entire lactation, but highly positive (above 0.8) when both traits were in mid lactation. The correlation between DMI and LW was 0.6 during early lactation, but decreased to 0.4 during mid lactation. The highest correlations between FPCM yield and LW (0.3-0.5) were estimated during mid lactation. However, the genetic correlations between DMI and either FPCM yield or LW were not symmetric across DIM, and differed depending on which trait was measured first. The results of our study are useful to understand the genetic relationship of DMI, FPCM yield, and LW on specific days across lactation.

Most cows encounter a state of negative energy balance during the periparturient period, which may lead to metabolic disorders and impaired fertility. The aim of this study was to assess the potential of milk fatty acids as diagnostic tools of detrimental levels of blood plasma nonesterified fatty acids (NEFA), defined as NEFA concentrations beyond 0.6 mmol/L, in a data set of 92 early lactating cows fed a glucogenic or lipogenic diet and subjected to 0-, 30-, or 60-d dry period before parturition. Milk was collected in wk 2, 3, 4, and 8 (n = 368) and blood was sampled weekly from wk 2 to 8 after parturition. Milk was analyzed for milk fatty acids and blood plasma for NEFA. Data were classified as "at risk of detrimental blood plasma NEFA" (NEFA ≥ 0.6 mmol/L) and "not at risk of detrimental blood plasma NEFA" (NEFA

The objective of this study was to evaluate the effects of dry period length and dietary energy source in early lactation on milk production, feed intake, and energy balance (EB) of dairy cows. Holstein-Friesian dairy cows (60 primiparous and 108 multiparous) were randomly assigned to dry period lengths (0, 30, or 60 d) and early lactation ration (glucogenic or lipogenic), resulting in a 3 × 2 factorial design. Rations were isocaloric and equal in intestinal digestible protein. The experimental period lasted from 8 wk prepartum to 14 wk postpartum and cows were monitored for milk yield, milk composition, dry matter intake (DMI), energy balance, and milk fat composition. Prepartum average milk yield for 60 d precalving was 13.8 and 7.7 ± 0.5 kg/d for cows with a 0- and 30-d dry period, respectively. Prepartum DMI and energy intake were greater for cows without a dry period and 30-d dry period, compared with cows with a 60-d dry period. Prepartum EB was greater for cows with a 60-d dry period. Postpartum average milk yield until wk 14 was lower for cows without a dry period and a 30-d dry period, compared with cows with a 60-d dry period (32.7, 38.7, and 43.3 ± 0.7 kg/d for 0-, 30-, and 60-d dry period, respectively). Postpartum DMI did not differ among treatments. Postpartum EB was greater for cows without a dry period and a 30-d dry period, compared with cows with a 60-d dry period. Young cows (parity 2) showed a stronger effect of omission of the dry period, compared with a 60-d dry period, on additional milk precalving (young cows: 15.1 kg/d; older cows: 12.0 kg/d), reduction in milk yield postcalving (young cows: 28.6 vs. 34.8 kg/d; older cows: 41.8 vs. 44.1 kg/d), and improvement of the EB postcalving (young cows: 120 vs. -93 kJ/kg(0.75)·d; older cows: -2 vs. -150 kJ/kg(0.75)·d. Ration did not affect milk yield and DMI, but a glucogenic ration tended to reduce milk fat content and increased EB, compared with a more lipogenic ration. Reduced dry period length (0 and 30 d) increased the proportion of short- and medium-chain fatty acids in milk fat and omitting the dry period decreased the proportion of long-chain fatty acids in milk fat. In conclusion, shortening and omitting the dry period shifts milk yield from the postpartum to the prepartum period; this results in an improvement of the EB in early lactation. An increased energy status after a short dry period can be further improved by feeding a more glucogenic ration in early lactation.

A dry period of 6–8 weeks for dairy cows is generally thought to maximise milk production in the next lactation. However, the value of such a long dry period is increasingly questioned. In particular, shortening the dry period shifts milk production from the critical period after calving to the weeks before calving. This shift in milk production could improve the energy balance (EB), health and fertility of dairy cows. The objective of this study was to systematically review the current knowledge on dry period length in relation to milk production, EB, fertility, and health of cows and calves. A meta-analysis was performed for variables where at least five studies were available. Overall, both shortening and omitting the dry period reduces milk production, increases milk protein percentage and tends to reduce the risk of ketosis in the next lactation. Individual studies reported an improvement of EB after a short or no dry period, compared with a conventional dry period. Shortening or omitting the dry period did not affect milk fat percentage and shortening the dry period did not alter the odds ratio for mastitis, metritis, or fertility measures in the next lactation. So, current evidence for an improvement of health and fertility of dairy cows is marginal and may be partly explained by the limited number of studies which have evaluated health and fertility in relation to dry period length, the limited number of animals in those studies and the variable responses reported.

The early lactation period of dairy cows, which produce high quantities of milk, is normally characterized by an insufficient energy intake to cover milk production and maintenance requirements. Mobilization of body reserves occurs to compensate this negative energy balance (NEB), and probably as a consequence there is a higher susceptibility to diseases and metabolic disorders. There are several diagnostic methods to detect NEB, usually involving ketosis related parameters. Due to the easy availability of milk this is a preferred matrix, but simple and robust predictors of NEB level are missing. To better understand the physiological mechanism of NEB, milk of cows subjected to different dry period lengths, in different energy balance status and lactation stage, were analyzed by untargeted metabolomics and proteomics techniques. Milk of cows in severe NEB showed higher concentrations of acute phase response proteins, unsaturated fatty acids, and galactose-1-phosphate. Improved energy balance (EB) resulted in higher concentration of cholesterol, cholesterol synthesis related proteins, and stomatin. The presence of stomatin and galactose-1-phosphate in milk was strongly dependent on the EB of the cows. These novel and interesting findings warrant more in-depth research to assess their applicability as robust indicators of NEB in milk and to clarify the role of stomatin and galactose-1-phophate in milk of dairy cows in NEB.

Negative energy balance in dairy cows in early lactation has been associated with increased inflammation and oxidative stress in these cows. The objective of this study was to evaluate the effects of dry period (DP) length and dietary energy source on inflammatory biomarkers and oxidative stress in dairy cows. Holstein-Friesian dairy cows (60 primiparous and 107 multiparous) were assigned randomly to a 3 × 2 factorial design with 3 DP length (0, 30, or 60 d) and 2 early lactation rations (glucogenic or lipogenic). Cows were fed a glucogenic or lipogenic ration from 10 d before the expected calving date. Blood was collected in wk -3, -2, -1, 1, 2, and 4 relative to calving. Dry period length affected inflammatory biomarkers and oxidative stress, especially in wk 1 and 2 after calving. Cows with a 0-d DP had higher levels of ceruloplasmin, cholesterol, and reactive oxygen metabolites, and they tended to have higher haptoglobin levels compared with cows with a 30- or 60-d DP. Cows with a 0-d DP had a lower plasma paraoxonase and bilirubin in the first 2 wk after calving and a lower liver functionality index compared with cows with a 60-d DP. Cows of parity >3 fed a glucogenic ration had higher cholesterol levels compared with cows of parity >3 fed a lipogenic ration. No interaction between DP length and ration was present for inflammatory biomarkers or oxidative stress variables. Plasma bilirubin levels for cows with a 0-d DP were negatively related to energy balance and metabolic status in these cows. Moreover, occurrence of clinical health problems (fever, mastitis, metritis, and retained placenta) was 41, 27, and 30% for cows with 0-, 30-, and 60-d DP, respectively. High levels of ceruloplasmin, cholesterol, and reactive oxygen metabolites in cows with 0-d DP were related to the occurrence of health problems in these cows. In conclusion, omitting the DP increased levels of ceruloplasmin, cholesterol, and reactive oxygen metabolites, and decreased levels of bilirubin and paraoxonase in plasma, independent of ration, compared with cows with a 60-d DP. These contrasting effects of DP length on inflammatory status could be explained in part by the improved energy balance and occurrence of health problems in these cows, but was not related to increased somatic cell count in cows with a 0-d DP. Cows with a 0-d DP had better energy balance, but also had higher levels of oxidative stress compared with cows with a 60-d DP. Moreover, occurrence of health problems did not differ between cows with different DP lengths.

Shortening or omitting the dry period (DP) improves energy balance (EB) in early lactation because of a reduction in milk yield. Lower milk yield results in lower energy demands and requires less energy intake. The aim of this study was to evaluate the effects of DP length and concentrate level postpartum on milk yield, feed intake, EB, and plasma metabolites between wk -4 and 7 relative to calving of cows of second parity or higher. Holstein-Friesian dairy cows (n = 123) were assigned randomly to 1 of 2 DP lengths: 0-d DP (n = 81) or 30-d DP (n = 42). Prepartum, cows with a 0-d DP received a lactation ration based on grass silage and corn silage (6.4 MJ of net energy for lactation/kg of dry matter). Cows with a 30-d DP received a dry cow ration based on grass silage, corn silage, and straw (5.4 MJ of net energy for lactation/kg of dry matter). Postpartum, all cows received the same basal lactation ration as provided to lactating cows prepartum. Cows with a 0-d DP were fed a low level of concentrate up to 6.7 kg/d based on the requirement for their expected milk yield (0-d DP-L; n = 40) or the standard level of concentrate up to 8.5 kg/d (0-d DP-S; n = 41), which was equal to the concentrate level for cows with a 30-d DP (30-d DP-S; n = 42) based on requirements for their expected milk yield. Prepartum dry matter intake, concentrate intake, basal ration intake, energy intake, plasma β-hydroxybutyrate (BHB), and insulin concentrations were greater and plasma free fatty acids (FFA) and glucose concentrations were lower, but EB was not different in cows with a 0-d DP compared with cows with a 30-d DP. During wk 1 to 3 postpartum, milk fat yield and plasma BHB concentration were lower and dry matter intake and concentrate intake were greater in cows with a 0-d DP compared with cows with a 30-d DP. During wk 4 to 7 postpartum, fat- and protein-corrected milk (FPCM), lactose content, and lactose and fat yield were lower in 0-d DP-L or 0-d DP-S cows compared with 30-d DP-S cows. Basal ration intake, EB, body weight, plasma glucose, and insulin and insulin-like growth factor-1 concentrations were greater and plasma FFA and BHB concentrations were lower in 0-d DP-L and 0-d DP-S cows compared with 30-d DP-S cows. Concentrate and energy intake were lower in 0-d DP-L cows than in 0-d DP-S or 30-d DP-S cows. Milk yield and concentrations of plasma metabolites did not differ in wk 4 to 7, although EB was lower in wk 6 and 7 postpartum in 0-d DP-L cows than in 0-d DP-S cows. In conclusion, a 0-d DP reduced milk yield and improved EB and metabolic status of cows in early lactation compared with a 30-d DP. Reducing the postpartum level of concentrate of cows with a 0-d DP did not affect fat- and protein-corrected milk yield or plasma FFA and BHB concentrations in early lactation but did reduce EB in wk 6 and 7 postpartum.

The objective of the current study was to evaluate the effect of dry period (DP) length on milk yield, energy balance (EB), and metabolic status in cows fed a lipogenic or glucogenic diet in the second year after implementation of DP and dietary treatments. Holstein-Friesian dairy cows (n=167) were assigned randomly to 1 of 3 DP lengths (0, 30, or 60d) and 1 of 2 early lactation diets (glucogenic or lipogenic) for 2 consecutive years. Results of the first year were reported previously. In the second year, 19 cows in the 0-d DP group were attributed to a new group (0→67d DP) because these cows had a milk yield of

This study evaluated the effects of dry period (DP) length and dietary energy source on lactation curve characteristics over 2 subsequent lactations. It also evaluated the relationships of energy balance or metabolic status in early lactation with lactation curve characteristics in dairy cows. Holstein-Friesian dairy cows (n = 167) were assigned randomly to 1 of 3 DP lengths (0-, 30-, or 60-d) and 1 of 2 early-lactation diets (glucogenic or lipogenic) for 2 subsequent lactations. In the second lactation following DP length treatments, 19 cows in the 0-d DP group were assigned to a 0→67-d DP group (actual days dry: 67 ± 8 d). Cows were allocated to this new group when they had a milk yield of 2 cows, total FPCM yield and average daily FPCM yield throughout 2 lactations did not differ among DP lengths. In addition, average energy balance in the first 4 wk after calving had a negative relationship with peak yield and FPCM305, and a positive relationship with lactation persistency. Average plasma concentrations of free fatty acids and β-hydroxybutyrate had a positive relationship with peak yield and FPCM305, and a negative relationship with lactation persistency. Shortening or omitting the DP affected lactation curve characteristics in both lactations after implementation of DP length treatments but did not compromise FPCM yield compared with a conventional DP of 60 d in parity >2 cows. Severe negative energy balance and poor metabolic status were related to greater peak yield, FPCM305, and lower lactation persistency.

Shortening or omitting the dry period (DP) in dairy cows is of interest because of potential beneficial effects on energy balance and metabolic health. Reported effects of a short or omitted dry period on udder health are ambiguous. This study aimed to evaluate the effect of no DP (0 d), a short DP (30 d), or a conventional DP (60 d) on the occurrence of intramammary infections (IMI) during the precalving period and on somatic cell counts (SCC), elevations of SCC (SCC ≥ 200,000 cells/mL), and clinical mastitis in the subsequent lactation. The study also aimed to analyze which prepartum cow characteristics are associated with udder health after different DP lengths. Holstein-Friesian dairy cows (n = 167) were randomly assigned to a DP length (0, 30, or 60 d). Cows with a 0-d DP had a greater occurrence of chronic IMI and a lower occurrence of cured IMI during the precalving period than cows with a 30-d or 60-d DP. Postpartum average SCC for lactation was greater in cows with a 0-d DP than in cows with a 30-d or 60-d DP. The number of cows with at least 1 elevation of SCC, the number of elevations of SCC per affected cow, the number of cows treated for clinical mastitis, and the number of cases of mastitis per affected cow did not differ among DP lengths. Cow characteristics related to postpartum average SCC for lactation were DP length, parity, and the following interactions: DP length with prepartum elevation of SCC, DP length with fat- and protein-corrected milk (FPCM) reduction between 150 and 67 d prepartum, DP length with parity and with average SCC for lactation, and last FPCM before the conventional drying-off day with average SCC for lactation. Cows with prepartum parity 1 had a lower occurrence of at least 1 elevation of SCC in subsequent lactation compared with cows with parity >2. Last SCC before the conventional drying-off day was positively associated with occurrence of clinical mastitis in the subsequent lactation. In this study, DP length was not a risk factor for either elevation of SCC or occurrence of clinical mastitis in the subsequent lactation. The identified cow characteristics could be used in a decision support model to optimize DP length for individual cows.

Natural antibodies (NAb) are defined as antibodies that circulate in normal healthy individuals under the absence of deliberate antigenic stimulation. Two types of NAb are distinguished: NAb towards exogenous antigens and NAb towards autoantigens (N(A)Ab). The objectives of the current study were threefold. First, we studied the relation between metabolic health and concentrations of NAb binding keyhole limpet hemocyanin (KLH) or lipopolysaccharide (LPS) in milk and plasma of dairy cows in early lactation. Second, we determined the presence of N(A)Ab binding transferrin, myosin and thyroglobulin in bovine milk. Third, we studied the relation between N(A)Ab in bovine milk and mammary health. For the first objective, dairy cows were either fed a control (C) (n = 8) or a diet where 2 kg of concentrates were replaced by an iso-energetic concentrate containing marine algae (ALG) from week −3 till 8 postpartum (experiment 1). Plasma and milk samples were analyzed weekly for NAb binding either KLH or LPS. Plasma was analyzed for glucose, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA). For the second and third objective, milk samples were collected weekly from 96 dairy cows from week 2 till 9 postpartum and analyzed for milk composition and N(A)Ab binding myosin, transferrin and thyroglobulin (experiment 2). For both datasets, N(A)Ab titers are expressed as 2log values of the highest dilution giving a positive reaction. Data are expressed as means ± SEM. Repeated observations were analyzed in a mixed model. In experiment 1, no diet effect (P > 0.05) was observed on NAb binding LPS in plasma or milk, NAb binding KLH in milk was greater (P = 0.05) for cows fed the control diet. Concentration of NAb binding KLH and LPS in plasma was negatively related to plasma NEFA concentration (P

The objective of this study was to evaluate Fourier transform infrared (FTIR) spectrometry to measure milk ketone bodies to detect hyperketonemic cows and compare this method with milk fat to protein ratio to detect hyperketonemia. Plasma and milk samples were obtained weekly from calving to wk 9 postpartum from 69 high-producing dairy cows. The reference test for hyperketonemia was defined as plasma concentration of β-hydroxybutyrate (BHBA) ≥1,200μmol/L. The weekly prevalence of hyperketonemia during the first 9 wk of lactation was, on average, 7.1%. Both BHBA and acetone in milk, determined by FTIR, had a higher sensitivity (80%) to detect hyperketonemia compared with milk fat to protein ratio (66%). Specificity was similar for the 3 diagnostic tests (71, 70, and 71%). In conclusion, FTIR predictions of BHBA or acetone in milk can detect cows with hyperketonemia in early lactation with a higher accuracy compared with the use of milk fat to protein ratio. Because of the high proportion of false-positive tests, there are concerns about the practical applicability of FTIR predictions of acetone, BHBA, and fat to protein ratio in milk to detect hyperketonemic cows.

Item does not contain fulltext OBJECTIVES: To compare the preverbal communication skills of two groups of young implanted children: those with unilateral implantation and those with bilateral implantation. MATERIAL AND METHODS: The study assessed 69 children: 42 unilaterally and 27 bilaterally implanted with age at implantation less than 3 years. The preverbal skills of these children were measured before and 1 year after implantation, using Tait Video Analysis that has been found able to predict later speech outcomes in young implanted children. RESULTS: Before implantation there was no significant difference between the unilateral group and the bilateral group. There was still no difference at 12 months following implantation where vocal autonomy is concerned, but a strongly significant difference between the groups for vocal turn-taking and non-looking vocal turns, the bilateral group outperforming the unilateral group. Regarding gestural turn-taking and gestural autonomy, there was a strongly significant difference between the two groups at the 12 month interval, and also a difference before implantation for gestural autonomy, the unilateral group having the higher scores. Multiple regression of non-looking vocal turns revealed that 1 year following implantation, bilateral implantation contributed to 51% of the variance (p

This paper summarizes three recent studies by the same authors with the objective to study the effect of dietary energy source on the energy balance (EB) and risk for metabolic and reproductive disorders in dairy cows in early lactation. The first study, a literature survey, illustrated that feeding extra glucogenic nutrients relative to lipogenic nutrients, decreased milk fat and seems to decrease plasma non-esterified fatty acid (NEFA) and beta-hydroxybutyrate (BHBA) concentration. However studies are scarce and mostly confound the effect of energy source with level of energy intake, compromising eventual effects on EB and fertility. Therefore, in the second study, 16 dairy cows were either fed a glucogenic or a lipogenic diet (isocaloric) and EB was determined in climate-controlled respiration chambers from week 2 until 9 of lactation. Glucogenic diet decreased milk fat yield and milk energy and tended to decrease body fat mobilization compared with lipogenic diet. The objective of the third study was to study the effect of dietary energy source on EB, metabolites and reproduction variables. Dairy cows (n=111) were fed glucogenic, lipogenic or mixed diet from week 3 until week 9 relative to calving. Multiparous cows fed glucogenic diet had lower milk fat yield, higher calculated EB, and lower plasma NEFA, BHBA and liver triacylglyceride concentration and tended to have fewer days to first postpartum ovulation. In conclusion, increasing the glucogenic nutrient availability improved the EB and had potential to reduce the risk for metabolic disorders and to improve reproductive performance in dairy cows.

Increasing the availability of glucogenic nutrients relative to lipogenic nutrients has been hypothesized to decrease the production of milk fat, to improve the energy balance (EB), and to decrease the incidence and severity of metabolic and reproductive disorders in dairy cows in early lactation. Therefore, our objective was to evaluate the effects of a glucogenic, lipogenic, or mixed diet on EB, plasma metabolites and metabolic hormones, liver triacylglycerides (TAG), and reproductive variables in high-producing dairy cows in early lactation. Cows (n = 114) were randomly assigned to 1 of 3 diets and were fed either a mainly lipogenic diet, a mainly glucogenic diet, or a mixture of both diets (50:50 dry matter basis) from wk 3 before the expected calving date until 9 wk postpartum. Diets were isocaloric (net energy basis) and equal in intestinal digestible protein. Dry matter intake, net energy intake, milk yield, and milk protein percentage did not differ among diets. Milk lactose percentage was less for cows fed the lipogenic diet. Milk fat percentage was less for multiparous cows fed the glucogenic diet compared with cows fed the mixed or lipogenic diet (3.69 vs. 4.02 vs. 4.22 +/- 0.07%, respectively). The calculated EB was less negative for multiparous cows fed the glucogenic diet compared with cows fed the mixed or lipogenic diet [-33 vs. -125 vs. -89 +/- 21 kJ/(kg(0.75) x d), respectively]. Postpartum, the glucogenic diet decreased plasma nonesterified fatty acids, beta-hydroxybutyrate, and liver TAG concentrations and increased insulin concentration in multiparous cows. The glucogenic diet tended to decrease the number of days until first milk progesterone rise in multiparous cows compared with the mixed or lipogenic diet (20.4 vs. 24.4 vs. 26.4 +/- 2.1 d, respectively). Diet had no effect on any of the above-mentioned variables in primiparous cows, except that milk lactose percentage was greater for primiparous cows fed the glucogenic diet. We concluded that the glucogenic diet was effective in improving the calculated EB and decreasing plasma beta-hydroxybutyrate and liver TAG concentrations, suggesting a reduced risk of metabolic disorders in multiparous dairy cows fed a glucogenic diet.

The objectives of the present study were to evaluate the effects of dry period length on ovarian activity in cows fed a lipogenic or a glucogenic diet within 100 days in milk (DIM) and to determine relationships between ovarian activity and energy balance and metabolic status in early lactation. Holstein-Friesian dairy cows (n = 167) were randomly assigned to one of three dry period lengths (0, 30, or 60 days) and one of two diets in early lactation (glucogenic or lipogenic diet) resulting in a 3 × 2 factorial design. Cows were monitored for body condition score, milk yield, dry matter intake, and energy balance from calving to week 8 postpartum, and blood was sampled weekly from 95 cows from calving to week 8 postpartum. Milk samples were collected three times a week until 100 DIM postpartum for determination of progesterone concentration. At least two succeeding milk samples with progesterone concentration of 2 ng/mL or greater were used to indicate the occurrence of luteal activity. Normal resumption of ovarian cyclicity was defined as the onset of luteal activity (OLA) occurring at 45 DIM or less, followed by regular ovarian cycles of 18 to 24 days in length. Within 100 DIM postpartum, cows with a 0-day dry period had greater incidence of normal resumption of ovarian cyclicity (53.2%; 25 out of 47 cows) compared with cows with a 60-day dry period (26.0%; 13 out of 50 cows, P = 0.02). Independent of dry period length or diet, cows with OLA at less than 21 DIM had a greater body condition score during weeks 1 and 2 (P = 0.01) and weeks 1 through 8 (P = 0.01) postpartum compared with cows with OLA at greater than 30 DIM. Cows with the first ovarian cycle of medium length (18-24 days) had greater energy balance (P = 0.03), plasma concentrations of insulin (P = 0.03), glucose (P = 0.04), and insulin-like growth factor I (P = 0.04) than cows with long ovarian cycle lengths (24 days) but had lower plasma β-hydroxybutyrate (P 0.01) and liver triacylglycerol (P = 0.02) concentrations than cows with short ovarian cycle lengths (18 days) during weeks 1 through 8 postpartum. Diet did not affect the measured ovarian activity variables within 100 DIM. In conclusion, omitting the dry period (0 days) increased the incidence of normal resumption of ovarian cyclicity in dairy cows within 100 DIM compared with a conventional dry period (60 days). Short (18 days) or long (24 days) ovarian cycles during the first ovarian cycle postpartum were associated with severe negative energy balance and poor metabolic status in early lactation.

The aim of this study was to evaluate the effect of shortening or omitting the dry period of dairy cows on milk casein composition. For this study, we analyzed milk samples of 90 cows with a dry period of 0, 30, or 60 d and either a glucogenic or a lipogenic ration in early lactation. Milk was sampled at 6 and 2 wk prepartum and at 2, 6, and 12 wk postpartum. Milk was analyzed for casein (CN) composition by capillary zone electrophoresis, and isoforms of κ-CN were measured by reversed phase-HPLC. Shortening the dry period from 60 to 30 d reduced the αS1-CN fraction by 3.8% and increased the αS2-CN fraction by 5.5%. In milk from cows with a 0-d dry period, the glycosylated κ-CN fraction in late lactation increased from 8 to 12% between 6 and 2 wk prepartum. After calving, the glycosylated κ-CN fraction in milk was higher for cows with a 0-d dry period (6.7%) compared with cows with a 60-d dry period (5.2%). The glycosylated κ-CN fraction at 2 wk postpartum was negatively correlated with milk yield, suggesting that glycosylation was related to reduced productivity of mammary epithelial cells. In early lactation, the β-CN fraction was reduced in milk of cows with a 0-d dry period. A lowered β-CN fraction was associated with high somatic cell count and greater parity, indicating that it was the result of proteolytic activity. In conclusion, casein composition changes that result from shortening the dry period from 60 to 30 d are not expected to affect processing characteristics of milk. Applying a 0-d dry period may affect processability of milk because of a higher glycosylated κ-CN fraction, and possibly because of higher proteolytic activity compared with a 60-d dry period.

In a prior study, we observed that cows with a 0-d dry period had greater energy balance and lower milk production compared with cows with a 30- or 60-d dry period in early lactation. The objective of the current study was to evaluate the influence of dry period length on metabolic status and hepatic gene expression in cows fed a lipogenic or glucogenic diet in early lactation. Holstein-Friesian dairy cows (n = 167) were assigned randomly to 3 × 2 factorial design with 3 dry period lengths (n = 56, 55, and 56 for 0-, 30-, and 60-d dry, respectively) and 2 early lactation diets (n = 84 and 83 for glucogenic and lipogenic diet, respectively). Cows were fed a glucogenic or lipogenic diet from 10 d before the expected calving date and onward. The main ingredient for a glucogenic concentrate was corn, and the main ingredients for a lipogenic concentrate were sugar beet pulp, palm kernel, and rumen-protected palm oil. Blood was sampled weekly from 95 cows from wk 3 precalving to wk 8 postcalving. Liver samples were collected from 76 cows in wk -2, 2, and 4 relative to calving. Liver samples were analyzed for triacylglycerol concentrations and mRNA expression of 12 candidate genes. Precalving, cows with a 0-d dry period had greater plasma ß-hydroxybutyrate, urea, and insulin concentrations compared with cows with a 30- or 60-d dry period. Postcalving, cows with a 0-d dry period had lower liver triacylglycerol and plasma nonesterified fatty acids concentrations (0.20, 0.32, and 0.36 mmol/L for 0-, 30-, and 60-d dry period, respectively), greater plasma glucose, insulin-like growth factor-I, and insulin (24.38, 14.02, and 11.08 µIU/mL for 0-, 30-, and 60-d dry period, respectively) concentrations, and lower hepatic mRNA expression of pyruvate carboxylase, compared with cows with a 30- or 60-d dry period. Plasma urea and ß-hydroxybutyrate concentrations were greater in cows fed a lipogenic diet compared with cows fed a glucogenic diet. In conclusion, cows with a 0-d dry period had an improved metabolic status in early lactation, indicated by lower plasma concentrations of nonesterified fatty acids, greater plasma concentrations of glucose, insulin-like growth factor-I, and insulin, and lower mRNA expression of pyruvate carboxylase in the liver, compared with cows with a 30- or 60-d dry period. Independent of dry period length, the glucogenic diet also improved the metabolic status compared with the lipogenic diet.

The objective was to study the effect of dry period length in dairy cows on immunoglobulin content and natural antibodies (NAb) titers in colostrum, growth, and plasma natural and specific antibody titers in plasma of calves. Holstein-Friesian dairy cows (n = 167) were randomly assigned to 3 dry period lengths (0, 30, or 60 d). Colostrum production, concentration of colostrum IgG and IgM, and titers of NAb (isotypes IgG and IgM) binding keyhole limpet hemocyanin (KLH) and human serum albumin (HuSA) in colostrum were measured. Female calves were immunized with both KLH and HuSA at wk 6 and 10 of life. Titers of NAb and specific antibody (SpAb) for isotypes IgG, IgM, and total immunoglobulin (IgT) binding KLH or HuSA were determined in plasma of female calves. Primary and secondary antibody responses to KLH or HuSA from wk 6 and 10 were expressed as the increase in antibody titers to wk 10 and 11 of life after primary and secondary challenges, respectively. Pregnancy length for cows with a 0-d dry period was 3 d shorter compared with cows with a 30- or 60-d dry period. Birth weight of calves from cows with a 0-d dry period was lower compared with calves from cows with a 30-d dry period. Growth of calves until 12 wk of life was not affected by dry period length. Colostrum production and IgG and IgM concentration in colostrum were lower for cows with a 0-d dry period than a 60-d dry period. Natural IgG and IgM titers binding KLH or HuSA were lower in colostrum from cows with a 0-d dry period compared with cows with a 60-d dry period. Natural antibody titers (IgG, IgM, and IgT) binding KLH or HuSA in plasma were lower during the first 2 wk of life for calves from cows with a 0-d dry period compared with calves from cows with a 30- or 60-d dry period. After primary and secondary immunization of calves with KLH and HuSA, SpAb titers of calves were not affected by dry period length. After secondary immunization, the response of IgG and IgT binding KLH was higher in plasma of calves from cows with a 0-d dry period. The results of this study demonstrate that, although omission of the dry period of dairy cows leads to lower plasma NAb titers in calves during the first 2 wk of life, SpAb titers in calves were not affected and even the secondary antibody responses were enhanced compared with calves from cows with a 30- or 60-d dry period.

The pathway for oxidation of energy involves a balanced oxidation of C2 and C3 compounds. During early lactation in dairy cattle this C2/C3 ratio is out of balance, due to a high availability of lipogenic (C2) products and a low availability of glycogenic (C3) products relative of the C2 and C3 products required for milk production. This review compares studies which manipulated dietary energy source and shows that dietary energy source can affect the balance of the C2/C3 ratio, as indicated by plasma NEFA, Betta-hydroxybutyrate (BHBA) and glucose levels. It is shown that glycogenic nutrients increase glucose and insulin concentrations and decrease NEFA and BHBA plasma levels. Extra lipogenic nutrients elevate NEFA and BHBA and decrease plasma glucose concentrations. Lipogenic nutrients generally increase milk fat percentage and decrease milk protein percentage, suggesting a surplus of C2 compounds. The inverse is the case for feeding extra glycogenic nutrients, implying reduced deamination and oxidation of glycogenic amino acids. Feeding extra glycogenic nutrients improved the energy balance (EB), in contrast to ambiguous results of lipogenic nutrients on EB. Moreover, glycogenic feed may reduce the severity of ketosis and fatty liver, but increased the incidence of (sub)clinical acidosis. Since studies are scarce, it seems difficult to draw conclusions on the effects of dietary energy source on reproduction. However, lipogenic nutrients decrease glucose and increase NEFA and BHBA plasma levels. High plasma NEFA and BHBA and low plasma glucose levels are associated with decreased reproductive performance, which might imply the C2/C3 compound balance to be important for reproductive function.

Enhancing longevity by reducing involuntary culling and consequently increasing productive life and lifetime production of dairy cows is not only a strategy to improve a farm's profit, but is also related to improved animal welfare. High rates of involuntary culling in dairy cows are currently attributed to fertility problems, mastitis and locomotive disorders. Disease incidence is high in particular in the early-lactation period. The high disease incidence in early lactation has been attributed to metabolic stress related to the high metabolic priority for lactation and the inability of the cow to adapt effectively to the new lactation. Several biological mechanisms interact in the peripartum period of dairy cows and can result in this inability to adapt effectively to lactation. Biological mechanisms reviewed are metabolic adaptation, oxidative stress, immune function and inflammation, and feed intake capacity. Although relationships between these mechanisms become increasingly clear, these relationships are complex and not yet completely understood. Appropriate management of dairy cows in the peripartum period can facilitate cows to adapt to a new lactation. Nutritional and management strategies to ease adaptation are divided into strategies to restrict energy intake in the dry period, to improve energy intake in early lactation, alter repartitioning of energy between milk and body tissue, and strategies to support fat or carbohydrate metabolism. The success of various strategies, however, is often hampered by the complexity of interactions and high between-cow variation. We advocate for a multidisciplinary approach to understand and manage adaptation to a new lactation aiming at an improvement of cow welfare and longevity.

The length of the dry period in commercial dairy production is under close scrutiny. While the main concern is the composition and volume of milk produced, the evaluation of colostrum quality under these new paradigms has suggested a decline in IgG concentrations, while some reports indicate no change. Colostrum quality has been defined as an adequate concentration (>50 mg/ml) of immunoglobulin in the secretions to provide the newborn with maximal disease resistance. We investigated the appearance of IgG in mammary pre- and post partum secretions in cows without a dry period (continuously milked, Dry0) and compared the secretions with cows that experienced a dry period of 60 d (Dry60). Blood was collected during the experimental period and plasma analysed for progesterone (P4) and prolactin (Prl). Approximately −6 d relative to parturition, the Dry0 animals exhibited increased concentration of IgG in their secretions to an average of ∼35 mg/ml that remained rather constant through subsequent pregnancy and following parturition. Dry0 cows were producing an average IgG concentration in parturition colostrum of 44·2±17·6 mg/ml that was not different than that of controls (66·86±16·8 mg/ml). However, Dry0 cows exhibited high variation, different peak times (day) of IgG concentration including times that occurred both pre and post parturition. IgG mass of the Dry0 cows remained rather constant pre- and post partum and did not show the same declining mass following parturition that was shown for the Dry60 cows. The change in plasma P4 and Prl were shown to have no timing effect on colostrum IgG concentration.