The objective of this study was to derive the estimated breeding values (EBVs) of Holstein sires for colostrum and passive transfer of immunity traits to (1) estimate the genetic association between these new traits and established production, conformation, and function, and (2) explore whether sires can be classified in specific profiles regarding the new traits. For cow colostrum traits, the study included 699 daughters of 67 sires from 6 commercial dairy herds. The number of daughters per sire ranged from 5 to 49. Passive transfer of immunity was measured as the blood serum total protein content in 854 purebred Holstein calves of 61 sires from 8 commercial dairy herds. The number of calves per sire ranged from 5 to 44. Data were statistically analyzed using mixed models. Approximate genetic correlations of the derived sire EBVs for cow colostrum and calf serum total protein with EBVs for several other traits were estimated. Moreover, sires were classified into colostrum and calf serum total protein profile groups. Approximate genetic correlations of cow colostrum and calf serum traits with milk production, conformation, and functional traits were mostly unfavorable. Colostrum TS and protein contents were negatively correlated with milk yield, fat yield, protein yield, productive life, and livability. The only favorable correlation found was between colostrum TS/calf serum total protein and daughter pregnancy rate. However, several bulls had favorable profiles in both colostrum/passive transfer of immunity and production traits. Colostrum/passive immunity traits could be included in future genetic improvement programs after careful structure of relevant indexes.

Due to the feeding system (high-concentrate diet) during the early lactation stage, ruminal pH in dairy cows follows a diurnal pattern and can remain below the critical level of 5.5 for extended periods of the day. This study aimed to evaluate the effect of low ruminal pH on blood concentrations of certain macrominerals, trace minerals, and fat-soluble vitamins and on the oxidative status of dairy cows during the first half of lactation. Fifty-three randomly selected lactating Holstein cows were used; blood and ruminal fluid samples were collected from all cows on days 30, 90 and 150 of lactation. Blood samples were obtained via coccygeal venipuncture, while the ruminal fluid was obtained by rumenocentesis and the pH was measured immediately after collection. Using a threshold pH of 5.5, samples were classified as normal (pH > 5.5) or low pH (pH ≤ 5.5). Serum concentrations of Ca, Mg, K, Cr, Mn, Zn, Se, and vitamins A, D3, E, and K were not significantly affected by ruminal pH, either by days in milk or by their interaction (p > 0.05). Plasma malondialdehyde and reduced glutathione followed the same trend (p > 0.05). Copper concentration was significantly higher (p < 0.05), and Fe concentration tended to be higher in cows with low pH compared to those with normal pH (p = 0.052). On day 150 of lactation, Cu, Fe, and Co concentrations were significantly higher in low-pH cows compared to normal-pH cows (p < 0.05). Low ruminal pH is associated with significant changes in serum concentrations of copper, iron, and cobalt but has no significant effect on the oxidative status of the animals or on the serum concentrations of the macro elements and fat-soluble vitamins studied.

BACKGROUND:Monitoring the metabolic changes during the periparturient period is crucial. OBJECTIVE:We aimed to establish reference intervals (RIs) of several serum and plasma biochemical variables in multiparous periparturient Holstein dairy cows. METHODS:A total of 238 multiparous dry cows from six commercial dairy farms were enrolled. Blood samples were collected at predetermined time points (21 and 7 days before the expected calving date, 7, 21, and 28 days after calving, ±2 days on all occasions). Samples from 113 cows that met the inclusion criteria were analyzed for plasma and serum biochemical analytes. RESULTS:The lower and upper reference limits were 40.9-49.3 and 102.8-128.5 U/L, respectively, for aspartate aminotransferase; 9.1-14.0 and 33.8-47.8 U/L for γ-glutamyl transferase; 0.07-0.13 and 0.20-0.43 mmol/L for triglycerides; 1.11-1.25 and 3.04-3.52 mmol/L for cholesterol; 0.0 and 3.42-7.78 μmol/L for total bilirubin; 141.0-285.0 and 778.6-1279.3 μmol/L for β-hydroxybutyrate, 0.07-0.22 and 0.42-1.24 mmol/L for non-esterified fatty acids; 50.8-59.7 and 77.4-103.5 g/L for total protein; 23.6-29.2 and 39.4-48.5 g/L for albumin; 19.4-28.3 and 42.0-58.3 g/L for globulin; 0.59-0.70 and 1.30-1.61 for albumin/globulin ratio; 1.3-3.2 and 7.6-9.7 mmol/L for blood urea nitrogen; 42.4-62.8 and 83.1-124.7 μmol/L for creatinine; 1.8-3.2 and 9.8-25.1 μmol/L for 3-methylhistidine; and 1.9-2.7 and 10.5-14.8 μmol/L for 1-methylhistidine. CONCLUSIONS:The established RIs provide valuable benchmarks with important clinical and research applications in dairy cattle medicine.

This prospective observational study aimed to investigate the association of rumen fill and motility in post-partum Holstein cows with their future reproductive performance and subclinical ketosis (SCK). The study population consisted of two independent data sets: the first (DS1) included 237 cows from 6 herds and the second one (DS2) 709 cows from 9 herds. Rumen Fill Score (RFS) was transformed into a 3 level-trait, representing very low, low and adequate dry matter intake, respectively. A binary Rumen Contraction Score (RCS) was defined as: 0: <2 contractions/2 min, impaired rumen motility and 1: ≥2 contractions/2 min, normal rumen motility. A combined binary trait based on RFS and RCS (RFCS) was also established, representing unsatisfactory and satisfactory rumen function. Three SCK traits were defined, based on 3 different thresholds, SCK_I: BHB≥1,000 mmol/L, SCK_II: BHB≥1,100 mmol/L and SCK_III: BHB≥1,200 mmol/L. Scores were assessed and blood samples collected on day 7 (DS1) or day 8 (DS2), postpartum. Kaplan-Meier survival analysis, multivariable Cox proportional hazards models and Generalized Linear Mixed Models were performed to evaluate the association of rumen and SCK traits with reproduction. Herd, parity, calving season and several postparturient diseases were also included as potential explanatory variables. Mean days from calving to pregnancy after the 1st artificial insemination (AI) and from calving to pregnancy (all AIs) were shorter for levels of rumen traits representing adequate DMI and normal rumen motility; in most cases these differences were statistically significant in both datasets. Cows with adequate DMI and normal rumen motility (only in DS2) had greater hazard (hazard ratio [HR] = 1.84 and 1.61, for RFS and RFCS, respectively) and odds (odds ratio [OR] = 2.49 and 1.98, for RFS and RFCS, respectively) for pregnancy at 1st AI. Assessment of the association of examined rumen traits with hazard and odds for pregnancy at all AIs yielded statistically significant results in both datasets. For RFS, RCS and RFCS, HRs ranged from 1.57 to 3.31 and ORs from 1.95 to 4.83. No statistically significant associations with hazard and odds for pregnancy at 1st or all AIs were detected, for any of the 3 SCK traits, in either dataset. Overall, the combined RFCS trait constantly identified more than twice the number of cows with future reproductive problems than a positive SCK blood test.

The aims of this study were to assess a) the variation of protein metabolism biomarkers and of factors affecting them during the transition period, b) the association of each biomarker with skeletal muscle reserves and their changes, and c) the association of these biomarkers with postpartum health, colostrum quality, reproduction, and milk production. For this purpose, 238 multiparous Holstein cows from 6 herds were used in a prospective cohort study. Plasma concentrations of 3-methylhistidine (3-MH) and 1-methylhistidine (1-MH) and serum concentrations of total protein (TP), albumin (ALB), urea nitrogen (BUN) and creatinine (SCR) were determined for each cow at −21d; −7d; 7d; 21d and 28d relative to calving. Clinical diseases were recorded during the first 28 d post-calving, and presence of subclinical ketosis (scKET) was investigated at 7d and 21d. Colostrum quality was estimated by Brix refractometry. Reproduction data by 150 d-in-milk (DIM) and milk production records were also available. Linear mixed models including the fixed effects of time point, herd, parity, body condition score (−21d), duration of dry period and post-parturient diseases were fitted to assess the variation in each biomarker's concentration. The association between the biomarkers' concentration during the pre-partum period with the odds for each post-parturient disease and for a combined trait (CD_1–28), defined as the presence of at least one clinical condition during the first 28 d after calving, were assessed with separate binary logistic models for time points −21d and −7d. The relationship of each biomarker's concentration with longissimus dorsi thickness (LDT) and the changes in LDT (ΔLDT) was assessed with pairwise correlations. Separate general linear models were used to assess the association of each biomarker with colostrum Brix values and milk production traits. Finally, the associated hazard for 1st artificial insemination (AI) and for pregnancy by 150 DIM (PREG_150DIM) was assessed with Cox proportional hazard models, while odds for pregnancy to the 1st AI (PREG_1stAI) were assessed with binary logistic models. 3-methylhistidine was affected mainly by herd, time points and their interaction. Higher 3-MH was associated with increased odds for metritis and CD_1–28, increased hazard for PREG_150 DIM and with increased milk production. 1-methylhistidine was affected mainly by herd, scKET and occurrence of displaced abomasum. Higher 1-MH was associated with better colostrum quality, increased odds for scKET, increased hazard for 1st AI by 150 DIM and with decreased milk production. Both 3-MH and 1-MH were weakly to moderately negatively correlated with LDT and moderately to strongly negatively correlated to ΔLDT at the corresponding time-periods. Additionally, higher TP was associated with increased odds for metritis and CD_1–28 and increased milk production, while higher ALB was associated with increased odds for scKET and increased milk production. Moreover, higher BUN was associated with decreased odds for scKET, increased odds for PREG_1stAI and increased milk production. Higher SCR was associated with decreased odds for retained fetal membranes, metritis, and CD_1–28. Peri-parturient protein metabolism is significantly associated with postpartum health, colostrum quality, reproduction, and milk production; mechanisms involved require further investigation.

Abstract Initially, the nutritional value of the three main by-products of Cannabis sativa (hempseed cake, second-rate quality hemp seed and hemp hay), cultivated under Greek conditions and collected from four plantations in the Macedonian region was estimated. A second part of the study was the investigation of the effects of diet inclusion with hempseed cake (HSC) on the performance of Holstein dairy cows. The HSC used for this experiment was the one analyzed in the first part of the study. A total number of 20 lactating cows were allocated into two equal groups in a randomized block design. Cows of both groups were offered a total mixed ration (TMR) on the same feed allowance. The diet of the experimental group was formulated with 3.5 % hemp cake, at a quantity of 1kg of hemp cake per cow per day. Milk yield was recorded individually, and feed refusals were recorded on a pen basis daily, during the first 40 days of lactation. Individual milk samples were analyzed for their chemical composition, lipid oxidative stability and fatty acid composition and tetrahydrocannabinol (THC) and cannabidiol (CBD) content, as well as feed samples of each group. Individual blood samples were received for biochemical indices assessment. All data were subjected ANOVA statistical analysis. The results of hemp by-products chemical profile showed similar nutritional values among the different cultivation regions. The experimental results indicated that the inclusion of HSC did not affect milk production and composition (P > 0.05). However, diet inclusion with HSC favorably influenced milk fatty acid profile. Finally, serum NEFA concentration was lower for the HSC group while serum urea levels were higher (P < 0.05).

The objective was to estimate the genetic parameters of serum total protein concentration in newborn calves (calfSTP) and post parturient dairy cows (cowSTP). The study included 1013 calves and 989 cows from 10 dairy farms. Calf blood samples were collected 24–48 h after parturition while cow blood and colostrum samples were collected in the first 24 h after calving. Blood serum total protein and colostrum total solids content were determined using a Brix refractometer. Chemical analysis of colostrum was performed with Milkoscan. Univariate mixed linear models were used to estimate the heritability of calfSTP and cowSTP and their genetic and phenotypic correlations with colostrum traits. The heritability estimates of calfSTP and cowSTP were 0.21 and 0.20 (p < 0.05), respectively. Strong genetic correlations (r > 0.90) were detected between calfSTP and colostrum total solids and protein content (p < 0.05). Corresponding phenotypic correlations were 0.31–0.33 (p < 0.05). No genetic or phenotypic correlations were detected with colostrum fat content while the respective correlations with lactose were negative (−0.82 and −0.19, p < 0.05). No genetic correlations were detected between cowSTP and colostrum traits and only a low negative phenotypic one with lactose was detected. The results confirm that genetic selection aiming to improve the passive transfer of immunity in newborn calves and general fresh cow health would be feasible.

A retrospective study was conducted to evaluate temporal patterns of environmental heat stress during the in -uterus period of development (IUP) and the 3-month post-natal (PN) period of dairy heifers, and to estimate their association with the age at first calving (AFC). Data from 30 dairy herds in Northern Greece including 9098 heifers were extracted from National Cattle Database. Data (2005-2019) regarding 230,100 farm-specific ambient daily temperature and relative humidity records, were obtained from ERA5-Land. Average monthly Temperature-Humidity-Index values (THI; low <= 68, and high>68) were calculated and matched for each heifer to their IUP and PN. Subsequently, Cluster Analysis was used with monthly THIs as predictors to allocate heifers to THI clusters. The association of clusters with AFC was assessed with Generalized Linear Mixed Model analysis, an extended form of multiple linear regression. Finally, 8 Heat Stress Clusters (HSC; namely HSC-1 to HSC-8) were identified. Compared to HSC-8 (8th-9th IUP months and 1st PN month) heifers of HSC-5 (4th-7th IUP months) and HSC-6 (6th-8th IUP months) calved 13.8 and 17.8 days later, respectively (P < 0.01-0.001). Moreover, when AFC was treated as a binary variable, heifers of HSC-5 and HSC-6 had 1.15 and 1.34 (P < 0.01-0.001) higher risk of calving for the first time later than 787 days compared to HSC-8, respectively.

Non-esterified fatty acids (NEFA) and β-hydroxybutyric acid (BHBA) concentrations in blood serum are the most used indicators of energy status in dairy sheep. Ultrasound measurement of backfat thickness (BFT) and longissimus dorsi muscle thickness (LDT) is a non-invasive and on-field applicable technique, with no established critical thresholds for assessing energy balance in dairy sheep. The objective of the present study was to evaluate the use of ultrasound indices of BFT and LDT as image biomarkers of negative energy balance in pre-partum dairy ewes. The study was conducted in four commercial dairy sheep flocks in Central Macedonia Region of Greece, that each one reared a specific breed of purebred sheep. The final number of ewes with full records used in statistical analysis was 177 (flock A-Assaf.E, = 49, flock B-Chios = 46, flock C- Lacaune = 42 and flock D-Frizarta = 40). All animal measurements were performed one month (−30 ± 4d) and two weeks (−15 ± 4d) prior to estimated lambing date. Body condition score was assessed by palpation at the lumbar region. BFT and LDT were determined with ultrasonography after body condition scoring, to avoid bias on BCS estimation. The sum of BFT and LDT (TotalT), the LDT: BFT ratio (RatioT) and the difference in BFT (Δ_BFT) and LDT (Δ_LDT) between the two measurements were calculated. Blood sampling of ewes was performed on − 15d for serum BHBA and NEFA measurements. Negative energy balance status was defined as serum BHBA > 0.8 mmol/L or NEFA > 0.3 mmol/L. The receiver operating characteristic (ROC) analysis was used to define thresholds for fat and muscle reserves and mobilization parameters to predict elevated BHBA or NEFA status. All variables with a significant area under the ROC curve were transformed into binary variables and used in 2 multifactorial binary logistic regression models to assess the association of fat and muscle reserves and mobilization parameters with BHBA and NEFA status. Ewes with Δ_BFT > 0.65 mm had 3.2 times (P = 0.002) increased probability to have serum NEFA > 0.3 mmol/L. Moreover, ewes with BFT(−30d) > 6.86 mm, had 6.7 times (P < 0.001) increased probability to have serum NEFA > 0.3 mmol/L. Ewes with a BFT loss had 6.7 times (P < 0.001) increased probability to have serum BHBA > 0.8 mmol/L. Moreover, ewes with TOTAL_T(−15d) ≤ 25.6 mm, had 5.3 times (P < 0.001) increased probability to have serum BHBA > 0.8 mmol/L. The results showed that ultrasound measurements of BFT and LDT the last month of gestation can be used as a reliable alternative to BCS or metabolic profiling for the assessment of energy status in dairy sheep. Measuring BFT one month prior to lambing or TotalT two weeks prior to lambing can both provide reliable estimations.

Ruminal pH in dairy cows follows a diurnal fluctuation; low values are indicative of subacute ruminal acidosis and are associated with alterations of rumen fatty acids concentrations. The objective of the present study was to prospectively study the associations between ruminal pH and the rumen fluid concentrations of short, medium, and long chain fatty acids, under field conditions during the first half of lactation in 53 Holstein cows of a dairy farm. Ruminal fluid was obtained by rumenocentesis, which was performed at 30, 90, and 150 days in milk (DIM). Ruminal pH was measured immediately after collection with a portable pH meter, whereas gas chromatography was used for the determination of ruminal fatty acid concentrations. Mixed linear regression models were used for data analysis. The prevalence of cows with low ruminal pH (≤5.5) was 45.3%, 54.7%, and 66.0% at 30, 90, and 150 DIM, respectively. The concentrations of acetic, propionic, butyric, valeric, isovaleric, caproic and linoleic acids were negatively associated with ruminal pH values, whereas the acetic to propionic ratio was positively associated with rumen pH. Under field conditions and naturally occurring low ruminal pH cases, ruminal concentrations of most fatty acids are negatively related with ruminal pH values

The objective of this study was to evaluate the effects of subclinical hypocalcemia (SCHCa) patterns on reproductive performance in dairy cows. In a prospective observational study 916 cows from 9 herds were blood sampled on DIMs 1, 2, 4 and 8; Ca concentration was measured with atomic absorption and SCHCa was defined as Ca <= 2.09 mmol/L. Cluster analysis revealed 2 normocalcemic (NORM and HIGH) and five hypocalcemic (SCH-1 to 5) clusters. Cows in cluster NORM (n = 151) had mean day-to-day serum Ca (DIMs 1-8) between 2.24 and 2.41 mmol/L, and cows in HIGH (n = 167) between 2.42 and 2.53 mmol/L. Cows in SCH-1 (n = 130) and SCH-2 (n = 102) had transient and mostly mild SCHCa on day 1 and day 2, respectively. Cows in SCH-3 (n = 123) had mostly severe SCHCa on days 1 and 2, extending to day 4. Cows in SCH-4 (n = 120) and SCH-5 (n = 145) had SCHCa which culminated on days 4 and 8, respectively. Information on reproductive outcomes including pregnancy status by 120 and 200 DIM and days open were retrieved from farm records. Median (+/- SE) days to 1st artificial insemination (AI) until 120 DIM estimated with Kaplan-Meier analysis for cows in SCH-3, SCH-4 and SCH-5 were 100.0 +/- 7.2, 109.0 +/- 6.6 and 120.0 +/- 3.2, respectively, and were statistically significantly higher from those in NORM and HIGH (91.0 +/- 3.4 and 87 +/- 3.7, respectively). Mean days (+/- SE) to detected pregnancy until 200 DIM estimated with Kaplan-Meier analysis for cows in SCH-3 were 161.2 +/- 4.8 and were statistically significantly higher from those in clusters NORM and HIGH (155.5 +/- 4.2 and 151.6 +/- 4.3, respectively). The association of Ca clusters with the odds of detected pregnancy for the 1st insemination until 120 and 200 DIM was evaluated with Linear Mixed Models. Odds for pregnancy by 120 DIM did not differ among clusters, however, cows in clusters SCH-3 and SCH-5 had lower odds for pregnancy by 200 DIM compared to HIGH (OR = 0.55, P = 0.02, and OR = 0.49, P = 0.004, respectively). Covariate adjusted survival curves generated by multivariable Cox proportional hazards model revealed that: a) clusters SCH-3 and SCH-5 had the highest (36% and 38%, respectively), while NORM and HIGH the lowest (16% and 17%, respectively) proportion of cows not inseminated for the 1st time by 120 DIM, b) compared to HIGH, cows in SCH-5 had a lower hazard of pregnancy by 120 DIM (HR = 0.42, P = 0.005), c) the proportion of open cows by 200 DIM for NORM and HIGH were 57% and 47%, respectively, while for SCH-3 and SCH-5 66% and 68%, respectively, and d) compared to HIGH, SCH-3 (HR = 0.54, P = 0.008) and SCH-5 (HR = 0.50, P = 0.001) presented the lowest hazard for pregnancy by 200 DIM. In conclusion, cows that during the entire first week after calving were continuously normocalcemic had the best reproductive performance, while those of SCH-3 and SCH-5 the worst. (C) 2022 Elsevier Inc. All rights reserved.

Dairy cows face precipitous metabolic adaptations during the first postpartum week. Increasing knowledge of their hematologic profiles during this period could benefit both veterinary clinical pathologists and bovine practitioners. The objectives of this study were: (a) to establish period-specific RIs for Holstein dairy cows and (b) to assess the potential simultaneous effect of several factors on hematology parameters. Blood samples from clinically healthy cows of nine herds were used to establish hematology RIs for these periods. There were 68 cows in the prepartum period (PP), 247 and 218 cows at 2 and 8 days after calving (2 and 8 days in milk [DIM 2 and DIM 8], respectively), and 87 cows in peak lactation (PL). A complete blood count evaluation was performed using the ADVIA 120 analyzer. Linear models estimated the analytes associated with parity. RIs were calculated with Reference Value Advisor. Parity had a significant effect on analytes at all stages. Marked differences were evident between DIM 2 and 8 regarding red blood cell (RBC) counts, hematocrits, hemoglobin concentrations, and white blood cell (WBC), monocyte, and eosinophil counts. Reference intervals of RBC counts, hematocrits, and hemoglobin concentrations at DIM 2 were higher than those at PP and PL. This study provides evidence that period-specific RIs should be used for Holstein cows when making clinical decisions, especially during the critical first week postpartum.

The objective was to assess the effect of housing conditions during the summer months on the success rates of cervical artificial insemination (AI) with cooled semen, in intensively reared dairy ewes in Greece. The study involved 2083 Lacaune ewes from 23 flocks that were serviced during May to September. An estrous synchronization protocol with the insertion of progestogen sponges for 14 days and eCG administration at sponge removal, was used. All ewes were inseminated 54–57 h after sponge removal with cooled semen (15 °C) from 10 Lacaune rams. Pregnancy diagnosis was performed via trans-dermal ultrasonography at 35–40 days after AI. Data recording started the day after sponge placement (15 days prior to AI), and lasted up to 14 days after AI. Daily records included temperature, relative humidity, and Temperature-Humidity Index (THI) inside the shed. Available space and volume per animal, frequency of bedding renewal, access to a yard, and indoor light were also recorded in each farm. Binary logistic regression of data records showed that temperature and THI increases at days −15 to +4 around AI (day 0) had a negative effect on pregnancy rates (reducing the likelihood of pregnancy by 3–6% and 7%, respectively). The latter also decreased significantly (p < 0.05) in farms with high stocking density, non-frequent bedding renewal, and outdoor access by ewes (by 30%, 34%, and 44%, respectively). Overall, the results indicate that appropriate housing conditions are warranted to increase the success of AI in dairy ewes during the summer months.

Nutrient deficit during the periparturient period leads to mobilisation of body energy and protein reserves. Research regarding fat reserves and mobilisation is extensive, while, on the contrary, investigation of muscle mobilisation during the periparturient period is limited. The aim of this cohort study was to simultaneously investigate the biological variation of skeletal muscle and subcutaneous fat reserves together with their mobilisation in transition Holstein cows of different herds, using ultrasonography, and to assess potential affecting factors. For this purpose, ultrasound measurements of longissimus dorsi muscle thickness (LDT) and backfat thickness (BFT) from 238 multiparous cows of six dairy farms were obtained at six time points across the transition period (from 21 days pre- to 28 days postpartum). Concentrations of serum creatinine and non-esterified fatty acids were determined in order to confirm the loss of muscle mass and adipose tissue, respectively. Cases of clinical postparturient diseases and subclinical ketosis (scKET) during the first 28 days postcalving were recorded. Cows mobilised on average 32.8% and 37.3% of LDT and BFT reserves, respectively. Large between-cow variation was observed for both the onset and the degree of mobilisation. Time point, initial body condition score and parity were the most important predictors of LDT variation. Cows diagnosed with metritis (MET) had lower LDT postpartum and mobilised more muscle depth compared to cows not diagnosed with MET. Initial BCS, time point, initial BW (estimated by heart girth measurement) and parity were the most important predictors of BFT variation. Cows diagnosed with MET mobilised more backfat between -7d and 7d compared to cows not diagnosed with MET. Cows with scKET mobilised more backfat between 7- and 21 days postpartum compared to healthy ones. Variation of subcutaneous fat and skeletal muscle reserves during the transition period was large and affected by herd and several cow-level factors.

Two hundred and forty-three clinically healthy Holstein calves from eight commercial dairy farms were used to: (a) describe the evolutionary course of ruminal VFA concentration and pH during the peri-weaning period and (b) assess management factors affecting their phenotypical variation of these parameters. Management practices were recorded individually for each calf as these were not fixed within farms. Samples of ruminal fluid were collected at −7 d, 0 d, and 7 d relative to weaning. Gas chromatography was used to measure ruminal VFAs, and pH was measured on site. Linear mixed models for repeated measurements were used to assess the effects of management factors and their interactions. A large among-calves phenotypical variability was observed. Estimated marginal means showed that concentrations of acetate, butyrate, and total VFAs (but not of propionate) significantly decreased, while acetate propionate increased, from −7 d to 7 d. Age at weaning and body weight at −7 d were positively associated with total and several individual VFA concentrations. Group housing and late forage feeding pre-weaning were associated with higher VFA concentrations; the same factors, as well as step-weaning, were associated with pH values around 6. Feeding 7–8 L of milk replacer daily did not preclude a smooth transition, irrespective of weaning method.

The aim of this study was, for the first time, to simultaneously assess the association of skeletal muscle and subcutaneous fat reserves and their mobilisation, measured by ultrasonography, with the incidence of specific postparturient health, reproduction, and milk production traits. For this purpose, ultrasound measurements of longissimus dorsi thickness (LDT) and backfat thickness (BFT) from 238 multiparous cows from 6 dairy farms were obtained at 6 time points during the transition period (from 21 days pre-to 28 days postpartum). In each case, LDT and BFT measurements at each time point and LDT and BFT mobilisation variables at each study period were assessed simultaneously. Cases of specific clinical postparturient diseases and subclinical ketosis were recorded. An additional disease trait was used, defined as the presence or absence of at least one clinical condition after calving (CD_1-28). The associ-ated disease odds with LDT/BFT variables were assessed with binary logistic regression models. The asso-ciated hazard for 1st artificial insemination (AI) and for pregnancy by 150 days-in-milk (PREG_150DIM) was assessed with Cox proportional hazard models. Moreover, binary logistic models were used to assess the associated odds for pregnancy to 1stAI (PREG_1stAI). Finally, association with 30d, 100d and 305d milk yield was assessed with linear regression models. Increased muscle depth during transition was negatively associated with odds for metritis and CD_1-28, while associations with odds for subclinical ketosis were inconclusive. Moreover, increased LDT reserves were associated with greater hazard for 1st AI by 150 days-in-milk, but results were inconclusive regarding odds for PREG_1stAI. Increased LDT mobilisation was associated with increased odds for metritis. Increased BFT reserves were positively associated with odds for metritis, CD_1-28 and subclinical ketosis and with decreased hazard for PREG_150DIM. Increased BFT mobilisation was associated with increased odds for subclinical ketosis and with decreased odds for PREG_1stAI and decreased hazard for PREG_150DIM. Cows with moderate BFT reserves performed better. Finally, increased BFT mobilisation during-21d to-7d from parturition was associated with less milk by 30d and 100d. On the contrary, increased BFT mobilisation during-7d to 7d was associated with more milk by 305d. Metabolism of muscle and fat tissue during transition per-iod was differently associated with different postparturient health, reproduction and milk production traits. In general, greater muscle mass and moderate fat reserves with limited muscle and fat mobilisation were associated with better performance.(c) 2022 The Authors. Published by Elsevier B.V. on behalf of The Animal Consortium. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Biochemical profiles help vet practitioners identify problems in the weaning process when major metabolical changes occur. Reference intervals (RI) are useful in this respect but have not been established for this period. The objective of this study was twofold a) to identify the effect of time relative to weaning, adjusted for age at weaning, on the biochemical profile and b) to establish relevant RIs and assess the necessity of using time-specific RIs for the pre- and post-weaning periods instead of a single RI for this time frame. Two-hundred and forty-one clinically healthy Holstein calves from 9 commercial dairy farms were blood-sampled, at -7d, 0d and +7d relative to the day of weaning (0d). Samples were analyzed to determine the concentration of serum total protein (TP), albumin (ALB), globulin (GLOB), blood urea nitrogen (BUN), cholesterol (CHOL), triglyceride (TRIG), total bilirubin (tBIL), aspartate aminotransferase (AST), gamma-glutamyl transferase (gamma-GT), ll-hydroxybutyrate (BHB) and non-esterified fatty acids (NEFA). The effect of time relative to weaning (TIME-W), adjusted for age at weaning and accounting for herd- and calf-level random variation, was assessed using linear mixed models. Reference intervals for total peri-weaning (PeriRI), pre-weaning (PreRI) and post-weaning (PostRI) periods were generated with the freeware Reference Value Advisor. Established RIs were visually compared with Adult cow RIs (AC). In order to test the agreement between PeriRI and PreRI/PostRI, the Cohen's kappa coefficient (lc) was used. The effect of TIME-W was significant for all parameters, except CHOL. Estimated marginal means for TP, ALB, GLOB, BUN, AST and BHB increased across TIME-W, while those of tBIL and NEFA decreased from 0d to +7d and of TRIG decreased from -7d to 0d. Total peri-weaning period RIs differ from AC for all parameters except gamma-GT; PeriRI should be used for all biochemical parameters except for BUN, AST and BHB for which, PreRI and PostRI are preferable. The latter three parameters are potential candidates for assessing weaning management.