Association between early postpartum rumination time and peak milk yield in dairy cows

Limited information is available on the relationship between rumination time (RT) in the early postpartum period and milk production later in lactation. Therefore, the objectives of this study were to (1) investigate the association of change in RT and average RT during the immediate postpartum period with peak milk yield (PMY) in dairy cows, and (2) determine the best model based on days in milk (DIM) to evaluate this association. Cows from 33 free-flow automatic milking system farms were included in this study, where retrospective milk production and RT data were collected for 12 mo. Cows were categorized by parity number into parity 1 (P1, n = 1,538), parity 2 (P2, n = 1,354), or parity ≥3 (P3+, n = 1,770). For each cow, PMY was identified as the highest daily milk yield up to 180 DIM for P1 and 120 DIM for P2 and P3+ cows. Five change in RT variables and 5 average RT variables were created corresponding to the first 2 to 6 DIM. Change in RT variables were the slope coefficients for change in RT/d related to DIM = 1 extracted from simple linear regressions, and average RT variables were the arithmetic mean RT. Five models analyzing PMY and corresponding variables calculated over the first 2 to 6 DIM had fixed effects of average RT, change in RT, parity, average RT × parity interaction, change in RT × parity interaction, and a random intercept for farm. Peak milk yield occurred at (median) 75, 44, and 46 DIM for P1, P2, and P3+, respectively. Overall PMY was (mean ± standard deviation) 54 ± 11 kg and it increased as parity increased. A positive association was found between change in RT and PMY, and average RT and PMY for P2 and P3+ cows in all 5 models corresponding to the first 2 to 6 DIM, indicating that greater average RT and quicker increase in RT after calving are associated with greater PMY for multiparous cows. Although the model including all 6 DIM had the greatest accuracy, results indicated that rumination data collected over the first 2 DIM may also provide adequate information for the association of average RT and change in RT with PMY in P2 and P3+ cows. For each 100 min/d increase in change in RT over the first 6 DIM, PMY increased by 4.3 (95% confidence interval: 2.2–6.3) and 4.8 (95% confidence interval: 3.2–6.5) kg for P2 and P3+ cows, respectively. Peak milk yield increased by 2.3 (95% CI: 1.7–2.8) and 2.2 (95% confidence interval: 1.7–2.6) kg for each 100 min increase in average RT over the first 6 DIM for P2 and P3+ cows, respectively. No association was observed between rumination behaviors and PMY for P1 cows. Results from this study indicate that the length of time for multiparous cows to achieve a stable RT in the early postpartum period combined with average RT during the same period may be useful in predicting their overall lactation milk production.     

Metabolic profiling of early-lactation dairy cows using milk mid-infrared spectra

Metabolic disorders in early lactation have negative effects on dairy cow health and farm profitability. One method for monitoring the metabolic status of cows is metabolic profiling, which uses associations between the concentrations of several metabolites in serum and the presence of metabolic disorders. In this cross-sectional study, we investigated the use of mid-infrared (MIR) spectroscopy of milk for predicting the concentrations of these metabolites in serum. Between July and October 2017, serum samples were taken from 773 early-lactation Holstein Friesian cows located on 4 farms in the Gippsland region of southeastern Victoria, Australia, on the same day as milk recording. The concentrations in sera of β-hydroxybutyrate (BHB), fatty acids, urea, Ca, Mg, albumin, and globulins were measured by a commercial diagnostic laboratory. Optimal concentration ranges for each of the 7 metabolites were obtained from the literature. Animals were classified as being either affected or unaffected with metabolic disturbances based on these ranges. Milk samples were analyzed by MIR spectroscopy. The relationships between serum metabolite concentrations and MIR spectra were investigated using partial least squares regression. Partial least squares discriminant analyses (PLS-DA) were used to classify animals as being affected or not affected with metabolic disorders. Calibration equations were constructed using data from a randomly selected subset of cows (n = 579). Data from the remaining cows (n = 194) were used for validation. The coefficient of determination (R²) of serum BHB, fatty acids, and urea predictions were 0.48, 0.61, and 0.90, respectively. Predictions of Ca, Mg, albumin, and globulin concentrations were poor (0.06 ≤ R² ≤ 0.17). The PLS-DA models could predict elevated fatty acid and urea concentrations with an accuracy of approximately 77 and 94%, respectively. A second independent validation data set was assembled in March 2018, comprising blood and milk samples taken from 105 autumn-calving cows of various breeds. The accuracies of BHB and fatty acid predictions were similar to those obtained using the first validation data set. The PLS-DA results were difficult to interpret due to the low prevalence of metabolic disorders in the data set. Our results demonstrate that MIR spectroscopy of milk shows promise for predicting the concentration of BHB, fatty acids, and urea in serum; however, more data are needed to improve prediction accuracies.     

Milk yield relative to supplement intake and rumination time differs by health status for fresh cows milked with automated systems

Automated milking systems (AMS) provide the capability of adjusting the amount of supplemental concentrate offered to cows based on parity, days in milk, and milk yield; in many situations, more supplement is provided to those cows with higher production demands. To determine associations of subclinical ketosis (SCK) and blood β-hydroxybutyrate (BHB) with milk yield, supplement consumed in the AMS, rumination time, and the ratios of milk yield to supplement intake and milk yield to rumination time, we monitored 605 cows from 9 AMS herds, testing blood BHB concentrations 1×/wk for the first 3 wk of lactation. Milk yield, supplement intake, and rumination data were collected from the AMS computer on each farm. For analyses, only multiparous cows from 8 herds were included (n = 172 total) and were matched, within farm, to include an equal number of cows in each of 4 health status groups (n = 43 per group): SCK (BHB ≥1.2 mmol/L at ≥1 of 3 tests, with no other disorder in the first 30 d in milk), SCK+ (BHB ≥1.2 mmol/L at ≥1 of 3 tests, with another health disorder), HLT (BHB always <1.2 mmol/L, with no other disorder), or OTH (BHB always <1.2 mmol/L, with a health disorder). Milk yield and rumination time varied by health status, but we found no difference in supplement intake by health status group. As a result, milk yield relative to supplement intake and milk yield relative to rumination time differed by health status and were both positively associated with BHB. Cows in SCK had the highest milk yield and ratio of milk yield to supplement intake, but SCK+ cows had the lowest rumination time and the highest milk yield to rumination ratio. These results highlight the differences in milk production (per day and relative to supplement consumption or rumination time) associated with blood BHB and health status. Therefore, potential exists to modify supplementation in AMS to reduce negative energy balance by accounting for milk production of fresh cows.     

Effects of spray-dried plasma protein product on early-lactation dairy cows

Spray-dried plasma protein (SDP) compared with blood meal (BM) may contain various functional and active components that may benefit animal health. The objective of this experiment was to investigate the effects of feeding SDP or BM on production and blood profile in dairy cows during the transition and early-lactation periods. Seventy-two Holstein cows at 14 d before calving were used in a randomized block design. During the prepartum period, cows were fed a typical late-gestation diet containing BM (100 g/cow per day; 100BM, n = 24) or SDP (100 g/cow per day; 100SDP; n = 48). After calving, cows that were fed BM prepartum were fed a typical lactation diet formulated to provide 100 g/d of BM (100BM). Half the cows that were fed 100SDP prepartum were fed a lactation diet formulated to provide 100 g/d of SDP (100SDP; n = 24), and half were fed a diet formulated to provide 400 g/d of SDP (400SDP; n = 24) on a dry matter basis where SDP replaced BM (100SDP) or BM and soybean products (400SDP). All diets were balanced for crude protein concentration and metabolizable protein supply assuming BM and SDP were equal in rumen-degradable protein and rumen-undegradable protein. All data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) as a randomized block design where contrasts were made for 100BM versus 100SDP for prepartum variables and 100BM versus 100SDP and 100SDP versus 400SDP for postpartum variables. Prepartum supplementation of SDP had no effect on plasma fatty acids and β-hydroxybutyrate (2 d before calving). Plasma fatty acids (255 ± 29 µEq/mL) and β-hydroxybutyrate (675 ± 70 µmol/L) at 8 and 14 d of lactation were not affected by SDP in the diet. Feeding SDP at 100 g/d compared with 100BM increased or tended to increase milk fat, protein, and lactose contents for 16 wk after parturition. Providing SDP at 400 g/d in the diet increased milk yield (42 vs. 39 kg/d), energy-corrected milk (44 vs. 41 kg/d), energy-corrected milk per kilogram of dry matter intake, and yields of milk fat (1.60 vs. 1.48 kg/d), protein (1.21 vs. 1.16 kg/d), and lactose compared with 100SDP. Body weight losses tended to be lower for 100SDP compared with 100BM without a difference between 100SDP and 400SDP. Plasma histidine concentration (d 14 of lactation) was lower for SDP compared with 100BM. In addition, plasma 1-methyl-l-histidine tended to be lower as inclusion rate of SDP increased. In conclusion, SDP at 400 g/d increased milk and milk component yields without an increase in feed intake. Studies evaluating effects of functional and active compounds in SDP on gut microbiome, gut health, and immune functions may be needed to determine mode of action.     

Calving difficulty influences rumination time and inflammatory profile in Holstein dairy cows

Difficult calving may adversely affect dairy cow health and performance. Maternal:fetal disproportion is a major cause of dystocia. Therefore, the main objective of this study was to assess the effects of dam:calf body weight ratio (D:C) on calving difficulty, rumination time, lying time, and inflammatory profile in 25 Holstein dairy cows. Using automatic monitoring systems, we monitored behavior and production in 9 primiparous and 16 pluriparous cows between dry-off and 30 d in milk. During the same period, we collected blood samples to monitor metabolism and inflammatory profile of these cows. Calvings were video recorded to assess calving difficulty and observe the duration of the expulsive stage. After parturition, the cows were separated into 3 classes according to their D:C: easy (E; D:C >17), medium (M; 14 < D:C <17), and difficult (D; D:C <14). The cows in class D showed relatively longer labor durations (108 min vs. 54 and 51 min for classes D, M, and E, respectively) and higher calving assistance rates (50% vs. 0 and 11% of calvings for classes D, M, and E, respectively) than those in the other 2 classes. Compared with the cows in classes M and E, those in class D exhibited shorter rumination times on the day of calving (176 min/d vs. 288 and 354 min/d for classes D, M, and E, respectively) and during the first week of lactation (312 min/d vs. 339 and 434 min/d for classes D, M, and E, respectively) and maintained lower rumination values until 30 DIM (399 min/d vs. 451 and 499 min/d for classes D, M, and E, respectively). Primiparous class D cows had shorter resting times during the first week after calving compared with those in class M (8 vs. 11 h/d for classes D and M, respectively). Interclass differences were found in terms of the levels of inflammation markers such as acute-phase proteins (ceruloplasmin, albumin, retinol, and paraoxonase). Moreover, cows in class D had lower plasma levels of fructosamine and creatinine after calving. Low D:C reduced postcalving rumination time and increased inflammation grade, suggesting a lower welfare of these animals at the onset of lactation. The D:C might serve as a useful index for the identification of cows at relatively higher risk of metabolic and inflammatory disease, thus helping farmers and veterinarians improve the welfare and health of these cows.     

Association of postpartum hypocalcemia with early-lactation milk yield,reproductive performance,and culling in dairy cows

Periparturient hypocalcemia is frequently observed and considered as a gateway disease that is associated with various health issues. The objective of this study was to evaluate the association of hypocalcemia with early-lactation milk yield, reproductive performance, and culling across a large number of different managerial systems. A prospective cohort study was conducted based on a convenience sample of 125 dairy herds from 8 federal states of Germany between February 2015 and August 2016. A blood sample was drawn from 1,709 animals within 48 h after parturition and analyzed for serum calcium concentration. After discarding cows (n = 283) with missing data, a total of 1,426 cows were considered for final analyses. The median time from calving to sampling was 14.0 h (interquartile range = 5.0–24.9 h). For each herd, a record of the herd management software was requested 150 d after the last cow was sampled. Serum calcium concentration of each cow was associated with early-lactation milk yield (Dairy Herd Improvement Association equivalent test 1 to 3), reproductive performance [days in milk (DIM) at first artificial insemination (AI), pregnancy at first AI, time to pregnancy within 150 DIM], and culling (until 60 DIM) data. Generalized linear mixed models were used to analyze continuous or categorical data. Shared frailty models were used for time to event data. Five different thresholds were used to define hypocalcemia. Thresholds ranged from 1.8 to 2.2 mmol/L using 0.1-mmol/L increments. Clinical hypocalcemia was defined as serum calcium concentration <2.0 mmol/L in combination with clinical signs (e.g., recumbency). The effect of hypocalcemia on milk yield was conditional on parity. In primiparous cows a serum calcium concentration <2.0 mmol/L (6.4% of cows were below this threshold) had no effect on milk production, whereas there was a tendency for multiparous cows with a serum calcium concentration <2.1 mmol/L (63.2% of cows were below this threshold) to produce 0.80 kg/d more milk compared with multiparous cows at or above the threshold. Multiparous cows suffering from clinical hypocalcemia produced 2.19 kg/d less milk compared with normocalcemic cows in early lactation. Calcium status was not associated with days to first insemination. Cows with a serum calcium concentration <1.9 mmol/L (34.6% of cows below this threshold) had decreased odds (odds ratio = 0.56) of pregnancy at first AI. A serum calcium concentration <1.8 mmol/L (24.1% of cows below this threshold) had a significant effect on time to pregnancy. Compared with animals with a serum calcium concentration ≥1.8 mmol/L, the hazard of becoming pregnant within 150 DIM was reduced when cows had a serum calcium concentration <1.8 mmol/L (hazard ratio = 0.68). Cows with a serum calcium concentration <2.0 mmol/L (44.3% of cows were below this threshold) had a 1.69 times greater hazard of being culled within the first 60 DIM compared with normocalcemic animals. The present study shows that the association of hypocalcemia with milk yield was conditional on parity and serum calcium concentration measured once within 48 h after calving. Considering reproductive performance and culling in early lactation, a negative effect of postpartum hypocalcemia was demonstrated.     

Effects of different transition diets on dry matter intake,milk production,and milk composition in dairy cows

The primary objective of this study was to evaluate the effect on dry matter intake (DMI), milk yield, milk composition, body weight (BW), and body condition score (BCS) change of cows offered diets differing in energy density in the last 4 wk of gestation and in the first 8 wk of lactation. Three diets (grass silage:straw, 75:25 on a dry matter basis (SS), grass silage (S), and grass silage + 3 kg concentrate daily (C)) precalving, and two diets (4 kg [LC] or 8 kg [HC] concentrate daily + grass silage ad libitum) postcalving were combined in a 3 x 2 factorial design. Sixty Holstein-Friesian cows entering their second lactation were blocked according to expected calving date and BCS into groups of six and were then allocated at random to the treatments. Individual feeding started 4 wk prior to the expected calving date and measurements were made until the end of the 8th wk of lactation. Mean DMI differed between each of the precalving treatments (7.4, 8.1, and 9.9 kg/d for SS, S, and C, respectively) in the precalving period. The DMI also differed between SS and C for wk 1 to 8 (13.5 and 14.2 kg/d) postcalving. Postcalving, milk (24.2, 26.2, and 28.2 kg/d), fat (933, 1063, and 1171 g/d), and protein (736, 797, and 874 g/d) yields differed between SS, S, and C, respectively. The BCS changes differed between SS and C (-0.09 and 0.12 of a BCS) in the precalving period and between SS and S compared with C (0.02, 0.06, and -0.26 of a BCS) for wk 1 to 8 postcalving. The BW change differed between SS and S compared with C in both wk 1 to 4 (-0.23, -0.37, and -1.25 kg/d) and wk 1 to 8 (0.18, 0.10, and -0.58 kg/ d) postcalving. The BW and BCS were lower at calving for cows on SS compared with C. The greater amount of concentrate supplement postcalving increased DMI, yields of milk, fat, and protein and decreased BW loss in the first 8 wk of lactation. In conclusion, these results indicate that a greater energy density diet in the final 4 wk of the dry period improves cow production in early lactation.     

Production effects of feeding extruded soybean meal to early-lactation dairy cows

The objective of this experiment was to evaluate productive and reproductive effects of replacing solvent-extracted soybean meal (SSBM) with extruded soybean meal (ESBM) in a total mixed ration for early-lactation dairy cows. Thirty-four Holstein cows (12 primiparous and 22 multiparous) were used in a randomized complete block design experiment with 17 cows per treatment. Feeding was ad libitum for 5 to 10% refusals. A fresh-cow diet was fed the first 21 d in milk followed by a lactation diet from 22 to 60 d in milk. Milk and dry matter intake data were collected throughout the experiment, and samples were collected for blood chemistry and amino acid profile, nutrient digestibility, nitrogen utilization, and enteric methane emission using the GreenFeed system (C-Lock Inc., Rapid City, SD). Dry matter intake, milk yield, and feed efficiency were not different between SSBM and ESBM. Energy-corrected milk yield and efficiency were also not different between diets. Diet had no effect on milk composition, except that milk true protein yield was decreased by ESBM. Enteric methane emission, yield, and intensity were not different between SSBM and ESBM. Because of its greater fat content, ESBM triggered expected changes in milk fatty acid (FA) profile: decreased sum of C16, saturated, and odd- and branched-chain FA and increased sum of preformed FA, polyunsaturated, and trans FA. The ESBM diet increased or tended to increase some essential amino acids in plasma. In this study, ESBM did not affect dry matter intake and did not improve lactational performance or onset of ovarian function in early-lactation dairy cows, and it decreased milk protein yield, possibly due to greater unsaturated FA intake compared with SSBM.     

Effects of timing of palmitic acid supplementation on production responses of early-lactation dairy cows

The objective of our study was to evaluate the effects of timing of palmitic acid (C16:0) supplementation on production responses of early-lactation dairy cows. Fifty-two multiparous cows were used in a randomized complete block design experiment. During the fresh period (FR; 1–24 d in milk) cows were assigned to either a control diet containing no supplemental fat (CON) or a diet supplemented with C16:0 (palmitic acid, PA; 1.5% of diet dry matter). During the peak (PK) period (25–67 d in milk) cows were assigned to either a CON diet or a PA (1.5% of diet dry matter) diet in a 2 × 2 factorial arrangement of treatments considering the diet that they received during the FR period. During the FR period, we did not observe treatment differences for dry matter intake or milk yield. Compared with CON, PA increased the yield of 3.5% fat-corrected milk by 5.30 kg/d, yield of energy-corrected milk (ECM) by 4.70 kg/d, milk fat content by 0.41% units, milk fat yield by 280 g/d, and protein yield by 100 g/d. The increase in milk fat associated with the PA treatment during the FR period occurred due to an increase in yield of 16-carbon milk fatty acids (FA) by 147 g/d (derived from both de novo synthesis and extraction from plasma) and preformed milk FA by 96 g/d. Compared with CON, PA decreased body weight (BW) by 21 kg and body condition score (BCS) by 0.09 units and tended to increase BW loss by 0.76 kg/d. Although PA consistently increased milk fat yield and ECM over time, a treatment × time interaction was observed for BW and BCS due to PA inducing a greater decrease in BW and BCS after the second week of treatments. Feeding PA during the PK period increased milk yield by 3.45 kg/d, yield of 3.5% fat-corrected milk by 4.50 kg/d, yield of ECM by 4.60 kg/d, milk fat content by 0.22% units, milk fat yield by 210 g/d, protein yield by 140 g/d, and lactose yield by 100 g/d but tended to reduce BW by 10 kg compared with CON. Also, during the PK period we observed an interaction between diet fed in the FR and PK periods for milk fat yield due to feeding PA during the PK period increasing milk fat yield to a greater extent in cows that received the CON diet (+240 g/d) rather than the PA diet (+180 g/d) during the FR period. This difference was associated with the yield of preformed FA because feeding PA during the PK period increased the yield of preformed milk FA only in cows that received the CON diet during the FR period. In conclusion, feeding a C16:0 supplement to early-lactation cows consistently increased the yield of ECM in both the FR and PK periods compared with a control diet. For some variables, the effect of feeding C16:0 was affected by timing of supplementation because milk yield increased only during the PK period and BW decreased to a greater extent in the FR period. Regardless of diet fed in the FR period, feeding a C16:0 supplement during the PK period increased yields of milk and milk components.     

Prediction of metabolic status of dairy cows in early lactation using milk fatty acids and test-day variables

Early lactation metabolic imbalance is an important physiological change affecting the health, production, and reproduction of dairy cows. The aims of this study were (1) to evaluate the potential of test-day (TD) variables with or without milk fatty acids (FA) content to classify metabolically imbalanced cows and (2) to evaluate the robustness of the metabolic classification with external data. A data set was compiled from 3 experiments containing plasma β-hydroxybutyrate, nonesterified FA, glucose, insulin-like growth factor-I, FA proportions in milk fat, and TD variables collected from 244 lactations in wk 2 after calving. Based on the plasma metabolites, 3 metabolic clusters were identified using fuzzy c-means clustering and the probabilistic membership value of each cow to the 3 clusters was determined. Comparing the mean concentration of the plasma metabolites, the clusters were differentiated into metabolically imbalanced, moderately impacted, and balanced. Following this, the 2 metabolic status groups identified were imbalanced cows (n = 42), which were separated from what we refer to as “others” (n = 202) based on the membership value of each cow for the imbalanced cluster using a threshold of 0.5. The following 2 FA data sets were composed: (1) FA (groups) having high prediction accuracy by Fourier-transform infrared spectroscopy and, thus, have practical significance, and (2) FA (groups) formerly identified as associated with metabolic changes in early lactation. Metabolic status prediction models were built using FA alone or combined with TD variables as predictors of metabolic groups. Comparison was made among models and external evaluations were performed using an independent data set of 115 lactations. The area under the receiver operating characteristics curve of the models was between 75 and 91%, indicating their moderate to high accuracy as a diagnostic test for metabolic imbalance. The addition of FA groups to the TD models enhanced the accuracy of the models. Models with FA and TD variables showed high sensitivities (80–88%). Specificities of these models (73–79%) were also moderate and acceptable. The accuracy of the FA models on the external data set was high (area under the receiver operating characteristics curve between 76 and 84). The persistently good performance of models with Fourier-transform infrared spectroscopy-quantifiable FA on the external data set showed their robustness and potential for routine screening of metabolically imbalanced cows in early lactation.     

Technical note: Validation of a system for monitoring rumination in dairy cows

Increased rumination in dairy cattle has been associated with increased saliva production and improved rumen health. Most estimates of rumination are based on direct visual observations. Recently, an electronic system was developed that allows for automated monitoring of rumination in cattle. The objective was to validate the data generated by this electronic (Hi-Tag, SCR Engineers Ltd., Netanya, Israel) rumination monitoring system. Assessments of 2 independent observers were highly correlated (r = 0.99, n = 23), indicating that direct human observations were suitable as the reference method. Measures from the Hi-Tag electronic system were validated by comparing values with those from a human observer for fifty-one 2-h observation periods from 27 Holstein cows. Rumination times (35.1 ± 3.2 min) from the electronic system were highly correlated with those from direct observation (r = 0.93, R² = 0.87, n = 51), indicating that the electronic system was an accurate tool for monitoring this behavior in dairy cows.     

Effect of straw particle size on the behavior,health, and production of early-lactation dairy cows

The objective of this study was to determine the effect of reducing the particle size of wheat straw in a total mixed ration (TMR) on cow behavior, health, and production in early lactation. For 28 d after calving, 41 multiparous Holstein cows were individually provided either 1 of 2 TMR with 9% wheat straw (dry matter basis) chopped (1) using a 2.54-cm screen (short; n = 21) or (2) using a 5.08-cm screen (long; n = 20). Cows were housed in freestall pens during both the dry and lactating period. Enrollment in the trial was on a rolling basis and cows were evenly distributed by parity and milk production between treatments. Wireless telemetry boluses were used to measure reticulorumen pH. Automated systems recorded TMR dry matter intake, milk yield, and rumination activity. The TMR and orts samples were collected every 3 d to determine feed sorting. A particle separator was used to separate feed samples into 4 fractions: long (>19 mm), medium (<19 mm, >8 mm), short (<8 mm, >4 mm), and fine (<4 mm) particles. Feed sorting was calculated as actual intake of each particle fraction expressed as a percentage of its predicted intake. Cows sorted the longest TMR particles differently by treatment; on the long treatment cows sorted against long particles (94.2 ± 1.9%), whereas on the short treatment cows did not sort for or against these particles (99.7 ± 1.9%). Data were analyzed in mixed-effect linear regression models and fitted with polynomial functions over the 28 d of observations. The fitted data indicated treatment differences in linear coefficients, quadratic coefficients, and cubic coefficients for mean time (min/d) below a reticulorumen pH of 5.8 and milk yield. Rumination time (min/d) differed between treatments for quadratic and cubic coefficients. Cows on the short treatment linearly increased in dry matter intake at a greater rate than cows on the long treatment. Mean reticulorumen pH decreased at a greater rate for cows on the long treatment than for cows on the short, as indicated by differences between linear coefficients. Cows on the short treatment tended to produce 75 kg more milk cumulatively during the first 28 d in milk than cows on long treatment. These results suggest that cows fed a diet with longer straw particles selected against physically effective fiber, which may have contributed to greater fluctuations in rumination time, reticulorumen pH, dry matter intake, and milk production in early lactation.     

Effect of modified dry period lengths and bovine somatotropin on yield and composition of milk from dairy cows

Dry periods of 40 to 60 d have been an industry standard because dry periods <40 d have resulted in reduced milk yields in the subsequent lactation by 10 to 30%. However, recent research has demonstrated no production losses for cows given a 30-d dry period. The current study evaluated milk production effects of shortened or omitted dry periods for cows at mature-equivalent production >12,000 kg of milk and treated with bovine somatotropin (bST). The study used 2 commercial dairies and one university dairy and included 4 treatments. Five multiparous and 5 primiparous cows from each farm were assigned to each treatment: 1) 60-d dry period, label use of bST (60DD); 2) 30-d dry period, label use of bST (30DD); 3) continuous milking, label use of bST (CMLST); and 4) continuous milking with continuous use of bST (CMCST). Per label, bST use started at 57 to 70 d in milk and ended 14 d before drying (60DD and 30DD) or expected calving date (CMLST). In primiparous cows, average milk yields during the first 17 wk of lactation were reduced for cows on treatments 30DD, CMLST, and CMCST vs. the 60DD treatment. (38.3, 35.1, and 37.5 vs. 44.1 +/- 1.3 kg/d, respectively). For multiparous cows, respective milk yields did not differ (46.6, 43.4, 46.5, and 47.7 +/- 2.1 kg/d). Shortened or omitted dry periods may impede mammary growth in primiparous cows, resulting in reduced milk yield in the subsequent lactation. In contrast, a shortened or omitted dry period with either bST protocol did not alter production in multiparous cows treated with bST. Quality aspects of prepartum milk and colostrum require additional characterization. For multiparous cows, milk income generated for short dry periods or for continuous milking might increase their profitability. At 17 wk of the subsequent lactation, estimates of the cumulative net margins of multiparous cows on the 30DD treatment and continuous milking treatments exceeded those of cows on the 60DD treatment by 40 dollars to 60 dollars per cow.     

Temporary alterations to postpartum milking frequency affect whole-lactation milk production and the energy status of pasture-grazed dairy cows

This study investigated the immediate and long-term effects of temporary alterations to postpartum milking frequency (MF) on milk production, body condition score (BCS), and indicators of energy status in pasture-grazed cows supplemented with concentrates. Multiparous Holstein-Friesian cows (n = 150) were randomly assigned to 1 of 5 groups at calving: milked twice daily (2×) throughout lactation (control), or milked either once daily (1×) or 3 times daily (3×) for 3 or 6 wk immediately postpartum, and then 2× for the remainder of lactation. During wk 1 to 3 postpartum, cows milked 1× produced 15% less milk and 17% less energy-corrected milk (ECM) than cows milked 2×. This immediate production loss increased to 20% less milk and 22% less ECM during wk 4 to 6 postpartum for cows that remained on 1× milking; these animals also produced less than 1× cows switched to 2× milking after 3 wk. During wk 8 to 32, when all cows were milked 2×, those previously milked 1× had sustained reductions in milk (−6%) and ECM (−8%) yields, which were not affected by the duration of reduced postpartum MF. In contrast, cows milked 3× postpartum had 7% greater milk yields during wk 1 to 6 compared with 2× controls, irrespective of the duration of increased MF. Milk yields also remained numerically greater (+5%) during wk 8 to 32 in cows previously milked 3×. Nevertheless, yields of ECM were not increased by 3× milking, because of lower milk fat and protein contents that persisted for the rest of lactation. In addition, indicators of cow energy status reflected an increasing state of negative energy balance with increasing MF. Cows milked 1× postpartum had greater plasma glucose and lower plasma nonesterified fatty acid concentrations during the reduced MF, and plasma glucose remained lower for 2 wk after cows had switched to 2× milking. Moreover, BCS was improved relative to 2× controls from wk 5 to 6. In contrast, cows milked 3× had lower plasma glucose concentrations, greater plasma nonesterified fatty acid concentrations, and greater BCS loss during wk 1 to 3; however, greater body fat mobilization was not sustained, indicating that additional energy supplements may be required to achieve better milk production responses. In conclusion, temporary 1× milking had lactation-long negative effects on milk and milk component yields but improved cow energy status and BCS, whereas temporary 3× milking immediately increased milk yield but did not improve milk fat and protein yields in pasture-grazed cows.     

Association of residual feed intake with peripartal ruminal microbiome and milk fatty acid composition during early lactation in Holstein dairy cows

Residual feed intake (RFI) is a moderately heritable trait of feed efficiency in dairy cows. The main objective of the present study was to assess potential differences in the ruminal microbiome, milk fatty acid (FA) composition, and plasma concentrations of glucose, nonesterified fatty acids (NEFA), and β-hydroxybutyrate between the most (M-EFF) and the least efficient (L-EFF) dairy cows during early lactation. Forty-seven multiparous Holstein dairy cows with daily ad libitum access to a total mixed ration from 30 d before calving to 30 d in milk were used. Cows were retrospectively classified into M-EFF (i.e., low RFI, n = 29) and L-EFF (high RFI, n = 18) based on a linear regression model. Ruminal digesta and milk samples were collected from each cow at 15 and 30 d in milk for microbiome analysis using 16S rRNA gene sequencing. Microbiome sequencing data were analyzed with the QIIME 2 platform (http://qiime.org/), whereas the microbiome statistical analyses and visual explorations were performed using the web-based MicrobiomeAnalyst platform. Milk FA composition was measured via gas chromatography-mass spectrometry. The statistical model used in SAS 9.4 (SAS Institute Inc.) included RFI, time, and their interactions as fixed effects. The cor() function in R programming was used to determine Pearson correlations between relative abundance of significant bacteria and milk FA. Overall, daily milk yield did not differ due to RFI and averaged 42 ± 1.6 kg for L-EFF and 43 ± 1.3 kg for M-EFF cows. However, M-EFF cows had lower overall dry matter intake (14.9 ± 0.5 kg/d) compared with L-EFF cows (19.2 ± 0.6 kg/d). No incidence of clinical disease was recorded for cows in the study. Compared with L-EFF, overall glucose concentration was lower, whereas NEFA and β-hydroxybutyrate concentrations were greater in M-EFF cows. Ruminal digesta from both RFI groups had similar bacterial composition, but differed in the relative abundance of some bacteria. Compared with L-EFF, M-EFF cows had greater relative abundance of Lachnospiraceae, Lachnoclostridium, Papillibacter, Desulfovibrio, Sphaerochaeta, Acetobacter, and Histophilus. In contrast, relative abundance of Bifidobacterium, Ruminiclostridium, Prevotellaceae, and Erysipelotrichaceae bacterium was lower in M-EFF cows. Compared with L-EFF, M-EFF cows had greater proportions of long-chain monounsaturated FA, including 16:1 trans-9, 16:1 cis-9, 17:1 trans-10, 17:1 cis-10, 18:1 cis-9, 18:1 cis-11, whereas proportions of medium-chain saturated and 16:0 were lower in M-EFF. Acetate-producing bacteria (Sphaerochaeta and Acetobacter) were positively and significantly correlated (r ≥ 0.24) with concentrations of 16:1 cis-9 and 17:1 cis-10, whereas Prevotellaceae was significantly and negatively correlated (r = ?0.25) with these FA. Butyrate-producing bacterium (Papillibacter) had a significant negative correlation (r = ?0.27) with concentration of 15:0. Overall, data suggested that feed-efficient cows have unique profiles of ruminal microbiota, some of which are correlated with concentrations of milk FA during early lactation.     

Effects of winter housing system on hygiene,udder health,frostbite, and rumination of dairy cows

The objective of this study was to evaluate the effects of 2 winter (December to April) housing systems on dairy cow hygiene scores, frostbite, teat condition, clinical mastitis, and activity and rumination across 3 winter seasons (2013, 2014, and 2015). Certified-organic cows (n = 268) were randomly assigned to 2 treatments (2 replicates per system): (1) outdoor straw pack (outdoor) or (2) 3-sided compost-bedded pack barn (indoor). Cows calved during 2 seasons (spring or fall) at the University of Minnesota West Central Research and Outreach Center, Morris, Minnesota, organic dairy. Organic wheat straw was used as bedding for the 2 outdoor straw packs, and bedding was maintained by farm management to keep cows dry and absorb manure throughout the winter. The compost-bedded pack barn (2 pens in the barn) was bedded with organic-approved sawdust, and the bedding material was stirred twice per day with a small chisel plow. Hygiene scores were recorded biweekly as cows exited the milking parlor. Incidence of clinical mastitis was recorded in a binary manner as treated (1) or not treated (0) at least once during a lactation. Frostbite incidence was collected monthly. Activity and rumination times (daily and 2-h periods) were monitored electronically using a neck collar sensor (HR-LD Tags, SCR Dairy, Netanya, Israel). Indoor cows had greater udder hygiene scores (1.75 vs. 1.46) and greater abdomen hygiene scores (1.79 vs. 1.43) compared with outdoor cows. Additionally, the indoor cows had greater upper and lower leg hygiene scores compared with outdoor cows. Incidence of clinical mastitis was greater for indoor cows compared with outdoor cows (27.1% vs. 15.1%, respectively). Frostbite incidence was not different between indoor (30.1%) and outdoor (17.5%) cows. Daily rumination was 509 min/d for indoor cows and 530 min/d for the outdoor cows. In summary, lactating cows housed outdoors on straw-bedded packs had cleaner udders and improved udder health compared with cows housed in a compost-bedded pack barn.     

Association of days in close up,gestation length,and rumination around time of calving with disease and pregnancy outcomes in multiparous dairy cows

The purpose of this study was to evaluate the effect of rumination times and days spent in a close-up group before calving (DCU) on early-lactation health and reproductive outcomes in dairy cows. Data were gathered for 719 cows located in a single herd. Herd management and reproductive records were analyzed for cows receiving treatment in the first 30 d of lactation (days in milk; DIM) for clinical mastitis, reproductive tract disease, ketosis, milk fever, and displaced abomasum. Rumination times for each cow were downloaded daily from the herd's automated collar system used to generate heat and health alerts for each cow beginning at 21 d precalving until 14 d postcalving. During the first 30 DIM, 121 cows (18%) developed at least 1 disease—any combination of ketosis (40 cows, 5.9% of total), mastitis (17 cows, 2.5%), metritis (75 cows, 11%), milk fever (17 cows, 2.5%), or displaced abomasum (28 cows, 4.1%); 305 cows (45%) were pregnant again at 100 DIM, and an additional 139 cows (20%) were pregnant at 150 DIM. Principal component analysis was used to determine the relationship between gestation length and DCU and their association with the odds of developing disease in early lactation. We did not find any significant association between precalving rumination time and disease within the first 30 DIM. Higher rumination time in the week before calving was shown to be strongly linked to a shorter time to subsequent pregnancy, whereas rumination times postcalving were not associated with changes in the time to pregnancy. Principal component analysis showed that a curvilinear combination of gestation length and DCU (principal component 1) was significantly associated with changes in disease incidence in the first 30 DIM. Gestation length and time spent in close up are important management factors in reducing the incidence of disease in early lactation, and rumination times around calving may help predict future reproductive outcomes.     

Technical note: An evaluation of technology-recorded rumination and feeding behaviors in dairy heifers

Precision dairy monitoring technologies have become increasingly popular for recording rumination and feeding behaviors in dairy cattle. The objective of this study was to validate the rumination and feeding time functions of the CowManager SensOor (Agis, Harmelen, the Netherlands) against visual observation in dairy heifers. The study took place over a 44-d period beginning June 1, 2016. Holstein heifers equipped with CowManager SensOor tags attached according to manufacturer specifications (n = 49) were split into 2 groups based on age, diet, and housing type. Group 1 heifers (n = 24) were calves (mean ± SD) 2.0 ± 2.7 mo in age, fed hay and calf starter, and housed on a straw-bedded pack. Group 2 heifers (n = 25) were 17.0 ± 1.3 mo in age, fed a TMR, confirmed pregnant, and housed in freestalls. Visual observation shifts occurred at 1500, 1700, 1900, and 2100 h. Each heifer was observed for 2 hour-long periods, with both observation periods occurring on the same day. Visual observations were collected using a synchronized watch, and “start” and “stop” times were recorded for each rumination and feeding event. For correlations, data from CowManager SensOor tags and observations were averaged, so a single 1-h observation was provided per animal, reducing the potential for confounding repeated measures being collected for each animal. Concordance correlations (CCC; epiR package; R Foundation for Statistical Computing, Vienna, Austria) and Pearson correlations (r; CORR procedure; SAS Institute Inc., Cary, NC) were used to calculate association between visual observations and technology-recorded behaviors. Visually observed rumination time was correlated with the CowManager SensOor (r = 0.63, CCC = 0.55). Visually observed feeding time was also correlated with the CowManager SensOor (r = 0.88, CCC = 0.72). The difference between technology-recorded data and visual observation was treated as the dependent variable in a mixed linear model (MIXED procedure of SAS). Time of day, age in months, and group were treated as fixed effects. Individual heifers were treated as random and repeated effects. The effects of time of day, age, and group on rumination and feeding times were not significant. The CowManager SensOor was more effective at recording feeding behavior than rumination behavior in dairy heifers. The CowManager SensOor can be used to provide relatively accurate measures of feeding time in heifers, but its rumination time function should be used with caution.     

Eating behavior,milk production,rumination, and digestibility characteristics of high- and low-efficiency lactating cows fed a low-roughage diet

This study aimed to identify individual characteristics differing among high-efficiency (HEf; upper 20%, n = 31), low-efficiency (LEf; lower 20%, n = 31), and mid-efficiency (MEf, 60% n = 93) lactating cows. Primiparous (37) and multiparous (118) high-producing milking cows at 30 to 180 d in milk were fed individually a low-roughage diet [31.6% of dry matter (DM)] for 4 wk. Daily average DM intake, rate of eating, visit duration, meal size, and daily rumination time were higher in LEf compared with HEf cows. On the other hand, HEf cows exhibited higher digestibility of DM, crude protein, and neutral detergent fiber than the LEf cows. Daily eating time was similar in the HEf and LEf groups and higher than that of the MEf cows. Visit and meal frequency, average visit and meal duration, daily lying time, and pedometer activity were similar in the HEf, LEf, and MEf groups. The HEf cows produced 1.75% more milk, but similar energy-corrected milk compared with the LEf cows. Milk fat and protein content were lower by 1.8 and 3.8%, respectively, in the HEf cows than in the LEf group. Body weight (BW) and BW gain were similar in the 3 efficiency groups. Diurnal distribution of DM intake showed 6 distinct major meals, each composed of 1.1 to 1.6 visits. Higher intake peaks (greater meal size) were found in the LEf cows compared with the HEf group. Daily DM intake was highly correlated (affected) with energy-corrected milk production (r = 0.61), BW (r = 0.4), eating rate (r = 0.57), and visit size (r = 0.54). Energy balance showed that the lower efficiency of the LEf cows was attributed to their excess heat production and energy loss.     

Short communication: Heart rate variability,step, and rumination behavior of dairy cows milked in a rotary milking system

Step behavior, heart rate (HR), the high-frequency (HF) component of heart rate variability (HRV), the ratio of the low-frequency (LF) and HF components (LF/HF ratio) as well as rumination behavior during milking were investigated in dairy cows milked in a high-capacity rotary milking system (n = 49) to study animals' stress responses to the milking process. Cardiac parameters were analyzed for undisturbed standing (baseline) and for the stages of the morning, afternoon, and evening milking processes (i.e., driving animals from the barn to the pre-milking holding pen, pre-milking holding pen, preparation, milking, and waiting after milking in the milking stall). During driving, HR was greater than during all other stages. After driving, a gradual decrease in HR was observed. The HF decreased during driving, indicating a decrease in vagal tone compared with baseline. When animals were in the holding pen, vagal tone decreased, whereas sympathetic tone increased with lower values than recorded for baseline and driving. During preparation, HF values were still lower than those recorded for baseline. The recovery of the autonomic activity was observed following preparation as indicated by increased HF and decreased LF/HF ratio during milking and waiting stages. During milking, 53.1% of the animals ruminated. The frequency of steps was greater during preparation (3.7 ± 1.8 steps/min) than during milking (0.7 ± 0.4 steps/min) and waiting after milking (1.6 ± 1.0 steps/min). Our results suggest that being in the holding pen is stressful for cows; however, vagal predominance from the onset of milking, the low frequency of steps, and the high prevalence of rumination during milking suggest a possible welfare benefit of the investigated rotary milking system.