Short communication: Flooring preferences of dairy cows at calving

The present study investigated the flooring preference during the 30 h before parturition in Holstein dairy cows housed individually in a maternity pen. Seventeen multiparous cows were moved, on average, 2 d before expected calving date into an individual maternity pen with 3 different flooring surfaces: 10 cm of sand, pebble-top rubber mats, or concrete flooring, each covered with 15 cm of straw. Calving location, lying time, and total time and number of lying bouts on each of the floor types were recorded during 2 periods: precalving (24 to 29 h before calving) and at calving (0 to 5 h before calving). Ten cows calved on sand, 6 on concrete, and 1 on the rubber mat. Lying bouts increased during the hours closest to calving, regardless of flooring. The number of lying bouts did not differ between flooring types precalving but cows had more lying bouts on sand and concrete compared with rubber at calving. Cows spent more time lying down on sand and concrete compared with rubber precalving, but lying times did not differ between treatments at calving. Cows that calved on sand spent more time lying on sand at calving compared with the other 2 flooring types. Cows that calved on concrete did not show a flooring preference at calving. These results indicate that rubber mats are the least preferred by dairy cows in the maternity pens, even when covered with a deep layer of straw.     

Short communication: Genetic relationships between the Holstein cow populations of three European dairy countries

The degree of relatedness was studied in 3 dairy cow populations from Great Britain (GBR), Italy (ITA), and Ireland (IRL) by using cows born from 2003 to 2006. Effective population size, inbreeding coefficient (F), and average relationship in the top and bottom 4,000 cows ranked on a profit index value (PIV) or milk yield evaluations were studied. Average inbreeding was approximately 2% in GBR and ITA, was 1% in IRL, but was slightly more than 2% when the joint pedigree was used. The average F for the joint population was 10 to 15% higher than estimates averaged across the 3 populations, reflecting the increased completeness of pedigree information in the joint pedigree. Effective population size in the joint pedigree was approximately 12% lower than estimates within the individual countries. The average genetic relationships for the top 4,000 PIV cows were not markedly different from those based on milk evaluation in GBR and ITA, but were approximately 2% lower in IRL. This was due to the use of an index with less weight on production traits in IRL compared with GBR and ITA. However, selection of the top 4,000 cows on PIV reduced the degree of relatedness across the 3 countries. The use of common sires accounted for most of the relatedness across the 3 countries, more than did the use of related sires or common foreign dams.     

Short communication: Repeatability of measures of rectal temperature in dairy cows

Although taking body temperature by rectal thermometer is the method most commonly used to identify sick cows in the postpartum period, no data on the repeatability of this measure are available. The overall objective of this study was to evaluate variability of rectal temperatures in dairy cows considering different factors (intra- and interinvestigator repeatability, different thermometers, penetration depth into the rectum, and defecation). High coefficients of correlation (r = 0.98) and small differences between values of rectal temperatures (observer A = 39.3 ± 1.0°C and observer B = 39.4 ± 1.0°C) provide evidence that rectal temperature was a repeatable measure in dairy cows. Testing was carried out using 4 different digital thermometers: GLA M750 (GLA Agricultural Electronics, San Luis Obispo, CA), MTI8101 (SES Scala Electronics, Stahnsdorf, Germany), MT1831 (Microlife AG, Widnau, Switzerland) and Domotherm TH1 (Uebe Medical GmbH, Wertheim, Germany). Thermometers were inserted into the rectum to a certain depth (GLA M750 and MTI8101 = 11.5 cm; MT1831 = 8.4 cm; Domotherm TH1 = 7.7 cm) and a measure was finished when a visual or acoustic signal was emitted by the thermometer. The measures could be influenced by the procedure itself (up to 0.5°C), type of thermometer (up to 0.3°C), and the penetration depth (11.5 cm or 6.0 cm in one of the experiments) into the rectum (up to 0.4°C difference between a penetration depth of 11.5 cm and 6.0 cm in one of the experiments). Differences in rectal temperature before and after defecation were minor (<0.1°C). These results indicate that some care is required in generalizing rectal measures of body temperature.     

Short communication: Rumination and feeding behavior before and after calving in dairy cows

The objectives of the current study were to describe changes in rumination and feeding behavior around calving. Rumination time, feeding time, and dry matter intake were monitored in 11 freestall-housed cows from 96 h before to 48 h after calving. Data were summarized in 2-h and 24-h periods, adjusting for calving time. Differences between baseline (96 to 24 h before calving) and subsequent 24-h periods were evaluated. Compared with baseline, cows spent, on average, 63 ± 30 min/24 h less time ruminating and 66 ± 16 min/24 h less time feeding in the 24-h period before calving. These behaviors continued to decline during the 24-h period after calving when, compared with baseline, time spent ruminating decreased on average by 133 ± 35 min/24 h and time spent feeding decreased by 82 ± 18 min/24 h. Dry matter intake tended to decrease by 3.8 ± 1.9 kg in the 24-h period before calving but returned to baseline values in the 24-h following calving. Rumination time and time spent feeding started to decline approximately 4 and 8 h before calving, respectively, and increased in the 4 to 6 h following calving. Rumination time and time spent feeding show promise as tools to identify cows close to calving.     

Short communication: Plasma concentration of glucose-dependent insulinotropic polypeptide may regulate milk energy production in lactating dairy cows

In dairy cows, an increase in plasma concentration of glucose-dependent insulinotropic polypeptide (GIP) is associated with an increase in metabolizable energy intake, but the role of GIP in energy partitioning of dairy cattle is not certain. The objective of this study was to examine the relationship between plasma GIP concentrations and energy partitioning toward milk production. Four mid-lactation, primiparous, rumen-fistulated Holstein-Friesian cows were fed a control diet of 55% forage and 45% concentrate [dry matter (DM) basis] in a 4 × 4 Latin square design with 4-wk periods. The 4 treatments were (1) control diet fed at 1000 and 1600 h, and (2) once-daily (1000 h) feeding, (3) twice-daily (1000 and 1600 h) feeding, and (4) 4 times/d (1000, 1600, 2200 and 0400 h) feeding of the control diet plus 1 dose (1.75 kg on a DM basis at 0955 h) into the rumen of supplemental vegetable proteins (Amino Green; SCA NuTec Ltd., Thirsk, UK). Measurements of respiratory exchange and energy balance were obtained over 4 d during the last week of each period while cows were housed in open-circuit respiration chambers. Blood was collected from the jugular vein every 30 min for 12 h, using indwelling catheters, starting at 0800 h on d 20 of each period. Plasma GIP concentration was measured in samples pooled over each 5 consecutive blood samplings. The relationships between plasma GIP, DM intake, heat production, respiratory quotient (RQ), milk yield, and milk energy output were analyzed using linear correlation procedures, with metabolizable intake as a partial variant. Plasma GIP concentration was not correlated with heat production, or milk yield, but was positively correlated with milk energy yield (correlation coefficient = 0.67) and negatively correlated with RQ (correlation coefficient = −0.72). The correlations between GIP with RQ and milk energy output do not imply causality, but support a role for GIP in the regulation of energy metabolism in dairy cows.     

Short communication: Added value of rumination time for the prediction of dry matter intake in lactating dairy cows

The objective of the current study was to quantify the change in the prediction of dry matter intake (DMI) resulting from the inclusion of rumination time (RT) in the 2001 National Research Council (NRC) DMI prediction model. Forty-one Holstein cows fed the same total mixed ration were involved in a 10-wk study. Individual DMI were measured daily. The accuracy and precision of the original NRC prediction model, based on body weight, fat-corrected milk, and week of lactation as independent variables, was compared with the accuracy and precision of the same model with RT as an additional independent variable. The RT estimate was significant in the model developed but had a low value (0.031 kg/h). Root mean square prediction errors were very similar in the 2 models (1.70 and 1.68 kg/d) as were the other indicators (R², linear bias, random error, and concordance correlation coefficient) selected to compare the models in this study. These results indicate no gain in DMI prediction precision or accuracy when RT is included in the NRC model.     

Short communication: Changes in heart rate variability of dairy cows during conventional milking with nonvoluntary exit

Heart rate variability (HRV), as a physiological measure of animal welfare, was investigated in 36 cows milked in a parallel milking parlor with nonvoluntary exit. Heart rate variability parameters measured during the morning resting (baseline period) were compared with those measured during different stages of the entire milking process. No differences were found in HRV parameters between the baseline period, preparation, and main milking. A considerable reduction in vagal activity was detected during the movement of the cows to the milking parlor (driving) and while cows were in the holding area. The parasympathetic measures of HRV decreased whereas the sympatho-vagal balance increased compared with baseline. The same pattern was observed regarding the stage between removing the teat cups and leaving the milking parlor (waiting). No differences in any sympathetic measures were observed between the baseline period and any of the milking stages. These findings indicate that the milking process itself (preparation and main milking) is not stressful for cows. Decreased parasympathetic activity during driving might be the result of the physical activity of the cows, whereas waiting in the holding area and in the milking stall after milking caused stress for animals.     

Short communication: Relationship between the efficiency of utilization of feed nitrogen and N enrichment in casein from lactating dairy cows

The objective of the present study was to evaluate the relationship between the efficiency of conversion of feed N into milk N [N-use efficiency (NUE)] and ¹⁵N enrichment of milk casein from lactating cows fed corn silage-based diets. Samples of feeds and milk were obtained from 3 experiments with lactating dairy cows. All diets were based on corn silage and were designed to evaluate the effects of (1) diets with different ratios of effective rumen-degradable protein to fermentable metabolizable energy (experiment 1), (2) different proportions of quickly and slowly rumen-degradable protein (experiment 2), and (3) synchronizing the availability of fermentable metabolizable energy and effective rumen-degradable protein in the rumen (experiment 3). Although no significant effect of diet on casein δ¹⁵N values was detected, casein was more enriched than the diet in each of the experiments. Nitrogen-use efficiency was negatively related to adjusted Δ¹⁵N (casein δ¹⁵N − diet δ¹⁵N) for experiments 1 and 2 individually and when combining data from all 3 experiments. The relatively low values for Δ¹⁵N suggest that these productive animals were using dietary N efficiently, with a high proportion of N going to milk protein and less to urea. The weak, although significant, relationship between NUE and adjusted Δ¹⁵N, is consistent with relatively little variation in hepatic deamination and transamination, with variation in rumen efficiency having the predominant effect on NUE. The present study confirms the lower ¹⁵N enrichment in protein when NUE is high and the potential to use N-isotope fractionation as a marker of NUE.     

Short communication: Automatic washing of hooves can help control digital dermatitis in dairy cows

The objectives of this study were to develop and test a system for automatic washing of the hooves of dairy cows and to evaluate the effect of frequent automatic washing on the prevalence of digital dermatitis (DD). An automatic hoof washer was developed in an experimental dairy herd and tested in 6 commercial dairy herds in 2 experiments (1 and 2). In the experimental herd, automatic hoof washing resulted in cleaner hooves. In experiments 1 and 2, cows were washed after each milking on the left side only, leaving the right side unwashed as a within-cow control. In experiment 1, hooves were washed with a water and 0.4% soap solution. In experiment 2, hooves were washed with water only. In each experiment, DD was scored in a hoof-trimming chute approximately 60 d after the start of hoof washing. Data were analyzed using a generalized linear mixed model. The outcome was the DD status of each leg (DD positive or DD negative). Herd and cow within herd were included as random effects, and treatment (washing or control) was included as a fixed effect. The statistical analyses showed that the odds ratio of having DD was 1.48 in the control leg compared with the washed leg in experiment 1. In experiment 2, the odds ratio of having DD was 1.27 in the control leg compared with the washed leg. We concluded that automatic washing of hooves with water and soap can help decrease the prevalence of DD in commercial dairy herds.     

Short communication: Effects of molasses supplementation on performance of lactating cows fed high-alfalfa silage diets

Twelve Holstein cows were used in a replicated Latin square experiment to determine the effect of adding dried molasses to high-alfalfa silage diets on dairy cow performance. Three isonitrogenous diets were formulated with a 68:32 forage:concentrate ratio, with alfalfa silage as the only forage source. Dietary treatments were a control diet with no added molasses and 3 and 6% dried molasses diets. Three lactating Holstein cows fitted with ruminal cannulas were used to determine the effects of dietary treatments on ruminal fermentation. Dietary treatments had no effect on dry matter (average 23.3 kg/d), crude protein (average 4.4 kg/d), or neutral detergent fiber (average 7.4 kg/d) intake. Milk yield, energy-corrected milk (average 35.4 kg/d), and 4% fat-corrected milk (average 33.8 kg/d) were not influenced by dietary treatments. Cows fed the control diet produced milk with less milk urea nitrogen concentration than those fed molasses-supplemented diets. Ruminal pH, NH₃-N concentration, and total volatile fatty acids were not different among dietary treatments. The molar proportion of acetate linearly increased, whereas the molar proportion of propionate linearly decreased as the level of dried molasses increased. It was concluded that addition of dried molasses to high-alfalfa silage diets at 6% of the diet (dry matter basis) increased milk urea nitrogen but had no effect on animal performance.     

Short communication: Heritability of milk fatty acid composition and stearoyl-CoA desaturase indices in dairy cows

Activity of stearoyl-CoA desaturase (SCD) in the mammary gland is important for determining the relative proportions of saturated and monounsaturated fatty acids in milk and the concentration of the conjugated linoleic acid isomer rumenic acid (RA; cis-9,trans-11 18:2). Previous studies identified a large degree of between-cow variation in SCD activity, which was consistent across diets and suggests a genetic influence. The objectives of this study were to quantify genetic and phenotypic variations in fatty acid concentrations and SCD indices in milk fat and to estimate their heritabilities in a population of United Kingdom dairy cows. Milk samples were collected from 2,408 daughters of 597 Holstein-Friesian sires on 325 commercial farms for determination of fatty acid profiles. Indices of SCD activity were calculated by expressing each SCD product (cis-9 14:1, cis-9 16:1, cis-9 18:1, and RA) as a proportion of the precursor plus product [e.g., SCDI₁₄ = cis-9 14:1/(14:0 + cis-9 14:1)]. For individual fatty acids, phenotypic variance was considerably greater than additive genetic variance, resulting in small and nonsignificant heritability estimates (± standard error) for all except 6:0 (h² = 0.27 ± 0.10), 8:0 (h² = 0.27 ± 0.09), 12:0 (h² = 0.13 ± 0.07), cis-9 14:1 (h² = 0.28 ± 0.10), and cis-9 18:1 (h² = 0.12 ± 0.07). Heritability estimates of desaturase indices were significant for SCDI₁₄ (h² = 0.38 ± 0.11), SCDI₁₈ (h² = 0.19 ± 0.09), and SCDI_RA (h² = 0.21 ± 0.09), but not for SCDI₁₆ (h² = 0.05 ± 0.06). This study provides evidence that additive effects are responsible for a significant proportion of the phenotypic variation in SCD activity in dairy cows. It is concluded that because heritability of desaturase indices is moderate and significant in many cases, these indices could be investigated further for use in future breeding programs to increase concentrations of monounsaturated fatty acids and RA while decreasing concentrations of saturated fatty acids in milk fat.     

Short communication: Effects of dietary nonstructural carbohydrates pre- and postpartum on reproduction of grazing dairy cows

The working hypothesis was that postpartum anovulatory intervals (PPAI) of grazing dairy cows are shortened by inclusion of concentrates that increase the nonstructural carbohydrate content of the transition diet. Dietary treatments were arranged as a 2 × 2 factorial, with 68 multiparous cows assigned to isoenergetic diets (114 MJ of metabolizable energy/cow per day) of pasture and pasture silage (PreP) or pasture and pasture silage supplemented with 3 kg of dry matter/cow per day a corn- and barley-based concentrate for 36 d prepartum (PreC). After calving, cows within each prepartum diet group were managed on isoenergetic diets (179 MJ of metabolizable energy/cow per day) of either pasture and pasture silage (PostP) or pasture and pasture silage supplemented with 5 kg of dry matter/cow per day a corn- and barley-based concentrate (PostC) for at least 35 d and until reestablishment of ovulatory cycles. Relative to day of calving (d 0), blood samples were collected at least weekly from d −28 to 35 and milk samples were collected twice weekly for progesterone determination to diagnose ovulatory status. The main variable of interest was PPAI, defined as the interval between calving and the first detected increase in milk progesterone (>3 ng/mL), followed by a pattern of progesterone concentrations consistent with onset of an ovulatory cycle. Subsequent mating records, pregnancy testing, and recalving data were also examined. Prepartum diet did not affect reproduction. The PPAI was 8 d shorter and the 6-wk pregnancy rate was 17% greater in PostC cows compared with PostP cows. Measured indicators of metabolic state and energy balance were poorly related to PPAI. The results support the existence of nutritional signals associated with nonstructural carbohydrates in the postpartum diet, independent of energy balance; these signals benefit the physiological mechanisms underlying the timing of first ovulation and possibly subsequent breeding performance.     

Short communication: Lameness impairs feeding behavior of dairy cows

The automated, reliable, and early detection of lameness is an important aim for the future development of modern dairy operations. One promising indicator of lameness is a change in the feeding behavior of a cow. In this study, the associations between feeding behavior and lameness were evaluated. A herd of 50 cows was investigated during the winter season in a freestall barn. Feeding behavior, feed intake, milk yield, and body weight were monitored using electronic feeding troughs and an automated milking system. Gait scoring every second week was used as a measure of lameness. To analyze the effect of lameness on feeding behavior and milk yield, linear mixed models were used. Cows with more severe lameness spent less time feeding per day (104 ± 4, 101 ± 4, and 91 ± 4 min/d for lameness scores 2, 3, and 4, respectively). An interaction between parity and lameness score was detected, with severely lame primiparous cows spending the least time feeding. Severely lame cows fed faster; however, their body weights were lower than for less-lame cows. Increase in lactation stage was associated with longer daily feeding time, longer duration of feeding bouts, and lower feeding rate. Worsening of gait was associated with lower silage intake and less time spent feeding even before severe lameness was scored. The results indicate that lameness is associated with changes in feeding behavior and that such changes could be considered in the future development of remote monitoring systems. It should also be noted that impaired feeding behavior along with lameness can put the welfare of especially early lactating primiparous cows at risk.     

Short communication: Circulating and milk adiponectin change differently during energy deficiency at different stages of lactation in dairy cows

Adiponectin, one of the most abundant adipokines in circulation, is known for its role in regulation of body metabolism. The aim of this study was to evaluate the effects of a negative energy balance (NEB) at 2 stages of lactation (lactational NEB at the onset of lactation and an induced NEB by feed restriction near 100 d of lactation) on circulating adiponectin concentrations. We also investigated the effect of feed restriction on adiponectin concentrations in milk and the relationships of blood and milk adiponectin with selected plasma or milk variables and with measures of body condition. Plasma adiponectin was measured in 50 multiparous Holstein dairy cows throughout 3 experimental periods [i.e., period 1 = 3 wk antepartum up to 12 wk postpartum, period 2 = 3 wk of feed restriction starting at around 100 d in milk with a control (n = 25) and feed-restricted group (50% of energy requirements; n = 25), and period 3 = subsequent realimentation period for 8 wk]. Milk adiponectin was investigated among 21 multiparous cows at wk 2 and wk 12 of period 1 and wk 2 of period 2. Adiponectin concentrations in plasma and skim milk were measured using an in-house ELISA specific for bovine adiponectin. Major changes in circulating adiponectin concentrations were observed during the periparturient period, whereas energy deficiency during established lactation at around 100 d in milk and subsequent refeeding did not affect plasma adiponectin. Together with lower adiponectin concentrations in milk (µg/mL), the reduction in milk yield led to decreased adiponectin secretion via milk (mg/d) at the second week of feed restriction. Irrespective of time and treatment, milk adiponectin represented about 0.002% of total milk protein. Mean adiponectin concentrations in milk (0.61 ± 0.03 µg/mL) were about 92% lower than the mean plasma adiponectin concentrations (32.1 ± 1.0 µg/mL). The proportion of the steady-state plasma adiponectin pool secreted daily via milk was 2.7%. In view of the similar extent of NEB in both periods of energy deficiency, decreasing adiponectin concentrations seems important for accomplishing the adaptation to the rapidly increasing metabolic rates in early lactation, whereas the lipolytic reaction toward feed restriction-induced NEB during established lactation seems to occur largely independent of changes in circulating adiponectin.     

Short communication: Performance of lactating dairy cows fed pearl millet grain

Fifteen multiparous Holstein cows were used in a 3 × 3 Latin square experiment to determine the effects of feeding pearl millet grain on feed intake, milk yield, and milk composition of lactating dairy cows. Three isonitrogenous diets with a 57:43 forage:concentrate ratio were formulated. Diets contained 30% corn, 30% pearl millet, or 31% corn and pearl millet mixed 1:1 (wt/wt). Three lactating Holstein cows fitted with ruminal cannulas were used to determine the effects of dietary treatments on ruminal fermentation parameters. Dry matter intake and energy-corrected milk were similar for all dietary treatments and averaged 23.8 and 33.5 kg/d, respectively. Dry matter intake (% of BW) was unaffected by dietary treatments and averaged 3.40%. Milk fat, protein, lactose, and total solids concentrations were not influenced by grain type. Ruminal NH₃-N concentration was unaffected by dietary treatments. However, ruminal pH tended to be lower for cows fed pearl millet than those fed corn and pearl millet mix. It was concluded that pearl millet grain can replace corn in dairy cow diets up to 30% of the diet DM with no adverse effects on milk yield or milk composition.     

Short communication: Relationship between natural antibodies and postpartum uterine health in dairy cows

Postpartum uterine diseases of dairy cows compromise animal welfare and may result in early removal from the herd or impaired reproductive performance. The relationship between poor immune status around calving and uterine diseases is well established; however, that between natural antibodies (NAb) and uterine health has not yet been studied. The objective of this study was to evaluate the association of circulating NAb levels around parturition with puerperal metritis, clinical endometritis, and the intrauterine presence of the Escherichia coli virulence factor FimH. One hundred six pregnant heifers were enrolled; NAb in serum samples collected at 30 ± 3 d prepartum and at 2 ± 1 and 35 ± 3 d in milk (DIM) were measured by ELISA. Puerperal metritis was defined as the presence of fetid, watery, red-brown uterine discharge and rectal temperature >39.5°C at 6 ± 1 DIM. Clinical endometritis was defined as presence of pus in the uterine lavage sample collected at 35 ± 3 DIM. The intrauterine presence of the fimH gene at 2 ± 1 DIM was evaluated by PCR. The overall optical density (wavelength of 650 nm) of ELISA-detected serum NAb was lower for cows diagnosed with puerperal metritis than for cows that did not have puerperal metritis. Additionally, cows diagnosed with clinical endometritis tended to have lower levels of NAb than did cows without clinical endometritis. Finally, FimH-positive cows had lower overall levels of serum NAb compared with FimH-negative cows. In conclusion, NAb detected in serum around parturition was associated with uterine health of dairy cows.     

Short communication: Comparison of 3 solid digesta passage markers in dairy cows

This study investigated the usefulness of acid-detergent fiber-bound ¹⁵N [acid detergent insoluble (ADI)-¹⁵N] as a solid digesta passage marker in dairy cows compared with chromium (Cr) and ytterbium (Yb) (as labeled fiber or forage, respectively). Intrinsically (ADI-¹⁵N) or extrinsically (Cr, Yb) labeled alfalfa hay was pulse-dosed intraruminally to 7 lactating dairy cows. Following marker administration, spot fecal samples were collected for up to 72 h for marker analyses. Urine and milk samples were also collected and analyzed for Yb and Cr. Fecal marker excretion data were processed using 2-compartment mathematical age-dependent/age-independent (G_n→G₁) models. The rate of passage of the marker in the first, age-dependent compartment tended to be slower for Yb compared with Cr and ADI-¹⁵N, which resulted in a trend for longer mean retention time (MRT) in this compartment when Yb was used as a marker (19.0 h) compared with Cr and ADI-¹⁵N (14.5 and 13.9 h, respectively). The rate constant of marker disappearance for the second or age-independent compartment tended to be greater for Yb compared with Cr and ADI-¹⁵N, which led to a shorter MRT of Yb in this compartment (15.6) versus ADI-¹⁵N (32.1) and Cr (24.8 h). The cumulative MRT was greater for ADI-¹⁵N versus Cr and Yb (46.0, 39.3, and 34.4 h, respectively). Total MRT of marker tended to be greater for ADI-¹⁵N than for Yb (46.6 vs. 36.6 h, respectively). Urine and milk analyses data suggested no measurable losses of Yb along the digestive tract, but about 0.79% of Cr dosed intraruminally was secreted or excreted in milk and urine in the 48-h period following marker administration. Collectively, this study confirmed previous observations that ADI-¹⁵N can be used reliably as a solid digesta passage marker for ruminants, producing pre-duodenal and total-tract retention times similar to that of Cr-labeled fiber. Retention time in the age-independent compartment was underestimated when Yb was used as a marker, emphasizing the need to process forages to isolate fiber before labeling with Yb.     

Short communication: Serum osteoprotegerin concentrations in periparturient dairy cows

Dairy cows experience hypocalcemia at the onset of lactation; however, the contribution of bone metabolism to circulating Ca concentrations during the periparturient period is not well understood. Osteoprotegerin (OPG) protects against loss of skeletal mass by regulating osteoclastogenesis. We previously reported that the bone resorption increased around parturition in dairy cows from the perspective of bone markers in blood. The aim of this study was to explore osteoclastic bone resorption in periparturient dairy cows by measuring changes in serum OPG concentrations around calving. The OPG concentrations were evaluated in primiparous (n = 9) and multiparous (n = 9) cows at 21 d precalving and over 5 d after calving. Based on mixed model analyses, the multiparous cows had a higher serum OPG concentration than primiparous cows at precalving and exhibited a significant decline in serum OPG and Ca concentrations after calving. In contrast to multiparous cows, primiparous cows did not exhibit these changes. Therefore, we hypothesized that multiparous cows preserve their bone mineral content during late pregnancy and activate the osteoclastic bone resorption after calving. Based on our serum OPG data, we identified the different periparturient osteoclastic bone resorption patterns in healthy primiparous and multiparous dairy cows.