Dry Period Length Research Articles

Risk factors for peri-parturient farmer diagnosed mastitis in New Zealand dairy herds: findings from a retrospective cohort study

Risk factors associated with the development of clinical mastitis (CM) in multiparous cows, defined as detection of abnormalities in the milk by farm staff in the 30days before and 90days after calving were studied using a retrospective longitudinal cohort study of 18,162 cows on 30 South Island commercial New Zealand dairy farms. Risk factors studied included age, breed, length of dry period, farm, herd size, yield and individual somatic cell count (ISCC) status 30–60days before the end of the previous lactation, rainfall at calving and number calving on the same day. A modified Cox Proportional hazards model with time varying effects for breed, age, length of dry period and ISCC was used to identify which factors were significantly associated with an increased hazard of CM after calving Rainfall at calving >10mm increased the hazard ratio (HR) by 1.14 (95%CI=1.01–1.30) for 30days before to 90days after calving. Milk production >1.5kgMS/cow/day in the 30–60days before the end of lactation increased the HR for CM by 1.36 (95%CI=1.21–1.52) for the same period. The effects of breed, age, length of dry period and ISCC 30–60days before the end of lactation varied with time around calving. The HR decreased as the proportion of Friesian genetics decreased. Compared to animals >75% Friesian the HR for animals that were <25% Friesian was 0.50 (95%CI=0.26–0.99) in the 30days before calving, 0.81 (95%CI=0.60–1.08) in the 20days after calving and 0.28 (95%CI=0.18–0.62) from 21 to 90days after calving. HR increased with age, with the largest effect seen 21–90days after calving. Compared to cows <4 years of age, cows that were 4–8 years of age had a HR of 2.18 (95%CI=1.71–2.76) and those >8 years old had a HR of 4.09 (95%CI=3.06–5.46) for this period. Dry periods >112days had a HR of 1.46 (95%CI=1.24–1.73) in the 20days after calving but a decreased HR (0.73, 95%CI=0.57–0.94) 21–90days after calving. Cows with ISCC >150,000 cells/ml 30–60days before the end of lactation had a HR of 1.60, (95%CI=1.39–1.84) 0–20days after calving and 1.96 (95%CI=1.67–2.27) 21–90days after calving. Neither number of animals calving per day, nor herd size was associated with an increased hazard of CM and there was a significant difference in the hazard across farms.

Effects of dry period length and dietary energy source on milk yield, energy balance, and metabolic status of dairy cows over 2 consecutive years: Effects in the second year

The objective of the current study was to evaluate the effect of dry period (DP) length on milk yield, energy balance (EB), and metabolic status in cows fed a lipogenic or glucogenic diet in the second year after implementation of DP and dietary treatments. Holstein-Friesian dairy cows (n=167) were assigned randomly to 1 of 3 DP lengths (0, 30, or 60d) and 1 of 2 early lactation diets (glucogenic or lipogenic) for 2 consecutive years. Results of the first year were reported previously. In the second year, 19 cows in the 0-d DP group were attributed to a new group (0→67d DP) because these cows had a milk yield of <4kg/d at least 30d before expected calving date and were dried off. Milk yield was recorded and EB was calculated from wk –8 to 9 relative to calving. Blood samples were taken weekly from wk –3 to 8 relative to calving. Liver samples were taken in wk –2, 2, and 4 relative to calving. At the onset of lactation, cows with a 0-d or 0→67-d DP had greater body condition score (BCS) than cows with a 60-d DP. During the first 9wk, cows with a 0- or 30-d DP produced 5.0 and 4.3kg less milk per day, respectively, but had similar EB compared with cows with a 60-d DP. Cows with a 0- or 30-d DP produced additional milk precalving, which could compensate milk yield losses in the first 9wk postcalving. Cows with a 0-d DP did not have milk yield losses or improve EB in the second year as much as in the first year. Cows with a 0-d DP had greater plasma insulin and insulin-like growth factor-I (IGF-I) and lower liver triacylglycerol concentrations than cows with other DP lengths. Cows with a 0→67-d DP had lower EB, and greater plasma free fatty acids (FFA) and β-hydroxybutyrate (BHB) concentrations than cows with other DP lengths. Feeding a glucogenic diet increased plasma glucose, IGF-I, and insulin concentrations, and decreased plasma FFA, BHB, and urea concentrations compared with a lipogenic diet, independent of DP length. In conclusion, omitting the DP or feeding a glucogenic diet improved metabolic status in early lactation of the second year after implementation of DP length and dietary treatments, although effects of omitting the DP were less pronounced in the second year than in the first year. The less pronounced improvement of EB in the second year was related to the high BCS at the onset of lactation and reduced milk yield losses in cows with a 0-d DP.

The effects of dry period length and dietary energy source on natural antibody titers and mammary health in dairy cows

In earlier studies, natural antibodies (NAb) were related not only to the energy balance (EB) of dairy cows, but also to somatic cell count (SCC) and clinical mastitis (CM). The first objective of our study was to evaluate the effects of dry period length and dietary energy source on titers of NAb binding keyhole limpet hemocyanin (KLH) and lipopolysaccharide (LPS) in plasma and milk, SCC and CM occurrence in dairy cows in two subsequent lactations. Our second objective was to study the relationship between NAb levels and mammary health. Holstein-Friesian dairy cows (N=167) were randomly assigned to three dry period lengths (0, 30 or 60-d) and two early lactation rations (glucogenic or lipogenic). Treatments were repeated during two subsequent lactations (years 1 and 2). In year 2, 19 cows which were planned to have 0-d dry period dried off naturally and were assigned to an additional group 0→30-d dry period. In year 1, cows with a 0-d dry period had a higher SCC, a higher titer of immunoglobulin G (IgG) binding LPS in plasma, and higher titers of IgG and IgM binding KLH and LPS in milk compared with cows with a 30-d or 60-d dry period. In year 2, cows with a 60-d dry period had a lower SCC than cows with a 30-d and 0→30-d dry periods. In year 2, dry period length did not affect NAb titers in plasma or milk. The CM occurrence was 17 percent in year 1 of the experiment and 25 percent in year 2, and did not differ according to dry period lengths or rations. For both years, an increasing titer of IgG binding LPS in plasma was associated with decreased odds of a high SCC and decreased odds of CM occurrence. Also up to three weeks before the CM occurrence, an increasing titer of IgM binding KLH and LPS in plasma was associated with a decreased odds of CM occurrence. In conclusion, omitting the dry period increased SCC, NAb titers in milk and IgG binding LPS in plasma compared with a short (30-d) or conventional (60-d) dry period. The effects on NAb titers, however, were only present in the first year after omitting the dry period and disappeared after repeated omitting the dry period. Moreover, an increasing titer of IgG binding LPS in plasma was associated with decreased odds of high SCC and CM occurrence.

Effective lactation yield: A measure to compare milk yield between cows with different dry period lengths

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

IgG1 variations in the colostrum of Holstein dairy cows

High-immune quality colostrum (IgG1 concentration ⩾50 g/l) is crucial for the health and development of the young calf. Studies on colostrum quality tend to focus on external factors such as breed, parity or dry period length, but few have focused on within-cow variations. Here we ran experiments to gain a deeper insight into within-cow variation in IgG1 concentrations in dairy cow colostrum. Trials were performed in an experimental farm, located in the Western part of France. Colostrum from each quarter and a composite sample (mix of four quarters) were concomitantly collected on 77 Holstein dairy cows just after calving to assess the influence of sample type on IgG1 concentrations. Variation in IgG1 concentrations during the first milking was studied on samples from nine cows collected every minute from the start of milking. Repeatability of colostral IgG1 concentration was estimated from 2009 and 2010 data on 16 healthy cows. IgG1 concentrations were tested using a radial immunodiffusion method. Sensitivity and specificity were similar regardless of sample type tested (individual quarter or composite milk). Mean average IgG1 concentration was 54.1 g/l in composite colostrum, and was significantly higher in hind quarter teats (56.2 g/l) than front quarter teats (53.1 g/l). Average IgG1 concentration did not change significantly during colostrum milking, and the variations observed (15% or less) were likely due to the laboratory method (CV 15%). IgG1 concentrations in dam colostrum increased slightly from 2009 to 2010 due to BW and parity effects. In 56% of cases, colostrum quality could have been assessed on either individual or composite colostrum samples collected at any time during the first milking without affecting the reliability of the measurement. However, in other cases, differences were significant enough to mean that estimates of average IgG1 concentration in colostrum from any one quarter would not be reliable. It is concluded that colostrum quality, from an IgG1 concentration point of view, could be assessed with a composite sample taken at any time during the first milking.

Effect of calving interval and parity on milk yield per feeding day in Danish commercial dairy herds

The idea of managing cows for extended lactations rather than lactations of the traditional length of 1 yr primarily arose from observations of increasing problems with infertility and cows being dried off with high milk yields. However, it is vital for the success of extended lactation practices that cows are able to maintain milk yield per feeding day when the length of the calving interval (CInt) is increased. Milk yield per feeding day is defined as the cumulated lactation milk yield divided by the sum of days between 2 consecutive calvings. The main objective of this study was to investigate the milk production of cows managed for lactations of different lengths, and the primary aim was to investigate the relationship between CInt, parity, and milk yield. Five measurements of milk yield were used: energy-corrected milk (ECM) yield per feeding day, ECM yield per lactating day, cumulative ECM yield during the first 305d of lactation, as well as ECM yield per day during early and late lactation. The analyses were based on a total of 1,379 completed lactations from cows calving between January 2007 and May 2013 in 4 Danish commercial dairy herds managed for extended lactation for several years. Herd-average CInt length ranged from 414 to 521d. The herds had Holstein, Jersey, or crosses between Holstein, Jersey, and Red Danish cows with average milk yields ranging from 7,644 to 11,286kg of ECM per cow per year. A significant effect of the CInt was noted on all 5 measurements of milk yield, and this effect interacted with parity for ECM per feeding day, ECM per lactating day and ECM per day during late lactation. The results showed that cows were at least able to produce equivalent ECM per feeding day with increasing CInt, and that first- and second-parity cows maintained ECM per lactating day. Cows with a CInt between 17 and 19mo produced 476kg of ECM more during the first 305d compared with cows with a CInt of less than 13mo. Furthermore, early-lactation ECM yield was greater for all cows and late-lactation ECM yield was less for second-parity and older cows when undergoing an extended compared with a shorter lactation. Increasing CInt increased the dry period length with 3 to 5d. In conclusion, the group of cows with longer CInt were able to produce at least equivalent amounts of ECM per feeding day when the CInt was up to 17 to 19mo on these 4 commercial dairy farms.

Effect of the interval between calving and colostrum harvest on colostrum quality in dairy cows on a New York dairy

Colostrum management is one of the key factors in successful calf management. The estimated prevalence of failure of passive transfer in dairy heifer calves is still surprisingly high at 19.2%. In a recent study by Morrill and others, 30% of nationwide collected colostrum samples from dairy farms had immunoglobulin G (IgG) concentrations less than the industry-recommended 50 g/L. In recent years, an increasing amount of research in dairy cattle has focused on factors affecting colostrum quality including breed, age of dam, season of calving, volume of colostrum, and dry period length, whereas the effect of the interval between calving and first milking has only been addressed in a limited number of studies with small data sets. The objective of this study was to investigate the influence of the interval between calving and first milking on the colostrum quality.

Relationship between metabolism and ovarian activity in dairy cows with different dry period lengths

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

Optimal Sizing of Rainwater Harvesting Tanks for Domestic Use in Greece

Rainwater harvesting gains more and more ground as a modern, relatively inexpensive and simple water-saving technology, and as a sustainable water management practice, which saves water, and reduces stormwater runoff and peaks and non-point source pollution. In this paper, in order to determine the optimal size of rainwater harvesting tanks, two methods, the daily water balance method and the dry period demand method, are used in 75 regions of Greece to meet 30, 40 and 50 % of total water demands of households of 3 to 5 residents. The daily water balance method was developed based on a heuristic algorithm which uses the daily rainfall data, the rainfall collection area, the runoff coefficient, the available storage volume and the water demands, allowing excess water to overflow and setting public water supply to zero. The dry period demand method is based on meeting demand for the longest annual average dry period. According to the daily water balance method, in the majority of the 75 regions studied, tank sizes up to 50 m3 can meet a 240 L/day demand (40 % of total daily demand of 4 residents) with roof area not exceeding 300 m2. More than 50 m3 tank size is needed to meet demands of 300 L/day (40 % of 5 or 50 % of 4 residents) or 375 L/day (50 % of 5 residents). Results demonstrate that the tank size is strongly affected by the dry period length; small dry periods lead to small tanks, with the exception of low rainfall-high demand (300–375 L/day) case, where low rainfall increases sizes, having the dominant role. Comparison among the dry period demand and the daily water balance methods showed that in all cases, the dry period demand method calculates smaller tanks, with the exception of areas with medium-high rainfall and high dry period or low-medium demand (135–225 L/day) and high roof areas (more than 300 m2). Therefore, the main conclusion is that the rainwater harvesting tank capacity is strongly affected by various local variables and cannot be formulated. However, the method presented here can be programmed in a spreadsheet with no much effort, making harvesting tank computations easy.

Ketonemia in dairy goats: Effect of dry period length and effect on lying behavior

In dairy animals, a successful transition from one lactation to the next includes minimizing negative energy balance. Cows experiencing excessive negative energy balance typically develop metabolic complications following parturition (e.g., ketosis); does are also susceptible before kidding (e.g., pregnancy toxemia). It is not known to what extent the provision and the length of the dry period affect these conditions in does. Furthermore, whereas clinical symptoms of these conditions include lethargy, behavioral changes resulting from ketosis and pregnancy toxemia have not been quantified in small ruminants. The aims of this study were to (1) describe the relationship between the dry period and negative energy balance, and (2) determine if lying behavior changes are indicative of the metabolic status of dairy goats. A total of 420 does on 10 commercial dairy goat farms in southern Ontario, Canada, were enrolled in the study (mean ± SD: 42±18 does/farm). Each doe was affixed with a data logger to measure lying behavior from 12 d before to 12 d after kidding. Blood samples were collected at least once before and at least once following kidding to determine blood β-hydroxybutyrate (BHBA) concentration as an indicator of negative energy balance. Does were categorized as healthy (HLTH; both pre- and postkidding samples BHBA <0.9 mmol/L), PREGTOX (prekidding BHBA ≥1.7 mmol/L), or KET (postkidding BHBA ≥1.7 mmol/L). Behaviors were analyzed according to 5 periods: P−2 (d −12 to d −2 relative to kidding), P−1 (d −1 relative to kidding), P0 (d 0, kidding day), P1 (d 1 relative to kidding), and P2 (d 2 to 12 relative to kidding). Dry period length and milk production after kidding were recorded when available. Farms ranged from 0 to 15% and 0 to 50% in prekidding and postkidding ketonemia, respectively. The HLTH does had shorter dry periods compared with PREGTOX and KET does (43 vs. 55 d, SE of the differences of means=4 d). One farm kept some does milking, while drying off others; on this farm more PREGTOX and KET does (11/28) were found in the dry group versus the continuously milked group (1/16). Overall, does that had ketonemia before kidding (PREGTOX) spent more time lying down compared with healthy does (16.1 vs. 12.7 h/d, SE of the differences of means=0.9). Both PREGTOX and HLTH does had increased lying bouts in P−2 compared with the day before (P−1) kidding [(mean (95% CI): 16.8 (15.8–17.8) vs. 20.5 (19.4–21.8) bout/d]. Compared with HLTH does, animals that were ketonemic following kidding (KET) had higher mean lying times throughout the study (14.5 vs. 13.5 h/d, SE=0.4). Previous work has shown a relationship between shorter and skipped dry periods and improved energy balance in dairy cows; the current study is the first to indicate a similar relationship in dairy goats. Furthermore, goats that developed ketonemia, particularly before kidding, displayed decreased activity, including longer lying times and fewer lying bouts in the days around kidding.

Runoff-erosion modeling at micro-watershed scale: a comparison of self-organizing maps structures

In the last decades, everal runoff-erosion models have been proposed to estimate soil erosion, which may lead to loss of fertile land and increase sedimentation and pollution in water bodies. Physically-based erosion models are usually used for such purpose, but a major problem concerning their use is the difficulty to directly measure parameters in the field. This problem can be overcome by exploring empirical models, such as so-called Self-Organizing Maps (SOM). An SOM is a type of Artificial Neural Network (ANN) based on a competitive learning approach for clustering and modeling a variety of databases. Since studies on soil erosion modeling based on SOM are very incipient, we compared some structures of SOM with the purpose of estimating sediment yield based on runoff and climatological data at the micro-watershed scale. The case study was a micro-watershed within the Sumé Experimental Basin, which is located in a semiarid region of Brazil. Different from the conventional ANN, SOM-based models represent a multidimensional data set by means of a bidimensional matrix of features, which may be applied for analysis and estimation purposes. In order to calibrate and validate the proposed SOM structures, we used data from 117 rainfall events that occurred between 1985 and 1991. Analyses of the results indicate that all SOM structures were efficiently calibrated with NASH coefficients (Nash & Sutcliffe 1970) varying from 0.88 to 0.90. The SOM structure with 6 × 8 neurons was the most effective for estimating sediment yields when considering the validation data set (NASH = 0.73). The generated maps showed that sediment yields were directly related to runoff and rainfall intensity and inversely correlated to average vegetation heights. The dry period length did not seem to influence the production of sediments. SOM were shown to be very practical and meant to be applied to specific locations. This type of methodology also demands long term data and dynamic recalibration with up-to-date information in order to account for changes in the watershed.

EFSA's assistance for the 2015 Codex Committee on Residues of Veterinary Drugs in Food (CCRVDF) in relation to rBST

EFSA's assistance for the 2015 Codex Committee on Residues of Veterinary Drugs in Food (CCRVDF) in relation to rBST

Using variograms to detect and attribute hydrological change

Abstract. There have been many published studies aiming to identify temporal changes in river flow time series, most of which use monotonic trend tests such as the Mann–Kendall test. Although robust to both the distribution of the data and incomplete records, these tests have important limitations and provide no information as to whether a change in variability mirrors a change in magnitude. This study develops a new method for detecting periods of change in a river flow time series, using temporally shifting variograms (TSVs) based on applying variograms to moving windows in a time series and comparing these to the long-term average variogram, which characterises the temporal dependence structure in the river flow time series. Variogram properties in each moving window can also be related to potential meteorological drivers. The method is applied to 91 UK catchments which were chosen to have minimal anthropogenic influences and good quality data between 1980 and 2012 inclusive. Each of the four variogram parameters (range, sill and two measures of semi-variance) characterise different aspects of the river flow regime, and have a different relationship with the precipitation characteristics. Three variogram parameters (the sill and the two measures of semi-variance) are related to variability (either day-to-day or over the time series) and have the largest correlations with indicators describing the magnitude and variability of precipitation. The fourth (the range) is dependent on the relationship between the river flow on successive days and is most correlated with the length of wet and dry periods. Two prominent periods of change were identified: 1995–2001 and 2004–2012. The first period of change is attributed to an increase in the magnitude of rainfall whilst the second period is attributed to an increase in variability of the rainfall. The study demonstrates that variograms have considerable potential for application in the detection and attribution of temporal variability and change in hydrological systems.

Methodologies for pre-validation of biofilters and wetlands for stormwater treatment.

BackgroundWater Sensitive Urban Design (WSUD) systems are frequently used as part of a stormwater harvesting treatment trains (e.g. biofilters (bio-retentions and rain-gardens) and wetlands). However, validation frameworks for such systems do not exist, limiting their adoption for end-uses such as drinking water. The first stage in the validation framework is pre-validation, which prepares information for further validation monitoring.ObjectivesA pre-validation roadmap, consisting of five steps, is suggested in this paper. Detailed methods for investigating target micropollutants in stormwater, and determining challenge conditions for biofilters and wetlands, are provided.MethodsA literature review was undertaken to identify and quantify micropollutants in stormwater. MUSIC V5.1 was utilized to simulate the behaviour of the systems based on 30-year rainfall data in three distinct climate zones; outputs were evaluated to identify the threshold of operational variables, including length of dry periods (LDPs) and volume of water treated per event.ResultsThe paper highlights that a number of micropollutants were found in stormwater at levels above various worldwide drinking water guidelines (eight pesticides, benzene, benzo(a)pyrene, pentachlorophenol, di-(2-ethylhexyl)-phthalate and a total of polychlorinated biphenyls). The 95th percentile LDPs was exponentially related to system design area while the 5th percentile length of dry periods remained within short durations (i.e. 2–8 hours). 95th percentile volume of water treated per event was exponentially related to system design area as a percentage of an impervious catchment area.ConclusionsThe out-comings of this study show that pre-validation could be completed through a roadmap consisting of a series of steps; this will help in the validation of stormwater treatment systems.

Particle size distribution and characteristics of heavy metals in road-deposited sediments from Beijing Olympic Park

Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments (RDSs) of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents' and tourists' health. To identify the distribution and characteristic of heavy metals in RDS and to assess the road environmental quality in Chinese parks, samples were collected from Beijing Olympic Park in the present study. The results indicated that particles with small grain size (<150μm) were the dominant fraction. The length of dry period was one of the main factors affecting the particle size distribution, as indicated by the variation of size fraction with the increase of dry days. The amount of heavy metal (i.e., Cu, Zn, Pb and Cd) content was the largest in particles with small size (<150μm) among all samples. Specifically, the percentage of Cu, Zn, Pb and Cd in these particles was 74.7%, 55.5%, 56.6% and 71.3%, respectively. Heavy metals adsorbed in sediments may mainly be contributed by road traffic emissions. The contamination levels of Pb and Cd were higher than Cu and Zn on the basis of the mean heavy metal contents. Specifically, the geoaccumulation index (Igeo) decreased in the order: Cd>Pb>Cu>Zn. This study analyzed the mobility of heavy metals in sediments using partial sequential extraction with the Tessier procedure. The results revealed that the apparent mobility and potential metal bioavailability of heavy metals in the sediments, based on the exchangeable and carbonate fractions, decreased in the order: Cd>Zn≈Pb>Cu.

Effect of maternal dry period length on colostrum immunoglobulin content and on natural and specific antibody titers in calves

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

A survey of drying-off practices on commercial dairy farms in northern Germany and a comparison to science-based recommendations

While dry cow management is important for health, milk production and fertility information on drying-off procedures implemented on commercial dairy farms is lacking. Current drying-off management procedures on commercial dairy...

Milk production of dairy cows as affected by the length of the preceding dry period

The objective of the study was to determine the effect of the duration of the dry period (DP) on the milk yield and milk composition during the following lactation. Milk performance records of 561 Holstein cows, with a previous DP from the Elsenburg Research Farm obtained from the National Milk Recording Scheme, were used in the study. Four groups of dairy cows were identified, based on the duration of their dry period, i.e. cows with a DP of less than 60 days, DP of 61 to 90 days, DP of 91 to 120 days and DP of more than 121 days. The number of records for each group was 76, 162, 83 and 240 lactations, respectively. An ANOVA was conducted using the Generalized Linear Model of SAS to compare milk yield and milk composition according to the DP length. Almost 43% of cows had a DP longer than 121 days, while less than 14% of cows had a DP of less than 60 days. The milk yield was positively affected by DP length. Cows with a DP of less than 60 days produced less milk than cows with longer (more than 61 days) dry periods, e.g. 6462 ± 321 vs. 7393 ± 99 kg. Results were similar for cows in their second and fourth parity. In addition, the milk composition of cows was also affected by DP length, i.e. higher fat and protein levels in the milk from cows with a short DP. Cows in the third lactation with a DP above 121 days produced more milk than the other DP groups. However, the milk composition of cows in the third lactation was not affected by DP length. A DP of less than 60 days reduced milk yield, while an extended DP of more than 121 days would be costly for the dairy farmer even though milk yield was higher. A long dry period may also result due to an excess body condition and calving complications during the subsequent lactation.Keywords: Dry period, milk yield, milk composition, dairy cows

Dry Period Length as Related to Milk Yield and SCC During the First Month of Subsequent Lactation

Abstract Analysis was made of the effect of dry period length in primiparous and multiparous cows on daily milk yield during the first month of subsequent lactation and on milk somatic cell count (SCC) on the basis of the information about the test-day milkings of 59 138 cows. The GLM and FREQ procedures of the SAS package were used in the statistical calculations. Dry period length in the primiparous and multiparous cows had a significant effect (P≤0.01) on daily milk yield and udder health, determined based on SCC. In terms of milk yield, the most favourable dry period would be 51-70 days for both primiparous and multiparous cows. Depending on udder health, a dry period of 51-90 days can be suggested. Shorter dry periods had more undesirable effects than longer dry periods. Excessively shortened dry period (≤10 days) caused the daily milk yield to decrease by 17% in primiparous and by 13% in multiparous cows while increasing the risk of clinical changes of the cow’s udder, regardless of age. The proportion of milk samples that showed evidence of clinical mastitis also increased when the dry period was excessively long (&gt;90 days), especially in multiparous cows.

Environmental factors and dam characteristics associated with insulin sensitivity and insulin secretion in newborn Holstein calves

The objective of the present retrospective cohort study was to evaluate potential associations between environmental factors and dam characteristics, including level of milk production during gestation, and insulin traits in newborn Holstein calves. Birth weight and gestational age of the calves at delivery were determined. On the next day, heart girth, wither height and diagonal length of both the calves and their dams were measured. Parity, body condition score and age at calving were recorded for all dams. For the cows, days open before last gestation, lactation length (LL), length of dry period (DP) and calving interval were also calculated. The magnitude and shape of the lactation curve both quantified using the MilkBot model based on monthly milk weights, were used to calculate the amount of milk produced during gestation. Using the same procedure, cumulative milk production from conception to drying off (MGEST) was calculated. A blood sample was collected from all calves (n=481; 169 born to heifers and 312 born to cows) at least 5 h after a milk meal on day 3 of life to measure basal glucose and insulin levels. In addition, an intravenous glucose-stimulated insulin secretion test was performed in a subset of the calves (n=316). After descriptive analysis, generalized linear mixed models were used to identify factors that were significantly associated with the major insulin traits (Insb, basal insulin level; QUICKI, quantitative insulin sensitivity check index; AIR, acute insulin response; DI, disposition index) of the newborn calves. The overall average birth weight of the calves was 42.7±5.92 kg. The insulin traits were significantly associated with gender and season of birth when data of all calves were analyzed. In addition, the insulin traits in calves born to cows were significantly associated with MGEST, DP and LL. The Insb was estimated to be higher in calves born to the cows having passed a higher MGEST (P=0.076) and longer DP (P=0.034). The QUICKI was estimated to be lower in calves born to the cows having passed a higher MGEST (P=0.030) and longer DP (P=0.058). Moreover, the AIR (P=0.009) and DI (P=0.049) were estimated to be lower in male compared with female calves. Furthermore, the AIR (P=0.036) and DI (P=0.039) were estimated to be lower in calves born to cows having passed a longer LL. The decisive effects of MGEST, DP and LL in cows on the insulin traits of their calves may provide a basis for developing managerial interventions to improve metabolic health of the offspring.