Average Milk Flow Rate Research Articles

Evaluation of the performance of the first automatic milking system for buffaloes

The objective of this study was to evaluate the response of buffaloes to automatic milking, examining the relationships between milking interval, milk production, and milking time for this species. A total of 7,550 milking records from an average of 40 buffaloes milked by an automatic milking system (AMS) were analyzed during a 3-mo experimental period at a commercial farm with Italian Mediterranean buffaloes in southern Italy. Date and time of animal identification, milk yield, milking duration, milking interval, and average milk flow rate were determined for each milking. The results were also used to predict the maximum number of milkings per day and the optimal number of buffaloes per AMS for different levels of milk production. The average interval period between 2 consecutive milkings was 10.3 h [standard deviation (SD) 3.3]. Overall, 3.4 and 25.7% of the milkings had an interval of ≤6 h or >12 h, respectively. Milking duration averaged 8.3 min per buffalo per milking (SD 2.7). The average milk flow rate was 1.3kg/min (SD 0.5) at a milk yield of 2.8kg per milking (SD 1.4). Assuming that the milking station is occupied 80% of the time, the number of milkings ranged from 136 to 152 per day and the optimal number of buffaloes per AMS ranged from 59 to 66 when the production level increased from 2 to 5kg of milk per milking. Automatic milking systems are suitable for buffalo, opening new options for the management of dairy buffalo farms.

The relationship between responsiveness of first-lactation heifers to humans and the behavioral response to milking and milk production measures

The human–animal relationship can influence how an animal responds to situations involving humans and affect animal well-being and production. The objectives of this research were to (1) determine if there is a relationship between the behavioral reactivity of New Zealand dairy heifers toward humans and the behavioral response to cluster placement during milking and milk production measures and (2) determine if this relationship changes as heifers become habituated to the milking process. A total of 150 primiparous heifers were randomly selected from 3 commercial dairy farms. Approximately 1 month before calving, 2 behavioral tests, avoidance distance in response to an approaching human and exit speed from a restraint, were performed on 50 heifers at each farm. For each heifer, behavioral observations were recorded during the morning milking period (during the first and sixth weeks of lactation). Behaviors recorded during cluster placement at milking included flinching, stepping, and/or kicking (FSK). Milk yields, milking durations, and average milk flow rates were recorded for each individual heifer during the first and sixth weeks of lactation. Avoidance distance and exit speed were positively correlated (P 0.05) between avoidance distance and FSK. Avoidance distance was positively (P 0.05) between exit speed and milk yields, durations, or flow rates. Furthermore, the FSK response was negatively (P < 0.05) correlated with milk yield during weeks 1 and 6 of lactation. Therefore, the behavioral response of heifers toward humans and the milking process appears to be related to milk production measures.

Analysis of milking characteristics in New Zealand dairy cows

The objective of this study was to describe the variation in milking characteristics, and factors associated with these traits, in grazing dairy cows milked without premilking stimulation. Milk yield, duration, and average and maximum milk flow rate data were collected from 38 farms in New Zealand at 2 time points (spring and autumn) during the 2010 to 2011 season. Subsequently, a second data set, allowing the generation of daily milk flow profiles, was collected from 2 farms in the 2011 to 2012 season. Corresponding animal data, such as breed, date of birth, and ancestry information, were extracted from the New Zealand Dairy Industry Good Animal Database (New Zealand Animal Evaluation Ltd., Hamilton, New Zealand). Residual milking duration (deviation from the regression line of milk yield on milking duration) was calculated, allowing the identification of fast-milking cows independent of milk yield. Variance components for the milking characteristics traits were estimated using an animal linear mixed model. The average milk yield was 10kg/milking and the average milking duration was 360s. The average milk flow rate was 1.8kg/min and maximum milk flow 3.3kg/min, with 44% of milk flow curves being classified as bimodal. Primiparous animals exhibited different milk flow profiles, with a lower maximum flow, than multiparous animals, possibly due to differences in cisternal capacity. Residual milking duration was shortest (−10s) in mid-lactation (121–180d) and was 13s longer for Jersey compared with Friesian cows; however, it was 19s shorter when adjusted for energy content. Residual milking duration had a negligible genetic correlation (−0.07) with milk yield, indicating that selection for cows with shorter residual milking duration should have a negligible effect on milk yield. A heritability of 0.27 indicated that residual milking duration could be valuable as part of a breeding program. Knowledge of the distribution of milking durations for a given milk yield allows farmers to choose appropriate cluster-on time when using a maximum milking time strategy to improve milking efficiency.

Milking efficiency of swingover herringbone parlours in pasture-based dairy systems

The objective of this study was to collect and analyse milking data from a sample of commercial farms with swingover herringbone parlours to evaluate milking efficiency over a range of parlour sizes (12-32 milking units). Data were collected from 19 farms around the Republic of Ireland equipped with electronic milk metres and herd management software that recorded data at individual milking sessions. The herd management software on each farm was programmed to record similar data for each milking plant type. Variables recorded included cow identification, milking date, identification time, cluster-attachment time, cluster/unit number, milk yield, milking duration, and average milk flow rate. Calculations were performed to identify efficiency benchmarks such as cow throughput (cows milked per h), milk harvesting efficiency (kg of milk harvested per h) and operator efficiency (cows milked per operator per h). Additionally, the work routine was investigated and used to explain differences in the benchmark values. Data were analysed using a linear mixed model that included the fixed effects of season-session (e.g. spring-AM), parlour size and their interaction, and the random effect of farm. Additionally, a mathematical model was developed to illustrate the potential efficiency gains that could be achieved by implementing a maximum milking time (i.e. removing the clusters at a pre-set time regardless of whether the cow had finished milking or not). Cow throughput and milk harvesting efficiency increased with increasing parlour size (12 to 32 units), with throughput ranging from 42 to 129 cows/h and milk harvesting efficiency from 497 to 1430kg/h (1-2 operators). Greater throughput in larger parlours was associated with a decrease in operator idle time. Operator efficiency was variable across farms and probably dependent on milking routines in use. Both of these require consideration when sizing parlours so high levels of operator efficiency as well as cow throughput can be achieved simultaneously. The mathematical model indicated that application of a maximum milking time within the milking process could improve cow throughput (66% increase in an 18-unit parlour when truncating the milking time of 20% of cows). This could allow current herd milking durations to be maintained as herd size increases.

Factors associated with milking characteristics in dairy cows

Milking characteristics, and in particular milking duration, are a known contributor to costs in dairy production systems. Results from previous studies suggest that higher-yielding animals, on average, milk for a longer duration. Culling or selection for reduced milking duration alone may, therefore, reduce milk yield. Here, we propose 2 new traits, residual milking duration (RMD) and residual milking duration including somatic cell score (RMDS). Residual milking duration is represented by the residuals from a least squares regression of milking duration on milk yield; RMDS is represented by the residuals from a least squares regression of milking duration on both milk yield and somatic cell score [i.e., logarithm (base 10) of somatic cell count]. The mathematical properties of least squares regression ensure than the residual traits are independent from the regressor variables, or, in other words, RMDS is not correlated with either milk yield or somatic cell score. Both RMD and RMDS were defined using electronically measured individual cow milking duration from 235,036 part-day milking events from 74,607 cows from 1,075 Irish dairy herds. Twenty-four percent of the variation in milking duration was explained by the multiple regression model containing both milk yield and somatic cell score. The phenotypic standard deviation of RMD and RMDS was 102.2 and 98.2s, respectively, suggesting large variation in milking duration independent of milk yield (and somatic cell score). The correlation of RMD and RMDS with average milk flow rate, which may also be considered a measure of milking efficiency, was −0.74 and −0.75, respectively. Neither RMD nor RMDS was correlated with somatic cell score. However, average milk flow rate was correlated with milk yield (0.57) and milking duration (−0.38). Both RMD and RMDS are useful traits, which exhibit considerable variation and, therefore, can be used by farmers to identify phenotypically slower milking animals irrespective of milk yield (and somatic cell score). However, because of the lack of a correlation between RMD and somatic cell score in the sample population used in the present study, RMD and RMDS values per milking were almost identical.

Milking efficiency for grazing dairy cows can be improved by increasing automatic cluster remover thresholds without applying premilking stimulation

It was hypothesized that streamlined premilking stimulation routines are effective at reducing cow cluster-on time but are not required to maintain milk yield or quality when increasing the automatic cluster remover (ACR) threshold above 0.4kg/min. This was tested by examining the effect of 3 premilking treatments and 4 ACR thresholds over an 11-wk period with 96 mixed-age New Zealand Friesian-Jersey cross cows during peak lactation. Three premilking treatments were chosen: attach cluster immediately (control), attach cluster immediately and apply 30s of mechanical stimulation (Stim), and remove 2 squirts of milk from each quarter and attach cluster (Strip). Four ACR milk flow rate thresholds were imposed: 0.2kg/min (ACR2), 0.4kg/min (ACR4), 0.6kg/min (ACR6), and 0.8kg/min (ACR8). Measurements included individual cow milk yield, cluster-on time, average milk flow rate, maximum milk flow rate, time to average milk flow rate, time from maximum milk flow rate to end of milking, and the milk flow rate and cumulative yield at predetermined intervals during each milking session. Milk composition and somatic cell count (SCC) were determined on composite milk samples, collected weekly. Postmilking strip yield was measured at the end of each treatment period. Cows receiving the Strip treatment had a 3 to 4% shorter cluster-on time than did cows on the control treatment, but cows receiving Stim were not different from the control cows. Milk yield, SCC, and postmilking strip yield were not different between the 3 premilking treatments. Cluster-on time of the ACR8 cows was 18 to 26% less than that of the ACR2 cows, but SCC and milk production variables did not differ between the 4 end-of-milking treatments, despite higher strip yields as the ACR threshold increased. Increasing the ACR threshold is an effective strategy to improve milking efficiency (cows milked per operator per hour) in situations where the work routine times of dairy operators can be accelerated. To achieve the greatest milking efficiency, clusters should be attached immediately without premilking manual or mechanical stimulation.

Short-term application of prestimulation and increased automatic cluster remover threshold affect milking characteristics of grazing dairy cows in late lactation

It was hypothesized that reducing cow cluster-on time by increasing automatic cluster remover (ACR) thresholds above 0.4kg/min would require premilking stimulation of the mammary gland to maintain milk yield. This was tested by examining the interaction between 4 ACR thresholds and 3 premilking treatments over an 8-wk period with 96 mixed-age Friesian-Jersey cross cows being milked twice per day in late lactation (average production: 13.9kg/d). The 3 premilking treatments were attach cluster immediately (control), attach cluster 60s after entering the dairy (delay), or remove 2 squirts of foremilk from each quarter and attach cluster 60s after entering the dairy (Prep). Four ACR thresholds were chosen, where the cluster was removed after the milk flow rate was less than 0.2 (ACR2), 0.4 (ACR4), 0.6 (ACR6), and 0.8kg/min (ACR8). Measurements included individual cow milk yield, cluster-on time, average milk flow rate, maximum milk flow rate, time from cluster attachment to average milk flow rate, milk yield in the first 2min, time from maximum milk flow rate to end of milking, and the milk flow rate at predetermined intervals during each milking session. Composite milk samples were collected weekly at a.m. and p.m. milkings to determine composition and somatic cell count (SCC). On 3 occasions during the experiment, postmilking strip yield was measured. No interactions were detected between premilking treatment and ACR threshold in any of the measured variables. Cows receiving the Prep treatment had a 5 to 9% shorter cluster-on time than the control treatment. Milk yield, SCC, postmilking strip yield, and maximum flow rate were not different between the 3 premilking treatments. Cluster-on time of the ACR8 cows was 21 to 29% less than ACR2, but SCC and milk production variables were not different between the 4 end-of-milking treatments despite higher strip yields as ACR threshold increased. Increasing ACR threshold offers the potential to reduce the duration of milking without detriment to overall productivity. The results of the premilking treatments indicate that to achieve the most efficient routine, the operator should attach clusters as close as possible to the first bail in rotary dairies to increase bail utilization in pasture-based systems. If cluster attachment can be sped up and ACR threshold lifted, significant potential exists to decrease herd milking duration and improve labor productivity.

Large rotary dairies achieve high cow throughput but are not more labour efficient than medium-sized rotaries

It was hypothesised that large rotary dairies (&gt;60 clusters) are not more operator efficient than medium-sized rotaries (40–60 clusters). This was tested by collecting and analysing milking data, during peak and late lactation, from block calving herds milked in rotary dairies fitted with electronic milk meters. Data were collected from a total of 61 unique farms around New Zealand, with rotary dairies ranging in size from 28 to 80 clusters, for two 5-day periods during spring (September–November 2010; 47 farms; average milk yield 23.1 kg/day) and autumn (February–April 2011; 60 farms; average milk yield 16.4 kg/day). A telephone survey was conducted to collect basic farm details: size, land area, the number of herds managed (including hospital herds), number of operators in the dairy and total labour input. A site visit was conducted to collect data such as the number of bails/stalls over the entrance and exit of the platform. The herd management software on each farm was programmed to record similar fields for each of the six machine manufacturers represented. Variables recorded included cow, date, identification time, bail number, milk yield, milking duration, and average milk flow rate. Calculations were performed to determine the number of cows milked and milk harvested per hour as well as the operator efficiency values for these measures and an estimate of cluster utilisation. Mixed models were used to determine the relationship between the dependent variables, cows milked per hour, milk harvested per hour, cows milked per operator per hour, milk harvested per operator per hour, and cluster utilisation, and the independent variables collected. Cows milked and milk harvested per hour increased linearly with rotary size, during both spring and autumn and there was a quadratic relationship between operator efficiency measures and rotary size, which peaked at ~60 clusters. Cluster utilisation, the amount of time clusters were harvesting milk out of the plant running time, was estimated at 46 ± 6%. Larger rotary dairies on average achieved greater throughput; however, they were not more operator efficient than medium-sized rotaries. Thus, large rotary dairies are best suited to farms where the additional throughput is required.

Short communication: The effect of premilking with a teat cup–like device, in a novel robotic rotary, on attachment accuracy and milk removal

This study investigated the effects of premilking teat preparation on attachment accuracy and milk removal characteristics for individual cows in a novel 16-bail prototype robotic rotary (RR; automatic milking rotary system; DeLaval AMR, Tumba, Sweden). The first commercial versions of the RR systems will have the option of purchasing and installing a teat preparation module (TPM) for premilking stimulation and cleaning of teats. It is expected that attachment of teat cups would be faster and more successful with the use of a TPM, and that the efficiency of milk removal, in terms of average and peak milk flow rates, would increase. We observed a significant effect of treatment (no wash vs. wash) and individual quarters on attachment success: cows exposed to the wash treatment had up to 1.5 times higher odds of being successfully attached. The attachment was not only more successful but was also found to be 4.3s faster after cows were exposed to the wash treatment. Average milk flow rate was not affected by the wash treatment. Nevertheless, a significant interaction was found between wash treatment and milking interval affecting the peak milk flow (kg/min) of individual cows. This interaction showed that cows with a milking interval ≤8h subjected to the wash treatment had significantly higher peak flow rates (300g/min increase) compared with cows in the same milking interval category with no wash treatment. The relationship between premilking stimulation and attachment success shown in this study will increase awareness (of both farmers and developers of the technology) of the importance of teat cleaning within the RR. The effects of the improved system performance should be taken into account (alongside the capital investment cost) when deciding to install a RR equipped (or not) with a TPM.

Estimates of marker effects for measures of milk flow in the Italian brown Swiss dairy cattle population

BackgroundMilkability is a complex trait that is characterized by milk flow traits including average milk flow rate, maximum milk flow rate and total milking time. Milkability has long been recognized as an economically important trait that can be improved through selection. By improving milkability, management costs of milking decrease through reduced labor and improved efficiency of the automatic milking system, which has been identified as an important factor affecting net profit. The objective of this study was to identify markers associated with electronically measured milk flow traits, in the Italian Brown Swiss population that could potentially improve selection based on genomic predictions.ResultsSires (n = 1351) of cows with milk flow information were genotyped for 33,074 single nucleotide polymorphism (SNP) markers distributed across 29 Bos taurus autosomes (BTA). Among the six milk flow traits collected, ascending time, time of plateau, descending time, total milking time, maximum milk flow and average milk flow, there were 6,929 (time of plateau) to 14,585 (maximum milk flow) significant SNP markers identified for each trait across all BTA. Unique regions were found for each of the 6 traits providing evidence that each individual milk flow trait offers distinct genetic information about milk flow. This study was also successful in identifying functional processes and genes associated with SNPs that influences milk flow.ConclusionsIn addition to verifying the presence of previously identified milking speed quantitative trait loci (QTL) within the Italian Brown Swiss population, this study revealed a number of genomic regions associated with milk flow traits that have never been reported as milking speed QTL. While several of these regions were not associated with a known gene or QTL, a number of regions were associated with QTL that have been formerly reported as regions associated with somatic cell count, somatic cell score and udder morphometrics. This provides further evidence of the complexity of milk flow traits and the underlying relationship it has with other economically important traits for dairy cattle. Improved understanding of the overall milking pattern will aid in identification of cows with lower management costs and improved udder health.

Milkability evaluation of Holstein dairy cows by Lactocorder

Milkability evaluation of Holstein dairy cows by LactocorderThe aim of this work was to evaluate chosen milk flow characteristics of Holstein dairy cows, using mobile electronic milk flow meters - Lactocorders. A total of 181 Holstein dairy cows were evaluated and divided according to parity, lactation stage and bimodality in order to carry out a detailed comparison of measured milkability traits. The average total milk yield was 11.98±3.41 kg per milking with an average milk flow rate of 2.52±0.75 kg min-1 and a maximum milk flow rate of 3.94±1.30 kg min-1. The total milk yield showed positive correlations with the average milk flow rate (r = 0.48; P&lt;0.001) and also with the maximum milk flow rate (r = 0.32; P&lt;0.001). More than 47% of milk flow curves were classified as bimodal. Bimodality was positively correlated with the duration of the incline phase (r = 0.73; P&lt;0.001) and negatively correlated with the quantity of milk obtained during the first minute of milking (r = -0.34; P&lt;0.001). In relation to the lactation stage - the highest average milk flow rate was reached by Holstein dairy cows at the beginning of the lactation (up to 100 days in milk), and in relation to parity - the highest milk flow rates were measured in second-lactation dairy cows.

Best combination of pre-stimulation and latency period duration before cluster attachment for efficient oxytocin release and milk ejection in cows with low to high udder-filling levels

Experiments were designed to investigate the suitability of a combination of a short manual teat stimulation with a short latency period before teat cup attachment to induce and maintain oxytocin release and milk ejection without interruption. In Experiment 1, seven dairy cows in mid lactation were manually pre-stimulated for 15, 30 or 45 s, followed by either 30 s or 45 s of latency period. It was shown that all treatments induced a similar release of oxytocin without interruption until the end of milking. In particular, the latency period of up to 45 s did not cause a transient decrease of oxytocin concentration. In Experiment 2, milking characteristics were recorded in seven cows each in early, mid, and late lactation, respectively. Because the course of milk ejection depends mainly on the degree of udder filling, individual milkings were classified based on the actual degree of udder filling which differs between lactational stages but also between morning and evening milkings. All animals underwent twelve different udder preparation treatments, i.e. 15, 30, or 45 s of pre-stimulation followed by latency periods of 0, 30, 45, or 60 s. Milking characteristics were recorded. Total milk yield, main milking time and average milk flow rate did not differ between treatments if the degree of udder filling at the start of milking was >40% of the maximum storage capacity. However, if the udder filling was <40%, main milking time was decreased with the duration of a latency period up to 45 s, independent of duration of pre-stimulation. Average milk flow at an udder filling of <40% was highest after a pre-stimulation of 45 s followed by a latency period of another 45 s. In contrast, average milk flow reached its lowest values at a pre-stimulation of 15 s without additional latency period. However, average milk flow after a 15-s pre-stimulation increased with increasing latency period. In conclusion, a very short pre-stimulation when followed by a latency period up to 45 s before teat cup attachment remains a suitable alternative for continuous stimulation to induce milk ejection.

MILKABILITY IN HOLSTEIN COWS

The aim of this work was evaluation of milkability in Holstein cows. We collected a total 63 milk flow curves, using electronic mobile milk flow meter – lactocorder. The measuring was carried out in cows from 5 to 305 days in milk. The average milk yield per milking was 15.63 kg, with average milk flow rate 2.84 kg.min-1 and average maximum milk flow rate of 4.49 kg.min-1. The average duration of incline phase was 1.09 min., duration of plateau phase was 1.82. min, and duration of decline phase was 2.26 min. Percentage of bimodal milk flow curves was 52 %, on average. The highest average milk flow rate (3.01 kg.min-1) and the highest average peak milk flow rate (4.96 kg.min-1) were found in cows in second lactation, in comparison with primiparous cows (2.87 kg.min-1, and 4.37 kg.min-1) and cows in another lactation (2.7 kg.min-1, and 4.3 kg.min-1).

Einfluss differenzierter Eutervorbereitungszeiten auf Melkbarkeitsmerkmale bei Milchkühen in Kuba

Abstract. Title of the paper: Effect of different time of pre-milking teat preparation on milking characteristics of dairy cows in Cuba For the evaluation of different times of pre-milking teat preparation on milking ability of different races/genotypes some parameters about milking with machines (milking characteristics) have been registered. This study reveals that an insufficient pre-milking teat preparation clearly under 60 s lead to a significant deterioration of the milking characteristics. The average milk flow rate decreased while the main-milking-time and the post-milking-time increased. Generally a pre-milking teat preparation of 60s was sufficient to trigger a fully adequate milk ejection. An increase of this time of pre-milking teat preparation to 300 s or even 400 s lead to negative influence on the milking characteristics.

Short Communication: Effect of Vacuum and Ratio on the Performance of a Monoblock Silicone Milking Liner

The vacuum and teat-cup chamber ratio are important operating parameters that affect milking performance by milking machines. In addition, the design and composition of materials are major elements affecting the performance characteristics of (teat-cup) milking machine liners. The objective of this experiment was to determine the effects of vacuum and teat-cup chamber ratio on the performance of a unique mono-block silicone milking machine liner that is round in the open position and triangular in the collapsed position. System vacuum settings (set at receiver) were 40.6, 43.9, and 47.3 kPa, whereas teat-cup chamber ratios were 60:40, 65:35, and 70:30. Milk yield was greatest at a vacuum of 43.9 kPa. Manual adjustments and kickoffs were very low (<2%) at all vacuum levels and for all ratios. The interaction of vacuum level and ratio was significant for milking duration, peak flow rate, and average flow rate, but not for milk yield. Average and peak milk flow rates increased at each increasing vacuum level and each wider ratio, whereas milking duration decreased.

유우의 착유 지속시간과 유속에 미치는 요인 및 산유량과의 상관관계 추정에 관한 연구

The objective of this study was to investigate the environmental effects on duration time of milk flow, peak milk flow, and average milk flow in teats, and to estimate their relationships with milk yields in morning and evening milking, and to provide fundamental information for the further study on their relationships with clinical mastitis and somatic cell in milk. A total of 6,768 milking records were studied in 72 Holstein cows. The influences of season, parity, lactation month, and milking interval on characteristics of milk flow considering in linear model were significant(p < .05). Duration of milk flow was longest at milking in fall, past first parity and second month of lactation, and with milking interval over than 13.5hrs. Average milk flow rate and peak milk flow rate were highest at milking in summer, past first parity and 8 10 months of lactation, and with milking interval over than 13.5hrs. Milk flow rate was positively correlated to milk yield, and negatively correlated to the duration of milk flow. However duration milk flow was positively correlated to the milk yield with high level of correlation coefficient(+.60). For the establishment of optimum selection criteria on these traits, other aspects such as the udder health, disease and respective economic weights of milk flow characteristics in this study must be considered to develop the indices.

Milk Flow Rate and Milking Frequency in Red Sokoto Goats

Twenty-four Red Sokoto goats were hand milked for 120 days to determine milk flow rate. The does were grouped into three for once, twice and thrice a day milking to determine the effect of milkin g frequency on milk flow rate. The average daily milk yield and milk flow rate was 466.9g and 3.5g/sec, respectively. Milking frequency significantly (P<0.01) influenced milk yield and milk flow rate. The higher the milking frequency, the higher the milk yield, but with a decreasing flow rate. Milk yield and milk flow rate were significantly (P<0.01) and positively correlated (r = 0.88). Both milk yield and flow rate reached their peak at the 4 week of production. The optimum milking frequency for Red Sokoto goat in this study was the twice th daily milking, since there was 52.7% increase in milk yield from once a day, with a marginal 7.9% reduction in milk flow rate.

MILKING PERFORMANCE OF DAIRY COWS SUBJECTED TO ELECTRICAL CURRENT AND INDUCED MILKING MACHINE PROBLEMS

Milking performance of cows subjected to electrical current during milking and two common milking machine problems were documented. The first experiment used 32 cows in a 2 U 2 factorial design with exposure to 1 mA (rms, 60 Hz) of electrical current from front to back hooves during milking and a pulsation failure (no massage phase) as treatments. A second experiment used 16 cows in a 2 U 2 factorial design with exposure to 1 mA (rms, 60 Hz) of electrical current from front to back hooves during milking and excessively aged milking machine liners as treatments. The response measures for both experiments were milk yield, average milk flow rate, maximum milk flow rate, cow activity, and strip yield. The main effect of current exposure was not statistically significant for any of the response variables. The main effect of pulsation failure was significant for cow activity (5.8 fewer weight shifts during a milking). The main effect of aged liners was significant for milk yield (2.2 kg increase), average flow rate (0.3 kg/min reduction), maximum flow rate (1.2 kg/min reduction), and liner slips (26 more per milking). The significance of some interactive effects appeared to indicate that current exposure had a mitigating effect on the changes caused by the milking machine problems. These interactions were not consistent across experiments and in some cases were highly influenced by a few observations. Further investigation is warranted before drawing any firm conclusions regarding these interactive effects. This study adds further evidence to the body of literature showing that exposure to low–level step potential resulting in <1 mA rms of 60 Hz electrical current during milking is not a cause of cow discomfort or poor milking performance.

Milking interval, milk production and milk flow-rate in an automatic milking system

One of the characteristics of automatic milking is that cows can visit the milking robot voluntarily. This induces a large variation in the frequency of visits to the milking robot and, thus, results in a large variation in milking intervals. The relationships between milking interval, milk production and milk flow-rate using a milking robot were studied with data from a research farm (66 cows) collected between October 1997 and September 1999 (107 785 milkings). The average milking interval was 9.2 h (S.D.=3.3). The average milk flow-rate was 2.5 kg/min (S.D.=0.79) and the average milk production was 1.3 kg/h. There was a large variation in milking intervals. Respectively, 9.7 and 17.6 percent of the milkings had an interval shorter than 6 h or longer than 12 h. In this variation, cow factors do play a role. Of all cows, 6% had an average milking frequency of less than twice per day. Cow factors and time of the day contributed to the variation in milking interval. In addition to cow factors, the length of the milking interval had a significant effect on milk production and milk flow-rate. The effects of milking interval on milk production per hour were greater for higher producing cows than for lower producing cows. The variation in the milking interval could be part of the explanation for an apparent increase in SCC with automatic milking. Optimisation of the milking frequency and thus the milking intervals is important. This optimisation should consider effects of milking interval on milk production, capacity of the automatic milking system and udder health.

Effect of suckling during early lactation and changeover to machine milking on plasma oxytocin and cortisol levels and milking characteristics in Holstein cows

Plasma concentrations of oxytocin and cortisol, and milk yield and flow rates, were compared in three primiparous cows and two cows in their second lactation during suckling and subsequent machine milking. After calving, cows suckled their calves for 3-4 weeks and then the experiment was carried out over 4 d. Blood samples were taken prior to, during and after suckling or evening machine milking (EMM) on day 1 of the experiment (the last day of suckling), day 2 (first EMM) and day 4 (third EMM). After weaning and rehousing, cows were machine milked twice daily. During the first EMM, average milk yield and flow rate in the second minute of milking were significantly lower (P < 0.05) than corresponding values for the other 2 d. Plasma oxytocin concentrations were lower during the first than during the third EMM (P < 0.001) and suckling (P < 0.001), and more oxytocin was released during the third EMM than during suckling (P < 0.01). Cortisol concentrations were higher during and after the first EMM than during the third EMM. Thus in cows sucked for several weeks after calving and then separated from their calves and rehoused we found a transient decrease in oxytocin release, milk yield and flow rates during the first machine milking.