Morten Dam Rasmussen

Influence of switch level of automatic cluster removers on milking performance and udder health

The effect of a switch level of 200 or 400 g/min for automatic cluster removers on milking performance and udder health was measured with 71 first lactation cows in their first 36 weeks of lactation and with 64 older cows in their first 12 weeks of lactation. Early removal of the milking unit decreased machine-on time by 0.5 min, increased average milk flow rate slightly, improved teat condition significantly and reduced the change in teat end thickness during milking of first lactation cows. Early removal of the milking unit did not affect milk yield or composition, and the incidence and prevalence of subclinical mastitis were the same in the two groups. Fewer older cows developed clinical mastitis in the group switched at 400 g/min, but this was not significant. It is concluded that the milking unit can be detached at a milk flow rate of 400 instead of 200 g/min without having a negative influence on milk yield. Machine-on time is shortened and teat condition improved and udder health does not seem to be affected.

Milking management of dairy buffalo

Abstract In this note, the Authors report a summary of a coming bulletin on milking management of dairy buffaloes published by the International Dairy Federation (IDF). The bulletin includes the following chapters: introduction, milk composition and quality, anatomy of the buffalo udder, physiology of milk ejection, udder health, milking machines for dairy buffaloes, milking routines, milking hygiene, storage of milk, and milk recording. The present paper focuses on anatomy, physiology of milk ejection and how the management around milking can improve milk quality, milk yield and milk flow.

Identification of peptides in milk as a result of proteolysis at different levels of somatic cell counts using LC MALDI MS/MS detection.

The somatic cell count (SCC) in milk is associated with increasing proteolytic degradation of caseins and it has been suggested that enzymes derived from somatic cells contribute to a lower yield and poorer quality of cheese. It is essential to increase the knowledge on naturally occurring milk proteinase activities to better understand how to improve the technological quality of milk. The aim of this work was to identify peptides actually present in milk as a result of proteolysis at different levels of SCC and to assign these peptides to potential responsible proteases where possible. Peptide fractions were prepared from acid whey by ultrafiltration at a molecular cut-off value of 10 000 Da. The peptides were separated using capillary reversed phase high performance liquid chromatography (RP-HPLC) and identified by matrix-assisted laser desorption/ionization-time of flight tandem mass spectrometry (MALDI-TOF MS/MS). Peptides identified ranged in mass from 1023 to 2000 Da, and originated from alphaS1-, alphaS2- or beta-casein. Possible responsible proteases that could be suggested when examining the peptide cleavage sites included plasmin, cathepsin B, D and leukocyte elastase. The results indicated that plasmin was primarily responsible for the observed proteolysis in milk at low cell count, whereas the cathepsins and elastase became implicated at elevated cell count. Specificity and activity of cathepsins and elastase has earlier mainly been studied in model systems, whereas less is known about their activities in milk itself. This is also the first indication of involvement of elastase in milk proteolysis through the unequivocal determination of cleavage sites.

Udder health of cows changing from tie stalls or free stalls with conventional milking to free stalls with either conventional or automatic milking

Udder health and milk production were monitored in cows transferred from tie stalls or loose housing with conventional milking to loose housing with either automatic or conventional milking. Data were collected from 182 Finnish farms from September 1999 to February 2006. Data from the first year before and first year after the changes were compared. A total of 88 herds changed from conventional milking (CM herds) to automatic milking (AM herds), 29 of which were housed in tie stalls and 59 of which were housed in a loose housing barn before the change. Additionally, 94 CM herds milked in loose housing barns that had been housed in tie stalls before the change were included. Milk record data consisted of annual herd size, parity, breed, calving dates, test day data [date, milk yield, and cow somatic cell count (SCC)] and records for treatments of clinical mastitis. Calculations were made for energy-corrected milk yield and logarithmic SCC (logSCC), proportion of cows at risk that experienced an SCC >200,000 cells/mL for the first time (highSCC), and number of treatments of clinical mastitis within a herd. Cows in tie stalls had higher milk yield (28.5 +/- 0.29 vs. 26.5 +/- 0.46 kg/d) and a lower logSCC (4.86 +/- 0.01 vs. 4.95 +/- 0.02) than cows in loose housing barns before the change. After the change, CM herds had slightly better udder health than AM herds because the proportion of cows at risk for highSCC was larger in AM herds (3.3 vs. 2.1%). The change in milking and housing systems caused a decline of 0.8 +/- 0.25 kg/d per cow in energy-corrected milk yield, a slight increase in cow logSCC (from 4.88 +/- 0.01 to 4.93 +/- 0.01), and an increase of 0.6% in the proportion of cows having highSCC (from 2.5 to 3.1). The impact was clearer on herds that began automatic milking. Based on the results, the increase in bulk milk SCC of herds milked automatically in Finland was probably due to reduced separation of mastitic milk in AM herds.

Pressure in the teat cistern and the mouth of the calf during suckling

The principles of todays machine milking techniques have developed since the early 1900s. The original intention to imitate the sucking action of the calf had to be abandoned owing to technical difficulties. Further developments were made on a largely empirical basis and milking technique became a specific complex of tasks, problems and solutions. Consequently, the sucking of the calf was rejected as a model for machine milking. The sucking behaviour and the application of vacuum and/or pressure by the sucking mammalian offspring have been adapted through evolution. Any eventual changes due to ‘recent’ breeding and development of the milking machine remain marginal compared with evolutionary changes. Since the cineradiographic techniques used by Ardran et al. (1957, 1958) it was believed that sucking calves use mainly pressure to transfer a squirt of milk from the proximally closed teat cistern and through the teat canal. The calf creates the pressure by compressing the teat between the tongue and the hard palate from the base of the teat towards the teat end. Cowie (1977) summarized these results as follows: ‘Sucking, that is the production of vacuum within the mouth cavity, is not an essential feature in suckling, although it aids the process. … The act of suckling is thus analogous to hand milking …’. These conclusions were based on visually analysed recordings. McDonald & Witzel (1966) measured pressure in teat cisterns and vacuum at the teat end simultaneously during suckling. Average maximum pressure in the teat cistern was 36·6 kPa and vacuum at the end of the teat averaged −34·6 kPa. These authors concluded that the average differential pressure across the teat canal was 71 kPa. However, this method of calculation gives only the maximal pressure difference and not the average pressure applied by the calf. They noted that vacuum in the teat cistern occurred during the resting phase of a suckling cycle. The calfs sucking technique for single teats during a meal has been analysed (Mayntz, 1996). Further details of pressure and/or vacuum application during suckling at a specific teat remain unknown. The objective of the present study was to extend the current knowledge about milk extraction by sucking calves through continuous and simultaneous measurements of positive and negative pressure in the teat cistern and in the mouth cavity.

Visual scoring of milk mixed with blood.

Sorting of normal and abnormal milk at time of milking is done visually for conventional milking systems, but more concrete standards are needed when milking is done in automatic milking systems (AMS). Several panel tests were carried out to find out how different consumer groups, milkers and advisors look at and respond to the visual appearance of milk mixed with blood, in order to set a limit for what they think is acceptable. It is concluded from the test panel results that milk samples with 0.4% or more of blood all will be scored as pink and samples with 0.1% blood (about 6 microM-haemoglobin or 100 mg/l) can be visually detected if they are compared with milk samples without blood. The consumer group scored fewer of the samples with 0-1% blood as normal than did the professional groups. The test panel scored 65% of the samples with 1% blood as normal when milk was presented in a black strip cup, which is the reference method when foremilking takes place in a conventional parlour. Only 2% of the milk samples with 2% blood (about 120 microM-haemoglobin or 2000 mg/l) were scored as normal in a black strip cup and should consequently be detected by conventional as well as automatic systems. One model of AMS was tested for its ability to detect and separate milk coloured by blood. The model separated milk with > or = 6 microM-haemoglobin. Milk mixed with blood injected into the milk stream for a short time at the beginning of milking was not separated. We lack data on how blood is naturally expelled into milk and in what amount. We propose that cow composite milk with > 6 microM-haemoglobin should be separated because at this level milk will have a red tinge.

Visual scoring of clots in foremilk

The necessary unequivocal and generally accepted definitions of normal and abnormal milk are not available. A precise definition is needed in order for companies to develop sensors to detect and sort abnormal milk at the time of milking. Experts at a workshop defined abnormal milk to be that from cows whose foremilk had changed in homogeneity or was coloured by blood. The objectives of this paper were: firstly, to explore how different groups of people scored the appearance of foremilk; and secondly, to develop a method suitable as an objective reference for testing of manual and automatic detection systems. Consumers, farmers and advisors did not agree on the visual appearance of normal, watery, clotty milk, or milk with blood, and experience is needed to score the visual appearance of foremilk correctly. It seems reasonable to expect a sensitivity of at least 70% for detection of abnormal milk during foremilking. Filter sizes 0.05, 0.07, 0.1, 0.2, 0.5, 1.0, and 2.0 mm were used to filter milk from cows with visually abnormal foremilk. If clots appeared in the foremilk, clots appeared on all size filters, but the filter with pore size 0.1 mm was the easiest to read and work with. The filter method is not reliable in identifying quarters with watery, yellowish, or bloody milk, whereas the method seems consistent, and at least as good as scoring of visual appearance in finding clots in the milk. Clots should show clearly on the filter to be counted as abnormal milk. All clinical cases with clots in the foremilk can be found on the filter and such cases have high somatic cell count (SCC). Both trained and untrained persons using the filter method can score normal and abnormal foremilk with a high specificity (>90%) and a high sensitivity (>80%). The filter method is recommended as a reference for scoring the homogeneity of foremilk.

Effect of pulsation rest phase duration on teat end congestion

The objective of this study was to quantify the effect of d-phase (rest phase) duration of pulsation on the teat canal cross-sectional area during the period of peak milk flow from bovine teats. A secondary objective was to test if the effect of d-phase duration on teat canal cross-sectional area was influenced by milking system vacuum level, milking phase (b-phase) duration, and liner overpressure. During the d-phase of the pulsation cycle, liner compression facilitates venous flow and removal of fluids accumulated in teat-end tissues. It was hypothesized that a short-duration d-phase would result in congestion of teat-end tissue and a corresponding reduction in the cross-sectional area of the teat canal. A quarter milking device, designed and built at the Milking Research and Instruction Laboratory at the University of Wisconsin-Madison, was used to implement an experiment to test this hypothesis. Pulsator rate and ratios were adjusted to achieve 7 levels of d-phase duration: 50, 100, 150, 175, 200, 250, and 300ms. These 7 d-phase durations were applied during one milking session and were repeated for 2 vacuum levels (40 and 50kPa), 2 milking phase durations (575 and 775ms), and 2 levels of liner overpressure (9.8 and 18kPa). We observed a significant reduction in the estimated cross-sectional area of the teat canal with d-phase durations of 50 and 100ms when compared with d-phase durations of 150, 175, 225, 250, and 300ms. No significant difference was found in the estimated cross-sectional area of the teat canal for d-phase durations from 150 to 300ms. No significant interaction was observed between the effect of d-phase and b-phase durations, vacuum level, or liner overpressure.

Short communication: Changes in gait symmetry in healthy and lame dairy cows based on 3-dimensional ground reaction force curves following claw trimming

Lameness is a frequent health problem in dairy cows. This preliminary study aimed to detect gait differences between healthy and lame walking cows using 3-dimensional force plates. We examined left-right leg symmetry changes of healthy and lame Holstein dairy cows following claw trimming. Gait scoring (GS) was performed on d -5, 0, 1, and 7 relative to claw trimming. Before the experiment, 5 cows walked normally (initial GS=1) and 4 cows limped moderately on a hind leg (initial GS=3). Gait was measured on d -2, -1, 0, 1, and 7 relative to trimming by obtaining ground reaction forces as cows walked repeatedly across 2 parallel 3-dimensional force plates. From the ground reaction forces, stance phase data were derived using computerized procedures. Left-right leg symmetries of entire curves in the 3 force directions were calculated. Effects of lameness and trimming were analyzed in a mixed model, using a low lameness threshold (GS>1). One week after claw trimming, only one cow was mildly lame. In addition, the symmetries of all 3 dimensions were significantly improved shortly after trimming. Importantly, lameness significantly worsened vertical symmetry. Lame cows walked significantly more slowly than healthy cows. In conclusion, all force symmetries seemed capable of detecting gait responses to claw trimming. Although our results are based on a small number of animals, vertical leg symmetry was affected by lameness.

Milking performance and udder health of cows milked with two different liners.

The effects of milking cows with two different liners were measured for a period of 8 months with 115 Danish Holstein cows divided into two groups. Group H and L animals were milked with liners with mouthpiece cavity heights of 30 and 18 mm respectively (other dimensions also differed between the two liners). Average teat lengths of first lactation cows were 45 and 40 mm for front and rear teats. Older cows had teats approximately 10 mm longer. There was no difference in milk yield or milk flow rates between the two groups. Average machine-on time was shorter for group L, and first lactation cows of group L were less restive. The frequency of red and blue discoloured teats immediately after milking was higher for group H, and teat length increased on average 5 mm during lactation with no increase for group L. The small overall differences in udder health between the two groups were not significant. Udder health was better for first lactation cows of group L, even though liners of group L slipped more often and cows with recorded liner slip had poorer udder health. We conclude that special attention should be given to first lactation cows when liner type is selected for a herd. We propose that breeding programmes should ensure that teat length is kept above 50 mm.