Normal Milking Research Articles

Effect of mechanical premilking stimulation on milking duration in late lactation.

This study documents the effect of mechanical prestimulation on the milking duration of pasture-based cows in late lactation to better harness increased capacity of automation in the milk harvesting process. Premilking stimulation, provided via manual or mechanical means, has been shown to promote the milk letdown reflex and assist in achieving quick, comfortable, and complete milk removal from the udder. The literature is lacking knowledge on the effect of mechanical premilking stimulation on milking duration, especially in late lactation and in pasture-based systems, and many pasture-based farms do not practice a full premilking routine because of a lack of labor availability. The current study addresses this gap in knowledge. In this study, we tested 2 treatments: (1) the No Stim treatment used normal farm milking settings with no premilking preparation and (2) the Stim treatment used 60 s of mechanical premilking stimulation, with a rate of 120 cycles per minute and a pulsator ratio of 30:70 on cluster attachment. Once the 60 s of stimulation had elapsed, normal milking settings resumed for the remainder of the milking. Sixty cows were enrolled in the study, which ran for 20 d. The effect of treatment on a.m. milking duration was significant, a.m. milking duration for Stim was 12 s shorter than that of No Stim. The effect of treatment on p.m. milk duration was not significant. Treatment had no effect on a.m./p.m. milk yields, average milk flowrates or peak milk flowrates. Significant differences emerged between treatments on a.m. and p.m. dead time (time from cluster attachment to reach a milk flowrate of 0.2 kg/min). The a.m. and p.m. dead times were 6 s shorter for Stim compared with No Stim. The time taken to achieve peak milk flowrate (time to peak) at morning milking was 7 s shorter for Stim compared with No Stim, and treatment yielded no significant effects on time to peak at p.m. milkings. Treatment also had no significant effect on log10 somatic cell count. Although the percentage of congested teat-ends and teat-barrels was numerically lower for Stim versus No Stim, no statistical differences were detected across these measures. Based on the results of the study, we found merit in applying 60 s of mechanical pre-stimulation at a.m. milking from a milking duration perspective. However, the strategy was not as successful for the p.m. milking. Analysis of the milk flowrate profiles recorded during the study suggest potential utility in employing different machine settings for various milkings based on anticipated yield and level of udder fill.

Short communication: Teat wall diameter and teat tissue thickness in dairy cows are affected by intramammary pressure and by the mechanical forces of machine milking

The objective of this study was to validate and apply 2 different methods to record changes in teat tissue related to machine milking. Teat wall diameter was measured via B-mode ultrasound cross sectioning with a 7.5-MHz linear probe. Teat tissue thickness was measured using a cutimeter (spring-loaded caliper, spring constant 6.5 N/cm, 0.5 N at closed jaws). Both methods were applied at the teat barrel, 2 cm above the teat tip. In experiment 1, 24 teats from freshly slaughtered cows were used to perform ultrasound imaging (12 teats) or cutimeter measurements (12 teats) while the teat cisterns were filled with water to increase the intracisternal pressure from 0 to 30 kPa in steps of 1 kPa. Teat tissue thickness did not change at an intracisternal pressure from 0 to 10 kPa but increased with intracisternal pressure at levels >10 kPa. In contrast, teat wall diameter decreased with intracisternal pressure between 0 and 7 kPa but did not significantly change at a pressure ≥7 kPa up to 30 kPa. Significant Pearson correlation coefficients between intracisternal pressure and teat wall diameter were observed from 0 to 7 kPa (r = -0.38), and between intracisternal pressure and teat tissue thickness from 10 to 30 kPa (r = 0.45). In experiment 2, ultrasound and cutimeter measurements were performed in 12 lactating Holstein cows. Measurements before and during milking, immediately after cluster removal, with normal milking or with a 5-min overmilking, were performed and continued at 5-min intervals for 60 min and at 10-min intervals until 120 min. Additionally, with the 5-min overmilking treatment, measurements were continued at 60-min intervals up to 10 h after milking. Teat wall diameter decreased in response to milk ejection, followed by a continuous increase during the course of milking, with highest values after 5 min overmilking. Teat tissue thickness did not change during milking but was significantly increased after overmilking. Teat wall diameter and teat tissue thickness recovered to premilking levels within 35 min after normal milking and within 60 min after overmilking. Until 10 h after overmilking, the teat wall diameter decreased steadily, whereas teat tissue thickness was unfluctuating. In the physiologically relevant range of intramammary pressure, ultrasound measurements of the teat wall were affected by both intramammary pressure and mechanical forces, whereas cutimeter measurements were not affected by the intramammary pressure.

Milk flow obstruction caused by varicose vein of the teat in dairy cattle

To describe varicose vein as a cause of obstruction of the teat cistern in dairy cattle and to report therapeutic options and outcome. Retrospective case series. Dairy cows (n = 22). Medical records (1998-2011) of dairy cows admitted for milking difficulties caused by a teat varicose vein were reviewed. Three treatment approaches were used: sclerotherapy, ligation of the vein associated with sclerotherapy, and phlebectomy. Long-term outcome was obtained ≥ 6 months after treatment and defined as a milking improvement. Descriptive statistics were used to determine the population at risk and a chi square test was used to evaluate the relationship between treatments and outcomes. Twenty-four teats (22 cows) had a varicose vein. Forequarters were more frequently affected than rear quarters (P < .01). Three sclerotherapies, 12 ligations associated with sclerotherapy and 6 phlebectomies were performed. Five veins were not treated. Overall prognosis with treatment was good (84%) at ≥ 6 months and was not significantly different between treatment types (P = .38). Recurrence of the obstruction by the varicose vein occurred in 3 of 19 teats. Several surgical options are available for treatment of teat varicose veins. The overall prognosis of return to normal milking is good.

Glucose and lipid metabolism are modified by short‐term alterations to milking frequency in grazing dairy cows

Short‐term changes to milking frequency (once daily, 1X; or thrice daily, 3X) alter metabolic balance in dairy cows. There are contradictory results regarding effects when cows are switched to normal milking (twice daily; 2X). Cows were allocated to 3 or 6 weeks of 1X or 3X milking post‐calving, switched to 2X milking for the rest of lactation, and compared with cows milked 2X for the whole lactation. Serial liver and adipose biopsies were collected in the first 9 weeks (n=12 cows/trt) and gene expression measured by RT‐qPCR. Data suggests that cows milked 1X had reduced gluconeogenesis and β‐oxidation in liver tissue but increased β‐oxidation and lipolysis in adipose tissue during treatment, compared with cows milked 2X. Cows milked 3X for 6 weeks exhibited reduced lipogenesis and lipolysis in adipose tissue during and post‐treatment. Results indicate that alterations to milking frequency affect carbohydrate and lipid metabolism during, and after treatment. These results increase understanding of the regulation underlying responses to altered milking frequency, and may have implications for farm management. This research was funded through DairyNZ Inc. and the Ministry of Science and Innovation, NZ

The effects of increased milking frequency during early lactation on milk yield and milk composition on commercial dairy farms

Increased milking frequency (IMF) during early lactation has the potential for carryover responses following the return to normal herd milking frequency. The objective was to determine the consistency of response of cows in commercial dairy farms to IMF during early lactation. Cows (n=398) were assigned randomly at calving within each of the 4 participating farms to 1 of 2 treatments. The control group was milked twice-daily (2×) during the entire lactation. The IMF group was milked 4-times daily (4×) starting on d 1 to 7, depending on farm, until d 21 postcalving and 2× thereafter. Cows in the IMF group were milked at the beginning and again at the end of the normal milking routine. Milking intervals differed across the farms for the 4× cows with a minimum interval of 3.5, 4.0, 5.0, and 6h for each of the 4 farms, respectively. The milk yield of cows subjected to IMF increased by 2.2±0.4kg/d during the first 7 mo of lactation. Interactions of treatment with lactation group (primiparous vs. multiparous) were not significant. Although percentages of fat and protein in milk were decreased by early lactation IMF (3.69%±0.03 fat and 3.05%±0.02 true protein for control vs. 3.57%±0.03 fat and 2.99% ± 0.02 true protein for IMF), overall yields of protein were increased by IMF (1.02±0.01 vs. 0.98±0.01kg/d). Early lactation IMF did not affect udder health as assessed by somatic cell count linear score. Cows subjected to IMF were 1.4 times more likely classified as subclinically ketotic than the control cows. Early lactation IMF has the potential to increase milk yield on commercial dairy farms. Although the direction of response was the same on all farms, the magnitude of the response was different among farms and appears influenced by management practices specific to each farm, which included, but were not limited to, housing system, stocking density, nutrition, genetics, and other covariates differing among farms.

Effect of chronic oxytocin-treatment on the bovine mammary gland immune system

The aim of this study was to evaluate the effect of chronic oxytocin (OT) treatment on the mammary gland immune system. In &lt;I&gt;Experiment I&lt;/I&gt; fourteen healthy cows were used to study the effect of chronic intramuscular (im) OT administration on concentration of milk somatic cells and white blood cells (WBC). Cows in the OT-group (6) were im injected with 50 IU OT (5 ml) whereas animals of the C-group (6) were im injected with 5 ml of saline (9 g/l) for eight days (Day 1–8) before each milking. Milk samples were taken during normal milking time on Day 0–3, 5, 7, 9–11 and 18. Blood samples were taken immediately after each milking and analysed for WBC count, polymorphonuclear neutrophils, potassium (K), sodium (Na) and chloride (Cl) ions, and blood lactose. All milk samples were analysed for somatic cell counts (SCC), lactose, Na, Cl and electrical conductivity (EC). Furthermore mRNA expression of tumor necrosis factor-&amp;alpha; (TNF&amp;alpha;), interleukin (IL)-1&amp;beta;, IL-6, IL-8 and cyclooxygenase-2 (COX2) in milk cells were measured via real-time RT-PCR. None of the investigated milk and blood parameters changed significantly in response to the OT treatment. The mRNA-expression of TNF&amp;alpha; decreased (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) to a minimum on Day 3 in response to OT administration. IL-1&amp;beta; and IL-6-mRNA expression decreased (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) to a minimum within three day. IL-8 and COX2 expression did not change in response to OT treatment. In &lt;I&gt;Experiment II&lt;/I&gt; twelve cows, randomly divided into two groups of six, were used to investigate the effect of chronic im OT administration on mammary tissue. Cows were im administered 50 IU OT (OT-group) or 5 ml saline (9 g/l; C-group) before each milking during eight days. Biopsy samples were taken after every morning milking. The mRNA expression of various inflammatory factors and the tight junction (TJ) proteins occludin (OCLN) and zonula occludens (ZO)-1, ZO-2 and ZO-3 were measured via real-time RT-PCR. TNF&amp;alpha;-mRNA expression decreased (Day 2 with &lt;I&gt;P&lt;/I&gt; &lt; 0.05) within the first four days of OT administration and increased (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) in the C-group on Day 2. IL-1&amp;beta; expression levels of the OT-group increased transiently and decreased on Day 3 and in the C-group values increased significantly on Day 3 as compared to Day 0. IL-6 expression in the OT-group decreased (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) to a minimum on Day 1 and increased (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) as compared to Day 0 on Day 7 and increased significantly on Day 1 and Day 5 compared to Day 0 in group C. IL-8 and COX2 expression did not change in response to OT administration. The mRNA-expression of OCLN and ZO-3 decreased (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) as compared to Day 0 with a minimum on Day 7. ZO-1 and ZO-2 expression did not change due to OT administration. ZO-2-mRNA expression in C-group decreased significantly on Day 2 compared to Day 0. In conclusion, chronic OT administration induced increasing SCC and EC levels in milk as well as K and lactose in blood while nearly all investigated cytokines in milk cells and mammary tissue were down regulated. The mRNA expressions of the TJ proteins OCLN and ZO-3 were down-regulated in response to the OT treatment what indicates an increasing TJ permeability. Besides the effect on TJ proteins there was no obvious change of the immunological competence of the mammary gland in response to OT. However, a more complete milk ejection should help to remove pathogens during milking.

Effect of milking interval on milk yield and quality and rate of recovery during subsequent frequent milking

Forty mid-lactation, pasture-fed dairy cows were used to study the effects of milking interval on milk yield and quality and whether effects could be reversed during a short period of subsequent frequent milking. Following a 2-day pre-experimental period of normal twice-daily milking (TDM), cows were milked again after 6, 12, 18, 24 or 30 h, with each milking interval followed by 24 h of frequent milking (i.e., every 6 h). Milk yield increased linearly until 18 h and then started to plateau. Similarly, milk quality (serum albumin and proteolytic enzyme activity) became adversely affected after 18 h. These changes coincided with increased permeability of mammary tight junctions (TJ), starting after a milking interval of 18 h. A brief period of frequent milking helped restore milk yields to pre-experiment levels, even after the longest milking interval.

Milking of Brown Swiss and Austrian Simmental cows in a herringbone parlour or an automatic milking unit

Automatic milking systems (AMS) are becoming increasingly common on dairy farms and should be evaluated for their effect on cow welfare. Dairy cows’ stress responses during normal successful milking in a 2×6 herringbone milking parlour (HMP) were compared with their responses during normal successful voluntary milking in an automatic unit (AMU). We observed 42 cows: 12 Simmental and 11 Brown Swiss in the AMU, and 10 Simmental and 9 Brown Swiss in the HMP. Both prior to and during the observations each cow was milked in one system only. Behaviour during milking and durations of different phases of the milking procedure were observed directly two to six times per cow. Heart rate was recorded telemetrically. Samples of composite milk were analysed for cortisol using an enzyme-immunoassay. Milking lasted longer in the HMP than in the AMU (general mixed model: F 1,39=12.06, P=0.0013), after significant effects of milk yield, day of lactation and time of day had been taken into account. Location of the teats by the robot took longer in Simmental than in Brown Swiss cows (Mann–Whitney- U-test: U 11,12=32, P=0.037). Kicking and stepping with the hind legs was less frequent in the AMU than in the HMP ( U 23,19=76.5 for kicks; U 23,19=85 for steps; P<0.001 in both cases). Brown Swiss cows stepped less than Simmental cows in the AMU ( U 11,12=32, P=0.036). In the HMP, kicks occurred more frequently during the time period from the beginning of udder cleaning until cluster attachment was completed, than at other times (Friedman test: F 19,4=32.41, P<0.001; Bonferroni-corrected post-hoc-comparisons: P<0.01). There was no difference between groups in heart rate during milking. The AMS group had higher milk cortisol values than the HMP group ( U 23,19=130.5, P=0.026). This was probably not related to milking itself, but to other aspects of the system, and absolute values were not very high. In conclusion, Simmental cows may be more vulnerable during milking than Brown Swiss. Limiting the study to successful voluntary milking events without AMU attachment failure, there were no indications of more stress in the AMU than in the HMP.

Effect of Weaning System on Milk Composition and Distribution of Milk Fat within the Udder of East Friesian Dairy Ewes

We investigated whether the inhibition of milk ejection during and/or between machine milkings is responsible for the low milk fat observed in commercial milk obtained from dairy ewes managed with a mixed system (MIX) of partial daily suckling (10h) and once daily machine milking (after 14h of udder filling). East Friesian crossbred dairy ewes were randomly allocated postpartum to the MIX system (n = 9) or to exclusive twice-daily machine milking (DY1, n = 8). Following wk 4, MIX ewes were permanently weaned from their lambs and milked twice daily. All ewes were injected with saline, oxytocin, or an oxytocin-receptor antagonist prior to three morning milkings during wk 2, 4, and 6 of lactation to study cisternal and alveolar milk distribution. Overall milk yield (cisternal + alveolar) for MIX ewes was 42% greater than for DY1 ewes during wk 2 and 4, which demonstrates the beneficial effect of lamb suckling on milk production of dairy ewes. However, during normal machine milking, only the cisternal fraction was obtained from MIX ewes, confirming that milk ejection did not occur for as long as these ewes remained in partial daily contact with their lambs. Although the volume of milk stored within the cistern, and its concentration of milk protein was similar for the two weaning systems, milk of MIX ewes was significantly inferior in cisternal milk fat concentration and yield compared to DY1 ewes. This provides evidence that not only is there inhibition of milk ejection during machine milking of MIX ewes, there is additional inhibition of transfer of milk fat, but not milk protein, from the alveoli to the cistern during the evening when MIX ewes are separated from their lambs. Following weaning of MIX ewes, the majority of lactation traits studied were similar compared to DY1 ewes.

Prevalence, Aetiology and Treatment of Post-Micturition Dribble in Men: Literature review

Summary This literature review of post-micturition dribble in men revealed only eight papers. Three papers identified the prevalence while one described the action of the bulbocavernosus muscle. Two randomised controlled trials and one non-randomised controlled trial were found which explored the effect of pelvic floor muscle exercises on post-micturition dribble and one study investigated the effect of post-micturition dribble on sexual dysfunction. Results suggested that the cause of post-micturition dribble is failure of the bulbocavernosus muscle to perform a normal reflex post-void milking mechanism or urethrocavernosus reflex. Suggested treatment consisted of bulbar urethral massage for immediate self-help and pelvic floor exercises targeted at the bulbocavernosus and ischiocavernosus muscles for an improvement or alleviation of the condition. Men may also benefit from a functional post-void muscle contraction termed ‘squeeze-out' to help develop the normal post-void milking mechanism. Further good quality multi-centre trials are necessary to provide evidence on which to base practice.

Measurement of milk progesterone using near infrared spectroscopy

It is now well established that milk progesterone analysis can provide a valuable tool in reproductive management of the dairy cow. With the advent of relatively cheap cow side milk progesterone tests, the principle block to widespread monitoring is the time and effort involved in the actual collection and analysis of the milk samples. This has led to a research drive to develop on line milk progesterone monitoring systems whereby progesterone is routinely monitored at normal milking. Near-infrared spectroscopy (NIRS) is widely used in the agricultural industry for analysing cereals and forages and is used for on-line testing in the food and pharmaceutical industries. Vibrations of chemical bonds between carbon, oxygen, hydrogen and nitrogen atoms affect the amount of near-infrared light absorbed at individual wavelengths, so different molecules show unique patterns in the spectrum. These patterns are related to determined concentrations of chemicals in calibration samples to develop equations that predict concentrations in unknown samples. This project set out to assess the use of this technique to measure milk progesterone.

Central and peripheral inhibition of milk ejection

Milk ejection can be inhibited as a result of a lack of release of oxytocin (OT) from the pituitary gland, or, when OT is released normally, as a lack of effect on the mammary gland. The former can be overcome by administration of exogenous OT, whereas the latter cannot. Central inhibition of OT release can be caused by several factors, such as relocating cows to unfamiliar surroundings for milking, oestrus, change from suckling to machine milking. In such cases peripheral blood concentrations of β-endorphin and cortisol are elevated. Administration of exogenous cortisol does not cause inhibition of milk ejection. On the other hand, the administration of morphine inhibits OT release from the pituitary, and, therefore, milk ejection. The effect of morphine can be abolished by naloxone (opioid antagonist) administration. However, premilking administration of naloxone does not abolish spontaneous inhibition of milk ejection in cows during milking in unfamiliar surroundings. The role of β-endorphin in central inhibition of milk ejection remains unclear. Peripheral inhibition of milk ejection is caused by exogenous α-adrenergic receptor agonists or OT receptor blocking agents, while OT release from the pituitary is normal. Administered β-adrenergic agonists cause elevated milk flow rates as compared with normal milking. Inhibition of milk ejection by catecholamines cannot be abolished by administration of OT but α-adrenergic receptor blocking agents. Effects of OT receptor blocking agents can be abolished by administration of high dosages of exogenous OT. However, milk flow rates are not reduced as long as milk is present in the cistern. The presence of high concentrations of adrenergic receptors in the teat and lower amounts in more proximal regions of the bovine udder has been demonstrated. Their influence on milkability has been reported and relations between adrenergic receptor concentrations in the udder or on blood platelets and milking characteristics are most likely. Under stress free conditions the sympathetic tone in the mammary gland is reduced during milking and increases between milkings. All these investigations reflect the importance of the sympathic nervous system in the process of milk removal. Milk removal seems to be regulated by the adrenergic system, although the mechanism is not clear.

Lactation failure in crossbred Sahiwal Friesian cattle.

Milk producers in Malaysia make extensive use of crossbred Sahiwal Friesian dairy cattle. These animals have, however, been found susceptible to lactation failure. A survey of cows in an experimental herd of F1 Sahiwal Friesian animals indicated that, in 30% of animals, milk yield decreased to negligible levels within the first 8 weeks post partum. Lactation failure was associated with a progressive increase in the amount of residual milk left in the udder after normal milking. By week 3 of lactation, residual milk volume was significantly greater than that in animals that, based on previous lactation history were not susceptible to lactation failure, and accounted for up to 30% of milk available at the morning milking. The cellular consequences of residual milk accumulation were evident in the activities of acetyl-CoA carboxylase, fatty acid synthetase and galactosyltransferase, key enzyme markers of cellular differentiation, which decreased in glands undergoing lactation failure and were lower than values measured in tissue of control cows. Mammary cell number, estimated by tissue DNA content, was also reduced in animals undergoing lactation failure. These indices of mammary development indicate that lactation failure is the result of premature involution in susceptible animals. Premature involution is a predictable consequence of progressive milk stasis in failing lactation, and attributable to an increase in autocrine feedback by inhibitory milk constituents. The progressive increase in residual milk is, on the other hand, unlikely to be attributable to impaired mammary development. Measurements of milk storage during milk accumulation showed no differences between control and lactation failure cows in the distribution of milk between alveolar and cisternal storage compartments. We conclude that lactation failure in Sahiwal Friesian cows is due to a failure of milk removal, and probably the result of an impaired milk ejection reflex rather than to the glands' milk storage characteristics.

Prediction of Milkline Fill and Transition from Stratified to Slug Flow

Equations were developed to predict milkline fill and the transition from stratified to slug flow under normal milking conditions. The equation to predict fill explained 93% of the variation in the experimental data for 48 to 98 mm milklines sloped at 0.5 to 2%. The prediction equation for the transition from stratified to slug flow accounted for 98% of the variation in the experimentally determined transition points.

Continuously elevated concentrations of oxytocin during milking are necessary for complete milk removal in dairy cows

The importance of elevated concentrations of oxytocin (OT) during the entire milking period was investigated in seven primiparous dairy cows with inherent disturbed milk ejection and in sixteen healthy cows with disturbed milk ejection induced by placing them in an operating theatre. Disturbance of milk removal in both groups has previously been demonstrated to be exclusively due to central blockage of the expected OT release in response to teat stimulation and milking. However, milk ejection can be induced by exogenous OT. OT (0.2 i.u.) was injected i.v. before milking and 49 +/- 6% of the total milk was removed. When plasma OT decreased, milk flow stopped. In response to a second and third injection of 0.2 i.u. OT, 30 +/- 4 and 7 +/- 2% of the milk were removed respectively. The remaining milk was removed with 10 i.u. OT. The lag time from injection of OT to the start of milk flow was inversely correlated with the amount of milk actually removed in response to the OT injection. If 0.2 i.u. OT was injected during intramammary pressure (IMP) recording, IMP immediately increased to its maximum value. After 2.5 +/- 0.3 min, IMP decreased to an intermediate IMP (between preinjection and maximum IMP). After two additional injections of 0.2 i.u. OT and after injection of 0.5 i.u. OT, IMP increased to a similar maximum. However, after injection of 0.5 i.u. OT, maximum IMP lasted longer (2.9 +/- 0.3 min; P < 0.05) than after injections of 0.2 i.u. If OT was continuously infused (0.15 i.u./min) during milking, milk flow lasted until the udder was completely emptied. IMP increased during OT infusion to a maximum which remained stable until infusion was stopped after 10 min. The same IMP maximum was reached after the first individual OT injection (0.2 i.u.), but when plasma OT decreased towards basal concentrations, milk flow ceased and IMP decreased to an intermediate level. Thus continuously elevated OT concentrations such as those during infusion or during normal milking are necessary for complete milk removal.

Effects on milk yield, somatic cell count and milk conductivity of short-term non-milking of lactating quarters of cows

Compensatory changes in daily milk production between quarters within an udder were investigated, together with related changes in cell count and electrical conductivity of fore milk samples. Two quarters per cow were left unmilked for 2 d (Group 1, four cows) or for 4 d (Group 2, four cows), and then all quarters of all cows were milked twice daily for a further period of 16 d. The mean daily yield per cow fell 50% during the period of milking two quarters. Daily yield for cows in Group 1 decreased significantly only during the treatment period and the first post-treatment period of 4 d, whereas the daily yield for Group 2 was significantly reduced during the whole post-treatment period. The cell count for all continuously milked (control) quarters was stable during the experiment, but increased in the treated quarters during the first 4 d of the post-treatment period. Non-milking was accompanied by a significant increase in fore milk conductivity which persisted for an additional 4 d after the resumption of normal milking. Throughout the last 12 d of the post-treatment period milk from both control and treated quarters had significantly decreased conductivity levels compared with the pretreatment values.

An investigation of the changes in sites of milk storage in the bovine udder over two lactation cycles

AbstractThe objective of this work was to investigate phenotypic sources of variation in the sites of storage of milk within the udder. Ten primiparous and 10 multiparous dairy cows were studied over two successive lactations in order to investigate the effects of age, parity and stage of lactation. Cistern and alveolar milk volumes were estimated at a standard 8 h after a normal morning milking by catheter drainage and machine milking with oxytocin respectively. Measurements were made at approximately 9, 20, 30 and 42 weeks of the initial lactation and weeks 1, 4, 7, 10, 20 and 34 of the subsequent lactation. In the initial lactation, there was a significant difference between primiparous and multiparous animals in the rate of decline of total daily milk yield (P&amp;lt; 0·001). Cistern milk yield (kg/8 h) from multiparous animals declined over the lactation whilst that for primiparous animals was maintained. The effect was shown as a significant interaction effect (P&amp;lt; 0·05). For both multiparous and primiparous animals cistern proportion (cistern yield divided by total milk yield at 8h after a normal milking), increased over the lactation (P&amp;lt; 0·001). This was largely a consequence of the reduced total milk yield. Eleven animals were studied through the subsequent lactation. Cistern yield followed a lactation curve of similar form to that for total yield. The decline in cistern yield over this lactation was much greater than the decline with multiparous animals in the previous year. This may, in part, reflect a faster decline in total daily yield. Stage of lactation and parity must be taken into account if a standardized evaluation of cistern characteristics is to be obtained.

Milk removal in familiar and unfamiliar surroundings: concentrations of oxytocin, prolactin, cortisol andβ–endorphin

Eight cows were machine milked either in an operating theatre or in their familiar barn. During the experiments, milk flow curves were recorded and blood samples were taken for determination of concentrations of oxytocin, prolactin, cortisol and beta-endorphin. The milking cluster was attached without udder preparation. After cessation of milk flow, air was blown into the vagina for 2 min. When milk flow had stopped again, 1 i.u. oxytocin and finally 10 i.u. oxytocin were injected to remove the remaining milk. After the start of milking, oxytocin remained basal in unfamiliar, but increased in familiar surroundings. Therefore, during normal milking only 9% of total milk was removed in unfamiliar, whereas 79% was available in familiar surroundings. In response to subsequent vaginal stimulation in the operating theatre, oxytocin increased transiently in five cows and 15-71% of the milk was removed in these animals. In the other three cows in the operating theatre, oxytocin remained basal during vaginal stimulation, and no more milk was available. After injection of 1 i.u. oxytocin, 56 and 11%, and after injection of 10 i.u. oxytocin, 13 and 8% of milk was removed in unfamiliar and familiar surroundings respectively. Concentrations of prolactin increased during the course of milking in both treatments. Premilking concentrations of cortisol and beta-endorphin were elevated in unfamiliar as compared with familiar surroundings. During the course of milking, cortisol increased slightly and beta-endorphin decreased in unfamiliar, whereas both hormones increased markedly during milking in familiar surroundings.(ABSTRACT TRUNCATED AT 250 WORDS)

Milking System Dynamics. 1. Measurement of Variation

Vacuum, air temperature, and airflow in a pipeline milking system are measured at various locations to obtain systemwide data on dynamic variations. High frequency variations caused by vacuum pump operation are attenuated, and slight damping exists. Milk flow causes the greatest vacuum variations within liners during normal milking. Interaction between liners is severe when liner slip or fall-off occurs. Internal air temperature is steady. Mach numbers for internal airflow are small.

Relationship between cisternal storage capacity and tolerance of once-daily milking in dairy cows

Once-daily milking reduces fixed costs, may be used strategically as a quota-management tool and could become the production system of choice in a programme of extensification. However, milk secretion is reduced during once-daily milking, through the action of an autocrine feedback inhibitor. This natural milk protein is active in milk stored within the secretory tissue, but not in cisternal milk (since it is then remote from its site of action). Consequently, large-cisterned cows should tolerate infrequent milking better than those with small cisterns, by virtue of storing a greater proportion of their milk in a site where the inhibitor is inactive. The aim of this experiment was to test this hypothesis.A group of 9 multiparous and 2 primiparous Friesian-Holstein cows from the Hannah herd calving in March and April 1991 were selected for study. All had been free of clinical mastitis during the current lactation. Throughout the experiment the group were managed routinely at grass as part of the main herd, and were fed a flat rate of 2.4 kg/d of an 18% protein concentrate feed. Normal milking was twice daily at 15:9 h intervals, and yield was recorded at each milking.