Short Milk Research Articles

Assessing liner performance using on-farm milk meters

The primary objective of this study was to quantify and compare the interactive effects of liner compression, milking vacuum level, and pulsation settings on average milk flow rates for liners representing the range of liner compression of commercial liners. A secondary objective was to evaluate a methodology for assessing liner performance that can be applied on commercial dairy farms. Eight different liner types were assessed using 9 different combinations of milking system vacuum and pulsation settings applied to a herd of 80 cows with vacuum and pulsation conditions changed daily for 36d using a central composite experimental design. Liner response surfaces were created for explanatory variables milking system vacuum (Vsystem) and pulsator ratio (PR) and response variable average milk flow rate (AMF=total yield/total cups-on time) expressed as a fraction of the within-cow average flow rate for all treatments (average milk flow rate fraction, AMFf). Response surfaces were also created for between-liner comparisons for standardized conditions of claw vacuum and milk ratio (fraction of pulsation cycle during which milk is flowing). The highest AMFf was observed at the highest levels of Vsystem, PR, and overpressure. All liners showed an increase in AMF as milking conditions were changed from low to high standardized conditions of claw vacuum and milk ratio. Differences in AMF between liners were smallest at the most gentle milking conditions (low Vsystem and low milk ratio), and these between-liner differences in AMF increased as liner overpressure increased. Differences were noted with vacuum drop between Vsystem and claw vacuum depending on the liner venting system, with short milk tube vented liners having the greater vacuum drop than mouthpiece chamber vented liners. The accuracy of liner performance assessment in commercial parlors fitted with milk meters can be improved by using a central composite experimental design with a repeated center point treatment, rotating different clusters to different stalls (milk meters), and adjusting performance estimates for similar claw vacuum and pulsation conditions.

Effect of automatic cluster removers on milking efficiency and teat condition of Manchega ewes

Milking operations represent more than 50% of the work on a dairy ewe farm. The implementation of automatic cluster removers (ACR) is gaining popularity, as it allows the operator to avoid manual cluster detachments, simplifying the milking routines. The aim of this study was to discover the effect on the milking of Manchega ewes over an entire lactation period by using this type of devices, set up with 2 different combinations of milk flow threshold (MF) and delay time (DT) and comparing them with the traditional method using manual cluster removal. During a 15-d pre-experimental period, the animals were milked without ACR and sampling was performed to select 108 ewes and distribute them into 3 groups of similar characteristics according to their parity, milk yield, milking duration, and mammary gland sanitary status. Later, each group was milked for a duration of 4mo in 3 different conditions: 1 with manual cluster removal, the second setting the ACR at MF 150g/min and DT 20 s, and the third setting the ACR at MF 200g/min and DT 10 s. Samplings of milking fraction, milking duration, milk composition, mammary gland sanitary status, teat-end status, and vacuum level in the short milk tubes during milking were performed. The use of ACR limited the vacuum drops in the short milk tubes and the edema in the teat end after milking, although no reduction in the number of new cases of mastitis was observed and the milk composition did not change. Moreover, it was noted that the use of ACR set with MF 150g/min and DT 20 s was more efficient than the manual cluster removal, as it obtained a similar amount of extracted milk but took less time. Conversely, the use of ACR set with MF 200g/min and DT 10 s involved a higher reduction in individual milking duration and the milking duration of groups of animals but reduced milk extracted.

Effect evaluation of short term non-lactose milk powder feeding for neonatal diarrhea

Objective To explore the effect of short term non-lactose milk powder feeding for neonatal diarrhea.Methods Totals of 140 cases of neonatal diarrhea who were selected from March 2013 to February 2014 were randomly divided into observation group and control group .The observation group adopted short term non-lactose milk powder feeding , while the control group accepted long term non-lactose milk powder feeding . The effect of treatment , gastrointestinal symptom , average weight growth and milk powder tolerance were compared.Results In the observation group, the recovery, effective and ineffective neonatus were fifty one cases, seventeen cases and two cases respectively , while there were forty seven cases recovered , twenty nine effective cases and three ineffective cases in the control group .There were no statistical significance （ Z =0.758,P=0.366）.The observation group had better results than the control group on average weight growth [（34.30 ±7.35） g/（kg· d） vs （24.29 ±8.06） g/（kg· d）] and milk powder intake [（105.37 ± 24.02）ml/（kg· d） vs （97.21 ±21.66）ml/（kg· d）], and the differences were statistically significant （t=2.809,3.161, respectively;P 〈0.05）.In the observation group, the frequency of defecation, vomiting, ventosity and gastric retention were less than those of the control group （P〈0.05）.Conclusions The short term feeding of lactose free milk powder is not only suitable for infant ’ s growth and immune system improvement , but also economical and valuable for clinical application widely . Key words: Diarrhea,infantile; Non-lactose; Milk powder feeding

335 GENETIC ENGINEERING OF GOATS FOR THE PRODUCTION OF A BIOSIMILAR ANTIBODY IN MILK

Dairy animals provide an attractive production platform for biosimilar antibodies due to the high protein production capacity of the mammary gland and easy access to milk. Goats are well suited for this approach as they offer a relatively short gestation time and good milk yield and are fully validated for the production of recombinant therapeutics. To generate transgenic goats capable of producing a biosimilar version of cetuximab, a monoclonal antibody for epidermal growth factor receptor and approved for the treatment of specific cancers, we co-transfected primary female fetal fibroblasts with expression constructs for cetuximab’s heavy (HC) and light (LC) chains under the control of the goat β-casein regulatory sequences. Beta-globin insulators were added to both transgenes to minimize position effects, and an antibiotic selection marker was placed downstream of the HC transgene sequences to allow for the isolation of stable transgenic cell clones. Selected cell clones were screened by PCR for the presence of both transgenes. Positive cell clones were analysed by Southern blot with a β-casein-specific probe. This allowed for the simultaneous detection of both transgenes, and the endogenous β-casein gene served as a standard to determine transgene copy numbers. The cell clones showed a broad range of copy numbers, from single copy insertions to >100 copies for the HC and LC transgenes. Interestingly, most of the cell clones had more LC than HC transgene copies. Ten cell clones were selected to generate transgenic founders using somatic cell nuclear transfer. We were able to produce 43 live kids from 9 cell lines following transfer of between 26 and 153 one- and two-cell embryos per line into recipients (range of 4 to 15 embryos per recipient). The one cell clone that we used unsuccessfully had the lowest number of transferred embryos (11). The efficiency for the production of live kids per transferred embryos was, on average, 5.1% (range of 1.0 to 9.7%). Kids from 5 lines were hormonally induced into lactation at the age of 10 weeks. Two lines with high copy numbers (≥30) produced either no or only a few drops of milk, whereas the lines with ≤25 transgene copies gave up to several milliliters of milk per day. Western analyses confirmed cetuximab production levels of 15 g L–1 in 2 of the lines with ≤25 transgene copies and ~45 g L–1 in a high copy number line; one low copy number line showed good HC but very low LC expression. Our data demonstrate that cetuximab can be produced in significant quantities in transgenic goats. Future work is aimed at determining production levels under natural lactation conditions and characterising glycosylation patterns to fully understand the pharmacodynamic properties of the antibody. Supported by GTC, the NZ Ministry of Science and Innovation and AgResearch.

Milk flow-dependent vacuum loss in high-line milking systems: Effects on milking characteristics and teat tissue condition

To study the effects of a milking system that partially compensates for milk flow-dependent vacuum loss compared with a standard (high-line) milking unit in a tie-stall barn, milk flow and vacuum patterns were recorded in 10 cows during machine milking with 2 milking systems in a crossover design for 7 d each. Before and after each treatment period postmilking teat condition was recorded by ultrasound cross-sectioning. Additionally, 2 methods to measure teat tissue condition were compared: longitudinal teat ultrasound cross-sectioning and teat tissue density measurements with the spring-loaded caliper (cutimeter method). The partial compensation of milk flow-dependent vacuum loss caused an elevation of the peak flow rate (4.74±0.08 vs. 4.29±0.07 kg/min) and a shorter duration of plateau (1.57±0.06 vs. 1.96±0.07min) compared with the standard milking system. Total milk yield, duration of incline and decline of milk flow, average milk flow, time until peak flow rate, main milking time, and total milking time did not differ between treatments (overall means: 13.75±0.17kg; 0.65±0.01min; 2.88±0.09min; 2.82±0.05 kg/min; 1.65±0.03min; 5.23±0.09min, and 5.30±0.10min, respectively). The vacuum drop in the short milk tube during periods of high milk flow was less in the compensating vacuum than in the standard milking system (11±1.1 vs. 15±0.7 kPa). Teat measures as determined by ultrasound remained unchanged over the entire experimental period with both milking systems. Postmilking teat tissue measures including their recovery within 20min after the end of milking show a correlation (0.85 and 0.71, respectively) between the methods used (ultrasound and cutimeter method). In conclusion, a more constant vacuum at the teat tip (within the short milk tube) during periods of high milk flow affected milk flow patterns, mainly increasing peak flow rate. However, the reduced vacuum loss did not increase the overall speed of milking. In addition, effects of higher vacuum stability on teat condition and udder health were not obvious.

Effects of a Low Vacuum Level on Vacuum Stability and Milking Parlor Performance for Sheep

In line with the current interest in animal welfare in animal husbandry, this study of two groups of 24 sheep compares milking performances at a low vacuum level (28 kPa) and at a standard level (42 kPa) that is normally used for sheep. The two working vacuum levels were tested with three different combinations of pulsator rate and pulsator ratio. Each of the experiments lasted 21 days, of which 11 were for adaptation and 10 were for collecting data. The milking machine used was a low line with 24 stalls, 12 milking units controlled by two operators, a milk line 74 mm in diameter, and a cluster with a total mass of 490 g. The measurements performed were the dynamics of the vacuum level in the short milk tube and the milk line during milking, and the time duration for each individual milking. There were no significant differences in fluctuations in vacuum in either the short tube or the milk line at the two vacuum levels used. By contrast, there was a significant increase in vacuum fluctuations in the short milk tube when the pulsator ratio changed from 50% to 60%. The milk flow time for each sheep increased on average by 17% with low vacuum, while the throughput of the system was reduced by some 4%, from 333 to 321 sheep/h.

Effects of low vacuum levels on vacuum dynamics during milking

One of critical points of the milking unit is the short milk tube. Here milk plugs can cause abrupt variations in vacuum which are stressful for the animals. Our trials allowed us to define the effects of the operational vacuum and pulsation on vacuum stability in the short milk tube. Reducing the vacuum from 42 to 28 kPa did not produce appreciable variations in vacuum fluctuation. It was 9.2 kPa for the low vacuum and 9.8 kPa for the standard vacuum. Changing the pulsation rate from 150 to 120 cycles/min did not modify the vacuum stability in the short milk tube. By contrast, raising the pulsation ratio from 50% to 60% significantly increased the amplitude of vacuum fluctuation in the short milk tube.

Influence of Air Intake on the Concentration of Free Fatty Acids and Vacuum Fluctuations During Automatic Milking

The main objective of the study was to determine whether the amount of air intake during quarter milking influences the concentration of free fatty acids (FFA) and vacuum fluctuations at the teat end when milking automatically. Air intake in the teat cup was restricted from the normal inlet of 4.5 to 7 L/min to 1.7 and 0 L/min on 2 farms and experiments were carried out as half-udder studies with 40 cows. Blockage of the air inlet reduced FFA from 1.02 to 0.77 mEq/100g of fat in one herd and from 1.50 to 1.17 mEq/100g of fat in the other herd. Milk yield per milking was the most significant factor influencing FFA. Air intake accounted for <20% of the variation in FFA concentration. Characteristics of the cow explained the most variation, which could mainly be assigned to the effects of milk yield, fat percentage, fat globule size, and fat globule size distribution. The interval between milkings was not significant when adjusting for milk yields. Blockage of the air inlet caused vacuum fluctuations at the teat end to increase from 15.4 to 21.5 kPa for one model of an automatic milking system (AMS), but from 12.8 to 53.6 kPa for another model. Measurements made with a flow simulator and water revealed that the AMS model and water flow were the most important factors influencing vacuum fluctuations, and that interactions existed between the diameter of the short milk tube and air intake. Free fatty acids in bulk milk from 5,980 herds averaged 0.75 mEq/L of milk for conventional herds and varied from 0.77 to 0.94 mEq/L of milk for the 5 AMS models on the Danish market. Fault detection in 55 herds pointed out that the most frequent faults in conventional herds were air leakages and intake of too much air in the cluster, whereas AMS herds had problems with the cooling and stirring of milk. Correction of the cooling faults caused FFA to decrease by 0.52 mEq/L in the AMS herds. We concluded that air intake during automatic milking is not the most important factor in reducing FFA, whereas milk yield per milking matters the most. More attention should be paid to the cooling and stirring of milk. Reducing the air intake causes vacuum fluctuations during milking to increase significantly.

Use of recorded nursing grunts during lactation in two breeds of sows. I. Effects on nursing behaviour and litter performance

The impact of exposing lactating sows and their litters to recorded sow nursing grunts played at different intervals during lactation was studied. Yorkshire × Landrace (YL) and 25% Meishan (MH) primiparous sows were divided into three groups (n = 14): (1) no playback, (2) playbacks at 35-min intervals (GR35), and (3) playbacks at 40-min intervals (GR40). Recordings were played from day 110 of gestation to day 27 of lactation. Nursing behaviours, incidence of nursings without milk ejection (NPN), nursing interval and proportion of nursings induced by playbacks were measured on days 6, 18 and 26 of lactation. Litter size was standardized to 10 ± 1 piglets within 48 h of birth and piglets were weighed weekly. Mean nursing intervals, excluding NPN, were shorter for MH than for YL sows (P &lt; 0.001). The increase in mean nursing interval between days 6 and 18 was greater in GR40 than in GR35 or controls (P &lt; 0.01) and, when excluding NPN, the mean nursing interval decreased in GR35 on day 18 (P = 0.01). The occurrence of NPN decreased as lactation advanced (P &lt; 0.001) and was lower for MH than YL sows on day 26 (P &lt; 0.001). Between days 6 and 18, the proportion of nursings initiated by playbacks increased (P &lt; 0.05) and the duration of milk ejection decreased (P &lt; 0.001). In MH sows, controls had longer milk ejections than GR35 (P &lt; 0.05) whereas, in YL sows, controls had shorter milk ejections than GR40 (P &lt; 0.05) and GR35 (P = 0.06). Piglet growth was not affected by treatments or breed (P &gt; 0.1). In conclusion, exposing sows and their litters to recorded sow nursing grunts played at 35-min intervals reduced nursing intervals on day 18 of lactation only, without affecting piglet performance. Key words: Auditory stimulus, behaviour, lactation, litter performance, Meishan, sows

Physico-chemical surface characterization of a bacterial population isolated from a milking machine

The hydrophobicity of 26 species of bacteria representative of the main genera isolated from a rubber short milk tube, which is a constituent of a cluster from a milking machine, was determined. The materials forming the cluster namely rubber, stainless steel (SS) 316, stainless steel (SS) 304, glass and polymethylmethacrylate (PMMA) were also assayed in terms of hydrophobicity. In relation with the hydrophobicity of bacteria, all the strains of Lactobacillus lactis lactis as well as of Enterococcus faecalis are hydrophobic. Concerning Pseudomonas aeruginosa and Staphylococcus sciuri, some are hydrophobic and others are hydrophilic. All the materials are hydrophobic, being rubber, SS 316 and SS 304 the most hydrophobic surfaces while glass is the less hydrophobic.The free energy of adhesion between the bacteria and the materials in aqueous medium was calculated and used to predict which material of the cluster has a higher ability for biofilm formation and by this way contribute for milk contamination due to the release of bacteria from the deposit. For all the situations studied, adhesion is thermodynamically favourable to SS 316, SS 304 and rubber and less favourable to PMMA and glass.

INSTRUMENT REQUIREMENTS AND METHODS FOR MEASURING VACUUM IN MILKING MACHINES

The instrument specifications given in current international (ISO) and national (ASAE) standards state thatmeasured values should be within 90% of the true amplitude of vacuum change at the various locations in the milking machine.Recommendations are given for the minimum sampling rate and response rate of instruments used to measure vacuum changesfor dry, wet, milkingtime, and cleaningtime tests. These minimum performance requirements should ensure that themeasurement accuracy stated in the ISO and ASAE standards are met.A simple method was developed to measure the response rate of a vacuum recording system. The method can be used, quicklyand easily, by field or laboratory technicians to specify the response rate of their vacuum recording systems. The predominanteffects on response rate of vacuum recording systems are caused by the fittings connecting the electronic vacuum recorderto the measurement point. A major source of measurement error was water or milk in connecting tubes and fittings.Dry and wet tests in the milkline and receiver confirmed previous studies showing that the rate of vacuum change during drytests or in dry parts of the milking machine are much lower than those in wet parts of the machine. The fastest vacuum changeswere measured in the short milk tube and mouthpiece chamber during a liner slip in a milkingtime test. Measurements madein the short milk tube during wet tests corresponded well with those made during wet tests at the teatend of the ISO standardudder.

Effects of Milkline Vacuum, Pulsator Airline Vacuum, and Cluster Weight on Milk Yield, Teat Condition, and Udder Health

The influence of milkline vacuum, pulsator airline vacuum, and cluster weight on complete lactation milk yield performance, teat condition, and udder health were studied in 241 cows by using three separate factorial experiments. The first experiment had milkline vacuum set at 38 and 48 kPa, pulsator airline was vacuum was set at 0 and 8 kPa above milkline vacuum, and cluster weight was 1.6 and 2.3kg. The second experiment had milkline vacuum set at 38 and 48 kPa and cluster weight was 1.6 and 2.3kg. The third experiment had milkline vacuum set at 32 and 42 kPa and pulsator airline vacuum 0 and 8 kPa above milk line vacuum. The first two experiments were carried out with a high-level milking and the third with a low-level milking system. The average vacuums in the short milk tube during milking for low and high milkline vacuum in the high-level system were 26 and 33 kPa, and 30 and 39 kPa for the low-level milking system, respectively. Milking at low vacuum increased the machine-on time and frequency of liner slip, decreased milk flow rate, but had no influence on teat condition and udder health. The milk yield of high producing cows with long machine-on time was reduced by 5% when milked at a low vacuum. A higher pulsator airline vacuum than milkline vacuum had no influence on milking performance. The use of the light cluster reduced machine-on time. We recommend that mean vacuum in the short milk tube should not be lower than 32 kPa.

Treatment of Clinical Mastitis

Mastitis continues to be of great importance to the US dairy industry. When diseases on dairy farms were recently evaluated according to effects on productivity, international trade, animal welfare, and zoonotic risk, mastitis ranked highest, above salmonellosis, paratuberculosis, and bovine virus diarrhea.1 Subclinical mastitis caused by contagious mastitis pathogens still causes substantial economic loss on some US dairy farms, but it can readily be controlled by dry cow antibiotic therapy, hygiene practices in the milking parlor, and selective culling. In herds that have achieved contagious mastitis control, clinical mastitis caused by opportunistic pathogens in the environment or on teat skin is the predominant form of the disease.2,3 Because these pathogens are ubiquitous, eradication of clinical mastitis is an unreasonable goal. Rather, dairy producers must strive to reduce the incidence of clinical mastitis by instituting hygienic practices that minimize exposure of teats to pathogens and by optimizing immune function through proper nutrition and vaccination. When clinical mastitis develops, as it does at an annual incidence rate of &lt; 5% to &gt; 50%,4 veterinarians and dairy producers must make appropriate treatment decisions.&#x0D; Despite decades of treating clinical mastitis, controversy still exists about when and how to treat it, particularly in herds that have controlled contagious pathogens. The predominant mastitis-causing pathogens in those herds are coliform bacteria, Streptococcus spp. other than Streptococcus agalactiae (environmental streptococci), and Staphylococcus spp. other than Staphylococcus aureus.2,3 An ideal treatment regimen would be one that is safe, reduces pain and suffering, is efficacious (resulting in rapid clinical and bacteriological cure), causes short milk and slaughter withholding times, avoids unnecessary drug use or excessive labor, positively impacts milk production and survivability, and is economical. Almost certainly the ideal regimen would differ for mild, moderate, and severe episodes of clinical mastitis and episodes caused by different pathogens. Hundreds of different treatments for clinical mastitis are used daily on US dairy farms, but, in general, even the most common treatments have not been studied in controlled clinical trials to determine if they are better than no treatment at all. In the remainder of this paper, I will discuss some of the common treatments for clinical mastitis in herds that have controlled contagious mastitis, and suggest areas for future study.

Examination of systems that exert traction on the teatcup and reduce teat bending in machine milking of ewes

Summary — Two systems were designed to exert traction on the teatcups and reduce the bending of teats during machine milking: 1 ) an articulated arm, which held the teatcups in a fixed position throughout milking; and 2) a system using springs, which were joined to the short milk tube at one end, and hooked onto a wire mesh at the other end after the teatcups were attached. These systems were compared with the traditional milking system in a Latin square design (3 x 3 weeks), using 36 Manchega ewes in their 3rd week of machine milking, after 5 weeks of suckling. Ewes were milked twice a day with machine and hand strippings. The system using springs produced an increase in total milk production compared with the traditionally milked control group, although the increase was not very large (3.7%). However, its composition (percentage of fat and protein) and residual milk did not vary. Fractionation also improved, increasing machine milk by 16% and decreasing the stripping (machine stripping by 60%; hand stripping by 26%). The arm system produced lower total milk production (6%) when compared with that of the control milking system, although the composition and residual milk did not vary. The machine milk fraction was similar to that of the control group, but stripping decreased by 41 and 7% for the machine and hand strippings, respectively. Teatcup falls increased slightly in the spring (6.6%) and arm (8.9%) systems compared to the control milking system (5.1 %). The incidence of mastitis, estimated with California mastitis test, did not vary significantly. In conclusion, a simple spring that exerts traction on the teatcup and reduces teat bending gives better milk fractionation. This could be interesting economically when stripping is eliminated from the milking routine (rotary parlours with automatic cluster removers).

Cow Sensitivity to Electricity During Milking

Alternating currents were delivered to lactating cattle through the milk during milking. Electrodes were placed at the top of each short milk tube and jointed for one electrical contact. A metal grid on which the cows’ rear hooves stood during milking was the second contact. Constant voltages (0 to 16V) applied to contacts showed first lactation cows to be more sensitive than multiple lactation cows. First lactation cows kicked milking machines at 8V (currents >5mA), and multiple lactation cows kicked at 16V (currents >8mA). At lower voltages, there were no consistent significant differences in milking duration, milk yield, or composition for primary or residual milk. Application of constant currents of 5mA for first lactation cows and 8mA for multiple lactation cows produced no undesired behaviors but did result in some differences in production variables. Milking duration decreased during application of constant current to first lactation cows. Blood cortisol monitored in the multiple lactation cows during trial 2 showed a significant increase during milking but was equivalent or less during application of current. This study demonstrates that currents of 5mA or less, delivered through the milk line, did not produce any direct economic effect. To produce this current, voltages on the milk pipe line would have to be in excess of 125V (obvious human safety hazard) or in excess of 5V on the claw of the milking cluster.

Effect of the Short Milk Tube Check Valves on Milking Rate, Milk Yield, and Transfer of Bacteria Among Quarters

To determine effect on milk yield, milking time, and rate. Holstein cows were milked using machines equipped with or without short milk tube check valves. In each of three experiments, 16 cows were divided into two groups of 8. Experiments 1 and 2 employed a crossover experimental design; Experiment 3 used a switchback design. Check valves increased 2-min milk yields in all experiments and increased 3-min yields in Experiments 1 and 3, but decreased 3-min yields in Experiment 2. Total milk yield was decreased by check valves in Experiments 1 and 3 but was not affected by check valves in Experiment 2. Milking time was not affected by check valves in Experiments 1 and 3, but decreased in Experiment 2. In two other experiments, three cows were used in a 3 x 3 Latin square to measure transfer of a marker bacteria between teat cups. Bacteria transfer was not different among machines equipped with conventional, check valve, or shielded liners. The check valves functioned during full milk flow, producing hydraulic milking conditions, but they ceased functioning when milk flow declined in the later stages of milking. The check valves were ineffective in increasing milking rate and milk yield and are unlikely to prevent teat end impact.

Milk Temperature in the Claw Piece of the Milking Machine and Mammary Surface Temperature are Predictors of Internal Mammary Temperature in Goats1

Mammary internal and surface temperatures and milk temperature were correlated using five lactating goats. Internal mammary temperature was estimated using temperature-sensitive transmitters placed deep within the parenchyma of each mammary half. External mammary temperature was estimated using infrared thermography of four mammary skin sites: T1, teat end; T2, teat base; G1, about 20 mm above the teat base; and G2, about 20 mm ventral to the base of the gland deep to the thigh. The thermistor bead used for estimating milk temperature was placed in the claw piece where the short milk tube of the liner attaches. This placement minimized cooling effects of milk contact surfaces. The overall correlations of milk temperature with mammary temperatures ranged from 0.45 to 0.64. Correlations among the six paired values for the four external sites ranged from 0.76 to 0.92. Milk and surface temperatures, milking time, and milk weight were employed in various combinations as covariables; these were calculated within animal, within half. Milk temperature was the single most important predictor of internal mammary temperature in all models. Milk temperature alone or combined with covariables can be used to predict internal mammary temperature.

Nursing interaction of Wistar rats is modified by prior experience of altered nursing bout length.

We tested the capacity of 2 week postpartum Wistar rat litters and their dams to adapt to experimental shortening and lengthening of the time available for nursing while maintaining the frequency of bouts constant, using manual transfer between cage compartments. In 8-hr and 24-hr experiments, the short bout group (10 min/hr) gradually came to show normal litter weight gain, short latency milk ejections, and increased high arched nursing position, while the 40-min/hr group showed increased latency to attachment and longer latency to ME compared to the 20 min/hr control group. Pup body temperature did not vary between groups. Although pups in the 10-min group showed increased dam-directed behaviors in the first 8h, this difference vanished thereafter. In a twenty-fifth cycle, after dams and litters were exchanged, the prior experiences of the dams and not of the litters were found to determine the dynamics of milk exchange.

Improved milking characteristics of teatcups fitted with non-return valves

SummaryThe milking characteristics of conventional clusters were compared with individual teatcups or clusters fitted with valves in the short milk tubes without external air admission to the liners. Individual teatcups fitted with non-return valves had peak milk flow rates 13% higher than conventional teatcups. A daily cross-over experiment involving 36 cows compared clusters fitted with non-return valves to conventional clusters. Valved clusters milked 18% faster, showed significantly better teatcup stability and 3% higher machine milk yields, but 48% higher strip yields were recorded. Clusters with non-return valves were difficult to remove after milking because the valve closed when the vacuum supply was shut off, thereby maintaining the vacuum level under the teats. When the nominal plant vacuum level for teatcups with non-return valves was reduced by 10 kPa to compensate for the higher effective milking vacuum level, the valved teatcups had peak flow rates 20% lower than the conventional teatcups. Clusters fitted with a modified valve, which allowed some reverse flow when closed (a ‘leaky’ valve), milked significantly faster than conventional clusters, had 33% lower strip yields and were easy to remove after milking.

Milk temperature fluctuations during milking in cows with subclinical mastitis

Observations on fluctuations of milk temperature during milking were carried out on 114 cows. A sensitive thermistor mounted in the short milk tube was used to measure milk temperature; fluctuations were very frequent in cows with subclinical mastitis as diagnosed by the presence of mastitis pathogens, high cell count, increased electrical conductivity and chloride content. Similar fluctuations were found in experimentally infected quarters of some cows. The fluctuations seem to indicate disorders in milk ejection and the automated measuring technique may be used as a tool in the early diagnosis of mastitis.