Quarter Milk Yield Research Articles

Comparing the Performance of Automatic Milking Systems through Dynamic Testing Also Helps to Identify Potential Risk Factors for Mastitis.

Automatic milking systems (AMSs) are revolutionizing the dairy industry by boosting herd efficiency, primarily through an increased milk yield per cow and reduced labor costs. The performance of milking machines, whether traditional or automated, can be evaluated using advanced vacuum meters through dynamic testing. This process involves scrutinizing the system and milking routine to identify critical points, utilizing the VaDia™ logger (BioControl AS, Rakkestad, Norway). Vacuum recordings were downloaded and analyzed using the VaDia Suite™ software under the guidance of a milking specialist. Access to data from AMSs across various manufacturers and herds facilitated a retrospective study aimed at describing and comparing key milk emission parameters for different AMS brands while identifying potential mastitis risk factors. Using the proper statistical procedures of SPSS 29.1 (IBM Corp., Armonk, NY, USA), researchers analyzed data from 4878 individual quarter milkings from cows in 48 dairy herds. Results indicated a significant variability in milking parameters associated with quarter milk yield and AMS brand. Notably, despite AMSs standardizing teat preparation and stimulation, this study revealed a surprisingly high frequency of two major mastitis risk factors-bimodality and irregular vacuum fluctuations-occurring more frequently than in conventional milking systems. This study, one of the few comparing different AMS brands and their performance, highlights the crucial role of dynamic testing in evaluating AMS performance under real-world conditions.

Decreased lactose percentage in milk associated with quarter health disorder and hyperketolactia, a proxy for negative energy balance, in dairy cows

Several studies have described variations in lactose content (LC) in dairy cows during udder quarter health disorder or negative energy balance (NEB). However, their joint effects on LC have never been described. This was the aim of a longitudinal observational study performed on 5 Quebec dairy farms using automatic milking systems. Quarter milk samples were collected every 14 d from 5 to 300 DIM. Quarter health status was described by combining SCC level (SCC- or SCC+: < or ≥100,000 cells/mL) and infectious status (Patho- or Patho+: presence or absence of pathogens on a milk culture). Cows with NEB in early lactation (DIM <70) were identified using milk β-hydroxybutyrate (BHB) content: 0.15 mM = BHB-; 0.15 - 0.19 mM = BHB+; > 0.19 mM = BHB++. A total of 14,505 quarter cisternal milk samples were collected from 380 lactating cows. The quarter LC was analyzed using a mixed linear regression model with the following fixed effects: quarter health status, parity, time interval between last milking and sampling, quarter milk yield (in kg/d), DIM, and herd. A random quarter intercept with a repeated measures correlation structure and a cow random intercept were also specified. The LC of SCC+ quarters was lower (-0.17 ± 0.013% pts) compared with LC of SCC- quarters for both primiparous and multiparous cows. Over the 162 bacterial species identified, only 8 species had a prevalence greater than 4.0%, and just 5 of them were associated with a reduction in LC: Staphylococcus aureus, Staph. chromogenes, Streptococcus dysgalactiae, Staph. epidermidis, and Staph. simulans. Cows identified as BHB+ and BHB++ in early lactation had a lower LC (-0.05 ± 0.019% and -0.13 ± 0.020% pts, respectively) compared with BHB- cows. For BHB++ cows, in both parity groups the decrease in LC (-0.20 ± 0.025% pts) was higher in SCC+ quarters compared with SCC- quarters. Moreover, the additive effect of the quarter health status and NEB on milk LC was greater with larger increases in BHB. Our findings highlight the necessity to jointly take into consideration both quarter health status and milk BHB concentration when using LC as a biomarker for NEB.

Molecular characterization of persistent subclinical mastitis-causing Staphylococcus aureus from dairy farms.

The study aimed to evaluate the genetic diversity of Staphylococcus aureus causing subclinical mastitis (SM) isolated from dairy cows and to assess the effect of the infection status (transient vs. persistent) on the milk and component yield. A total of six dairy farms in São Paulo state were used for the selection of cows with SM caused by S. aureus. S. aureus strains (n = 56) obtained from three biweekly aseptic mammary quarter milk samplings (n = 1140 from 95 cows) were subjected to MALDI-TOF MS analysis for species confirmation and further PFGE analysis. Intramammary infections (IMI) caused by S. aureus were categorized as transient (T: when only one out of 3 milk samplings had positive isolation of any pulsotype) or persistent (P: when two (P2) or three (P3) milk samplings had positive isolation of identical pulsotype over the consecutive episodes of SM. The SmaI macrorestriction fragment profiles of 56 S. aureus isolates showed a dominant S. aureus clonal pattern (PFGE type A; n = 50; 89.3%) within and among the herds. The SM-causing S. aureus represented a reduction of quarter milk yield of 26.2% in transient and 54.8% in persistent cases as well as a reduction of total solid yield of 38.1% and 49.4%, respectively, when compared with the healthy control quarters. Overall, the greater chance of S. aureus to be persistent is when a dominant clonal pattern is present in the herd which consequently may be associated with the cause of accentuated milk loss.

Association between Udder and Quarter Level Indicators and Milk Somatic Cell Count in Automatic Milking Systems.

Simple SummaryIn dairy cattle herds milked by automatic systems, the absence of a human milker originates the need for control systems to monitor the milking process and cow conditions. Modern milking robots are equipped with a lot of sensors that, at each milking (2.5–3 times a day), record data on milk yield and quality, milking efficiency, cow welfare, and health with particular focus to udder conditions. Mastitis is one of the most frequent and serious diseases of dairy cow that negatively affects milk quality and yield, reduces animal welfare, and often implies the use of antimicrobial drugs. At the moment, the alerting systems for mastitis risk is generally based on monitoring milk electrical conductivity, color, and/or temperature, but these indicators have limited reliability. Other information gathered by automatic sensors, already implemented in commercial robots, could be useful to early detect mastitis. Using a multivariate approach, our study showed that the deviations over time of milk electrical conductivity, milk yield, and milk flow of single quarters in comparison with the whole udder are potential indicators, alone or in combination, for altered udder conditions. The results could be useful for the development of new algorithms more effective in the early detection of mastitis.Automatic Milking Systems (AMS) record a lot of information, at udder and quarter level, which can be useful for improving the early detection of altered udder health conditions. A total of 752,000 records from 1003 lactating cows milked with two types of AMS in four farms were processed with the aim of identifying new indicators, starting from the variables provided by the AMS, useful to predict the risk of high milk somatic cell count (SCC). Considering the temporal pattern, the quarter vs. udder percentage difference in milk electrical conductivity showed an increase in the fourteen days preceding an official milk control higher than 300,000 SCC/mL. Similarly, deviations over time in quarter vs. udder milk yield, average milk flow, and milking time emerged as potential indicators for high SCC. The Logistic Analysis showed that Milk Production Rate (kg/h) and the within-cow within-milking percentage variations of single quarter vs. udder milk electrical conductivity, milk yield, and average milk flow are all risk factors for high milk SCC. The result suggests that these variables, alone or in combination, and their progression over time could be used to improve the early prediction of risk situations for udder health in AMS milked herds.

Longitudinal study on the effects of intramammary infection with non-aureus staphylococci on udder health and milk production in dairy heifers

We conducted a longitudinal study to evaluate the effect of non-aureus staphylococci (NAS) causing subclinical intramammary infections (IMI) on quarter milk somatic cell count (qSCC) and quarter milk yield (qMY). In total, 324 quarters of 82 Holstein Friesian heifers were followed from calving to 130 d in milk (DIM) and were sampled 10 times each at 14-d intervals. The IMI status of each quarter was determined based on bacterial culture results at the current and previous or next sampling day, or both. The qSCC was determined on each sampling day and the average qMY on sampling day was available through stored daily milk weight data in the management program of the automatic milking system. A transient IMI (tIMI) was defined as a case where a specific pathogen was isolated from a quarter on only one sampling day and not on the previous or next sampling day. When the same bacterial strain, as defined by random amplification of polymorphic DNA-PCR, was isolated from the same quarter on multiple sampling days, it was defined as a persistent IMI (pIMI) status on those sampling days; a pIMI episode was defined as the combination of multiple consecutive pIMI statuses with the same bacterial strain on different sampling days. During this study, 142 subclinical IMI with NAS occurred in 116 different quarters from 64 animals, yielding in total 304 NAS isolates belonging to 17 different species. The prevalence of NAS was highest in the first 4 DIM. Overall, the predominant species was Staphylococcus chromogenes (52% of the isolates), followed by S. epidermidis (9.2%), S. xylosus (8.2%), and S. equorum (5.9%). Staphylococcus chromogenes was the only species for which an effect on qSCC and qMY could be analyzed separately; the other NAS species were considered as a group because of their low prevalence. Eighteen out of 40 IMI (45%) caused by S. chromogenes persisted over at least 2 sampling days, whereas only 10 of 102 (9.8%) IMI caused by other NAS species persisted for at least 2 sampling days. The average duration of pIMI episodes was 110.4 d for S. chromogenes and 70 d for the other NAS species. Remarkably, 17 of the 18 pIMI episodes with S. chromogenes started within the first 18 DIM. The qSCC was highest in quarters having a pIMI with a major pathogen, followed by quarters having a pIMI with S. chromogenes, and a pIMI with other NAS. Transient IMI with other NAS or with a major pathogen caused a small but significantly higher qSCC, whereas the qSCC in quarters having a tIMI with S. chromogenes was not statistically different compared with noninfected quarters. No significant differences in qMY were observed between quarters having a pIMI or tIMI with S. chromogenes or with the other NAS species compared with noninfected quarters, despite the higher qSCC. Quarters having a pIMI with major pathogens showed significantly lower daily milk production. Surprisingly, quarters that cured from an IMI with S. chromogenes had a significantly lower qMY than noninfected quarters.

Pathogen effects on milk yield and composition in chronic subclinical mastitis in dairy cows

This study aimed to evaluate the effects of chronic subclinical mastitis (CSM) on milk production and component yields in dairy cows. A total of six herds located in the Midwest area of São Paulo State, Brazil were selected. Herds were visited once every 2 weeks to measure milk yield and to collect milk samples from lactating Holstein cows. Milk samples were collected at two stages (1 and 2), and each stage comprised three milk samplings. In stage 1, a total of 117 of 647 cows were diagnosed with CSM based on at least two of three repeated somatic cell counts (SCC) > 2000,000 cells/mL and positive bacterial milk culture results (BC). Cows with CSM were selected for the second stage. In stage 2, selected cows had quarter sampling aseptically collected for BC analyses prior to milking, and quarter milk yield was measured. Milk components (total protein, fat, lactose, and total solids) were measured using mid-infrared spectroscopy. Mammary quarters were considered healthy if all three repeated SCC results were ≤ 200,000 cells/mL and no bacterial growth was detected on BC. All quarters with positive bacterial growth were classified as having (non-chronic) subclinical mastitis when only one of three SCC results were > 200,000 cells/mL, and CSM when at least two of three SCC results were > 200,000 cells/mL. The effects of CSM by type of pathogen on milk and components yield were assessed using a linear mixed model.Mammary quarters with CSM caused by major pathogens had milk loss of 1.1 kg/quarter milking in comparison to healthy quarters. Milk losses were 0.8 and 1.3 kg/quarter milking when CSM was caused by Staphylococcus aureus or environmental streptococci, respectively. In addition, healthy quarters produced more milk components than quarters with CSM caused by major pathogens. Minor pathogens causing CSM (non-aureus staphylococci and Corynebacterium spp.) had no effect on milk yield. Quarters with CSM had lower milk and component yields when compared with healthy quarters. Milk losses varied according to the type of pathogen and were higher when associated with major pathogens such as S. aureus and environmental streptococci compared with healthy quarters.

The effect of intramammary infection in early lactation with non-aureus staphylococci in general and Staphylococcus chromogenes specifically on quarter milk somatic cell count and quarter milk yield

This longitudinal study aimed to evaluate the impact of subclinical intramammary infection (IMI) with non-aureus staphylococcal (NAS) species in the first 18 d in milk (DIM) on the quarter milk somatic cell count (qSCC) and quarter milk yield (qMY) during the first 4 mo of lactation in Holstein Friesian heifers. Quarter milk samples were collected from 82 heifers from 1 to 4 DIM until 130 DIM on a biweekly (14 d) basis for determination of the qSCC; qMY data were available through the automatic milking systems. The quarter samples collected on the first (1-4 DIM) and second (15-18 DIM) sampling days were used for bacteriological culturing to determine the IMI status. In this study, 324 quarters from 82 heifers were enrolled, of which 68 were NAS-infected at the first sampling day. Only 16 (23.5%) of these quarters were still NAS-infected at the second sampling day, demonstrating the high spontaneous cure rate of these infections shortly after calving; 9 of these 16 cases were infected with the same NAS species. Interestingly, none of the NAS-infected quarters at the first sampling day acquired a new infection with a major pathogen at the second sampling day, whereas 2.3% of the noninfected quarters did. All 102 isolates phenotypically identified as NAS were further identified to the species level. Staphylococcus chromogenes was the most prevalent species on the first (29.4% of all NAS) and second (52.9%) sampling days. Quarters infected with Staph. chromogenes at the first sampling day had a significantly higher qSCC in later lactation than noninfected quarters, whereas this was not true for quarters infected with all other NAS species (i.e., as a group of species). The average daily qMY in the first 4 mo of lactation did not differ between noninfected quarters and quarters infected with Staph. chromogenes or all other NAS species at the first sampling day. Persistently NAS species-infected quarters in the first 18 DIM (i.e., infected with the same NAS species on the first and second sampling days) had the highest qSCC later in lactation, followed by quarters with a new NAS IMI (i.e., noninfected at the first sampling day and infected with NAS at the second sampling day). The qSCC from transiently NAS species-infected quarters (i.e., not infected with the same NAS species at the second sampling day) was not significantly higher in later lactation compared with that in noninfected quarters. The IMI status of quarters in the first 18 DIM, combining culture results at 1 to 4 and 15 to 18 DIM (new, persistent, and transient IMI), was not significantly associated with daily qMY in the first 4 mo after calving. In general, NAS should be considered minor pathogens with no adverse effect on daily qMY in quarters of heifers infected in the first 18 DIM and with a high spontaneous cure rate. Staphylococcus chromogenes was the most prevalent species, causing an increase in qSCC comparable to the level of quarters infected with a major pathogen; Staph. chromogenes caused most infections that persisted through at least the first 18 DIM.

Pattern of milk yield and immunoglobulin concentration and factors associated with colostrum quality at the quarter level in dairy cows after parturition

First colostrum yield and constituents as well as milk yield during established lactation vary considerably among mammary quarters in dairy cows. However, data on the development of milk yield, IgG concentration, and their distribution per quarter within cows during the first milkings after calving are scarce. We analyzed milk production and IgG concentration at the individual quarter level in 29 multiparous Holstein cows during the first 5 milkings after calving. Cow- and calf-related factors (time interval between calving and first milking, parity number, previous lactation yield, gestation length, dry period length, sex, and birth weight of the calf) potentially affecting first colostrum quality and quantity were assessed. Milking of first colostrum was carried out between 30 and 180 min after parturition. Further milkings were performed twice daily. Quarter milk yield varied between 0.1 and 5.5 kg at the first milking and between 1.4 and 5.1 kg at the fifth milking relative to parturition. Quarter IgG concentration ranged between 18.8 and 106.0 mg/mL at the first milking and between 0.8 and 46.1 mg/mL at the fifth milking. Distribution of milk yield and IgG concentration among quarters was not entirely repeatable during the first 5 successive milkings after parturition; that is, the ranking of quarters changed (intraclass correlation coefficients for quarter milk yield and IgG concentration: 0.64 and 0.79, respectively). The average hourly milk production increased in all quarters, ranging from 0.02 to 0.26 kg/h between the first 2 milkings up to 0.11 to 0.45 kg/h between the fourth and fifth milkings. First colostrum yield was not affected by any of the evaluated cow- and calf-related factors. Quarter colostrum IgG concentration was higher in cows with a higher previous lactation yield, whereas a lower colostrum IgG content was observed in cows with a longer gestation period and consequently heavier calves. In conclusion, milk yield and IgG concentration of individual quarters varied considerably, and their distribution among quarters within cows was moderately repeatable in consecutive milkings and changed partially over time. The decline of IgG concentration was independent of the concomitant increase in milk secretion, with changes occurring at different rates in individual quarters. Our results confirm the independence of the single mammary quarters at the onset of lactation despite an identical exposure to endocrine stimuli.

Effect of intramammary infection with non-aureus staphylococci in early lactation in dairy heifers on quarter somatic cell count and quarter milk yield during the first 4 months of lactation

A longitudinal study was conducted to assess to what extent intramammary infection (IMI) with non-aureus staphylococci (NAS) within the first 4 d after calving in dairy heifers affects quarter milk yield (qMY) and quarter milk somatic cell count (qSCC) during the first 4 mo of lactation. In total, 324 quarters from 82 Holstein Friesian heifers from 3 commercial dairy herds equipped with an automatic milking system were included and followed from calving up to 4 mo in lactation. The automatic milking system allowed us to precisely determine the daily qMY. A milk sample from each quarter was collected in early lactation (between 1 and 4 d in milk) for bacteriological culturing and measurement of the qSCC. Subsequently, milk samples were taken on a biweekly basis for measurement of the qSCC. The milk prolactin level in early lactation was measured, and the relation with NAS IMI was determined. Overall, NAS IMI in early lactation caused only a slight but significant increase in qSCC compared with milk from noninfected quarters during the first 4 mo in lactation, whereas no significant difference in daily qMY was present between NAS-infected and noninfected quarters. The milk prolactin level in early lactation did not differ between NAS-infected and noninfected quarters either. Our data suggest that IMI with NAS (as a group) present shortly after calving do not have an adverse effect on later production. The milk prolactin concentrations were not dissimilar between NAS-infected and noninfected quarters and thus cannot explain why NAS-infected quarters do not produce less than noninfected quarters.

Method for short-term prediction of milk yield at the quarter level to improve udder health monitoring

Udder health problems are often associated with milk losses. These losses are different between quarters, as infected quarters are affected both by systemic and pathogen-specific local effects, whereas noninfected quarters are only subject to systemic effects. To gain insight in these losses and the milk yield dynamics during disease, it is essential to have a reliable reference for quarter-level milk yield in an unperturbed state, mimicking its potential yield. We developed a novel methodology to predict this quarter milk yield per milking session, using an historical data set of 504 lactations collected on a test farm by an automated milking system from DeLaval (Tumba, Sweden). Using a linear mixed model framework in which covariates associated with the linearized Wood model and the milking interval are included, we were able to describe quarter-level yield per milking session with a proportional error below 10%. Applying this model enables us to predict the milk yield of individual quarters 1 to 50 d ahead with a mean prediction error ranging between 8 and 20%, depending on the amount of historical data available to estimate the random effect covariates for the predicted lactation. The developed methodology was illustrated using 2 examples for which quarter-level milk losses are calculated during clinical mastitis. These showed that the quarter-level mixed model allows us to gain insight in quarter lactation dynamics and enables to calculate milk losses in different situations.

Electrical conductivity of milk as related to daily milk yield of udder quarters in automatically milked cows

The aim of the study was to determine the frequency of udders with specific levels of milk electrical conductivity and milk yield in primiparous and multiparous cows. Relationships between the health and milk yield of individual udder quarters in the primiparous and multiparous cows were also analysed. The left and right front quarters constituted, respectively, 67.39 and 67.90% of the quarters from which milk with electrical conductivity ≤5.50 mS/ cm was drawn. In the conductivity class &gt;7.00 mS/cm, the right and left rear quarters showed the highest proportions (9.59 and 7.13%, respectively). Individual udder quarters from the cows most often produced either less than 7.00 kg or more than 10.00 kg milk per day. These differences concerned the front and rear udders. In the first two classes of milk electrical conductivity, the frequency of individual udder quarters in the primiparous and multiparous cows was similar. For milk with the lowest electrical conductivity, the values ranged from 50.38% (front left) to 52.62% (rear left) in primiparous cows, and from 47.38% (rear left) to 49.62% (front left) in multiparous cows. As the health of the mammary gland deteriorated, daily milk production of all its quarters was observed to decrease. A more marked reaction to this condition was observed in the front quarters, the yield of which decreased by 3.40 kg (left) and 3.02 kg (right). The rear left quarters decreased their yield by 2.85 kg/day, and the rear right ones by 2.18 kg/day. Higher production levels in all mammary quarters and in every milk electrical conductivity class were noted in the multiparous cows. The increasing milk electrical conductivity was paralleled by a lower daily milk yield of the udder quarters in both primiparous and multiparous cows. For the front left and right quarters, this decrease was 2.77 and 2.41 kg in the youngest cows, and 4.27 and 4.26 kg in the older cows. The decrease in milk production from the rear left quarters was 2.67 kg/day in primiparous and 3.76 kg/day in multiparous cows; the respective values for the rear right quarters were 2.01 and 3.86 kg milk/day.

Association of quarter milking measurements and cow-level factors in an automatic milking system

The primary aim of this observational study, in a single herd milked using multiple automatic milking system units, was to describe associations of quarter milk yield variability and quarter peak milk flow rate with cow-level factors. Information from the current lactation of 1,549 primiparous and multiparous cows was collected from January to December 2015. Data from each individual milking used in the analysis included quarter milk yield (QMY), udder milk yield, quarter peak milk flow rate (QPMF), quarter average milk flow rate (QAMF), quarter milking time, and milking interval. Milking interval and milk yield were used to calculate milk production rate (kg/h) at the quarter and udder levels. We investigated associations between QPMF and milking interval, QPMF and days in milk, and QMY and QAMF. A strong association between QPMF and both QAMF and milking interval was observed. A moderate association was found between QPMF and stage of lactation. However, QMY was not a useful indicator of QPMF because of the weak association observed between these variables. In this study, rear quarter QPMF was significantly increased by 3% compared with front quarter QPMF (1.45 vs 1.41 kg/min). Quarter milk yield was calculated as a percentage contribution of total udder milk yield per 10-d in milk window and ranked from lowest to highest contribution. Quarter contribution to udder milk yield showed a high level of variability, with 39% of animals having all 4 quarters change contribution rank at least once during part of or the whole lactation. Only 14% of cows were observed to have no change in quarter rank. When quarter contribution was assessed, irrespective of physical position of quarter within the udder, the percent of highest to lowest contribution across the lactation was relatively stable. The standard deviation of quarter milk production rate for each cow was regressed against the same cow's peak udder milk production rate, within a lactation, to ascertain whether quarter milk production rate variance could be used to predict peak udder milk production rate. Knowledge of the intra-udder quarter milk production rate standard deviation for an individual cow is not useful in predicting peak udder milk production rate. Quarter milking time appears to be a useful indicator to predict the optimal order of teatcup attachment. Analysis from this large, single-herd population indicates that QPMF is associated with the cow-level factors milking interval and days in milk, and that intra-udder QMY is highly variable.

Bovine subclinical mastitis reduces milk yield and economic return

The effect of different pathogens was studied by evaluating the contralateral (healthy and infected) mammary quarters of 146 lactating cows. The impact of SM on economic return (quarter milk yield × milk price) was determined by applying milk payment estimates on milk collected from healthy vs. infected glands. Cows were considered infected when they had at least 2 out of 3 weekly composite SCC results > 200 × 103 cells/mL and a microbiological culture (MC) positive result from composite foremilk samples, collected in the third week of sampling. Infected cows were evaluated a second time within 15 days and had milk yield measured at the quarter level and foremilk samples collected by aseptic technique for analysis of MC, milk composition and SCC. Of the 611-composite milk samples, 397 (65%) were culture-negative, and 214 (35%) were culture-positive and the most frequent isolated bacteria were Corynebacterium spp. (7.9%), coagulase negative staphylococci (5.8%), Staphylococcus aureus (5.3%), Streptococcus uberis (4.6%), Streptococcus agalactiae (3.9%), other environmental streptococci (2.4%), Gram-negative isolates (2.4%), Enterococcus spp. (1.4%) and Streptococcus dysgalactiae (0.7%). A total of 55 pairs of healthy contralateral quarters (control) were compared, and no difference was observed between them when evaluating SCC, milk yield, fat and protein concentration and economic return. A total of 124 pairs of healthy had lower SCC (274.9 × 103 cells/mL) than infected contralateral quarters (SCC of 1038.5 × 103 cells/mL). At the quarter level, IMI caused by minor pathogens had no effect on SCC, milk yield and economic return. Subclinical mastitis caused by contagious and environmental pathogens increased SCC and decreased milk yield when compared with healthy contralateral quarters. Moreover, quarters infected by contagious pathogens had increased concentrations of milk protein and fat when compared with healthy contralateral quarters. Therefore, the milk economic return was lower in quarters with SM caused by environmental pathogens (US$ 0.18/quarter.milking) and contagious (US$ 0.22/quarter.milking) when compared with healthy contralateral quarters. The milk losses ranged from 0.07 kg/quarter.milking to 1.4 kg/quarter.milking and the economic losses ranged from US$ 0.02–0.4/quarter.milking according to the pathogen causing SM.

Effect of incomplete milking on milk production rate and composition with 2 daily milkings

The primary aim of this study was to assess the effects of incomplete milking on milk secretion and milk composition at the quarter level. Twelve cows were enrolled beginning at 5 d in milk and remained on study through 47 d in milk. Half of each contralateral udder was incompletely milked (treatment), detaching the teat cup early to leave approximately 30% of the total milk yield behind. This target milk remaining in the gland was based on weekly calibration milking measurements of quarter total milk yield. Control quarters were milked completely until milk flow had decreased to 0 kg/min based on visual assessment. Harvested milk yield was measured twice daily at each milking, and milk components (fat, protein, lactose, solids nonfat, milk urea nitrogen) and somatic cell count, were measured twice weekly at the quarter level. The experimental unit in this design was the half-udder, and a mixed-model approach was used to assess the main and interactive effects of experiment week and treatment on milk production rate, milk remaining in the gland, and milk composition. The effect of treatment on milk production rate was significant, with the average control half-udder producing 0.97 kg/h and the treatment half-udder 0.73 kg/h. The effect of week on milk production rate and the interaction of week × treatment were also significant. The effect of treatment on milk remaining in the gland was significant, illustrating that an increase in milk remaining in the cisternal compartment had been achieved. We detected a significant decrease in milk lactose percentage in treatment half-udders, and a significant increase in somatic cell count (log10). The increase was relatively small, from a geometric mean of 26,300 cells/mL in control quarters to 48,300 cells/mL in treatment quarters. The decrease in milk production rate in treatment half-udders supports current knowledge about how mammary epithelial cell secretion, proliferation, and apoptosis are modulated by autocrine-paracrine factors.

Study on Prevalence of Sub-Clinical Mastitis in Crossbred Dairy Cattle and its Potential Risk Factors

The study was designed to determine the prevalence of sub-clinical mastitis in cross-bred dairy cattle and potential risk factors associated with the disease. The study was conducted in organized dairy farm at Jammu, and milk samples collected from 106 animals were put to MCMT (Modified Californian Mastitis Test). The overall prevalence of sub-clinical mastitis was found to be 59.43 per cent (%) and quarter level prevalence was at 34.78%. The risk factors under study; parity, age, milk yield and position of quarters, had significant influence on prevalence of sub-clinical mastitis. Prevalence was high in animals with greater than 20 litre (77.41%) of milk yield, and those falling in age group of greater than 8 years (82.92%). In relation to parity of animals and position of quarters, prevalence was maximum in six and above parity animals (78.6%), and with regard to position of quarters, mostly right hind quarters (49.39%) were affected. The pathogens isolated were mostly contagious in nature, and Staphylococcus aureus (66.67%) was most commonly found organisms.

Milk prolactin response and quarter milk yield after experimental infection with coagulase-negative staphylococci in dairy heifers

Coagulase-negative staphylococci (CNS) are the most common bacteria involved in subclinical mastitis in dairy cows. Remarkably, CNS-infected dairy heifers produce more milk than uninfected heifers. Because the lactation hormone prolactin (PRL) is also involved in mammary gland immunity, we investigated the milk PRL response and the mammary quarter milk yield following experimental CNS challenge. Eight healthy Holstein-Friesian heifers in mid-lactation were experimentally infected using a split-udder design with 3 different CNS strains: one Staphylococcus fleurettii (from sawdust bedding) and 2 Staphylococcus chromogenes strains (one isolate from a teat apex, the other isolate from a chronic intramammary infection). Three mammary quarters per heifer were simultaneously inoculated with 1.0×106 cfu, whereas the remaining mammary quarter was infused with sterile phosphate-buffered saline, serving as a control. An existing radioimmunoassay was modified, validated, and used to measure PRL frozen-thawed milk at various time points until 78h after challenge. The mean milk PRL level tended to be higher in the CNS-challenged mammary quarters compared with the control mammary quarters (7.56 and 6.85ng/mL, respectively). The increase in PRL over time was significantly greater in the CNS-challenged mammary quarters than in the control mammary quarters. However, no difference was found in the PRL response when comparing each individual CNS strain with the control mammary quarters. The mean mammary quarter milk yield tended to be lower in the CNS-infected mammary quarters than in the control mammary quarters (1.73 and 1.98kg per milking, respectively). The greatest milk loss occurred in the mammary quarters challenged with the intramammary strain of S. chromogenes. Future observational studies are needed to elucidate the relation between PRL, the milk yield, and the inflammatory condition, or infection status, of the mammary gland.

Staphylococcus aureus intramammary infection affects milk yield and SCC of dairy cows.

Staphylococcus aureus (S. aureus) is the most prevalent infectious microorganism affecting dairy cattle worldwide, and its pathogenic characteristics facilitate its spread in dairy herds. S. aureus intramammary infections (IMI) are mainly subclinical, and associated losses can exceed average herd losses where the pathogen is not isolated. However, the extent it affects milk composition at udder and quarter levels is still unknown, and cow composite milk losses may be underestimated due to the dilution effect. The aim of this study was to investigate the effects of S. aureus subclinical mastitis on mammary quarter milk yield and composition. In order to determine the effects of the pathogen on milk yield and composition at quarter level, a pairwise comparison of infected and non-infected mammary quarters (n = 28) from two dairy herds was carried out. Quarters were individually milked, and milk production and composition were assessed. S. aureus has increased somatic cell counts at quarter level; however, no effect of S. aureus IMI on milk lactose, fat, and protein contents was observed. Fat yield from infected quarters decreased, but losses due to the infection caused by S. aureus were not associated with quarter positioning in cows.

Effect of sub-clinical mastitis on milk yield and composition of dairy goats in Tanzania.

Production of dairy goats is on the increase in East African countries. As in cows, prevalence of mastitis in dairy goats appears to be high but studies on the influence of this disease on milk yield and composition are scarce. This study was, therefore, carried out to determine the effect of sub-clinical mastitis on milk yield and composition in dairy goats of Magadu dairy farm in Morogoro, Tanzania. Does were screened for mastitis using the California Mastitis Test (CMT), milk yield was recorded and 80 ml samples collected for laboratory analyses. A total of 184 quarter milk yield samples were available for analyses. Milk samples were analysed for butterfat (BF) by the Gerber method, crude protein (CP) by the Kjeldahl method, lactose by IDF Standard No.28 method and chloride by titration using silver nitrate solution. Data were analysed using least squares analysis of variance based on General Linear models procedures. The fixed effects considered were CMT score, parity, stage of lactation, sampling occasion and quarter of the udder. Sub-clinical mastitis had a significant negative effect on quarter milk yield (P Keywords : Mastitis, milk yield, composition, goats. AJFAND Vol. 9 (1) 2009: pp. 623-634

Interaction of Somatic Cell Count and Quarter Milk Flow Patterns

Milk flow parameters at udder and quarter levels were studied in relation to somatic cell count (SCC) and other risk factors for mastitis (bimodality, duration of decline, and duration of overmilking phase). Thirty-eight Holstein cows in their first to sixth lactations were investigated during 10 mo of lactation. Monthly milk samples were collected for SCC during morning milking. Quarter and udder milk flows were recorded daily. A cow was included if one quarter was found to have an SCC higher than 200×103 cells/mL. A total of 3,262 quarter milk flow curves and 804 udder milk flow curves from 22 cows (6 primiparous and 16 multiparous) were selected and evaluated. Selected data for milk flow profiles in relation to SCC represented 5 consecutive morning milkings around the time of milk sampling (sampling on d 3). A total of 661 milk samples were analyzed. At both the udder and quarter levels milk yield was reduced in groups with increased SCC. Quarters with high SCC (>500×103 cells/mL) had lower peak flow rate and longer overmilking phases compared with quarters with low SCC (<200×103 cells/mL). There was a tendency for a longer duration of the decline phase in quarters with high SCC but no effect was observed at the udder level. There were longer declines in bimodal milk flows at the quarter, but not at the udder, level. Also, quarters with bimodality had longer overmilking phases. The duration of the decline phases at the quarter level influenced all measured parameters except the duration of the increase phase. The quarters with a longer duration of the decline phase (≥80s) had greater SCC and peak flow rate but had lower milk yield compared with quarters with a shorter duration of the decline phase (<27s). Duration of the overmilking phase influenced all measured parameters except SCC. We conclude that for good udder health, the duration of the decline phase at the quarter level should be considered for milking parameters and udder preparation before milking.

Incontinentia Lactis: Physiology and Anatomy Conducive to Milk Leakage in Dairy Cows

Incontinentia lactis is a possible predisposing factor for an elevated level of intramammary infection. The goal of the present study was to investigate possible causes of incontinentia lactis in dairy cows. Two farms that differed in breed composition, but that had similar average milk yields were studied: herd A, 28 kg/d, 31 Red Holstein cows; and herd B, 26 kg/d, 16 Brown Swiss cows. Herd A was classified into 2 groups: incontinentia lactis (ILA group) and control, whereas herd B was exclusively a control herd. Milk samples that represented foremilk and the main milk fraction were collected during 4 milking sessions. In addition, milk leakage samples from the ILA group were collected at different time intervals from 0 to 5h before milking. Measurements of the teat, milk flow, fractions of cisternal and alveolar milk, intramammary pressure, and blood oxytocin pattern also were obtained. The ILA cows did not have differences in fat content between milk leakage and cisternal milk fraction. Milk fat content, however, increased during milking in response to continuous milk ejection (1.95, 1.99, and 4.61% for milk leakage, cisternal, and main milk samples, respectively). Teat canals were 9% shorter in the ILA cows, which showed greater milk yield, peak, and average flow rates. Quarter cisternal milk yield of ILA cows tended to be greater (0.50 vs. 0.23 and 0.28kg for ILA and controls from herds A and B, respectively), whereas percentages of cistern milk and alveolar milk did not differ from controls. The greater pressure in the ILA group, both before and after manual udder stimulation (ILA: 4.0 and 6.4 kPa; control: 2.0 and 5.0 kPa, respectively), could be an important cause for the leakage. Nevertheless, the increase in IMP that occurred after udder preparation affirms that milk ejection occurred in response to the tactile teat stimulation, but not before the onset of leakage. Blood oxytocin concentration in ILA cows was low until the start of udder preparation and increased in response to the milking stimulus (reaffirming the hypothesis that milk leakage occurred in the absence of milk ejection). In conclusion, milk losses by leakage are likely due to the large amount of cisternal milk, which creates pressure and causes leakage, in the absence of milk ejection.