Analysis of the influence of variation factors on electrical conductivity of milk in Murciano-Granadina goats

Infrared Thermography as a Diagnostic Tool for the Assessment of Mastitis in Dairy Ruminants

Among the health issues of major concern in dairy ruminants, mastitis stands out as being associated with considerable losses in productivity and compromised animal health and welfare. Currently, the available methods for the early detection of mastitis are either inaccurate, requiring further validation, or expensive and labor intensive. Moreover, most of them cannot be applied at the point of care. Infrared thermography (IRT) is a rapid, non-invasive technology that can be used in situ to measure udder temperature and identify variations and inconsistencies thereof, serving as a benchmarking tool for the assessment of udders' physiological and/or health status. Despite the numerous applications in livestock farming, IRT is still underexploited due to the lack of standardized operation procedures and significant gaps regarding the optimum settings of the thermal cameras, which are currently exploited on a case-specific basis. Therefore, the objective of this review paper was twofold: first, to provide the state of knowledge on the applications of IRT for the assessment of udder health status in dairy ruminants, and second, to summarize and discuss the major strengths and weaknesses of IRT application at the point of care, as well as future challenges and opportunities of its extensive adoption for the diagnosis of udder health status and control of mastitis at the animal and herd levels.

A new decontamination method for Bacillus subtilisin pasteurized milk: Thermosonication treatment

Thermosonication (TS) is a novel and viable technique employed to replace conventional thermal processing. TS treatment combined with pasteurization was used to kill the residual heat-resistant Bacillus in pasteurized milk and extend the shelf life of pasteurized milk and compared with High Temperture Shoort Time (HTST) pasteurization to study its decontamination effect on Bacillus subtilis and the quality of treated milk. The results showed that after 40 kHz, 240 W, 25 min ultrasonic treatment and 50 °C heating decontamination treatment, the number of B. subtilis in the medium and milk medium decreased by 4.17 log CFU/mL and 4.09 log CFU/mL respectively. The results of cell membrane permeability showed that the leakage of DNA and protein in the HTST-TS group increased by 52.3 % and 34 %, respectively, when compared to that in the HTST group. In addition, transmission electron microscopy (TEM) analysis showed that the bacterial cell membrane of the HTST-TS group swelled up, the cell wall was ruptured, and the cell content was accumulated in the cells. The results showed that HTST-TS treatment significantly inhibited the activities of ATPase (47 %), succinate dehydrogenase (SDH) (68.6 %), and malate dehydrogenase (MDH) (54.4 %). The physical and chemical sensory evaluation of milk treated with HTST-TS showed that HTST-TS treatment could improve the L* value (2.24 %), zeta potential (64.19 %), and colloidal particle size (14.49 %) of milk but had no significant effect on oral sensitivity. In conclusion, this study provides new insights, which may be helpful in implementing this new combined decontamination method in the dairy industry to improve the quality of pasteurized milk and extend the its shelf life.

Relationship among Milk Conductivity, Production Traits, and Somatic Cell Score in the Italian Mediterranean Buffalo

The measurement of milk electrical conductivity (EC) is a relatively simple and inexpensive technique that has been evaluated as a routine method for the diagnosis of mastitis in dairy farms. The aim of this study was to obtain further knowledge on relationships between EC, production traits and somatic cell count (SCC) in Italian Mediterranean Buffalo. The original dataset included 5411 records collected from 808 buffalo cows. Two mixed models were used to evaluate both the effect of EC on MY, PP and FP and EC at test-day, and the effect of EC on somatic cell score (SCS) by using five different parameters (EC_param), namely: EC collected at the official milk recording test day (EC_day0), EC collected 3 days before official milk recording (EC_day3), and three statistics calculated from EC collected 1, 3 and 5 days before each test-day, respectively. All effects included in the model were significant for all traits, with the only exception of the effect of EC nested within parity for FP. The relationship between EC and SCS was always positive, but of different magnitude according to the parity. The regression of EC on SCS at test-day using different EC parameters was always significant except when the regression parameter was the slope obtained from a linear regression of EC collected over the 5-day period. Moreover, in order to evaluate how well the different models fit the data, three parameters were used: the Average Information Criteria (AIC), the marginal R2 and the conditional R2. According to AIC and to both the Marginal and Conditional R2, the best results were obtained when the regression parameter was the mean EC estimated over the 5-day period.

Physicochemical, Microbiological and Technological Properties of Red Deer (Cervus elaphus) Milk during Lactation

Simple Summary

Milk from red deer is richer in fat and proteins than that of cow or other ruminants. The semi-captive breeding of this species has traditionally focused on meat, velvet or hunting purposes, but recent studies suggested that the high level of nutrients, the promising content of bioactive peptides and the better digestibility than that of milk from other species could open innovative alternatives for the dairy industry. As for other non-commercial mammalian species that are gaining technological interest for the elaboration of dairy products, it is necessary to understand the aptitude and performance of milk from red deer to be used for the production of cheese, fermented milks or other products. Our study aims to assess some chemical, physical, microbiological and technological properties of red deer milk during a lactation period of 18 weeks. The results show that milk from this species is similar to that of other ruminant species whose milk is commercialized. In addition, our results indicate the best period to industrialize the milk during lactation. To the best of our knowledge, this is the first study to explore the benefits of using red deer milk with a technological approach.

Abstract

This study describes chemical, physical, microbiological and technological characteristics of red deer milk and the effect of lactation on these parameters in order to know their potential aptitude to elaborate dairy products. During 18 weeks, milk from five hinds was monitored for composition, bacteriology, somatic cell count (SCC), physical properties and rennet coagulation. Mean values (g/100 g) for fat, protein, lactose and dry matter were 10.4, 7.1, 4.3 and 24.2, respectively, and for urea, 265 mg/100 mL. Except for lactose, a significant increase in these components was observed (p < 0.01) as lactation progressed. The average values for bacteriology and SCC were 5.3 log cfu/mL and 4.7 log cells/mL, respectively. Regarding physical properties, conductivity (mean: 2.8 ms/cm), viscosity (3.1 Cp), coordinates L* (89.9) and a* (−3.1) and milk fat globule diameter (D_4,3: 6.1 µm) increased along with lactation while density (1.038 g/mL) decreased (p < 0.01). The pH (6.7), acidity (22.9° Dornic), coordinate b* (8.4) and ethanol stability (66.6% v/v) were stable during the study period. The stage of lactation also has a significant impact on milk coagulation properties and mean curd yield was 3.29 g/10 mL. These results suggest that red deer milk could be a potential innovative source of milk for the dairy industry.

The Impact of Mastitis on the Biochemical Parameters, Oxidative and Nitrosative Stress Markers in Goat's Milk: A Review

Goat mastitis has become one of the most frequently diagnosed conditions in goat farms, with significant economic impact on the dairy industry. Inflammation of the mammary gland poses serious consequences on milk composition, with changes regarding biochemical parameters and oxidative stress markers. The aim of this paper is to present the most recent knowledge on the main biochemical changes that occur in the mastitic milk, as well as the overall effect of the oxidative and nitrosative stress on milk components, focusing on both enzymatic and nonenzymatic antioxidant markers. Mastitis in goats is responsible for a decrease in milk production, change in protein content with pronounced casein hydrolysis, and reduction in lactose concentration and milk fat. Milk enzymatic activity also undergoes changes, regarding indigenous enzymes and those involved in milk synthesis. Furthermore, during mastitis, both the electrical conductivity and the milk somatic cell count are increased. Intramammary infections are associated with a reduced milk antioxidant capacity and changes in catalase, lactoperoxidase, glutathione peroxidase or superoxide dismutase activity, as well as reduced antioxidant vitamin content. Mastitis is also correlated with an increase in the concentration of nitric oxide, nitrite, nitrate and other oxidation compounds, leading to the occurrence of nitrosative stress.

Machine milking parameters for Murciano-Granadina breed goats

In dairy ruminants, the combination of milking parameters must ensure good milking performance without harming udder conditions. Commonly, milking conditions for goats are established without having checked the admissible limits for optimal and fast milking. The aim of this study was to establish a limit combination of machine milking parameters that improves machine milking performance without altering milkability or udder status. To this end, we studied the effect of 2 combinations (42 kPa, 120 cpm, 60% vs. 44 kPa, 120 cpm, 60% in terms of kilopascals of vacuum level, cycles per minute of pulsator rate, and percentage of pulsator ratio, respectively) on milk production and composition, milk fractioning during milking, SCC, teat tissue thickness variation after milking, and the milk emission kinetics parameters throughout 1 lactation period (6 mo). The 42 and 44 kPa measured at the vacuum gauge level became average values of 37.5 and 39.3 kPa, respectively, measured at the teat sphincter level during milking. Milk flow significantly increased and total milking time decreased 25 s with the elevation of the vacuum level from 42 to 44 kPa without any adverse effect on milk fractioning at milking. However, the use of 44 kPa also showed an increase in tissue thickness above 5%, and we observed a tendency of average conductivity of milk to increase, although without any adverse effect on SCC. It seems that 44 kPa, 120 cpm, 60% is a possible limit combination of parameters to improve milking performance without altering milkability or udder conditions. We concluded that this combination can be used for milking Murciano-Granadina breed goats in conditions similar to those of this study (mid-level milking system and 1 milking/d), although further studies are necessary to verify its application in the case of 2 milkings/d.

Somatic cell count during first and second lactation in ewes

The aim of this study was to describe the frequency of distribution of ewes in SCC groups on the basis SCS (somatic cells score) per lactation and estimate changes of SCC from 1st lactation on 2nd lactation. The experiment was carried at seven farms in 1st observed period (2016 and 2017) and at eight farms in 2nd observed one (2017 and 2018). Within each of periods the same animals were sampled on their 1st and following 2nd lactation in next year of study, only. Totally 1199 milk samples from 159 ewes and 1653 milk samples from 219 ewes were collected during 1st period and 2nd period, respectively. Milk sampling were taken monthly from April to August in both periods. For evaluation only ewes with minimum three sampling per year (minimum six samples per animal) were included in the study within both periods. The ewes were divided into the five SCC groups on basis of their SCS per lactation: G1 = SCC <200 × 103 cells.mL-1, G2 = SCC ≥200 <400 × 103 cells.mL-1, G3 = SCC ≥400 <600 × 103 cells.mL-1, G4 = SCC ≥600 <1000 × 103 cells.mL-1 and G5 = SCC ≥1000 × 103 cells.mL-1. In total statistically significant impact of parity on SCC in 2nd period was detected (p <0.0001) only. From the farm point of view in 1st period only in two farms and in 2nd one in five farms significant effect of parity was found out. Thus in some farms no increase of SCC from first to second lactation was observed. When comparing the changes in SCC from the first to the second lactation in both first and second periods, 6.92% and 10.96%, respectively ewes moved from SCC group G1 to G5. The significant effect of farm management and parity on SCC was demonstrated.

Effect of the pulsation type (alternate or simultaneous) on milk yield and health status of the mammary gland of Murciano-Granadina goats

Recent research into how the pulsation type affects goat milking concluded that alternate pulsation (AP) and simultaneous pulsation (SP) similarly affect the milking efficiency (milking duration and milking fractioning) and teat end condition after milking when both pulsations are employed in short-term experiments. However, the use of SP in high pipeline milking machines led to higher vacuum fluctuations, which, in the long term, may entail a potential risk factor for the mammary gland health status. The aim of this work was to study how AP and SP affect the milk yield, mammary gland health status, and milk composition of goats in the long term, during a complete lactation period, in a high pipeline milking machine. With this objective, 100 Murciano-Granadina goats with similar parturition dates (4 ± 1 postpartum weeks) were divided into 2 similar groups (50 goats per group) according their parity, milk yield, mammary gland health status, and milking duration (after a 15-d pre-experimental period). Throughout the experimental period (7 mo), one group was milked using SP and the other group using AP. Every month, samplings were carried out of the variables related to sanitary status of the mammary gland, milk fractioning, milking duration, average and maximum milk flows, milk composition, teat end status, vacuum fluctuations at the short milk tube during milking, and pulsation tests. Results showed that the use of SP in a high pipeline milking machine showed higher vacuum fluctuations without involving any difference in the other variables studied. We concluded that the use of AP in the milking of Murciano-Granadina goats offers little improvement of the milking performance and increases the investment required for installation and maintenance of the milking machines.

Relationship of mammary gland health status and other noninfectious factors with electrical conductivity of milk in Manchega ewes

Measuring the electrical conductivity (EC) of milk during milking has been extensively studied in cattle as a low-cost mastitis detection method that can be easily automated. The aim of this work was to study the effect of the health status of the glands and several noninfectious factors (lactation stage, milking session, and lactation number) that affect the use of EC measurement of milk to detect mastitis in dairy sheep livestock. Likewise, we studied the relation between EC and milk composition (macrocomposition and mineral content) and between EC and somatic cell count (SCC). Finally, we evaluated the use of EC thresholds as a mastitis detection method. To this end, we monitored the glandular milk EC throughout 2 consecutive lactations, during which 42 and 40 ewes were controlled, respectively. We carried out 7 biweekly checks, analyzing the EC, SCC, composition, and mineral content of glandular milk at morning and evening milkings. Before the morning milking, samples were aseptically collected for bacteriological analysis, and the results along with the SCC were used to classify the glands according to their sanitary status (healthy, latently infected, or infected). Lactation stage, parity, milking (morning or evening), health status, and the interactions of parity with health status, lactation stage with health status, and parity with lactation stage all had a significant effect on SCC and EC of the milk. The correlation between EC and SCC was only significant when all the data were analyzed jointly (r = 0.33) and for SCC ≥ 600.000 cells/mL (r = 0.25). The changes in milk composition, mainly in fat content, largely explained the variation in EC (R² = 0.69). For the same EC threshold, the specificity and sensitivity varied depending on the parity or the milking, with the negative predictive value obtained being higher than the positive predictive value at all times. We concluded that developing methods of detecting mastitis in sheep by milk EC readings would require consideration of noninfectious factors that also affect the gauging of EC. One option to consider would be individualized daily monitoring of the glands, as demonstrated in other species such as cattle and goat.

Improved Fuzzy Logic System to Evaluate Milk Electrical Conductivity Signals from On-Line Sensors to Monitor Dairy Goat Mastitis

The aim of this study was to develop and test a new fuzzy logic model for monitoring the udder health status (HS) of goats. The model evaluated, as input variables, the milk electrical conductivity (EC) signal, acquired on-line for each gland by a dedicated sensor, the bandwidth length and the frequency and amplitude of the first main peak of the Fourier frequency spectrum of the recorded milk EC signal. Two foremilk gland samples were collected from eight Saanen goats for six months at morning milking (lactation stages (LS): 0–60 Days In Milking (DIM); 61–120 DIM; 121–180 DIM), for a total of 5592 samples. Bacteriological analyses and somatic cell counts (SCC) were used to define the HS of the glands. With negative bacteriological analyses and SCC < 1,000,000 cells/mL, glands were classified as healthy. When bacteriological analyses were positive or showed a SCC > 1,000,000 cells/mL, glands were classified as not healthy (NH). For each EC signal, an estimated EC value was calculated and a relative deviation was obtained. Furthermore, the Fourier frequency spectrum was evaluated and bandwidth length, frequency and amplitude of the first main peak were identified. Before using these indexes as input variables of the fuzzy logic model a linear mixed-effects model was developed to evaluate the acquired data considering the HS, LS and LS × HS as explanatory variables. Results showed that performance of a fuzzy logic model, in the monitoring of mammary gland HS, could be improved by the use of EC indexes derived from the Fourier frequency spectra of gland milk EC signals recorded by on-line EC sensors.

Evaluation of the Fourier Frequency Spectrum Peaks of Milk Electrical Conductivity Signals as Indexes to Monitor the Dairy Goats' Health Status by On-Line Sensors

The aim of this study is a further characterization of the electrical conductivity (EC) signal of goat milk, acquired on-line by EC sensors, to identify new indexes representative of the EC variations that can be observed during milking, when considering not healthy (NH) glands. Two foremilk gland samples from 42 Saanen goats, were collected for three consecutive weeks and for three different lactation stages (LS: 0–60 Days In Milking (DIM); 61–120 DIM; 121–180 DIM), for a total amount of 1512 samples. Bacteriological analyses and somatic cells counts (SCC) were used to define the health status of the glands. With negative bacteriological analyses and SCC < 1,000,000 cells/mL, glands were classified as healthy. When bacteriological analyses were positive or showed a SCC > 1,000,000 cells/mL, glands were classified as NH. For each milk EC signal, acquired on-line and for each gland considered, the Fourier frequency spectrum of the signal was calculated and three representative frequency peaks were identified. To evaluate data acquired a MIXED procedure was used considering the HS, LS and LS × HS as explanatory variables in the statistical model.Results showed that the studied frequency peaks had a significant relationship with the gland’s health status. Results also explained how the milk EC signals’ pattern change in case of NH glands. In fact, it is characterized by slower fluctuations (due to the lower frequencies of the peaks) and by an irregular trend (due to the higher amplitudes of all the main frequency peaks). Therefore, these frequency peaks could be used as new indexes to improve the performances of algorithms based on multivariate models which evaluate the health status of dairy goats through the use of gland milk EC sensors.

Within-day variation and effect of acute stress on plasma and milk cortisol in lactating goats

An experiment was carried out to study the effect of acute stress on cortisol concentration in goat milk (milk cortisol; MC) and its suitability for stress assessment. Additional variables studied were plasma cortisol (PC), blood glucose (BG), and somatic cell count (SCC). Ten goats free of mastitis at 2 mo of lactation were divided into 2 groups. One group of animals was exposed to acute stress (visual and auditory, but not physical, contact with a barking dog for 3 min) immediately before the 1000 h sampling (STR), and the other group was considered as the control group, not exposed to acute stress (CON). The animals were gradually accustomed to the sampling schedule for 1 wk before the stress treatment (pre-experimental period). The variables PC, MC, BG, SCC, and milk composition (fat, lactose, whey protein, true protein, and casein) were recorded at 0600, 1000, 1130, 1400, 1800, 2200, and 0200 h. Milk variables were recorded in both glands separately. The right gland (n=10) was completely milked and the left gland (n=10) was milked to 30 mL at every sampling except at 1000 h, when complete milking was carried out on both glands. Variables were analyzed by using a linear mixed model. Both PC and MC concentrations varied throughout the day, with values being highest in the morning. Higher PC levels were recorded in the STR group immediately after treatment compared with CON (36.9 vs 16.3 ng/mL). For MC, differences between treatments were noted 1.5h after STR treatment (1.27 vs 0.25 ng/mL). Blood glucose increased immediately after treatment in STR animals, being different from CON until 1.5h after treatment sampling (101 vs. 58 mg/dL). The SCC was not increased by STR treatment, showing higher values in the morning and afternoon compared with evening and night (5.6±0.13 to 5.87±0.13 log10 SCC). The STR treatment had no significant effect on milk composition, and overall milk yield of a complete day after stress stimulus of both groups was similar (STR: 2,067±280 g/d; CON: 2,134±427 g/d). We conclude that plasma and milk cortisol concentrations in control dairy goats varied throughout the day; MC showed significant differences in the STR group if samples were taken 1.5h after the stressing stimulus, whereas PC showed significant differences in samples taken immediately after the stressing stimulus. Additionally, MC sampling has the advantage of being noninvasive compared with blood sampling.

Effect of intramammary infection on milk electrical conductivity in Murciano-Granadina goats

Measurements of electrical conductivity (EC) of milk are used in mastitis detection in cows due to the low cost, possibility of automation, and rapid diagnosis, but the literature about EC measurement in goats is scarce. In this study, we studied the effect of the establishment of intramammary infection (IMI) on EC of goat milk by gland using daily measurements. Additionally, the effects on milk yield, somatic cell count (SCC), and mineral content were analyzed. Eight primiparous and 10 multiparous Murciano-Granadina goats free from IMI were included in the study. Health conditions of the participating animals were monitored for 16 d and then various unfavorable health situations that may arise on commercial farms were simulated to increase the chances of IMI. Once the IMI was confirmed, the experiment continued for another 16 d. Statistical analysis was conducted using a linear mixed model considering several periods regarding the establishment of the infection and whether it affected one or both glands in the animal. The establishment of IMI caused a significant increase of EC, SCC, and chlorides in the infected glands, whereas the sodium:potassium ratio and the ratio of EC between collateral glands showed significant increases only in bilaterally infected animals. The microorganisms that caused greater increases of EC were Staphylococcus aureus and a gram-negative bacterium. Changes due to other isolated microorganisms (coagulase-negative staphylococci and streptococci) were small. No significant differences in milk yield were determined. The significant effect of infection on EC in the affected glands suggests that the use of a system based on daily readings of EC could be useful in IMI detection of goats.

Evaluation of commercial probes for on-line electrical conductivity measurements during goat gland milking process

The measurement of the milk electrical conductivity (EC) during mechanical milking has been widely studied for mastitis detection on cows because its improving of welfare and animal health, although research about small ruminants is scarce. The aim of this study was to evaluate the performance of three commercial conductimeters to be used during mechanical milking of small ruminant halves, especially Murciano-Granadina goats. The objective of this research was to integrate the probes on the milking unit and to check the suitability of the probe selected. The results presented in this research have guided authors to discard the commercial probes and to establish the requirements of a new probe design that is briefly outlined in the conclusions of this contribution.