Non-aureus staphylococci and mammaliicocci isolated from bovine milk in Italian dairy farms: a retrospective investigation.

Non-aureus staphylococci and mammaliicocci (NASM) are associated with bovine mastitis and increased milk somatic cell count (SCC) but their relationships with mammary gland health at the species level are not clearly defined. Regional differences have also been reported in their specific prevalence. The implementation of MALDI-TOF MS in milk microbiology is generating large and dependable datasets with the potential of providing useful epidemiological information. We present the retrospective analysis of 17,213 milk samples sent to our laboratory in 2021-2022, including 13,146 quarter samples from cows with subclinical (SCM) or clinical mastitis (CM) from 104 farms, and 4,067 composite herd survey (HS) samples from 21 farms. NASM were isolated from 21.12% of SCM, 11.49% of CM, and 15.59% of HS milk samples. The three most frequently identified NASM in SCM milk were Staphylococcus chromogenes (33.33%), S. haemolyticus (26.07%), and S. epidermidis (10.65%); together with S. microti and S. hyicus, these species were significantly more prevalent in quarters with SCM (p < 0.05). The three most frequently identified NASM in CM milk were S. chromogenes (31.69%), S. haemolyticus (21.42%), and Mammaliicoccus sciuri (18.38%), although no significant associations were found between these NASM species and CM. The three most frequently identified NASM in HS milk were S. chromogenes (44.49%), S. epidermidis (17.84%), and S. haemolyticus (17.23%), with S. chromogenes being isolated in all the farms sending HS milk (100%). In conclusion, this retrospective study provides the first information on the NASM species isolated from cow milk in Italy, expanding our knowledge on the epidemiology of NASM at the species level and providing further insights into their relationships with mammary gland health in modern dairy farms.

The Potentialities of Machine Learning for Cow-Specific Milking: Automatically Setting Variables in Milking Machines.

In dairy farming, milking-related operations are time-consuming and expensive, but are also directly linked to the farm's economic profit. Therefore, reducing the duration of milking operations without harming the cows is paramount. This study aimed to test the variation in different parameters of milking operations on non-automatic milking machines to evaluate their effect on a herd and finally reduce the milking time. Two trials were set up on a dairy farm in Northern Italy to explore the influence of the pulsation ratio (60:40 vs. 65:35 pulsation ratio) and that of the detachment flow rate (600 g/min vs. 800 g/min) on milking performance, somatic cell counts, clinical mastitis, and teats score. Moreover, the innovative aspect of this study relates to the development of an optimized least-squares support vector machine (LSSVM) classification model based on the sparrow search algorithm (SSA) to predict the proper pulsation ratio and detachment flow rate for individual cows within the first two minutes of milking. The accuracy and precision of this model were 92% and 97% for shortening milking time at different pulsation ratios, and 78% and 79% for different detachment rates. The implementation of this algorithm in non-automatic milking machines could make milking operations cow-specific.

Biopreservation as a potential hurdle for Bacillus cereus growth in fresh cheese.

This study aimed to evaluate the possible inhibitory effect of natural lactic acid bacteria on the growth of 2 Bacillus cereus strains. First, we evaluated the behavior of spores of B. cereus GPe2 and D43 when inoculated before cheesemaking using pasteurized or raw milk; no statistical differences were observed between cheese produced with the 2 types of milk. Then, lactic acid bacteria (LAB) were isolated from cheese at the last sampling time, identified, and tested in vitro for their antagonistic activity and organic acid production by using an HPLC method, showing antimicrobial potential. The LAB that produced larger inhibition halos (>9 mm) against B. cereus strains (LAB 3, 6, 9, 10: Lactococcus lactis ssp. lactis; LAB 7: Lactococcus lactis ssp. cremoris) were selected to produce a LAB mixture for subsequent tests. Spores of B. cereus GPe2 and D43 were inoculated in pasteurized milk before cheesemaking with or without addition of the LAB mixture at a high dosage. Bacillus cereus grew more slowly when LAB were added to the dairy matrix (with differences from 2.36 to 2.66 log cfu/g in B. cereus GPe2 and D43 growth).

In vitro assessment of the effects of temperature on phagocytosis, reactive oxygen species production and apoptosis in bovine polymorphonuclear cells.

Heat stress exerts a direct negative effect on farm animal health, triggering physiological responses. Environmental high temperature induces immunosuppression in dairy cows, increasing the risk of mastitis and milk somatic cell counts. The influence of heat stress on leukocytes activities has not been fully elucidated. The present in vitro study was aimed at assessing whether the exposure to temperature simulating conditions of severe whole body hyperthermia affects defensive functions of bovine blood polymorphonuclear cells. Blood was collected from seven clinically healthy, multiparous, late lactating Holstein cows. After isolation, PMN were incubated at either 39 or 41°C. Phagocytosis, respiratory burst and apoptosis were then investigated. The selected temperatures of 39°C or 41°C mimicked conditions of normothermia or severe heat stress, respectively. Phagocytosis assay was carried out by measuring the fluorescence of phagocyted fluorescein-labelled E. coli bioparticles. The modulation of oxidative burst activity was studied by the cytochrome C reduction method. Apoptosis was determined by measuring the activities of two enzymes that play an effector role in the process, namely Caspase-3 and Caspase-7. Statistical analyses were performed using SPSS 22.0. A Student t-test for paired samples and a Generalised Estimating Equation were used based on data distribution. The phagocytosis rate was reduced (-37%, P<0.01) when PMN were incubated for 2h at 41°C, when compared to phagocytosis rate measured at 39°C. The oxidative burst, as determined by extracellular production of reactive oxygen species (ROS), was also reduced by the exposure of cells to 41°C compared to 39°C. Such reduction ranged between -2 and -21% (P<0.05). Apoptosis rate was not affected by different temperatures. The results reported in this study suggest that phagocytosis and ROS production in PMN exposed to severe high temperature are impaired, partially explaining the higher occurrence of infections during periods of hot weather.