The present study aims to examine the relationships between temperature and humidity and milk composition, microbial load, and somatic cells in the milk of Holstein dairy cows. For this purpose, the temperature–humidity index, ambient temperature, and relative humidity data were obtained from the nearest weather stations. Production data were obtained from four dairy farms in Golestan province, Iran, collected from 2016 to 2021. The traits investigated were protein, fat, solids-not-fat (SNF), microbial load, and somatic cell count (SCC) in milk. The effects of the environmental temperature, humidity, month, and season on the milk composition, microbial load, and somatic cells were analyzed through analysis of variance. The effects of environmental temperature, humidity, month, and season on the milk composition, microbial load, and somatic cell composition were analyzed using a mixed procedure with a restricted maximum likelihood model. Although our findings revealed that there were significant differences in fat, protein, SNF, and SCC among the different months of the year (p < 0.01), no significant difference was observed in the total microbial count in milk. Environmental temperature presented significant impacts on fat, protein, SNF, SCC, and total microbial count within various temperature ranges (p < 0.01). When the temperature increased from 6.2 °C to 31.3 °C, the milk protein, fat, SNF, and somatic cell count significantly decreased, by approximately 4.09%, 5.75%, 1.31%, and 16.8%, respectively; meanwhile, the microbial count in milk significantly increased, by approximately 13.7%. Humidity showed an influence on fat, protein, non-fat solids, somatic cells, and total microbial count within different temperature ranges (p < 0.01). When the humidity increased from 54% to 82%, the milk protein, fat, SNF, and SCC significantly increased, by approximately 3.61%, 4.84%, 1.06%, and 10.2%, respectively; meanwhile, the microbial count in milk significantly decreased, by approximately 16.3%. The results demonstrate that there is a negative correlation between different months of the year, temperature, and the humidity of the environment, in terms of milk components and SCC. Our findings demonstrate that the optimum performance, in terms of milk composition, occurred in the first quarter of the year. As temperature increases and humidity decreases, milk quality decreases. Therefore, the adverse effects of environmental conditions on agricultural profits are not negligible, and strategies to better deal with the negative environmental effects are needed in order to improve milk quality in dairy cows.

This current study addresses the knowledge gap regarding the influence of seasons, months, and THI on milk yield, composition, somatic cell counts (SCC), and total bacterial counts (TBC) of dairy farms in northeastern regions of Iran. For this purpose, ten dairy herds were randomly chosen, and daily milk production records were obtained. Milk samples were systematically collected from individual herds upon delivery to the dairy processing facility for subsequent analysis, including fat, protein, solids-not-fat (SNF), pH, SCC, and TBC. The effects of seasons, months, and THI on milk yield, composition, SCC, and TBC were assessed using an analysis of variance. To account for these effects, a mixed-effects model was utilized with a restricted maximum likelihood approach, treating month and THI as fixed factors. Our investigation revealed noteworthy correlations between key milk parameters and seasonal, monthly, and THI variations. Winter showed the highest milk yield, fat, protein, SNF, and pH (p < 0.01), whereas both SCC and TBC reached their lowest values in winter (p < 0.01). The highest values for milk yield, fat, and pH were recorded in January (p < 0.01), while the highest protein and SNF levels were observed in March (p < 0.01). December marked the lowest SCC and TBC values (p < 0.01). Across the THI spectrum, spanning from −3.6 to 37.7, distinct trends were evident. Quadratic regression models accounted for 34.59%, 21.33%, 4.78%, 20.22%, 1.34%, 15.42%, and 13.16% of the variance in milk yield, fat, protein, SNF, pH, SCC, and TBC, respectively. In conclusion, our findings underscore the significant impact of THI on milk production, composition, SCC, and TBC, offering valuable insights for dairy management strategies. In the face of persistent challenges posed by climate change, these results provide crucial guidance for enhancing production efficiency and upholding milk quality standards.

This study was conducted to investigate the effect of milk supplemented with organic iron on performance, blood hematology, iron metabolism parameters, biochemical and immunological parameters in suckling lambs. Thirty-six newborn Dalagh lambs were randomly divided into three groups with 12 replications. The control group was fed with milk without organic iron. The other two groups were fed milk supplemented with 25 and 50 mg/d organic iron, respectively. During the experiment, increased daily weight gain and total body weight were observed in the iron-supplemented groups. An increase in the levels of red blood cell, hemoglobin, hematocrit, mean corpuscular hemoglobin, and mean corpuscular concentration in iron supplemented groups was indicated. Consumption of organic iron caused a significant decrease in plasma copper concentration. Total antioxidant status level was lower, but levels of glutathione peroxidase, superoxide dismutase, and catalase were higher in iron supplemented groups. In organic iron supplemented groups, insulin and thyroid hormones levels were significantly increased, and glucose level was significantly decreased. In organic iron supplemented groups, alkaline phosphatase level significantly increased, and aminotransferase level significantly decreased. Overall, the use of organic iron in the milk improved the performance and health in suckling lambs, and since a lower level of supplementation is naturally preferable, supplementation of milk with 25 mg/d organic iron is recommended.

The livestock industry significantly contributes to greenhouse gas emissions, with ruminant animals, including cows, sheep, and goats, being responsible for a substantial share of these emissions due to methane production. Reducing methane emissions from ruminants is crucial for mitigating the environmental impact of livestock production. Additionally, there has been a growing interest in improving the nutritional quality of ruminant products through modifying their profile of fatty acids. The current study aimed to investigate the potential of sage (SAG), pine (PIN), and clove (CLO) essential oils as natural additives for modulating in vitro ruminal fermentation characteristics and biohydrogenation of polyunsaturated fatty acids (PUFA). Within the current experiment, three dose levels (300, 600, and 900 mg/L) of essential oils were evaluated using rumen inoculum from three mature Dalagh ewes (58 ± 2.84 kg body weight). The results revealed that the essential oils had a significant impact on gas production, methane and carbon dioxide production, ruminal fermentation parameters, and ruminal biohydrogenation of dietary PUFAs. The essential oil treatments resulted in reduced gas production compared with the control group. Methane production was significantly reduced by all doses of the essential oils, with the highest dose of CLO resulting in the lowest methane production. In addition, the essential oils affected ruminal fermentation parameters, including pH, ammonia concentration, and production of total volatile fatty acids. Promising modifications in ruminal biohydrogenation of PUFAs and the profile of fatty acids were also observed in the current study. These findings suggest that SAG, Pin, and CLO hold promise in mitigating methane emissions and improve the nutritional value of ruminant products. Further investigation is required to evaluate their effectiveness in practical feeding strategies for livestock.