Effect of Heat Stress on Dairy Cow Performance and on Expression of Protein Metabolism Genes in Mammary Cells

Hormonal alterations occurring under late gestation heat stress may disturb mammary gland remodelling, resulting in a reduced milk yield during the subsequent lactation. We investigated the effects of an altered endocrine environment on mammary gene expression at different stages of the dry period. Mammary gland biopsies from in vivo-cooled (CL) or heat-stressed (HT) cows were collected at d 3 and 35 relative to dry-off and divided into explants. Explants were incubated in vitro for 24 h in one of three media: Basal: no prolactin or estrogen; CL-mimic: Basal + low prolactin + high 17β-estradiol, or HT-mimic: Basal + high prolactin + low 17β-estradiol. Real time qPCR was used to quantify gene expression. We established that late-gestation heat stress changes the expression of prolactin and oestrogen receptors, downregulates genes involved in apoptosis, autophagy and proliferation at d 3 and upregulates genes related to those cellular processes at d 35. Moreover, compared with in vivo treatments, we showed that the expression of fewer genes was impacted by in vitro treatments which aimed to mimic the hormonal response of cows exposed to a different environment. Further research will continue to uncover the mechanisms behind the production impairments caused by late-gestation heat stress.

Section: Discussionsupporting

confidence: 93%

Endocrine Signals Altered by Heat Stress Impact Dairy Cow Mammary Cellular Processes at Different Stages of the Dry Period

Ouellet

Negrão

Skibiel

et al. 2021

“…However, in our study, milk fat increased in summer, which may have been caused by long-term HS, leading to the decomposition of long-chain fatty acids, and thus, increased milk fat. Furthermore, the higher percentage of fat in the milk of heat stressed cows could be attributed to the reduction in milk yield and subsequent concentration of fat, in addition to possibly greater non-protein nitrogen contents in the milk produced from cows under HS [ 26 ]. Several studies have shown that milk protein and lactose concentrations are higher during the first parity than the third parity [ 24 , 27 ].…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Heat Stress Effects in Different Geographical Areas on Milk and Rumen Characteristics in Holstein Dairy Cows Using Robot Milking and Rumen Sensors: A Survey in South Korea

Lee

et al. 2022

This survey investigated, using robotic milking and rumen sensors, the effects of an adjusted temperature–humidity index (THI) in different geographical areas on milk yield, fat and protein, rumen temperature, and activity in lactating Holstein cows. We additionally explored the effect of parity on milk and rumen temperature and activity under different THI levels during the summer. From January to September 2020, four farms (276 dairy cows) were subjected to the use of robot milking machines, and two farms (162 dairy cows) to the use of rumen sensors. For the temperature and humidity data, the THI was calculated on the basis of the data from the Korea Meteorological Administration (KMA). The data were analyzed using the GLM procedure of SAS. Milk yield and milk protein decreased (p < 0.05), and milk fat increased (p < 0.05) at all farms during the summer, from July to August, when the temperature and humidity were high (THI = 72–79). Milk yields were the highest in the fifth, sixth, seventh, and eighth parities, and the lowest in the fourth (p < 0.05). Milk fat concentration was the highest in the fourth parity and the lowest in the first parity (p < 0.05). In the first parity, the highest levels of milk protein and lactose were seen (5.24% and 4.90%, respectively). However, milk protein concentration was the lowest in the third parity, and the lactose concentration was the lowest in the fifth, sixth, seventh, and eighth parities. According to the rumen sensor, the rumen temperature of the dairy cows at the two farms also continued to increase (p < 0.05) from July to August, and then decreased (p < 0.05) in September. However, the activity in the rumen was increased (p < 0.05) from July to September. In the second parity, the highest rumen temperature (39.02 °C) was observed, while the lowest value (38.28 °C) was observed in the third parity. The highest value of rumen activity (12.26 mg) was observed in the second parity and the lowest value (11.31 mg) in the fourth parity. These data, taken together, confirm that a high THI during summer conditions negatively affects milk yield, milk protein content, and rumen temperature and activity in lactating Holstein cows. It is also demonstrated that various parities affect milk characteristics and the rumen environment in the summer season.

“…Only if the values of the environment are at the optimal level (usually recommended temperature within a range of −0.5 to 20.0 °C and 40–80% relative humidity), the dairy cows are in a state of well-being [ 8 , 9 , 10 , 11 ]. The results of some research studies revealed that even mild heat stress reduced the feed intake and milk yield of dairy cows [ 12 , 13 ]. The influence of temperature conditions in the hot tropical climate on milk production is very strong and causes serious problems, especially for dairy cows with high milk yield [ 14 ].…”

Section: Introductionmentioning

confidence: 99%

Influence of External Thermal Conditions on Temperature–Humidity Parameters of Indoor Air in a Czech Dairy Farm during the Summer

Kic

2022

The aim of this article is to show the relationship between external thermal conditions and the quality of the indoor environment on a dairy farm during the summer. The measurements were carried out on a large dairy farm of Holstein cattle situated in the Czech Republic. The research included the measurement of the cowshed for 440 lactating cows, a milking parlor, a maternity cowshed, a cowshed for dry cows, 69 individual calf hutches, and three outdoor group shelters for calves. The results of the registration measurements of the thermal state parameters outside and inside the buildings were analyzed. The critical and dangerous situations were especially regarding the calves. The highest temperature in the calf hutches was 48 °C with the value of THImax = 90.1, while in the calf group shelters it was 46.9 °C with the value of THImax = 89.4. The research results showed that not only the critical values of temperature and the temperature–humidity index that affect the housed animals are important but also the duration for which the animals are exposed to heat stress. The massive masonry constructions of the milking parlor and also of the cowshed for dry cows dampened the temperature rise in these barns, with good values for the attenuation coefficient.