Exploitation of multiple approaches to adapt and mitigate the negative effects of heat stress on milk production and fertility of friesian cows under field conditions

الملخص AR

This study was designed to assess impact of heat stress on performance of low producing Friesian cows and implement adaptive herd management including multiple approaches for alleviate these impacts.

The Temperature Humidity Index (THI) and physiological parameters (cow’s rectal temperature ‘RT’ and respiration rate ‘RR’) were used as indicators of heat stress.

Daily averages of microclimatic factors in district were recorded; milk production data were recorded throughout study period.

Postpartum cyclicity and reproductive parameters were estimated.

Finally, a field trial based on multiple approaches to mitigate impacts of heat stress was planned and implemented.

Results, mTHI>78 significantly (P<0.0001) increased RR and RT and decreased average daily milk/cow (P <0.0001).

Moreover, mTHI>78 was associated with significantly lower cyclicity by 60 days postpartum, cyclic high progesterone (P4) and first insemination conception, compared to mTHI<72.

Interestingly, serum P4 levels five days post insemination were negatively correlated (r = -0.88, P<0.0001) with mTHI.

Furthermore, mTHI>78 significantly (P<0.001) increased days to first estrus and days to conception (days open).

Also, cows exposed to mTHI<72 and 72-78 acquired significantly (P<0.01) fewer inseminations per conception, as compared to cows exposed to mTHI>78.

The field trial implemented decreased cows’ physiological parameters, increased their milk and increased serum P4 concentrations of pregnant cows Subjected to adaptive measures.

Conclusion, heat stress negatively impacted milk production and fertility of low producing Friesian cows with significant impacts observed with mTHI above 78.

Implementation of adaptive measures led to increased milk production of adapted cows and increased serum P4 in pregnant cows.