Negative effect on the productive performance of future generations
A recent study examined the productive performance and profitability of two future generations of cows born from mothers exposed to heat stress during pregnancy.
The results show that maternal hyperthermia during late gestation alters the performance of daughters for multiple lactations.
As is well known, heat stress has a significant effect on dairy cows and a negative impact on milk production, reproductive performance, herd health, and increases involuntary culling. In the United States, this amounts to losses of approximately 1.5 billion dollars per year.
According to a study conducted in the United States, the impact of heat stress is long-lasting and continues to affect the performance of the offspring of a heat-stressed cow for 2 generations.
It has already been shown that cows born from heat-stressed dams during the late phase of pregnancy have lower growth and produce an average of 5 kg less milk per day during the first lactation.
Heat stress and a summer plan: download the magazine
Although it took its time this year, the hot season has arrived, bringing with it all the heat stress issues that can affect the herd.
On time, the Tecnozoo magazine dedicated to the summer period arrives, where you can discover the best management strategies against the heat.
In addition to this article, in this issue you will find:
Uterine Health During Summer Periods: assessing the incidence of metritis and endometritis (Research presented at ADSA July 2019. (ADSA Abstract # 403)).
Heifer Management: protocol for optimally managing the summer period.
Production and reproductive performance of the 2 studied generations
There were two objectives of the study conducted by Laporta et al., 2020:
1) To measure the carryover effect of maternal exposure to heat stress during the late gestation period on: milk production, reproductive performance, and survival rates of daughters and granddaughters.
2) To estimate the economic losses associated with these outcomes in the United States.
Over a 10-year period, data were collected on the performance of Holstein cows in Florida, the U.S. state with the highest number of heat stress days per year. Information was gathered on longevity, productivity, and reproductive performance of 2 successive generations of cows born from mothers exposed to heat stress during pregnancy, and those born from mothers cooled during the summer.
The cows in Figure 1 are divided by parity; CL animals are daughters born from mothers cooled during the late stage of pregnancy (~46 days) under heat stress (shade, fans, and misters), while HT animals are those born from cows that had only shade. All cows were cooled during the three lactations. As shown, the production loss is evident in all three lactations.
Daughters of cooled cows produced +2.2 kg/cow/day more in the first lactation (31.4 vs 29.2); +3.3 kg/cow/day more in the second lactation (36.7 vs 34.4); and +6.5 kg/cow/day more in the third lactation (39.6 vs 33.1). The persistence of production in the granddaughters (Figure 2) was also somewhat compromised, with a more pronounced decrease in milk production for those not cooled. In a typical U.S. dairy farm with daughters (35% first lactation, 20% second lactation, and 14% third lactation) born from cows with heat stress during late gestation, there is a loss of 120 kg of milk per lactation.
Daughters and granddaughters of cows under heat stress showed negative effects on: survival rate (Figure 3) from birth to first calving, productive life span, milk production and its components, during the 3 lactations.
These effects translated into a considerable increase in costs for dairy producers, with national losses up to 595 million dollars per year.
This confirms the need to effectively manage heat stress even in dry cows.
According to Laporta (Department of Animal Sciences – University of Florida), this research suggests the presence of a permanent effect of the fetus/environment interaction on gene expression in adulthood.
