Kamran Rezayazdi *1 
, Hassan Mehrabani Yeganeh1, Seyed Esmaeil Ghorbi1, Parham Moslehifar1, Behin Lor Kalantari1
, Hassan Mehrabani Yeganeh1, Seyed Esmaeil Ghorbi1, Parham Moslehifar1, Behin Lor Kalantari1
1- Department of Animal Science, Faculty of Agriculture, University of Tehran, Tehran, Iran
Abstract: (938 Views)
Extended Abstract
Background: The heat caused by the metabolism of nutrients and the heat of the environment are two sources of imposing heat on livestock. Heat stress in dairy cows occurs when the imposed heat load exceeds the animal's ability to eliminate it. Heat stress in lactating cows leads to a decrease in feed consumption, a reduction in milk production and quality, especially a decrease in milk fat, a decline in reproductive performance, the occurrence of various metabolic disorders, such as acidosis, endangered health, and reduced longevity of animals in the herd. The annual increase in the intensity and duration of heat, as well as the high importance of the final price of milk production and the existence of financial incentives to produce more milk fat, necessitate finding suitable nutritional solutions, along with management solutions to deal with heat stress as a challenge lasting for years that has caused continuous and large losses to milk producers in the world and Iran. In recent years, research has investigated using additives containing medicinal plants' essential oils or effective compounds as a nutritional solution to deal with animal heat stress. This study was conducted to investigate the effect of a mix of medicinal plant essential oils, including four families of aromatic compounds (aldehydes, monoterpene hydrocarbons, monoterpenols, and phenols) as an effective additive in reducing the negative effects of heat stress, on milk production and composition in Holstein dairy cows.
Methods: In this experiment, 90 Holstein dairy cows with an average milk production of 31.8 ± 4.7 kg per day and an average lactation of 180 ± 20 days were divided into two experimental groups in a completely random design, namely 1) a control and 2) medicinal plant essential oils. The experiment comprised two phases of without treatment (initial 21 days) and treatment days (45 days). During the main experiment, 50 g of a 2% mixture of medicinal plant essential oils with calcium carbonate was provided daily to the second group. The temperature-humidity index (THI) was calculated daily. Milk production and composition, persistency of milk production, feed consumption and efficiency, rectal temperature, respiration rate, and milk somatic cells were investigated and measured. The MIXED procedure of SAS software version 9 was used for the statistical analysis.
Results: Although an increase in THI led to a decrease in milk production in both experimental groups, the slope of the decrease in milk production was higher in the control group than in the group that fed medicinal plant essential oils. The comparison results of the average slope of the lactation curve line, considered an index of the persistency of milk production, showed that the medicinal plant essential oil could significantly reduce milk production loss caused by heat stress (P < 0.01). This medicinal plant essential oils led to a significant increase (3.4% on average) in daily milk production (P < 0.05). Moreover, significant increases were observed in average daily 3.5% fat-corrected (3.5% FCM) milk production from 28.83 kg to 29.81 kg (+3.40%), the average daily 4% fat-corrected milk production (FCM 4%) from 26.66 kg to 27.58 kg (+3.45%), and energy-corrected daily milk production (ECM) from 28.91 kg to 29.86 kg (3.28%) (P < 0.05). Medicinal plant essential oils did not significantly affect daily dry matter intake and feed efficiency. It significantly reduced rectal temperature and the breathing rate by affecting vascular dilation (P < 0.05). The percentage of milk fat, the percentage and amount of milk protein, and the amount of urea nitrogen in milk were not significantly affected by medicinal plant essential oils. There was no significant difference between total solids and solids without milk fat, although these traits tended to be significant (P-values 0.07 and 0.09, respectively). The average amount of milk fat was significantly higher in the group of cows fed medicinal plant essential oils than in the control group due to a significant increase in the amount of milk production (40 g per day) (P < 0.05).The medicinal plant essential oil led to a significant decrease in the number of milk somatic cells and the score of milk somatic cells and a significant increase in the percentage of milk lactose (P < 0.05).
Conclusion: According to the experimental results, medicinal plant essential oils led to a significant decrease in the rectal temperature and respiratory rate of cows in heat stress (P < 0.05). It also significantly increased daily milk production, 3.5% fat-corrected milk production (3.5% FCM), 4% fat-corrected milk production (4% FCM), and energy-corrected milk (ECM) (P < 0.05). Medicinal plant essential oils increased the average amount of milk fat of each cow by 40 g per day (P < 0.05), with no negative effects on the percentage and amount of milk protein. Furthermore, the number of milk somatic cells significantly decreased and the percentage of milk lactose increased by feeding medicinal plant extracts (P < 0.05). According to the results of this research, adding 50 g of 2% medicinal plant essential oil mixture to the feed of Holstein dairy cows is an appropriate approach to improve the productive performance and health of dairy animals and economic production of milk, especially in hot seasons.
Background: The heat caused by the metabolism of nutrients and the heat of the environment are two sources of imposing heat on livestock. Heat stress in dairy cows occurs when the imposed heat load exceeds the animal's ability to eliminate it. Heat stress in lactating cows leads to a decrease in feed consumption, a reduction in milk production and quality, especially a decrease in milk fat, a decline in reproductive performance, the occurrence of various metabolic disorders, such as acidosis, endangered health, and reduced longevity of animals in the herd. The annual increase in the intensity and duration of heat, as well as the high importance of the final price of milk production and the existence of financial incentives to produce more milk fat, necessitate finding suitable nutritional solutions, along with management solutions to deal with heat stress as a challenge lasting for years that has caused continuous and large losses to milk producers in the world and Iran. In recent years, research has investigated using additives containing medicinal plants' essential oils or effective compounds as a nutritional solution to deal with animal heat stress. This study was conducted to investigate the effect of a mix of medicinal plant essential oils, including four families of aromatic compounds (aldehydes, monoterpene hydrocarbons, monoterpenols, and phenols) as an effective additive in reducing the negative effects of heat stress, on milk production and composition in Holstein dairy cows.
Methods: In this experiment, 90 Holstein dairy cows with an average milk production of 31.8 ± 4.7 kg per day and an average lactation of 180 ± 20 days were divided into two experimental groups in a completely random design, namely 1) a control and 2) medicinal plant essential oils. The experiment comprised two phases of without treatment (initial 21 days) and treatment days (45 days). During the main experiment, 50 g of a 2% mixture of medicinal plant essential oils with calcium carbonate was provided daily to the second group. The temperature-humidity index (THI) was calculated daily. Milk production and composition, persistency of milk production, feed consumption and efficiency, rectal temperature, respiration rate, and milk somatic cells were investigated and measured. The MIXED procedure of SAS software version 9 was used for the statistical analysis.
Results: Although an increase in THI led to a decrease in milk production in both experimental groups, the slope of the decrease in milk production was higher in the control group than in the group that fed medicinal plant essential oils. The comparison results of the average slope of the lactation curve line, considered an index of the persistency of milk production, showed that the medicinal plant essential oil could significantly reduce milk production loss caused by heat stress (P < 0.01). This medicinal plant essential oils led to a significant increase (3.4% on average) in daily milk production (P < 0.05). Moreover, significant increases were observed in average daily 3.5% fat-corrected (3.5% FCM) milk production from 28.83 kg to 29.81 kg (+3.40%), the average daily 4% fat-corrected milk production (FCM 4%) from 26.66 kg to 27.58 kg (+3.45%), and energy-corrected daily milk production (ECM) from 28.91 kg to 29.86 kg (3.28%) (P < 0.05). Medicinal plant essential oils did not significantly affect daily dry matter intake and feed efficiency. It significantly reduced rectal temperature and the breathing rate by affecting vascular dilation (P < 0.05). The percentage of milk fat, the percentage and amount of milk protein, and the amount of urea nitrogen in milk were not significantly affected by medicinal plant essential oils. There was no significant difference between total solids and solids without milk fat, although these traits tended to be significant (P-values 0.07 and 0.09, respectively). The average amount of milk fat was significantly higher in the group of cows fed medicinal plant essential oils than in the control group due to a significant increase in the amount of milk production (40 g per day) (P < 0.05).The medicinal plant essential oil led to a significant decrease in the number of milk somatic cells and the score of milk somatic cells and a significant increase in the percentage of milk lactose (P < 0.05).
Conclusion: According to the experimental results, medicinal plant essential oils led to a significant decrease in the rectal temperature and respiratory rate of cows in heat stress (P < 0.05). It also significantly increased daily milk production, 3.5% fat-corrected milk production (3.5% FCM), 4% fat-corrected milk production (4% FCM), and energy-corrected milk (ECM) (P < 0.05). Medicinal plant essential oils increased the average amount of milk fat of each cow by 40 g per day (P < 0.05), with no negative effects on the percentage and amount of milk protein. Furthermore, the number of milk somatic cells significantly decreased and the percentage of milk lactose increased by feeding medicinal plant extracts (P < 0.05). According to the results of this research, adding 50 g of 2% medicinal plant essential oil mixture to the feed of Holstein dairy cows is an appropriate approach to improve the productive performance and health of dairy animals and economic production of milk, especially in hot seasons.
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