نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم دامی، دانشکده کشاورزی، دانشگاه زابل، زابل، ایران
2 گروه علوم دامی، دانشکده کشاورزی، دانشگاه تربیت مدرس، تهران، ایران
3 مرکز اصلاح نژاد دام و بهبود تولیدات دامی کشور، وزارت جهاد کشاورزی، کرج، ایران
4 بخش پژوهش های ژنتیک و اصلاح نژاد، موسسه تحقیقات علوم دامی کشور، کرج، ایران
5 گروه پژوهشی شترمرغ پژوهشکده دام های خاص پژوهشگاه زابل، زابل، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
The productivity of Holstein dairy cattle herds is significantly influenced by prevailing climatic conditions. Given the potential variability in climates within a single province, this study aimed to investigate the impact of different climates across the country on the productive characteristics of these herds. The study examined average milk production, fat content, protein content, fat percentage, and protein percentage, analyzing data from 325,040 heifers belonging to 270 herds for the period between 2006 and 2021. The regions of the country were classified into five distinct climates, namely BSh, BSk, BWk, Csa, and Dsa, based on the Köppen classification system, which characterizes climates by varying temperature and humidity levels. The study found that the BWk climate, characterized by cold and dry conditions, exhibited the highest milk production levels despite the unfavorable climatic conditions. This outcome can be attributed to effective herd management practices implemented in cities such as Isfahan, which fall under this climate category. The Dsa climate, characterized by a continental climate with hot and dry summers, demonstrated the third-highest milk production levels and was found to be relatively suitable for livestock rearing, particularly during seasons other than summer. Additionally, the Dsa climate was highly conducive to the growth of fodder for livestock and exhibited the best performance in terms of both the quantity and percentage of fat and protein. Despite having the lowest number of herds among the different climates, the Dsa climate outperformed the other climates in terms of production traits. Moreover, in the period from 2007 to 2021, when increasing economic problems, such as the increase in inflation and currency rates, as well as the removal of livestock input subsidies, made it difficult for livestock farmers to cover the costs of providing animal feed, all regions except Dsa region experienced a decrease in the number of herds. From the findings of this research, it can be concluded that the climatic effect in terms of heat stress for livestock and in terms of the suitability of weather conditions for planting fodder and providing livestock feed can have a decisive effect on the productive traits of livestock.
کلیدواژه‌ها [English]
Extended Abstract
Introduction
The dairy cattle industry in Iran needs to develop and adapt breeding programs according to different climates because of the country's diverse weather conditions. The dominant breed in Iran's dairy industry is the Holstein dairy cattle. However, the Holstein breed is negatively impacted by heat stress, affecting its productivity. The management and organizational structure of each province have minimal influence on the variations in the quality of selected dairy cattle herds across the country. Nevertheless, climatic diversity significantly affects the performance of herds in most Iranian provinces. Several methods for climate classification have been proposed, with the Köppen climate classification being the most well-known. Hence, the objective of this study is to examine the production trends of key traits (milk yield, fat content and percentage, and protein content and percentage) and demographic changes in selected Holstein cattle herds throughout the country.
Material and Methods
The study examined the production traits of 325,040 Holstein cows during their first calving cycle across 270 herds with consistent and regular record-keeping. The researchers compared the average production traits among different climates using a statistical model that accounted for climate effects. Tukey's method was utilized to compare the differences between the averages. The data analysis was conducted using Minitab software. The climates were classified using the widely used Köppen classification method, which categorizes climates into five major groups. The researchers utilized climate data from the Climate Data database (https://en.climate-data.org/) to determine the specific climate classification for each dairy farm based on its geographical location.
Results and discussion
The declining trend of milk production in recent years is evident. The average record of milk production in selected herds of the country was recorded higher than 9 tons only in 2018. The decreasing trend of the average milk production in recent years can have several factors, one of these factors is the changes in the number of active herds and the size of flowers every year. Reducing the size of the herd due to the removal of surplus cows is also effective on the country's meat production, and by comparing the amount of milk production, the amount of beef production and the number of active herds, it is possible to investigate the reasons for the decrease in the size of the country's Holstein cattle population. The decrease in protein in 2018 was accompanied by a decrease in the amount of milk, as a result of which the percentage did not change. In 1399 to 1400, average milk production increased (Figure 1), but protein did not increase with the same ratio. The highest average milk production of Holstein cows recorded in 270 herds across Iran is related to BWk climate, which is significantly different from other climates. BSh is in the next place and BSk and Dsa climates are in the third place jointly. The lowest average also corresponds to the Csa climate, which is significantly different from the rest of the climates, which can confirm that high temperatures reduce the performance of Holstein cows.
Conclusion
According to the results of this article, it was observed that among the examined climates, BWk climate has the highest average milk production. This region includes the cities of Isfahan and Khorasan provinces, which have the best management of dairy cows in the country. However, in the amount and percentage of milk fat and protein, Dsa climate performed the best. Also, in difficult conditions when other climates have had a sharp decrease in the number of herds, the Dsa climate has maintained its stability, despite having the lowest number of herds among the climates. Considering that the level of herd management in this climate is not comparable with a climate like BWk, this performance can be attributed to the optimal weather conditions in this climate. Considering the obtained results, it can be concluded that climatic conditions can be a determining factor in the productive performance of Holstein dairy cattle herds. Of course, it should be mentioned that in order to develop the dairy cattle industry and increase the profitability of herds, in addition to environmental factors such as the weather conditions of the region and climate, attention should also be paid to the points of providing food and water resources, breeding technology, thermal management, and providing health care (Erickson and Kalscheur, 2020). For example, despite the desert climate, Isfahan is one of the hubs for breeding dairy cows, especially Holsteins, in Iran due to proper management (Ashrafi et al., 2021). By improving knowledge and technology in this industry and using suitable breeds for each climate, it is possible to facilitate and improve the development of dairy cattle industry in Iran in different climates.
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