Yaks and their crossbreds: effects of stocking density, pasture site and altitude on performance, behavior and metabolic adaptation in the Himalayan Mountains of Nepal

Abstract

Transhumant livestock herding at high altitude in the Himalayan mountains of Nepal is characterized by the seasonal movement of animals for grazing pastures situated at different altitudes. In the Kanchenjunga Conservation Area (KCA) of Nepal, the yaks (Bos grunniens) and the first generation (F1) crossbred females of yak and cattle being either (locally called) Dimjo chauries (shortly Dimjos, cattle-yak crossbreds, B. taurus × B. grunniens,) or Urang chauries (shortly Urangs, yak-cattle crossbreds, B. grunniens × B. indicus) are the major bovine genotypes kept in transhumance for milk production. In that system, they are moved towards high alpine pastures in summer and returned to low altitude mixed forest areas in winter. There are almost no scientific studies on transhumant yaks and crossbreds, and because their performance is expected to vary differently depending on seasonal herbage growth and altitude of pasture sites along the transhumance route, a project was performed where the traditional transhumant pastoral systems of the KCA of Nepal was analyzed in detail from biological and social aspects. In a first study (2010), at first, a survey was conducted in order to characterize the bovine livestock husbandry system within the Kanchenjunga Conservation Area with a major focus on transhumant production systems with yaks and their crossbreds from KCA. Information from 240 households across different altitude i.e. high (2000-4200 m) and low (1400-2000 m) and trekking routes applied from Phungling Taplejung i.e. east (crossing KCA in direction to Mt. Kanchejunga), and the west (in direction to Olangchung Gola). Data were analyzed for 192 households for some basic of livestock systems. The household mean livestock ownership and the household income contribution from the livestock sector was higher at the high altitude areas of KCA, and high for also families who live close to high altitude areas. The household income contribution of yaks and their crossbreds was higher for large number of families at high altitudes. The majority of the respondents were not concerned about the rangeland conditions but were positive about rangeland improvement. In a second study (2010), it was aimed to assess the effect of stocking density (SD) on general performance and activity pattern of Dimjos (without calves) across pasture sites of different altitudes along a common transhumant route. The two SD were four lactating Dimjos in high SD and two in low SD. This was replicated at each of five different pasture sites. The five selected pastures selected at the common route representing upward (pastures at 3200 m, 4000 m and 4500 m and downward movement (at 4000 m and 2600 m) are traditionally used by local herders. Groups of two yaks (with calves) were replicated at low SD at the three high altitude pasture sites (4000 m, 4500 m and 4000 m again). Pedometer devices were used for assessment of activity pattern. The data collection period lasted for 9 days at each pasture site and for eight consecutive days for milk and behavior data collection. The daily milk yield was higher for low SD crossbreds. The milk fat content increased across the pasture sites in Dimjos, while the protein content decreased probably mostly in to response to changing feed composition. At cost of walking, lying time increased across the pasture sites. High SD forced animals for longer walking and lying time but lowered the standing time as compared to low SD. Dimjos even at low SD were not superior to yaks in performance at pastures of above 4000 m, however produced higher milk amount when maintained at low SD as compared to high SD. In the third study (adaptation study, 2011), two crossbred genotypes, i.e. Dimjos and Urangs, and purebred yaks, with each genotypic group consisting of six multiparous lactating animals, were assessed for their ability to adapt to high altitude first at high altitude (4700 m) in August and then at medium altitude (3000 m). The experimental period was 12 days at high altitude and 14 days at medium altitude and included first 6 and 8days as adaptation and last 6 days of measurement period at each altitudinal site. Each group of genotype was observed for general performance, physiologic parameters (respiration rate, rectal temperature, heart rate and heart rate variability) and blood parameters (glucose, lactate and hemoglobin) and activity pattern at both altitudes. The Dimjos always had higher milk yield and higher milk fat content than Urangs and had a higher daily yield of important milk components than yaks and Urangs. As influenced by lactation, daily yields of milk fat and protein declined from high to medium altitude but remained highest for Dimjos. The higher milk yield of the Dimjos compared with that of the Urangs was consistent with the blood metabolic and with the physiological parameters at cost of similar activity pattern. In comparison to yaks, Dimjos were even not so well adapted than yaks at high altitude but were clearly better than Urangs as revealed from the physiologic and metabolic traits measured. Dimjos also produced highest milk yield as compared to yaks and Urangs with similar fat content as that of high altitude and maintained the body weight lost at high altitude until arrived at medium altitude. The results of the project well illustrated the importance of yaks and their crossbreds with cattle in the livelihood of the smallholder transhumant herders of the Himalayan Mountains. As an option to achieve higher milk production, Dimjo type crossbreds are the better option for increasing milk production at low SD in the restricted areas such as in Kanchenjunga Conservation Area of Nepal, where land expansion for grazing is impossible. Furthermore, Dimjos were better than Urangs concerning high altitude tolerance which was obvious from better milk yield and milk fat content, physiologic and metabolic conditions. The activity behavior of Dimjos was similar to that of yaks and Urangs but Urangs were clearly stressed as compared to yaks at high altitude. Thus, for high altitude conditions, yaks are even a better livestock genotype as compared to any of the crossbreds. With respect to the amount of consumable milk, the Dimjo type crossbreds have another advantage to yaks due to their longer lactation period and the keeping practice without calves, while almost half of milk is consumed by calves in yaks.