Meat production

Meat from yak is derived from surplus males, often the castrated steers, and also from females, usually at the end of their useful reproductive life, or at the end of their time as milk-producers. In "efficiency" terms (meat output/feed input), the process of meat production in the yak cannot be regarded as "efficient" because, for the most part, the animals are not slaughtered until quite late in life after several cycles of weight gain and weight loss. Meat from the yak represents an important source of sustenance for the herders and their families and an additional source of income from sales. Also, there are circumstances when meat production from yak should be regarded as an efficient use of resources, at high altitudes, that might otherwise not be utilized at all. In this sense, Smirnov et al. (1990) pointed out that in a part of the Caucasus, the cost of a unit increase in live weight was ten times greater for beef cattle than for yak. (Yak in the Caucasus fatten on summer pastures at elevations of 3 500 - 4 000 m). In fact, it is claimed that the annual expenditure on keeping a yak was marginally less than that on a sheep. Similar claims of the "efficiency" of yak for meat production are made in other countries and referred to in Chapter 11, part 2.

Meat quantity

The major factor contributing to meat output is the body weight of the animal at the time of slaughter. Thus, the factors associated with variation in growth, discussed earlier in this chapter, all influence the amount of meat produced. Grass growth, as affected by season and location, is the major contributor, along with breed, age and sex of the animal. Seasonal changes in body weight, shown earlier in this chapter, clearly affect meat output. In practice, animals intended for meat are slaughtered, whenever possible, only in the autumn when they are in good, fat condition. Just as July-August are termed by herdsmen concerned with milk as the "golden age", local people regard October as the month of "best fatness" for meat production (in Tibet this is considered to be in September [Ma Zongxiang and Dou Yaozong, 1982]).

Breed and location

There is much variation in the meat properties of different breeds of yak at different locations (as noted earlier, these factors are generally confounded). Meat output in terms of dressing percentage, ratios of lean to bone and loin-eye area are thought to be better from Alpine - than from Plateau-type yak - though this impression may be derived largely from the superiority of the Jiulong breed in Sichuan province. Table 6.22 gives some of the results.

Live weights at slaughter varied with breed and location (and age at slaughter) from 116 - 576 kg. Dressing percentages ranged from 40 - 62 percent. In at least one case (Smirnov et al. 1990), the low dressing percentage was attributed to the slaughter of young male yak at what was considered the wrong age - two years old. There was also substantial variation in loin eye area. It should be noted, however, that in some instances the numbers on which the means are based are very small. Most of the information should be regarded as indicative of the range of values found in yak rather than definitive of the merits of any particular class or location of yak.

The question of stage of maturity at time of slaughter is clearly important (some of this information may be available in the source references shown in Table 6.22), but the main criterion for timing the slaughter of yak is usually to leave it to the end of the grass-growing season when the condition of the animals is at its best.

As referred to in Chapter 3, there is interest in the potential benefits of crossing domestic yak with wild yak (by the use of A.I.). Evidence, though not fully consistent across different studies, suggests that the first crosses and backcrosses are heavier and somewhat larger in body dimensions than the domestic yak. Jialin et al., (1998b) reported that meat production of the first crossbred generation was assessed and carcass dissection was made of males. One group (n=14) was slaughtered at six months of age and the second (n=12) at 18 months. Crossbred yak in this study were significantly heavier (P<0.01) at 6 months and at 18 months than domesticated ones in the same herd and many of the associated carcass traits were larger in the crosses - but the dressing percentage was similar for both groups of animals (Table 6.23). It would be of interest to know whether the differences between the wild yak crosses and the domestic yak, in terms of meat production, would be maintained to the older slaughter ages more usual in herders' practice.

Effect of sex

As was seen in Table 6.22, there is a tendency for steer yak to have the higher live weights and carcass weights at slaughter relative to females and perhaps higher dressing percentages. However, there is not a consistent finding. Also, a report by Ji Qiumei et al. (2000b) indicated that in one of two groups (Jiali yak), dressing percentages and lean/bone ratio were similar in the two sexes and in the other group (Sibu yak) the females were the better in these traits.

Table 6.22 Meat production and carcass attributes of yak from different populations (animals at the age of 6.5 year or older unless otherwise indicated)

* Viscera fat included in dressing percentage; ** sterrs of 16-17 months old; '' males 2 years old; *** steers 2.5 and 3.5 years old; # location of yak within province.

[Sources: (1) Cai Li et al., 1980b; (2) Chen X. F. et al., 1981; (3) Pu et al., 1987; (4) Research Co-operative Group, 1980-87; (5) Lei, 1983; (6) Smirnov et al., 1990; (7) Jia H. G, 1966; (8) Wei et al., 1981; (9) He et al., 1997]

Table 6.23 Weight and linear measurements of carcass components of crossbred (wild yak crossed with domestic yak) and domestic yak at 6 and 18 months of age [Source: adapted from Jialin et al., 1998b]

Significant differences: * P<0.05; ** P<0.01

Effect of age

In a trial in Sichuan province, entire male yak from the age of 1.5 - 4.5 years and thereafter, yak steers to the age of 20.5 years were chosen at random from yak herds in the same area and kept under year-round grazing without supplementary feeding. All the animals were slaughtered at the Animal Husbandry and Veterinary Station in Kangdin county of Sichuan at the end of autumn, in their fattest condition. In spite of the small number of animals involved, the trends shown in Table 6.24 indicate that the dressing percentage increased with age (and live weight) up to six and a half years and declined somewhat thereafter. However, the castration of males after the age of four and a half years and the subsequent switch to steers could be an important factor in the larger increase in dressing percentage noted between the ages of four and a half and five and a half years. Variation among the steers above the age of 16.5 years showed no clear trends (the data for these ages have been pooled).

Table 6.24 Dressing percentage (carcass weight/live weight) of yak males and steers, according to age at slaughter

* m=entire male s=castrated male (steer)
** Average for the older steers.

Composition of meat

Yak meat is fine textured and scarlet in colour. It is regarded as very palatable, but muscular marbling is poor. It is rich in myoglobins and has a flavour akin to game. Among local people yak meat has been prized above that of ordinary cattle since ancient times. Table 6.25 provides some evidence on composition of the meat for different locations, breeds and ages of yak steers (the rib sample from the Tianzhu White steers was unusually fat).

Table 6.25 Composition of yak steer meat (%) [ +SD]

*at Datong Yak Farm ** Source: Research Co-operative Group (report), 1980 - 1987

Besides location, sex, age and breed (if it can be differentiated from location), the rearing treatment of the animals, which is reflected in body condition, must be expected to affect the meat composition of yak. Kirghiz literature cited by Zhang Rongchang (1989) indicates the relationship between rearing treatment and meat composition of yak (Table 6.26). It can be seen that dry matter, fat and energy in yak steer meat increased with the improved feeding level.

Table 6.26 Composition of yak steer meat (percent) under different rearing treatments in Kyrgyzstan [Source: Zhang Rongchang, 1989]

* I: suckling the [milked] dam; II: milk with artificial rearing, III: milk with artificial rearing together with supplementation in the cold season.

The amino acid content of meat from different muscles of the yak has been analysed in a number of studies (for example, Zhong Guanghui et al., 1993; Mkrtchyan et al., 1993; Ji Qiumei et al., 2000b, 2000c) The ratio of essential to nonessential amino acids was found to be between 0.6:1 and 0.8:1.