Determining the Palatability of Rangeland Species Grazed by Goat in Relation to Growth Stages and Day Length (Case Study: Rangelands of Deh Sheikh Village, Kohgiluyeh and Boyer-Ahmad Province)...

Palatability is one of the important characteristics of rangeland plants that is related to their acceptance by animals for grazing (Arzani, 2009). It is also defined as an animal's pleasurable reaction to its food depending on the taste, smell, texture, and appetite of nutrition animal (Church, 1988). Molyneux and Ralphs (1992) reported that while palatability means acceptance, it is not necessarily desirable. In other words, a nutritious food may not have a specific smell or taste in terms of preference, and it may not be attractive or taste bad. In terms of nutritional needs, most of the animal food may be composed of plants that have a moderate degree of palatability.

This research has been done in the rangeland of Deh Sheikh Village of Kohgiluyeh and Boyer-Ahmad provinces. To conduct this study, first two healthy three-year-old goats (females) of Mamasani breed were randomly selected from a herd that belonged to the same area. Then, three important rangeland species including two perennial species including Gundelia tournefortii and Bromus tomentellus and one annual species, Aegilops triuncialis were selected by video method to determine the palatability of species at different stages of growth including vegetative growth, flowering and seeding. For this purpose, the grazing time of goats from any plant was monitored at intervals of 30 minutes in three times including morning, noon and evening and in two repetitions (two days in each growing season) with a suitable distance from the goats. Finally, the palatability percentage of each species was calculated separately.

The results of perennial species in vegetative growth and flowering stages showed that there is no significant difference in palatability between different times of the day (morning, noon and evening). In other words, the consumption of goats from any specie is the same at different times of the day in the stages of vegetative growth and flowering. It was also observed that G. tournefortii has more palatability than B. tomentellus in vegetative growth and flowering stages (Figures 2 and 3). Also, the palatability results of perennial species in the seeding stage indicate that there is no significant difference between different species in terms of palatability at any time of the day. In the case of A. triuncialis, it was found that the palatability of this species at different stages of growth has a significant difference at the level of 1%, but at different times of the day there was no significant difference in palatability (Table 3). Also, according to Figure 7, it was found that the highest and lowest palatability of this species are related to the stages of vegetative growth (27.21%) and seeding (8.09%), respectively.

In the vegetative and flowering stages of G. tournefortii, which is a forb species, it has more palatability than B. tomentellus (grass) for goats. In fact, if G. thournefortii thorns are not for livestock, this species will appear in the form of a palatable species and will be selected by goats. In this regard, Shoaib Amjad et al. (2014) stated that the morphological characteristics of plants such as thorns, hairs, bitter taste and unpleasant reduce palatability. The findings of Arzani and Naseri (2007) in relation to the study of goat grazing behavior of G.tournefortii also showed that G.tournefortii is more grazed by goats at the flowering stage when the thorns are soft. The results of some studies also showed that even in the flowering stage, changes in flowering time and flowering and fruiting rates affect the behavior of animal species that are directly or indirectly dependent on plant phenology. On the other hand, the results of the seeding stage of perennial species showed that in the sowing stage of B.tomentellus species has a higher percentage of palatability than G.tournefortii species in all three times of the day (Figure 5). The results of this study on A. triuncialis palatability (annual species) showed that the highest and lowest palatability of this species for goats coincides with the stages of vegetative growth and seeding (Table 3 and Figure 6). It should be noted that the decrease in palatability of most plants with the development of vegetative stages is almost confirmed for most species. So that in the early growth of forage is very green and palatable and with the development of puberty most of its nutrients are reduced (Tan et al., 2003; Rebole et al., 2004; Alikhahasl, 2008). The results of some studies also confirm that forage quality indicators also change as the growth stages progress. In fact, forage quality changes constantly as plants mature, and these changes are so rapid that a significant reduction in forage quality can be detected every two or three days (Twidwell and Wegenhoft, 1999). The results of Heady and Denis (1994) show that in the vegetative growth stage of forage plants, the amounts of crude protein, sugars and vitamins are high; but fiber and lignin levels are low. According to the results of this study, it can be said that future studies can extend these results to vegetation, including a wider range of vegetative forms, because our results emphasize the importance of maintaining the complex structure of plant communities in rangelands (different species, vegetative forms and growth stages). To maintain their nutritional value over time. Although goats are known as browser and are interested to shrubs, but as Arzani and Naseri (2009) reported, in the absence of shrubs, this animal will graze on grass and forb in the rangeland, so most herds Countries A combination of sheep and goats can be seen.