الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 75 |  |  |
| | | from | 75 | | |
Abstract
The extension in cultivated salt-tolerance plants in order to reduce the cost of feeding in desert areas is one of the primary objectives for sustainable development of animal production in arid and semi-arid area. The aim of the current experiment was to investigate the feeding selectivity of camels and their ability to meet nutritional requirements while grazing on alfalfa (which is high in protein), barley (which is high in energy), or a mix of both. Eighteen lactating camels were divided into three feeding treatments with six camels in each group. The animals were allowed to graze daily on either alfalfa, barley or a mix of both for two periods, each lasting one month. The concentrate supplement, which was given to each camel, was 40 g per kg BW0.75, divided into two parts - one in the morning and another in the afternoon. The total energy expenditure (EE) was estimated by heart rate (HR) monitors for 48 hours after being calibrated by oxygen consumption using an upgraded face mask open-circuit respiratory system. During the first period, a greater forage intake was observed for those grazing barley vs. alfalfa (25.1 vs. 10.7 g/ kg BW0.75, respectively), while those grazing the mixed pasture were intermediate (13.4 g/ kg BW0.75). However, total dry matter intake and digestibility followed the same trend as forage intake, with the greatest digestibility for those grazing barley and the lowest one for those grazing alfalfa alone or mixed with barley (62.8 vs. 56.4 and 59.0%, respectively). Neutral detergent fiber digestibility was going on the same trend of the dry matter digestibility (56.7 vs. 45.1 and 52.2%), while the contrary was observed for the crude protein digestibility (58.5 vs. 61.5 and 61.4%, respectively). On the other hand, at the second period, similar forage intake (15.7 g / kg BW0.75) and dry matter digestibility (55.6%) were observed among treatments. This DROP in intake and digestibility of the cultivated barley was expected as the selected plant part was shifted gradually from barley grains to mostly straw with a function of time. a significantly (P<0.05) lower milk yield and energy were obtained by those grazing barley vs. alfalfa alone or combined with barley with no interaction was detected between period and treatment. A similar HR and EE were found across periods and treatments. As a result, a greater gross and digestible energy intake for 1st period and those grazing barley resulted in a higher energy balance when compared to 2nd period and those grazing alfalfa alone or combined with barley. In conclusion, grazing barley, alfalfa or a mixed pasture of both of them can not cover the nutrients requirements of lactating she-camels. The cultivated barley is better utilized by camels than alfalfa but supplementary feeding is essential to cover the aforementioned requirements. Heart rate is successfully used as an indicator for the energy expenditure in camels.