تأثیر انتخاب آزاد یونجه، جاشیر و کنسانتره بر قابلیت هضم و رفتار مصرف خوراک برههای نر عربی (Persian)

Introduction Ruminants require roughage in their diets to maximize production and to maintain health by sustaining a stable environment in the rumen. There is a need to identify local plants that can offer high quality forage to local ruminants. P. ferulacea (family: Umbelliferae) is a valuable forage grass found in high mountain areas of South-east Iran. Local farmers cut and wilt the plant, prior to feeding it to sheep. Sheep are selective and spend a lot of time selecting and sorting feed materials. Domestic livestock are herbivores that evolved to eat a wide array of vegetal species and typically select a diverse diet even when their nutritional requirements can be met by ingesting a single feed. A free-choice feeding method partially mimics nature and facilitates selection based on nutrient requirements that fluctuate along with feed quality and availability. Also, this method requires less use of manpower and equipment. The information available regarding the effects of ad libitum supply of concentrate and the possibility of freechoice provision of forage in lambs is very limited. Also, limited data is available concerning nutritional behaviors of lambs fed high-concentrate diets, and this information is even more limited in terms of providing feed-choice. The aim of this study was to investigate the effect of free-choice provision of two forage sources including alfalfa and P. ferulacea in addition to concentrate on digestibility and behavior of Arabian lambs. Materials and Methods A total of 18 male lambs of Arabic breed with an average of 90 ± 8 (SD) days of age and body weight of 19 ± 3 (SD) kg were used in the study in a completely randomized design for 45 days. Lambs were housed individually in pens (1.3 m×1.5 m) in an open shed building. Cages were separated by a metal fence with a bar design that allowed contact between animals. The animals were randomly assigned to one of the three experimental diets including free choice between; 1-alfalfa hay and concentrate, 2-P. ferulacea and concentrate, and 3-alfalfa, P. ferulacea and concentrate. The lambs were fed the total mixed rations ad libitum once daily at 0800 h and had free access to fresh water at all times. Essential oils of P. ferulacea were identified using gas chromatography-mass spectrometry. Samples taken for DM and chemical analysis were oven-dried at 55 °C for 48 h and then ground to pass through a 1-mm screen. Chemical analyses were performed in duplicate. Feed offered and refusal of each lamb were recorded daily. Digestibility was measured by total collection of feces during a 5-d period. The behavior of lambs was recorded with nine video cameras that were connected to a digital video recorder. Video recordings continuously observed visually for each lamb over a 48-h period. Recorded activities were registered together with their beginning and ending times. Data for each activity are reported as the total time, expressed in minutes, in which the lamb maintained this specific activity. Chewing behavior was divided into eating and ruminating. Intake and digestibility data were analyzed using a GLM procedure of SAS 9.2. Multiple mean comparison were carried out using Tukey's test. Animal behavior from video recordings was analyzed using a GLIMMIX procedure of SAS. Comparison. For the different statistical tests, significance was declared at P<0.05. Results and Discussion The compounds of α-bisabolol, β-Pinene, α-Pinene and δ-3-carene had the highest amounts among P. ferulacea essential oils. Free-choice provision of two forages increased dry matter intake and the proportion of consumed forage compared to other treatments. Forbes and Provenza (22) reported that in freechoice provision between forage and concentrate, ruminants allocate about 20% of the dry matter intake to forage. This finding is in an agreement with observed ratio of forage consumption in treatments with one forage source but is less than the observed value in the treatment with free access to two forages (36.2%). Among the mechanisms that may be involved in this increase is the greater diversity of forages that act as a stimulus for its consumption. Lambs consumed P. ferulacea as the only forage source showed higher digestibility of dry matter, organic matter, NDF and ADF compared to other treatments. Low lignin content of P. ferulacea compared to alfalfa is one of the main reasons for its higher digestibility. Lambs receiving P. ferulacea as the only source of forage had the lowest time spent eating per day compared to the other treatments. When animals were given a choice between alfalfa and P. ferulacea, the time spent eating increased significantly compared to P. ferulacea alone. Lambs that had access to two sources of forage had the lowest feeding time per gram of NDF and ADF compared to other treatments. This decrease could be due to the higher consumption of dry matter as well as NDF and ADF in this treatment compared to other treatments. Lambs that had access to two forage sources spent more time ruminating compared to the alfalfa recipient treatment. The highest duration of rumination per gram of NDF and ADF was observed in P. ferulacea treatment as the only source of forage. It has been shown that the chewing per gram of forage NDF is higher in animals with lower NDF intake (4). In this regard, Grant (24) suggested that there is an adaptive mechanism when consuming low-forage diets by increasing chewing per gram of forage NDF. Nonnutritional behaviors including self grooming, licking and biting fixed objects and laying time were not affected by treatments. Conclusion Providing two forage sources instead of one source, led to an increase in dry matter intake. The higher digestibility of dry matter, organic matter, NDF and ADF in the treatment of P. ferulacea compared to alfalfa indicates the high nutritional value of this forage. Due to the limited information available on free concentrate supply and the lack of examination of rumen and liver health indicators in the present study, any practical conclusion regarding ad libitum concentrate intake requires further research. [ABSTRACT FROM AUTHOR]

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