This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authorsare permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights a b s t r a c t Summary:The aim of the study was to determine the influence of increasing levels of urea (i.e., 0 (U0); 10 (U10); and 15 (U15) g kg -1 of concentrate) in sheep fed diets containing dates (local name: Azzawi), on nutrient intake and digestibility, N utilisation and ruminal fermentation. To maintain iso-nitrogenous and iso-metabolisable energy diets, the dates were added with increasing levels of urea. Sheep were fed a 400:600 (dry matter (DM) basis) concentrate:berseem hay (Trifolium alexandrinum) diet. Twelve Barki sheep (53.8 7 1.95 kg body weight) with three/diet were used in a randomised block design to determine digestibility and N balance, while four ruminally cannulated Barki sheep (56.6 7 2.15 kg body weight) were used in a 3 Â 3 Latin square design to determine rumen function. Experimental periods were 22 days with the first 15 days for adaptation. The calculated metabolisable energy (MJ kg -1 DM) and actual crude protein (CP; g kg -1 DM) contents were 12.17 and 156.1, 12.69 and 158.2 and 12.60 and 154.8, for the U0, U10 and U15 diets, respectively. Increased urea feeding increased (P o 0.05) digestibility of DM, organic matter (OM) and CP. Rumen ammonia N concentrations, allantoin in urine and the resultant microbial N supply increased linearly (P o 0.05), as did the total ruminal volatile fatty acid concentrations. Results suggest that urea supplementation to sheep diets containing dates improved DM, OM and CP digestibility and substantially increased rumen microbial growth as well as ruminal fermentation function. Crown

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The present experiment aimed to evaluate the partial replacement of soybean with slow-release urea (Optigen 1200™) in the diet of lactating cows for 84 d. Three-hundred multiparous lactating Holstein (635 ± 25 kg of body weight, BW) cows were stratified by live body weight; parity and previous milk production were randomly assigned into two experimental groups with 150 cows per each treatment. In the control treatment, 25 g soybean meal was replaced by 5.7 g slow-release urea for 84 d. Optigen treatment did not affect feed intake, daily milk production, milk composition, or milk (feed) efficiency; however, increased (P<0.01) total BW gain and daily BW gain. Optigen treatment increased (P<0.01) the digestibility of crude protein and neutral detergent fiber. Optigen treatment increased (P<0.01) estimated N balance, milk urea-N, and net energy (NE) for gain. Without affecting blood total protein, creatinine, urea-N, triglycerides, glucose, β-hydroxybutyrate, or non-esterified free fatty acids, Optigen treatment increased the concentrations of blood albumin and cholesterol compared to the control (P<0.05). In conclusion, slow-release urea could replace soybean meal in ruminant diets with no adverse effects on feed intake, nitrogen utilization, or digestibility; however, improve the total tract digestibility of fiber and crude protein in cows.

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ecently, some plants essential oils (EO) are used as natural feed additives for ruminants because their major bioactive compounds have antimicrobial properties that can be effective against undesirable rumen microbes. In addition, EO have not an adverse effect either on animal or human health and environment. This work was carried out to evaluate the effect of natural additives as essential oils addition on animal performance, feed intake, apparent digestibility, carcass characteristics, chemical composition and fatty acids profile of longissimus lumborum muscle of Barki lambs. Twenty weaned male Barki lambs ( 19.72 ± 2.09) kg BW, 3 months old were randomly assigned in one of four diet groups, 5 animals each , were received the same basal diet,(50% berseem hay, BH, and 50% concentrate feed mixture). All experimental animals were kept in individual pens for 195 days for fattening trial and 15 days for digestibility trial. At the end of the experiment all lambs were slaughtered for carcass characteristics evaluation and meat fatty acids (FAs) profile determination. The control lambs were fed their basal diet without EO supply. The other three groups were orally given, by syringe, one of the three tested EO before morning feeding as follow: the basal diet plus 2 ml/day/lamb of anise EO (Anise group), 2 ml/day /lamb clove EO (Clove group) or 2 ml/day/lamb thyme EO (Thyme group). According to the results, the experimental EO had no significant effects on nutrients intake, lamb's performance (final body weight, average daily gain and feed conversion ratio) (P> 0.05). Clove EO improved dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), acid detergent fiber (ADF) digestibility (P<0.05) and nitrogen balance% of intake (P<0.05). Ruminal parameters showed higher ruminal ammonia with thyme EO supply (P<0.05). Most of carcass characteristics were not affected by EO addition but lambs of clove group showed a significant increase in weight of feet (P<0.05), full (P<0.01) and empty (P<0.05) digestive tract, tail fat (P<0.01) and liver (P<0.05) compared with control lambs. Some blood plasma metabolites were affected by EO where plasma createnine and low-density lipoprotein (LDL) were increased (P <0.05) in thyme group however, total lipids and cholesterol increased in clove group. Fatty acids content of longissimus lumborum muscle was slightly affected by addition of EO where palmitoleic (C16:1n-7) was increased and arachidonic acids (C20:4n-6) was decreased (P<0.05) in meat of lambs fed clove. Also, clove inclusion in lambs diet increased monounsaturated fatty acids (MUFA) deposition in their meat (P<0.05). Overall, addition of anise, clove or thyme EO to lambs' diets may not have the potential to improve animal growth performance, blood metabolites and meat chemical composition. Clove EO has a considerable positive effect on nutrients digestibility and improve carcass characteristics, meat FA profile. Further research are needed with higher concentrations of EO for longer duration of supply.

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Atriplex sp. is widely distributed in arid, semi-arid and Saharan regions of the world. It grows naturally as a fodder in these areas because of its great resistance to drought and high tolerance to salt (El Shaer, 2010;Shawket et al., 2010;Walker et al., 2014). The protein content in Atriplex sp. is more complex than traditional feed resources and it ranges between 100 and 250 g/kg DM. Atriplex sp. has high concentration of non-protein nitrogen compounds (NPN) such as free amino acids and nitrates that contribute to osmotic regulation (Slama et al., 2015). Approximately 400-600 g/kg of total N in Atriplex sp. is NPN (Benjamin et al., 1992). The NPN compounds are degraded and used as a source of N for synthesis of microbial protein.

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