Small ruminant production is the main source of income of farmers living in arid and semiarid regions. Sheep and goats raised in these areas are generally confronted with severe nutritional deficits during food scarcity period which exacerbate disease and health problems and consequently low productive and reproductive performances. These areas are characterized by rainfall seasonality and scarcity resulting in a low fodder potential. Therefore, native rangelands are degrading due to overgrazing, high stocking rates and mismanagement. Options to improve small ruminant-based production systems include i) innovative technologies targeting the increase of feed resources availability, rumen manipulation using natural compounds to boost microbial activity, improving diets' quality, alleviation of feeding cost, and better control of livestock watering. Although this paper is focussing on the benefits from these technical options, we should bear in mind that i) the organization of local institutions for better adoption of these technologies and for protecting the main natural resources (rangelands and water) and ii) the participatory approach involving all partners concerned with the improvement of farmer's income and livelihood are key tools for promoting livestock sector in the target areas. A set of simple, inexpensive and environmentally friendly options that could ameliorate small ruminant production in the semiarid regions are discussed in this paper.

This paper reviews the small but growing literature on the water footprint (WF) of livestock production and provides an analysis of the strengths, weaknesses, opportunities and threats of this indicator. We identified 42 papers published in peer-reviewed international journals between 2000 and 2017, which covered the WF of dairy, meat and egg production using life-cycle assessment and WF network methodologies. The WF of livestock products decreases with the level of intensification of the farming system. In addition, the WF of meat is higher than that of either milk or eggs. The WF of beef is much larger than the WFs from sheep, goat, pork and chicken. The WF variation among different animal products is explained by the difference of the feed conversion ratio. Ruminants (cattle, sheep and goat) have a poor feed conversion ratio compared with monogastric animals (poultry and swine). Estimating the WF of livestock production and economic analysis of water use at different stages of production will help farmers and other stakeholders to identify the most demanding activities in term of water use, and implement strategies to improve water-use efficiency. Thus, feed production was identified as the largest contributor of the WF of livestock production. Options to reduce the WF of livestock production include the use of low-WF feeds, more efficient irrigation of crops used for livestock feed, and reduced consumption of animal-sourced protein in human diets through substitution with plant proteins. The strengths, weaknesses, opportunities and threats analysis highlighted the importance of combining WF with other environmental-footprint and sustainability indicators to provide more reliable information for decision makers.

Atriplex nummularia L. (atriplex) foliage and urea-treated straw have been used as nitrogen supplements for Barbarine lambs given Opuntia ficus-indica f. inermis (cactus) and their effects on feed intake, diet apparent digestibility, nitrogen balance and daily gain have been evaluated. Twenty-four lambs (mean live weight 19·9±2·79 kg) were randomly allocated to one of four experimental groups, groups 1–3 received freshly cut pads of cactus ad libitum. Group 1 was supplemented with 600 g untreated barley straw (C+US), while group 2 received 600 g urea-treated straw (C+UTS). Group 3 received 600 g untreated straw and 400 g atriplex (C+A). The amount of atriplex was calculated so that groups 2 and 3 receive iso-nitrogenous diets (i.e. C+UTS and C+A). Group 4 (US+BW) received a diet commonly offered to sheep by Tunisian smallholders, untreated straw ad libitum and 400 g of ground barley grain and wheat bran mixture (50[ratio ]50). A growth trial (60 days) followed by a digestibility trial (8 days) were performed in 1999. Irrespective of dietary treatment, cactus intake was high, averaging 500 g dry matter (DM)/day. It was not affected (P>0·05) with N supplementation, as urea-treated straw or atriplex. Sheep fed cactus-containing diets drank considerably less (P<0·001) water than those on the common diet (US+BW). Nitrogen provision improved significantly apparent digestibility of cactus-based diets. Urea treatment of straw increased content of digestible dry matter, organic matter, crude protein and cell wall (NDF) by 100, 100, 120 and 290 g/kg diet, respectively. There was a further increase when atriplex was provided instead of urea-treated straw. Nitrogen balance was positive across all dietary treatments but was improved when the nitrogen content of cactus-based diets was increased. Sheep fed on cactus and supplemented with atriplex retained the same amount of N as those fed the common diet (US+BW). The efficiency of microbial N production, estimated by the urinary excretion of allantoin, was improved (P0·05) on sheep growth (31·4 and 39·7 g/day, respectively). It is concluded that cactus may be considered as an emergency feed and water source for sheep in arid and semi-arid zones. Nitrogen supplementation of cactus-based diets with urea-treated straw or atriplex foliage improved the feeding value of these diets and consequently sheep growth. A cactus-based diet, supplemented with atriplex, promoted similar growth in sheep as the commonly used diet (US+BW).

Thirty young male sheep were given air-dried foliage of Acacia cyanophylla Lindl. ad libitum and 400 g oat hay. Animals were divided into five equal groups each of which was supplemented with either 300 g concentrate with (CPEG) or without (C) 20 g polyethylene glycol 4000 (PEG) or urea-containing feedblocks with (BUPEG) or without (BU) PEG. One other treatment was PEG-containing feedblock without urea (BPEG). PEG was used to preferentially bind A. cyanophylla condensed tannins (CT). Feedblocks (BU, BPEG and BUPEG respectively) were made from olive cake (395, 376 and 353), wheat bran (263, 250 and 235), wheatfeeds (132, 125 and 118), quicklime (88, 83 and 78), salt (44, 42 and 39), mineral and vitamin supplement (12, 10 and 10), urea (66, 0 and 59) and PEG (0, 114 and 107 g/kg). These diets were used in growth (60 days) and metabolism (7 days) studies. Urea-containing feedblocks, as compared with concentrate, were higher in crude protein (CP; 235 v. 116 g/kg DM) and lower in metabolizable energy (6 v. 10 MJ/kg DM). The type of supplement (i.e. concentrate v. feedblocks) had no effect (P > 0·05) on A. cyanophylla DM intake, CP and neutral-detergent fibre (NDF) digestibilities and nitrogen (N) retention. However, concentrate-containing diets exhibited higher DM and organic matter (OM) digestibilities (P < 0·05), urinary excretion of allantoin (P < 0·05), microbial N supply (P < 0·001) and average daily gain (P < 0·001). PEG supply increased DM intake of A. cyanophylla, CP digestibility, N retention, allantoin voided in urine, microbial N supply and lamb growth. PEG-containing feedblocks enriched (BUPEG) or not (BPEG) with urea had similar effect on A. cyanophylla intake, DM, OM and NDF digestibilities, allantoin in urine, microbial N supply and average daily gain. These findings suggested that urea inclusion in feedblocks are not necessary and thus the feeding cost may be reduced. The higher amount of microbial N and daily gain in lambs given concentrate as compared with those on feedblock-supplemented diets was ascribed to the level of energy which was low in the latter diets. Enrichment of feedblocks with energy-rich ingredients such as molasses or cactus fruits could be a solution. This work confirmed that tannins depressed the nutritive value of this shrub species and lamb growth. However, the reduction was not drastic in the absence of PEG in the diet. Feedblock diet (BU) matched maintenance requirements of lambs while lambs on concentrate-supplemented diet (C) grew at a rate of 78 g/day. The choice between these two supplements will depend upon farm conditions and objectives.

Twenty-five male Barbarine lambs aged approximately 150 days were divided into five groups. All the animals received 400 g/day of oat hay and Acacia cyanophylla Lindl. foliage ad libitum. Two groups also received 300 g/ day of a mixture (70: 30) of processed barley and wheat bran, with or without 20 g polyethylene glycol 4000 (PEG), groups CPEG and C respectively. The three other groups had free access to feedblocks based on olive cake, and containing urea, urea and PEG, or PEG, groups BU, BUPEG and BPEG respectively. Lambs were slaughtered at age 230 days and meat quality was determined in the longissimus thoracis et lumborum muscle. Lean colour was significantly affected by dietary condensed tannins. Lightness (L*) was higher in those animals that did not receive PEG (P < 0·001) indicating that condensed tannins can cause lighter meat colour. This difference was not due to the ultimate pH, which was not affected by the inclusion of PEG in the diet. Meat from groups that received supplementation of concentrate had lower values of resistance to the Warner-Bratzler shear device compared with those that received feedblocks. This result was confirmed by a taste panel, that found samples from groups C and CPEG more tender than samples from groups BU, BUPEG and BPEG. Inclusion of PEG in the diet increased intensity of flavour (P < 0·05) but had no effect on overall acceptability. Meat from animals that had received the concentrate had higher overall acceptability (P < 0·05) than meat from animals that received the feedblocks. No differences were found in meat chemical composition.