This study aimed to determine the emissions of methane (CH₄) and nitrous oxide (N₂O) from seven Tunisian livestock species and their evolution over eleven consecutive years (2008–2018). The species of animals used were cattle (dairy and others), sheep, goats, camelids, horses, donkeys and mules, and poultry. The estimations of CH₄ and N₂O emissions were based on the Intergovernmental Panel on Climate Change (IPCC) guidelines for national inventories, using Tier 1 and Tier 2 approaches, with its default emission factors (EFs). The Tier 2 approach was applied only for the calculation of EF to estimate CH₄ emissions related to livestock manure management. CH₄ emission represented more than 92% of the total greenhouse gas (GHG) from livestock emissions. Moreover, 53% of the total CH₄ emissions from livestock were derived from cattle, followed by sheep, goats, other mammals (camelids, horses, mules, and donkeys), and poultry. During the period covered by the study (2008–2018), a slight and continuous decrease of both livestock population and total GHG emissions was observed, mainly in terms of CH₄. In mammals, CH₄ emissions were greater than N₂O emissions, whereas in poultry, N₂O emissions were up to 2.6 times greater than CH₄ emissions. The aggressive drive of the government to increase cattle and sheep production might affect CH₄ emissions in the future. Therefore, periodic estimations of GHG emissions from livestock are required to follow the time trends for more rational decision-making regarding livestock and GHG emissions policies.

The integration of livestock in the practices of conservation agriculture (CA) was assessed in Tunisian semi-arid conditions. Forty five Barbarine lambs (aged 220 ± 10 days, average body weight 20 ± 2.5 kg) were used in a performance trial, carried out in the experimental station of INRAT. During the experiment, lambs were grazing on a plot of barley stubble cultivated according to CA was divided into 6 fenced equal subplots and to each subplot was assigned a stocking rate of animals (15 and 30 lambs per hectare, SR15 and SR30 respectively). The biomass of stubble and its botanical composition were estimated 2 times, using quadrats sampling technique. Live weight was determined 3 times after the start of the experiment (three 15-days successive periods) to calculate live weight gain (LWG) and daily live weight gain (DLWG). The amount of biomass varied (P <0.05) from 2204 to 2067 kg DM / ha for SR15 plots and from 2404 to 1826.5 kg DM/ha for SR30 ones. This decrease was higher with SR30 (P<0.05). Heads proportion decreased first, then leaves and finally stems. Biomass chemical composition declined with sampling period. During the first grazing period, lambs assigned to both treatments lost LW (P<0.001), mainly SR30 lambs as compared to SR15 (P<0.05, -610 and -110 g, respectively). The same trend was observed in DLWG (P<0.05). In the second period, the two groups exhibited similar LWG (about 2 kg) and DLWG (about 171 g/d). In the third period, SR15 lambs maintained their body weight, while SR30 group lost (P<0.001) about 400 g comparatively to the second period. It was concluded that under the studied feeding system, stubble grazing without supplementation allowed Barbarine sheep to maintain body conditions. Key words: Lambs, barley stubble, stocking rate, conservation agriculture.

Conservation practices that involve leaving mulch on the soil are known to increase soil fertility. However, mulch is an important source of feed for ruminant livestock. Accordingly, the trade-offs between mulching and stubble uptake by livestock are currently hot topics in the research field. In this study, a comparison between the quality of stubbles of wheat grown in no-tillage and conventional tillage fields and the rumen fermentation characteristics of Barbarine ewes grazing in the two fields was carried out. Samples were collected four times after wheat grain harvesting. Immediately after harvest, stubble biomass was slightly higher under no-tillage than conventional tillage. The ewes displayed different grazing behavior, with feeding at a higher rate on the conservative stubble than the conventional stubble. This feeding behavior seemed to be an adaptive strategy to offset the decline in the nutritional quality of stubbles from no-tillage-grown wheat. Indeed, dry matter, protein, fiber, and ash contents were lower in stubbles from no-tillage than conventional tillage at the second sampling time. Consequently, the concentration of the volatile fatty acid, propionic acid, was lower in ewes grazing in the conservative plots. However, this feeding behavior did not cause any body weight impairment during the two-month experimental period. At the end of grazing, the no-tillage practice was found to be comparable to the conventional tillage system according to the amount of residue remaining on the soil surface. Therefore, no-tillage could not be used to solve the competition between crops and livestock for residues.