Abstract
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.
Highlights
In the Mediterranean Basin, livestock production and crop farming have always co-existed
Lambs were grazing on a plot of barley stubble cultivated according to conservation agriculture (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)
According to Parr et al (1990), low-input sustainable agriculture (LISA) are systems how “seek to optimize the management and use of internal production inputs and to minimize the use of production inputs, such as purchased fertilizers and pesticides, wherever and whenever feasible and practicable, to lower production costs, to avoid pollution of surface and groundwater, to reduce pesticide residues in food, to reduce a farmer's overall risk, and to increase both short- and long-term farm profitability”. This suggest that LISA will have a physical productivity limited by the maximum on-farm resources that can be mobilized and that LISA can be associated with lower output (Poux, 2008)
Summary
In the Mediterranean Basin, livestock production and crop farming have always co-existed. Local sheep breeds are often assigned to extensive management system (OEP, 2013) including local feed resources such as crop residues (e.g. cereal straws and stubbles: about 1.5 million and 500 000 tones/year) These practices might not be independent of farming system evolution and development. According to Parr et al (1990), LISA are systems how “seek to optimize the management and use of internal production inputs (that is, on-farm resources) and to minimize the use of production inputs (that is, off-farm resources), such as purchased fertilizers and pesticides, wherever and whenever feasible and practicable, to lower production costs, to avoid pollution of surface and groundwater, to reduce pesticide residues in food, to reduce a farmer's overall risk, and to increase both short- and long-term farm profitability”. This experiment was designed to study the effect of stocking rate on stubble biomass variation and lamb growth
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