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sur le développement des zones arides et semi-arides

Titre : Status of Crop Residues in Gedarif State and Improvement of Sorghum Stover utilization through Urea Treatment and Concentrate Supplementation

Auteur : Asaad Salim Ahmed Guma

Université de soutenance : University of Khartoum

Grade : Doctor of Philosophy in Animal Production (Animal Nutrition) 2021

Résumé partiel
This study was carried out to estimate the total production of crop residues in Gedarif State and evaluate the enhancement of nutritional value of sorghum stover through urea treatment and supplementation. The study is composed of four experiments. In experiment one, survey was conducted in Gedarif State to estimate total production of feed from crop residues of different resources and to determine nutrient requirement of animal units, and thus, determining feed balance on State level. Primary and secondary data along with visits were used for this study. Descriptive statistics and analysis of variance were used to analyze the collected data. Results showed that total need of feed was estimated to be 9.1 million ton of dry matter and available estimated total production was 4.85 million tons dry matter, with 43% deficit. However, sorghum stover contribution to the total need was 59%. Experiment two was designed to evaluate the effect of urea treatment on chemical composition and in vitro digestibility of sorghum stover of seven varieties. Sorghum stover of seven varieties from Gedarif crop market was treated with 5% urea, for three weeks as incubation period. Proximate chemical analysis and in vitro digestibility were used as indices. The results showed that, crude protein (CP) of the treated sorghum stover was enhanced (15.81%) over the untreated (4.06%). Neutral detergent fiber (NDF) for sorghum stover was decreased from 25.90% for untreated to 19.30% for urea treated samples. The increment of CP in concomitant with reduction in NDF for treated stover compared to untreated stover was reflected positively in organic matter digestibility (52.11% vs. 39.59%, respectively). In the third experiment, potential gas production was performed to evaluated nutritional value of seven sorghum stover varieties (treated and untreated). Gas production was continuously measured by incubating samples in buffered rumen fluid collected from three sheep. Cumulative gas production was recorded at 3, 6, 12, 24, 48, 72 and 96 h of incubation periods and kinetics of gas production was described. Results showed that four of sorghum stover varieties responded positively to urea treatment and recorded high gas production compared with untreated samples. The same trend was observed in VFA’s concentrations. The varieties that responded positively were, Ajabsido, Corocola, Dapper and ArfaGadamik. Experiment four was conducted to investigate the effect of urea treated sorghum stover and concentrate supplementation on sheep performance. Sheep were offered treated and untreated stover as basal diet (ad. Libitum) with two levels of concentrate supplementation (250 and 500 g/sheep/day) in 2×2 factorial was arrangement. Twelve desert sheep lambs were assigned randomly to four groups of three lambs each. Group one was fed treated stover with 500 g/day ; Group two fed untreated stover with 500 g/day concentrate ; Group three fed treated stover with 250 g/day concentrate and Group four fed untreated stover with 250 g/day concentrate.

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