"Les sous-produits de l’agriculture en Algérie"

Abstract

"The aim of this study was to analyze the effect of partial replacement of wheat straw (WS) by date pits (DP) in diets with different forage:concentrate (F:C) ratio. 7 feeds (WS, DP, orange seeds, mandarine seeds, orange pulp, olive stones and a commercial concentrate (CON)) were used to formulate several diets. The diets had F:C, OS, MS, OP, OC, ratios of 100:0, 80:20 (80) or 60:40 (60) with either WS or a 80:20 WS:DP mixture (MIX) as forage, and were designated as WS (100% WS), 80WS, 60WS, MIX, 80MIX and 60MIX. Samples (500 mg) of each diet were incubated with 50 ml of buffered rumen fluid at 39ºC. Final pH, production of volatile fatty acids (VFA), total gas and methane, NH3-N concentration and organic matter apparently fermented (OMAF) were determined after 24 h. The neutral detergent fibre (NDF) content of WS and DP was 71.1 and 86.5% (dry matter basis), but NDF lignification was greater for DP (26.7% of NDF) than for WS (15.3% of NDF). Compared with WS, the ruminal fermentations of the MIX diets resulted in greater (P<0.05) butyrate proportions (11.7 vs. 14.0%) and lower (P<0.05) gas production (2768 vs. 2588 μmol) but there were no differences (P>0.05) in the rest of the fermentation parameters. For both forages (WS and MIX), increasing the proportion of CON, OS or OM in the diet increased (P<0.05) the production of gas and total VFA, the molar proportion of butyrate and the OMAF. There were no differences (P>0.05) between 80WS and 80MIX diets in any fermentation parameters. Compared with 60WS diet, the fermentation of 60MIX diet resulted in greater production of total VFA, but no differences were detected in the rest of the parameters measured. The final pH, methane production and NH3-N concentrations ranged between 6.91 and 7.00, 434 and 516 μmol, and 330 and 359 mg/L, respectively, with no differences (P=0.059 to 0.121) among diets. The results indicate that WS can be replaced by DP at 20% of the forage portion of the diet without any detrimental effect on ruminal fermentation. Furthermore, in diets with 60:40 F:C ratio, incorporating DP resulted in greater VFA production. If this result is confirmed in vivo, it would be of great interest in sheep practical feeding. In the other hand, the experiment was conducted to evaluate the effect of the incorporation of date seeds in a ration based on wheat straw or a mixture with date seeds and concentrate, orange pulp or olive stones on the weight and the daily grain weight. Thirty (30) rams of Ouled Djellal breeds of 12 months were distributed randomly in 5 groups of six animals.Three groups received a diet composed of wheat straw, orange pulp or olive stones (60:40), the other groups received a diet composed of a mixture of wheat straw and date seeds (80:20) as a roughage in addition to concentrate or orange pulp at 40% of the diet. The diet based on wheat straw and concentrate allowed to cover the maintenance needs of animals, in addition to a daily gain weight of 125 g/d. Moreover, the animals fed olive stones lost drastically, the first weeks, stabilize in the middle and finally improve their weights at the end of the experiment. Moreover, the animals fed orange pulps showed an increase of their weights and daily gain and were comparables to those fed concentrate as supplement. Animals fed date seeds showed an increase of the weights with a daily gain weight between 125 to 250g/d. From these results, we can deduce that the incorporation of date seeds could not only cover the maintenance needs of ovine during (winter, summer) but also increase the weights of daily gain weights of animals. The orange pulp can be a substitute to concentrate if the pulps are distributed directly after juice exctraction. Olive stones can replace the concentrate for maintenance if the animals are well adapted to them."