Influence de l’alimentation sur la reproduction des petits ruminants.
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The purpose of this study was to investigate the impact of nutrition on the productive performances of reproductive ewes through the valorization of local food resources. Thus partial or total barely substitution by dates wastes is undertaken in order to evaluate the influence of energy complementation on the metabolic profile and the ponderal performances of the ewes and their lambs. The study was conducted on 135 healthy, multiparous Ouled Djellal ewes aged between 3 and 4 years, belonging to the experimental farm of ITELV-Ain M'lila located in the East of Algeria. The physico-chemical analysis of the feed showed that concentrate and hay are the richest in dry matter, organic matter and cell walls (NDF and ADF). Green forages are the richest in total nitrogen and total ash, contrary to the dates wastes that are the most lignified (ADL). The evaluation of the chemical composition of rations (0% R, 25% R, 50% R and 75% R) distributed at the end of pregnancy did not revealed any significant difference except for the 100% incorporated ration of dates wastes which shows the highest rate in ADF and cellulose and the lowest rate in hemicellulose. The study of the influence of the physiological stage on various biochemical blood parameters in the Ouled Djellal ewes of the semi-arid zones showed that the pregnancy or lactation state affect significantly the serum levels of glucose (p<0,001), cholesterol (p<0,001), triglyceride (p=0,0003), total protein (p=0,0007), urea (p<0,0001), albumin (p<0,0001), creatinine (p<0,0001), bilirubine (p<0,0001), calcium (p=0,01), phosphate (p=0,005), magnesium (p<0,0001) and iron (p=0,0001) as well as the enzyme activity of ASAT (p=0,0004), ALAT (p<0,0001) and GGT (p=0,0005). The metabolic profile of ewes at the end of pregnancy, supplemented with 25% of dates wastes, is characterized by hypoglycemia (p=0,0002) accompanied by significant hypercholesterolemia (p=0,008) and hypertriglyceridemia (p<0,0001). While, the levels of total proteins (p<0,0001), albumin (p=0,0006), urea (p=0,005), creatinine (p=0,002) and bilirubin (p=0,002) were significantly lower in group supplemented with 50% of dates wastes, as well as the concentrations of ASAT (p<0,05), ALAT (p=0,006), GGT (p<0,01), phosphorus (p=0,002), magnesium (p<0,0001), sodium (p=0,0003) and iron (p=0,01) showed a significant decrease in the same group. The analysis of the data relating to the performances of production shows clearly that Ouled Djellal ewes supplemented with 25% and 50% of date wastes improved significantly their of body condition score (p<0,0001) and their dairy production (p<0,0001). Which reflected positively the performance of their products growth. Contrary to the birth, the 20 days old lambs resulting from the supplemented mothers with 50% are significantly heaviest (11,91±0,41 kg ; p<0,0001) with the highest growth rate equal to 302,9±18,32 g/j ; p<0,0001). On the other hand, at 1 month of age, the feed mode had a notable effect on the average weight and GMQ of the lambs of the 25% batch (335,6±55 g/j ; p>0,05). Despite of the low level of dates wastes in crude proteins the use of this energetic co-product during steaming remains efficient for the improvement of growth performance in lambs through the improvement of the diary production of their mothers.