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Améliorer le succès de la période critique de transition du peri-partum chez les petits ruminants : perturbations physiologiques et métaboliques et prospection des effets de produits naturels pour les éviter

Abstract : The peri-partum period is a critical time for small ruminants because nutritional requirements are very high and feed intake is often limited. Nutritional diseases, such as pregnancy toxemia, can develop. Farmers try to limit these problems. β-glucan and saponin-based plant extracts have been shown to have favourable effects on animal production: immune-modulation for the former and reduced methane production and modification of rumen fermentation patterns for the latter. However, little is known about their effects on metabolism. Therefore, the general objective was to better understand the effects of 1) β-glucan injections and 2) dietary saponin, on metabolism and rumen fermentation in small ruminants during the transition period. The influence of β1,3-glucan (i.m. injections, 1ml/animal/week for 60 days) on the metabolic profile of 14 Santa Inês ewes in the last weeks of gestation was studied. Two groups of ewes were formed in late gestation: a glucan group (G, n=7) and a control group (C, n=7). Nutritional requirements during the experiment were covered. Blood samples were collected throughout the study. Blood samples were analysed for metabolites, ions and enzymes. All ewes were clinically healthy. Glucose, L-lactate, non-esterified fatty acids and β-hydroxybutyrate peaked at parturition (p<0.05). Aspartate aminotransferase (AST) was higher in C vs. G (p<0.05) and there was a similar trend for fructosamine and albumin (p<0.10). Urea tended to be higher in G vs. C (p<0.10). In conclusion, the changes with time were consistent with a change in physiological status (gestation/lactation). β1,3-glucan appeared to protect muscle and liver because AST levels were lower than in controls and it did not negatively affect metabolism. The influence of a dietary saponin-based additive (25g saponin/animal/day) on the metabolic and rumen fermentation profile of Saanen and Alpine dairy goats during two different metabolic situations: metabolic neutrality (mid-lactation) and metabolic imbalance (pregnancy/lactation) was studied in two experiments. Experiment 1, used mid-lactating goats (Saponin group (S), n=10; Control group (C), n=10). The 6 week experiment was divided into: 1 week of C diet, 4 weeks either S or C and 1 week C. Experiment 2, used peri-parturient goats (Saponin group (S), n=12; Control group (C), n=12). The 7 week experiment was divided into: 1 week C diet, 4 weeks either S or C (stopping at parturition) and 2 weeks C. Nutritional requirements during the experiments were covered. Blood samples and rumen fluid were collected throughout both experiments. Blood samples were analysed for metabolites, ions and enzymes. All the goats were clinically healthy. There was no effect of saponin in experiment 1 on animal husbandry measures, plasma metabolites and ruminal fermentation (p>0.05). The ruminal acetate to propionate ratio tended to be affected by treatment (S < C; p=0.057). There was no effect of saponin in experiment 2 on blood metabolites (p>0.05), except for plasma urea (S > C; p=0.054). Total protozoa numbers tended to be affected by treatment (S > C; p<0.10). Most of the animal husbandry, plasma and ruminal variables showed a time effect around parturition (p<0.05). In conclusion, dietary saponin during mid-lactation or the peri-partum period had little effect on metabolism and ruminal fermentation. The trends observed in blood urea, total protozoa count and acetate/propionate ratio could be potentially beneficial. Lastly, the potential for saponin to influence ruminal fermentation may depend on the level, the period of administration and the type of diet. β-glucan and saponin did not have a negative effect on metabolism and it would be interesting to conduct further work in animals suffering from pregnancy toxemia. Studies could also be conducted on the possible immune actions of β-glucan and saponin.
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Rafael Otaviano Do Rego. Améliorer le succès de la période critique de transition du peri-partum chez les petits ruminants : perturbations physiologiques et métaboliques et prospection des effets de produits naturels pour les éviter. Veterinary medicine and animal Health. Institut agronomique, vétérinaire et forestier de France; Universidade federal de Pernambuco (Récife, Brésil), 2017. English. ⟨NNT : 2017IAVF0001⟩. ⟨tel-03386188⟩

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