Níveis de proteína e energia dietéticos para redução do parasitismo gastrintestinal em ovinos artificialmente infectados

Abstract

The aim was to evaluate the effects of feeding different crude protein to total digestible nutrients (TDN) ratios on intake, performance, apparent digestibility and nutrient metabolism, carcass characteristics, parasitological and hematological parameters, and biochemical profile in lambs experimentally infected with Haemonchus contortus. A total of 40 male lambs with mean initial weight of 18 ± 1.2 kg and five months old were housed in metabolic cages. The treatments were four different protein:TDN (CP/TDN) (71:597; 103:641; 140:679 and 186:696) to animals infected or not with Haemonchus contortus, totaling eight treatments and five replicates per treatment. A 4 x 2 factorial scheme (four crude protein to TDN ratios and two infection conditions)was used in a completely randomized design. Infection negatively influenced the dry matter intake, neutral detergent fiber intake (g/kg0.75), TDN intake (g/kg0.75), protein and neutral detergent fiber digestibilities, which were lower in infected animals. There was an interaction between diet and infection on gross, digestible and metabolizable energy intakes (Mcal/kgDM), in which infected animals fed CP/TDN 140:679 and 186:696 had lower intakethan those not infected fed the same diets. Energy balance was negative for infected animals receiving CP/TDN 71:597.Purine absorption regard less of infection condition was higher in animals fed CP/TDN140:679 and 186:696 than those receiving the diet with 71:597. Microbial protein synthesis was lower in infected animals fed CP/TDN103:641 and 186:696. Infection decreased metabolizable protein intake in animals receiving CP/TDN71:597; 140:679 and 186: 696diets. Infected animals had lower average daily gain (0.145 kg/day) and lower fat thickness (1.86 mm). There was an interaction (P<0.05) between diet and infection on feed conversion, in which conversion was worse in infected animals fed CP/TDN71:597diet. Carcass weights and yields varied according to the diets. The highest fecal egg count (FEC) was found in animals fed the ratio CP/TDN71:597 (3213.7).Animals receiving CP/TDN71:597 and 186:696 diets had higher number of Haemonchus recovered. The infection reduced the values of globular volume and total plasma proteins. There was an interaction (P<0.05) between diet and infection on the degree of anaemia assessed by the Famacha© method, in which infected animals fed CP/TDN 71:597 had higher Famacha© score (2.16) than those not infected receiving the same diet (1.24). There was an interaction between diet and infection (P<0.05) on albumin concentrations, in which infected animals receiving CP/TDN71:597 had lower albumin concentrations than those not infected fed the same diet. Feeding CP/TDN140:679 and 186:696 diets to lambs provides adequate nutrient supply that allowsa better balance in the relationship between parasite and host. Then, the nutritional plan to be used should be the most suitable for each type of farm and farmer‟s reality.