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.
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