Intake, apparent digestibility of nutrients, milk yield and milk composition were all evaluated in goats receiving diets with 47% of corn silage and 53% of concentrate. Dietary crude protein (CP) was increased as follows [dry matter (DM) basis]:11.5, 13.5, 15.5 and 17.5%. Twelve lactating Alpine goats were randomly assigned to three 4 x 4 Latin squares with 15 days experimental periods: seven days for diet adaptation and eight days for samples collection. Total collection of feces was done from day 8 to day 12 of each period while milk samples on day 10. Data were evaluated by analysis of variance and regression. Intakes of DM, organic matter (OM), CP, rumen degradable protein (RDP) and total digestible nutrients (TDN) increased linearly with the increment of dietary CP. Similarly, digestibilities of DM, OM, CP and non-fiber carbohydrates (NFC) increased linearly when the CP level increased from 11.5 to 17.5 of the diet. Milk production also increased linearly with the increase of CP in the diet but no significant effects were observed for 3.5% fat corrected (FCM) milk as well as for contents of milk fat and milk CP. It can be concluded that the diet with 13.5% of CP met the protein requirements of lactating goats and appeared to be adequate for animals yielding up to 2.7 kg of 3.5% FCM per day.
feeding; goat; lactation; soybean meal
