Effects of Cassava Chips used as Non-structural Carbohydrate Source for Lactating Dairy Cows Fed Urea-treated Rice Straw

Abstract

Twenty-four multiparous Holstein cows in early and mid-lactation, an average weight of 382 ± 12kg and were blocked according to days in milk (DIM) into two groups (30 - 75 DIM and 76 - 120 DIM). Allcows within each group were randomly allocated to one of the four experimental diets accordingly to arandomized completed block design (RCBD) with six replications per treatments. The dietary treatmentswere concentrate based, containing 15, 30, 45 and 60% of cassava chips (CC) in concentrate (18%CP)replacing rice bran. Cows were offered diets as consisted of 60% concentrate and 40% urea-treated ricestraw (UTRS).

Urea-treated rice straw (UTRS) and total dry matter intakes increased (p<0.001) with increasinglevels of CC in concentrate up to the 45%CC, thereafter both UTRS and total dry matter intakes weresignificantly decreased (p<0.001) where cows fed the 60%CC in concentrate. Total non-structuralcarbohydrate (NSC) intake increased linearly (p<0.001) and quadratically (p<0.001) with increasing levelsof CC in concentrate (28.9, 32.2, 35.6 and 38.2% of DMI intake). Digestible nutrients intake, milk yieldand milk compositions (fat, protein, solid-not fat, total solid) in terms of yield and concentrationquadratically (p<0.01) increased with increasing levels of CC in concentrate up to the 45%CC, thereaftersignificantly decreased (p<0.001) where cows fed the 60% CC in concentrate. The optimal level of cassavachips in a lactating dairy cow diet is suggested as being between 30 to 45% of cassava chips or 32.2 to35.6% NSC intake in the concentrate when fed with UTRS as roughage.

Keywords : Cassava Chip / Dairy Cattle / Non-structural Carbohydrate / Urea-treated Rice Straw