Effect of alkali-treated rice straw supplemented with spent tea leaf and thyroprotein on milk yield, milk composition and certain physiological parameters of dairy cows

Abstract

Thirty-six Friesian cows in mid-lactation were used to compare the effects of nine treatments. Rice straw untreated (US), or treated with 40 g NaOH in 1.5 l H 2 O kg −1 straw (TS), was given ad libitum with a concentrate mixture containing 0 or 20% spent tea leaf (STL 0 and STL 20) and with or without thyroprotein (TP 10 or TP 0). The control treatment (C) represented the standard feeding practice adopted on the farm. The NaOH treatment increased milk yield by 22%, but lowered the butterfat content of milk by 6%. Milk yield and milk composition were not affected by spent tea leaf supplementation. Thyroprotein had no significant effect on milk yield or composition during the experimental period but depressed yield significantly after its withdrawal from the diet. It increased rectal temperature by 0.5° C and heart rate by 5 beats min −1. All animals on thyroprotein lost body condition. It is concluded that alkali-treated straw is a suitable source of roughage for low yielding cows but its use in practice may be uneconomic. Spent tea leaf is a suitable source of protein for ruminants at the 8% level of substitution in the total diet DM. Thyroprotein feeding is not economical under Sri Lanka conditions and is not recommended for animals on straw diets.