Chiang Mai Journal of Science

Twenty-four lactating Holstein cows in early and mid-lactation, an average weight 475 + 27.7 kg and were according to days in milk into two groups of block (30-65 days and 80-120 days) of six cows each. All cows within each group were randomly allocated to one of the four experimental diets accordingly to a randomized completed block design (RCBD) with six replications per treatments. The dietary treatments were concentrate based, containing 0, 10, 20 and 30 % of sunflower seed meal (SSM) in concentrate replacing soybean meal. Cows were fed ration consisted of urea-treated rice straw (UTRS) and concentrate at ratio 40 to 60, ad libitum for all treatments. Urea-treated rice straw increased linearly (p<0.01) with increasing level of SSM. Similarly, total dry matter intake (DMI) also increased linearly (p<0.01) with increasing level of SSM (16.8, 17.1, 17.2 and 17.3 kg DM, respectively for 0, 10, 20 and 30 % SSM), and those of SSM dietary treatments were significantly higher (p<0.01) than the control treatment (0 % SSM). Dry matter digestibility increased linearly and quadratically (p<0.01) with increasing level of SSM. Similarly, OM, CP and NDF digestibility increased linearly and quadratic (p<0.01) with increasing level of SSM. Milk yield increased linearly (p<0.01) with increasing level of SSM (15.34, 15.39, 16.39 and 16.53 kg, respectively for 0, 10, 20 and 30 % SSM). Total UTRS, dry matter digestibility, OM, CP and NDF digestibility, milk yield, milk fat content and total solid, milk protein yield and solid-not fat content all increased linearly with increasing SSM levels.