Effect of offering three amounts of maize stover to dairy cows on intake and selection

Several studies with barley straw (e.g. Wahed et al, 1990) and sorghum stover (e.g. Osafo, 1993) have shown improvements in intake with increasing ‘ad libitum’ amounts offered. Furthermore, these studies have demonstrated that sheep and goats offered barley straw or sorghum stover in long, unprocessed form, increase intake by selecting for leaf and leaf sheath, and against stem. This phenomenon offers a simple feeding strategy to use selective feeding behaviour to improve intake and hence production. The aim of the present experiment was to study the effect of offering increasing amounts of long maize stover on intake and selection by dairy cows.Six, early- to mid-lactation Ayrshire and Friesian cows (live weight, M, 430 kg) were used in a double 3x3 Latin square design with 24-day (d) feeding periods. Cows were offered long (unchopped) maize stover at low, medium or high ‘ad libitum’ rates, i.e. 31, 59 or 87 g dry matter (DM)/kg M.d. Cows also received 3.2 kg DM/d of cotton seed cake (339 g/kg DM crude protein) in two meals at milking (0700 h and 1800 h). Stover was offered in one meal daily, at 0700 h, after collecting refusals from the previous day. Amounts of stover offered and refused were weighed daily. Samples of offered stover (0.5 kg) and refused stover (0.5 kg) were analysed for DM daily. All refused stover and 4.0 kg samples of offered stover were botanically fractionated, daily, into stem (S), leaf (L), sheath (Sh) and husk (H). Milk yield was recorded daily and cows weighed at the start and end of each period.