Substitution of ryegrass pasture with a high fibre concentrate supplement to grazing Jersey cows to overcome winter roughage shortages

The low growth rate of ryegrass pasture in the southern Cape area of South Africa during the winter months results in a gap in the fodder flow plan. The objective of this study was to determine whether roughage shortages during the winter months could be overcome by the substitution of pasture with a high fibre concentrate (HFC). This was determined by feeding varying levels of the HFC to cows grazing ryegrass pasture. Treatments were: Low concentrate (LC), where each cow received 4 kg concentrate and 10 kg dry matter (DM) pasture per day; medium concentrate (MC), where each cow received 7 kg concentrate and 7 kg DM pasture per day; high concentrate (HC), where each cow received 10 kg concentrate and 5 kg DM pasture per day. Forty eight lactating Jersey cows were blocked according to days in milk, lactation number and 4% fat corrected milk yield, to determine the effect of treatments on production. Cows within blocks were randomly allocated to one of three treatments. Eight ruminally cannulated Jersey cows were randomly allocated to the LC and HC treatments in a cross-over design, to determine the effect of treatments on rumen health. The metabolisable energy (ME), crude protein (CP) and neutral detergent fibre (NDF) contents of the HFC was 10.9 MJ/kg, 145 g/kg and 231 g/kg, respectively. Cows in the three treatments grazed separately, allowing for the restriction of pasture intake according to treatments specifications. The ruminally cannulated cows grazed with the production study cows, in their respective treatments, throughout the study. The mean daily milk yield was higher for treatment HC (18.1 kg/d) than for treatment LC (16.2 kg/d), while treatment MC (17.3 kg/d) remained intermediate. The mean milk fat content was lower for treatment HC (45.9 g/kg) compared to treatment MC (49.6 g/kg) and treatment LC (49.2 g/kg). Rumen activity of cows in the HC treatment was inhibited. Rumen pH of cows in the HC treatment spent a longer time below pH 5.8 (7.43 h) compared to cows in the LC treatment (6.24 h). Pasture NDF degradation coefficient after 30 h of incubation and rumen acetate concentration was higher for the LC treatment (0.42 and 75.11 mM/L) than for the HC treatment (0.39 and 64.96 mM/L). It was concluded that restricting pasture intake and feeding higher levels of a HFC is a viable option to overcome pasture shortages during winter months.