Grazing by steers at different sward surface heights on extensive pastures: A study of weight gain and fat deposition

Live weight gain of steers grazing at three different target sward heights, Low (3-6 cm), Medium (6-10 cm) and High (>10 cm), together with carcass fa t deposition, were studied during two grazing seasons. Sward height was mea sured with a sward stick. The grassland consisted of seminatural grazing ar eas mixed with previously cultivated areas. Animals grazed continuously wit h small adjustments in animal numbers (year 1) or pasture area (year 3) to maintain award height within the target for each treatment. The recorded av erage sward heights were 4.7, 6.8 and 11.1 cm for pastures on treatments Lo w, Medium and High, respectively. The animals weighed approximately 440 kg at the start of the grazing season and went directly from pasture to slaugh ter at the end of the experiment. No differences between years were found a nd data from both years were thus pooled, giving a total of 50 steers of th e Swedish Red and White breed in the data set. Over the whole grazing seaso n, the average daily live weight gain of animals on treatment Low (0.43 kg day(-1)) was significantly (P < 0.001) lower than on treatments Medium and High (0.77 and 0.83 kg day(-1), respectively). The animals on treatment Low had a significantly (P < 0.05) lower proportion of abdominal fat at slaugh ter compared with animals on treatment High (43 vs 52 g kg(-1) carcass weig ht) and the carcasses had a thinner layer of subcutaneous fat compared with the other treatments (2.4 mm vs 2.9 and 3.0). The main conclusion of this experiment is that continuous gazing of these pastures throughout the seaso n at a sward surface height below 6 cm cannot be recommended as it leads to lower animal productivity. Other management strategies need to be develope d for seminatural pastures that can comply with environmental goals without lowering animal productivity.