Supplementation of a high fibre concentrate to Jersey cows on pasture to overcome winter roughage shortages

[摘要] ENGLISH ABSTRACT:Kikuyu over-sown with ryegrass is the most widely used pasture system in the Southern Cape of South Africa. During the winter months the kikuyu component remains dormant and cows are solely dependent on the ryegrass component of the pasture. Ryegrass has a low growth rate (25 - 30 kg DM ha-1 day-1) during the winter and early spring months (June - September), resulting in roughage shortages. There are various strategies that can be adopted to overcome these shortages. Most commonly, lucerne hay is bought in. The cost (R 1800 - R 2400 ton-1), however, is high and all farms do not have the capacity to store hay in large quantities. Significant wastages occur when feeding lucerne in ring feeders or feed troughs. Silage made of surplus grass, maize or cereal crops can also be fed. Many farms do not have the implements required for ensiling and due to financial pressure, most farms are at full capacity and as such no surplus pasture is available for ensiling. The purpose of this study was to determine whether a high fibre concentrate supplement and restricted pasture intake strategy could be followed to overcome roughage shortages during the winter months.Forty eight lactating Jersey cows were blocked according to 4 % fat corrected milk yield (19.1 ± 2.2 kg day-1 (±s.d.)), days in milk (104 ± 62.7) and lactation number (4.4 ± 1.8). Cows within blocks were then randomly allocated to one of the three treatments. Treatments were defined according to the amount of a high fibre concentrate supplement that was allocated as well as the level of pasture allocated: Treatment 1 - Low concentrate treatment (LC) received 4 kg concentrate cow-1 day-1 and 10 kg DM pasture cow-1 day-1; Treatment 2 - Medium concentrate treatment (MC) received 7 kg concentrate cow-1 day-1 and 7 kg DM pasture cow-1 day-1; Treatment 3 - High concentrate treatment (HC) received 10 kg concentrate cow-1 day-1 and 5 kg DM pasture cow-1 day-1. Eight ruminally cannulated Jersey cows were used in the rumen study portion of the trial. These cows were divided into two groups of four and were allocated to the MC and LC treatments. They were used in a cross-over design, where all cows were subjected to both treatments. The metabolisable energy, crude protein and neutral detergent fibre contents of the high fibre concentrate supplement was 10.9 MJ kg-1, 145 g kg-1 and 231 g kg-1, respectively. Cows of the three treatments grazed separately, allowing for the restriction of pasture intake according to treatments specifications.The average daily milk yield and milk fat content of treatments LC, MC and HC was 16.2a, 17.3ab and 18.1b kg day-1 (P < 0.05) and 4.91a, 4.96a and 4.58b % (P < 0.05), respectively. The average stocking rate for treatment LC, MC and HC was 5.07a, 6.07b and 7.64c cows ha-1 respectively. Thirty seven percent of pasture was saved on the HC treatment strategy compared to the LC treatment. Cows gained body weight during the study at a rate of 0.62a, 0.28b and 0.27b kg day-1 (P < 0.05) for the LC, MC and HC treatments, respectively. None of the hourly rumen pH values differed between treatments LC and HC. The rumen pH of cows on treatment LC did, however, spend a longer time below pH 6.0 and pH 5.8 compared to the rumen pH of cows on treatment HC (P < 0.05). The digestibility of dry matter and neutral detergent fibre of pasture of cows on treatment LC and treatment HC at 30 hours of incubation was 82.3 and 73.5 % (P < 0.05) and 43.5 and 39.2 % (P < 0.05), respectively.The results show that winter roughage shortages can be managed by feeding higher levels of a high fibre concentrate supplement and restricting pasture intake, although a decrease in milk fat content can be expected.

[发布机构] Stellenbosch University