The influence of feeding strategy on growth and rejection of herbage around dung pats and their decomposition

Abstract

Fresh cattle dung from four farms with different feeding strategies was used to create artificial dung pats in a continuously grazed pasture in order to compare the rejection of herbage growing around the pats, the effect on undisturbed herbage growth under cages and pat decomposition. The first farm was an extensive organic farm (ORGE) with young steers grazing on a biodiverse sward. The second was an intensive organic farm (ORGI) with dairy cattle grazing on a grass/clover sward during the day and fed low-protein forages indoors. The third dung used was from an integrated farm (INT), where the feeding strategy was aiming for high dung quality by including straw in the diet. The fourth examined dung was from a conventional farm (CONV) aiming for a high milk production per cow, where fertilized grazed grass was the main component of the diet. A human smell test was performed to rank the odour of the four dungs.

After 6 weeks of continuous grazing with dairy cattle, herbage yield around INT pats tended to be lowest, whilst undisturbed herbage yield in and around caged INT pats was highest (P<0·05). Therefore, it could be concluded that rejection was lowest for INT. The CONV pats gave highest rejection (P<0·05). However, herbage yield around the dung pats under grazing showed no significant correlation with both the human smell test and the contents of total-N and sugar in the rejected herbage.

The feeding strategy had a significant effect on the decomposition of dung pats under the cages. After 6 weeks, the most liquid and least fibrous dung (CONV) showed highest decomposition (P<0·05), whilst decomposition of the most solid and fibrous dung (ORGE) tended to be lowest. However, no relationship was found between the decomposition of dung and the rejection of herbage around the dung pats.

When combining a number of parameters determined in the experiment and comparing them using index figures for dung quality in terms of rejection, herbage growth and decomposition, the index figures of ORGI (102) and especially INT (113) were above average (100), while those of ORGE (94) and CONV (90) were below average. The difference between ORGI and INT might be explained by the addition of straw to the diet in the latter. The study showed that there are possibilities to improve dung quality by altering feeding strategy.