Studies in the use of feedblocks for ruminants

Over recent years the 'self-help' feedblock system of giving additional nutrients to ruminant animals has become increasingly popular. This has principally been due to the convenience and potential labour saving attributes of this system of feeding. A series of claimed nutritional advantages for 'self-help' feedblocks have also been proposed which are not possible with traditional 'hand-feeding.' It has been the objective of this thesis to evaluate the validity of these claims and assess the suitability or otherwise of feedblocks in ruminant husbandry. Two different philosopihies of feedblock use were recognised. The original feedblock concept was essentially a low intake product as a supplement for poor quality roughages; the majority of feedblock available in the U.K. fall into this category. Recently, higher intake feedblocks have been developed with formulations more similar to conventional concentrates, these aim to substantially increase ME) intake directly via the block ingredients per se, as well as indirectly ma increased roughage utilisation. In this thesis they have been referred to as substitute feedblocks. Considerable emphasis has been placed in this thesis on the individual intake of feedblocks and other supplementary foodstuffs using chromic oxide as a faecal marker. In Section 1 a comparative assessment of individual variation in feedblock intake relative to giving equivalent amounts of DM as concentrates in troughs or cobs spread on the ground was conducted. In virtually all circumstances individual variation in feedblock intake was greater than for 'hand-feeding' for both sheep and cattle, which is the converse of what is often claimed. The use of continuously available feedblocks did not appear to reduce the number of individuals in a group which completely refused to consume feedblocks. In older sheep, dental status appeared to be a major contributory cause to the magnitude of individual intake variation. In Section 2 it was shown that feedblocks could not be relied upon to provide a consistent pattern of intake over various periods of time. A wide variety of factors were identified which could potentially contribute to the non-uniformity of total feedblock intake by a group of animals. These could be categorised as factors inherent in the blocks per se, the stock consuming them and other environmental factors, such as climatic variables and managerial influences. In Section the relationship between feedblock consumption and individual nutrient requirements was examined with respect to protein, energy and magnesium. There was no evidence to suggest a relationship between feedblock intake and physiological need as is sometimes claimed to be the caseo Multi-gravid ewes did not consume more feedblock than either single or non-pregnant ewes in late pregnancy. Animals seemed to consume less feedblock when alter-native more palatable foods were available e.g. spring grass, and vice versa. This makes the use of feedblocks as carriers of supplementary' magnesium during the critical post-turnout periods ineffective becavise of the very low and. unreliable level of intake. In Section 4 the effect of the feedblocks and their ingredients on the utilisation of roughages, was examined. There did not appear to be any noticeable advantage of giving NPN frequently compared with once daily during a 24-hr period as may occur with feedblocks, in terms of increased voluntary straw intake and digestibility. In other experiments the increase in ME intake from improved roughage utilisation arising through supplementation of roughages with feedblocks was generally small and unlikely to create a plane of nutrition much in excess of the maintenance needs of the animal. One of the major ingrediants of a particular feedblock (PJC feed, a residue of the distillery industry) has been widely claimed to enhance roughage utilisation by considerable amounts. This was not found to be the case in this thesis and indeed may have had a negative effect on roughage utilisation. It is concluded that feedblocks have a useful role to play in animal husbandry, particularly in extensive hill systems of production. However due to their high cost and love energy content relative to alternative compound foodstuffs, their use can seldom be justified where it is possible to give cheaper concentrates, unless considerable saving of labour, results