The utilization of cereal straws are limited by their low nutritive value and bulkiness which prevents ruminants from consuming sufficient to meet their nutrient requirements. However, recently there has been interest in furthering the use of cereal straws as food for ruminants. The main objective of the present study was to provide information on the degradability of straw for cereal varieties recently included on the SAC recommended lists. A further objective was to examine the between farm variation in degradability of straw for individual cereal varieties and to assess how this may be affected by management practices in the field.

Forty two samples of straw comprising three varieties of winter wheat, four varieties of winter barley and seven varieties of spring barley straw were collected from farms in and around the North East of Scotland. The potential degradabilities of the straw was measured using three different techniques; 1) the nylon bag technique (0rskov, 1985); 2) in vitro analysis, and 3) near infra red analysis (NIR).

The effects of methods of processing soyabean meal (SBM), and low (LRSM) and high (HRSM) gluco-sinolate rapeseed meals on rumen degradability (DG) of dry matter (DM) and nitrogen (N), were determined by the nylon bag method in experiments of Latin Square design with 4 rumen-fistulated heifers. Rumen fractional outflow rates (FOR) for untreated SBM, LRSM and HRSM were determined by the chromium-mordant method in 2 heifers. Effective rumen degradabilities (EDG) for rumen incubation times of 24 h were calculated from DG and FOR.

Methods of processing were formaldehyde (FT, 0.8g HCH0/I6g N), heat (HT, 110°C for 2 h) and untreated (UT). Heifers were given a basal diet of hay (0.55 of DM intake) and mineralized barley with LRSM (0.45 of DM intake). The diet was offered twice a day at 08.00 and 16.00 hours. An adaptation period of four weeks preceded the experiments.

In an experiment of 3 x 3 Latin Square design, 3 heifers each fitted with rumen and simple T-piece duodenal cannulae were used to determine the effects of method of processing soyabean meal (SBM), and low (LRSM) and high (HRSM) glucosinolate rapeseed meals on rumen degradabilities (RD) and intestinal digestibilities of dry matter (DM), nitrogen (N) and organic matter (0M) using a mobile nylon bag technique.

Heifers were given a basal diet of hay (0.55 of DM intake) and mineralized barley with LRSM (0.45 of DM intake) to provide a ME intake of > 2 x maintenance. The diet was offered twice a day and a period of four weeks was allowed before the experiment. Methods of processing were formaldehyde (FT, 0.8 HCH0/l6g N), heat (HT, 110°C for 2 h) and untreated (UT). After processing the feedstuffs were ground and 1g samples were placed in sealed nylon bags (3-5 x 5.5 cm). The bags were placed in a plastic mesh cylinder and incubated in the rumen for 0, 12, and 24 hours.

NIRS is now a familiar tool in the assessment of forage and feedingstuff quality. Recently NIRS has been applied to the direct prediction of in vivo organic matter digestibility (OMD) of grass silages (Barber et al 1990) and cereal straws (Givens et al 1991).

The Agricultural Development and Advisory Service (ADAS) has been using NIRS to predict the in vivo OMD of oven dried silages on a routine basis since 1989, and it has proved to be reliable, accurate and rapid. In addition to OMD, crude protein (CP), and neutral detergent fibre (NDF), are routinely predicted by NIRS, leaving pH, ammonia, dry matter and ash still to be determined by wet chemistry methods.

Previous studies (e.g Rogers et al., 1985; Estell and Gaylean, 1985) have shown that addition of sodium (Na) as NaHCO3 or NaCl to conserved feeds increases rumen pH, fluid dilution rate, digestibility of dietary nutrients and rumen cellulolysis. Little research has involved the effect of Na supplementation on cattle fed fresh herbage.

The objective of the present experiment was to examine the effects of 0 (Nil), 32 (Low), 66 (Medium) and 96 (High) Kg Na ha-1 yr-1 applied as fertilizer to zero-grazed perennial ryegrass pasture, on rumen digestion and feed and water intakes.