It has been shown by Beever, Thomson, Cammell and Harrison (1977) that formaldehyde treatment of silage increased amino acid absorption from the small intestine of sheep by 13% and increased the amount of food protein passing through the rumen undegraded by 66% compared to sheep receiving untreated silage. This paper details the digestion of N and apparent uptake of N, non-ammonia N and amino acid N from the small intestine of Jersey cattle fed a silage made from a second growth, mixed S24 perennial ryegrass/red clover sward which was wilted for 24h and then ensiled either without an additive or with a 50/50 mixture of formic acid and formaldehyde (formalin), each at the rate of 2.2 litres/tonne of grass ensiled. The method of ensiling was by use of an Eberhardt Silopresse (Benedict Agricultural Ltd., London). Each of the three cows fed each diet was equipped with a rumen fistula and re-entrant cannulae into the proximal duodenum and terminal ileum.

Recent proposals (ARC, 1980) have clearly identified the need to supply adequate ruminally degradarle nitrogen (RDN) if rumen microbial protein yields are to be optimized and they provide a basis on which the required quantities of RDN can be calculated. However, apart from the suggestion that urea is used with only 80% of the efficiency of degraded protein N as a source of RDN in the synthesis of microbial protein, the present scheme fails to qualify the RDN composition (i.e. protein N (PN) vs. NPN) most likely to promote optimal microbial synthesis.

Cottrill, Beever and Osbourn (1982) examined the isonitrogenous supplementation of maize silage fed to growing calves with four different NPN:PN ratios in the supplement and showed a 29% increase in total duodenal amino acid (DAA) flow at the first increment of PN (fish meal). Of this increase, almost 87% could be accounted for by an increased duodenal microbial protein (DMP) flow. Higher levels of PN inclusion did not promote any further increases in DAA, despite increases in undegraded dietary protein (UDP) flow, due to a significant reduction in DMP flow. From these data, a further examination of total RDN supply and its composition in relation to MP synthesis was undertaken and the results are presented in this paper.

To make the best use of forages, it is necessary to consider the need for, and source of, nitrogen supplementation of the diet. This paper describes a study of the use of spring barley straw and other forages in the diet of the dairy heifer between 9-18 months of age, 200-300 kg live weight and required to grow at 0.5-0.7 kg per day. In the feeding trials, fixed amounts of the diets were fed.

In the first series of experiments, it was demonstrated that spring barley straw could supply up to 70% of the dry matter (DM) intake in mixed straw:concentrate diets when an adequate protein content was supplied. Thus, when fish meal was added, the required growth rates were obtained, as demonstrated in Figure 8.5.1 (Smith, Broster and Siviter, 1980), comparing favourably with estimates of energy requirements for growth (MAFF, 1975). With low straw (< 50%) diets, the response to fish meal was less.

During early lactation, when requirements for energy and protein are high, tissue protein requirements cannot be fulfilled by microbial protein alone and the opportunity arises to feed protected protein as a supplement to provide UDP which will compensate for the deficit between tissue protein requirements and microbial protein supplied by RDP.

The degradability characteristics of a wide range of grass silage types have been studied using the in sacco technique over a 48-hour period. Each silage was examined in three steers on two occasions, with pairs of bags being withdrawn at each sampling time. The steers had an average live weight of 270 kg and were fed once daily on silage, molassed sugar beet pulp and barley meal (5:3:2 on a dry matter basis), which supplied an average of 55 MJ ME per head daily.

The losses of dry matter, nitrogen, cell contents, hemicellulose and cellulose were followed. For the carbohydrate fractions, modifications of the methods of van Soest were used. For each of these components, asymptotic equations of the form: p = a + b (1-e−ct) were fitted, where a and b represent percentages of the amounts originally present in silage, c represents the proportional rate of degradation and t represents hours of incubation.

In sacco studies are at present the most practical way of estimating the rumen degradability of feeds. The commonly adopted procedure (Standard Method = SM) has a number of disadvantages, including night work and the need to select bags at each sampling time. The Complete Exchange Method (CEM), described here, has been developed to meet the need for a convenient routine procedure.

Pasture productivity was studied between August 1977 and July 1978 at five different sites in Kenya's mixed farming regions by harvesting sample plots every 2 months at a standard height (3-4 cm). The content (%) and yield (kg/ha/day) of digestible crude protein was calculated from the results of the proximate analysis using the equation: DCP (%) = 5 + 60 log CP - 0.33 CF. The results were subjected to standard methods of variance and covariance analysis using precipitation as the covariate, since rainfall yields differed considerably among sites and seasons.

Gamma amino butyric acid (GABA) is a food intake depressant (Morley, 1980) and is quantitatively a significant nitrogenous constituent in silage (Oshima and McDonald, 1978). When maize silage extracts were infused into the rumen of sheep, it was shown that short-term feed intake could be depressed but this effect was attributed to high rumen osmolality (Phillip, Buchanan-Smith and Grovum, 1981) The purpose of the present experiments was to determine whether GABA and low dry matter lucerne silage extracts could depress food intake in sheep.

During the ensiling process, even under good conditions, some of the plant proteins are broken down to soluble nitrogen compounds which are less well utilized by the ruminant. Formaldehyde, alone (Wilkins, Wilson and Woolford, 1974) or in conjunction with formic acid (Wilson and Wilkins, 1980), has been used as a silage additive to protect proteins against degradation during ensilage. Glutaraldehyde (Mangan, Jordan, West and Webb, 1980) has been suggested as an alternative due to its rapid fixing action and in this experiment it was compared with formaldehyde.

The use of silage additives containing lactic acid bacteria and enzymes to promote a rapid homolactic type fermentation has met with some success in the United States but the little evidence available (see Burghardi, Goodrich and Meiske, 1980) suggests that, for grass silages, the value of this type of additive is limited. However, in laboratory silos, inoculation with lactic acid bacteria has been shown to be effective in reducing proteolysis (Carpintero, Henderson and McDonald, 1979).

The recent availability in the UK of a commercial product containing a lactic acid bacteria inoculum and the non-toxicity and ease of application of this product prompted this investigation, which describes the assessment of a silage prepared with this type of additive in comparison with a well characterized additive, formic acid.

The object of the experiment to be reported was to determine the extent to which intake and eating behaviour are influenced by differences in the ratio of nitrogen (N) to water soluble carbohydrates (WSC) in the feed and the liquid phase of boli obtained from oesophageal fistulae. Four feeds were chosen as being likely to cover a range of N to WSC ratios in the liquid phase; these were frozen lucerne, lucerne silage, grass silage and grass silage treated with formaldehyde (46 g/100 g crude protein).

Free ranging cattle in the Accra Plains of Ghana have an almost all grass diet during the rainy season when lush grass abounds (Fianu, 1966). Depending on the ecological status of the grassland, the prominent species include Andropogon gayanus, Brachiaria falcifera, Panicum maximum, Schizachyrium schweinfurthii and Vetiveria fulvibarbis. On bush fallows, grasses of lower successional status, e.g. Chloris and Digitaria spp., are grazed.

At the start of the rainy season (March-April), the young herbage may contain as much as 2.8% N. As the plant matures, however, the N content declines rapidly below critical levels, e.g. 0.95-1.3% at 18 weeks (Fianu and Winch, 1980) and 0.6-0.8% at 38 weeks (Lansbury, Rose Innes and Mabey, 1965).

Such mature grass is burnt in the dry season to induce a more nutritious flush but hard grazing and slashing also induce equally nutritious regrowth (Fianu and Winch, 1980).