Hovell et al. (1986) proposed that degradation characteristics of forages, as measured in nylon bags, may have useful application in predicting voluntary intakes. They reported intakes of four hays by sheep were more closely related to the potential degradability of forage dry matter (DM) than to in vivo The present work was undertaken to examine these relationships with forages and with both young growing cattle and sheep.

Seven forages were prepared with the objective of providing material wide range of voluntary intake. The forages were:

• (i)WS, wheat straw

• (ii)AWS, round-baled WS wrapped in 4 layers of overlapping plastic sheet (Silawrap; Volac Ltd), injected with 32% aqueous ammonia at the rate of 40kg/1000kg DM

• (iii)H1, first cut ryegrass hay

• (iv)H2, second cut ryegrass hay from the same field as (iii)

• (v)S2, 50% DM silage, baled and wrapped with Silawrap, prepared from the same crop as H2

• (vi)ES2, the same crop as S2 sprayed with a mixed enzyme preparation (Deezyme, Finnish Sugar Company Ltd.) at 0.81/tonne immediately before baling and wrapping with Silawrap

• (vii)AS2, S2 treated with aqueous ammonia in the wrapped bale as for AWS. All forages were fed in the long form except WS which was coarsely chopped through a straw chopper without any retaining screen into approximately 7cm lengths.

Ability to predict accurately the intake of digestible nutrients by ruminants is of great interest. The feed intake can be limited mainly by the amount of undigested residue remaining in the rumen. Ingested feed disappears from the rumen in two ways: through digestion and through passage. So, forages with easily degraded cell-walls, may promote faster rates of digestion and passage and allow the animal to consume more feed (Hovell et al., 1986).

The objective of the present study is to determine the rate and extent of rumen degradation of various hays “in situ” and to evaluate the ability to predict the voluntary intake from these rumen degradation characteristics.

Eleven sun-cured hays from three cultivars (alfalfa, red-clover and vetch-cereal), two sown grasslands (grass-clover mixture and mixed grass sward) and six permanent meadows were used to study the relationship between some rumen degradation characteristics and the voluntary dry matter intake (VDMI) by sheep.

It is well known that the process of ensiling forage has a deleterious effect on intake. It is likely that the soluble constituents, produced during the fermentation, are responsible for a major part of this effect, although studies of infusion of constituents into the retlculo-rumen have shown that there Is no simple post-ingestive mechanism. Studies on feeding behaviour have shown that ruminants eat silage more slowly than unensiled forage and from this it has been concluded that ruminants may be aversive to the taste, smell or sight of silage. The question, however, of whether is this aversion to silage could explain reduced intake, when silage is the only food offered, remains. To provide a more definitive test of this question, soluble constituents were added to a high-quality low dry matter silage in combinations and levels typical of those reported in the literature. The effects of these additions on intake by sham-fed sheep was measured.

Much interest has been shown recently in synchronising the supply of nitrogen and energy yielding substrates to microorganisms in the rumen. It is argued that when supplies are synchronised, rumen fermentation will be more efficient and improved performance will result. Previous trials with beef cattle at Nottingham and elsewhere have investigated the effect of single protein sources (e.g. fishmeal, soya bean meal) on rumen fermentation and performance. However, the majority of silage-fed beef cattle in this country receive supplementary protein in compound feeds. It is possible that the digestion of the carbohydrate portion of the compound feed could compete with silage digestion for nitrogen supply. Therefore, degradation of silage should be investigated in animals actually fed on the compound feeds, rather than just considering the degradation of the protein components in a compound. A trial was carried out to investigate the influence of protein source in compound feeds on rumen fermentation and performance in beef steers given silage.

Spreadsheet computer programs provide a two-dimensional matrix into whose cells numbers and text can be placed and manipulated. A cell can also contain a formula which causes a calculation to be performed on values In other cells and the answer shown on the screen. Graphs can be produced from specified ranges of values in cells. Thus a spreadsheet is well suited to financial accounting. Modelling biological systems has often been thought to be complicated and to involve writing a computer program. Simulation languages take away much of the detailed programming effort but still require the user to learn the syntax and capabilities of the language.

The aim Is to develop a simple model of voluntary feed Intake by the lactating cow using a spreadsheet program. The basis is the model described by Forbes (1988) simplified for a complete feed rather than forage and concentrates but with the level of intake determined by both metabolic and physical factors rather than by which ever of those two Is the lower.

There Is considerable evidence that end products of carbohydrate fermentation and distension of the rumen are involved in limiting intake in ruminants. Intraruminal Infusion of acetate or propionate (Montgomery et al., 1963) distension of the rumen (Campling and Balch, 1961) depressed hay Intake in cattle It is unlikely, however, that any single factor is entirely responsible for terminating feeding but that the effects of the changes that occur In the rumen during a meal, such as production of SCFA, changes In pH, osmolality, rumen distension, are Interpreted as a whole to induce satiety.

In a previous study with dairy cows distension of the rumen together with Intraruminal infusions of sodium acetate and sodium propionate had additive effects on hay Intake (Anil et al, 1987) and a similar experiment has now been carried out with silage.

It is important to understand the factors which limit forage intake in ruminants. Most work carried out on sheep has now been extended to the dairy cow. The effects and possible roles of the short chain fatty acids In the control of forage intake in the dairy cow, in particular, hay intake have already been reported (Mbanya, 1988). One of the factors in question is propionate which depresses intake when given intraportally in sheep, but hay intake in the dairy cow was not affected by intraruminal propionate. The aim of this study was to test the role of propionate in the control of silage intake which has economical importance in the dairy industry.

Five rumen fistulated Friesian cows in early lactation (mean yield 25 kg/day) were used in a Latin-square experiment and individually fed grass silage (DM: 229g/kg; CP: 158g/kg DM; MAD fibre = 349g/kg DM; ether extract: 42g/kg DM; ash: 96g/kg DM) ad libitum plus 6 kg of concentrate fed twice daily. 3h intraruminal infusions of the following were made on different days: Control (no infusion), 4,6 and 8 moles of sodium propionate in 41 water. Silage intake was measured during the 3h and for 2h post-infusion.

When autumn calving dairy cows are offered low levels of compound supplement, milk production and subsequent profitability depends not only on silage quality but also the quantity of silage consumed. Silage quality and palatability are undoubtably related but when grass silage contributes in excess of 75% of total dry matter intake, some silages which, to date, would be defined as being of good quality, appear comparatively less palatable than their chemical analyses would initially suggest, To enable accurate ration formulation in dairy feeding systems based on ad libitum grass silage, a prediction of silage dry matter intake is essential. In this experiment nine silages, all with a high digestibility and crude protein content, but varying in their fermentation characteristics, were offered ad libitum to individually fed October calving dairy cows receiving 3 kg of a 160 g/kg crude protein cereal based compound supplement daily.

Moving onto silage aftermath is an integral part of the 1.2.3 grazing system. In this system two thirds of the grass area are conserved for first cut silage while the other third is grazed. Between first and second silage cuts the silage aftermath is grazed while the original grazing area is closed for silage. After the second silage cut the whole area is grazed. In this trial the contribution of silage aftermath to the system was investigated by comparing the intake and performance of young cattle moved onto aftermath in raid-season with that of similar animals grazing the same sward continuously.

Thirty-two Hereford x Friesian and thirty-two Limousin x Friesian steers (mean liveweight 193 ± 16.8 kg) were allocated to either Treatment C, grazed continuously on the same sward throughout the experiment or Treatment S where the animals were turned onto silage aftermath in mid-season. Treatments were replicated twice and balanced for breed and liveweight of animals.

Backfat firmness is an important aspect of pig carcass quality. National values for backfat thickness have been falling annually whilst softer backfat has been increasingly reported by the meat trade. The problems of soft backfat have been well documented: it is unsightly, difficult to slice and prone to separation (MLC, 1983). All these factors can lead to downgrading of the product and consequent financial loss to the processor. Leanness of pigs is one cause of softer backfat and unsaturation of the backfat lipid, especially by the exogenous fatty acid linoleic acid (C18:2), is also an important factor (Prescott, 1988). The present study investigates the effect of backfat thickness and consequent chemical composition on fat tissue quality and considers some histological aspects of the soft fat problem.

Forty-six NPD gilts were reared to obtain carcasses having a wide range of backfat thickness values at a slaughter live weight of 90 kg. Two diets containing different levels of linoleic acid and energy but the same ratios of linoleic acid to energy were used to achieve this.

In a recent experiment using the same improved genotype, pigs over the liveweight range 25 to 120 kg were found to have modest voluntary energy intakes (Chadd and Cole, 1988) particularly when compared with former intake prediction equations. It follows that the response of such pigs in terms of voluntary feed intake behaviour when provided with diets differing in energy concentration may have also changed. Diets that are formulated to be low in energy density and therefore bulky in nature are likely to represent more of a limitation to voluntary feed intake than previously. Former experiments designed to examine the pig's ability to adjust feed intake in order to maintain a constant energy intake have produced results varying from complete to incomplete compensation.

A study was undertaken to examine the response of a modern genotype in terms of voluntary feed intake, digestible energy (DE) intake, growth performance and associated carcass characteristics, when offered a range of dietary energy concentrations ad libitum and taken to a heavy slaughter weight.

Skatole and indole, compounds formed in the large intestine by microbial breakdown of tryptophan, are associated with carcass taint (Hansson et al., 1980). The present work involved the development of a method for detecting the absolute values of the analytes in fat and faeces. The effect on faecal excretion of skatole was also examined following infusion of skatole directly into the caecum. Finally as substrate effects the type and extent of fermentation in the large intestine, different diets were fed and the corresponding faecal and fat skatole levels were determined.

Skatole analysis involved homogenising adipose tissue with methanol and removal of fat by cooling and filtering. Solid phase extraction columns concentrated the analytes to produce samples which gave good resolution by gas liquid chromatography (Porter, Hawe and Walker, 1989). Due to higher levels of skatole in faeces, no concentrating phase was required before detection.

Good husbandry practices for ad libitum feeding of finishing pigs have traditionally provided between 50-75 mm trough space per pig. However, following the success of commercial pig producers in Denmark and The Netherlands in using single-space feeders, these feeders are becoming increasingly popular in the UK. If pig performance is unimpaired, the saving in floor area required for feeders may provide an opportunity to increase stocking rate per pen.

Two hundred and sixteen entire male and female pigs of about 30 kg liveweight at 12 weeks of age were blocked by sex and weight to groups of 12 and allocated at random to one of 3 treatments:

1. Ad libitum feeding with one single-space feeder (occupying 0.326 m2 floor area).

2. Ad libitum feeding with 2 single-space feeders (occupying 0.652 m2 floor area).

3. Ad libitum feeding with one multi-space feeder (occupying 0.439 m2 floor area).

Pigs were housed in an environment controlled house managed on a fully-slatted slurry system with no bedding used. The single-space feeders (QE Fivestar c) incorporate a 5 starred wheel which pigs operate with their snouts to drive an auger which dispenses a metered amount of feed from a bulk hopper.

The modern genetically-improved female pig reaches first mating with low levels of back fat compared to the female bred in previous decades. Increasingly too, gilts have been bred at younger ages and lower weights and the effects of these management changes are unclear. It has been questioned whether the modern gilt is under greater physiological stress especially when subjected to low feeding levels, which could influence reproductive efficiency. The objectives of the trial reported here were to compare the reproductive performance of gilts given different feeding regimes during rearing and pregnancy in order to produce a range in body weight and back fat.

The trial was designed as a 2 x 3 factorial experiment. Gilts from a Large White x Landrace crisscross breeding programme, blocked for genotype, were first allocated to one of two treatments from 10 to 25 weeks of age. Gilts were group housed and fed on a age-based scale rising to either 2.25 kg/d (L) or 2.70 kg/d (H). At 25 weeks of age, gilts with defects of teats or gait were discarded.

The present experiment was designed to investigate the influence of variations in energy intake during both pregnancy and lactation on changes in body weight, backfat and body composition of the sow after four parities and the extent to which these may have influenced overall sow productivity.

The experiment has been designed in a 2 x 2 factorial arrangement involving two levels of feeding during both pregnancy and lactation. The feeding levels in pregnancy were planned to produce net maternal body weight gains of 30kg (H) and 10kg (L). At each of these, two feeding regimes were applied during a 3 week lactation, one being at a conventional level (H) and the other 25% below this (L). The experiment thus involved four groups of animals given different levels of feeding during both pregnancy and lactation, designated: High-High (HH), High-Low (HL), Low-High (LH), Low-Low (LL). No creep feed was provided to the piglets during the suckling period. At the start of the experiment the gilts weighed 115kg live weight with a backfat thickness at the P2 position of 18mm. They remained on the same treatment throughout four parities and were slaughtered after weaning their fourth litters when the carcasses were retained for analysis. Data are presented from 66 sows; 17(HH), 17(HL), 16(LH), 16(LL).

The use of fibrous by products in diets for pregnant sows offers possible economic and welfare advantages. To correctly determine their nutritional value it is essential to know the relative roles of enzymatic digestion and fermentation. Techniques developed previously for this purpose have involved the use of surgically modified animals, making them costly and limiting their widespread use. This experiment was designed to investigate the possibility of using short term administration of bacteriostatic levels of antibiotics for this purpose.

Twenty Landrace x Large White pregnant sows were individually housed in unbedded stalls and allocated to one of five dietary treatments with differing levels of the two fibrous by-products - distillers dark grains (DDG) or dried, unmolassed sugarbeet pulp (SBP)

• 1)Basal diet (BAS) 850g/kg barley, 120g/kg soyabean meal,30g/kg vitamins and minerals

• 2)70% diet BAS, 30% distillers dark grains (30DDG)

• 3)40%diet BAS, 60% distillers dark grains (60DDG)

• 4)70%diet BAS, 30% unmolassed sugar beet pulp (30SBP)

• 5)40% diet BAS, 60% unmolassed sugarbeet pulp (60SBP)

Fats are important but variable energy-yielding ingredients in diets for broilers. One of the factors that may affect the dietary energy value of fats is the proportion of free fatty acids which, together with rate of inclusion of fat and the age of the bird, must be considered in fat evaluation. The current experiment was designed to investigate the effect of free fatty acid content of tallow on the apparent metabolisable energy values for broilers.

Tallow and tallow acid oil (Table 1) were obtained for evaluation. Tallow (A) of free fatty acid content 138.4 g/kg was hydrolysed to produce a fat (E) of free fatty acid (FFA) content 952.1 g/kg. Fat A and B were blended in the proportions A75:B25, A50:B50 and A25:B75 giving fats of 341.5, 545.3 and 748.7 g/kg FFA respectively which were included at rates of 40 g/kg, 80 g/kg and 120 g/kg at the expense of the energy-yielding ingredients. The 16 experimental diets - basal (Table 2) together with 15 containing fats - were evaluated with Ross 1 broiler chicks of 1.5 weeks (5 replicates of cage of 2 birds) and 7.5 weeks of age (5 replicates of cage of 1 bird).

British Landrace (BL) is used widely as a dam breed in producing crossbred sows for commercial pig production in Zimbabwe. This study was undertaken to evaluate the performance of BL under current level of management in Zimbabwe and to make recommendation for improvement of productivity.

The records for this study were obtained from a nucleus/multiplier farm. The data included 720 litters from BL sows over the five year period 1983 - 1987. The reproductive traits analysed, number born alive (NBA), number weaned (NW), total litter weight at birth (TLWB) kg, at weaning (TLWW), age at first litter (AFL) days, days weaning to effective service (DWES) and farrowing interval (FI) days, were from both pure and crossbred matings. The performance data, daily gain (DG) and food conversion ratio (FCR) between 35 - 86 kg and k backfat thickness (BF) at 86 kg, were from 620 performance tested BL pigs. The data were analysed by least-squares procedures. The fixed effect included in the analysis of reproductive traits were the sire breed of the litter, the dam parity and the year and season of birth of litter. The effects considered for the performance data were the year and season of performance test and the sex. The season according to month of birth of litter, farrowing, rebreedlng or performance test was classified as cold (April - July), dry (August - November) or rainy (December - March). For all the traits, typical model included the above fixed effects and two-way Interactions.

Farrowing accommodation is currently provided by different variants, or designs, of the farrowing crate. The farrowing crate, which is intended to reduce piglet mortality and give the piglets good access to the sow, severely restricts her movement and activity. The welfare codes (Ministry of Agriculture, Fisheries and Food, 1983) recommend that pigs should have ‘freedom of movement’ and ‘opportunity to exercise most normal patterns of behaviour’. There is, therefore, a need to develop farrowing facilities which allow the sows freedom of movement and permit greater activity but which also maintain or improve economic performance.

A sow which is permitted greater freedom of movement in the late stages of pregnancy would, within the pen, determine her own farrowing site. This benign approach cannot easily be reconciled to the production process which seeks to reduce uncertainty and maximise the use of resources. In this instance, the provision (creep, heat source) made for the litter. Thus it is important to be able to identify the sows’ preference for such a site and to identify features which attract the sow. This study examined some of the structural and environmental preferences for a farrowing site of sows and gilts, and examined behaviour at their chosen site.

At farrowing time, sows are normally confined in barren environments which prevent the performance of normal behaviour patterns. It has been argued that both the sows welfare and productivity may suffer as a result of these conditions, (Vestergaard and Hansen, 1984). Investigations into the feasibility of an alternative system in which the sows are not restricted have therefore been initiated. The main objective of the present study was to establish design criteria for voluntary accessed farrowing pens which will attract sows by providing them with their preferred environmental requirements.

Previous observations, not reported here, were made of the pre-farrowing behaviour of sows housed individually in large pens which contained a deep sand floor and a straw dispenser. All the sows showed nest building behaviour which culminated in the production of a recognisable nest. Typically they had the following characteristics: a shallow depression; a straw lining and a nest rim which formed a low barrier around the nest. The experiments described here were designed to establish the preferences of the peri-parturient sow for preformed lying areas which incorporated these features.