The transition period (last four weeks of pregnancy and the first four weeks of lactation) is the most traumatic period in the annual cycle of the dairy cow. It is physiologically and nutritionally stressful, particularly as food intake is reduced, especially in the last few days prior to calving, whilst nutrient demands for foetal growth and initiation of milk synthesis are increased. As the genetic merit of the national herd has increased considerably in the last ten years, improved nutritional management of cows during the transition period may be more important in reducing or preventing the cumulative loss of body condition, particularly in early lactation. The present study was undertaken to evaluate the effect of level of concentrate intake in late gestation on subsequent milk yield and composition.

The Dutch DVE/OEB protein evaluation system (Tamminga et al., 1994) gives predictions for the concentration of whole true protein digested in the small intestine (DVE) in cattle feeds, but not for the concentration of single amino acids. Therefore, new standard methods has been introduced for the prediction of true methionine and lysine digested in the small intestine (DVmet and DVlys, respectively) in cattle feeds based on the principles of the calculation of DVE (van Duinkerken and Blok, 1998). These methods give the opportunity to select particular feeds and concentrate ingredients in order to manipulate the concentration of DVmet and DVlys in diets and compound concentrates. However, in the Netherlands, there are no recommendations for DVmet and DVlys in dairy cow rations established yet. An experiment was therefore conducted to study the effects of feeding compound concentrate supplements with either a low (L) or high (H) level of DVmet on feed intake and milk production in dairy cows fed a grass and maize silage mixture ad libitum

The overall performance of pigs is closely related to that achieved immediately post-weaning which is often only modest because of inefficient digestion on cereal-based diets (attributable to insufficient a-amylase). Processing of cereals is frequently considered and micronising is employed. Previous studies using this technology have concentrated on growing / finishing pigs (e.g. Lawrence 1973). Furthermore, investigation of the precise effects of altering variables during processing have not been widely studied. The objective of the current trial was to examine the effects of steeping and micronising temperature with wheat on the nutritional value of diets determined with postweaning piglets through assessments of performance and digestibility.

Formulating diets to match more closely the requirements of the pig for amino acids results in diets which are lower in crude protein (CP) than conventional commercial diets. The lower intake of nitrogen (N) which is concomitant with these diets results on lower N excretion. The excretion of excess N requires energy and previous nutrient balance work undertaken at Terrington (Lee and Kay, 1998) indicated that the ‘energy sparing’ effect of the reduced crude protein diets can be utilised by reducing the digestible energy (DE) content of reduced CP diets whilst at the same time maintaining the level of N retention. The objective of this work was to determine the performance carcass characteristics and slurry characteristics of growing/finishing pigs given reduced CP/DE diets.

Testing several genotypes on one diet may impose nutritional constraints on growth for particular genotypes. In the study, three genotypes were tested on four isoenergetic dietary regimes to determine if a genotype with diet interaction existed for the pattern of cumulative protein intake and total protein intake.

There were 150 Large White pigs from the lean, control and fat lines, with divergent selection for lean growth rate over seven generations. In each line, there were 10 full-sib groups and within each full-sib group, one pig was allocated to each of the high (H : 220 g crude protein (CP)/kg) or low (L : 120 g CP/kg) protein diets, a standard test diet (S : 195 g CP/kg) and the two remaining pigs were tested using the diet-choice procedure (DC), using the H and L diets. Pigs were performance tested from 30 to 85 kg, with individual penning.

In recent years there has been a notable increase in outdoor pig production systems; however, the nutritional requirements of these animals have not been well established. To make nutritional decisions relating to the needs of grazing animals, accurate estimations of the herbage intake and value have to be made. N-alkanes found in the wax cuticle of plants have been used as markers to measure the intake of grass by grazing ruminants (Dove and Mayes, 1991). This experiment studied the use of the methodology in grazing pigs.

The intake and the digestibility of grass, and the effect of level of supplementary concentrate feed, were measured in late spring and late summer in two studies each with eight multiparous, pregnant sows. In the Spring study sows were nose rung to prevent rooting, but only unrung sows were available for the Summer study.

Feeding lambs diets formulated to be synchronous for their hourly release of energy and nitrogen (N) in the rumen has been shown to increase growth rate and feed conversion efficiency (Witt et al. 1997). However the diets used contained different feed ingredients and therefore the differences in performance may have been due to some aspect of the diet that was not characterised. The objectives of the current experiment were to supply the same quantity of feed ingredients over a 24h period but alter the sequence of allocation within the day to achieve different patterns of energy and N release in the rumen and investigate the effects on growth and metabolism of ram lambs when fed at a restricted level.

Sucrose and lactose are used as energy supplements in ruminant diets. In our previous study (Hussain and Miller, 1998) lactose maintained a higher rumen pH, increased organic matter and neutral detergent fibre digestion in the rumen, reduced the number of rumen protozoa and increased microbial (bacterial) protein flow to the duodenum compared with sucrose. However, it was not clear whether the effect of lactose on pH or on reduction of protozoa was the main factor increasing rumen fermentation and microbial protein flow. The objective of the present study was to examine the effect of isoenergetic amounts of sucrose and lactose as supplements (equivalent to 50 g glucose) on rumen fermentation and metabolism in the presence of sodium bicarbonate to maintain rumen pH.

Microbial protein is the most variable and uncertain element of current systems of evaluating protein requirements for ruminants. The variability is partly a result of the multiplicity of techniques used to quantify microbial nitrogen (MN) yield and partly due to unrepresentative sampling of microbial cells. In a number of studies in the literature it is tacitly assumed that marker:N ratios in rumen liquid associated bacteria (LAB), solid associated bacteria (SAB) and duodenal digesta bacteria (DDB) are identical. Under ordinary feeding conditions ruminal SAB are numerically predominant and may comprise 50-75% of the total microbiota (Mitsumori and Minato, 1997). This study highlights the variations in chemical composition in LAB, SAB and DDB and their implications in estimating microbial growth. The study also simultaneously compares four microbial markers in vivo.

The distinctive (phospholipid or total) fatty acid profiles of the major classes of micro-organism have been used in microbial taxonomy as well as to act as microbial markers in soils. Our studies seek to identify the potential of this approach in rumen studies. One of the main distinctions is between solid- and liquid-associated bacteria (SAB and LAB) in the rumen, though it is not clear what relative contributions these make to microbial yield from the rumen. The objective of this work was to determine whether SAB and LAB have distinctive fatty acid profiles and if differences are affected by dietary fat supplementation.

The current energy (E) feeding standards (AFRC, 1993) have the objective of providing accurate feeding of dairy cows when there is either zero tissue E retention or a given tissue E change. Such approaches are of limited practical value in the real world in which we must be able to predict optimum feeding levels and strategies for animals of differing milk yield potential producing in a range of physical and economic environments. In the latter context the key economic factor is how the animal responds to additional increments of feed. This is primarily driven by how the animal partitions that additional E between milk output and body tissue gain. The objective of this experiment was to use calorimetric techniques to explore the impact of level of metabolisable E (ME) intake (MEI) on milk E output (E1) and tissue E gain (Eg) and hence partitioning of increments of MEI between milk and tissues.

Increasing maturity at harvest of maize silage has been shown to affect feed intake and milk production in Holstein-Friesian cows (Phipps et al., 1998). The purpose of the present experiment was to determine whether the milk production response was related to improvements in the efficiency of feed energy utilisation.

Four multiparous Holstein-Friesian cows (mean live weight 620 kg) fitted with permanent cannulas in the rumen and proximal duodenum were given diets based on maize silage and grass silage (3:1 DM ratio) offered ad libitum plus 8.7 kg DM/day of a concentrate (254 g crude protein (CP)/kg DM) starting 5-10 weeks post-calving. The maize silage was harvested at four different stages of maturity as defined by DM content and ensiled without additives. The grass silage was a first-cut perennial ryegrass (260 g DM/kg, 519 g neutral detergent fibre (NDF)/kg DM, 146 g CP/kg DM).

Previous studies at this Institute (Yan et al., 1997), using regression techniques on calorimetric data obtained with dairy cows offered grass silage based diets, have indicated that the metabolisable energy (ME) requirement for maintenance (MEm) is higher than that predicted using the equations of AFRC (1990). It was hypothesised, (Yan et al., 1997), that this higher MEm may reflect the use of diets containing ensiled grass and, furthermore, that ratio of grass silage:concentrates also influences MEm. In contrast, kl calculated by regression techniques was in line with that predicted using the equations of AFRC (1990). Against this background, the objective of the current study was to establish, using regression techniques, the MEm and kl on a non-grass silage based ration.

The metabolisable energy (ME) requirement for maintenance (MEm) has been derived from measurements of fasting heat production (FHP) with non-lactating cattle, with, for example, ARC (1980) using published data on steers to develop equations to calculate the MEm of dairy cattle. Recent studies at this Institute (Yan et al. 1997 a&b) have produced estimates of MEm, through either direct measurement of FHP, or the use of regression techniques for producing animals and concluded that MEm was higher than those in published feeding standards (ARC, 1980; AFRC, 1993). The objective of the present experiments was to explore possible reasons for the differences, such as the effect of cow body condition score (CS) on FHP and the effect of level and type of diet given during the pre-fasting period on FHP.

Wilting of grass prior to ensiling generally produces positive responses in dry matter (DM) intake of cattle, but the responses in animal performance are often small, or even negative. The primary objective of the present study was to compare energy utilization from heavily wilted and unwilted silages by growing cattle when given at equal metabolisable energy (ME) intakes. A secondary objective was to evaluate effects of silage additive type (inoculant v. formic acid) on energy utilization.

Four silages were produced from unwilted and wilted grasses (DM 193 and 450 g/kg) obtained from a perennial ryegrass sward. The wilted grass was dried in the field for 26 hours using rapid wilting techniques involving crop conditioning and spreading. At ensiling both the unwilted and wilted grasses were each treated with two additives, a bacterial inoculant (Ecosyl, Zeneca Bioproducts Limited) and a formic acid additive (ADD-F, BP Chemicals Ltd.).

The in vitro gas production technique has been developed as a means of predicting the degradability of feeds. However, it was pointed out by Blümmel et al. (1997) that attention should be given to the other products of the incubation as well. Degraded feeds may be incorporated directly into microbial biomass, or they may be fermented to produce VFA and gas. One of the objectives of this experiment was to determine whether the proportion of degraded substrate that was partitioned to gas production varied with different feeds. Blümmel et al. (1997) observed a negative relationship between gas yield (ml gas produced/g substrate degraded) and microbial biomass yield (mg biomass/g substrate degraded) when poor quality forages were incubated. A second objective of this work was to determine whether this relationship was also observed when higher quality feeds were used.

Methane formation in the rumen represents a substantial loss of energy to the animal and is also a major source of greenhouse gas emissions from agriculture. Methanogenesis is the main means of disposal of hydrogen during rumen fermentation. The formation of propionate represents an alternative route of hydrogen disposal, providing sufficient propionate precursors are available. Theoretically, adding propionate precursors should stimulate propionate production and decrease methane production. In the present experiment, the effects of two potential precursors of propionate, fumarate and acrylate, on rumen fermentation and methane production were investigated in a rumen simulating fermentor.

To calculate the extent of ruminal degradation based on the gas production technique, equations were derived to describe gas production profiles from substrate degradation (France et al. submitted). This derivation demonstrated that if the yield of gas (Y; ml/g degradable OM) produced during the course of incubation varies significantly, then the calculated extent of degradation is not correct. Variation in Y may occur due to variation in the yield of individual volatile fatty acids (VFA) produced. The objective of this simulation study was to examine the impact of variation in individual VFA production and consequently in yield of gas on the extent of ruminal degradation.

Gas production profiles were simulated based on a generalized Mitscherlich (GM) equation (see France et al. submitted) for three substrates (soluble sugars, starch, fibre) that differ in degradation rate and VFA production profile (see Table 1).

In the Dutch feed evaluation system for ruminants, it is assumed that each 1000 g of rumen fermented organic matter (FOM) produces 150 g of microbial protein. However, this is a simplification of the real in vivo processes. Demeyer and Van Nevel (1986) concluded that the efficiency of microbial growth depends on several factors, such as chemical and physical properties and intake. They concluded that feeding low quality roughage would show lowest efficiency and feeding highly degradable starch would show highest efficiency. We investigated the possibilities to estimate differences in efficiency of microbial growth in rumen fluid with the gas production technique.

Vitamin E is an important nutrient for lambs and low levels in tissues as a result of either low intake, poor absorption or excessive utilisation results in myopathy (pale muscle). The causes of deficiency are incompletely understood, especially as it can occur when lambs are consuming good quality grass containing high levels of vitamin E. We now report an occurrence of low tissue levels of vitamin E in lambs of two breeds raised on complete dry pelleted rations and its effect on meat quality and fatty acid composition.

96 male lambs, half Suffolk x Lleyn and half Scottish Blackface, with average live weights of 24 kg and 18kg respectively were individually penned and randomly allocated to one of 6 isoenergetic isonitrogenous diets based on dried grass, molassed sugar beet pulp, soya bean meal and molasses and containing two levels of vitamin E, 100 (low) and 500 (high) g/kg DM.