Thirty-six entire male pigs were used to investigate the effects of two levels of dietary crude protein (150 and 220 g/kg) each in combination with four levels of feeding (1·0, 1·32, 1·64 MJ digestible energy/kg M0·73 per day and ad libitum) on growth, body composition and energy utilization over the live-weight range 7 to 19 kg.

Growth rate responded linearly (P < 0·001) to increasing energy intake but was depressed (P < 0·05) when dietary crude protein was reduced from 220 to 150 g/kg.

Raising digestible energy intake increased and decreased respectively the proportions of fat and protein in the empty body at 19 kg live weight. However, the magnitude of the response of both components to change in digestible energy intake was reduced in the case of pigs fed the lower protein diet.

Total energy retained and that retained as fat and as protein responded linearly (P < 0·001) to change in digestible energy intake of either diet. Extrapolation of the regression of total energy retained on digestible energy intake yielded a digestible energy requirement for maintenance of 510 kJ/kg M0·75 per day, which was unaffected by level of dietary protein.

The partial efficiencies of protein utilization, estimated from the regressions of protein deposition (g/day) on protein intake (g/day), were 0·616 and 0·411 for pigs given the diets containing 150 and 220 g crude protein per kg respectively.

Many trials at Reading have shown store lambs to be reluctant to eat straw when first housed after grazing. This is especially so if penned individually, as is often the case in feeding trials. Such isolation may induce stress, including depressed intake (Crampton, 1959; Kidwell, Bohman and Hunter, 1954). Farm animals are generally stimulated to eat more when in a group than when isolated (Curtis, 1983), yet most intake studies, particularly with sheep and cattle, are conducted with individually-penned animals. Concern for the welfare of animals being used for trials calls for systems of housing that minimise stress.

The present experiment tested the hypothesis that straw intake, by store lambs first-housed after grazing, would increase if lambs were penned in pairs rather than individually, or confined in pens allowing pen to pen vision rather than prohibiting pen to pen vision.

The removal of ciliate protozoa, or defaunation, results in the establishment of a new ecosystem in the rumen, consisting only of bacteria and fungi. Although extensive research has been done on ciliate-free ruminants, the role of protozoa in the rumen still provokes considerable debate. The diversity of experimental design, such as animal species, defaunation method, and diet could account for many of the differences observed between defaunation studies. Also it is important to examine the stability of the ciliate-free ecosystem. The aim of this study was to investigate changes in rumen fermentation of ciliate-free sheep over a period of one year.

Eight male castrated sheep, weighing 60-70 kg, received twice daily 700 g of a diet of hay, barley, molasses, fish meal and vitamins/minerals (500, 299.5, 100, 91 and 9.5 g/kg DM respectively). Four sheep were defaunated by the rumen washing technique (Jouany and Senaud, 1979) and kept in isolated pens while the other four were left faunated with a mixed type A ciliate protozoa population. Rumen samples were withdrawn via the rumen cannula and blood samples were taken from the jugular vein -1, 0, 1, 2, 4 and 6 h after feeding. There were three sampling periods: one month, six months and one year after defaunation.

Mating is one of the most critical processes influencing the success of any breeding pig enterprise since the efficiency of this process establishes the potential output of pigs. A study was conducted on 100 recently weaned sows during the mating process to determine potential sources of inefficiency.

The study was conducted in a large commercial herd with Large White (LW) x Landrace (LR) first cross sows. 4 genotypes of boar were in use, these being LW, LR, LW x LR and Duroc. The parity of the 100 sows involved in the study ranged from 1 to 9. Sows were housed in small groups of 5 to 6 following weaning at a mean of 18 days post partum and were taken daily to an oestrus detection area to test for standing oestrus (SO). Boars were housed around this area and SO was detected using the back pressure test Within 5 minutes of SO being confirmed, each sow was paired with a boar in a specialist 2.9 v 2.65 m mating pen. This pen had a 15 cm floor covering of sawdust-based deep litter which provided good foothold and comfort Boar-sow behavioural interactions, general behaviour of the mating partners and sow vocalisations were recorded from the first pairing in the pen to the dismounting of the boar following mating.

In pigs the quantification of breakdown and synthesis by powers of body protein led to the estimation of turn-over related protein retention efficiency by the equation kP = {1 + [1 − (P/α) (2/9)Q]−1/6}−1, with α the limit value of whole body protein (P) maturity, so that 0 ≤(P/α)≤1. The factor 2/9 is derived from diffusion attributes indicated by cell and nucleus geometries α and Q represents a scaled transformation of intake, 0 ≤ Q ≤ 1, such that a value of Q = 1 may represent ad libitum intake and Q = 0 the intake at the maintenance requirement. Published observations on finishing steers provide estimates of whole body protein synthesis and breakdown at pre-determined levels of intake in confirmation of the theoretical (2/9)Q power associated with (P/α) in kP. Further confirmation of the (2/9)Q power in cattle follows from satisfactory agreement between an estimate of conventional multiple regression retention efficiency and the turn-over related retention efficiency calculated at the given level of intake, for the mid point of the body mass interval covered by the regression estimate. In addition, a simulation experiment on cattle from the literature gives power estimates of protein breakdown and synthesis in general agreement with those accepted for pigs. Examples on both fine and coarse diets are employed to suggest a general rule for prediction on diets causing submaximal efficiency due to suboptimal intakes.

In sheep, evidence derived from estimates of conventional multiple regression efficiencies suggests that the rule (a-b) = (2/9) Q for the calculation of kP should be reserved for the description of compensatory growth. Protein retention efficiency for ordinary growth should be described by an adaptation of the rule derived for suboptimal intakes.

Results of an experiment involving a total of 24 individually-fed pigs, covering the growing period between about 40 and 210 lb. live-weight, indicated that the addition of 20 g./ton griseofulvin to the diet had a slight depressing effect on the rate of growth of the pigs. It had no significant effect on the efficiency of food utilisation, but caused a small reduction in daily food consumption.

Effects of dietary protein concentration on the amino acid composition of sow's milk was studied using 10 crossbred first-litter sows. At parturition, diets containing similar concentrations of digestible energy but with either 63 or 238 g crude protein per kg and 4.4 and 15.1 g lysine per kg respectively, were given through lactation (five sows per treatment). The ratios of other amino acids to lysine were in excess of those currently recommended for lactating sows. Dietary protein level significantly affected milk yield, gave higher milk protein output (P > 0.05) but was without significant effect on the proportions of amino acids in the milk.

Inaccurate prediction of silage intake is often the greatest source of error in ration formulation but improvements have been hindered by an inadequate description of the silage fermentation in advisory practice. Until recently, only pH and ammonia N have been routinely measured as indicators of silage fermentation characteristics. A new method, based on research in Finland (Moisio and Heikonen, 1989) has been developed and is now in use by SAC. This involves automated titration of juice squeezed from the silage to pH 2 (with HC1) followed by stepwise titration (with NaOH) to pH 12. Concentrations of juice constituents are predicted from the buffering capacities measured over segments of the titration curve (pH 2 to pH 12). Calibrations have been obtained empirically by the addition of known increments of standards to a range of silage juices. Proportions of variance (R2) of measurements made by reference methods accounted for by predictions from titrations for a validation set of 93 silages were 0.90, 0.78, 0.92, 0.82 and 0.82 for lactic acid, acetic+butyric acids (VFA), soluble N, sugar and ammonia N respectively.

A comparison was made between the Heal digestibility of the amino acids in pigs obtained by the use of a basal diet, the apparent Heal digestibility obtained with a semi-synthetic diet where peas were the sole protein source and the true Heal digestibility obtained with synthetic and nitrogen-free diets.

The UK metabolisable protein system (AFRC, 1992) requires the measurement of fermentable metabolisable energy (FME) to determine the potential yield of microbial crude protein in the rumen. FME is defined as:

The objective of this work was to measure the ME , ether extract and volatile fatty acid components of first cut grass silages to assess the range of FME and non-fermentable fractions and hence the range of fermentabilities (FME:ME).

Eighty-four clamp grass silages, predominantly first-cut rye grass, were analysed for modified acid detergent fibre (MADF), individual volatile fatty acids, oil (ether extract) and oven dry matter. ME was predicted from the MADF after correction for oven dry matter. The gross energy of the lactic, acetic, propanoic, butyric and valeric acid were taken to be 15.2, 14.6, 20.8, 24.9, and 28.0 MJ/kg DM, and for the Ether Extract fraction of grass 38.5 MJ/kg DM. The energy content of the volatile fatty acids in the silage were summed and FME was calculated as described above. The fermentability of the silage was the expressed as the proportion of FME to ME.

The efficient production of lean beef suitable for current consumer demand necessitates effective rationing of beef cattle. Feeding standards for beef cattle given by ARC (1980) predict that a reduction in energy intake produces a large reduction in performance with little effect on the energy or fat contents of the gain. However previous studies have shown that diets containing a high proportion of grass silage may sustain lower levels of performance and result in a greater proportion of fat in the gain in both calves and finishing cattle, than when similar quantities of energy and protein are given in the form of high-concentrate diets. The effects of a change in energy intake on performance and carcass composition of beef cattle are therefore likely to depend on whether this change is achieved by restricting the quantity of food given or changing the forage: concentrate ratio of a diet given ad libitum.The present experiment was carried out to examine the effects of forage:concentrate ratio in the diet and ad libitum versus restricted dry matter intake on the performance, carcass composition and efficiency of lean meat production by steers.

The aims of the experiment were to determine the intake, digestibility and particle passage kinetics of urea treated (40 g urea / Kg DM) whole crop wheat (UW), grass silage (GS) and a 0.5:0.5 UW : GS mixture (UG) on a DM basis.

The chemical composition of GS and UW were respectively, TDM (gTDM/Kg) 227, 648; NDF (g/Kg DM) 528,426; ADF (g/Kg DM) 346, 285; Ash (g/Kg DM) 74, 62; Starch (g/Kg DM) 3, 236; Nitrogen (g/Kg DM) 24.2, 30.2; Ammonia N (g/Kg TN) 91, 382; pH 3.9, 8.5; NCD (g/Kg DM) 681, 642 respectively.The UG was mixed daily, in an attempt to reduce selection of individual components by the animals.

The experimental design was based on two 3 x 3 latin squares with three animals per square and three periods of three weeks duration. Six Holstein Friesian x Brown Swiss pregnant heifers (mean liveweight 400 Kg) were used to assess (during the last 7 days of each period) the voluntary intake, digestibility and particle passage kinetics of the three forages.

Animal production is commonly reported to increase when different animal species are grazed together on the same pasture (Nolan and Connolly 1977). In such experiments there is often a difficulty with interpretation of results due to a failure to establish equal grazing pressures between species mixtures, and confounded production differences may result. The theory behind the design of mixed experiments continues to pose problems (Connolly and Nolan 1976, Connolly 1984).

The experiment reported here was designed to investigate whether, when different animal species are grazed at the same pressure, there are differences in animal intake and/or diet composition when they are grazed singly or in mixtures.

Nineteen, 18-month-old steers, 40 yearling wether goats and 40 10-month-old wether sheep were grazed in New Zealand on a mature summer ryegrass/white clover pasture (4550 kgDM/ha) in 5 treatments: cattle alone (CA), sheep alone (SA), goats alone (GA), and cattle with sheep (CS, SC) and cattle with goats (CG, GC).

Plant structural polysaccharides provide a major source of nutrient for ruminant livestock. These carbohydrates are not degraded by mammalian-derived enzymes, but are hydrolysed by rumen microbial plant cell wall hydrolases. In view of the pivotal role of microbial cellulases and xylanases in ruminant nutrition, there has been considerable interest in these enzymes. In this paper we wish to illustrate how recombinant DNA (rDNA) technology can be utilised to dissect the biochemistry and molecular architecture of these enzymes, and provides us with the opportunity of generating novel cellulases and xylanases with increased capacity to hydrolyse the plant cell wall.

In general cellulases and xylanases from anaerobic microbes associate into large molecular weight complexes, whose integral structures are responsible for the efficient hydrolysis of plant structural polysaccharides. The feasibility of altering these complexes, or transferring them to other organisms represents a significant challenge.

The two most widely adopted methods for measurement of milk production in sheep suckling lambs, the lamb-weight increment technique and milking-out following administration of oxytocin, give estimates which differ proportionately between 0·05 and 0·28 especially in early lactation (Doney, Peart, Smith and Louda, 1979). It is not easy to determine which method gives the most accurate estimate of milk production in suckling ewes. It is important, however, to understand the circumstances in which discrepancies between methods may occur and their magnitude. This note provides evidence that such discrepancies may vary with nutritional status of the ewe.

Future human population increases will require more land being devoted to cereal production. This will demand that ruminants be increasingly reliant on crop by-products for feed. The greater integration of crop and animal production will require more reliance on stall feeding systems. There is little published information on stall feeding systems for sheep and goats. Furthermore there is little information on the design of stall feeders for these animals. This paper reports an experiment designed to measure the reach capacity of sheep and goats in order to provide base line data which will be required when designing feeders for them.

A study was made of the concentration of insulin-like growth factor-l (IGF-I) in the plasma of Jersey cows differing in genetic merit for milk and milk fat production. Plasma IGF-I concentrations exhibited an annual cycle and from this study it is concluded that, in the Jersey breed, selection for increased milk and milk fat production, with the correlated responses of increases in mature live weight and live-weight gain, will not be accompanied by increased plasma IGF-I concentration.

Sward growth rate and height decline under autumn grazing in the UK. This eventually depresses ewe intake, live weight and body condition and may, as a consequence, reduce reproductive performance. The provision of supplementary feeding is a strategic measure to avoid this but requires quantification in relation to measurable variables such as sward height and stage of the reproductive cycle.

A management decision rule for supplementary feeding over the mating period, which is currently operated in the MLURI upland system studies, requires that, in order to maintain both body weight and condition until the completion of the second cycle of mating, concentrated feed be introduced when sward height (herbage mass) is ≤3.5 cm (≤1200 kg DM/ha), be increased when height is ≤3.0 cm ( ≤ 1000 kg DM/ha) and ad lib, hay be introduced when height is ≤ 2.5 cm (≤ 750 kg DM/ha).

Several expert committees have recommended reductions in intake of saturated fat for health reasons and in Britain this advice has been accepted by Government. There will be increasingly more fat-conscious consumers demanding leaner meat and in order to supply this demand retailers will select leaner carcasses and adopt new cutting methods. The trend within the beef industry is towards leaner cattle, coupled with increased production rates in abattoirs. This has led to concern about possible damage to eating quality.

A trial was carried out to investigate the eating quality of lean beef cuts produced from leaner animals or by more severe trimming and to investigate the possible compensatory effects of electrical stimulation on quick chilling.

At each of 20 abattoirs, 12 steers were selected and slaughtered together. Four were Hereford x Friesian, four were Continental x Suckler and four were Friesian/Holstein.