A deterministic bio-economic model was used to investigate the impact of different heifer replacement breeding systems for beef suckler cow production in different environments. It was shown that measures of cow efficiency were highly correlated with profitability in suckled calf production. However, where significant genotype differences exist in final output value due to issues of carcass quality, then more complete characterization of system profitability is recommended. In systems utilizing a terminal sire mating policy for all matings in excess of replacement heifer requirements the proportion of terminal sire matings made are affected by female fertility. Reduced cow fertility combined with late attainment of puberty in heifers and low heifer fertility has a substantial negative effect on the proportion of terminal sire matings made. This illustrates an aspect of production that can be improved by the use of crossbreeding to exploit heterosis in reproductive traits. The time frame of impacts of the different systems was seen to vary. Grading up to a pure breed allowed exploitation of heterosis in the early years of the transition leading to a boost in profitability but this boost was lost as the herd became purebred. Composite and rotational crossing systems were seen to create a steady rise in financial margin to the point where they became stable in breed proportion and heterosis. The effect of cow size was evaluated in three different environments, representing UK lowland, upland and hill. It was found that small cows became more profitable in relation to large cows as food resources became more limiting. In a non-limiting environment large cows were more profitable than small cows.

A deterministic, dynamic pig growth model is described that predicts the effects of genotype and the thermal and nutritional environments on food intake, growth and body composition of growing pigs. From the daily potential for protein gain, as determined by pig genotype and current state, the potential gains of the other chemical components, including ‘desired’ lipid gain, are calculated. Unconstrained voluntary food intake is predicted from the current protein and lipid contents of the pig, and the composition of the food, as that which is needed to permit potential growth to be achieved. The model allows compensatory lipid gain. The composition of the food is described in terms of its digestible energy content (DEC), ideal digestible crude protein content (IDCPC) and bulkiness. Both energy and protein can be limiting resources and the bulk of the food may constrain intake. The animal’s capacity for bulk is a function of its size. The thermal environment is described by the ambient temperature, wind speed, floor type and humidity and sets the maximum (HLmax) and minimum (HLmin) values possible for heat loss. A comparison with heat production (HP) determines whether the environment is hot (HP > HLmax), cold (HP < HLmin) or thermoneutral (HLmin < HP < HLmax). A constraint on intake operates in hot environments, while in cold environments, there is an extra thermal demand. If conditions are thermoneutral no further action is taken. Daily gains of each of the chemical components are calculated by partitioning energy intake between protein and lipid gains according only to the energy to protein ratio of the food. The model builds on the work of others in the literature as it allows predictions on how changes in: (i) the kind of pig; (ii) the animal’s current state, which is particularly relevant in cases of compensatory growth; (iii) the dietary composition, and; (iv) the climatic environment, affect food intake and growth, whilst maintaining simplicity and flexibility.

A total of 276 crossbred pigs were used in three trials to determine if feeding spray-dried animal plasma (SDAP) in simple phase 1 piglet diets with differing soya-bean meal (SBM) levels can influence performance or immunoglobulin G (IgG) levels specific to the antigenic soya proteins, glycinin and β-conglycinin. Pigs were blocked according to initial body weight and equalized across treatments according to gender and ancestry. Blocks of pigs were then randomly assigned to one of three treatments in a completely randomized block design. The dietary treatments were as follows: (1) 10% +: 100 g/kg SBM with 75 g/kg SDAP; (2) 20% +: 200 g/kg SBM with 75 g/ kg SDAP; (3) 20%-: 200 g/kg SBM without SDAP. Pigs were given treatment diets for 14 days, followed by a common diet for the duration of the trials (35 days). Average daily gain (ADG) and gain to food (G: F) ratios were not affected by dietary treatments. Average daily food intake (ADFI), however, was greater for pigs given 10% + as compared with 20% + and 20%- (P < 0.05) during days 0 to 14 post weaning. Addition of SDAP increased ADFI (P < 0.01) and tended to increase ADFI when added to diets containing 200 g/kg of soya-bean meal (P = 0.06). No differences were detected in soya-specific IgG levels during any collection period. These data suggest that SDAP addition to simple phase 1 piglet diets increased ADFI during the first 2 weeks, but did not alter ADG or food efficiency. There was no indication that SDAP addition altered IgG titres against the soya-bean proteins, glycinin and β-conglycinin.

Twenty-seven multiparous Large White sows were used to determine the effect of season in a tropical climate and dietary fibre on their feeding behaviour during lactation. The experiment was conducted in Guadeloupe (French West Indies, latitude 16°N, longitude 61°W) between October 1999 and January 2001; climatic conditions in the farrowing room were equivalent to outdoor conditions. Two seasons were determined a posteriori from climatic criteria recorded continuously in the farrowing room. During the warm season, ambient temperature and relative humidity averaged 25°C and 0·868, respectively. The corresponding values for the hot season were 27·5°C and 0·835. Experimental diets offered during lactation were a control diet (C; 140 g neutral-detergent fibre (NDF) per kg) and a high fibre diet (HF; 200 g NDF per kg). Sows were offered food ad libitum between the 6th and the 27th day of lactation. Daily food intake between day 6 and day 27 decreased during the hot season (P < 0·001; 3226 v. 5571 g/d during the warm season). This was achieved by a reduction of both meal size (P < 0·05; 460 v. 718 g per meal) and ingestion and consumption time (P < 0·01; -11·1 and -15·3 min/day, respectively) whereas the number of meals remained constant (8·4 meals per day on average). During warm season, hourly food intake peaked twice daily near sunrise and sunset. During the hot season, peaks were attenuated and food intake was reduced during the hotter periods of the day and increased during the fresher period of the day, especially in early morning. As a result the diurnal partition of food intake was significantly affected by season; proportionately 0·62 and 0·47 of total food intake occurred during the day in warm and in hot seasons, respectively. Standing duration averaged 138 min/ day with no significant difference between seasons. Feeding behaviour criteria were not influenced by diet composition. In conclusion, the season in a humid tropical climate significantly affects the feeding behaviour of lactating sows.

The effects of floor type and stocking density on leg weakness, osteochondrosis and claw disorders in slaughter pigs were studied. Three hundred pigs were housed in pens with either solid floors with plenty of straw, solid floors without straw or fully slatted floors at either high (0·65 m2 per pig) or low (1·2 m2 per pig) stocking density from 25 to 105 kg. In each pen half of the pigs were boars and half gilts of the breeds Landrace and Yorkshire ✕ Landrace crossbred. There was no difference in growth rate between the three floor types. The growth rate of the boars was higher at low compared with high stocking density, while no effect of stocking density was seen in the gilts. The prevalence of leg weakness and claw disorders was different for the various floor types, while no effect of floor type could be found on joint changes. With regard to leg weakness, slatted flooring was significantly worse than solid floors with or without straw for standing under position on hind legs, while pens with plenty of straw were significantly better than the other floor types with regard to stiff movement and forelegs turned out. A calculated sum of the nine leg weakness symptoms showed that pens with straw were the best followed by solid floor without straw, while slatted floors were the worst. Regarding claw disorders, solid floors without straw were the worst. High stocking density affected four leg weakness variables (buck-kneed forelegs, turned-out fore- and hind legs, standing under position on hind legs), one joint change and three claw disorders negatively. Boars scored worse than gilts with regard to one leg weakness trait and one claw disorder and thickening of cartilage in two joints. Differences between breeds differed for the examined variables. Claw hardness was affected by floor type with regard to medial claws, which were softer on slatted floors. The hind claws were softer than the foreclaws on the volar surface, while there was no difference between the hardness of the topside of the fore- and hind claws. Claw hardness was not affected by sex. In conclusion, it can be said that the examined floor types do not have the same effect on the different aspects of leg weaknesses and claw disorders. Thus, clinical leg problems are worst on slatted floors and best in pens with straw, but claw disorders are worst on solid floors without straw. Further, high stocking density specifically affects the clinical leg weaknesses and claw disorders. Joint changes were not affected by floor type or stocking density.

A deterministic, dynamic pig growth model predicting the effect of genotype, and the thermal and nutritional environments on food intake, growth and body composition of growing pigs was tested and evaluated against experimental data from the literature. Four sets of experiments meeting the necessary requirement of feeding the pigs ad libitum and reporting sufficient information on trial conditions were chosen to test the model. The parameters used in the model to describe the kind of pig were protein weight at maturity (Pm) the Gompertz rate parameter (B) and the ratio of mature lipid weight (Lm) to Pm. Values for Pm and B used to apply to the pigs in the four experiments were selected as those which gave the maximum daily gains equal to those reported at thermoneutral temperatures on diets not limiting in protein. The value of Lm was chosen as that which gave a value for food conversion ratio close to that seen in the experiment, again at a thermoneutral temperature and on a non-limiting diet. The model was run for each of the experiments from the given start weight until slaughter weight was reached. All pigs were assumed to have their desired bodily composition at the start of the experimental period, which is determined by their genetic descriptors and weight. From the conditions of the experiments, average daily gain (ADG) average daily food intake (ADFI) food conversion ratio (FCR) final body weight, body composition, average daily gains of each of the chemical body components and heat production (HP) were predicted. Generally as temperature increased or the crude protein content of the food increased, ADFI, ADG and the fatness of the pig decreased, whilst protein content increased. Quantitative differences between the model predictions and the observations, were probably due to the greater sensitivity of the model to temperature. This is likely to reflect the omission of long-term adaptation and acclimatization, or to incorrect estimation of the wetness of the pig’s skin. However, model predictions were generally in good quantitative agreement with the observed data over the wide range of treatments tested. This gives support to the value and accuracy of the model for predicting pig performance when the thermal and nutritional environments are manipulated.

Avilamycin (AGP) and zinc oxide (ZnO) are both frequently included in the post-weaning piglet diet to enhance growth performance and prevent diarrhoea. This study investigated what effect removing these compounds from the post-weaning diet would have on the growth performance and faecal microbiota of weaned piglets. Fifty-two crossbred piglets (JSR Healthbred) were allocated, at weaning, to one of two dietary treatments on the basis of weight, litter origin and gender. The diets were (i) control (no supplemented ZnO or AGP); (ii) ZnO + AGP (supplemented with 3100 mg ZnO per kg food and 40 mg avilamycin per kg food). These diets were offered ad libitum for 20 days post weaning. Thereafter, the pigs received the same non-supplemented grower and finisher diets ad libitum. All piglets were individually weighed, and faecal samples were obtained from pre-selected piglets, at various time points throughout the trial period. Ten-fold serial dilutions of faecal material were cultured on specific media to enumerate aerobes, anaerobes, Lactobacillus spp. and Escherichia coli. ZnO + AGP supplementation enhanced weaned piglet average daily food intake (ADFI) (P < 0·001), average daily live-weight gain (ADG) (P < 0·001) and food conversion ratio (FCR) (P < 0·01) during the initial 20 days post weaning. Piglets previously supplemented with ZnO + AGP gained more weight per day during the non-supplemented grower phase (days 21 to 60) than their control counterparts (741·5 v. 672·5 g per pig per day) (P < 0·01). The bacteriological data showed that ZnO + AGP piglets had lower counts of anaerobic bacteria in their faeces than control piglets (P < 0·01). These findings indicate that dietary AGP + ZnO may enhance growth by reducing gastro-intestinal bacterial populations, and that their removal from the post-weaning diet will increase days to slaughter.

The intake of immunoglobulin G (IgG) by sucking piglets from colostrum was estimated over the first 24 h of sucking by the weigh-suck-weigh technique using experimentally determined correction factors for metabolic and urinary losses and was related to appearance of IgG in piglet plasma. Colostrum immunoglobulin G (IgG) concentrations declined rapidly from 61 mg/ml at the start of sucking to 9·0 mg/ml after 24 h sucking. IgG was first detected in piglet plasma after 4 h sucking, increased to a maximum after 12 to 16 h sucking and thereafter declined. In piglets allowed to suck from birth, there was no significant relationship between estimated IgG intake and plasma IgG concentration suggesting that IgG intake did not limit acquisition of IgG by the piglet. When sucking was delayed by 8 or 12 h, colostrum intakes by piglets were not different from piglets allowed immediate access to the udder but IgG intakes were significantly (P < 0·001) decreased. Total plasma IgG (g/kg live weight) did not decline significantly as a result of delayed sucking. In conclusion, under the experimental conditions employed, the appearance of IgG in piglet plasma was limited by factors other than by colostrum IgG intake.

The present work was planned to study the effects of mild and hot conditions on reproductive traits of male rabbits. The traits studied were libido (reaction time), semen quality characteristics (hydrogen-ion value, ejaculate volume, sperm motility, dead sperm, sperm abnormalities, acrosomal abnormalities, sperm-cell concentration and total sperm output), seminal biochemical traits (total protein, albumin, globulin, total lipid, cholestrol and creatinine), seminal enzymes (glutamic-pyruvate transaminase (GPT), glutamic oxalo-acetic transaminase (GOT), alkaline phosphatase and acid phosphatase), seminal hormones (tri-iodothyronine (T3) and cortisol), thermoregulatory parameters (respiration rate and temperatures of ear, rectum and skin), food and water consumption, blood metabolites (total protein, albumin, globulin, glucose, total lipid and cholesterol), kidney function (urea-N and creatinine), liver function (serum GPT, serum GOT and alkaline and acid phosphatase) and endocrine functions (T3 and cortisol hormones).

The estimated temperature-humidity index (THI) values were 20·2 during the mild and 30·1 in the hot period, indicating absence of heat stress in the first period and exposure of rabbits to very severe heat stress in the second one.

In semen characteristics, the effects of heat stress on reaction time, semen pH, sperm motility, percentages of dead sperm, sperm abnormalities and acrosomal damage, were not significant. However, ejaculate volume, sperm-cell concentration and total sperm output were significantly lower (P < 0·01) under heat stress than under mild conditions. In seminal plasma, effects of heat stress were not significant on total protein, globulin, total lipid, cholesterol, creatinine and alkaline phosphatase. Meanwhile, seminal plasma albumin, acid phosphatase, T3 and cortisol were significantly (P < 0·01 or P < 0·05) lower, while GPT and GOT were significantly (P < 0·01) higher in heat stress than in mild conditions.

Thermoregulatory parameters (respiration rate and temperatures of ear, rectum and skin) and water consumption were significantly (P < 0·01) higher, while consumption of food was significantly (P < 0·01) lower in heat stress than in mild conditions. Blood serum globulin was not affected, while serum total proteins, albumin, glucose, total lipid, cholesterol, acid phosphatase, T3 and cortisol were significantly (P < 0·01 or P < 0·05) lower and urea-N, creatinine, GPT, GOT and alkaline phosphatase were significantly (P < 0·01 or P < 0·05) higher in heat stress than in mild conditions, within the Egyptian subtropical climate.

A total of 104 weanling piglets was used to study the interrelationships between faeces consistency and mucosal integrity, as assessed by specific aminopeptidase and isomaltase-sucrase activity, villus height and crypt depth. Piglets were weaned at 26 (s.d. 1·4) days of age, weighing 8·4 (s.d. 0·70) kg. On the day of weaning (day 0), dissection was performed on one group of eight piglets. The remaining piglets were given restricted amounts of diets containing different protein sources. However, during the first 7 days post weaning 72% of the piglets ate on average less than 0·9 of the amount offered and thus actually had ad libitum access to food. On days 3 or 7 post weaning pigs were weighed and euthanased. Diet composition did not effect small intestine integrity and the data were pooled for further analysis. The weight of the stomach, large intestine and pancreas increased with time post weaning (P < 0·001). Small intestine weight decreased from day 0 to 3 and was increased again on day 7, exceeding the pre-weaning value (P < 0·001). Isomaltase-sucrase and aminopeptidase activities were decreased on days 3 and 7 when compared with day 0. Villus height was decreased after weaning, followed by an increase on day 7 post weaning at the proximal small intestine, but by a further decrease at the mid small intestine (P < 0·001). Crypt depth was increased after weaning (P < 0·001). Faeces consistency was scored twice a day on a scale from 0 to 3 with increasing liquid nature. The average percentage of days during which piglets had more-liquid faeces was 26%. During the 1st week post weaning, 73% of the piglets showed a faeces score of 2 during at least 1 day. Villus height was positively correlated with food intake level, brush-border enzyme activity and dry matter content of the chyme. Villus height was negatively correlated with more-liquid faeces. Crypt depth was positively associated with the weight of various parts of the gastro-intestinal tract. It is concluded that this study supports the concept that food intake by weaned piglets determines villus height in the small intestine and brush-border enzyme production which in turn determine the risk of diarrhoea development.

The management of pastures used by horses poses various problems: swards are often grazed down rapidly, patches of bare ground and refused areas develop. In order to gain a better understanding of the plant-animal interaction behind this problem the influence of sward height on bite dimensions (bite depth, weight, volume, area) of horses was investigated. Perennial ryegrass (Lolium perenne) microswards were grown on artificial substrate to four different heights (3, 8, 15, 19 cm) but the same plant density. Biomass and bulk density for each sward height was determined. Eight horses (predominantly Thoroughbred ×) were allowed to take six bites of each grass height. Bite depth, weight, volume and bite area were calculated.

Bite depth, weight, volume and area were not fixed, but increased with sward height (P < 005). For all sward heights, the horses removed between 51% and 68% of the initial grass length. The horses adjusted their bite dimensions to sward height but did not maximize food intake per bite. The response to sward height might be explained by a preference for easily digested food or the trade-off between energy intake and the cost for food processing.

This experiment suggests that grass height has a major influence on bite dimensions of horses. However there may be more complex factors influencing ingestive behaviour of horses (e.g. age, dietary experience and social behaviour) that have to be considered when horses are grazing pasture.

An 8-week feeding trial was conducted to determine the dietary copper (Cu) requirement of juvenile hybrid tilapia, Oreochromis niloticus 5 O. aureus. Purified diets with eight levels (0, 1, 2, 3, 4, 8, 12 or 20 mg Cu per kg diet) of supplemental Cu were given to tilapia (mean initial weight 0·79±0·03 g). Each diet was given to three replicate groups of fish. The rearing water contained 0·98 µg Cu per l. Weight gain was highest in fish given diets supplemented with 2 mg Cu per kg diet, followed by the group given 1 mg Cu per kg diet, then the unsupplemented control group, and was lowest in the 20 mg Cu per kg diet group. The differences between each of these four groups were significant (P < 0·05). Food efficiency (FE) of fish showed a similar trend to that of weight gain. Blood haemoglobin (Hb) and haematocrit (Hct) concentrations were lowest in fish given ≥ 12 mg Cu per kg diet, followed by fish given the unsupplemented control diet and highest in fish given 2 mg Cu per kg diet (Hb) and 2 and 3 mg Cu per kg diet (Hct). Plasma ceruloplasmin activity was higher in fish given 1 and 2 mg Cu per kg diet, followed by 3 to 12 mg Cu per kg diet and the control group, and lowest in fish given 20 mg Cu per kg diet. The body Cu content in fish generally increased as the dietary Cu supplementation level increased. Analysis by broken-line regression of weight gain percent and by linear regression of the whole-body Cu retention of fish indicated that the adequate dietary Cu concentration in growing tilapia is about 4 mg Cu per kg diet.

The influence of a diet of either pasture or hay on the development of lactic acidosis in sheep was investigated using a grain challenge approach. Twenty-four Merino wethers with a mean live weight of 36·7 (s.e.3·6) kg were used; 12 were adapted to grass pasture and 12 to hay (lucerne and oaten hay, 60: 40) for 4 weeks before being given 1 kg of crushed barley via stomach tube. Six sheep in each group were also given virginiamycin (VM; 50 mg/kg barley) with the grain to test the efficacy of this antibiotic in controlling the bacteria responsible for the development of acidosis. Changes in volatile fatty acid (VFA), pH, lactate and bacterial count in the rumen and faecal pH and dry matter (DM) were measured for a 24-h period following administration of the barley. Daily intakes of hay were measured for a 10-day period following grain engorgement. Total ruminal VFA increased (P < 0·01) over time and tended (P = 0·08) to be higher in sheep adapted to hay than in those adapted to pasture (67·5 v. 59·8 mmol/l). The molar proportions of VFA changed (P < 0·01) over time in favour of propionate in both groups. Ruminal pH was higher (P < 0·001) in pasture-adapted sheep, but declined (P < 0·001) in both groups over time following the introduction of barley. This decline in pH was associated with increases in ruminal concentration of VFA in pasture-adapted sheep and VFA and lactate in hay-adapted sheep. The addition of VM resulted in a higher (P < 0·001) proportion of propionate and a trend towards higher (P = 0·24) faecal pH and DM content. Faecal pH and DM content declined (P < 0·001) over time and was lower for the pasture-adapted sheep. The introduction of either barley alone or barley with VM from both hay and pasture diets increased (P < 0·05) the viable counts of total bacteria, Streptococcus bovis and lactic acid bacteria. Bacterial isolates were purified and identified by complete sequencing of the 16S rRNA gene to determine the predominant bacteria during the overfeeding of grain. Isolates from medium selective for S. bovis were all identified as this species when VM was not given. VM had no effect on counts of viable bacteria, but inhibited the growth of S. bovis.

This study has shown that sheep given hay are more susceptible to lactic acidosis, the signs of which can be reduced by VM.

Better understanding of how animals regulate their intake may be gained by analysis of feeding behaviour. This is often recorded in terms of feeding events, e.g. visits to feeders, which can be clustered into meals. This enables calculation of the probability of animals starting a meal in relation to time since the last meal, which is thought to give insight into food intake regulation. Starting probabilities are often calculated with pooled data but recent work suggests that pooling may strongly affect conclusions.

In this study we analysed feeding behaviour of cows to investigate how previous conclusions about feeding behaviour may have been affected by pooling. Using parameters derived from experimental data, we constructed simulation models to further explore under what circumstances pooling, either across day and night or across individuals, could affect the interpretation of starting probabilities. Data were simulated to explore the consequences of pooling as either the proportion of meals occurring during the day or the individual variation in their mean number of meals per 24 h changed. Simulation allowed us to extend the analysis of the consequences of pooling for the interpretation of starting probabilities.

Analysis of experimental data, collected with 16 dairy cows, showed that they ate a mean of six meals per 24 h. Individual variation resulted in a proportional CV of the individual mean number of meals per 24 h of 0·14. Cows ate a mean proportion of 0·59 of their meals during the day. Analysis of experimental data suggested that pooling, conducted in previous studies, has probably led to a quantitative underestimation of the increase in starting probability with time since the last meal but not a qualitative misinterpretation of the direction of change in the starting probability.

Simulation studies showed that pooling had no serious consequences when the mean number of meals per 24 h, or the variation about this mean, was low. However, as the number of meals per 24 h and variation increased, pooling led to conclusions that may wholly misrepresent both magnitude and direction of the change in starting probabilities calculated separately for the individuals or for day and night. This may explain why the results of some published studies seem not to agree with biological principles of food intake regulation.

A first group of three horses was given diet 1 (D1) allowing 1180 g per 100 kg body weight (BW) of a pelleted food rich in fibre (P1) and 556 g per 100 kg BW of straw during a 20-day period to allow for adaptation. A second group of four horses were given diet 2 (D2) allowing 1180 g per 100 kg BW of a pelleted food rich in cereals (P2) and 1000 g per 100 kg BW of meadow hay during the same period. Digesta was collected from the stomach, duodenum, jejunum, ileum, caecum, right ventral colon, left ventral colon, left dorsal colon, right dorsal colon, and small colon, and faeces were collected under general anaesthesia 2·5 h after the ingestion of the morning pelleted meal. The concentration of total anaerobic, cellulolytic and lactic acid-utilizing bacteria, lactobacilli and streptococci were determined in all these segments except for the duodenum, left ventral colon, right dorsal colon and small colon. D-/L-lactic acid, volatile fatty acids and pH were measured in all anatomic segments of the digestive tract (from stomach to small colon). The caecal concentration of total anaerobic bacteria was the lowest (7·9 5 107 colony-forming units (c f. u.) per ml), whereas that of the stomach was the highest (1·4 5 109 c f. u. per ml) (P < 0·001). Cellulolytic bacteria did not exceed 3·0 5 102 c f u. per ml in the ante-caecal segments whereas in the hindgut the average concentration was 5·3 x 105 c f u. per ml (P < 0·001). Likewise, VFA concentrations were also greater in the large intestine (on average, 96·3 mmol/l v. 8·8 mmol/l in the ante-caecal segments) (P < 0·001), confirming the limited extent of fibre degradation in these ante-caecal segments. Lactobacilli, streptococci and lactate-utilizing bacteria colonized all the digestive tract; the stomach and the small intestine tended to host the greatest numbers of these bacteria, which suggests a high interference of micro-organisms with the digestion of readily fermentable carbohydrates. Compared with the other ante-caecal segments, the stomach ecosystem seemed the most affected by the composition of the last pelleted meal ingested: the concentrations of lactobacilli and lactate-utilizing bacteria were higher (P < 0·05) with P2. The lower concentration of D-/L-lactate with P2 (P < 0·05) was concomitant with a greater proportion of propionate (P < 0·05), probably related to a greater fermentation of lactate. In the large intestine of horses given D2, cellulolytic bacteria tended to be lower, whereas VFA concentrations were higher (P < 0·05). The lower [NDF/starch] ratio of D2 was probably less propitious for the proliferation of cellulolytic bacteria but was compensated by the higher cellulose intake brought by the hay.

Two weaning diets (C and S) and three weaning ages (21, 25, and 28 days) were compared in a two factorial arrangement to evaluate their effect on growth performance, body composition and caecal fermentation activity of young rabbits. One hundred litters born the same day from multiparous does were used. Sixty litters were early weaned at 21, 25 and 28 days of age (20 litters per weaning age), put in collective cages (nine kits per cage) (W21, W25, and W28 litters) and offered the control diet C (crude protein (CP) : 175 g/kg dry matter (DM); ether extract : 20 g/kg DM; starch : 157 g/kg DM; acid-detergent lignin (ADL) : 60 g/kg DM; digestible energy (DE) : 11·08 MJ/kg DM) or the starter diet S (CP : 173 g/kg DM; ether extract : 41 g/kg DM; starch : 112 g/kg DM; ADL : 51 g/kg DM; DE : 11·31 MJ/kg DM). At 32 days of age, 180 early weaned rabbits (three rabbits from each of the 60 litters above) were selected : 60 animals were slaughtered; 120 animals were placed into individual cages and offered a fattening diet (CP : 166 g/kg DM; ether extract : 23 g/kg DM; starch : 177 g/kg DM; ADL : 49 g/kg DM; DE : 11·26 MJ/kg DM) from 32 to 56 days of age. At 56 days of age, another 60 representative rabbits were slaughtered. The administration of diet S to the early weaned rabbits increased litter weight at 32 days (6160 v. 6027 g; P <005) and gain to food ratio from weaning to 32 days (752 v 666 g/kg; P <0001) compared with diet C. Moreover, empty bodies (EB) of S rabbits were fatter (fat : 45 v. 41 g/kg; P = 001) and had greater energy content (5·92 v 5·71 MJ/kg; P <001). At 56 days of age, no residual effect of the diet was recorded. Weaning age affected growth performance, body composition and caecal fermentation at 32 days of age : EB weight (P <005) and EB protein concentration increased (from 164 to 168 g/kg, P <0·01) while caecal volatile fatty acid concentration decreased (from 71·7 to 53·8 mmol/l; P <0·01) when weaning age was increased from 21 to 28 days. At 56 days of age, no effect (P > 0·05) of weaning age was recorded on growth performance or caecal fermentation traits, but EB protein remained lower in the earliest weaned rabbits (P <0·05). In conclusion, feeding a high-fat low-starch diet to early weaned rabbits stimulated growth and body fat and energy retention of kits at 32 days of age with no effect on caecal fermentation. The early weaning successfully performed at 21 days of age strongly stimulated caecal fermentation but reduced body protein reserves.

The model incorporates, amongst its novel components, variable efficiency coefficients in the simulation of the responses of growing pigs to nutrient inputs, and thereby increases the accuracy and efficacy of control of feeding and nitrate excretion. The model determines (rather than is presented with) net energy and required amino acid level and balance. The estimation of protein turn-over as a function of rate of protein retention, protein mass and the maturity of the pig was found to be central to both the energy (ATP) and protein economy. Protein turn-over varied from around 0·14 to 0·08 of the protein mass depending upon the size of the pig. Efficiencies of energy yield from lipid, starch (and sugar), protein and (fibre-derived) volatile fatty acids were calculated to be 0·98, 0·86, 0·56 and 0·58 for ATP production and 0·90, 0·70, 0·50, and 0·44 for lipid retention, respectively. The maximum efficiency of use of ileal digestible amino acids was determined as around 0·85. The energy cost of protein synthesis was equivalent to 4·2 MJ metabolizable energy (ME) per kg, and the efficiency of use of ME for protein retention varied from 0·55 to 0·40 depending on the protein mass of the pig. The components of the model and the biochemical drivers are described in detail, and proof of principle of the main elements is presented. The model is different in its architecture to other published simulation models, and is considered to add to the present knowledge base in this discipline.

Sixteen early to mid lactation Finnish Ayrshire dairy cows were used in a cyclic change-over experiment with four 21-day experimental periods and a 4 5 2 factorial arrangement of treatments to evaluate the effects of heat-treated rapeseed expeller and solvent-extracted soya-bean meal protein supplements on animal performance. Dietary treatments consisted of grass silage offered ad libitum supplemented with a fixed amount of a cereal based concentrate (10 kg/day on a fresh weight basis) containing 120, 150, 180 or 210 g crude protein (CP) per kg dry matter (DM). Concentrate CP content was manipulated by replacement of basal ingredients (g/kg) with either rapeseed expeller (R; 120, 240 and 360) or soya-bean meal (S; 80, 160 and 240). Increases in concentrate CP stimulated linear increases (P < 0·05) in silage intake (mean 22·5 and 23·8 g DM per g/kg increase in dietary CP content, for R and S, respectively) and milk production. Concentrate inclusion of rapeseed expeller elicited higher (P < 0·01) milk yield and milk protein output responses (mean 108 and 3·71 g/day per g/kg DM increase in dietary CP content) than soya-bean meal (corresponding values 62 and 2·57). Improvements in the apparent utilization of dietary nitrogen for milk protein synthesis (mean 0·282 and 0·274, for R and S, respectively) were associated with higher (P < 0·05) plasma concentrations of histidine, branched-chain, essential and total amino acids (35, 482, 902 and 2240 and 26, 410, 800 and 2119 µmol/l, respectively) and lower (P < 0·01) concentrations of urea (corresponding values 4·11 and 4·52 mmol/l). Heat-treated rapeseed expeller proved to be a more effective protein supplement than solvent-extracted soya-bean meal for cows offered grass silage-based diets.

Dairy operations located in many temperate climates experience a decline in milk production associated with short-term moderate heat stress during the summer months. The duration and intensity of this heat stress differs dramatically from the sustained, intense heat experienced in many tropical and subtropical countries where the vast majority of heat stress research has been conducted. As such, many of the strategies utilized to ameliorate production losses associated with sustained, intense heat may not be effective in temperate climates. The objective of this research was to characterize the production responses of lactating dairy cows during and after short-term, moderate heat exposure and, to determine if feeding a fungal culture, Aspergillus oryzae, during a 5-day heat stress period, could effectively alleviate the associated production losses. In a two-period, cross-over design, eight mature lactating cows were given a total mixed ration with or without Aspergillus oryzae. Each 15-day period consisted of a 5-day thermoneutral phase, a 5-day heat stress phase and a 5-day thermoneutral recovery phase. When exposed to moderate heat stress for a 5-day period, cows experienced a rise in vaginal temperature and a decline in dry-matter intake. Following the 5-day heat stress phase, milk yield declined by a factor of 0·09. Supplementation with Aspergillus oryzae had no effect on vaginal temperature, dry-matter intake, water intake, milk yield or milk components. These data indicate that short-term, moderate heat stress, which occurs during the spring and summer months in temperate climates, will significantly decrease production in the lactating cow. Addition of fungal cultures to the diet during the period of imposed heat did not ameliorate production losses associated with this type of heat stress.

Supplementary salt is often added to the diet of sheep by including it in concentrate food, but an alternative is to soak their forage in a weak salt solution, which could prevent the sudden influx of large doses of sodium(Na) to the rumen. An experiment was conducted to compare low and moderate levels of salt in forage with moderate and high levels added to the concentrate. Twenty sheep were housed in individual chambers equipped for faeces and urine collection and offered fresh grass and concentrate, with the salt being added to the grass by soaking in salt water and to the concentrate by direct mixing. The grass for sheep offered the supplementary Na in concentrates and for a control treatment was soaked in water without salt. Grass was offered in two daily meals and was available ad libitum, and concentrates were offered at a restricted level just before the first feeding of grass. Adding salt at the low and moderate levels to the water in which the grass was soaked increased the Na intake from 1·1 g/day (the control treatment) to 2·1 and 3·8 g/day, respectively, and reduced the Mg and Ca contents in the grass, compared with grass soaked in unsalted water. Adding salt to the concentrate at moderate and high levels increased Na intake to 3·7 and 5·9 g/day, respectively. Grass dry matter (DM) intakes were increased by adding Na to the concentrates, but not to the grass, and DM digestibility was increased in all salt supplement treatments except the high level added to the concentrate. The apparent absorption of Na was increased in proportion to the amount of Na added to the diet and that of K was increased at the moderate and high levels. The apparent absorption and retention of Mg and Ca were decreased at the low level of Na supplementation in herbage. It is concluded that the potential benefits of adding salt to the diet, namely increased food intake and digestibility and increased mineral absorption, are dependent on the level of addition and the method of adding it.