Four adult ewes (mean weight 42·6 kg) fitted with oesophageal fistulae were given 5 mmol/day ofallantoin or saline solutions by intrajugular continuous infusion. The experiment was a randomized cross-over design, with two consecutive 3-day infusion periods. One kg/day fresh matter of either chopped or pelleted fescue hay was distributed over 12 meals and salivary flow estimated from dilution of Co-EDTA infused into the buccal cavity. Allantoin infusion resulted in a rapid increase in its plasma concentration (84 to 128 (s.e. 1·5) μmol/l) and urinary excretion (9·6 to 13·3 (s.e. 0·18) mmol/day) without significant differences between diets. Salivary allantoin also increased (4·6 to 6·4 (s.e. 0·60) ymol/1) in response to infusion, although the concentration of total purine derivatives in saliva was only proportionately 0·08 that of plasma. Renal and salivary clearance of oxypurines, allantoin (78 (s.e. 5·0) ml/min and 13 (s.e. 0·7) ml/h), uric acid (466 (s.e. 98·0) ml/min and 45 (s.e. 9·8) ml/h) and creatinine (104 (s.e. 3·0) ml/min and 14 (s.e. 1·1) ml/h) were constant, irrespective of diet and infusion treatments. Urinary recovery of infused allantoin averaged 0·78 (s.e. 0·031) but salivary secretion, equivalent to about 0·003 of urinary losses, was not the explanation for the incomplete recovery.

In two experiments prepubertal gilts were injected with a combination of 400 international units pregnant mare's serum gonadotrophin and 200 international units human chorionic gonadotrophin. The gilts were housed either in contact with or isolated from mature boars. Data were obtained of ovarian activity determined immediately after gonadotrophin treatment and at the anticipated time of the second oestrus.

All treated gilts ovulated in response to the treatment and 83% displayed oestrus. Ovulation rate varied both within and between experiments, in experiment 1 the range being 7 to 19 corpora lutea and in experiment 2, between 5 to >30 corpora lutea. Four distinct types of behaviour were observed at the time of the second cycle: ovulation associated with oestrus; ovulation without oestrus; oestrus but no ovulation; and a return to a prepubertal state with no oestrus or ovulation. The presence of boars enhanced the maintenance of cyclic activity. Overall, more gilts displayed a second oestrus (33/39 v. 19/41, X2 = 11·2, P<0·001), and more had a second ovulation (32/39 v. 24/41, X2=4·2, P<0·05) when boars were run with the gilts.

From observations made over 3 years on a flock of Welsh Mountain sheep kept at 210 to 330m above sea level there was no indication that ewes especially sought shelter for lambing when wind speed was under 8 km/hr or the Kata cooling power was below 20 millical/cm2 per sec. When wind speed or cooling power rose, lambing sites chosen by the ewes were progressively more sheltered. Average wind speed and Kata cooling power at sheep height at lambing sites were about 14 km/hr and 35 millical/cm2 per sec.

Variability in wind speed and cooling power at an unsheltered site accounted for only 24% and 18% of the variability in these measures at the lambing sites, thus the lambing sites chosen depended to a considerable extent upon other factors, which are discussed.

The environment at lambing sites chosen by ewes cannot be taken as the optimum. No attempt was made to correlate lambing site environment with ewe or lamb performance.

In trials with 64 pigs growing from 37 to 60 kg or from 65 to 88 kg growth rate and food conversion were not affected by either a 10°C or a 20°C range in diurnal air temperature cycle compared with a constant temperature equal to the mean of the cycle when the mean temperatures were optimal. However, with a constant temperature and cycle mean at 6°C above optimum, performance declined with a 20°C range cycle.

Fumonisins, a group of toxic metabolites produced by the genus Fusarium, are known to be consumed by farm animals and are the causative agent or a suspected contributing factor in farm animal diseases. Pigs are particularly susceptible to fumonisins. Reproductive inefficiency is recognized as the most costly limiting constraint to efficient animal production. To account for potential reproductive effects of fumonisin in boars, dietary fumonisin B1 (FB1) was fed to 24 male Large White weanling pigs, 8 to 9 weeks of age. The animals were randomly assigned to four diets containing 5.0, 10.0, 15.0 and 0.2 mg FB1/kg constituting diets 1, 2, 3 and control diet, respectively. After 6 months, semen samples were collected from the pubertal boars and analysed. After the semen collection, all the pubertal boars were killed by decapitation, their reproductive systems dissected and the weights of the testes and epididymides as well as the volumes of the testes recorded. Dietary FB1 did not influence both the relative weights of the testes and epididymides as well as the volumes of the testes. Except for the semen volume and spermatozoa morphological abnormalities, all the semen characteristics studied decreased in a dose-dependent manner and the decrease was statistically significant (P < 0.05). The sperm concentration, total sperm and motile sperm per ejaculate of the animals on diet 3 were 83.3%, 79.1% and 59.6% of the controls, respectively. The dietary FB1 levels influenced the mass activities of the semen, which ranged from very turbulent motion for animals on the control diet to absence of wave motion for those on diet 3. The study revealed that male weanling pigs for breeding should not be exposed to dietary FB1 higher than 5 mg/kg for optimum reproductive performance. The results of this present study suggest that the recommendation of 10 mg/kg by the United States Food and Drug Administration as the maximum level of total dietary fumonisins was above the no-observable-effect level of dietary fumonisin for swine.

The ingenious biochemical system, which we generally call heredity, directs the body development and regulates the reaction of the individual in relation to the environmental conditions. It is this genetically determined adaptiveness of the individual which makes it possible for organic life to survive even when the climatic conditions and the supply of nutriment vary within wide limits in nature.

The interaction of heredity and environment involves several problems of vital importance for animal production. One such problem is the influence of level of nutrition during the rearing period on body development, fertility, milk production and longevity. When investigating the relative importance of heredity and various environmental factors on the production traits in dairy cattle, we have concentrated much of our effort on this special problem.

A study was conducted to evaluate the effect of decreasing age of puberty on lifetime productivity in sows. Two lines of gilts from the Nebraska Gene Pool population were used in this study: a line that had been selected for decreased age at puberty (AP) and a line in which selection had been random (RS). The study was conducted in two parts. In part one, 75 gilts were mated at second oestrus and the productivity measured over five parities. A second experiment utilizing 68 gilts was conducted to provide further data for comparing litter size at parity 1, and also to compare ovulation rates in the two lines at second oestrus. Results showed that litter size was similar in both lines across parities. After five parities the percentage of sows farrowing relative to parity 1 was 58-8% for the AP line but only 39·4% for the RS line (P = 0·17). Litter birth weight, litter size and weight at 21 days, number weaned, and lactation food consumption were similar for both lines. Lactation weight loss was not significantly different between the two lines (60·9 (s.e. 5·9) v. 527 (s.e. 5·0) kg, for RS and AP gilts, respectively) but was consistent with the slightly longer weaning to remating intervals in the RS line (7·8 (s.e. 0·7) v. 6·6 (s.e. 0·7) days, P = 0·22). Ovulation rate at second oestrus did not differ between the two lines (14·1 (s.e. 0·9) v. 14·3 (s.e. 0·5), for RS and AP gilts, respectively). The regression of mean accumulative productivity on time was in favour of the AP line (P = 0·05). These results suggest that reproductive performance is not impaired in gilts which have been selected to reach puberty at earlier ages, and productivity at a specific age may be enhanced.

The objective of this study was to investigate the effect of orally administered spermine at various doses on intestinal maturation in sucking piglets. Thirty-six 11-day-old sucking piglets were assigned randomly to one of six treatments to receive via a stomach tube 0, 0·1, 0·2, 0·3, 0·4, or 0·5 mmol spermine per kg live weight (LW) per day for 3 days. At day 14 of age, duodenum, jejunum and ileum were obtained for biochemical and morphological analysis. Increasing the dose of orally administered spermine increased intestinal weight (linear effect, P<0·01), mucosal weight (linear effect, P<0·05), and mucosal protein, DNA and RNA contents of the duodenum (linear effect, P≤0·01) and jejunum (linear effect, P<0·01). Elevating spermine doses also enhanced (linear effect, P≤0·02) the specific activities of maltase and sucrase but decreased (linear effect, P<0·01) lactase specific activity in the jejunum and duodenum. Furthermore, augmenting oral doses of spermine increased crypt depth and villus width but reduced villus height in the jejunum (linear effect, P<0·05) and duodenum (linear effect, P<0·01). For most measurements, the effects were observed at the oral spermine doses of 0·3 to 0·5 mmol/kg LW per day. Collectively, the results show that oral administration of optimal doses of spermine to 11-day-old sucking piglets induces precocious intestinal maturation and promotes intestinal growth.

Dehydration can be extremely damaging to the performance and welfare of indigenous chickens. The effect of water restriction on haematological and biochemical parameters was compared in Naked Neck (NNK) and Ovambo (OVB) chickens. A total of 54 8-week-old pullets each of NNK and OVB chickens with an initial average weight of 641 ± 10 g/bird were randomly assigned to three water intake treatments with three replications, each having six birds. The water restriction treatments were ad libitum, 70% and 40% of ad libitum intake. Nine experimental pens with a floor space of 3.3 m2 per strain were used. Feed was provided ad libitum. Packed cell volume (PCV), erythrocyte count (RBC), mean corpuscular volume (MCV) and total leucocyte count (WBC), and biochemical parameters (uric acid (UA)), creatinine (CREAT), total protein (TP), albumin (ALB), globulin (GLOB), triglyceride (TGA), total cholesterol (TC), high- (HDLC) and low- (LDLC) density lipoprotein cholesterol and activity of alanine transaminase (ALT), alkaline phosphatase (ALP) and aspartate transaminase (AST) were determined from blood collected after 60 days of water restriction. PCV was higher (P < 0.05) in NNK than OVB chickens offered water ad libitum, but similar in birds offered 70% and 40% of ad libitum. There were no differences in RBC and MCV values between strains, but MCV was higher in birds on 40% than 70% of ad libitum water intake, irrespective of strain. Naked neck chickens had higher (P < 0.05) WBC values than OVB at 40% restriction level, but lower WBC than OVB at 70% water restriction level. UA, CREAT, TGA, TC, LDLC, TP and GLOB increased (P < 0.05) with each increment in water restriction, but the increase in CREAT and TC was more pronounced in OVB than NNK chickens. The opposite was observed for UA. ALT activity indicated that liver function was not affected by water restriction. It was concluded that the two strains can withstand up to 40% of ad libitum water restriction, but NNK tolerated water stress better than OVB chickens.

Significant differences in the estimation of amino acid requirements exist between the available factorial methods. This study aimed to compare current factorial models used to estimate the individual and population standardised ileal digestible (SID) lysine (Lys) requirements of growing pigs during a 26-day feeding phase. Individual daily feed intake and BW data from 40 high-performance pigs (25-kg initial BW) were smoothed by linear regression. Body weight gain was constant (regression slope not different from 0) for all the pigs. The CV of the SID Lys requirements ranged from 22% at the beginning of the trial to 8% at the end. The population Brazilian tables (BT-2017) and National Research Council (NRC-2012) SID Lys requirements for the average pig were 16% higher than the average requirement estimated by the individual precision-feeding model (IPF), but similar to the estimated for the population assuming that population requirements are those of the 80th-percentile pig of the population (IPF-80). Meaning that, the IPF-80, BT-2017, and NRC-2012 models would yield similar recommendations when pigs are group-fed in conventional multi-phase systems. Additionally, the IPF-80 estimates are independent of the phase length, whereas the BT-2017 and NRC-2012 models use average population values in the middle of the feeding phase for the calculations and therefore, conventional requirement estimations decrease as the length of the feeding phase increases. In conclusion, the BT-2017 and NRC-2012 methods were calibrated for maximum population responses, which explains why these methods yield higher values than those estimated for the average pig by the IPF model. This study shows the limitations of conventional factorial methods to estimate amino acid requirements for precision-feeding systems.

Some routine handling procedures can produce stress in farm animals, and an adequate control of these stressors is important to avoid the negative effects on animal health and production. The measurement of biomarkers in saliva can be a suitable tool for the evaluation and control of stress. In this report, lipase, butyrylcholinesterase (BChE), total esterase (TEA) and adenosine deaminase (ADA) activities in the saliva of sheep were evaluated as biomarkers of stress. For this purpose, they were measured after inducing stress by facing a dog (experiment 1) and shearing (experiment 2), and comparing them to other stress salivary biomarkers such as α-amylase (sAA) and cortisol, as well as heart rate (HR). Each analyte was measured at the basal time, and during and just after the end of the stressful stimulus, and at various times for the first hour after the period of stress induction. Values were compared with those obtained from a control group. Lipase was the only analyte that showed significant changes between the stress and the control group in both experiments. Although TEA and ADA increased after stress, no significant differences were seen compared with the control group. Lipase was correlated highly with sAA and HR, in experiment 1; and correlated moderately with cortisol and HR in experiment 2. Lipase showed the greatest percentage increase after the stressful stimuli and less overlap with the control group in the two experiments. From the results of this study it can be concluded that lipase, TEA, BChE and ADA are enzymes present in the saliva of sheep and that they can be measured by using simple and fast colorimetric methods. Further studies should be undertaken with regard to the possible application of lipase as a biomarker of stress in sheep.

It is proper, on the occasion of this lecture, to recall the man whose name it bears. John Hammond, the first president of our Society, was known to many of us, all of us have been influenced by his ideas, and the animal industries of this country, and indeed the world, have been transformed as a result of the work he and his small band of colleagues and students carried out at Cambridge, mostly before the Second World War. If anyone can be called the ‘onlie begetter’ of modern animal production it is John Hammond.

This experiment tested the hypothesis that a lift in the nutrition of ewes, before lambing, to increase colostrum production would enhance lamb survival. In all, 261 mature Corriedale ewes, each with a single fetus from a synchronised mating, grazed native pasture to day 130 after mating; at which point they were weighed, condition scored and allocated to graze either native pasture or a pasture dominant with Lotus uliginosus. Five days later (14 days before the expected start of lambing) the ewes were allocated to one of four treatments and fed: (i) native pasture alone, (ii) native pasture plus a commercial high-energy lick, (iii) L. uliginosus pasture alone or (iv) L. uliginosus pasture plus whole maize. The weight, viscosity and concentration of components and immunoglobulin G in the colostrum that had accumulated at parturition, were measured for 10 ewes in each treatment. The lambs that survived to 20 days of age from the 221 ewes that were not milked, were recorded. The ewes supplemented with the lick or maize grain and those that grazed the L. uliginosus pasture alone accumulated two to three times more colostrum at birth than the ewes that grazed native pasture alone (396, 635 and 662 g v. 206 g; P < 0.01). The colostrum from the ewes that grazed only native pasture was more viscous (lower score) than that from the ewes supplemented with the lick or maize grain or the ewes that grazed the L. uliginosus pasture alone (scores of 4.1 v. 6.2, 6.5 and 6.4, P < 0.001) and, not surprisingly, the concentration of lactose in the colostrum of the ewes fed only native pasture was also much lower (1.1% v. 3.0%, 2.8% and 2.6%; P < 0.001)he survival of lambs from the ewes fed only native pasture was less than that of the lambs from ewes fed native pasture plus the commercial lick (81.8% v. 95.5%; P < 0.05) or the L. uliginosus pasture alone (92.4%, P < 0.05), and also tended to be lower than that for lambs born to ewes fed L. uliginosus pasture plus maize (91.8%, P = 0.08). The concentration of glucose in the blood of the lambs from the ewes that grazed only native pasture was lower than that of the other lambs (42.1 v. 60.2 ng/ml, P = 0.012). We conclude that the marked increase in colostrum production associated with the lift in ewe nutrition, just prior to lambing, enhanced lamb survival.

Historically, pre-pubertal development of the bovine mammary gland (MG) has received little attention compared to later development. Recent evidence suggests not only that this period represents a very active time in the development of the MG but also that the first 90 days of life can partially dictate future productivity of the lactating cow. The MG, often considered quiescent during early life (first 3 months), is now known to increase in size by over 60-fold in the same period. The importance of sex steroids in MG development is well classified, but a complex signaling network exists among estrogen, progesterone and other growth factors and hormones. Complicating our understanding of this developmental period further is the discovery that pre-weaning nutrition of the calf not only influences the growth of the mammary parenchyma but may also alter the way in which it responds to mammogenic stimuli. Recent data suggest that feeding calves a higher plane of nutrition improves the ability of the mammary epithelium to respond to estradiol and also alters the way in which the mammary parenchyma and fat pad communicate. It is clear that early life nutrition, although able to influence the MG, is still poorly understood mechanistically. For example, additional evidence suggests that increased feeding rates in early life alter the morphology of myoepithelial cells in the mammary epithelium. Further data have also suggested a role for other cell types, such as immune cells, in the penetration of the mammary parenchyma into the fat pad during the early life development of the MG suggesting that mammary development is not only controlled by the local tissue population (parenchyma and fat pad) but perhaps systemically by other tissue types (i.e., immune system). Understanding the roles of these various stimuli and signaling pathways as they relate to the development of the MG in early life may hold the key to unlocking the potential for the optimal development of this crucial organ and, in turn, may lead to improvements in other phases of mammary development and milk yield potential.

The gut health of poultry is closely associated with feeds and feeding. The experiment was conducted to the effect of crude glycerol addition to diets of male broilers on the bacterial microflora and morphology of their small intestines (duodenum, jejunum and ileum). A total of 120 Ross 308 broiler chicks received diets containing 0% (GLY 0), 4% (GLY 4) or 8% (GLY 8) crude glycerol for 42 days. The presence of Coliform bacteria and Enterobacteria was reduced in the duodenal tract of the broilers of GLY 4 (P<0.001); however, the presence of Staphylococci/Micrococci in the GLY 8 was reduced relative to the other groups (P<0.001). The presence of Salmonella spp. decreased in conjunction with the increasing quantities of glycerol (P<0.001). Analysis of the data regarding gut morphology (epithelial cell thickness, villi length and width, and crypt length and width) indicated that the glycerol levels fed to the different groups of broilers represented statistically different results in the small intestine. In general, whereas the diet with 4% glycerol statistically affected the investigated parameters of the gut, the diet with 8% glycerol statistically affected some segments of the broiler intestines.

Feed production is a significant source of greenhouse gas (GHG) emissions from dairy production and demands large arable and pasture acreage. This study analysed how regional conditions influence GHG emissions of dairy feed rations in a life cycle perspective, that is the carbon footprint (CF) and the land area required. Factors assessed included regional climate variations, grass/clover silage nutrient quality, feedstuff availability, crop yield and feed losses. Using the Nordic feed evaluation model NorFor, rations were optimised for different phases of lactation, dry and growing periods for older cows, first calvers and heifers by regional feed advisors and combined to annual herd rations. Feed production data at farm level were based on national statistics and studies. CF estimates followed standards for life cycle assessment and used emissions factors provided by IPCC. The functional unit was ‘feed consumption to produce 1 kg energy corrected milk (ECM) from a cow with annual milk yield of 9 900 kg ECM including replacement animals and feed losses’. Feed ration CF varied from 417 to 531 g CO2 e/kg ECM. Grass/clover silage contributed more than 50% of total GHG emissions. Use of higher quality silage increased ration CF by up to 5% as a result of an additional cut and increased rates of synthetic N-fertiliser. Domestically produced horse bean (Vicia faba), by-products from the sugar industry and maize silage were included in the rations with the lowest CF, but horse bean significantly increased ration land requirement. Rations required between 1.4 to 2 m2 cropland and 0.1 to 0.2 m2/kg semi-natural grassland per kg ECM and year. Higher yield levels reduced ration total CF. Inclusion of GHG emissions from land use change associated with Brazilian soya feed significantly increased ration CF. Ration CF and land use depended on ration composition, which was highly influenced by the regional availability and production of feedstuffs. The impact of individual feedstuffs on ration CF varies due to, for example, cultivation practices and climate conditions and feedstuffs should therefore be assessed in a ration and regional perspective before being used to decrease milk CF. Land use efficiency should be considered together with ration CF, as these can generate goal conflicts.

Plasma hormone concentrations and metabolite responses to changes in energy equilibrium were measured in experiments designed to compare a) Hereford × Friesian with Friesian calves and b) Friesian calves sired by bulls with a high level of Improved Contemporary Comparison with those sired by bulls of a low level. The concentration of thyroxine and triiodothyronine tended to be greater in calves of higher dairy merit. The concentration of growth hormone was largely unrelated to dairy merit in the circumstances studied. The concentration of insulin was greater in Hereford × Friesian than in Friesian calves following feeding and following the injection of propionate. Responses to the injection of insulin and of growth hormone (as measured by changes in the plasma concentration of urea nitrogen, free fatty acids, glucose or the other hormone) were little affected by the level of Improved Contemporary Comparison of a calfs sire.

It was concluded that the thyroid system and the response of insulin to perturbation of energy balance may provide criteria of genetic merit for milk production which are neither age- nor sex-limited.

A consequence of increasing litter size in sheep is that a portion of the lambs have to be reared artificially. Detailed information about the pattern of milk consumption of artificially reared lambs would help improve their management. The purpose of this study is to describe the individual and group feeding behaviour of 94 Romane artificially reared lambs from 5 to 28 days of age using an electronic automatic lamb feeder. Animals were located in four pens of 8 to 15 lambs of similar age with one teat per pen. They were fed ad libitum. In our experimental situation (group rearing, continuous lightning) on average a lamb made 1.4±0.7 visits to the teat per meal and 9.5±3 meals per day. Mean meal duration was 247±158 s and the mean daily time spent feeding was 38±25 min. The mean quantity of milk intake was 176±132 ml per meal and 1.68±0.8 l per day. With age, the number of daily meals and their duration decreased while the quantity of milk consumed per meal and per day increased. Females tended to make more visits to the teat per meal and perform more meals per day but their milk consumption per meal was lower. The feed conversion ratio was 1.36±0.2. Synchrony in feeding (group meal) was estimated as the percentage of lambs that wanted to access the teat within the same short period (relative group meal size). On average 65% of lambs in the pen wanted to access the teat within the same period, but for 35% of group meals the relative group meal size was >90%. There was no consistency in the order in which lambs accessed the teat during a group meal. Our evaluation suggested that electronic automatic lamb feeders are tools that can provide, on a large scale, data describing the feeding behaviour of artificially reared lambs. It is then possible to study factors influencing these traits in order to improve the outcome of artificially reared lambs.

Silymarin is an extract from the plant milk thistle that was shown to have antioxidant and hyperprolactinemic properties. Taking into account the essential role of prolactin for lactating sows and the systemic oxidative stress occurring during lactation, it is of interest to investigate the potential beneficial effects of silymarin on lactating sows. A study was therefore carried out to determine the effects of providing either 1 or 8 g/day of the plant extract silymarin to lactating sows. Sows in first, second or third parity were fed conventional diets during gestation and, at farrowing, were assigned as controls (CTL, n=33), or were fed 1 g/day (SYL1, n=33) or 8 g/day (SYL8, n=33) of silymarin. The silymarin was provided in two equal amounts per day, and was fed throughout a 20-day lactation. The performance of sows and their litters was assessed and circulating concentrations of prolactin (days 7 and 18), urea (days 7 and 18) and oxidative status, via protein carbonyls and superoxide dismutase activity (day 18), were measured in sows. Milk samples were obtained on day 18 to measure standard composition. There was no effect of silymarin (P>0.10) on circulating prolactin or urea, or on oxidative damage to proteins or antioxidant potential in sows. Lactation feed intake, backfat and BW of sows were unaffected by treatment (P>0.10) as was the case for milk composition and piglet growth (P>0.10). Results demonstrate that providing up to 8 g/day of the plant extract silymarin to lactating sows had no beneficial effects in terms of circulating prolactin concentrations or oxidative status of sows, or in terms of performances of sows and their litters.

A study was carried out to evaluate the effect of horizontal walking upon CO2 production rate by the carbon dioxide dilution rate technique. This was used as an indicator of animal energy expenditure. Two groups of three 18-month-old Aberdeen-Angus steers were assigned to two experiments. Average weights were 290 (s.e. 7·6) kg and 285 (s.e. 1·0) kg for experiments 1 and 2 respectively. Animals were allocated to individual pens and given 5·0 and 4·5 kg dry matter of a mixed diet for experiments 1 and 2 respectively. After a 45-day training period they were assigned to three walking treatments: 0 (T0), 3 (T3) and 6 (T2) km at 3 km/hfor 3 days in a Latin square design (3 × 3). 14C labelled sodium bicarbonate (5·4 μCi/h), diluted in carbonate-bicarbonate buffer sterile solution 0·1 mol/l, was infused for 92 h intraperitoneally with portable peristaltic pumps carried by the animals. The CO2 production rate was calculated as the ratio between the rate of infusion (μCi/h) and the specific activity of CO2 (μCi/ml CO2) in saliva samples, which were taken, in experiment 1, as an average of the day (09.00 to 16.00 h) and the night (16.00 to 09.00 h of the following day). In experiment 2 the day was divided as follows: prior to activity (09.00 to 13.00 h), activity (14.00 and 15.00 h) and post activity (16.00 h). CO2 production rate (ml CO2 per h per kg M0·75) at resting was 817 (412 kj/kg M0·75), increasing during walking to 1·46 of the resting level (T1 and T2, experiment 2) with no differences between the 1st and 2nd h of activity. One hour post activity, the CO2 production rate returned in T2 to the level of T0 but in T2 remained at 1·28 times that of T0. The average CO2 production rate during a complete day or night (experiment 1) was not affected significantly by the activity. Assuming that CO2 production rate during walking is 1·46 of resting (experiment 2) and remains at that level even at lower speeds, it can be estimated that a daily 6 km walk would increase resting energy expenditure from 1·04 when walking takes 2 h, as in this experiment (3 km/h), to 1·11 when the animal spends 6h(1 km/h).