Due to genetic selection for fast growth and high breast meat yield, commercial strains of broiler chickens and broiler breeders are predisposed to high feed intake; however, feeding broiler breeders ad libitum impairs their health and reproductive performance. Broiler breeders are feed-restricted throughout rearing to maintain health and performance, yet feed restriction results in hunger, feeding frustration and lack of satiety. The objective of this study was to examine the effect of alternative feeding strategies, including feed additives (separately or combined) and a fixed non-daily feeding schedule, on the feeding motivation and welfare of broiler breeders during rearing. At 3 weeks of age, 180 Ross 308 breeder pullets were allocated to 90 cages and fed with one of five isocaloric treatments: (1) daily control diet (control), (2) daily calcium propionate diet (CaP), (3) daily soybean hull diet (SBH), (4) daily alternative diet (alternative: CaP + SBH) and (5) 4/3 control diet (four on-feed days and three non-consecutive off-feed days per week). The CaP diet included calcium propionate at 1.4% from 3 to 6 weeks of age, and at 3.2% from 7 to 12 weeks of age, and the SBH diet contained soybean hulls included at 40%. The alternative diet included both soybean hulls and calcium propionate at the same inclusion rate as the SBH and CaP diets, respectively. Pullets were weighed and scored for feather coverage every week. A feed intake test was conducted at 3, 4, 8, 10 and 11 weeks of age for 10 min during on- and off-feed days. At 12 weeks of age, feather samples were analysed for fault bars. Data were analysed using linear mixed regression models, with cage nested in the models and age as a repeated measure. At 4 weeks of age, pullets fed soybean hull-enriched diets (SBH and alternative diets) and those on the 4/3 schedule had lower feed intake than control pullets (P = 0.02). Feathers from pullets fed the SBH diet had fewer fault bars than those fed the CaP diet (P = 0.04). The results indicated that the inclusion of soybean hulls (alone or combined with calcium propionate) and a 4/3 feeding schedule can reduce feeding motivation of broiler breeders during early rearing.

The prevalence of feline obesity is influenced by numerous factors, including inactivity and overconsumption of food. The objective of the present study was to evaluate the effect of feeding frequency on physical activity in adult cats. A total of twelve healthy adult cats were used in a cross-over study consisting of 32 d. In each of the two periods, six cats were fed either two meals or four meals daily. Throughout the study, cats were fed the same diet at amounts to maintain body weight and body condition score. Cats were individually housed 4 h/d at each scheduled feeding time, while for the other 20 h, cats were group-housed to allow for voluntary physical activity in the room with a 16 h light–8 h dark cycle. Voluntary activity levels were evaluated using Actical activity collars for seven consecutive days in each period. Daily average activity level for two-meal-fed cats (20·04 (sem 2·19), activity counts/epoch (15 s)) was not different from four-meal-fed cats (20·14 (sem 2·15), activity counts/epoch (15 s); P>0·05). In conclusion, when group-housed cats are fed to maintain their body weight and body condition score, varied feeding frequency between twice and four times daily may not affect activity levels.

Recent work shows that increased meal frequency reduces ghrelin responses in sheep. Human research suggests there is an interaction between insulin and ghrelin. The effect of meal frequency on this interaction is unknown. Therefore, we investigated the effect of feeding frequency on insulin and ghrelin responses in human subjects. Five healthy male volunteers were recruited from the general population: age 24 (sem 2) years, body mass 75·7 (sem 3·2) kg and BMI 23·8 (sem 0·8) kg/m2. Volunteers underwent three 8-h feeding regimens: fasting (FAST); low-frequency (two) meal ingestion (LOFREQMEAL); high-frequency (twelve) meal ingestion (HIFREQMEAL). Meals were equi-energetic within trials, consisting of 64 % carbohydrate, 23 % fat and 13 % protein. Total energy intake was equal between feeding trials. Total area under the curve for serum insulin and plasma ghrelin responses did not differ between trials (P>0·05), although the hormonal response patterns to the two meal feeding regimens were different. An inverse relationship was found between serum insulin and plasma ghrelin during the FAST and LOFREQMEAL trials (P < 0·05); and, in the postprandial period, there was a time delay between insulin responses and successive ghrelin responses. This relationship was not observed during the HIFREQMEAL trial (P>0·05). This study provides further evidence that the postprandial fall in ghrelin might be due, at least partially, to the rise in insulin and that high-frequency feeding may disrupt this relationship.

The diet of breeding white-chinned petrels was studied during the summers of 1996 and 1998 at South Georgia. Krill abundance/availability was high throughout 1996 but apparently low at the beginning of the 1998 breeding season. The diet of white-chinned petrels was similar between years and consistent with previous studies. Krill Euphausia superba (41–42% by weight) was the single most important prey item followed by fish (39–29%) and squid (19–25%). Meal mass was consistent (110 g in 1996, 119 g in 1998) between years but a significant decrease (46%) in feeding frequency in 1998 (0.54 meals day−1 compared to 0.75 meals day−1 in 1996) resulted in 19% less food delivered to chicks in 1998 than in 1996. Breeding success, however, was consistent between years at 44% and similar to that recorded previously at Bird Island. This is in contrast to black-browed and grey-headed albatrosses, both of which experienced almost total breeding failure in 1998. It is suggested that their varied and versatile feeding methods, together with their greater diving ability, capacity to feed at night and extensive foraging range, help white-chinned petrels minimise the effects of krill shortage.

The data used in these analyses were compiled from individual feeding records of 1832 pigs from 70 sire families using FIRE (food intake recording equipment) system from Hunday Electronics Ltd at the Cotswold Pig Development Company. Pigs were on test between 45 (s.d. 2·76) kg and 95 (s.d. 6·78) kg. Daily food intake (DFI kg), food intake per visit (FlV kg), number of visits per day (NV), duration of each visit (TV min), time in the feeder per day (TD min), feeding rate (FR kg/min) and number of non-feeding visits per day (NFV), were measured as means of test and DFI was also recorded as means of bi-weekly periods of test. Performance test traits ofbackfat depth off test (BF mm), food conversion ratio (ECR kg/kg) and average daily gain (ADG kg), over the test period, were also measured.

Parameters were estimated by restricted maximum likelihood with a multivariate individual animal model. DFI had a heritability of 0·21 ranging from 0·18 to 0·26 over the four test periods. Correlations between DFI in each test period were high (rg = 0·75 to 0·99). DFI was highly correlated with performance test traits (0·61 to 0·78) but had low correlations with feeding pattern traits (0·0 to 0·24). The heritabilities of feeding pattern traits were low (0·06 to 0·11) with the exception of FIV (0·27) and NV (0·34) but correlations between feeding pattern traits were high. FIV, NV and TV were moderately correlated with ADG (rg = 0·49, -0·29, 0·33 respectively), BF (rg = 0·35, -0·15, 0·17 respectively) and ECR (rg = -0·12, 0·31, -0·27 respectively). Feeding patterns may be changed substantially by selection and the genetic correlations with performance test traits indicate that feeding patterns traits can be usefully incorporated in selection criteria to improve somewhat the accuracy of selection.

The potential of the spot urine sampling technique as an alternative to performing a total urine collection was evaluated. Twelve multiparous Holstein-Friesian cows were given two experimental diets in a complete change-over design using two 14-day experimental periods. Experimental diets were either silage offered ad libitum with 7 kg fresh weight concentrate supplement as a single meal (SF), or a complete diet formulated from the same ingredients with a similar foragexoncentrate ratio (CD). Total urine collections were performed every 2 h on days 11 and 14 of each experimental period. Subsamples of urine were stored at 20°C and subsequently analysed by high-performace liquid chromatography. Daily allantoin and purine derivative (PD) excretion were highly correlated (r = 0·995, no. = 48, P < 0·001). PD and creatinine excretion during each 2-h interval depended on time of collection (PD, P < 0·001 and creatinine, P < 0·05) and on cow (P < 0·01) but were unaffected by sampling day or treatment. Diurnal variations in the molar ratio ofPD or allantoin to creatinine (PD/c and Ale, respectively) followed similar diurnal patterns as observed for PD and allantoin excretion. The data were used to assess the error of prediction of daily mean PD/c or Ale ratios. Three spot sampling regimens (based on the collection of four 4-h samples, three 8-h samples or two 12-h samples) and also on either single or 2-day urine collections were evaluated. Collection of multiple samples within a day was more reliable than collecting fewer samples over several days. Prediction errors were greater for SF compared with CD. Even the most intensive sampling regimen did not allow an acceptable prediction of daily mean PDIc or Ale ratio, minimum r values for PDIc and Ale ratios were 0·098, 0·136 and 0·547, 0·579 for SF and CD, respectively. Furthermore, daily mean PDIc and Ale ratios proved poor predictors of daily PD and allantoin excretion (r values of 0·69 and 0·72, respectively). Total urine collection appears necessary to assess accurately daily PD excretion in dairy cows.

An experiment was conducted to examine the effect of method and level of concentrate feeding on milk production characteristics in dairy cows offered a grass silage-based diet. Twelve treatments were used with 24 Holstein/Friesian dairy cows in a four-period change-over design experiment. Treatments consisted of three methods of concentrate feeding (twice daily, four times daily or complete diet) and four levels of concentrate feeding (2, 4, 6 or 8 kg/day). Offering a complete diet significantly reduced silage substitution rate (0·28 kg silage dry matter (DM) per kg concentrate DM) compared with concentrates offered twice daily (0·50 kg silage DM per kg concentrate DM; P < 0·01). Method of concentrate feeding had no significant effect on milk yield or milk fat concentration (P > 0·05), although the response in milk protein concentration to increased concentrate food level was significantly greater with twice and four times daily concentrate feeding than with complete diet feeding (0·59, 0·56 and 0·44 g/kg per kg increase in concentrate food level; P < 0·05). Increasing concentrate inclusion level significantly reduced silage DM intake (P < 0·001) but significantly increased (P < 0·001) total DM intake. Milk yield and milk protein concentration were significantly increased (P < 0·001) and milk fat concentration significantly reduced (P < 0·02) with increasing concentrate inclusion level. Total ration apparent digestibility coefficients were unaffected (P > 0·05) by either method of feeding or concentrate inclusion level. However, modified acid-detergent fibre apparent digestibility decreased significantly with increasing concentrate inclusion (P < 0·01). Results suggested that offering complete diets, with concentrates comprising on average 0·33 of total DM intake, increased both silage and total DM intake although this was not reflected in either increased milk yield or improvements in milk composition.

There have been suggestions that positive feedback from the meal may stimulate the performance of undesirable behaviour, such as stereotypies, in the post-feeding period. The aim of this work was to measure the short-term effects of a meal on the post-feeding behaviour of the pig.

Pigs (70 kg live weight) were offered food ad libitum for 7 days and then given a restricted food allowance for 23 days (experiment 1) or 14 days (experiment 2). In experiment 1, the food allowance was given in one, two or three meals per day. In experiment 2, the food allowance was given in two meals per day and comprised ingredients which supplied glucose at different rates (starch, glucose/starch, starch/guar gum). The pigs' posture and behaviour were recorded in three 1-h periods during the day on 2 days consecutively during the ad libitum feeding period (time period 1) and on pairs of days on three (periods 2, 3 and 4: experiment 1) or two (periods 2 and 3: experiment 2) subsequent occasions during food restriction. The meal frequency or estimated rate of glucose supply had no significant effects on posture or behaviour. In both experiments activity increased with the duration of food restriction. In periods 1, 2, 3 and 4 of experiment 1 the proportions of observations spent were: standing 0·244, 0·260, 0·706 and 0·728 (s.e.d. 0·0346); nosing 0·073, 0·094, 0·229 and 0·253 (s.e.d. 0·0169); rooting 0·032, 0·037, 0·108 and 0·133 (s.e.d. 0·0133). In periods 1, 2 and 3 of experiment 2 the proportions were: standing 0·247, 0·302 and 0·446 (s.e.d. 0·0240); nosing 0·045, 0·075 and 0·138 (s.e.d. 0·0113); chewing 0·101, 0·126, 0·155 (s.e.d. 0·0121). In experiment 1 feeding rate increased with duration of restriction (P < 0·001), but was unaffected by treatment. It is concluded that post-feeding behaviour was influenced more by long-term changes in state (i.e. prolonged food restriction) than by short-term effects of the meal.

Eiues on grass silage-based diets were offered, during the last 6 weeks of pregnancy, an increasing allowance of a barley-soya-fish meal concentrate (400 g/day in weeks 15/16; 600 g/day in weeks 17/18; 800 g/day in weeks 19/20) as either one, two or three feeds daily or as a complete mix with silage. Silage dry-matter intake increased with concentrate feeding frequency (P < 0·01) and was greatest with the mixed diet at an average of 1·38 of that with a single daily concentrate meal. The effect on silage intake was evident even at the lowest level of concentrate supplementation during weeks 15/16 and was independent of silage quality. Ewes gained more live weight (P < 0·01), and maintained a higher live weight post partum, as a result of increasing the frequency of feeding of concentrates but mean lamb birth weight was unaffected. Maternal serum metabolites were measured in weeks 17/18 and 19/20 only. Mean [i-hydroxybutyrate was higher, but not significantly so, in weeks 19/20 despite the increased concentrate allowance and was higher overall (P < 0·05) in ewes offered concentrates once daily compared with those receiving concentrates three times daily or mixed with the silage. Insulin-like growth factor 1 (IGF-1) was higher in serum of ewes given frequent concentrate meals compared with those offered concentrate once daily (P < 0·05). Serum albumin and globulin increased as concentrate intake increased between weeks 17/18 and 19/20 (P < 0·05) and also, when concentrates were offered more than once daily (P < 0·05). Serum urea level was higher with more frequent concentrate meals (P < 0·01) and was affected by silage quality (P < 0·001).

Broiler chickens were fed on a control diet based on maize or a diet containing sugar-beet-pulp fibre (Beeffiber) at an inclusion level of 46 g/kg. Diets were provided ad lib. or at a restricted level either once daily or three times daily. On days 13 and 20, chickens fed on the ad lib. control and sugar-beet-pulp-containing diets generally weighed more and had poorer feed conversion ratios than chickens given the restricted control and sugar-beet-pulp-containing diets respectively. Furthermore, chickens given the restricted diets once daily had greater body weights and generally improved feed conversion efficiencies compared with chickens given the restricted diets three times daily. Generally, elevated plasma Lipid concentrations were observed amongst chickens given the restricted diets once daily compared with chickens fed ad lib. as well as the restricted diets three times daily, while chickens fed on restricted diets three times daily had plasma lipid concentrations intermediate between those fed ad lib. and once daily. In a plasma triacylglycerol response study on day 22, feeding of sugar-beet-pulp-containing diets generally reduced postprandial triacylglycerol concentrations and delayed triacylglycerol response relative to chickens given the control diets either ad lib. or restricted, which may indicate gastrointestinal adaptation to feeding of a fibre-rich diet. Postprandial triacylglycerol concentrations observed for chickens receiving restricted diets were increased compared with chickens given the respective ad lib. diets, indicating adaptation of chickens to reduced feed frequency. On day 25, feeding of sugar-beet-pulp-containing diets decreased digesta dry matter content and ileal organic matter digestibility. Chickens given sugar-beet-pulp-containing diets generally had, on day 25, increased caecal short-chain fatty acid (SCFA) concentrations in comparison with chickens given the ad lib. control diet, indicating increased fermentation of dietary components. It is also noteworthy that the greatest SCFA concentrations were observed amongst chickens given the control diet once daily, suggesting enhanced caecal fermentation capacity. This may have been a consequence of increased bacterial activity and caecal hypertrophy due to infrequent feeding of a low-fibre diet.

The effects of acetone concentration in milk, feeding frequency, and intake of concentrates and energy in total diet on milk yield were studied in 38624 lactations from 474 herds during 3 years. Herd-related data on feeding factors were collected once per indoor feeding period. Milk acetone concentrations higher than 0·40 mmol/l were deemed to denote hyperketonaemia, whether subclinical or clinical. The lactation curves of ketotic cows had an abnormal shape, with an inverted peak in early lactation. Most of the reduction in milk yield took place during the first 100 days of lactation with an estimated loss of proportionately 0·085 (acetone concentration ≤0·40 v. >2·00 mmol/l). The loss in 200-day milk yield was estimated to 328 kg 40 g/kg fat-corrected milk (FCM) at an overall mean of 5056 kg. If a herd's performance is monitored by lactation curves, a low peak — and hence an apparently high persistency – can indicate a ketosis problem. More frequent feeding of concentrates was correlated with a proportionately 0·033 to 0·074 higher milk yield in multiparous cows, but inconsistent between years. A more variable proportional response (−0·035 to 0·131) was observed in primiparous cows depending on interactions with, for example, breed. A greater total energy supply, including a larger amount of concentrate (maximum in lactation), was correlated with a higher milk yield, about 0·06 kg FCM per day per MJ metabolizable energy and 0·5 kg FCM per day per kg concentrate, respectively. However, increased feeding of concentrates at calving (parity 1) and 15 days after calving (multiparous cows) was correlated with decreased milk yield, by about −0–3 and −0–5 kg FCM per day per kg concentrate, respectively.

The diurnal changes in plasma concentration and urinary excretion of purine derivatives (PD) were examined in four steers given their food in either one or two meals daily in two 18-day periods. In period 1, two steers were fed once daily (at 08.00 h) and the other two twice daily (at 08.00 and 16.00 h). In period 2, the treatments were switched. In the last 4 days of each period, plasma samples were taken from 08.00 to 24.00 h at 2 to 3 h intervals, and daily urine was collected in several 4 to 8h periods. With once daily feeding, allantoin concentration in plasma varied from 090 to 1·07 of the daily mean and with twice daily feeding, from 0·97 to 1·05 of mean. The coefficient of variation (CV) for total variation was 0·14. In urine, the concentration and hourly excretion of PD varied with sampling times (P < 0·05) but the ratio of PD to creatinine was relatively constant even for once-daily feeding (CV, 0·02 for measurements at different times). The CV for total variation in the ratio was 0·19. The results suggest that diurnal variation in plasma allantoin concentration and in the ratio of allantoin (or total PD) to creatinine are relatively small even for once daily feeding. It thus seems that these measurements in spot samples may be suitable for use as a simple index of microbial protein supply if they are correlated with the daily PD excretion. The results also indicate that measurements in samples of plasma and urine taken between 15.00 and 20.00 h tended to give a better representation of the daily mean.

The influence of the method of conserving grass herbage and the frequency of feeding on eating behaviour, rumen motility and rumen fill was studied in growing steers. Silage and hay were offered to twelve rumen-cannulated Friesian steers (average initial live weight (LW) 128 kg) at a restricted level of intake (20 g dry matter (DM)/kg LW) either once or eight times daily. With once daily feeding, the daily intake of hay was consumed in a single large meal which lasted about 2 h, while silage was eaten in many small meals throughout the day. The proportion of the day spent ruminating was higher (0·39) for steers offered hay once daily than for those offered silage (0·28) or hay eight times per day (0·29). There was little effect of conservation method on frequency of rumen contraction, but contractile intensity (integration of frequency and amplitude) increased during the second half of the 24 h feeding cycle in steers offered hay either once daily or eight times daily, while the same effect was only observed when silage was offered once daily. Total daily contractile activity (the integration of the frequency and duration of myoelectric spike bursts) was significantly (P < 0·05) higher in steers offered hay, compared with silage, once daily. The mean weight of organic matter in the reticulo-rumen of steers offered hay was significantly higher than for silage both with once (1593 v. 1326 g organic matter (OM)/100 kg LW, P < 0·01) and eight (1367 v. 1160 g OM/100 kg LW, P < 0·05) times daily feeding. The proportion of the particulate pool which was present as small (< 1·2 mm) particles was always greater than 0·60.

The effect of method of conserving grass herbage and the frequency of feeding on digestion in and passage from the rumen was studied in growing cattle. A single sward of perennial ryegrass (Lolium perenne cv. Endura) was cut on 1 d and conserved as silage or hay. These forages were offered as the only feed to twelve rumen-cannulated Friesian steers (average initial live weight (LW) 128 kg) either at a restricted level of intake (20 g dry matter (DM)/kg LW; Expt 1) or ad lib. (Expt 2). In Expt 1 the forages were offered either once or eight times daily. When fed once or eight times daily, in vivo digestibility of DM was very similar for hay and silage (0.771 and 0.783 respectively), while the fractional rate of digestion measured by incubation in Dacron bags was significantly (P < 0.05) higher for silage (0.069) than hay (0.057). The rate of passage of mordanted feed out of the rumen was significantly (P < 0.01) faster for silage when determined from concentrations of marker in the rumen (0.034 v. 0.028 /h). The volume of liquid in the rumen was lower (P < 0.01) for animals consuming silage (27.51) compared with hay (37.11), while the fractional rate of passage of liquid from the rumen was higher (0.141 v. 0.098 /h, P < 0.05). The volume of liquid in the rumen was also lower (P < 0.05) in steers offered feed eight times daily (29.51), compared with once daily (35.11), but frequency of feeding had no significant effect either on total digestibility or on rate of digestion in the rumen. The ad lib. intake of silage was significantly (P < 0.01) lower than that of hay (4.53 v. 5.16 kg DM/d) in Expt 2.

L'influence de la période (jour, nuit) et de la fréquence d'alimentation (1 à 4 repas fractionnés ou alimentation continue) a été étudiée sur la croissance et l'efficacité alimentaire chez un silure africain (Heterobranchus longifilis). L'expérience, d'une durée de 56 jours, a été réalisée sur des poissons de 74 g de poids moyen initial. Avec un même taux de rationnement (3 % du poids vif/jour), les poissons nourris la nuit ont une croissance significativement plus élevée que ceux nourris le jour et un nourrissage sur l'ensemble du nycthémère n'apporte pas d'amélioration. Les performances de croissance tendent à augmenter avec l'accroissement de la fréquence d'alimentation quelle que soit la période de nourrissage, et les croissances sont significativement plus élevées avec une alimentation en continu, de 2,36 à 2,64 g.j-1. L'indice de consommation est significativement plus faible pour les poissons nourris en continu que pour ceux recevant une alimentation par repas. Le rapport hépatosomatique est significativement plus élevé chez les poissons nourris la nuit que pour ceux nourris le jour. Par contre, les dépôts de graisse dans la cavité abdominale sont plus importants chez les individus nourris de jour et augmentent avec la fréquence des repas. L'analyse des compositions corporelles globales confirme ces observations. En pratique, il est recommandé de nourrir ce poisson en continu durant la nuit, ce mode d'alimentation conduisant aux meilleures performances de croissance.

Total and unilateral parotid saliva production during eating were measured in response to offering sheep a fixed amount of lucerne (Medicago sativa) hay as one, two, four or eight meals. Total saliva measurements were obtained using sham-fed oesophageal-fistulated sheep. Unilateral parotid saliva was collected from sheep fitted with reversible re-entrant cannulas. Dry matter intakes and eating times were measured for each meal but were not constrained to particular values. Total and unilateral parotid saliva production during eating increased linearly with the log of the number of meals (p = 0.0001). The amounts corresponding to one, two, four and eight meals of lucerne hay were 1553, 1737, 1851 and 2087 ml during total collections and 209, 248, 307 and 352 ml during unilateral parotid collections. The time-period spent eating and the amount of food consumed both increased as meal number increased. Total saliva collections when lucerne hay was sham-fed as one, two, four or eight meals were associated with eating times of 56.9, 57.4, 70.8 and 86.0 min and intakes of 562, 622, 629 and 638 g dry matter respectively. For unilateral parotid collections, eating times and dry matter intakes were 64.2, 71.3, 78.0, 82.1 min and 515, 579, 614 and 627 g for one, two, four and eight meals of lucerne hay respectively. The saliva production response appeared to be determined through the effects of the time-period spent eating and amounts consumed, but other undetermined effects of feeding frequency contributed to the response. The importance of meal duration on total saliva production was assessed by sham-feeding of 800 g lucerne as stem, leaf, hay, chopped hay or ground and pelleted hay. Increasing meal duration by feeding with stems resulted in the production of 1808 ml saliva, whereas the rapid consumption of pellets resulted in only 442 ml being produced.

The effect of frequency of feeding (once daily or six equal portions at intervals of 3 h) of diets containing lysine (6.4 g/kg) supplied as either protein-bound or free lysine on the metabolism of essential amino acids was investigated in pigs over the 23–34 kg weight range. The amounts of radioactivity from 14CO2 produced by the pigs given oral doses of [14C]lysine or [14C]phenylalanine were determined. [14C]Lysine was confirmed to be unsuitable presumably because the oral dose was diluted by the dietary free lysine or was absorbed ahead of the protein-bound lysine, or both. With [14C]phenylalanine addition, there was a significantly (P < 0.01) greater production of 14CO2 by pigs fed once daily on the diet containing free lysine. However, with frequent feeding, there was no significant difference (P > 0.05) in the amount of 14CO2 produced by pigs from [14C]phenylalanine for either diet. Growth responses of the pigs were lower when the diet containing free lysine was given once daily (P < 0.01) but were similar when the diets were given frequently. It is concluded that the more rapid absorption of free lysine by growing pigs fed once daily results in an imbalance of amino acids at the sites of metabolism. This leads to greater oxidation of essential amino acids than occurs when all the amino acids are supplied in the protein-bound form. With frequent feeding, a better balanced supply of amino acids is absorbed, leading to similar rates of oxidation of excess essential amino acids from diets containing either free or protein-bound lysine.