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The effect of Lys restriction followed by a repletion period on the performance of growing pigs was studied during 3 feeding phases, each lasting 28 d. A total of 47 castrated male pigs (G Performer 8.0 × Fertilis 25 pigs; Genetiporc Inc., Saint-Bernard, QC, Canada; initial BW of 26.7 ± 2.7 kg) were given each d 70% or 100% of their Lys requirements according to 1 of the following 5 sequences: 70-70-70, 70-70-100, 70-100-70, 70-100-100, or 100-100-100 (for each sequence, numbers indicate the Lys supply percentage in phase 1, 2, and 3, respectively). Individual Lys requirements were estimated daily on the basis of each pig's actual BW and feed intake and BW gain patterns obtained by regression using each pig's historical data. At the end of phase 1, the pigs given 100% of their Lys requirements had higher ADFI ( = 0.01), ADG (0.01), and average daily protein deposition (0.01) than did the pigs given 70% of their requirements. Similar results were observed during phases 2 and 3. At the end of phase 2, the pigs in the 70-100 sequence did not display any compensatory response, given that their ADFI, ADG, and average daily protein deposition did not differ from those of the pigs in the 100-100 sequence. Similar results were observed during phase 3. Although no compensatory growth was observed during the growing phases, the fact that the pigs in the 70-100-100 treatment were able to catch up in terms of BW and body protein mass to the pigs in the 100-100-100 sequence could indicate that a small degree of compensation did occur; these research results cannot ascertain that any compensatory growth occurred.

A novel method is proposed to detect multi-part objects of unknown specific shape and appearance in natural images. It consists in first extracting a strictly over-segmented map of circular arcs and straight-line segments from an edge map. Each obtained constant-curvature contour primitive has an unknown origin which may be the external boundary of an interesting object, the textured or marked region enclosed by that boundary, or the external background region. The following processing steps identify, in a systematic yet efficient way, which groups of ordered contour primitives form a complete boundary of proper multi-part shape. Multiple detections are ranked with the top boundaries best satisfying a combination of global shape grouping criteria. Experimental results confirm the unique potential of the method to identify, in images of variable complexity, actual boundaries of multi-part objects as diverse as an airplane, a stool, a bicycle, a fish, and a toy truck.

Plasma concentrations of hormones and metabolites were measured in growing steers to establish their relation with degree of feed restriction. Sixty medium frame beef steers (259 ± 29 kg) were divided in groups of five and fed during 3 mo either timothy (T) or bromegrass (B) harvested at stem elongation of the first cut or at boot stage of the aftermath. Forages were fed at one of three levels of intake: ad libitum (FF), 80% of FF, or 65% of FF. Plasma concentrations of growth hormone (GH), insulin, glucagon, insulin-like growth factor-1 (IGF-1), glucose and nonesterfied fatty acids (NEFA) were measured on day 1 and day 78 before the morning meal. The effect of a meal on GH, insulin, glucagon, IGF-1, glucose and NEFA concentrations was also determined in 24 steers sampled from 3 h before to 3 h after a meal. Severity of feed restriction resulted in a linear decrease (P < 0.05) of plasma glucagon (0.139, 0.130, 0.121 ± 0.005 ng mL–1) and IGF-1 (109, 98, 84 ± 7 ng mL–1). Insulin concentration tended to be affected quadratically (0.37, 0.35, 0.27 ± 0.04ng mL–1 for FF, 80% of FF and 65% of FF, respectively, P < 0.10). Ingestion of a meal resulted in a decrease (P < 0.05) of GH, NEFA and glucose, and an increase of insulin concentrations (P < 0.05). There was a positive correlation (r = 0.53, P < 0.05) between IGF-1 and average daily gain, and lipid percentage of carcasses suggesting that IGF-1 is related to growth rate and fat accumulation in growing steers. Key words: Feed restriction, growth hormone, insulin, IGF-I, metabolites, grass silage

The feeding behaviour of eight Pietrain boars (PP/M), eight Large White boars (LW/M) and nine barrows (LW/C), and six Meishan barrows (MS/C) was studied at three different stages of growth (S1, S2, S3) corresponding to average body weights (BW) of 23, 39 and 57 kg, respectively. The PP, LW and MS breeds were considered as lean, conventional and fat types of pigs, respectively. All animals were reared individually. The light pattern was 12 hours of artificial light. The type of pig significantly affected the daily voluntary feed intake (1659, 1746, 1970 and 1622 g/d in PP/M, LW/M, LW/C and MS/C, respectively). Daily number of meals was higher in PP/M (14.4) than in LW/M and LW/C (12.2 on average) and in MS/C (7.3) whereas meal size was lower in PP/M (125 g vs. 166 g in LW pigs and 250 g in MS/C). Feed intake increased linearly with BW; the increase was lower in PP/M and MS/C (+15 g per kg of BW gain) than in LW/M (+26 g per kg) and in LW/C (+35 g per kg). With increasing age, number of meals per day decreased. Simultaneously, their size increased but the increase was more important in MS/C than in other types of pigs. The pattern of feed intake was mainly diurnal and more pronounced with the increase of BW (57 and 66% of feed intake during the day at S1 and S3, respectively). The results obtained in the present experiment clearly indicate that differences observed in composition of BW gain between types of pigs are associated with differences in VFI but also with differences in feeding behaviour.

One week after weaning, 16 animals were immunized (IMM) against human-globulin (hG-IMM) and 16 against SRIF conjugated to hG (SRIF-IMM) in Freund's complete adjuvant. Subsequent boosters in Freund's incomplete adjuvant were made on days 14, 28, 56 and 73 of the experimental period. On day 79, half of the animals within each immunization treatment were infused continuously with human GRF(1-29)NH2 (3.33 ng min-1 kg-1 BW) and the other half with saline over a 32-day period. GRF increased (P=0.01) body weight gain by 12%, whereas SRIF immunization decreased (P=0.01) weight gain by 7.5% during the infusion period (days 79-111). However, the effect of SRIF immunization on growth rate was not significant (P>0.10) when considered over the entire duration of the experiment (days 0-111). Feed intake, feed efficiency, carcass characteristics, nutrient digestibility, nitrogen retention and metabolizability of energy were not affected (P>0.10) by SRIF immunization or GRF infusion. However, GRF infusion increased pancr...

In a first trial, release of growth hormone (GH) to various doses of human growth hormone-releasing factor (1-29)NH2 (GRF) infusion (0, 1.11, 3.33 and 10 0 ng min-1 kg-1

Metabolizable energy (ME), net energy for maintenance and net energy for growth of grass silages were evaluated by the comparative slaughter technique using a 2 × 2 × 3 factorial design. Sixty medium frame beef steers (259 ± 29 kg BW) were divided in groups of five and fed during 3 months either Timothy (T) or Bromegrass (B) harvested at stem elongation (S) of the first cut or at boot stage of the aftermath (A). Forages were fed at one of three levels of intake: ad libitum (FF), 80% of FF, or 65% of FF. Silages averaged 26.9% DM, 16.0% CP and 37.7% ADF. Regression of logarithm of heat production (HE) against ME intake were similar for all silages (log HE = 0.00046*ME + 2.4923; r2 = 0.89). From this equation, fasting HE of 311 kJ kg−0.75 d−1, ME for maintenance of 559 kJ kg−0.75 d−1 and efficiency of utilization of energy for maintenance of 56% were determined. Regression of ME intake against retained energy (RE) were similar for all silages. Efficiency of ME utilization for growth was 33% using the regression of ME over RE with a ME requirement for maintenance fixed at 559 kJ kg−0.75 d−1. Net energy for maintenance and growth were similar for all silages, averaging 6.17 and 3.70 MJ kg−1, respectively. The use of a prediction equation based on ADF of forages underestimated ME values of silages by approximately 25%. Moreover, NRC (1984) equations that estimate NE from experimentally estimated ME values tended to overestimate the net energy of our grass silages. Key words: Net energy, grass silages, timothy, bromegrass, beef cattle

Leucine irreversible loss (ILR) and fractional leucine oxidation (FO) were estimated using primed infusions of L-[1-13C]leucine and [13C]bicarbonate. Feed restriction decreased (P < 0.05) ILR from 16.42 to 10.82 mmol h−1, but did not affect FO (0.172) in two young dairy heifers. In six growing steers, ILR and FO averaged 30.03 ± 5.09 mmol h−1 and 0.147 ± 0.027, respectively. L-[1-13C]leucine and [13C]bicarbonate can be successfully used to measure the different components of protein metabolism in cattle. Key words: Stable isotope, protein metabolism, leucine, bicarbonate, cattle

Eight mature wethers fitted with rumen cannulae were used in a double 4 × 4 Latin square feeding trial to study the effect of dietary alkalis on digestive physiology of sheep fed a high-barley diet. The treatments were: C = control diet composed of 17% alfalfa meal and 83% concentrate, on as-fed basis; CA = control plus 1% Ca(OH)2; MG = control plus 0.79% Mg(OH)2; CAMG = control plus 0.5% Ca(OH)2 and 0.39% Mg(OH)2. Dry matter intake averaged 1.91, 2.54, 2.79, and 2.72% of BW for diets C, CA, MG and CAMG, respectively (P −1 for C, CA, MG, and CAMG diets, respectively (P 3-N concentration was lower in sheep fed the hydroxide-containing diets than in animals fed the control diet (P 3− and base excess (P 2 and Mg(OH)2 to the diet, alone or in combination, improved the systemic acid-base status of sheep and was associated with increased DM intake. Key words: Hydroxides, acid-base balance, rumen fermentation, sheep

Nine DLS rumen-cannulated wethers (69 kg avg BW) were used to study the effects of dietary supplementation with two types of fermented, ammoniated, condensed whey permeate on performance, rumen physiology and acid-base status in sheep fed high-grain diets. Sheep were fed three isonitrogenous (16% CP) diets according to a triple 3 × 3 Latin square design, with three 21-d periods each. One whey permeate contained ammonium lactate (AL) while the other contained ammonium propionate (AP). Urea was used as a source of NPN in the control diet (C). Diets, offered ad libitum, contained 78% barley and 18% dehydrated alfalfa meal. Dry matter and digestible energy intakes were about 15% higher for diets AL and AP than for diet C (P

Twenty-four castrated lambs (32.4 ± 4.1 kg BW) were used to study the effect of varying dietary cation–anion concentration [C–A] on performance and acid–base balance. The diets contained approximately 100, 300, 500 and 700 mequiv Na + K − Cl kg−1 of feed. Each group of six lambs was fed one of the diets ad libitum during a 6-wk test. Increasing the [C–A] of the diets resulted in higher feed intake and higher daily gains (P −1 stimulated growth by allowing greater feed intake and greater daily gains with little effect on nutrient digestibility. Blood profile showed a systemic response to dietary changes in [C–A], but indicated that lambs were able to adapt to cation loads since the values obtained for acid–base balance were within physiological range for lambs. Key words: Cation–anion, acid–base, lambs

Environmental effects of excess P from manure and the soaring price of phosphates are major issues in pig production. To optimize P utilization, it is crucial to improve our capacity to predict the amount of P absorbed, while taking into account the main factors of variation. Mathematical modeling can represent the complexity of the processes and interactions in determining the digestive utilization of P in growing pigs. This paper describes and evaluates a model developed to simulate the fate of the dietary forms of P in the digestive tract of growing pigs, with particular emphasis on the effect of dietary Ca and exogenous phytase on P digestive utilization. The model consists of 3 compartments associated with specific anatomical sections: stomach, proximal small intestine, and distal small intestine. The main metabolic processes occurring in these sections are, respectively, P solubilization/insolubilization and phytate P hydrolysis, and P absorption and P insolubilization. Model parameters governing these flows were derived from in vitro and in vivo literature data. The sensitivity analysis revealed that the model was stable within a large range of model parameter values (±1.5 SD). The model was able to predict the efficacy of Aspergillus niger microbial phytase in accordance with literature values, as well as the decreased efficacy of plant phytase compared with microbial phytase. The prediction capabilities of the model were assessed by comparing actual and simulated P and Ca apparent total-tract digestibility (ATTD) based on published pig data not used for model development. Prediction of P digestibility across 66 experiments and 281 observations was adequate [P ATTD observed = 0.24 (SE, 0.943) + 0.98 (SE, 0.0196) × P ATTD predicted; R(2), 0.90; disturbance error (ED), 96.5%], whereas prediction of Ca digestibility across 47 experiments and 193 observations was less accurate (Ca ATTD observed = 11.1 + 0.75 × Ca ATTD predicted; R(2), 0.78; ED, 20.4%). A lack of agreement between experimental and simulated Ca digestibility was found. This model is, therefore, useful in evaluating P digestibility for different feedstuffs and feeding strategies. It can also be used to provide insight for improving dietary P utilization, especially from plant sources, by quantifying the effect of the mean sources of variation affecting P utilization.

The present study was conducted to assess the effect of 2 dietary Ca concentrations on P and Ca digestive and metabolic utilization in weanling pigs fed diets providing practical concentrations of P, with or without phytase. The responses of pigs fed diets adequate or moderately deficient in Ca and P postweaning were compared. A total of 60 pigs weaned at 28 d of age were used. Two groups of 30 pigs with differing mineral status resulted from a 10-d depletion period, during which the animals received depletion diets (DD) that consisted of corn-soybean meal with either 1.42% Ca and 0.80% P (DD+) or 0.67% Ca and 0.43% P (DD-), designed to achieve the same Ca:digestible P ratio. At the end of the depletion period, a plasma sample was taken from each pig and 12 pigs (6 from each group) were slaughtered for bone assessment to establish the baseline mineral status. The animals fed the DD- diet had signs of P deficiency with reduced plasma P (13%; P0.01) and femur ash concentration (8%; P0.05), and increased plasma Ca (9%; P0.05) and alkaline phosphatase activity (31%; P0.01). For the subsequent 25-d period, the remaining 24 pigs from each group were fed 1 of 4 repletion diets: 1) 0.56% P, 1.06% Ca; 2) 0.56% P, 0.67% Ca; 3) diet 1 + 1,000 phytase units (FTU) of Natuphos phytase/kg; and 4) diet 2 + 1,000 FTU of Natuphos phytase/kg. Total feces and urine were collected from d 5 to 11, and a blood sample was taken from each pig at d 11 and 25. The initial moderate P deficiency (DD-) stimulated Ca absorption (5%; P0.01), irrespective of the repletion diet, and stimulated P absorption (5%; DD x phytase, P0.05), only when the diets contained phytase. At the end of the repletion period, because of these compensatory phenomena, the depleted pigs achieved full recovery of femur DM and ash weight when they received phytase, whereas ash concentration tended to remain reduced by 3% (P = 0.08). Phosphorus digestibility was improved in the diets supplemented with phytase (73.0 vs. 56.0%; P0.001), whereas an increase in dietary Ca decreased P digestibility (65.6 vs. 63.4%; P0.05). Those 2 effects were independent, indicating that dietary Ca reduced equally P digestibility with and without phytase and did not influence the efficiency of phytase in releasing P in the digestive tract. In pigs fed diets with phytase, however, the reduction of Ca (Ca:P from 1.9 to 1.3) increased urinary P losses 5-fold. Those extra losses were due to a lack of Ca for skeleton ash deposition, resulting in a 4% reduction in femur ash concentration. In the end, reducing the dietary Ca:P from 1.9 to 1.3 in a practical diet containing 0.56% P did not improve the efficiency of phytase in releasing P. Moreover, the reduction in dietary Ca (Ca:P) caused an imbalance between Ca and P that impaired bone mineralization.

Two experiments were conducted with 24- to 72-h-old male piglets. In exp. 1, 24 piglets were assigned to three dietary treatments. In the control diet, 100% of the dietary protein originated from low-heat skimmed milk powder. In the other diets, either 25 or 50% of the milk proteins were replaced by oat protein concentrate. In exp. 2, eight piglets were assigned to each of two diets where 100% of the dietary protein originated from skimmed milk powder and 50% of the milk proteins were replaced by oat protein concentrate. In exp. 1, dry matter intake was not affected by treatments while body weight gain declined and feed to gain ratio increased significantly (P 0.05) for both the oat and milk protein treatments. Oat protein concentrate can thus replace up to 50% of milk proteins without apparent detrimental effect on dry matter intake and N digestibility; however, growth rate will be reduced. Key words: Piglets, artificial rearing, milk replacer, skimmed milk powder, oat protein concentrate, digestibility

A method is proposed to detect multi-part man-made or natural objects in complex images. It consists in first extracting simple curves and straight lines from the edge map. Then, a search tree is expanded by selecting and ordering the segmented primitives on the basis of generic local and global grouping criteria. The set of partial contours provided by the parallel search are combined into more complex forms. Global scores produce a sorted list of potential object silhouettes.

In this paper, a top-down approach based on perceptual grouping is proposed for multi-part objects detection. The abstract conceptual category of multi-part objects is formalized by a set of global criteria. These criteria will enable the evaluation of the segmentation quality in order to determine if the whole grouping is perceptually significant and if it has a good perceptual shape. A new cognitive vision methodology, called SAFE (subjectivity and formalism explicitly), is presented. Its goal is to help identify the proper global criteria and to validate the judgment derived from formal calculations of these criteria by human judgment.

The contribution of the total splanchnic tissue (TSP; portal-drained viscera (PDV) plus liver) to whole-body protein metabolism was estimated in relation to intake (0.6, 1.0 and 1.6 x maintenance requirements), in six multicatheterized growing beef steers used in a double 3 x 3 Latin square design. At the end of each 21 d experimental period, [1-13C]leucine was infused into a jugular vein (1.05 mmol/h for 5 h, preceded by a priming dose of 1.05 mmol). Arterial, portal and hepatic blood samples were collected hourly during the infusion. The increment in TSP leucine irreversible loss rate (ILR) observed with increasing intake reached significance (P0.10) only for PDV, while whole-body ILR increased markedly (P0.001) with intake. The relative contribution of TSP to whole-body leucine ILR averaged 44% (25% from PDV and 19% from the liver). Although these proportions were not affected by intake, on an incremental basis more than 70% of the increase of whole-body leucine ILR between the 0.6 and 1.0 x maintenance originated from the changes in TSP ILR, while the corresponding value was below 13% between 1.0 and 1.6 x maintenance. Total whole-body leucine oxidation and fractional oxidation increased (P0.05) with intake. Protein retention increased with intake (P0.01), as a result of a greater increase in protein synthesis compared with protein degradation. Protein breakdown had a major impact on protein turnover as 65% of the protein synthesized was degraded when intake varied from 1.0 to 1.6 x maintenance. Net leucine portal absorption increased (P0.001) with intake and represented 1, 16 and 23% of whole body leucine ILR, for 0.6, 1.0 and 1.6 x maintenance, respectively. Although leucine oxidation was not a major component of whole body ILR (9.3-19.9%), it represented 69% of the net available leucine (portal absorption) even at 1.6 x maintenance. The lower relative contribution of the TSP to whole-body leucine ILR at higher intake indicates the proportional increase in the metabolic activity of peripheral tissues as the animals moved into positive protein balance.

A total of sixty-five observations on heat production during fasting and physical activity were obtained in four groups of pigs differing in breed and/or castration (Meishan (MC) and Large White (LWC) castrates and Large White (LWM) and Piétrain (PM) males) with body weight (BW) ranging between 25 and 60 kg. Pigs were fed ad libitum before fasting. Heat production was measured using indirect calorimetry. Fasting heat production (FHP) was proportional to the body weight raised to the power 0.55, but with group-specific proportionality parameters (810, 1200, 1220 and 1120kJ/kg BW0.55 per d for MC, LWC, LWM and PM respectively). Group effects could be removed by expressing FHP as a function of muscle, viscera and fat: FHP (kJ/d) = 457(muscle)0.81 + 1969(viscera)0.81 - 644(fat)0.81. It is hypothesized that different breeds with equal muscle and visceral mass, can have different FHP. The negative coefficient for fat would then be the result of a low FHP rather than a cause of it. Because a large part of the variation in tissue composition between groups was due to MC group, a separate equation for the lean groups was established. For lean pigs, FHP could be expressed as a function of muscle and viscera alone: FHP (kJ/d) = 508(muscle)0.66 + 2011(viscera)0.66. Both type of pig and BW affected the number of bouts of physical activities (i.e. standing or sitting) per day, the duration of activity and the total cost of activity. Energetic cost of activity was proportional to the muscle mass raised to the power 0.91 (FHPactivity (kJ/h activity) = 21.0(muscle)0.91). Physical activity represented less than 10% of the total heat production in fasting growing pigs housed alone in metabolic cages and kept in a quiet environment.

A model is proposed that allows study of the short-term dynamics of gas exchanges (and heat production) in large open-circuit respiration chambers. The model describes changes in [O2] and [CO2] in the respiration chamber by a series of differential equations based on animal metabolism and physical characteristics of gas exchange. The model structure was similar for O2and CO2, although model parameters differed. A constant level of O2consumption (and CO2production) was assumed for resting animals which was different for fed and fasted animals. The adaptation from a fed to a fasting state was described as a first-order process. Physical activity (standing or sitting) was recorded and was included in the model as a constant. Thermic effect of feed comprised the O2consumption and CO2production related to several relatively rapidly occurring processes after ingestion of a meal (e.g. ingestion, digestion or absorption). In the model, these processes were pooled into a single phenomenon. Model parameters were obtained statistically by comparing model predictions (based on the numerically integrated differential equations) with the observed [O2] and [CO2]. The model was evaluated by studying gas exchanges in growing pigs that were fasted for 31 h and re-fed a single meal thereafter. The model fitted the data well over the 47 h measurement range. Traditional methods in which heat production is calculated suffer from noisy data when the interval between observations becomes too short. The proposed method circumvents this by modelling the observed concentration of gases in the respiration chamber rather than the calculated heat production.

Ninety-six 1-day-old male broilers were fed a diet containing 0, 2, 4, 6, 8, or 10% of a 1:1 mixture of pyruvic acid (PY) and dihydroxyacetone (DH) for ad libitum consumption for 42 days. Feed intake, body weight gain, and feed efficiency decreased linearly (P.001) with increasing levels of PY and DH. There were no significant differences among treatments for abdominal fat percentage. Carcass chemical analysis revealed small but significant (P.05) differences among dietary treatments for protein and fat percentages. In a second experiment, 192 1-day-old male broilers were fed diets containing 5% of PY, lactic acid (LA), citric acid (CI), DH, or glycerol (GY) or mixtures (1:1) of DH or GY in combination with each organic acid. Bird performance was impaired (P.05) by PY or CI but not by DH or GY. Lactic acid reduced (P.05) feed intake by 9% without affecting weight gain. Lactic acid plus DH, CI plus DH, and CI plus GY mixtures decreased (P.05) bird performance but other combinations had no effect. Pyruvic acid or CI decreased abdominal fat and carcass lipid percentages. Dihydroxyacetone increased (P.05) carcass lipid percentage and GY increased (P.05) abdominal fat percentage. Lactic acid plus DH increased (P.05) carcass lipid percentage. Only PY and CI decreased carcass fat deposition, but they also impaired broiler performance.

Thirty-six calves 19–20 wk old (149 ± 17 kg) and forty-eight rams (46 ± 4 kg) were used in two experiments to study the effects of two ground roughages (alfalfa and timothy), their proportion in pelleted rations (20, 40 and 60%) and addition of monensin (0 and 33 ppm) on ration digestibility. Calves and rams were fed the test rations ad libitum for a period of 8 and 5 wk, respectively, before the digestibility trial. Dry matter (DM) digestibility in both species and energy digestibility in calves were significantly higher for the rations containing alfalfa than for those containing timothy; however, digestibility of crude protein (CP) in both animal species and of cell walls (NDF) in calves was lower in alfalfa rations. The two trials revealed an increase in digestibility of acid detergent fiber (ADF) and of cell wall (NDF) fractions but a reduction in DM digestibility when the roughage content in the rations increased; the reduction in DM digestibility was larger with timothy than with alfalfa. Addition of monensin did not affect digestion coefficients of DM, ADF and NDF in calves and rams on average. However, a monensin × roughage level interaction indicated a decrease of ADF and NDF digestibility in calves fed 20% roughage and an increase of ADF and NDF digestibility in calves fed 60% roughage. Key words: Alfalfa, timothy roughage level, monensin, calf, sheep

Eighty-four calves 11–12 wk old (88 ± 10 kg BW) were used in a 47-d trial to study the effects of two ground roughages (alfalfa and timothy), their proportions in pelleted rations (20, 40 and 60%) and addition of monensin (0 and 33 ppm) on animal performance. After the trial, the animals continued to consume the rations until they reached a slaughter weight of 185 kg. Calves fed rations containing timothy showed higher dry matter (DM) and digestible energy (DE) intake and higher average daily gains (ADG) than calves fed rations containing alfalfa, which was partially due to the quality of the protein used to supplement the timothy rations. Proportion of roughage did not affect DM intake with the exception of 60% alfalfa rations which had the lowest intake. Increasing the roughage in the rations reduced DE intake and ADG, and increased feed conversion values (FC), particularly at 40 and 60%. Monensin increased DE intake and FC of rations containing 40 and 60% timothy, but had no effect on DM intake or ADG. Monensin increased DE conversion values when roughages were added at levels of 40 and 60%, the effect being greater with timothy. Dressing percentage of carcasses decreased with increasing levels of roughage in the ration, the lower values being obtained with timothy. Carcass classification and color of the meat were unaffected by the treatments. Key words: Alfalfa, timothy, roughage level, monensin, calf

In the first experiment, two catheters were placed in one of three sites for infusion and sampling (vena cava and vena cava with 7 cm between catheter tips, VC/VC, n = 5; right ventricle and atrium, RV/RA, n = 5; anterior aorta and left ventricle, AA/LV, n = 4) to determine the effect of site on the measurement of CO2 and leucine kinetics. Pigs received a 6-h continuous i.v. infusion of NaH13CO3 (1.45 µmol h−1 kg−1, preceded by a priming dose of 2.05 µmol kg−1) and of L[1-13C]leucine (9.7 µmol h−1 kg−1, preceded by a priming dose of 9.7 µmol kg−1), the following day. No effect (P > 0.10) of site was observed on NaH13CO3 recovery rate, leucine irreversible loss rate (leucine ILR) and leucine used for protein synthesis (LS). A tendency (P 13CO3 and L[1-13C]leucine for three different 6h periods (12:00 to 18:00 h, first day; 20:00 to 02:00 h, night; 12:00 to 18:00 h, second day) to determine the diurnal and day-to-day variation of CO2 and leucine kinetics. No effect (P > 0.10) of period was observed on NaH13CO3 recovery rate, leucine ILR and LS. The LO was lower (P 0.10) LO was observed between the first day and night (diurnal variation). Together, these results indicate that 1) the VC/VC site can be used for L[1-13C]leucine and NaH13CO3 infusions, 2) NaH13CO3 recovery studies can be performed either the day preceding or following the measurement of substrate and 3) protein synthesis estimated from a 6-h infusion period can be extrapolated to the 24 h periods under conditions of frequent feeding. Key words: Pigs, leucine, protein synthesis, tracer techniques, diurnal variation

Eighteen growing barrows (body weight: 26.6 ± 1.4 kg) were assigned (day 0) to one of three levels of dietary lysine: to be deficient (0.45%; L1), to achieve (0.75%; L2), or to exceed (0.98%; L3) National Research Council (NRC) (1988) lysine requirements (as-fed basis), according to a completely randomized block design. Nitrogen balance was measured over a 6-d period (days 10 to 16). On day 16, pigs were moved into respiratory chambers and received a 6-h continuous i.v. infusion of NaH13CO3 (1.66 µmol h−1 kg−1, preceded by a priming dose of 2.35 µmol kg−1) on day 17. The following day, pigs received an i.v. infusion of L-[1-13C]leucine (11.07 µmol h−1 kg−1, preceded by a priming dose of 11.07 µmol kg−1). Average daily gain and nitrogen retention increased (P 0.10) between diets. In consequence, fractional oxidation decreased (P 0.10) by treatments. In conclusion, the improvement in protein gain associated with increasing lysine supplementation to achieve lysine requirement involved a general stimulation of whole-body turnover, protein synthesis being increased to a larger extent than protein degradation. Key words: Pigs, protein, metabolism, hormone, lysine, leucine