Investigations of energy metabolism in weanling barrows: the interaction of dietary energy concentration and daily feed (energy) intake

Much of our understanding of energy metabolism in the pig has been derived from studies in which the energy supply was controlled through regulated feed intake. In commercial situations, where ad libitum feeding is practiced, dietary energy concentration, but not daily feed intake, is under producer control. This study evaluated the interactive effects of dietary energy concentration and feeding level (FL) on growth, body composition, and nutrient deposition rates. Individually penned PIC barrows, with an initial BW of 9.5 +/- 1.0 kg, were allotted to 1 of 9 treatments in a 3 x 3 factorial arrangement plus an initial slaughter group (n = 6) that was slaughtered at the beginning of the trial. Three NE concentrations (low, 2.15; medium, 2.26; and high, 2.37 Mcal of NE/kg) and 3 feeding levels (FL: 100, 80, or 70% of ad libitum access to feed) were investigated. Daily feed allowance for the restricted-fed pigs was adjusted twice per week on a BW basis until completion of the experiment at 25 +/- 1 kg of BW. Average daily gain, ADFI, and G:F were unaffected by NE (mean = 572 g, 781 g, and 0.732 g/g, respectively). Average daily gain and ADFI, but not G:F, increased (P < 0.05) with FL. Empty body lipid concentration increased with dietary NE concentration and with FL; a significant (P < 0.01) interaction revealed that empty body lipid concentration increased most rapidly as ADFI increased on the highest energy diet. Empty body lipid concentration was greatest in pigs with ad libitum access to the high-NE diet. Empty body protein concentration decreased with increasing NE (P < 0.05) but was not affected by FL. Empty body protein deposition (PD) increased with increasing FL (P < 0.001), but not with NE. Empty body lipid deposition (LD) and the LD:PD ratio increased (P < 0.01) in pigs with ad libitum access to the high-NE diet. In conclusion, NE did not interact with FL on growth, body protein concentration, or PD, suggesting that the conclusions regarding energy utilization obtained from experiments using restricted feed intake may not easily be applied to pigs fed under ad libitum conditions. The interactive effects of NE and FL on body lipid concentration, LD, and the LD:PD ratio indicate that changes in dietary energy concentration alter the composition of gain without necessarily changing overall BW gain. Consequently, the composition of gain is an important outcome in studies on energy utilization.     

Impact of early postweaning growth rate as affected by diet complexity and space allocation on subsequent growth performance of pigs in a wean-to-finish production system

The objective was to evaluate the effect of restricted early postweaning growth rate due to diet complexity, pen space, or both on subsequent growth to market in a wean-to-finish system. Pigs (n = 1,728) were used in a randomized block design with a 2 x 2 factorial arrangement of treatments: 1) diet complexity (Complex vs Simple) and 2) space allocation (Unrestricted vs Restricted). Treatments were imposed for the first 8 wk after weaning (period 1) and growth was measured from weaning (5.0 +/- 0.01 kg body weight; 15 d of age) to the end of wk 23 postweaning. The Simple diet was based on corn-soybean meal with minimal inclusion of milk products, processed cereals, and animal protein-based ingredients compared to the Complex diet. Floor and feeder-trough spaces were 0.63 m2 and 4 cm and 0.21 m2 and 2 cm per pig for Unrestricted and Restricted space treatments, respectively. From the end of wk 8 to end of wk 23 (period 2), pigs on all treatments had the same floor and feeder spaces and were fed common diets. There was no interaction (P > 0.05) between diet and space treatments. In period 1, Simple diets resulted in similar average daily feed intake (ADFI; 639 vs 650 +/- 5.4 g; P > 0.05), but lower average daily gain (ADG; 408 vs 424 +/- 3.8 g; P < 0.01) and gain:feed ratio (0.64 vs 0.65 +/- 0.002; P < 0.001), and lighter body weight (2.8%; P < 0.01) compared to the Complex diets. In period 2, growth was not affected (P > 0.05) by previous diet complexity, and pig body weight was similar (114.4 vs 114.4 +/- 0.37 kg, P > 0.05) at the end of wk 23. In period 1, pigs with Restricted space had lower ADG (398 vs 434 +/- 3.8 g; P < 0.001), ADFI (621 vs 668 +/- 5.4 g; P < 0.001), and gain:feed ratio (0.64 vs 0.65 +/- 0.002; P < 0.01), and were lighter at the end of wk 8 (6.5%; P < 0.001) than those with Unrestricted space. However, in period 2, pigs with Restricted space had higher (P < 0.01) ADG (3%), ADFI (2%), and gain:feed ratio (3%) than those with Unrestricted space, and body weight was similar (114.5 vs 114.3 +/- 0.37 kg; P > 0.05) at end of wk 23. Carcass backfat and loin-eye depth at market body weight were influenced by neither diet nor space treatment. Using a simple diet program and restricted space allowance immediately postweaning resulted in a lower early growth rate, but had no impact on pig body weight or carcass measures at market.     

Requirement of true ileal digestible threonine of growing and finishing pigs

Ninety-six crossbred barrows and gilts were used to investigate the optimum supply of true ileal digestible threonine for growing (approximately 35-65 kg body weight) and finishing (approximately 65-110 kg body weight) pigs. For this purpose, according to a bifactorial arrangement in the grower as well as in the finisher phase four dietary threonine levels were combined with two dietary levels of lysine. Measurement criteria were body weight gain, feed intake, feed conversion rate and carcass characteristics. In the grower stage at the lower lysine level daily gain increased numerically (p < 0.1) and the feed to gain ratio decreased significantly with an increasing dietary true ileal digestible threonine concentration. Increasing the true ileal digestible lysine concentration of the diet from 7.8 to 9.2 g/kg increased average daily gain in the grower stage significantly from 815 to 855 g and decreased the feed to gain ratio significantly. In finishing pigs, daily gain and feed to gain ratio were significantly improved by an increasing dietary true ileal digestible threonine concentration from 821 to 902 g and from 3.14 to 2.94 kg/kg, respectively, but not by the differing lysine supply. As in the grower stage, barrows consumed more feed than gilts at similar growth rates and this resulted in a significantly reduced feed to gain ratio in gilts compared with barrows. The requirements of true ileal digestible threonine for optimize both, daily gain and feed to gain ratio, as derived by the broken-line model were 10.3 g/animal and day for growing and 10.7 g/animal and day for finishing pigs respectively.     

Comparative growth performance of pigs immunised with a gonadotrophin releasing factor vaccine with surgically castrated pigs and entire boars raised under conventionally managed conditions

The objective of this study was to determine the effect of using a gonadotrophin releasing factor (GnRF) vaccine on growth performance of male pigs. Vaccinated pigs were compared with surgically castrated pigs and entire males under conventionally managed farm conditions. Male pigs were randomly assigned to three treatment groups: pigs surgically castrated during the first week of life (group "C", n=274), pigs immunised twice during the fattening period with a GnRF vaccine, the first when 13-14 weeks of age and the second when 20-21 weeks of age (group "V" n=280) and entire males (group "E", n=56). Average daily weight gain (ADG) was measured during the study. Additionally, feed conversion ratio (FCR) as defined by feed intake/weight gain and feed consumption was assessed during the fattening period. No difference in the ADG during the fattening period could be determined between "C" and "V". From the start of the study until slaughter at study day 160/173 the ADG in group "E" was lower (625 g/day; P) than in group "C" (681 g/day; P < 0.001) and group "V" (675 g/day; P < 0.01). The FCR during the fattening period until study day 160, three days before the first batch of pigs were slaughtered at 24-25 weeks of age, was higher in group"C" (2.72 kg feed intake/kg weight gain) compared with group "V" (2.44 kg feed intake/kg weight gain; P < 0.001) and group "E" (2.44 kg feed intake/kg weight gain; P <0.01). Pigs in group "V" performed similarly to those in group "E" until the second vaccination (day 135) after which time they showed a substantial increase in feed intake and ADG, while retaining an FCR advantage over group C.     

斜发沸石添加水平对育肥期苏淮猪生长性能、屠宰性能和肉品质的影响

本试验研究基础日粮中添加不同水平的斜发沸石对育肥期苏淮猪生长性能、肉品质的影响,旨在获得苏淮猪育肥期斜发沸石的适宜添加量。选择体重相近(50 kg左右)、健康的苏淮阉公猪40头,随机分为对照组、试验Ⅰ组、试验Ⅱ组、试验Ⅲ组共4个处理组,每组10头。预试期10 d,所有猪自由采食对照组基础日粮;正试期64 d,对照组饲喂基础日粮,试验Ⅰ至Ⅲ组分别在基础日粮中添加0.5%、1.0%和2.0%的斜发沸石。于试验结束屠宰全部试验猪,用于屠宰测定和肉质检测。结果表明:1)第1阶段(体重56~68 kg)和第2阶段(体重83~98 kg),终末体重、平均日增重、料重比均无显著差异;但斜发沸石水平对第1阶段和第2阶段平均日采食量影响显著(P<0.05)并呈线性(P=0.02,P=0.047)二次方升高趋势(P=0.01)。2)对照组、试验Ⅰ组、Ⅱ组和Ⅲ组苏淮猪的生长曲线拐点分别是:第50.26天86.06 kg、第40.22天87.15 kg、第38.27天89.69 kg和第45.98天89.02 kg;最大日增重分别是0.702、0.743、0.814和0.855 kg/d,说明在饲料中添加斜发沸石后,可延长育肥猪到达生长曲线拐点体重。3)斜发沸石水平对眼肌面积和肌内脂肪影响显著(P<0.05),眼肌面积随斜发沸石添加水平的升高,呈二次方(P=0.01)变化;肌内脂肪呈线性(P=0.01),二次方(P=0.03)升高;胴体重和系水力分别随斜发沸石添加水平的升高,呈线性(P=0.07,P=0.09)升高趋势。试验表明:苏淮育肥猪采食量、胴体重和肌内脂肪随日粮斜发沸石添加水平增加呈线性升高,系水力呈线性升高趋势,但眼肌面积随斜发沸石添加水平的升高,呈二次方变化,先升高后降低。因此,添加2%斜发沸石有利于采食量、胴体重和肌内脂升高,有助于系水力降低;但从增加眼肌面积的角度考虑,斜发沸石的适宜添加比例为1%。     

Effect of neomycin, carbadox and length of adaptation to calorimeter on performance, fasting metabolism and gastrointestinal tract of young pigs

Five sets of littermate gilts (8.2 +/- .19 kg average initial weight) were randomly assigned within litter to a 16% protein corn-soybean meal basal diet (B), B + .308% neomycin, or B + 55 ppm carbadox. Each set was equally-fed individually once daily for 16 d in metabolism cages and 5 d in calorimeters. The average daily feed intake for 21 d was 276 g. Oxygen consumption and CO2 production were measured during an 8- to 24-h postprandial period on d 16, 19, 20 and 21, and during a 32- to 48-h postprandial period after the d 21 feeding. Pigs were killed 50 h postprandially for gastrointestinal tract measurements. Dietary supplementation of antimicrobial agents (neomycin and carbadox) resulted in improvements (P less than .01) in daily gain and efficiency of feed utilization and lower (P less than .05) small intestinal mass in pigs. There was no difference (P greater than .05) in daily gain, feed efficiency or small intestinal mass between pigs fed neomycin- or carbadox-supplemented diets. Whole-animal fasting O2 consumption and CO2 production measured during the 8- to 24-h or 32- to 48-h postprandial period were not affected (P greater than .05) by the supplementation or the source of dietary antimicrobial agents. There were no differences (P greater than .05) in 8- to 24-h fasting O2 and CO2 measurements determined on d 16, 19, 20 and 21, indicating that adaptation to calorimeters was not needed by the pigs.(ABSTRACT TRUNCATED AT 250 WORDS)     

The antibody repertoire in infection and vaccination with Dictyocaulus viviparus: heterogeneity in infected cattle and genetic control in guinea pigs.

The antigen recognition profiles of serum antibody from calves infected or vaccinated with irradiated Dictyocaulus viviparus larvae were analysed by immunoprecipitation of radio-iodinated in vitro-released excretory-secretory materials from live adult parasites. Immunoprecipitates were analysed by SDS-PAGE and considerable heterogeneity in antigen recognition between individual animals was observed, regardless of infection regimen. This heterogeneity was also found to occur amongst outbred guinea pigs infected with the parasite and permitted an examination of the genetics of the effect using inbred guinea pigs (Strains 2 and 13). The antibody repertoires of the two strains were distinct, with only slight variation occurring between individuals within a strain. Previous work on nematode infections in rodents has demonstrated a role for the major histocompatibility complex (MHC) in the control of the immune repertoire. If this, as is probable, holds for the guinea pig, then it can be ascribed to the MHC Class II region because Strain 2 and Strain 13 bear identical Class I alleles but disparate Class II alleles. Whilst there is no evidence to date that the efficiency of vaccination of cattle is influenced by genetic factors, the operation of vaccines based on a single or a few molecularly cloned parasite antigens might be seriously compromised by the kind of genetic restriction to the immune repertoire described here.     

Direct and correlated responses to selection for efficiency of lean gain in mice

Improvement in feed efficiency when selection is based on gain:feed ratio has often been accompanied by a reduction in feed intake. The following four criteria were used in mass selection for improved lean gain efficiency in mice with an objective of evaluating changes in lean gain and intake: 1) gain deviation, animals selected had the greatest gain in fat-free mass (FFM) after adjustment to a constant intake; 2) intake deviation, mice selected had the least feed intake after adjustment to a constant gain in FFM; 3) intrinsic efficiency, similar to the second criterion except that adjustment was also made for average weight maintained during the period; and 4) a positive control that used the ratio of gain in FFM: feed intake as the selection criterion. A fifth line, in which a male and a female were selected at random from each litter, served as a negative control. Experimental animals were outbred mice of the CF1 strain. Two replicates of the five lines were included in the study. Twelve males and females were pair-mated within each line-replicate combination each generation. Feed disappearance was measured from 25 to 42 d. Mice were scanned to obtain an electrical conductivity measurement for prediction of FFM. After six generations of selection, realized heritabilities for gain:feed, gain deviation, intake deviation, and intrinsic efficiency were .00 +/- .04, .04 +/- .29, .35 +/- .08, and .28 +/- .06, respectively. There were no differences among lines for gain:feed ratio. The correlated response in feed intake reduction was significant in the intake deviation and intrinsic efficiency lines (-.17 +/- .05 and -.21 +/- .04 g x d(-1) x generation(-1), respectively). The realized genetic correlations between the ratio and gain deviation, intake deviation, and intrinsic efficiency were .83 +/- .15, .01 +/- .04, and .21 +/- .12, respectively. Litter size was depressed in all selected lines.     

Metabolic and microbial responses in western crossbred and Meishan growing pigs fed a high-fiber diet

Four Duroc x White composite crossbred (21.8 +/- 1.0 kg BW) and four 12-wk-old Meishan purebred (20.7 +/- 1.6 kg BW) growing barrows were used to determine the relative breed differences in metabolic and microbial responses to a high-fiber diet. The pigs were trained to consume 700 g of a diet containing 35% (as-fed basis) dehydrated alfalfa meal once daily. The pigs' daily intakes of DM, N, GE, NDF, and ADF were 610 g, 16.6 g, 2.64 Mcal, 150 g, and 88 g, respectively. On d 12 after surgical catheterization of the portal vein, ileal vein, and carotid artery, a 3-d total urine and feces collection was conducted. On d 24 after surgery, each pig was placed in an open-circuit calorimeter, and its catheters were connected to a system for simultaneous measurements of oxygen consumption by portal-drained viscera and by whole body, and the net portal absorption of VFA after a 24-h fasting and during a 5-h postprandial period. The VFA measured included acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids. A second 3-d total urine and feces collection was conducted on d 30 after surgery. There were no differences (P = 0.13) between the first and second collections in apparent total-tract digestibility coefficients for nutrients and N retention of pigs. Compared with Duroc x White composite crossbred pigs, Meishan pigs had lower (P = 0.05) apparent digestibility coefficients for DM, N, NDF, hemicellulose, and N retention, but their portal-drained viscera used a greater (P = 0.05) fraction of whole-body oxygen consumption. No differences (P = 0.12) were found between Duroc x White composite crossbred and Meishan pigs in total viable bacteria and cellulolytic bacteria from fecal samples, in vitro digestibility of alfalfa NDF fractions by fecal inocula, whole-body oxygen consumption, net portal absorption of VFA, total energy of absorbed VFA, and the potential of absorbed VFA for meeting the energy needs for whole-body heat production. These results indicate that, in contrast to previous beliefs, the ability of Meishan growing pigs to utilize a high-fiber diet is not superior to that of Duroc x White composite crossbred growing pigs.     

Correlated response to selection for litter size in pigs: I. Growth,fat deposition,and feeding behavior traits

Data on individually tested pigs from a line selected for litter size (H) and a control line (C) were used to estimate the correlated responses to litter size in growth, fat, and feeding behavior patterns from 75 to 165 d of age. During the test period, BW and ultrasonic midback (UMB) and loin (ULB) backfat were recorded periodically on the same animal. Individual voluntary feed intake (DFI), number of visits (NVD), and feeding time (FTD) were measured on a daily basis using an automatic feeding system. Third degree polynomial models with random regression coefficients were used to describe BW, UMB, ULB, DFI, NVD, and FTD as a function of age. The first derivative of the model for BW was used to estimate growth rate. Several measurements of efficiency were obtained using polynomial models on accumulated DFI, NVD, and FTD. The difference between the genetic means of animals from line H and line C was used to estimate correlated responses. The H pigs showed higher BW throughout most of the test period (2.29 +/- 0.90 kg at 135 d of age, P < 0.05) but they were not different (P = 0.18) from C pigs at the end of the test (102 kg, SD 9). Thus, despite both lines showing similar average growth rate on the test, line H grew faster at the start of the test (34 +/- 11 g/d, P < 0.01), but it grew more slowly by the end (-68 +/- 27 g/d, P < 0.05). Fat deposition rate differed between lines, with H pigs showing higher UMB (1.26 +/- 0.23 mm, P < 0.01) and ULB (1.32 +/- 0.28 mm, P < 0.01) at 165 d of age. The difference between lines in total on-test feed intake was not significant (P= 0.10), but intake was slightly higher in line H between 105 and 135 d of age (2.28 +/- 1.25 kg, P = 0.07). Line H showed a higher feed efficiency up to about 100 d of age, whereas line C performed better from this age until 165 d of age. However, differences never exceeded 18 +/- 6 g of weight gain per kilogram of feed consumption (P < 0.01). Total feed efficiency throughout the test period was slightly higher in line C (1.37 +/- 0.77 kg of weight gain after eating 185 kg of feed, P = 0.08). Lines H and C had distinct feeding patterns with regard to eating frequency. Pigs from line H ate less frequently, but instead they spent more time and ate more per visit. In the long term, selection for litter size could result in pigs with less capacity of lean growth.     

Weight increase following administration of insulin to rats with reduced feed intake]

Young male Wistar rats, adapted to single daily administration of feed (from 8.00 to 10.00 a.m.) were studied for the intake of feed, weight gains, and feed consumption per weight gain unit after administration of Superdep insulin in the dose of 10 u kg-1 of body weight. The time limitation of access to food reduced the over-all intake of feed and weight gains and adversely affected the utilization of feed, expressed as consumption per 1 g of weight gain. The administration of insulin partly compensated the adverse effect of the reduced feed intake; this was manifested by better utilization of feeds by the experimental group, in comparison with the control animals.     

Growth performance and immune response of two commercial broiler strains fed diets containing Lactobacillus cultures and oxytetracycline under heat stress conditions

1. Hubbard x Hubbard (HH) and Shaver x Shaver (SS) chicks given a dietary supplement of either 50 mg/kg oxytetracycline (OTC) or 1 g/kg Lactobacillus culture (LC) were exposed to 36 +/- 1 degrees C for 3 h daily from day (d) 21 to 42. 2. Prior to heat treatment, body weight (d 21) and weight gain (d 1 to d 21) of OTC and LC birds were greater than those fed the control diet. Chicks given LC had the best food efficiency followed by OTC and control birds during d 1 to d 21. Body weight (d 1 and d 21) and weight gain (d 1 to d 21) were greater for HH tlhan SS chicks. 3. After 3 weeks of heat exposure, birds receiving the LC diet had greater body weight and weight gain, higher food intake and lower food efficiency than OTC and control chicks. 4. Antibody production against Newcastle discase vaccine on d 21 was not affected by strain or diet. On d 42, while diet had negligible effect on this variable among the SS broilers, HH birds fed LC had higher antibody production than those on the control diet. 5. Neither strain nor diet had a significant effect on mortality.     

The effect of daily energy intake on growth rate and composition of weight gain in pigs

An experiment with 29 crossbred female growing pigs (Dutch Landrace × Dutch Yorkshire) was carried out to measure the effect of daily energy intake on growth rate, N retention (according to the balance method) and composition of the weight gain. The weight gain composition was analysed by slaughtering pigs at regular intervals between 25 and 110 kg live weight. Two levels of daily energy intake, at an adequate protein intake, were used, and pigs on both treatments were slaughtered at the same age.Differences in daily energy intake affected growth rate and composition of the weight gain. Restriction of the daily energy intake by 20% caused a 15% lower live weight gain and a 12% lower N retention. Carcass muscle growth was 8% lower and fatty tissue growth was lower by 28%. Growth of bone was unaffected. Chemical analysis of different parts of the body revealed that reducing the daily energy intake by 20% caused an 8% lower protein deposition and a 28% lower fat deposition in the total body. However, there were differences between different anatomical parts of the body.Efficiency of pig meat production is discussed in relation to the effects of energy supply on weight gain composition.     

Investigations on genetically modified maize (Bt-maize) in pig nutrition: fattening performance and slaughtering results.

A grower finisher performance trial with forty-eight pigs was designed to compare the growth performance of pigs fed diets containing either genetically modified (GM) Bt-maize (NX6262) or its parental maize (Prelude) line. During the experiment, the pigs were fed with a grower and a finisher diet both containing 70% maize investigated in a previously study which showed that they contained similar ME values and digestibility of crude nutrients. The pigs with an initial live weight of 23.9 +/- 3.0 kg were allotted to single boxes. During a 91 days growing period the pigs of both groups recorded equal performance in daily weight gain (AW) 815 +/- 93 vs. 804 +/- 64 g/d depending on equal amounts of feed intake 1.95 +/- 0.15 vs. 1.94 +/- 0.15 kg/d (parental vs. transgenic). The results confirm equal performance among growing-finishing pigs fed parental or genetically modified maize containing diets. For slaughtering the pigs were divided into 4 groups with a different duration of the finishing period. After slaughtering the carcass characteristic were registered.     

Water intake of weaned piglets from three to seven weeks old

One hundred and two large white cross landrace piglets weaned at 21 (+/- 1) days old were randomly allocated to one of two commercial early weaning diets for a four week growth trial. The piglets were housed in groups of between six and 10. After initial moderate restriction the piglets were fed ad libitum. Food intakes and weight gains were recorded weekly. Water consumption of individual pens of piglets was recorded daily. Dietary treatment had no significant effect on mean daily feed intake, daily liveweight gain or food conversion ratio. The relationship between water and food intake, piglet weight and daily gain was examined using regression and multiple regression analyses. Water intake was related to all these parameters, with daily feed intake being the best single predictor of water intake. The relationship was described by the equation: water intake (litres/day) = 0.149 + 3.053 feed intake (kg/day).     

地顶孢霉培养物对黑豚生长性能、屠宰性能和免疫器官指数的影响

为研究地顶孢霉培养物对黑豚生长性能、屠宰性能和免疫器官指数的影响,试验随机选取90只黑豚,将其分成3组(对照组、低剂量组、高剂量组),对照组、低剂量组、高剂量组分别在基础日粮中添加0、0.1%、0.2%的地顶孢霉培养物,测定生长性能、屠宰性能和免疫器官指数检测指标。结果表明:低剂量组与对照组相比,日均增重、半净堂率、脾脏指数均显著提高(P<0.05),料重比显著降低(P<0.05);高剂量组与对照组相比,日均增重、日均采食量、屠宰率、半净堂率、脾脏指数、肝脏指数以及肾脏指数均显著提高(P<0.05),料重比显著降低(P<0.05);高剂量组与低剂量组相比,日均增重、日均采食量、屠宰率以及半净堂率均显著提高(P<0.05)。说明黑豚基础日粮中添加0.1%和0.2%的地顶孢霉培养物均能改善黑豚的生长性能、屠宰性能和免疫器官指数,且0.2%添加剂量的作用效果更为显著。     

Dynamics of body protein deposition and changes in body composition after sudden changes in amino acid intake: II. Entire male pigs

A study was conducted to evaluate the extent and dynamics of whole body protein deposition (Pd) and changes in chemical and physical body composition after a period of AA intake restriction in entire male pigs with high lean-tissue growth potentials. Fifty-eight entire male pigs (initial BW 15.8 +/- 0.9 kg) were allotted to 1 of 3 dietary AA levels between 15 and 38 kg of BW: control (15% above requirements), AA-15% (15% below requirements), and AA-30% (30% below requirements). Thereafter, pigs were fed diets not limiting in AA content. Throughout the experiment, pigs were scale-fed at 90% of estimated voluntary daily DE intake. Representative pigs were slaughtered at 15, 38, 53, 68, or 110 kg of BW to monitor changes in body composition. Between 15 and 38 kg of BW, restriction of AA intake reduced BW gain (P < 0.01; 794, 666, and 648 g/d for control, AA-15%, and AA-30%, respectively). At 38 kg of BW, AA intake restriction increased whole body lipid (LB) content (P < 0.01; 11.3, 14.3, 17.5% of empty BW), and the LB-to-whole body protein (PB) ratio (LB/PB; P < 0.02; 0.68, 0.88, 1.10 for control, AA-15%, and AA-30%, respectively). Relationships between PB versus whole body water and PB versus whole body ash were not affected by dietary treatments (P > 0.10). At 110 kg of BW and based on BW, PB, and LB/PB, complete compensatory growth (CG) was achieved. Body weight gain between 38 and 110 kg of BW was inversely related to previous dietary AA levels (P < 0.01; 1,089, 1,171, and 1,185 g/d for control, AA-15%, and AA-30%, respectively). For pigs on the control diet, and based on N-balance data, Pd increased with BW, from 172 g/d at 40 kg of BW to 226 g/d at 82 kg of BW. At 40 kg of BW, Pd was greater (P < 0.05) for pigs on the AA-15% (205 g/d) and AA-30% (191 g/d) diets than pigs on the control diet (172 g/d). These findings indicate that pigs with high lean-tissue growth potentials are more likely to express compensatory Pd and their genetically determined upper limit to Pd (PdMax) after a period of AA intake restriction. This study confirms previous findings that BW effects on PdMax are small in growing pigs between 40 and 80 kg of BW. It is suggested that CG and compensatory Pd after a period of AA intake restriction is constrained by the pig's PdMax and is driven by a target LB/PB. Combined with previous observations in our laboratory, these results suggest that CG after a period of AA intake restriction tends to occur only when pigs are within the energy-dependent phase of lean-tissue growth and not when the genetically determined upper limit to lean-tissue growth, or PdMax, determines growth performance.     

Performance of finishing pigs in hoop structures and confinement during winter and summer

Performance of finishing pigs in hoop structures or confinement during winter and summer was evaluated in Iowa. Hoops are large, tent-like shelters with cornstalks or straw for bedding. During summer and winter seasons for 3 yr (1998 to 2001), six trials were conducted using three hoop barns (designed for 150 pigs per pen, one pen per hoop) or a mechanically ventilated confinement barn with slatted floors (designed for 22 pigs per pen, six pens in the barn). A total of 3,518 pigs started the trials. Summer trials were June through October, and winter trials were December through April. Target stocking density was 1.11 m2/pig in hoops and 0.74 m2/pig in confinement. Identical corn-based diets were fed ad libitum from 16 to 118 kg for 127 d. Pigs were scanned before harvest for backfat and loin muscle area. When seasons were merged (season x housing interaction, P > or = 0.05), hoop-fed pigs had more backfat (21.8 +/- 0.3 vs 20.8 +/- 0.2 mm; P < 0.001), smaller loin muscle area (41.3 +/- 0.3 vs 43.0 +/- 0.2 cm2; P < 0.001), less lean percentage (51.1 +/- 0.2 vs 52.1 +/- 0.1%; P < 0.001), and less yield (74.9 vs 75.8 +/- 0.1%; P < 0.001) than confinement-fed pigs. When season x housing type interactions were observed (P < 0.004), summer hoop-fed pigs had greater ADG (834 +/- 5 vs 802 +/- 3 g/d; P < 0.001), required fewer days to 113 kg (174.9 +/- 0.9 vs 178.5 +/- 0.6 d; P < 0.01), had similar ADFI (2.40 +/- 0.03 vs 2.35 +/- 0.02 kg/d, as-fed basis) and gain:feed (G:F; 348 +/- 4 vs 342 +/- 3 g/kg) compared with confinement-fed pigs. Lean gain/day and efficiency of lean gain did not differ between housing systems. During winter, hoop-fed pigs had similar ADG (794 +/- 5 vs 801 +/- 3 g/ d), required more days to 113 kg (176.7 +/- 0.9 vs 172.9 +/- 0.6 d; P < 0.01), had greater ADFI (2.54 +/- 0.03 vs 2.35 +/- 0.02; P < 0.001), less G:F (313 +/- 4 vs 341 +/- 3; P < 0.001), less lean gain/day (312 +/- 2 vs 322 +/- 1 g/d; P < 0.01), and less efficiency of lean gain (130 +/- 2 vs 144 +/- 1 g lean gain/kg feed; P < 0.01) than confinement-fed pigs. Percentage of mortalities and culls did not differ between housing systems. During summer, there was a trend for fewer light pigs at marketing (< 100 kg) from hoops (0.8 vs 1.7%; P = 0.10). During winter, there were more light pigs at marketing from hoops (3.9 vs 1.3%; P = 0.01) than from confinement. Bedding use in hoops was 92 and 122 kg/pig for summer and winter, respectively. Performance of finishing pigs in bedded hoop structures depends in part on thermal environment.     

Drinking preferences in chinchillas (Chinchilla laniger), degus (Octodon degu) and guinea pigs (Cavia porcellus)

Chinchilla (Chinchilla laniger), degus (Octodon degus) and guinea pigs (Cavia porcellus) are South American rodents living in a semi‐arid habitat with varying, species‐specific adaptations to water deprivation. Nonetheless, several diseases have been linked to insufficient water intake when these species are kept as pets, such as urolithiasis or obstipation. This study evaluated preferences for drinking systems. Six animals of each species were given a choice between an open dish and a nipple drinker. Food intake and water intake were measured daily for 13 days. Chinchillas in this study had significantly lower water intakes than the other two species, indicating particular species‐specific adaptations to aridity. All chinchillas favoured open dishes, whereas the degus and guinea pigs had variable individual preferences. Water intake of chinchillas was similar or higher in this study than in previous studies where nipple drinkers were used. The results indicate that degus and guinea pigs can meet their drinking water needs with nipple drinkers; for chinchillas, other drinking systems may be more adequate.     

Rates of muscle protein breakdown in chickens selected for increased growth rate, food consumption or efficiency of food utilisation as assessed by N tau-methylhistidine excretion

1. N tau-methylhistidine excretion, growth rate, food consumption and body composition was determined in 12 4 to 5 week old chickens sampled from each of 4 lines selected for increased body-weight gain (line W), for increased food consumption (line F), for improved efficiency of food utilisation (line E) or at random (line C), after 12 generations of selection. 2. The use of N tau-methylhistidine as an index of myofibrillar protein breakdown was validated in male and female chickens of lines E and F by following the fate of injected N tau-(14CH3)methylhistidine. Most of the radioactivity (79.3 +/- 1.1%) was excreted in 4 d, with the remainder retained in the carcase. In excreta, 94 +/- 2% of the radioactivity was associated with free N tau-methylhistidine and for the carcase, this value was 88 +/- 3%. 3. In the main experiment, final body weights averaged 497, 651, 588 and 537 g and food: gain ratio averaged 2.47, 2.21, 3.14 and 2.06 for lines C, W, F and E respectively, Carcase protein content (g/100 g body weight) was not different between the lines. 4. N tau-methylhistidine excretion was 5.86, 5.48, 6.43 and 4.99 mumoles/mole carcase-N/d for lines C, W, F and E, respectively. The rate for line F was significantly higher than for lines W and C and that for line E was significantly less than for the control line. 5. The N tau-methylhistidine excretion rate was positively correlated with food: gain ratio. 6. Selection for rapid growth, high food consumption or improved food utilisation results in changes in N tau-methylhistidine excretion which suggest proportionate changes in muscle protein turnover.