Daily Digestible Energy Intake Research Articles

Avaliação da Silagem de Diferentes Híbridos de Sorgo (Sorghum bicolor, L. Moench) por meio do Desempenho de Novilhos de Corte Confinados

Este experimento foi conduzido com o objetivo de estudar os parâmetros relativos ao consumo de alimentos, ganho de peso, conversão alimentar e eficiência energética de novilhos de corte em confinamento, alimentados com quatro dietas contendo silagem de híbridos de sorgo de comportamento agronômico diferenciado: AGX-213 e AG-2002 (forrageiro), AGX-217 e AG-2005E (duplo propósito). Foram utilizados 48 novilhos com idade média de 19 meses e peso médio inicial de 316 kg. A relação volumoso:concentrado foi de 63:37, para todas as dietas testadas. Não houve interação entre fonte de volumoso e período de avaliação em confinamento. A silagem do híbrido AG-2005E propiciou maior consumo de matéria seca e energia digestível, ganho de peso médio diário e melhor conversão alimentar frente aos demais genótipos testados. A análise de contraste mostrou que a inclusão de silagens de sorgo forrageiro (AGX-213 e AG-2002) à dieta alimentar causou redução significativa de 8,84 e 12,11% no consumo voluntário de matéria seca e energia digestível, respectivamente, frente às silagens de sorgo de duplo propósito (AGX-217 e AG-2005E). Animais alimentados com silagem de sorgo com características de duplo propósito apresentaram maior ganho de peso médio diário (1,163 contra 0,943 kg) e foram mais eficientes na transformação de matéria seca e energia digestível consumida em ganho de peso vivo (PV) (7,65 contra 8,73 kg de MS/kg de PV e 19,76 contra 21,84 Mcal/kg de PV).

Harvesting, rumination, digestion, and passage of fruit and leaf diets by a small ruminant, the blue duiker.

Because small ruminants (<15 kg) have a high ratio of metabolic rate to fermentation capacity, they are expected to select and require low-fiber, nutrient-dense concentrate diets. However, recent studies suggest that small ruminants may not be as limited in their digestive capacity as previously thought. In this study, we examined harvesting, rumination, digestion, and passage of three diets (domestic figs Ficus carica, fresh alfalfa Medicago sativa, and Pacific willow leaves Salix lasiandra) ranging from 10 to 50% neutral detergent fiber content (NDF) in captive blue duikers (Cephalophus monticola, 4 kg). Harvesting and rumination rates were obtained by observing and videotaping animals on each diet, and digestibility and intake were determined by conducting total collection digestion trials. We estimated mean retention time of liquid and particulate digesta by administering Co-EDTA and forages labelled with YbNO3 in a pulse dose and monitoring fecal output over 4 days. Duikers harvested and ruminated the fig diet faster than the alfalfa and willow diets. Likewise, they achieved higher dry matter, energy, NDF, and protein digestibility when eating figs, yet achieved a higher daily digestible energy intake on the fresh willow and alfalfa than on the figs by eating proportionately more of these forages. Duikers maintained a positive nitrogen balance on all diets, including figs, which contained only 6.3% crude protein. Mean retention time of cell wall in the duikers' digestive tract declined with increasing NDF and cellulose content of the diet. Digestibility coefficients and mean retention times of these small ruminants were virtually equivalent to those measured for ruminants two orders of magnitude larger, suggesting that they are well adapted for a mixed diet.

Palha de trevo vesiculoso (Trifolium vesiculosum Savi cv. Yuchi) como substituto da silagem de milho na alimentação de novilhos confinados

O experimento teve como objetivo avaliar a utilização da palha de trevo vesiculoso como substituto parcial da silagem de milho, na fração volumosa da dieta fornecida para novilhos confinados, sendo testados os seguintes níveis de substituição: T0 constituído por 100% de silagem de milho; T25 constituído por 75% de silagem de milho mais 25% de palha de trevo vesiculoso; T50 por 50% de silagem de milho mais 50% de palha de trevo vesiculoso e T75 constituído por 25% de silagem de milho mais 75% de palha de trevo vesiculoso. O teor de concentrado na dieta oferecida foi de 32,5%. As dietas foram fornecidas durante 112 dias para novilhos com peso e idade inicial de 265 ± 1,65kg e 18 meses, respectivamente. Os dados foram submetidos à análise de regressão para nível de substituição (NS) de silagem de milho por palha de trevo vesiculoso na fração volumosa da dieta. O consumo voluntário de matéria seca (CMS) em kg de MS/100kg PV (CMSP) ou em g/kg PV0,75 (CMSUTM) decresce linearmente à medida que aumentou o nível de palha de trevo. O consumo de energia digestível diário expresso em Mcal/100kg PV (CEDPV) também decresceu linearmente conforme a equação: CEDPV = 7,22905 - 0,025941 NS. O ganho de peso médio diário (GMD) observado foi de 1,25; 1,18; 1,07 e 1,01, respectivamente. A análise de regressão mostrou que o aumento de uma unidade percentual de substituição de silagem de milho por palha de trevo provocou um decréscimo de 3,47g no GMD e piorou a conversão alimentar em 0,017 unidades. Apesar de causar uma redução no desempenho animal, a inclusão de palha de trevo vesiculoso na fração volumosa da dieta de bovinos é viável, tendo em vista que, mesmo no nível de substituição mais elevado, o GMD dos animais foi de um quilograma, o que demonstra o seu potencial de utilização na produção de bovinos.

Feeding Ecology of Two Wintering Geese Species at Poyang Lake, China

ABSTRACT The feeding ecology of the swan goose (Anser cygnoides) and the white-fronted goose (A. albifrons albifrons) overwintering at Poyang Lake, the largest freshwater lake in China, was studied from 1990 to 1991. The daily patterns of these geese showed differences of the activity categories between species. The energy intakes of these geese were estimated by fecal analysis, daily dropping counts, and calorie determinations. The average daily digestible energy intakes of these geese were about twice their basal metabolic rate. Roots of Vallisneria asiatica, Acorus calamus, and Cates sp. were the main food for the swan goose. The leaves of Carex sp. were the main food of the white-fronted goose. The diets of the geese do overlap with those of some other waterbirds, mainly that of the Siberian crane (Grus leucogeranus) in Poyang Lake. This, however, is not a main reason for the decrease of the number of geese in winter in this season.

DESEMPENHO DE GENÓTIPOS DE NOVILHOS PARA ABATE AOS CATORZE MESES, GERADOS POR FÊMEAS DE DOIS ANOS

O objetivo deste trabalho foi avaliar o desempenho de machos Hereford (H), ½ Jersey (J) ½ H e 5/8 H 3/8 Nelore (N), gerados por fêmeas acasaladas aos 14 meses de idade, confinados do desmame, aos sete meses, até o abate aos 14 meses, quando atingiram em média 195 kg de carcaça. A relação volumoso:concentrado foi decrescente, iniciando em 70:30 e finalizando em 40:60. O volumoso utilizado incluiu silagem de sorgo forrageiro, cana-de-açúcar e feno de aveia. Os consumos diários de matéria seca e de energia digestível dos três grupos de novilhos não diferiram significativamente, mas os novilhos ½ J ½ H apresentaram maior consumo de matéria seca por 100 kg de peso vivo em relação aos outros dois grupos. Não houve diferença no ganho de peso médio diário durante os 193 dias de confinamento. A eficiência de conversão, expressa em Mcal de energia digestível e em quilogramas de matéria seca, para cada quilograma de ganho de peso, também não diferiu significativamente entre os três grupos testados.

Utilization of old meadow by reindeer in spring in northern Norway

&lt;p&gt;Utilization of abandoned coastal meadows in northern Norway by reindeer (Rangifer tarandus tarandus) were investigated for 25 days in spring 1996 (&amp;laquo; = 12, 40-57 kg body mass (BM)) and 24 days in 1997 (&amp;raquo; = 12, 39-61 kg BM). Grass production on grazed and ungrazed meadow was measured both years. Faecal dry matter (DM) production and ruminai in vitro DM digestibility (IVDMD) of selected plants were measured in the reindeer 15-22 days after the grazing experiment started each year. During the grazing period mean, standard deviation (s), temperature was 8.7, s = 2.8, &amp;deg;C in 1996 and 11.0, s = 3.0, &amp;deg;C in 1997, while temperature the first week was significantly higher in 1997 (P &amp;lt; 0.05). Mean herbage mass, on ungrazed meadow (control), after one week of plant growth in 1996 (408, J" = 166, kg DM ha"1) was significantly different (P &amp;lt; 0.05) from 1997 (576, s = 110, kg DM ha'). We believe the low temperature the first week in 1996 affected the plant production, and was the main reason for the significant (P &amp;lt; 0.05) difference in mean daily plant DM production on the grazed meadow between 1996 (57, s = 16, kg DM ha') and 1997 (81, s = 16, kg DM ha"1). Mean ruminai IVDMD of a mixture of meadow plants, differed (P&amp;lt;0.05) between 1996 (72.4, s = 1.0, %) and 1997 (83.9, s = 1.3, %), and mean daily food intake in 1996 (82, s = 13.5, g DM/kg0 75) was significantly lower than the intake in 1997 (131, s = 15.8, g DM/kg0 75). Daily digestible energy intake in reindeer was estimated to 0.96 Ml/kg07"5 X d 1 in 1996 and 1.85 Ml/kg""5 X d"1 in 1997, which was 1.3 and 2.5 times the resting metabolic rate in reindeer, respectively. We therefore assume the difference in food intake could be due to the initial difference in herbage mass.&lt;/p&gt;

Effect of dietary forage: concentrate ratio on the behaviour, rumen fermentation and circulating concentrations of IGF-1, insulin, glucagon and metabolites of beef steers and their potential effects on carcass composition

AbstractIn an investigation of factors responsible for the lower efficiency of carcass lean gain seen previously in steers offered grass silage diets 18 Simmental × British Friesian steers (361 (s.e. 5-35) kg) were offered one of three diets: a perennial ryegrass silage ad libitum and alone (S) or supplemented with rolled barley at 300 g/kg of total dry matter (SC) or supplemented as described but restricted (SCr) in quantity so as to provide the same dry matter (DM) and digestible energy (DE) intakes as for S. Eating (Eb), ruminating (Rb), standing (Sb) or lying (Lb) behaviour was quantified during four 24-h periods of manual observation. Eb was noted in more detail in a second experiment using computerized Calan-Broadbent gates and load cells to monitor times and rates of eating. Blood was taken via temporary indwelling jugular catheters at 30 to 60 min intervals on each of 4 days 1 month apart. Rumen fluid was sampled hourly for three 24-h periods from three rumen-cannulated steers given the same three diets in a separate 3 x 3 change-over design experiment.Steers offered the restricted diet SCr ate most of their food in one extended meal within 6 h of feeding while two peak eating periods (morning and evening) were observed in steers offered the other two diets. Steers offered SCr spent more time in Sb (P &lt; 0.05), and less time in Eb (P &lt; 0·001) and Rb (P &lt; 0·05) activities than did animals offered the two diets ad libitum (SC and S). Mean 24 h insulin-like growth factor-1 (IGF-1) concentrations and postprandial insulin concentrations were significantly higher with diet SCr than with diet S (P &lt; 0·001) despite equal daily DM and DE intakes from each. Insulin appearance in the jugular vein reflected the pattern of food intake on all treatments. Rumen fermentation characteristics were largely unaffected by diet. Mean 24 h rumen volatile fatty acid, pH and ammonia concentrations did not differ between diets but post-prandial rumen pH tended to be lower in animals offered the SC and SCr diets.Differences in patterns of food intake between animals offered food ad libitum and at a restricted level are likely to determine patterns of nutrient absorption and the secretion of nutritionally regulated splanchnic hormones. The higher proportions of Sb and Rb activities in steers offered the restricted diet represent an energy cost to these animals while the higher plasma IGF-1 and insulin concentrations also seen in these animals may collectively influence the partitioning of nutrients to the peripheral tissues and contribute to the increased efficiency of carcass lean deposition previously shown in animals offered such diets.

Plasma aldosterone and electrolyte concentrations in exercising thoroughbred horses fed two diets in summer and winter

In a replicated 4 × 4 Latin square experiment conducted in summer, eight mature Thoroughbred horses received two diets, control and fat-supplemented, and were exercised at two fitness levels designed to increase daily digestible energy (DE) requirements to approximately 150% (fitness level I) and 200% (fitness level II) of maintenance. In a second experiment during the winter, horses received the two diets in a switchback design and exercised at fitness level II. After 3 wk adaptation to treatments, feed and fecal samples were collected and horses galloped a standardized exercise test (SET) designed to increase the heart rate above 185 bpm for 1200 m. Vital signs were monitored and blood samples were obtained. Feed intake increased as fitness level increased (P < .05). Horses on the fat-supplemented diet required less feed (P < .05) to meet the energy requirements at a given fitness level. Daily DE intake was higher (P < .05) for the horses exercised at fitness level II to meet the increased metabolic demands. Heart rate, respiration rate and rectal temperature all increased (P < .05) with exercise. No treatment effects were found for heart rate (P >. 10) or rectal temperature (P > .30). Horses exercised in the winter had lower (P < .05) respiration rates, indicative of less problems dissipating excess body heat. Plasma aldosterone concentrations increased (P < .05) with exercise, corresponding to an increase in plasma K concentrations. Horses exercised in the summer exhibited higher (P < .05) plasma aldosterone concentrations than horses worked in the winter. Plasma CI and Na concentrations did not change (P > .30) with any treatment or exercise, indicating that the horses were not sufficiently stressed to induce any significant dehydration.

Energy Intake Relationships for White-Tailed Deer on Winter Browse Diets

Food intake by white-tailed deer (Odocoileus virginianus) is affected by digestibility, but this relationship has not been well quantified for natural winter diets. We studied relationships between digestible energy (DE) content of winter diets and intake of food and DE by white-tailed deer in Maine. We fed 8 winter browse diets varying in DE content and 1 pelleted commercial diet to 9 captive fawns in 4 sets of digestion trials. Digestible energy content of browse diets ranged from 1.95 to 2.39 kcal/g. Dry matter intake (g/kg 0.75 /day) and DE intake (kcal/kg 0.75 /day) were positively and linearly related to dietary DE (r 2 = 0.75-0.82, P ≤ 0.01). Daily DE intake (DEI) of browse diets by deer provided 30-88% of maintenance requirements. When dietary DE was 2.2 kcal/g, the reported minimum DE value at which deer can regulate intake at maintenance requirements (Ammann et al. 1973), DEI of fawns in the present study was only 63% of maintenance. The 2.2 kcal/g threshold, commonly considered a minimum requirement for dietary DE, appears inadequate for maintenance on winter browse diets. We estimated that fawns on diets composed of >70% hardwood browses would lose ≥30% body mass. Therefore, more digestible foods such as northern white cedar (Thuja occidentalis), lichen (Usnea spp.), and possibly litterfall (deciduous leaves and conifer shoots) may be important winter forages

Economic values of traits for pig improvement. II. Estimates for New Zealand conditions

A computer model simulating life cycle production of a breeding sow and growth performance of her offspring was used to estimate economic values of reproduction and growth performance traits. The model simulated digestion and metabolism of dietary nitrogen in growing pigs (20 to 85 kg), based on the linear/plateau relationship between daily protein deposition and digestible energy intake. Economic values (EVs) of reproduction and growth performance traits were calculated by simulating effects of genetic changes in several biological components, in a farrow-to-finish production system, assuming ad libitum feeding. Results demonstrated that economic values of traits depended on the average genetic merit in the pig herd and its interaction with the management circumstances (level of feeding, nature of the diet, life cycle length) of the production system.

Economic values of traits for pig improvement. I. A simulation model

A computer model simulating life cycle production of a breeding sow and growth performance of her offspring was developed to estimate economic values of reproduction and growth performance traits. A biological growth model, simulating the digestion and metabolism of dietary nitrogen in growing pigs (20 to 85 kg), was part of the life cycle model. The growth model was based on the linear/plateau relationship between daily protein deposition and digestible energy intake. A farrow-to-finish production system, with slaughter pigs marketed at fixed liveweights, was simulated. Input variables were: gilt age at first oestrus, weaning to oestrus interval, number of pigs born alive per litter, and pre-weaning mortality for each parity. Economic inputs included prices of feed ingredients, carcass returns and non-feed costs. The upper limit to body protein deposition rate, mean daily ad libitum digestible energy intake and minimum lipid to protein deposition ratio were assumed the major genetic determinants of pig growth. The model output included average daily gain, ad libitum daily feed intake, backfat thickness, and life cycle reproductive performance and profit. The combined life cycle profit was expressed in the form of an Annualized Present Value. Life cycle profit was calculated for a range of simulated pig genotypes.

Peak Sustained Metabolic Rate and Its Individual Variation in Cold-Stressed Mice

Is long-term sustained metabolic rate (SusMR) subject to a ceiling value? If so, what physiological or evolutionary factors impose that ceiling, and is the ceiling value independent of the type of energy stress? We determined food intake and daily digestible energy intake (DEI) as measures of SusMR, and resting metabolic rate (RMR), in mice that were energy stressed by being maintained at cold ambient temperatures. We compared these values with those from previous studies of mice that were energy stressed by peak lactation. We also measured intestinal brush-border nutrient uptakes, body lean and fat masses, and masses of the small intestine, heart, kidneys, and liver. Even with ad lib. quantities of a high-fat diet available, mice could not survive at temperatures below -15° C. Body mass declined at low temperatures because of depletion of body fat reserves. Food intake increased 2.5-fold, RMR 1.5-fold, and masses of the small intestine, heart, and kidneys by 30%-70% with a decrease in temperature from 23° C to -15° C. Intestinal hypertrophy served to restore the reserve capacity of intestinal nutrient transporters that would otherwise have been swamped by the increased food intake. The values reached by sustained metabolic scope (SusMR/RMR), food intake, and intestinal mass were still considerably below those of lactating mice, even though mice at temperatures below -15° C died in the presence of excess food. Thus, intestinal capacity was not the ultimate reason for an inability to survive at lower temperatures. Analysis of individual variation showed that those mice with unusually high food intake, DEI, or RMR tended to have unusually large hearts, kidneys, and intestines. Those organs are essentialfor high energy budgets (reflected in high DEIs), but they also incur large maintenance costs themselves (reflected in high RMRs).

The food intake, performance and carcass characteristics of two pig genotypes grown to 120 kg live weight

AbstractUsing a completely randomized design, 72 individually penned pigs, comprising two genotypes (Masterbreeders Mastergilt × Large White and Sovereign × Large white progeny) with equal numbers of boars and gilts, were given foodad libitumfrom 25 to 60 kg live weight. From 60 to 120 kg one-third of the pigs continued to be given foodad libitumwhilst the remainder were given one of two levels of restriction (0.85 and 0.925 of maintenance energy × 3.5). Diets were calculated to provide 13.8 and 13.0 MJ digestible energy (DE) per kg air-dry weight for growing and finishing phases respectively. Ultrasonic measurements of backfat at the P2 site were made at 10 kg intervals from 60 to 120 kg live weight and carcass measurements taken at slaughter. Complete dissection of ham joints was carried out. Predictedad libitumintakes were based on established equations but daily intakes were much lower than these values and no treatment provided food restriction compared with them. Daily DE intakes (mean of both genotypes) obtained at 25, 60, 90 and 120 kg live weight were 204, 30.7, 36.2, and 414 MJ (i.e. 3.5, 3.1, 2.9 and 2.7 × maintenance). During the growing (25 to 60 kg live weight) and finishing (60 to 120 kg live weight) periods boars grew faster (P&amp;lt; 0.01 andP&amp;lt; 0.001) than gilts (881v.827 and 944v.806 g/day) with corresponding improvements in food conversion ratio (P&amp;lt; 0.001). Boars had lower killing-out proportions (0.787v.0.801;P&amp;lt; 0.001). Mean P2 values for boars and gilts were 13.2 and 13.9 mm respectively (excluding skin). Greater quantities of muscle were found in the hams of boars than gilts (662.7v.642.3 kg;P&amp;lt; 0.05) but no difference between the sexes for ‘eye muscle’ area was observed (43.3v.45.0 cm2). Results show the apparent potential of modern hybrids to achieve good growth rates despite moderate food intakes and their ability, even when given continuous access to food, to produce very lean carcasses at relatively heavy slaughter weights.

Dynamic and Static Phases of Severe Dietary Obesity in Sheep: Food Intakes, Endocrinology and Carcass and Organ Chemical Composition

The chronology of changes in body weights, food intakes and plasma concentrations of selected metabolic hormones and metabolites were determined in sheep during the induction (dynamic) and static phases of diet-induced obesity. Lean adult Dorset ewes weighing 47 kg were fed a pelleted hay-grain diet at maintenance (lean; n = 7) or were fed the same diet ad libitum to a maximum intake of 3 kg·sheep-1·d-1 (obese; n = 8) for 78 wk. Body weight of obese sheep doubled (97 vs. 47 kg) by wk 42 of ad libitum intake. Average daily intakes of dry matter (12.8 g/kg) and digestible energy (165 kJ/kg) were comparable in maintenance-fed lean sheep and ad libitum-fed obese sheep consuming maintenance after wk 50, which began the static phase of obesity. Fasting plasma concentrations of insulin in the obese sheep increased steadily from 50 ± 6 pmol/L at wk 0 to a sustained plateau of 249 ± 21 pmol/L after wk 30. Plasma levels of glucose, immunoreactive glucagon and thyroid hormones were consistently greater (P < 0.05) in obese sheep than in lean sheep after wk 2, 3 and 25, respectively, of the experiment. Concentration of lipid (49 vs. 25%) in the carcass stripped of internal fat was greater (P < 0.01) in obese sheep than in lean sheep, but concentration of protein (10.4 vs. 15.3%) was less in the heavier carcass (58 vs. 24 kg) of the obese sheep. We conclude that hyperinsulinemia and abnormal fuel metabolism are early events during dynamic obesity and these defects persist throughout the static phase of obesity. Maintenance energy requirements relative to unit body weight (W1.0) seem similar in lean and dietary obese sheep.

INTAKE AND DIGESTIBILITY IN STEERS FED GRASS HAY SUPPLEMENTED WITH CORN OR BARLEY AND FISH MEAL OR SOYBEAN MEAL

Twenty crossbred steers (493 ± 6 kg) were used to study the effects of two types of cereal (cracked corn or rolled barley) and two protein supplements (fish meal or soybean meal) on voluntary intake and apparent digestibility of grass hay based diets for beef steers. Diets contained 65% concentrate and 35% roughage as fed. Daily digestible energy intake, expressed as MJ kg−0.75 body weight, was 15% higher in steers fed barley (P &lt; 0.01) and 10% higher when fish meal was fed instead of soybean meal (P &lt; 0.04). Apparent digestion coefficients of DM and acid detergent fiber were similar for the four diets. Apparent protein digestibility was 30.5% higher in steers receiving barley (P &lt; 0.01). Energy digestibility was slightly higher (6.5%, P &lt; 0.14) for animals receiving barley compared with those receiving corn, probably because digestibility of barley starch was 7.3% higher (P &lt; 0.01). Thus, digestible energy values of barley diets were 6.3% higher than those of corn diets. The results suggest that rolled barley was superior to cracked corn and fish meal superior to soybean meal when fed with grass hay to steers. Key words: Cattle, fish meal, soybean meal, corn, barley

RATE AND EFFICIENCY OF GAIN, BODY COMPOSITION, NITROGEN METABOLISM, AND BLOOD COMPOSITION OF GROWING HOLSTEIN STEERS GIVEN DEITS OF ROUGHAGE OR CONCENTRATE

To assess the effects of diet (roughage vs. concentrate) on energy utilization and protein metabolism, growing Holstein steers were given equal daily intakes of digestible energy from one of three diets: hay alone (diet 1; 12% protein), 85% concentrate and 15% hay (diet 2; 16% protein), and 85% concentrate and 15% hay (diet 3; 12% protein). The ratio of protein to digestible energy was the same in diets 1 and 2. At 100, 200, 300, 400, and 500 kg liveweight, estimates were obtained of digestibility and metabolizability of the diets, of weight of gastrointestinal digesta, of body composition based on the volume of distribution of tritiated water, of the concentration of a number of constituents in blood and of VFA in rumen fluid, of fractional degradation rate of skeletal muscle protein based on the urinary excretion of NT-methyl histidine, of the concentration of ammonia in rumen fluid and bacterial urease associated with the reticulo-rumenal epithelium, and of the concentration of total protein, and of the myofibrillar and sarcoplasmic protein fractions, in skeletal muscle. As a proportion of the weight of the empty body, water and protein were higher and fat was lower in steers on diet 1 than in those on diets 2 and 3. Empty liveweight gain in the steers on the concentrate diets (diets 2 and 3) was 35% greater than in steers on the hay diet (diet 1), and steers on concentrate required only 73% as much metabolizable energy per unit empty liveweight gain and 57% as much energy per unit energy gain as steers on hay. Daily gains of fat and energy were greater in the steers on concentrate than in those on hay and most of the extra gain of the steers on concentrate was attributable to gain of fat. Steers on concentrate had lower levels of triglyceride and higher levels of insulin and glucose in blood, and higher levels of propionate and lower levels of acetate in rumen fluid, than did steers on hay. There were no diet effects on the composition of skeletal muscle nor on the fractional degradation rate of muscle protein. Nitrogen metabolism in the rumen, and associated effects on blood urea and urinary nitrogen excretion, were the same in steers on diets 1 and 2 but different for steers on diet 3. However, fecal nitrogen output was the same for steers on diets 2 and 3 but much higher in steers on diet 1. These results are consistent with the view that the higher rate of gain of fat in steers on concentrate, as compared with those on hay, was not due to effects on the availability of protein for productive purposes or on protein metabolism in skeletal muscle, but was more likely to have been due either to lower rates of protein turnover in other tissues, such as those of the gastrointestinal tract, thus sparing energy for fat synthesis, or to a less efficient utilization of the energy available for fat synthesis. The latter possibility appears to be compatible with the finding of higher levels of circulating insulin in steers on the concentrate diets. Key words: Growth, efficiency, body composition, cattle

Protein and energy retention by growing rabbits offered diets with increasing proportions of fibre

SummaryNinety-six young rabbits (48 males, 48 females) each weighing 08 kg were offered one of six diets to appetite (n = 8 per treatment) or at one of four restricted feeding levels (n = 2 per treatment). All animals were culled at ca. 2 kg body weight and carcass analysis was carried out. Nutrient retention was estimated by the comparative slaughter technique.Five of the experimental diets (A–E) were formulated to contain increasing concentrations of a poor-quality grassmeal (0, 100, 300, 500 and 700 g/kg, respectively), the remainder of the diet consisting predominantly of ground oats and soya-bean meal. A sixth diet (F) was based on a common laboratory rabbit diet (SGI). All diets contained similar digestible crude protein (DCP): digestible energy (DE) ratios of ca. 13·1 g DCP/MJ DE. Acid detergent fibre concentrations in diets A–F were 146, 158, 213, 264, 321 and 180 g/kg dry matter (D.M.), respectively.When feeding to appetite, growth rates were depressed at the highest inclusions of grassmeal (diets D and E). Growth rates (GR) and voluntary food intakes (VFI) for diets A–F were: GR (g/day): 40, 41, 43, 36, 30 and 40; VFI (g D.M./day): 93, 103, 120, 137, 159 and 111, respectively. The depression in growth rate on diets D and E was associated with a reduction in total daily DCP and DE intake. The data suggested that, when the DE content of the diet falls below 10·5 MJ/kg D.M., the young rabbit is unable to compensate further by increasing daily VFI. Males grew significantly faster than females (40 cf. 37 g/day) and females had fatter carcasses at slaughter (301 cf. 274 g fat/kg carcass D.M.).Relationships between daily N and energy intake and their retention in the body of the growing rabbit were calculated using data from both restricted and ad libitum-fed animals. Daily energy retention (ER, kJ) was related to daily DE intake (DEI, kJ) by the equation: ER = –227 + 6 x DEI (b ranged from 0·407 to 0·502, according to diet).The estimated maintenance energy requirement of the growing rabbit ranged from 351 to 434 kJDE/kg0·75 per day and the average value across all diets was 377 kJ DE/kg0·75 per day.Daily N retention (NR, g) was related to daily digestible nitrogen intake (DNI, g) by the equation: NR = –0·398 + 6 x DNI (b ranged from 0·589 to 0·667, according to diet).The estimated N requirement for maintenance ranged between 0·464 and 0·525 g DN/kg0·75 per day and the average value across all diets was 0·497 g DN/kg0·75 per day.

Influence of diurnally fluctuating high temperature on growth and energy retention of growing pigs

Abstract The effects of two temperatures (thermoneutral, 22°C v. fluctuating high temperature, 35·22°C), four food levels (ad libitum and three levels of food restriction) on growth and energy retention of growing pigs (male and female) was investigated in a 2 × 2 × 4 factorial experiment involving 48 individually penned pigs from 20 to 50 kg live weight. A second experiment was conducted over the 50 to 80 kg liveweight range using a 2 × 2 × 3 design.Mean daily digestible energy (DE) intake, daily gain, P2 backfat thickness, carcass fat proportion, total body energy retained and body energy retained as protein did not differ significantly between the temperature treatments in either experiment. Mean carcass protein proportion was greater at 35·22°C than at a constant 22°C.With pigs given food ad libitum during the 50 to 80 kg phase, an increase in temperature from 22°C to 35·22° reduced daily DE intake by 4·1 MJ (38·9 v. 34·8 MJ or 300 g food per day), reduced energy retention by 2·3 MJ/day (15·6 v. 13·3 MJ/day), and increased carcass protein proportion by 11 g/kg (142 v. 153 g/kg).There was a significant interaction between the effects of sex and temperature on P2 backfat thickness over both live-weight ranges. Female pigs housed at 35·22°C had 2·6 mm less P2 backfat at 50 kg (13 v. 15·6 mm) and 2 mm less at 80 kg (20 v. 22 mm) compared with females housed at 22°C. The P2 backfat thickness of male pigs did not vary at 50 kg (13·2 v. 13·5 mm) but when housed at 35·22°C males had 1·4 mm more P2 backfat at 80 kg (18·2 v. 19·6 mm).

Amino acid and energy interactions in growing pigs. 3. Effects of sex and live weight and cereal on the responses to dietary lysine concentration when fed ad libitum or to a restricted food scale on diets based on wheat or barley

ABSTRACTThe responses of growing pigs to dietary lysine as influenced by sex (male and female) and cereal (barley and wheat) were investigated in an 8 × 2 × 2 factorial experiment involving 128 pigs. The basal barley-soya bean (13·4 MJ digestible energy (DE) per kg) and wheat-soya bean (14·1 MJ DE per kg) diets were offered ad libitum from 20 to 50 kg live weight. The eight dietary lysine concentrations were 70 to 140 g/kg in increments of 1·0 g/kg. The experiment was repeated with pigs given food according to a restricted scale. Performance in both experiments was assessed by multiple regression analysis based on data from successive 10-kg live-weight intervals. Analysis of variance was used to assess chemical carcass composition and retention of protein and fat after slaughter at 50 kg live weight.Average daily DE intake (MJ) of pigs fed ad libitum was not significantly different for barley-based (27·4) and wheat-based diets (29·1). For pigs fed on a restricted scale, average daily DE intake was 18 MJ for barley-based and 17·5 MJ for wheat-based diets. The daily energy retained in the empty carcass, expressed as a proportion of daily DE intake, was proportionately 0·08 less for barley-based than for wheat-based diets irrespective of whether food was offered ad libitum (0·347 v. 0·379) or restricted (0·311 v. 0·337).The average daily gain of females fed ad libitum was not affected by dietary lysine concentration. With males, the response of daily gain to lysine concentration was curvilinear, increasing to a maximum of 120 g dietary lysine per kg up to 40·3 kg and 7·0 g/kg at greater weights for both cereals. For pigs fed on a restricted scale the daily gain on barley diets increased linearly up to the maximum dietary lysine concentration (14 g/kg), while for those on wheat-based diets maximum daily gain occurred with a lysine concentration of 11·2 g/kg for males and 131 g/kg for females. Carcass P2 backfat (mean = 15·4 mm), carcass fat proportion (mean = 242 g/kg) and carcass protein retention (mean = 89 g/day) were not significantly affected by dietary lysine concentration from 7 to 14 g/kg when pigs were fed ad libitum. However, when pigs were fed at a restricted level carcass fatness decreased to a minimum at 12 g lysine per kg.

Effect of environmental temperature and dietary energy concentration on the performance and carcass characteristics of growing-finishing pigs fed to equal rate of gain

An experiment involving 54 individually-housed castrated male pigs was conducted to determine the interactive effects of environmental temperature (12, 20 or 28°C) and dietary-energy density (13.0 vs. 15.0 MJ digestible energy (DE) kg −1) on the performance and carcass characteristics of growing-finishing pigs, fed to achieve equal rate of weight gain at any treatment. The diets were based either on maize with supplemental maize oil (high-energy diet), or on barley with supplemental wheat bran (low-energy diet). There was no temperature × dietary-energy density interaction ( P > 0.10) for any parameter studied. Daily DE intake, and the amount of DE required per unit of body weight gain (BWG) or empty body weight gain (EBWG), increased quadratically ( P < 0.01) as environmental temperatures decreased. Additional DE required to compensate for 1°C drop in temperature between 28 and 20°C, and between 20 and 12°C, amounted to 0.20 and 0.44 MJ day −1, respectively. The environmental temperature had no substantial effect on the total fat of the carcass. However, the body fat distribution was modified: backfat weight and thickness were increased ( P < 0.05) in the cold, whereas weight of leaf fat was decreased ( P < 0.05). The decrease in temperature was associated with a linear increase ( P < 0.01) in the backfat unsaturation rate.