Low Crude Protein Level Research Articles

Rapid Dietary Protein Changes, Enzyme Activities, mRNAs and Plasma Hormones in the Broiler Chicken

Ross 708 broiler chickens were fed one of three levels of crude protein (12, 21 or 30%) from 7 to 28 days of age. Birds were then switched to either a higher (30%) or lower level of crude protein (12% and sampled three days following the switch. The purpose of these treatments was to test effects of changes in protein level at a representative time during the finisher phase (days 28 to 31) of broiler growth and to relate changes to metabolic plasma hormone levels (IGF-I, IGF-II, insulin, leptin, T3, T4, glucagons, Ghrelin) and regulatory enzymes [malic enzyme (ME), aspartate aminotransferase (AAT), and NADP-isocitrate dehydrogenase (ICD)] and their respective mRNAs The data from this experiment show that a priority of hormones can be established with respect to correlations between circulating values and representative metabolic enzymes and their mRNAs. It is suggested from these data that both IGF-I and T4 are equal in a metabolic priority scheme and are superior to glucagon and Ghrelin which are still significantly related to certain enzymes and their mRNAs. It is entirely possible that mRNA levels do not correlate or totally regulate enzyme protein (as evidenced by activities of regulatory enzymes) although the relationships for ME (R = 0.69; P<0.001), ICD (R = 0.64; P <0.001) and AAT (R = 0.47, P<0.001) does lend some credence that transcriptional events regulate these two enzymes.

Chemical and bromatological characteristics of elephant grass silages containing a mango by-product

This study was carried out to evaluate the nutritive value of elephant grass (Pennisetum purpureum, Schum.) silages with the addition of 0, 4, 8, 12 and 16% dehydrated mango (Mangifera indica, L.) by-product (DMB), on the fresh matter basis. A randomized complete design with four replications was used. As experimental silos, 210L plastic drums were used. Dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HCEL), ether extract (EE), total carbohydrates (TC), non-fibrous carbohydrates (NFC), neutral detergent insoluble nitrogen (NDIN, % total N), acid detergent insoluble nitrogen (ADIN, % total N), pH values, ammoniacal nitrogen (% total N), lactic acid, acetic acid, butyric acid and propionic acid levels were determined. The DM, OM, CP, EE, NFC, NDIN, lactic acid and propionic acid levels increased with the DMB addition while the NDF, ADF, hemicellulose, N-NH3/ammoniacal nitrogen levels and the pH values decreased with the DMB addition. The addition of DMB had a quadratic effect on the acetic and butyric acid levels but there was no effect with the addition of DMB on TC and ADIN. The DMB can be used at the ensiling of the elephant grass, because the addition of 8.6% improves the silages fermentative process. However, these silages have low crude protein levels and high contents of ether extract and nitrogen compounds mixed with the fiber (NDIN and ADIN) in the silages, that may damage their use by animals.

Chemical and nutritional quality of silage made from raw or cooked lizard fish (Saurida undosquamis) and blue crab (Portunus pelagicus)

AbstractTwelve silages were prepared from uncooked or cooked lizard fish (Saurida undosquamis) and blue crab (Portunus pelagicus) and stored at ambient temperature (30 ± 2 °C) for 60 days. The antioxidative effect of adding ethoxyquin was also investigated. Generally, the nutritional quality of all the silages was stable for up to 60 days of storage and the composition of raw materials was reflected in the composition of the silages. Crab had a lower level of crude protein than fish (85 versus 162 mg kg−1), but a higher level of ash (96 versus 36 g kg−1); moreover, there were significant differences in nutritional composition between uncooked and cooked materials. High level of ash in crab required addition of high levels of formic acid in crab‐related silages. At the end of the experiment cooked silages showed a tendency for spoilage; in particular, maggots were observed in cooked crab silages on the last few days of the experiment. Comparison of treatments with or without ethoxyquin showed that only rancidity of fish silage groups was higher without addition of ethoxyquin. Uncooked materials are more suitable for prolonged storage than cooked materials, and it is probably not necessary to add antioxidants to silages made from material with low lipid content. Copyright © 2009 Society of Chemical Industry

Developing a method for laboratory biosafety testing impacts of transgenic plants on non‐target insects

AbstractA series of laboratory experiments was carried out with the main objective of contributing to the development of biosafety testing methods for transgenic plants or plants produced by other novel technologies. The adult stage of a New Zealand native weevil, Nicaeana cervina (Broun) (Coleoptera: Curculionidae: Entiminae), was used as a test insect as this has become well‐adapted to introduced pasture species, feeding on both ryegrass [Lolium perenne L. (Poaceae)] and white clover [Trifolium repens L. (Fabaceae)]. Ryegrass plants used in experiments were infected with strains of the symbiotic endophytic fungi Neotyphodium lolii (Latch, M.J. Chr. & Samuels) and Epichloe festucae Leuchtm., Schardl & M.R. Siegel and included a transgenic endophyte, which was modified to eliminate production of the insect deterrent, peramine. Nicaeana cervina was exposed to these endophyte‐infected plants along with endophyte‐free ryegrass. Weevils were also exposed to white clover with high or low levels of cyanogens, and to white clover selections bred conventionally to contain high or low levels of crude protein. These bioassays were carried out sometimes over a series of time intervals, and weevil survival, feeding, and reproductive performance variables were measured. Nicaeana cervina survival was generally high, although feeding and oviposition were variable between experiments despite high replication in some cases. A summary of significant differences obtained across all experiments suggested that data on the proportion of weevils feeding and amounts of leaf material consumed were more often significantly different than treatment effects on survival or reproductive performance. A positive relationship between the proportion of weevils feeding and those ovipositing was found, suggesting that a 50% reduction in feeding would result in a 28% reduction in the proportion of weevils ovipositing. Power analysis using the range of values recorded for the variables measured indicated that for proportions of weevils surviving, feeding, or fecund, about 35–42 replicates would be required for a 40% difference in values. For measures of leaf consumption and numbers of eggs per female, fewer replicates were required for 95% power when these values were at the higher end of the range than when they were at the lower end of the observed range. The usefulness of the case study test insect and risk assessment protocols used for biosafety testing are discussed.

Suplementação de lisina e metionina em dietas com baixo nível protéico para o crescimento inicial do pacu, <em>Piaractus mesopotamicus</em> (Holmberg)

The objective of this research was to study the effects of methionine or lysine supplementation in diets with low protein level for growth of pacu Piaractus mesopotamicus (Holmberg) (Characiformes, Characidae). Diets were formulated as a basal diet presenting 22% crude protein (CP), 4100 kcal gross energy (GE)/kg, 0.42% of methionine and 1.16% of lysine and other six diets, with the same basic formulation, supplemented with 0.2%, 0.4% or 0.6% methionine or lysine. An eighth diet (control) contained 26% CP, 4100 kcal (GE)/kg, 0.48% methionine and 1.43% of lysine. The diets were administered ad libitum to 144 fingerlings with initial medium weight of 14.98 ± 1.16 g. Averages weight gain, gross energy efficiency retention and feed intake for the control treatment were significantly higher (P < 0.05) than those of smaller protein level diets. Averages protein retention efficiency were only higher (P < 0.01) in the diets supplemented with lysine, showing the advantages of lysine supplementation in diets with low crude protein level. A higher growth of pacu was confirmed with diets containing 26% of CP.

Formulação com aminoácidos totais ou digestíveis em rações com níveis decrescentes de proteína bruta para frangos de corte de 21 a 42 dias de idade

Foram realizados dois experimentos para avaliar a formulação de rações para frangos de corte com redução do nível de proteína bruta (PB) e suplementadas com aminoácidos sintéticos, formuladas com base nos aminoácidos totais - AAT (experimento 1) ou digestíveis - AAD (experimento 2). Os experimentos foram conduzidos no período de 3 a 6 semanas de idade das aves. Em ambos os experimentos, os quatros níveis de PB foram: 20,8; 19,7; 18,6 e 17,5% PB. No experimento 2, também foram testados outros dois tratamentos com rações contendo 20,8 e 17,5% de PB e alta digestibilidade (ADig), à base de milho, farelo de soja, amido de milho e proteína isolada de soja. Nos dois experimentos, o consumo de ração não foi afetado pela redução de PB. No experimento 1, o ganho de peso (GP), a conversão alimentar (CA) e os rendimentos de peito e de coxa foram afetados negativamente pela redução dos níveis de PB, enquanto, no experimento 2 estas variáveis não foram influenciadas. No entanto, em ambos os experimentos, na semana de 21 a 28 dias, o GP e a CA foram influenciados negativamente pela redução dos níveis de PB na ração. Com o decréscimo no nível de PB, a digestibilidade da matéria seca (MS) e da matéria orgânica (MO) aumentou no experimento 2, em virtude da menor inclusão de farelo de soja. Em ambos os experimentos, a retenção relativa de proteína foi superior para rações com baixos níveis de PB. No experimento 2, apesar de os níveis de PB não terem influenciado o desempenho, a ração de ADig proporcionou maior digestibilidade da MO e tendência à maior digestibilidade da MS. As rações com 17,5% PB e ADig promoveram balanço mais positivo e maior retenção relativa de proteína em comparação às de digestibilidade padrão. Considerando todos os resultados, a formulação de rações com AAD mostrou vantagens em relação aos AAT.

Chemical composition and in vitro ruminal fermentation of common tree forages in the semi-arid rangelands of Swaziland

Browse plants play an important role in providing feed for livestock in semi-arid rangelands of Africa. Chemical composition and in vitro ruminal fermentation of leaves collected from Acacia burkei, Acacia tortilis, Acacia nilotica, Dichrostachys cinerea and Ehretia obtusifolia in communal grazing lands in the lowveld of Swaziland is presented. Leaves were collected from trees located on two soil types ( i.e., lithosol and vertisol) in the communal land but it had no effect on the chemical composition of tree leaves. The NDFom and ADFom content were highest in D. cinerea and A. burkei and lowest in E. obtusifolia and A. nilotica. Crude protein (CP) contents ranged between 108 g/kg and 122 g/kg DM. D. cinerea had the highest Ca and Mg content, while A. tortilis had the lowest. There were marked variations in K level amongst browse species, with A. tortilis (9.1 g/kg DM) having the highest value. The P, Zn and Fe did not differ between browse species. Soil type and tree species interaction impacted in vitro fermentation parameters. Extent of fermentation, as measured by 48 h cumulative gas production, and organic matter degradability was highest in E. obtusifolia leaves and lowest in D. cinerea leaves within soil type. Fermentation efficiency, as measured by partitioning factors, was highest in A. nilotica leaves. Leaves of E. obtusifolia could be a valuable supplementary feedstuff for ruminant livestock due to its in vitro fermentation characteristics as well as low fibre and moderate CP levels.

Interactive effects of dietary crude protein and fermentable carbohydrate levels on odour from pig manure

The objective of this study was to determine the effects of dietary levels of crude protein (CP) and levels of fermentable carbohydrates (FC) and their interaction on odour emission, odour intensity, odour hedonic tone, and ammonia emission from pig manure, and manure characteristics. An experiment was conducted with finishing pigs ( n = 36) in a 2 × 3 factorial randomized complete block arrangement with 6 treatment combinations in 6 blocks. There were 2 dietary CP levels (low 12%; high 18%) and 3 digestible FC levels: (low 95.5; medium 145.5; and high 195.5 g/kg feed, as-fed basis). Pigs with an initial body weight (BW) of 57.7 ± 2.5 kg were penned individually in partly slatted floor pens. Faeces and urine of each pig accumulated in separate manure pits under the slatted floor. In the 6th week of the collection period air samples were collected directly above the manure in each pit. Manure samples were taken for manure characteristics. Air samples were analyzed for odour concentration and for hedonic tone and odour intensity. Manure samples were analyzed for volatile fatty acids (VFA), indoles, phenoles, sulphurous compounds, ammonium, and total N concentrations. Dietary CP level and FC level did not affect odour emission, odour intensity and hedonic tone but their interaction affected odour emission at P = 0.06. At a high dietary CP level, increased FC level decreased odour emission, while at a low CP level, increased FC level increased odour emission from pig manure. Total N and ammonium concentrations, and ammonia emission from pig manure were reduced at low dietary CP level ( P < 0.001). High FC level led to low ammonia emission from pig manure ( P = 0.01). Manure pH increased at high dietary CP level ( P < 0.001) and decreased when FC level increased ( P < 0.05). Total VFA concentration increased at high dietary CP level ( P < 0.001) and when FC level increased ( P < 0.001). Enhanced dietary CP increased the manure concentrations of phenol (P < 0.001), cresols ( P = 0.01), indole ( P < 0.001), 4-ethylphenol ( P < 0.001) and carbon disulfide ( P < 0.001), but FC did not affect concentrations of these compounds ( P > 0.05) in the manure. We conclude that the interaction between dietary CP and FC plays a role in odour production and emission. Ammonia emission from pig manure can be reduced substantially by decreasing dietary CP and by increasing FC.

Skatole and indole concentration and the odour of fat from lambs that had grazed perennial ryegrass/white clover pasture or Lotus corniculatus

An experiment was conducted for 111 days in the summer of 2002/2003 to compare the effect of grazing lambs on condensed tannin-containing Lotus corniculatus L. (cv. Grasslands Goldie; n = 12) and perennial ryegrass/white clover pasture (PRG/WC; Lolium perenne/ Trifolium repens; n = 12) on the concentration of indole and skatole in rumen fluid, blood plasma and body fat and upon the odour of the fat. Rumen fluid and blood samples were obtained on days 0, 22, 58, 87 and 111 of the experiment. Fat from inter-muscular and tail-stub depots was obtained at slaughter. During the experiment the mean concentration of indole and skatole in both the rumen fluid and blood plasma was lower for lambs grazing L. corniculatus compared to PRG/WC pastures. The concentration of skatole in the tail-stub fat was lower and less variable (P<0.05) in the lambs that had grazed L. corniculatus. No differences were observed in the odour of the inter-muscular fat from lambs that had grazed L. corniculatus compared to PRG/WC pasture, suggesting that the reductions in indole and skatole formation from grazing L. corniculatus were not large enough to produce a detectable difference in fat odour. The experiment was complicated by the on-set of drought conditions during the second half which resulted in a relatively lower level of crude protein in the L. corniculatus forage. It was concluded that CT-containing forages hold some potential to reduce the concentration of indole and skatole in the fat to provide consistently flavoured meat products from grazing systems.

Correlations among metabolic enzyme activities, their mRNAs and hormone levels in broiler chickens

Ross 708 broiler chickens were fed one of three levels of crude protein (12, 21 or 30%) from 7 to 28 days of age. Birds were then switched to either higher (12 to 30%, 21 to 30%) or lower levels of crude protein (30–12%, 21–12%). Birds were sampled three days following switches to their respective finisher diets. The purpose of these treatments was to test effects of changes in protein level during the finisher phase (days 28 to 35) of broiler growth and to relate changes to metabolic hormone levels and regulatory enzymes [malic enzyme, ME; aspartate aminotransferase, AAT; isocitrate dehydrogenase (NADP), ICD activities and mRNA]. Glucagon, IGF-I, T4 and Ghrelin were inversely correlated (P<0.01) to ME activities but, positively correlated to both ICD and AAT activities. The data from this experiment also shows that a priority of hormones can be established as far as correlations between circulating value and representative metabolic enzymes and their mRNA’s. It is suggested from these data that both IGF-I and T4 are equal in a metabolic priority scheme and are superior to glucagon and Ghrelin which are still significantly related to certain enzymes and their mRNA. It is entirely possible that mRNA levels may not correlate or totally regulate enzyme protein (as evidenced by activities of ME, ICD and AAT activities) although the relationships for ME (R = 0.69; P<0.01) and ICD (R=0.64; P<0.01 were significant.

Effects of dietary whole cottonseed and crude protein level on rumen protozoal population and fermentation parameters

In this investigation in vitro and in vivo trials were performed to determine the efficacy of a cottonseed to limit protozoal population and fermentation parameters. The composition of diets given to the different treatments were as follow: (1) control (without whole cottonseed), 16% crude protein (CP), 3.2% ether extract (E.E.); (2) 20% whole cottonseed, 16% CP, 6.5% E.E.; (3) 20% whole cottonseed, 13% CP, 6.4% E.E. and (4) 20% crushed whole cottonseed, 13% CP, 6.4% E.E. DM disappearance (DMD) and fermentation characteristics of the treatments were determined by in vitro incubation studies. In the in vivo trial, ruminal fluid was taken by rumenocentesis (3 h after feeding) on days 1, 3, 5, 7, 9, 11, 14, 21 and 28 from four sheep fed about treatment diets. The pH and protozoal counts were determined in each sample, while ammonia nitrogen and volatile fatty acid (VFA) were determined in samples taken on days 7, 14, 21 and 28. The in vitro DMD after 24 h incubation decreased ( p < 0.01) with the addition of cottonseed in diets 3 and 4 and DMD after 72 h incubation was highest ( p < 0.01) for the control diet. The fractional rate of gas production ( c) for the control and diet 2 was higher ( p < 0.05) than for the diets 3 and 4. Feeding crushed whole cottonseed decreased molar proportion of propionate ( p < 0.05) and increased molar proportion of butyrate ( p < 0.01). Low crude protein level increased the molar proportion of propionate ( p < 0.05) and decreased molar proportion of butyrate ( p < 0.05) and cellolytic protozoa population ( p < 0.05). Feeding cottonseed decreased ( p < 0.05) the total protozoa population from approximately 500,000 to 250,000 ml −1 and Holotrich and cellulolytic protozoa disappeared from the rumen of sheep and only Entodinium sp., remained. This was associated with lower concentration of ammonia nitrogen in rumen fluid of sheep fed diets 4 ( p < 0.05) and 2 ( p < 0.01). It was concluded that cottonseed reduced rumen fauna and ammonia nitrogen, but had no effect on ruminal VFA while the crushed whole cottonseed decreased molar proportion of isovalerate only. In vivo molar proportion of propionate and butyrate and valerate were increase and decrease, respectively, by decreasing CP percentage in treatment diets.

Effects of cattle feeding regimen and soil management type on the fate of Escherichia coli O157:H7 and salmonella enterica serovar typhimurium in manure, manure-amended soil, and lettuce.

Survival of the green fluorescent protein-transformed human pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium was studied in a laboratory-simulated lettuce production chain. Dairy cows were fed three different roughage types: high-digestible grass silage plus maize silage (6:4), low-digestible grass silage, and straw. Each was adjusted with supplemental concentrates to high and low crude protein levels. The pathogens were added to manure, which was subsequently mixed (after 56 and 28 days for E. coli O157:H7 and Salmonella serovar Typhimurium, respectively) with two pairs of organically and conventionally managed loamy and sandy soil. After another 14 days, iceberg lettuce seedlings were planted and then checked for pathogens after 21 days of growth. Survival data were fitted to a logistic decline function (exponential for E. coli O157:H7 in soil). Roughage type significantly influenced the rate of decline of E. coli O157:H7 in manure, with the fastest decline in manure from the pure straw diet and the slowest in manure from the diet of grass silage plus maize silage. Roughage type showed no effect on the rate of decline of Salmonella serovar Typhimurium, although decline was significantly faster in the manure derived from straw than in the manure from the diet of grass silage plus maize silage. The pH and fiber content of the manure were significant explanatory factors and were positively correlated with the rate of decline. With E. coli O157:H7 there was a trend of faster decline in organic than in conventional soils. No pathogens were detected in the edible lettuce parts. The results indicate that cattle diet and soil management are important factors with respect to the survival of human pathogens in the environment.

Lysine requirements of young broiler chickens are affected by level of dietary crude protein

Growth and body nitrogen and fat deposition in response to dietary lysine were assessed in chicks to 21 d of age when fed dietary crude protein (CP) at 170, 210, 250 or 290 g kg-1 diet. Response variables were evaluated using linear and quadratic regression, and linear-plateau models. In all cases, a better fit was observed with quadratic regression and linear-plateau models. Weight gain, F:G, and body nitrogen and fat deposition plateaued as dietary lysine was increased regardless of CP. Lysine requirements for weight gain to 21 d were significantly different when comparing 170 vs. 210 and 210 vs. 250 g CP kg-1 diets, although no differences were found when 250 and 290 g CP kg-1 were fed. Feed efficiency and body nitrogen responded in a similar manner to diet CP and lysine levels. Dietary lysine requirement increased as CP increased (170 vs. 210, and 210 to 250 g kg-1), although lysine requirement was unaffected when 250 or 290 g CP kg-1 diets are used. The requirements for lysine at low CP levels are better expressed as a percentage of CP. However, when dietary CP intake no longer limits growth, lysine needs should be specified as a diet percentage. Key words: Lysine, broiler chickens, nitrogen

Effects of Glycine and Threonine Supplementation on Performance of Broiler Chicks Fed Diets Low in Crude Protein

A study was conducted to evaluate effects of dietary crude protein (CP) level and Gly and Thr supplementation on performance of male broiler chicks during the period of 0 to 21 days. Diets were formulated based on NRC (1994) recommendations (Lysine at 110% of suggested level). All diets were formulated to contain 3,200 ME kcal/kg. A minimum dietary electrolyte balance of 250 meq/kg was stipulated with a minimum of 0.25% sodium and 0.20% chloride. Five primary diets were formulated to contain 16%, 18%, 20%, 22%, and 24% CP. The diets were then supplemented with additional 0, 0.2%, 0.4% Gly or 0, 0.2%, 0.4% Thr in all possible combinations resulting in a 5x3x3 factorial arrangement. Each of the 45 treatments was fed to six replicate pens of five male commercial broilers. The test diets and tap water were provided for the ad libitum consumption from 1 to 21 d of age. At 21 d of age body weight and feed consumption were determined. Reducing dietary protein below 22% significantly reduced 21 d BW and depressed feed conversion. Addition of 0.2 or 0.4% Gly significantly improved BW and numerically improved feed conversion at lower levels of protein but at protein levels of 20% or more the basal diets appeared to provide sufficient Gly. These data suggest that requirements for Gly suggested by NRC (1994) are inadequate in diets with low CP. Thr supplementation was ineffective in improving performance at low CP levels suggesting that the present recommendations of NRC (1994) are adequate. Mortality did not vary significantly among chicks receiving all experimental diets.

Environmental Systems Analysis of Pig Production - The Impact of Feed Choice (12 pp)

The purpose of this environmental system analysis was to investigate the impact of feed choice in three pig production scenarios using substance flow models complemented by life cycle assessment methodology. The function of the system studied was to grow piglets of 29 kg to finished pigs of 115 kg. Three alternative scenarios of protein supply were designed, one based on imported soybean meal (scenario SOY); one based on locally grown peas and rapeseed cake (scenario PEA) and one based on Swedish peas and rapeseed meal complemented by synthetic amino acids (scenario SAA). The environmental impact of both feed production as such and the subsequent environmental impact of the feed in the pig production sub-system were analysed. The analysed feed ingredients were barley, wheat, peas, rapeseed meal, rapeseed cake, soybean meal and synthetic amino acids. The crude protein level of the feed affected the nitrogen content in the manure, which in turn affected nitrogen emissions throughout the system and the fertilising value of the manure, ultimately affecting the need for mineral fertiliser application for feed production. The results showed that feed production contributed more than animal husbandry to the environmental burden of the system for the impact categories energy use, global warming potential and eutrophication, whereas the opposite situation was the case for acidification. The environmental impacts of scenarios SOY, PEA and SAA were 6.8, 5.3 and 6.3 MJ/kg pig growth; 1.5, 1.3 and 1.4 kg CO2-eq/kg pig growth; 0.55, 0.55 and 0.45 kg O2-eq/kg pig growth; and 24, 25 and 20 g SO2-eq/kg pig growth, respectively. The results suggested that scenario SAA was environmentally preferable, and that the reason for this was a low crude protein level of the feed and exclusion of soybean meal from the feed. Feed choice had an impact on the environmental performance of pig meat production, not only via the features of the feed as fed to the pigs, such as the crude protein content, but also via the raw materials used, since the environmental impact from the production of these differs and since feed production had a large impact on the system as a whole.

Valine requirement for maximal growth rate in weaned pigs

The objective was to define valine requirements for weaned piglets in the context of reducing dietary crude protein (CP). A total of 120 pigs were fed six diets with varying content of ileal digestible CP, valine and essential amino acids (EAA). Littermate piglets with initial live weights (±S.E.) of 8.0±0.1 kg were weaned at day 28 and fed with experimental diets for 4 weeks. The highest dietary level of CP, lysine and valine (12.1, 0.82 and 0.59 g apparent ileal digestible per MJ ME, respectively) were in accordance with the Danish Recommendations. Lower levels of CP, valine and EAA were obtained by reduced amounts of fishmeal in the diet formulations, while diets were fortified with crystalline AA. Reducing the CP level did not affect daily gain or feed conversion ratio (FCR). Lowering the valine:lysine ratio from 72% to 59% reduced the daily gain from 457 to 361 g per day and concomitantly raised the FCR from 23.7 to 26.0 MJ ME kg −1. Lowering the supply of CP and essential AA's by 15% reduced the growth rate by 8%. The requirement for valine to support maximal growth amounted to 0.59 g apparent ileal digestible valine per MJ ME.

The effect of commercially formulated, reduced crude protein diets, formulated to 11 apparent ileal digestible essential amino acids, on nitrogen retention by growing and finishing boars

Two experiments were carried out to determine the nitrogen retention (NR) and gross efficiency of NR (NR/NI) of boars offered diets with reduced crude protein (CP) levels designed to decrease nitrogen excretion. Six diets were compared which differed in CP content, from 177 to 253 g/kg and from 151 to 229 g/kg for growing and finishing boars, respectively. All diets were isocaloric and formulated to minimum amounts of all 11 essential amino acids on a determined apparent ileal digestible basis (IEAA), calculated from the lysine:IEAA ratio required for Ideal Protein (IP). Formulating the diets to all 11 IEAA was not sufficiently accurate to maintain dietary IP content at the lowest CP levels (177 and 151 g/kg). These two diets significantly increased NR/NI for the boars ( P<0.01) but this was not sufficient to maintain NR which was reduced in both the growing (13%; P<0.05) and the finishing (26%; P<0.001) boars. The two lowest CP diets also had a lower dietary electrolyte balance (dEB) which could have contributed to the reduction of NR.

Evaluation of Crude Protein Needs for Large White Male Turkeys from 16 to 20 Weeks of Age

A study was conducted to determine the minimum crude protein content of finisher diets based on corn and soybean meal supplemented with commercially available amino acids for male Large White turkeys. Diets were formulated to contain a minimum of 105% of NRC (1994) recommended levels of Met, Lys, TSAA, Thr, and Trp for diets fed 16 to 20 wk of age; no other essential amino acids were specified. The crude protein content of the diets ranged from 75 to 100% of the recommended level of 16.5%. When diets were formulated to contain at least the minimum recommended levels of Met, TSAA, Lys, Thr, reducing the crude protein content of the diet to less than 85% resulted in a significant reduction in weight at 20 wk or body weight gain from 16 to 20 wk. Addition of Ile and Val to diets formulated to contain 80 or 85% of the recommended crude protein level had no significant effect on body weight or weight gain, indicating that a deficiency of these amino acids per se was not responsible for the reduction in performance on diets with low levels of crude protein. Feed conversion was more variable and was not significantly influenced by dietary crude protein.

Protein and body weight accretion of chicks on diets with widely varying contents of soyabean meal supplemented or unsupplemented with its limiting amino acids

1. Two studies were conducted to evaluate the effects of relative deficiencies of methionine and threonine on the growth performance of 8- to 21-d-old chicks fed on isoenergetic diets containing a wide range of crude protein (CP) concentrations from dehulled soyabean meal (SBM). 2. Chicks fed on graded levels of SBM containing supplemental methionine and threonine (BAL) accreted whole-body protein more efficiently (P < 0.05) than those receiving graded levels of unsupplemented SBM (DEF), and superior (P < 0.05) growth performance was also obtained at lower CP levels when chicks were fed on the BAL diets. 3. Voluntary food intake increased between 30 and 220 g CP/kg in chicks fed on DEF diets, whereas food intake of chicks fed on BAL diets increased only between 30 and 100 g CP/kg, after which it decreased between 100 and 220 g CP/kg. 4. Protein efficiency ratio (g gain per g protein intake) decreased with each incremental increase in CP between 30 and 260 g CP/kg, regardless of whether diets were BAL or DEF. 5. These data indicate that maintaining a balanced ratio of amino acids is a preferable approach when poultry producers are interested in employing low CP diets for economic, physiological or environmental reasons.

The economic implications of bush encroachment on livestock farming in rangelands of Uganda

The objective of this study was to assess the economic implications of shrub encroachment on pastoral rangeland productivity in Mbarara district, in south western Uganda. Sixty pastoral households were surveyed, thirty of which were grazing on cleared farms (with less than 25% of grazing covered by bush) and thirty were grazing on bushy farms (with more than 75% of grazing land covered by bush). The study was a survey and did not involve rigorous experimental work. Results indicated that cleared farms had higher herbage dry matter yield ranging from 1 850 kg ha−1 to 2 230 kg ha−1, compared to a range of 622 kg ha−1 to 1 190 kg ha−1 on bushy farms. Heifers on cleared farms reached puberty earlier and calved relatively earlier (12-30 months) as opposed to 24-36 months on bushy farms. The mean calving rate on cleared farms was higher (33.6%) than 22.6% on bushy farms. Mean milk yield on cleared farms was 3.8 L cow−1 d−1 compared to 2.4 L cow−1 d−1 on bushy farms. Results of body condition score indicated that cattle on cleared range had a higher mean score of 5.8 compared to 4.2 on bushy farms. Mean annual gross income was US$49.393 per cow per annum on cleared farms compared to US$23.351 on bushy farms. Financial efficiency measured by TR/TVC ratio was 1.2 on cleared farms compared to 1.1 on bushy farms. From the findings of the study, it was concluded that shrub encroachment led to reduced herbage DM yield and low levels of crude protein of the pasture, while clearing more than doubled herbage DM production. As a result, animal productivity in terms of milk yield, body condition and reproductive performance were also reduced. Cleared farms were more profitable than bushy ones in terms of gross margins due to higher animal performance and hence higher incomes. The financial efficiency of cleared farms was low due to high costs of shrub control. Shrub encroachment is a serious problem facing pastoral production in Mbarara district and requires adequate attention.