A five point radial response surface design supplemented with a control group and several single factor points was utilized to investigate the effects of sodium bicarbonate and disodium phosphate on animal performance, ruminal fermentation, ration digestibility and rate of passage of liquid and particulate phases of digesta. Rations contained 0 to 4.5% sodium bicarbonate and 0 to 2.5% disodium phosphate.. Calves were randomly assigned to experimental rations, eight to the control group, six to the centerpoint, two to the radial points and three to the single factor points with restrictions as to time. Animals were on a growth trial from wk 7 to 14. Human samples were taken for determination of pH, buffering capacity, volatile fatty acids anct ruminal ammonia and blood samples for determination of glucose and plasma urea nitrogen at 8, 11 and 14 wk. Rate of passage was determined using ytterbium and cobalt EDTA to follow the particulate and liquid phases of digesta respectively. A digestion trial was carried out concurrently with rate of passage determinations. A two compartment model and a gamma time-dependent model were fitted to marker excretion data. Average daily gains were not significantly affected by buffer additions, but appeared to be maxillial at 1 to 2% sodium bicarbonate and 0% disodium phosphate. Average daily gain and feed efficiency were not changed. Buffers consistently elevated total concentration of volatile fatty acids and osmolality in the rumen. Proportion of volatile fatty acids and acetate to propionate ratio were not changed by buffer addition. Digestibility of dry matter, organic matter, neutral detergent fiber, starch and acid detergent fiber are unchanged. Sodium bicarbonate increased ash digestibility while disodium phosphate tended to decrease ash digestibility. Urine volume and pH were increased by both buffers. Rumen dilution rate for liquid digesta was increased by 50% and particulate digesta increased by 25% with addition of buffers. Flow of liquid digesta was best described by a two compartment model and particulate digesta by a gamma time-dependent model. No benefit of manipulating rate of passage in young dairy calves was observed in this study. Manipulation of ruminal fermentation by rate ot passage has potential to increase; milk production by bypassing starch and protein. Rates of flow of particulate digest may exert important affects on the ruminal acetate to propionate ratio and has potential to explain milk fat depression. / Ph. D.

Early weaning onto pasture, separate grazing for ewes and lambs on pasture, and weaned and nonweaned lambs in a drylot were compared with control groups of ewes and lambs grazed together at Blacksburg and Glade Spring in 1960 and 1961. Data were available on 457 lambs for average daily gain and slaughter grade and on 311 lambs for carcass grade and yield. The data were adjusted for the effects of breed of sire, breed of dam, age of dam, sex, and type of birth and rearing. Comparing the pasture treatments at both Blacksburg and Glade Spring in 1960 and 1961, in a two-way classification, in the analysis of variance there was a highly significant interaction between years and treatments. There was no significant difference between the high and low roughage ration that was fed to weaned and nonweaned lambs at both stations. The weaned lambs on the low roughage ration at Blacksburg performed significantly better at the 5 percent level than the pasture groups, for average daily gain. The means were higher for the other three traits, though not significantly so. At Glade Spring the drylot lambs that were weaned had a significantly higher mean at the 5 per cent level for yield over the control group, and the means were higher for the other three traits. / Master of Science

no abstract provided by author / Master of Science

Two metabolism trials were conducted with 12 crossbred wether lambs, each surgically prepared with a rumen catheter, and abomasal and ileal cannulae to study the effect of K infusion in the different sites on site of absorption and flow of minerals. The treatments consisted of the infusion of 33.6, 12.0 or 12.0 g K/d as bicarbonate into either the rumen, abomasum or ileum, respectively. Each trial consisted of a minimum 5 d preliminary period, five 3 d collection periods of feed, feces and urine for determining mineral balance and a 6 d sampling period of feed, abomasal and ileal contents and feces for determining mineral flow and site of absorption. Chromic oxide was used as a marker. Magnesium was absorbed primarily from the preintestinal region. Ruminal infusion of K tended to decrease preintestinal Mg absorption. Total Mg absorption was decreased ( P<. 05) by 43% when K was infused into the rumen. There was a slight absorption of Mg in the small intestine followed by a net secretion of Mg into the large intestine. Serum Mg levels tended to be depressed in the animals infused with K intraruminally. Calcium flow into the preintestinal region was decreased ( P<. 05) by infusion of K into the rumen. Generally, a net secretion of Ca occurred in the preintestinal region and in the large intestine, with the small intestine being the major site of absorption. Only animals being infused with K in the rumen secreted Na into the preintestinal region. The large intestine was the primary site of Na absorption. Phosphorus flow into the preintestinal region was decreased (P<.05) by infusion of K into the rumen. The small intestine was the main site for P absorption. Potassium flow into both the preintestine and small intestine was increased (P<.05) by ruminal K infusion. The flow of K into the small intestine was increased by ileal K infusion. The infusion of K increased (P<.05) the absorption of K as compared to the control animals with the small intestine being the major absorptive site. The infusion of K bicarbonate into the rumen of sheep raised (P<.05) the pH of the rumen. / M.S.

Four studies were performed to examine peripheral factors involved with food intake regulation in the domestic fowl. In the first study, the mechanism by which tryptophan depresses food intake was clarified. Intraperitoneal injections of tryptophan methyl ester were demonstrated to inhibit feeding in Single Comb White Leghorn (SCWL) cockerels. Intragastric intubations of tryptophan inhibited food intake and decreased body temperature of SCWL cockerels. These results, in conjunction with previous findings, indicate that tryptophan's inhibitory influence on food intake is peripherally rather than centrally based. The second study explored the role of the duodenum in food intake regulation. Intraduodenal glucose loads had no effect on food intake of SCWL or Rock Cornish (RC) commercial broiler cockerels. In addition, splanchnicectomized birds did not respond to intraduodenal glucose infusions any differently than sham-operated controls. Apparently, the duodenum does not play a significant role in food intake control in the fowl. Hepatic involvement in appetite regulation was examined in SCWL and RC cockerels in the third study. Amino acid solutions failed to influence food intake when infused intraportally in either strain of chicken. Relatively small glucose or lipid solutions depressed food intake significantly when infused intraportally in the SCWL birds but had no effect in the RC cockerels. The liver appears to be integrally involved in controlling food consumption in the SCWL chicken. In the final study, the existence of a "hunger" factor in the peripheral circulation of two lines of chickens divergently selected for body weight was explored. Intrahepatic infusions of plasma from food deprived high-weight line chickens stimulated food intake of sated low-weight line chickens. These studies indicate that peripheral mechanisms are important in regulating appetite in light-breed chickens such as the SCWL, however, such mechanisms in heavy-breed chickens such as the RC appear to be less sensitive. This desensitization in heavy-breed chickens suggests that genetic selection for increased growth has affected the food intake control systems. / Ph. D.

Two experiments were conducted to quantitate the effects of several parameters on the growth, carcass characteristics and fat deposition of the turkey. In the first experiment, 0, 5, 10 or 15% fat from three sources (Fat 1, Fat 2 or Fat 3) was added to low (18%), standard (21%) or high (24%) protein diets fed to Nicholas Large White male turkeys from 8 to 22 weeks of age. Carcass quality as measured by fat deposition, carcass yield and breast meat yield was determined. The addition of each 1% added fat up to 10% increased body weight gain .72%. Feed consumption decreased 1.3% and feed efficiency increased 2.3% for each 1% added fat up to 15%. Addition of Fat 2 to the diet resulted in significantly better feed efficiencies as compared with Fat 1 or Fat 3. The feeding of low protein diets as compared with standard protein diets decreased body weight gain, feed consumption and feed efficiency 13.2, 5.7 and 8.1%, respectively. Addition of fat to the diet increased 22-week body weight and the amount of breast meat produced per kg feed consumed. For each 1% added fat to low and standard protein diets, leaf and gizzard fat deposition increased 10.2 and 8.0%, respectively. Feeding low protein diets resulted in a 10.4% decrease in body weight and a 19.5% decrease in breast meat yield. The increase in leaf and gizzard fat deposition from each 5% increment of added fat up to 10% was counteracted by a 3% increase in dietary protein. In the second experiment, both sexes of the Nicholas Large White, Jaindl Large White and Jaindl Medium White strains were fed standard (21%) or high (24%) protein diets containing 0, 5 or 10% added dietary fat from 8 to 28 weeks of age. Carcass quality as measured by yield of carcass parts, fat deposition and the composition of breast meat was determined at 16, 20, 24 and 28 weeks of age. The Nicholas strain of turkey had a greater growth rate and consumed less feed to reach heavier weights than the Jaindl Large strain. Addition of 10% fat to the diet decreased feed consumption 12% and increased feed efficiency 17%. Fresh carcass and breast meat yield increased with age of the turkey, indicating that marketing at younger ages does not take full advantage of the meat producing capability of the turkey. The Jaindl Large and Medium White strains averaged 6.8 and 6.9% more breast meat yield than the Nicholas strain. The Nicholas strain deposited 4.36 times more leaf fat and 1.84 times more lipid within the breast meat as compared to the Jaindl Large strain. Added dietary fat decreased fresh carcass yield .41% and breast meat yield .65%. Feeding high protein diets increased fresh carcass yield and breast meat yield .25 and .47%, respectively. / Ph. D. / incomplete_metadata

Growth, reproduction, and immunocompetence were measured in lines of chickens maintained under different feeding regimens. Populations included a commercial broiler breeder parent line segregating at a sex-linked feathering locus (K, k⁺) and 4 experimental lines of which 2 had undergone 32 generations of divergent selection for 56-day body weight and 2 were their sublines in which selection has been relaxed for 5 generations. Mild feed restriction of the broiler line from 7 to 27 days of age reduced carcass fat and heterophil:lymphocyte ratios, and increased immune organ weight, antibody titer to sheep red blood cell (SRBC) antigen and livability than ad libitum fed birds. Body weights were similar by 56 days of age, and there was sexual dimorphism for rate of accelerated growth. Long term obesity, but not short term weight gain, was detrimental to reproductive performance, feed utilization, response to SRBC, and resistance to Escherichia coli, lymphoid leukosis and livability of broiler breeder dams. Poorer quality crumbles also reduced reproductive performance. An association between an endogenous viral gene encoding for avian leukosis virus (ev21) and the sex-linked K allele of the Z chromosome was confirmed in the broiler genome. Reproductive performance and feed utilization were inferior for K/- than k⁺/-, notwithstanding a pleiotropic effect of K associated with heavier egg and embryo weights. Variation in residual feed consumption was influenced by feathering genotypes and management practices. Increases in hatchability for the initial period after onset of lay were due to a reduction in early embryo deaths. Egg and 18-day embryo weights, ratios of embryo:egg and yolk:albumen, and proficiency of lipid transfer also increased but the latter was not associated with higher hatchability. Selection for 56-day body weight resulted in a divergence between lines at 21 days of age of 404% for body weight, 279% for feed intake and 138% for feed conversion ratio. Genotype by feeding regimen interactions were observed for growth and appetite development. Early posthatch growth of small intestine was highly correlated with subsequent growth of demand organs. Selection had also resulted in correlated changes in cell size of muscles, but not liver or small intestine which increased in size due to cell hyperplasia. Correlated changes in feed intake mediated synthesis and secretion of digestive enzymes. / Ph. D.

Like most agricultural production systems, effective decision making in turkey production systems requires the prediction of future status of the system and evaluation of alternative management policies. A simulation model of a turkey production system was developed to predict values of flock performance indicators of significant economic importance, namely body weight and feed consumption. Existing weather simulation models were combined and modified in order to develop a model that predicted daily dry-bulb temperature and humidity ratio outside the turkey house. The weather simulation model was validated using twenty years of daily observed weather data from Roanoke, Virginia. Thermal environment inside the turkey house was predicted from simulated outdoor weather using energy and mass balance equations. House environment prediction part of the model was validated using observed inside and outside temperature data collected at a turkey farm in Virginia. A discrete event simulation model was developed to simulate the effects of house thermal environment, feed energy, sex, and age on weight gain and feed consumption of growing turkeys. The model was validated using temperature, body weight, and feed consumption data collected at a turkey farm in Virginia. The observed average bird weights at marketing age were within 95% confidence intervals of the predicted values. However, the model underpredicted energy consumption values. The sensitivity of the model to variations in R-value, ventilation rate, and feed energy concentration was evaluated. The model was more sensitive to feed energy concentration. / Ph. D.

No description available.

Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: South Africa, like many other developing countries throughout the world, has a rapidly growing human population, resulting in a consequent increased demand for food. Ironically, this increased food supply has to be produced on a smaller area of available agricultural land, which means that agricultural production processes have to become more efficient. Furthermore, the majority of the people in these countries are unschooled and poverty is a common phenomenon. Therefore, animal scientists are faced with the challenge and the responsibility to provide affordable, high quality food to these people. One way of reaching this objective is to improve the utilisation of low-quality, high roughage feedstuffs like crop residues and dry natural grass pastures. In the winter rainfall area of South Africa alone, about 460 000 ha of wheat straw are annually available. The ruminant animal has the ability to utilise the relatively unavailable energy (cellulose, hemi-cellulose and pectin) in the fibre component of these low-quality forages. Unfortunately, various factors, of which a N deficiency is the pre-dominant one, limit the utilisation of these feedstuffs. If the ability of the ruminant to utilise low-quality, fibrous energy sources is improved, these abundantly available and relatively inexpensive crop residues and natural pastures can be converted into high quality protein food for human consumption. Therefore, in order to rectify the N deficiency caused by these low-quality forages, the supplemental N requirement to optimise the fermentation and digestive processes of the ruminant animal has to be determined. The first study was conducted to determine the supplemental rumen degradable protein (RDP) requirement, to maximise the digestible organic matter intake (DOMI) of Dohne Merino sheep fed wheat straw. Keeping the high cost of natural protein supplementation in mind, the purpose of the second study was to determine the amount of true protein that can be replaced by nonprotein nitrogen (NPN) in RDP supplements fed to Dohne Merino sheep consuming wheat straw. In both trials animals had ad libitum access to low-quality wheat straw (3.2% CP; 74.2% NDF) and water. In the first trial, RDP (calsium caseinate: 90% CP; 100% rumen degradable) was intraruminally administered at 07hOOand 19hOO,at the following levels: 0, 40,80, 120 and 160 gld. Intake, fermentation and digestion were monitored to determine the RDP requirement to maximise DOM!. Digestible organic matter (OM) intake displayed a quadratic increase with elevated amounts of RDP (P < .01), and was maximised at an estimated 3.15 g RDPlkg BW·75 or 11.6% of DOM. Forage OM intake tended to increase quadratically (P = .15) with higher RDP levels. Microbial nitrogen (MN) flow to the duodenum and microbial efficiency increased quadratically (P ~ .04) and fluid dilution rate tended to increase in a quadratic manner (P = .15) with increased RDP supplementation levels. Rumina! ammonia nitrogen (NH3-N) and total volatile fatty acid (VFA) concentrations increased linearly (P ~ .07), while rumen pH exhibited a variable response to increased RDP levels (cubic; P = .08). Increasing RDP supplementation to Dohne Merino wethers consuming wheat straw, generally enhanced forage utilisation and DOM!. In the second trial, urea replaced different levels of casein N on an isonitrogenous basis, ranging from 0 - 100%. Since true protein is much more expensive than urea, the purpose of this study was to determine the maximum natural protein level that can be replaced by urea in RDP supplements, without adversely affecting intake and/or fermentation and digestive processes. The control treatment provided all of the RDP in the form of calcium caseinate (90% CP; 100% rumen degradable). The percentages of supplemental RDP from urea in the other treatments were 25, 50, 75 and 100%. The 100% urea treatment was balanced with maize starch to contain 40% CP and all other treatments received the same amount (150 gld) of starch. Intake of forage OM showed a weak decreasing trend (linear; P = .16) with increasing urea levels. Ruminal digestibilities of OM and NDF were not affected (P ;;::.:18) by urea level. Increasing urea levels resulted in linearly reduced total tract OM and NDF digestibilities (P ~ .10). As a result, DOMI declined (linear; P < .01) with increasing proportions of urea. Effects of increasing urea proportions on duodenal N flow, microbial efficiency and fluid dilution rate were minimal. Ruminal NH3-N tended to increase quadratically with increasing urea levels (P = .l4). Total VFA concentration decreased linearly (P = .03), while rumen pH increased in a linear manner (P = .08) with increasing urea proportions. Branched-chain volatile fatty acids (BCVFA's) and valerate decreased linearly (P ~ .05) with increasing urea levels, while other VFA's and the acetate:propionate ratio were generally not affected by treatment (P ;;:::.16). It appears as though ruminal and total tract OM and NDF digestibility criteria, as well as DOMI reached maximum values at substituting 25% of casein for urea. It is therefore concluded that replacing 25% of casein with urea in RDP supplements, will maintain effective utilisation of low-quality forages by sheep. / AFRIKAANSE OPSOMMING: Ontwikkelende lande, insluitend Suid-Afrika, word gekenmerk deur 'n vmmge bevolkingsaanwas. Dit lei tot 'n verhoogde vraag na voedsel, wat op 'n gevolglik kleinerwordende beskikbare kommersiële lanbbou-area geproduseer moet word. Die doeltreffendheid van produksieprosesse in die landbousektor moet dus noodgedwonge verbeter word. Die oorgrootte meerderheid van die bevolkings in ontwikkelende lande is ongeletterd en armoede en hongersnood is soms 'n algemene verskynsel. Veekundiges word dus gekonfronteer met die uitdaging en verantwoordelikheid om bekostigbare, hoë kwaliteit voedsel aan hierdie mense te voorsien. Een van die mees doeltreffende metodes om hierdie probleem aan te spreek, is om die benutting van lae kwaliteit, hoë-vesel voerbronne, bv. oesreste en droë grasweidings te verhoog. In die winterreënstreek van Suid-Afrika alleen, is 460 000 ha koringstrooi jaarliks beskikbaar. Herkouers beskik oor die besondere vermoë om die relatief onbeskikbare energie (sellulose, hemi-sellulose en pektien) in die veselkomponent van hierdie lae kwaliteit voere te benut. Verskeie faktore, waarvan 'n N-tekort die mees prominente is, beperk egter die benutting van hierdie voerbronne. Die uitdaging is dus om die herkouer se vermoë om hierdie voere te benut, te optimaliseer. Sodoende word 'n geredelik beskikbare, onderbenutte en relatief goedkoop voerbron omgeskakel in hoë kwaliteit proteïen vir menslike gebruik. Die N-aanvullingsbehoefte om die fermentasie- en verteringsprosesse van die herkouerdier te optimaliseer moet dus bepaal word, sodat die N-tekort in herkouers, wat soortgelyke weidings benut, reggestel kan word. Gevolglik was die doel met die eerste proef om die behoefte aan rumen degradeerbare proteïen-(RDP)-aanvulling, vir die maksimum inname van verteerbare organiese materiaal (VOM) van Dohne Merino skape wat koringstrooi ontvang, te bepaal. Weens die hoë koste van natuurlike proteïenaanvulling, was die doel met die tweede proef om die hoeveelheid ware proteïen in RDP-aanvullings, vir Dohne Merino skape wat koringstrooi ontvang, wat met nie-proteïen stikstof (NPN) vervang kan word, te bepaal. In beide eksperimente het die diere ad libitum toegang tot koringstrooi (3.2% RP; 74.2% NBV) en water gehad. In die eerste proefis RDP (kalsiumkaseïnaat; 90% RP; 100% rumen degradeerbaar) teen 07hOOen 19hOOintraruminaal toegedien, teen die volgende peile: 0, 40, 80, 120 en 160 gld. Inname, fermentasie en vertering is gemonitor om die RDP behoefte vir die maksimum inname van VOM te bepaal. Verteerbare OM-inname het 'n stygende kwadratiese tendens (P < .01) getoon met verhoogde RDP-peile en het 'n maksimum bereik by 'n aanvullingspeil van 3.15 g RDPlkg metaboliese liggaamsmassa (LM·75 ) of 11.6% van VOM. Organiese materiaalinname vanaf koringstrooi het geneig om kwadraties toe te neem (P = .15) met verhoogde RDP-peile. Mikrobiese stikstof-(MN)-vloei na die duodenum en mikrobiese effektiwiteit het kwadraties toegeneem (P :::;.;04) en vloeistof deurvloeitempo het 'n neiging vir 'n kwadratiese toename (P = .15) met verhoogde RDPpeile getoon. Rumen-ammoniakstikstof (NH3-N) en vlugtige vetsuur-(VVS)-konsentrasies het lineêr toegeneem (P :::;.;07), terwyl rumen pH 'n wisselende reaksie (kubies; P = .08) met stygende RDP-peile getoon het. Verteerbare OM-inname en benutting van koringstrooi is verbeter deur stygende peile van RDP aanvulling by Dohne Merino hamels. In die tweede proef is kaseïen op 'n iso-stikstof basis met verskillende ureumpeile, vanaf o - 100%, vervang. Omdat ureum baie goedkoper is as natuurlike proteïen, was die doel van die tweede proef om die hoeveelheid natuurlike proteïen in RDP-aanvullings te bepaal wat met ureum vervang kan word, sonder om inname, fermentasie en vertering te benadeel. Die kontrolebehandeling het 100% van die RDP in die vorm van kalsiumkaseïnaat (90% RP; 100% rumen degradeerbaar) voorsien, terwyl ureum in die ander behandelings onderskeidelik 25, 50, 75 en 100% van die kaseïen-N vervang het. Die 100% ureumbehandeling is met mieliestysel tot 40% RP gebalanseer en dieselfde hoeveelheid stysel (150 gld) is by al die ander behandelings ingesluit, om moontlike effekte van stysel op rumenfermentasie te elimineer. Organiese materiaalinname vanafkoringstrooi het 'n swak dalende tendens getoon met stygende ureum insluitingsvlakke (lineêr; P = .16). Rumenverteerbaarheid van OM en neutraal bestande vesel (NBV) is nie deur die ureumpeil beïnvloed nie (P ;;:: .18). Toenemende ureumpeile het gelei tot 'n lineêre afname in totale kanaal OM en NBVverteerbaarheid (P ~ .10). Gevolglik het VOM inname lineêr afgeneem (P < .01) met stygende ureum insluitingspeile. Die effek van behandeling op duodenale N-vloei, mikrobiese effektiwiteit en vloeistof deurvloeitempo was minimaal. Rumenammoniakstikstof-( NH3-N)-konsentrasie het 'n stygende kwadratiese tendens getoon (P = .14) met toenemende ureum peile. Totale vlugtige vetsuur-(VVS)-konsentrasies het lineêr gedaal (P = .03), terwyl rumen pH lineêr toegeneem het (P = .08) met stygende ureum insluitingsvlakke. Vertakte ketting VVS' e en valeriaansuurkonsentrasies het lineêr gedaal (P ~ .05) met stygende ureumpeile, terwyl die ander VVS' e en die asynsuur:propioonsuurverhouding oor die algemeen nie deur behandeling beïnvloed N; nie (P ;;:: .16). Dit blyk asof VOM inname, sowel as rumen- en totale kanaal verteerbaarheidsmaatstawwe, by 25% vervanging van kaseïen-N met ureum-N 'n maksimum bereik het. Die gevolgtrekking is gemaak dat die doeltreffende benutting van lae kwaliteit ruvoere deur skape, gehandhaaf sal word deur 25% van die ware proteïen in RDP-aanvullings met ureum te vervang.