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Two experiments were conducted to study the utilization of poor quality hay by ruminants. In the first experiment, several nitrogen supplements were compared under practical conditions when fed to stocker cattle receiving a hay diet. Sixty cattle were wintered on fescue hay with one of five supplements: 1) none, 2) liquid urea-molasses supplement injected into the bales, 3) liquid-supplement self-fed in lick-tank, 4) mixture of deep-stacked broiler litter and ground corn grain and 5) soybean meal. Preliminary observations showed that the liquid supplement injected into bales was poorly distributed. Highest daily weight gains were for the animals supplemented with urea-molasses self-fed, litter or soybean meal. Compensatory gains under spring-grazing conditions subsequently suppressed these differences. Feed intake was low for all treatments. Feed efficiency was best for the soybean-meal group but feed cost per unit of gain was lowest for the broiler litter supplemented group. In a second experiment, urea and carbohydrates were supplemented to a fescue hay diet fed to lambs cannulated at the rumen, abomasum and ileum. The treatment diets were: 1) hay, alone or supplemented with 2) urea, 3) urea and molasses and 4) urea and corn. Chromic oxide and Co-EDTA were used as markers. Urea supplementation improved N retention but did not affect DM, ADF and energy digestibilities. The extent and efficiency of rumen fermentations were low, with a high methane production. Supplementation did not significantly affect the partition of digestion of DM and N along the gastro-intestinal tract. ADF digestion in the large intestine was increased by urea supplementation. Mean retention time of food along the gastro-intestinal tract was similar among treatments. / M.S.

The objective of this study was to examine the use of technical indicators, in an econometric context, as guides in making pricing decisions relative to feeder cattle production. Technical indicators were developed for both the short and long term. Short term indicators were designed to capture divergence/convergence between the Relative Strength Index and the futures price stream to form the Price Linked to Divergence index. A long term indicator using an average difference in price over a longer period was developed to form the Price Linked to Trend index. These indicators were used in the econometric models which in conjunction with cash production costs formed a hold/price/sell decision framework. Analysis was conducted on fall-to-spring, spring-to-fall, and fall-to-fall production programs. Results for the three production programs in both the in and out-of-sample environments showed that on average a futures price in the top half of the futures price range was captured. This resulted in average improvement in returns through hedging for every program. / Master of Science

Influence of light, dietary amino acid levels, feeding space, and ambient temperature on male broiler body weight, feed efficiency, percentage abdominal fat, and incidence and severity of leg abnormalities was studied in two experiments. Broilers subjected to intermittent light (1 hr on:2 hrs off) had heavier 49 day body weights, and similar feed efficiencies than birds given continuous illumination. Feeding high [106 and 114% of NRC for lysine and total sulfur amino acids (TSAA), respectively] versus low (100% of NRC for lysine and TSAA) amino acid diets, improved body weight and feed efficiency at market age. Providing broilers with increased feeding space (from 1.47 to 2.94 cm/bd) resulted in improved body weight at market age. Birds under high ambient temperatures (29 to 26° C) had significantly higher feed efficiencies at four weeks of age than those given low temperatures (29 to 18° C). However, at market age broilers provided low temperatures had significantly greater gains with similar feed efficiencies. Birds fed high amino acid diets had significantly more abdominal fat than those given low amino acid diets. Light, feeding space, ambient temperature and relative humidity had no significant effect on percentage abdominal fat. Broilers provided intermittent light had significantly fewer and less severe leg abnormalities than birds under continuous illumination. Dietary amino acids, ambient temperature and relative humidity had no significant effect on the incidence or severity of the leg disorders. / Master of Science

Four experiments were conducted to compare adipocyte dynamics and body composition among adult chickens from lines differing in growth rate and feed consumption. In Experiment I, forced caloric overconsumption increased weight gain and fat deposition, with concomitant increases in the total adipocyte DNA content of the assayed fat depots. Injections of DNA-specific [methyl³H] thymidine resulted in higher radioactivity levels in the fat depots of forced versus ad libitum or restricted-fed birds. Evidently, stimulation of fat deposition in adult chickens can be associated with adipocyte hyperplasia. A second experiment was conducted to histologically examine the effects of forced caloric overconsumption on adipocyte size, number, and distribution in the retroperitoneal fat depot of adult weight-line birds. Similarly to Experiment I, force feeding increased fat deposition, resulting in increases in the retroperitoneal fat depot total adipocyte DNA content. The lipid/adipocyte DNA ratio also decreased during rapid depot expansion. This resulted in an increase in the small adipocyte population of the force fed birds when adipocyte diameter was increasing. Subsequently, when the constraints of force feeding were removed, adipose depot reduction occurred, with the mobilization of lipid from small as well as large adipocytes. In a third experiment, the effects of estrogen administration and partial lipectomy were examined. In addition to the weight-line birds, a commercial broiler breeder stock was utilized. Estrogen administration depressed body weight gain and abdominal fat deposition when compared to placebo implanted birds. Partial lipectomy depressed body weight, fat deposition, and abdominal fat total adipocyte DNA content. Lipectomy modified several components of carcass composition without altering feed intake. No indication of a compensatory hyperplastic response to lipectomy was indicated. A final experiment was conducted examining the effects of forced body weight fluctuations on body composition of male and females from the weight-selected lines. Although numerous first-order interactions were detected, force-feeding resulted in transient modifications in carcass composition and fat deposition which were more apparent in the high than low weight line, in females than males. After release to ad Iibitum feeding, the differences resulting from force feeding were reduced. / Ph. D. / incomplete_metadata

Three balance experiments were conducted to determine the effects of dietary fiber on mineral balance and intestinal.morphology of growing pigs. Fiber sources were added to corn-soybean meal diets at levels which increased neutral-detergent fiber levels by 6 to 8%. In experiment 1, 10% oat hulls (OH) decreased Ca (P<.06) and Zn (P<.01) balances of pigs after a 7 d feeding period. Wheat bran (20%) increased Mg intake and balance (P<.02), but did not affect Ca and Zn balances. In experiment 2, pigs were fed diets (with or without supplements of Zn, Fe and Mg) containing 15% OH or soybean hulls (SH) for 5 d or 26 d. SH increased Fe intake and balance (P<.01) and ( Mg absorption (P<.01). Compared with balances at 5 d, Zn balance was similar, while Fe and Mg balances were higher at 26 d for pigs fed the basal (P<.05) or SH (P<.01) diets. However, Zn balance was lower (P<.05) at 26 d 1 but Fe balance did not change over time for pigs fed the OH diets. At each time period, Zn balance was not different between pigs fed the basal or high-fiber diets. In experiment 3, Ca, Zn and Mg absorption were not affected by 15% OH or SH or 20% alfalfa meal (AM) after 67 d or 39 d, although SH and AM increased Fe balance (P<.01). Intestinal surface morphology of 12 pigs fed in experiment 3 was examined by scanning electron microscopy. Villus morphology was variable in jejunum, ileum and colon, although evidence of villus blunting and folding accompanied by erosion of microvilli and loss of epithelial cells was observed in small intestine of some pigs fed the SH and AM diets. Damage was not consistent in all sites examined in individual pigs, and did not occur in all pigs fed any specific diets. Although Ca and Zn balances were decreased by OH in two of the balance trials, the inability of OH to consistently decrease mineral balance suggests that the ability of the pig to adapt to different diets may be sufficient to overcome the mild inhibitory effect on mineral absorption of some fiber sources. When viewed together, the results of the balance trials indicate that moderate amounts of dietary fiber have a minimal negative impact on mineral balance of pigs fed practical corn-soybean meal diets. However, the results also indicate that fiber sources such as SH and AM, are rich sources of some minerals for the pig, particularly Fe. Evidence of intestinal damage was evident in pigs fed the high-fiber diets. However, not all animals fed a particular diet were affected, which suggests that some pigs within a given population may be susceptible to detrimental effects of dietary fiber on intestinal structure or function. / Ph. D.

Determining the energy values of feed ingredients for poultry is of great concern, especially since production efficiency is associated with profit margins. Therefore, accurate, precise, and reproducible energy values for feed ingredients are of the utmost importance in formulating an economical diet. An important aspect in determining the apparent metabolizable energy (AME) of a feed ingredient is the procedure employed in the drying of excreta samples. During sample preparation, substantial grinding losses were incurred amounting to 3.5 to 5.2% of the dried sample weight. Also moisture uptake during sample grinding accounted for a 1.9 to 3.9% increase in sample weight. To properly account for such losses, freshly collected excreta samples should be weighed, oven-dried at 40 C, reweighed, allowed to equilibrate with atmospheric moisture, weighed, ground, reweighed, and stored in air-tight containers for subsequent analyses. From the oven-drying of feed and excreta samples at various temperatures, a linear decrease in sample weight occurred with increasing drying temperatures. When dried at 100 C or less, the energy content of feed and excreta samples remained unchanged, but increased significantly at higher temperatures. The nitrogen composition of feed and excreta samples exhibited a similar trend, but a significant loss of excreta nitrogen (2%) occurred at 100 C. The loss of excreta nitrogen at a temperature of 100 C is of relatively minor consequence in the determination of metabolizable dry matter, but is of major concern in nitrogen balance studies. Extraction of feed and excreta samples with N,N-dimethylformamide and titration with Karl Fischer reagent indicated that significant amounts of water were retained by samples dried at 40, 60, and 80 C. However, at temperatures of 100 C or greater, little water was retained but sample decomposition occurred. A drying temperature of 90 C or the Karl Fischer method may yield a more accurate value for the dry matter of feed or excreta. When seven roosters were subjected to a total collection method for five consecutive days, individual birds were better metabolizers of dry matter and energy than others. By either a voluntary intake method or by a total collection method, values for the nitrogen-corrected metabolizable energy of corn were similar. The total collection method proved to be more reliable since it provided the least amount of variation when <u>ad libitum</u> feed intake and total excreta output were measured over a period of several days. In past experiments, adding fats to a test diet at the expense of cerelose in amounts no greater than 20% of the diet to determine the metabolizable energy of the fat has been associated with a high degree of variability. From the force-feeding of fats at levels to 100%, the variation associated with the metabolizable energy value of a fat was greatly reduced. The methodology presented here provided reliable estimates and detected differences between the metabolizable energy of two feed-grade fats in comparison to previous methods. / Ph. D. / incomplete_metadata

Experiments were conducted to investigate the effects of E. coli and rotavirus as causative agents in producing infectious stunting syndrome of poults. The syndrome, as it occurs commercially, was characterized in two experiments to produce decreased digestible dry matter and nitrogen as well as increased excreta nitrogen and gross energy content of affected poults. The effects of E. coli and rotavirus on the nutritional performance of poults were compared to the commercial syndrome by digestibility trials and assay of intestinal mucosaI enzyme activities. The strain of E. coli used in these experiments was isolated from the yolk sac of stunted poults. Inoculation of day-old poults was done orally in one experiment and via the yolk sac in another series of experiments. Experiments were designed in a factorial arrangement of E. coli inoculation and dietary protein level (28 vs. 22%). Oral administration of the pathogenic E. coli at a low dose (.1 ml of a 10⁻² dilution of a 24-hr culture) to day-old poults produced a significant increase in feed efficiency by 21 days of age for birds fed either 28 or 22°0 protein diets. In this case, E. coli apparently was established as part of the normal intestinal microflora of the turkey without producing a toxic response. Similar concentrations of E. coli (10⁻³ and 10⁻² dilutions) inoculated into the yolk sac of day-old poults resulted in significant mortality and morbidity. The lower dilution (10⁻³) produced the desired response of stunted poults without substantial mortality. Body weight gain and feed consumption were severely decreased by E. coli inoculation at both levels of protein (28 or 22%). The 28% protein diet alleviated the reduction in feed consumption for birds infected with the lower concentration of E. coli. The 10⁻² dilution caused substantial mortality and similar responses on body weight at both levels of protein. A malabsorption of nutrients accompanied E. coli infection in spite of reduced feed consumption as indicated by increased excreta nitrogen and gross energy content for all infected poults. In three experiments, rotavirus was orally inoculated into poults over 21 days of age previously fed either 28 or 22% protein diets. The response of rotavirus was variable in the three experiments, however, the low protein diet (22%) increased the poults susceptibility to rotavirus infection. Serum antibodies to rotavirus were detected in all poults tested prior to inoculation. Ubiquitous in nature, rotavirus appears to produce clinical signs of infection in combination with stress on the poults. Effects of rotavirus on digestibility parameters were inconclusive. In experiments with either rotavirus or E. coli, activities of intestinal mucosal enzymes were found to vary more between poults within a treatment than by any effect of the various treatments. / Ph. D.

Two feeding trials were conducted involving diets supplemented with soybean meal, dried brewers, and wet brewers grains. The first trial involved 24 first-calf heifers averaging 82 d postpartum. After a 20 d protein depletion period in which a 9.4% CP diet was fed, cows were randomly assigned to a 2 x 3 factorial where pelleted (P) or unpelleted (UP) soybean meal supplemented corn diets to 12.2% (L), 15.4% (M), and 18.1% (H) crude protein. During depletion, milk production, dry matter intake, and yields of milk protein, fat, and solids decreased in the range of 15 to 25%. However, these all increased to pre-depletion levels after 26 d of repletion. Considering repletion response separately resulted in no significant differences between P and UP for milk production and constituents, feed intake, and plasma urea. However, using depletion to covariably adjust means resulted in P diets favoring greater milk production (P < .01) than UP as well as protein, fat, and solid yields. This response may be caused by a significant increase in feed intake for P diets. Use of a depletion period did increase precision of results but its use in practical feeding trials is controversial. Results in milk, milk protein, fat, and solid yields, and plasma urea were linear with protein level (L vs H). The second trial involved 44 multiparous cows averaging 114 d postpartum. Eight cows remained on a control (CON) diet of 11.7% CP while all others were randomly assigned in a 3 x 3 factorial in which dried (DBG) and wet brewers grains (WBG), and soybean meal (SBM) supplemented the CON to 14.8 (L), 16.3 (M), and 18.0% (H) CP. Diet composition varied in corn silage and ensiled ground-corn but alfalfa silage was constant on a dry matter basis. All diets were superior to CON in milk production and constituent yield. Brewers diets were superior to SBM for milk yield, protein, and solid yields. Part of this response may be related to superior intake for diets containing brewers and lower rumen ammonia and plasma urea. Cows receiving brewers diets have higher intakes than SBM and brewers appear to be utilized more efficiently. For mid-lactating cows an increase in milk at 18.0% CP resulted from brewers diets but not SBM. The H level resulted in a significant increase in milk yield and protein (kg) but also had the highest plasma urea and rumen ammonia level. / M.S.

Thesis (MScAgric) -- Stellenbosch University, 2004. / ENGLISH ABSTRACT: The ruminant has the ability to utilize forages more efficiently than any other production animal. The utilization of forage fibre is an important aspect of ruminant production systems, as this is the main source of energy available to the animal. The availability of high-fibre forage nutrients is, however, restricted by cell wall degradability, and since low quality forages contribute a great deal to ruminant production systems worldwide, the improvement of this degradation process is of major economic importance. The use of exogenous fibre degrading enzymes has been proposed as a means of enhancing this process, with positive results being obtained from in vitro studies incorporating exogenous enzyme preparations. Positive in vivo results with regard to forage digestibility and other animal production parameters have consequently also been obtained following the addition of exogenous fibre-degrading enzyme preparations to the ruminant diet. Two initial screening experiments were undertaken in order to identify fungal enzyme preparations that may have a positive effect on in vitro fibre degradability. The initial screening employed an in vitro organic matter digestibility technique, and was successful in identifying at least six enzyme preparations displaying enhanced digestibility results that were statistically significant. A second in vitro gas production procedure was used to confirm results obtained from organic matter digestibility assays, as well as to increase screening capacity in order to evaluate new enzyme preparations more time-efficiently. Statistical analysis of results obtained from the secondary screening identified various enzyme candidates producing promising results. Only one of these, Abo 374, proved to be statistically superior to the control and other enzyme preparations. A growth trial was subsequently conducted to assess the performance of this enzyme in vivo. The trial involved individual feeding of 32 Dohne Merino ram lambs grouped according to weights into four groups consisting of 8 lambs each. Each group represented a specific application level of enzyme to the wheat straw component of a high fibre diet, amounting to 10, 5, or 1 ml enzyme supematant/kg straw. The enzyme was diluted with water at appropriate rates to obtain an application rate of 300ml/kg straw. The fourth (control) group was treated with water at the same application rate. The trial was conducted over a period of six weeks, during which feed intakes, weekly weight gains, as well as feed conversion efficiencies were recorded. Results suggested significant weight gains in the high (10ml/kg) and medium (5ml/kg) treatment groups, indicated by a P-value of 0.04. Similarly, feed conversion efficiencies were improved for above-mentioned groups (P=0.05), while feed intakes did not differ significantly between the four experimental groups. / AFRIKAANSE OPSOMMING: Die herkouer besit die vermoee om ruvoere beter as enige ander produksiedier te kan benut. Die gebruik van ruvoervesel is 'n belangrike aspek van herkouer produksiesisteme, aangesien ruvoere die hoof bron van energie aan die herkouer verskaf. Die beskikbaarheid van hoe-vesel ruvoer nutriente word egter beperk deur die degradeerbaarheid van die selwand, en aangesien lae kwaliteit ruvoere 'n groot bydrae tot wereldwye herkouer-produksiesisteme maak, is die moontlike verbetering van hierdie degraderingsproses van groot ekonomiese belang. In 'n poging om hierdie verteringsproses te help bevoordeel, is die gebruik van eksogene veselverterende ensieme ondersoek, en positiewe resultate is verkry wanneer hierdie ensieme in in vitro studies gebruik is. Goeie verbeterings ten opsigte van ruvoer verteerbaarheid en ander diereproduksie parameters is ook verkry deur middel van in vivo studies waar eksogene ensieme by die ruvoer van herkouers gevoeg IS. Twee eksperimente is ondemeem in 'n poging om ensiempreparate wat 'n moontlike positiewe effek op in vitro veselvertering mag he, te identifiseer. Die eerste, 'n in vitro organiese materiaal verteerbaarheid tegniek, was suksesvol in die identifisering van minstens ses ensiem preparate wat statisties betekenisvolle verbeterings ten opsigte van verteringsresultate geproduseer het. 'n Tweede in vitro gasproduksie prosedure is vervolgens gebruik om resultate verkry vanaf die eerste tegniek, te bevestig, asook om evalueringskapasiteit te vergroot en sodoende, nuwe ensiempreparate meer tydseffektief te evalueer. Statistiese evaluering van resultate verkry uit die tweede in vitro tegniek het 'n reeks ensieme met positiewe resultate opgelewer. Een van hierdie, Ab0374, het statisties betekenisvolle resultate ten opsigte van die kontrole, sowel as ander ensieme getoon. In 'n volgende eksperiment is 'n groeiproef gedoen om die effektiwiteit van hierdie ensiem in vivo te toets. In die proef is 32 Dohne Merino ramlammers op grond van hul gewig in vier groepe van agt skape elk verdeel, en individueel gevoer. Die groepe het verskillende toedieningsvlakke van die toetsensiem, toegedien tot die koringstrooi komponent van 'n hoe-vesel dieet, ontvang. Toedieningsvlakke was 10, 5, of lml ensiemkonsentraat/kg strooi. Elke groep se ensiemkonsentraat is verdun met die toepaslike hoeveelheid water om 'n toedieningsvlak van 300ml ensiemoplossing/kg koringstrooi te verkry. 'n Vierde groep is behandel slegs met water teen dieselfde toedieningsvlak, en het gedien as 'n kontrole. Die eksperiment is oor 'n periode van 6 weke uitgevoer. Tydens die proeftydperk is voerinnames, weeklikse gewigstoenames, sowel as voeromsetverhoudings, gedokumenteer. Resultate het betekenisvolle gewigstoenames in die hoe (lOml/kg) en medium (5ml/kg) groepe opgelewer, aangedui deur 'n P-waarde van 0.04. Voeromsetverhoudinge het ook verbeteringe getoon vir bogenoemde twee groepe (P=0.05), terwyl voerinnames nie merkbaar tussen die vier groepe verskil het nie.