The evolution and application of enzymes in the animal feed industry: the role of data interpretation

ABSTRACT

1. Enzymes have been used commercially for nearly 40 years and save significant costs through sparing of expensive nutrients but the mechanism by which this is achieved is still debated.

2. The research focused on non-starch polysaccharidase (NSPase) enzymes is used as an example of where greater progress could have been made if the details of the work had been described more fully and the analysis of the data generated had been broader in scope and more critical.

3. Lack of standardisation of the details presented in the materials and methods has been identified as a significant barrier to meaningful retrospective analysis and thus limits advances in the understanding of the mode of action of these enzymes.

4. The identity of the enzyme employed and its activity is often lacking, and more importantly the purity is rarely disclosed. Contaminant activities which are neither listed nor assayed could play a significant role in the responses observed.

5. The dose optimum of most enzymes is often considerably higher than that employed in most studies. Thus studies claiming synergy between two ‘activities’ should ensure that the response is not related to each enzyme simply augmenting the dose of just one activity in the finished feed. This is a common problem, and coupled with the lack of factorial experiments to justify the presence of each enzyme in a multi-enzyme product, it is not surprising that there is still debate as to whether single or multi-enzymes are best suited poultry rations.

6. The three proposed mechanisms for NSPases (viscosity, cell wall and prebiotic) are discussed, and along with their strengths and weaknesses it is suggested that a re-evaluation of each is needed. Viscosity may have to be re-evaluated as being a function not only of the cereal being fed, but of the age of the animal as well. The cell wall theory as described is poorly modelled in vitro and hence the validity of these data is questioned. The prebiotic theory may need significant modification as it appears that the quantities of oligomers produced are insufficient to generate the additional volatile fatty acids (VFA)’s reported. It is likely that all three mechanisms play a role in the responses observed, but the prebiotic mechanism probably plays by far the most important part in low viscosity diets.

7. Future research would be improved if it considered all potential mechanisms when designing a trial. Significant failings are apparent as a result of adherence to tenets in explanation of the results. Most importantly, it should be emphasised that a hypothesis is there to be tested, not defended.     

A real-time polymerase chain reaction assay for the detection of the myxozoan parasite Henneguya ictaluri in channel catfish

Proliferative gill disease (PGD), caused by the myxozoan parasite Henneguya ictaluri, is the most prevalent parasitic infection affecting commercial channel catfish (Ictalurus punctatus) aquaculture. There are currently no effective chemotherapeutic or biological control measures for PGD, which often peaks during the spring and fall when water temperatures are between 16-25 degrees C. The current diagnostic techniques of gross examination of gill clip wet mounts and histopathology are subject to false-negatives during the early stages of infection, and the quantifiable nature of end-point polymerase chain reaction (PCR) is subjective. Consequently, a rapid and more sensitive quantitative real-time PCR assay was developed for the detection of H. ictaluri during the early stages of infection in channel catfish. A 23 base-pair TaqMan probe was designed based on previously published H. ictaluri PCR protocols. The sensitivity of the assay was the equivalent of a single H. ictaluri actinospore, and in a pond challenge study, quantitative real-time PCR proved to be more sensitive than gross examination, microscopic examination of gill clip wet mounts, and histopathologic examination of gill tissue sections. Future applications of this assay will focus on developing methodologies to be used in conjunction with current pond-monitoring protocols to evaluate potential treatments and better manage this significant seasonal disease.     

Chemotherapy and radiotherapy for treatment of cutaneous lymphoma in a ground cuscus (Phalanger gymnotis)

A 15-year-old female ground cuscus (Phalanger gymnotis) was presented with an isolated ulcerated, nonhealing lesion on the lateral thorax. Histopathology and immunohistochemistry were diagnostic for cutaneous T-cell lymphoma with incomplete excision. Oral chemotherapy with CCNU (lomustine) resulted in clinical remission that lasted 255 days, with no appreciable toxicity. Tumor recurrence was treated with radiation therapy, which resulted in 120 additional days of clinical remission. Subsequently, the tumor developed at a distant site and the cuscus was humanely euthanized. A slight decrease in appetite early in disease progression was the only adverse effect noted throughout the treatment period. Oral, minimally invasive chemotherapy, and adjunct radiation therapy were viable treatment options for this ground cuscus and should be considered for treatment of neoplasia in other nontraditional species.     

Immunofluorescence studies of renal basement membranes in dogs with spontaneous diabetes

Renal tissue from 12 dogs with spontaneous diabetes and 16 control dogs were studied by light, immunofluorescence, and electron microscopies. Significant linear staining for immunoglobulin G and albumin were observed in the glomerular and tubular basement membranes of dogs with spontaneous diabetes--similar to that observed in human diabetes. On immunohistochemical grounds, it would appear that the dog with spontaneous diabetes is an appropriate model of diabetes in persons.     

IRIDIUM-192: A LITERATURE REVIEW FOR FURTHER REFERENCING THE ISOTOPE, ITS ACTIVITY UNITS, AND DOSIMETRY TECHNIQUES

The individual embarking on an iridium-192 brachytherapy program is faced with an abundance of concepts, terms and dosimetry techniques. This article introduces the beginning brachytherapist to the basic physical parameters of iridium-192, to the potential units for source strength and to the general concepts of the various dosimetry techniques. Multiple literature references are listed for more in-depth study.     

Accuracy of heart rate obtained by auscultation in atrial fibrillation

The accuracy of heart rate estimation by cardiac auscultation over a 15-second period, and the influence of clinical experience on accuracy were evaluated in a dog with chronic atrial fibrillation by test subjects of varying experience. Only 30% of all test subjects provided accurate heart rate estimates. Board-certified specialists, medicine residents, and experienced nurses were significantly more accurate in their estimates than surgery residents and students. Accurate estimates were provided by 12.5% of surgery residents and students, as opposed to 64% of the other test subjects. Auscultatory estimates of heart rate in atrial fibrillation may be significantly inaccurate, and under some circumstances they may not provide a sound basis for making clinical decisions.     

Fluoroscopic and endoscopic localization of an esophagobronchial fistula in a dog

A 10-month-old, intact male Chihuahua presented for a 7-month history of regurgitation and coughing. Survey radiographs revealed a soft-tissue opacity within the distal esophagus. A contrast study confirmed the presence of an esophagobronchial fistula. Endoscopic removal of foreign material within the esophagus allowed for visualization of an esophageal diverticulum. Bronchoscopic examination revealed the presence of an abnormal opening in a right caudal tertiary bronchus. Passage of a cardiac guidewire was accomplished, confirming the presence of the fistula and aiding its subsequent surgical removal.     

Current status of cattle production system in Nyagatare District-Rwanda

A study was conducted to characterize the cattle production systems in Nyagatare District, Eastern Province of Rwanda using pre-tested questionnaires, interviews with key informants as well as focus group discussions in a period of 2 months. The respondents were selected by multi-stage sampling at sector and cell levels. Based on the procedure of Krejcie and Morgan (Educational and Psychological Measurement 30:607–610, 1970) to determine the overall sample size, the result indicated that the majority (98.3%) of farms were privately owned by large families of five to seven members, and most farmers (53.9%) had only primary education. Most respondents (52.6%) were in the age bracket of 41–50 years and were mainly (48.3%) located within 3 km from trading centers. The farm size averaged 6.5 ± 0.8 ha and most farms (64.7%) were fenced except in Rukomo Sector (50%) where zero grazing prevailed. Natural pastures (savanna grass land) were the main feed resource; tethering (9%) and communal grazing had diminished. Napier grass was the main planted forage (93.2%), followed by Chloris guyana (3.1%) and Brachiara (1.2%). Leguminous forages were rarely (2.5%) reported. Vita-mineral and salt block supplements, hay, and crop residues were the predominant supplementary feed stuffs used except in Karangazi and Rwemiyaga Sectors where only vita-mineral block predominated. However, maize and rice brans were reported to be the main feed stuffs used in supplementary feeding of lactating cows. Most farmers (89.7%) reported shortage of water as most of the farmers trekked their cattle to the nearest valley dams (59.2%), rivers (21.1%), and a few 6% had water on farms. Indigenous cattle were predominant (67.03%) followed by cross-breeds (28.37%) and exotics (4.6%) while all farmers kept small ruminants. Natural breeding predominated (74.9%) and most farms (60.6%) had animal houses most of which were temporary (52.8%). The reported mean age at first calving (AFC) was highest (40.2 ± .33) for Ankole and the lowest (29.1 ± .50) months for exotic cattle. Calving interval was shorter in local breeds than 65.7 ± 3.0 in exotic. The mean dairy milk yield was lowest for Ankole cattle 2.4 ± .08 as compared to the exotics (10.42 ± .36) and their crosses (7.2 ± .34). The main challenges were diseases, shortage of water, feeds, and inadequate extension services. Same observation was reported by Okello (African Journal of Range and Forage Science 22(3), 2005) in Uganda.