Growth pattern and reproduction in meat chicken female lines

Objectives

• To improve the understanding of ovarian growth mechanisms in the hen by examining the effects of growth factors using a tissue culture system designed to represent the growing ovary.
• To identify pathways that may be exploited to cause an improvement in reproductive efficiency of broiler hens.

Long-term selection for meat production has resulted in lower reproductive performance of broiler breeder females associated with disrupted ovarian function (larger number of ovarian follicles grow but fewer eggs are laid). This project sought to understand the physiology of this problem so that improvements to ovarian function can be made by physiological means, while leaving the large genetic gains in broiler breeder lines intact.

Research

An ovarian cell culture system was established, capable of measuring ovarian cell growth (as DNA synthesis). The effects of the growth factors IGF-1 and IGF-2 (insulin-like growth factors 1 and 2), EGF (epidermal growth factor), TGFa (transforming growth factor a ), FGF-1 and FGF-2 (fibroblast growth factors 1 and 2) and GH (growth hormone) on DNA synthesis of cultured ovarian (granulosa and thecal) cells was investigated. The growth effects of factors added individually and in combinations (IGF-1, TGFa and FGF2) were compared. An investigation of the IGF system was undertaken, particularly focussing on the presence, effects and purification of chicken ovarian IGF binding proteins (IGFBPs).

Outcomes

All tested growth factors stimulated growth of chicken ovarian cells, however the potency of each factor was different. GH had no direct effect on the growth of ovarian cells. Growth factor combinations were many times more potent than factors applied singly. Ovarian cells produce IGFBPs that can modify the actions of IGF-1 on these cells. IGF-1, in turn, can modify the production of IGFBPs by granulosa cells. Purification of ovarian IGFBPs was problematic.

Implications

Growth factors, including the IGFs, are potent stimulators of ovarian cell growth. The IGFs may mediate the actions of GH. Growth factor synergy indicates a complex mechanism for control of the growth of ovarian follicles. The existence of functional ovarian IGFBPs indicates the existence of an autocrine/paracrine IGF system which may be subject to artificial control by IGFBP-like compounds in vivo.

Publications

Researcher: Dr Jeff Downing and Dr Rhys D Roberts

Organisation: CSIRO Division of Animal Production, c/- Dept of Animal Science, University of Sydney, Werombi Road, CAMDEN NSW 2570

Contacts: Phone: (02) 4655 0600     Fax: (02) 4655 0693    E-mail jeffd@camden.usyd.edu.au

Factors influencing the nutritive value of lupins

Objectives

• To collect a range of samples of Lupinus angustifolius and Lupinus albus cultivars with associated information on growing conditions.
• To determine AME and analyse the composition of each sample.
• To examine the effects of dietary addition of hulls, soluble and insoluble non-starch polysaccharides (NSP) and oligosaccharides, and develop strategies to minimise any anti-nutritive effects.

Although lupins are widely used as a monogastric protein source, uncertainty surrounds the effects of high dietary levels of oligosaccharides and NSP, the value of additional processing such as de-hulling and the cost-effectiveness of enzyme products. Strategies to overcome these problems are needed in order that greater use can be made of lupins in broiler diets with anticipated reductions in feed costs.

Research

The nutritive values of Australian sweet lupin cultivar Gungurru and white lupin cultivar Kiev mutant were assessed in a series of apparent metabolisable energy studies on commercial broiler chickens housed in metabolism cages.

Outcomes

Modern cultivars of Australian lupins are valuable alternative sources of protein and energy for inclusion in broiler diets. Large differences in nutritive value due to species, season and locality were evident. The seed coats of these species do not contain anti-nutritive factors but did have an energy dilution effect. Feed enzyme products failed to yield consistent results in short-term AME studies on different breeds of broiler chickens in metabolism cages.

Implications

Wholeseed of Gungurru lupin can be included at 200 g/kg in a wheat-based diet and at 300 g/kg in a maize-based diet without deleterious effects on growth or feed efficiency. Excreta moisture is increased by inclusion of wholeseed of Gungurru lupin at 200 g/kg in wheat-based and maize-based diets. Enzyme technology for degrading lupin NSP and oligosaccharides needs development.

Publications

RIRDC Project No: DAS-10CM

Researcher: Mr Robert Hughes, Dr Robert van Barneveld, Mr Andreas Kocher and Dr Mingan Choct

Organisation: South Australian Research & Development Institute, Pig and Poultry Production Institute, University of  Adelaide, Roseworthy Campus,  ROSEWORTHY SA 5371

Contacts: Phone: (08) 8303 7788    Fax: (08) 8303 7977   E-mail: hughes.bob@pi.sa.gov.au

Epidemiological studies of Salmonella using serotyping, plasmid analysis, chromosomal and PCR analysis

Objectives

• To continue to monitor and type, by conventional serotyping and other typing methods, Salmonella isolates submitted by the poultry industry.
• To develop universal DNA based typing methods for Salmonella sub-typing.
• To survey genes that are implicated in the virulence of Salmonella in serovars of interest to the industry.

Salmonellosis associated with poultry is a problem worldwide for both producers and consumers. Salmonella are traditionally classified into serovars on the basis of the O and H antigens. It is necessary for the purposes of organism tracing and epidemiology to further subdivide Salmonella isolates. Classical methods, such as phage typing, though useful do not always give sufficient discrimination. This has lead to the development of molecular typing methods that are based upon DNA technology.

Salmonella Sofia represented over 78% of Salmonella isolated from chickens in 1995. Despite its widespread colonisation of chickens, it is rarely represented in the serovars isolated from humans. The conclusion is that Salmonella Sofia is not a significant pathogen for humans or chickens. This avirulence may be due to the absence of virulence genes. The DNA sequence data of these genes is available and can be used in PCR or other molecular methods to detect these genes and possibly explain the avirulence of S. Sofia.

Research

Serovars in poultry have not changed significantly in the past three years. S. Sofia continues to be the major isolate in commercial broiler flocks in Australia, but almost absent in the human population. There appears to be no reliable ‘universal’ method of molecular typing available at present. PFGE is rapidly becoming the method of choice in many laboratories, however it is of limited use in highly clonal serovars. Phage typing remains the technique of first choice for organism typing, however when interpreting results it must be remembered that bacterial populations are dynamic entities. The invH gene, and to a lesser extent other genes within the inv cluster, are often incomplete and may have some role in the avirulent phenotype of S. Sofia. The absence of spv plasmid borne genes in Sofia is universal. It is possible that a large plasmid in S. Sofia may exclude the acquisition of virulence factors from virulent serovars found in chickens.

Outcomes

• The continued monitoring of industry flocks over the past three years and organism tracing when outbreaks occur.
• Development of a number of molecular typing methods and a partial understanding of the significance of phage type conversion when tracing organisms.
• Partial explanation of the avirulence of S. Sofia.

Continued strong epidemiological and scientific evidence indicates that Salmonella Sofia, the most common Salmonella colonising meat chickens, is avirulent. The mechanism of this avirulence is unknown, but it may be a combination of a deficiency in one or more of the genes required for virulence. This evidence could be used in public awareness campaigns that S. Sofia is harmless and may be beneficial in excluding more virulent serovars. Continual monitoring of chicken flocks for changes in the distribution and serovar type provides clear evidence to the consumer that the industry takes the issue of product safety extremely seriously.

RIRDC Project No: IMVS-6CM

Researcher: Dr Michael W Heuzenroeder

Organisation: Institute of Medical & Veterinary Science, PO Box 14, Rundle Mall, ADELAIDE SA 5000
 

Contacts: Phone: (08) 8222 3275    Fax: (08) 8222 3543  E-mail: michael.heuzenroeder@imvs.sa.gov.au

Differentiation of virulent and avirulent Campylobacter jejuni and Campylobacter coli strains isolated from humans and chickens

Objectives

• To develop a rapid, simple detection method and an identification scheme for Campylobacter spp. of medical and veterinary importance.
• To develop methods to differentiate virulent from avirulent Campylobacter spp.
• To identify and replace strains potentially pathogenic to humans in chicken flocks with a colonising strain, adapted to chickens but avirulent for people.

Campylobacter species such as C. jejuni and C. coli are recognised as major causes of acute gastroenteritis worldwide in humans. Consumption of contaminated foods, including poultry, has been recognised as a source of the disease in humans. However it is possible that not all Campylobacter strains that may inhabit chickens may be capable of producing disease in humans. Hence, it is important that tests be developed that can distinguish potentially pathogenic strains from non-pathogenic strains and that strategies be developed to reduce the frequency of virulent strains in chickens.

Research

A DNA probe was constructed which can distinguish C. jejuni strains into two subgroups based on a DNA polymorphism; a two-band hybridisation profile typical of the majority of strains of chicken origin, or a single-band profile typical of the majority of strains of human origin. Using this DNA probe, it was shown for the first time that there are definite genetic differences between those strains of Campylobacter spp. that colonise chickens and those that are isolated from human disease. Research was also undertaken to establish whether there are differences between strains of C. jejuni in their ability to colonise chickens.

Outcomes

Outcomes of this work were twofold:

• A molecular DNA probe capable of distinguishing between the majority of the Campylobacter jejuni stains isolated from chickens and those isolated from human patients with campylobacteriosis was developed. The probe has been tested using a large number of C. jejuni strains from various sources in Australia, USA and UK. Approximately 70% of Australian chicken isolates of C. jejuni can be distinguished from human isolates. For USA isolates from chickens it is greater then 90%, and for UK isolates, 60%. The difference in the figures may be due to the differences in chicken farming methods between the countries.
• C. jejuni and C. coli strains isolated from chickens, and those isolated from human patients with campylobacteriosis, were tested for their ability to colonise two week old chicks. Three distinct types of strains were identified: 1. strains unable to establish persistent colonisation in the chicken intestinal tract; 2. strains capable of establishing persistent colonisation, but which are easily displaced by other strains; and 3. one strain which was not only able to colonise chickens, but was able to displace all resident strains. It was shown that an individual strain of C. jejuni can completely dominate the intestinal flora of chickens and displace other Campylobacter strains in a small experimental flock of chickens.

It is essential that a rapid and specific detection and differentiation system be designed to enable separation of disease-causing strains of Campylobacter spp. from avirulent strains. These avirulent strains can form part of the normal flora in chickens. The results of this project will lead to the establishment of a typing scheme for Campylobacter spp. that will be available to the chicken industry to characterise any flock isolates. There is great potential to further develop a molecular typing scheme that will distinguish ‘human virulent’ strains of Campylobacter spp. from ‘normal flora’. Future research will allow a reference laboratory for thermophilic Campylobacter spp. to be established, primarily for chicken isolates but also for human and other animal isolates, where the organism will be identified by comparing with a genetic profile database.

The discovery of Campylobacter isolates with varying potential to colonise chickens will enable selection of Campylobacter strains that are super colonisers of the chicken intestinal environment, but which have been characterised as non-pathogenic, for evaluation as potential ‘competitive exclusion’ agents. With further development, such a strain could be used to displace undesirable strains from chickens in commercial flocks and so reduce the possibility of transfer of pathogenic strains to the food chain.

RIRDC Project No: RMIT-5CM

Researcher: Dr Victoria Korolik and Prof Peter J Coloe

Organisation: Royal Melbourne Institute of Technology, Dept of Applied Biology & Biotechnology,  124 LaTrobe Street, MELBOURNE VIC 3000

Contacts: Phone: (03) 9660 2796   Fax: (03) 9662 3421   E-mail: victoria.korolik@rmit.edu.au

Increasing efficiency of lean tissue deposition in broiler chickens

Objective

• To increase the efficiency of lean meat growth in broiler chickens through nutritional manipulation of protein degradation via the insulin axis.

Background

Genetic selection of broiler chickens over the past 40 years has resulted in extremely rapid growth rate. It has also increased carcass fat content. A combination of organic chromium and a branched-chain amino acid, leucine, and some long chain fatty acids may enhance protein deposition, thereby reducing fatness in broiler chickens.

Research

Two experiments were conducted to examine the effect of graded levels of organic chromium and leucine and four different fat sources on the body composition of broiler chickens.

Outcomes

Chromium picolinate at 0.5ppm significantly (P<0.05) lowered the carcass fat level. Leucine did not interact with chromium to effect lean growth. Chromium had no effect on bird performance. Dietary leucine above the recommended maintenance level (1.2% of the diet) markedly (P<0.001) reduced the breast muscle yield.

The addition of fish oil to broiler diets significantly reduced (P<0.05) the abdominal fat pad weights compared to birds on linseed diets. The amount of fat in the diet (2% or 4%) did not affect body composition.

Implications

Provisions could be made for chromium levels and some polyunsaturated fatty acids in practical feed formulations to take advantage of their effects on energy utilisation and carcass fat content.

Publications

Researchers: Dr Mingan Choct

Organisation: University of New England, School of Rural Science and Natural Resources – Animal Science,  ARMIDALE NSW 23510

Contacts: Phone: (02) 6773 5121   Fax: (02) 6773 3992   E-mail: mchoct@metz.une.edu.au

The metabolisable energy of 'viscous' and problem grains measured at two sites and methods of prediction of grain samples likely to respond to enzyme additions

Objectives

• To identify and understand why 'viscous' grains (cereals) and some grain legume seeds sometimes give depressed performance and do not always appear to respond to feed enzymes. Those that do, do not always give improved performance despite an increase in metabolisable energy.
• To develop a method for prediction of problem grain samples and their likelihood of responding to enzyme addition.

Some feed grains contain one or more anti-nutritional factors (ANF). In cereal grains these are mainly the non-starch polysaccharides (NSP) such as the arabinoxylans (pentosans) and b -glucans found in the endosperm walls rather than in the outer or bran layers. Not all cereal grains contain NSP but wheat in particular may contain high levels of NSP, particularly the arabinoxylans. As a consequence, when these grains are consumed by poultry some of the NSP goes into solution causing highly viscous gut digesta, particularly in the small intestine. The result of this is reduced nutrient digestion and wet and sticky droppings. The practical consequences can be poor feed conversion ratio, reduced growth rate of broilers, wet litter, hock burn, breast blisters and down-graded carcasses.

Feed enzymes have been used to reduce the negative aspects of NSP by degrading them and thereby reducing the viscosity of gut digesta.

Since not all wheats and other grains contain anti-nutritional factors in significant amounts, a response to feed enzymes would not always be anticipated. Yet these enzymes are routinely added to wheat-based and other diets at considerable cost, despite the fact that they only really need to be added when the diet contains problem grains. It would be of considerable commercial use to devise a rapid screening method which could identify problem grains prior to their incorporation in diets; a feed enzyme would then be added to alleviate the problem.

Research

There were three experiments undertaken. All experiments were with broiler chickens grown to 21 days of age. This the most sensitive period for detecting a response to offending grains and for monitoring a response to feed enzyme additions. In the three experiments, a detailed chemical description was undertaken of the behaviour of wheat, oats and two grain legumes within the bird's digestive system. It was hoped that this information would be used as a basis of an in vitro method which would simulate digestion by the measurement of either the appearance of key metabolites or the disappearance of feed components.

Outcomes

Four diets were examined in experiment one, these were wheat, oats, sweet lupins and faba beans at high levels of inclusion (250-700 g/kg). AME was considerably lower on all diets at the terminal ileum than in excreta at 22 and 40 days of age suggesting considerable fermentation in the hind gut. This was confirmed by very high levels of the steam volatile fatty acids measured in caecal contents. The wheat sample used was of unusually high viscosity but this did not translate into a low AME value.

In the second experiment an examination was undertaken of several published in vitro methods that would predict foregut viscosity and also AME using 24 diets. Inclusion of the wheat samples was 700 g/kg. Relationships between in vivo viscosity and the most promising in vitro method (Bedford's) did not show sufficiently close agreement for the purposes of prediction. Nor did relationships with in vitro viscosity and AME (R²=0.43), digestible energy at the terminal ileum, or gross energy of digesta dry matter at the terminal ileum give useful predictions. AME and gross energy of hindgut digesta, pentosans in feed and hindgut viscosity, and food intake and hindgut viscosity were all examined but again relationships proved to be disappointing.

In experiment three, four wheats of different protein levels and extract viscosities were examined. Twelve diets were formulated by adding 0.0, 0.25 or 0.5 g of the exogenous enzyme, Avizyme (Finnfeeds International). Diets were fed to eight birds/cage and replicated four times. Results showed that enzyme inclusion had a dramatic effect on gut viscosity but there was little difference in response between the two levels of enzyme. There was also an increase in digestible energy measured in the hindgut with feed enzyme addition and sometimes in feed conversion ratio (FCR).

In vitro viscosity had a good correlation (R²=0.53) with liveweight gain; this was particularly strong after viscosity exceeded 2.5 cps. However, when the in vitro viscosity of the cereal grains was related to excreta stickiness score, there was a good relationship (R²=0.82). Similarly in vitro viscosity correlated well with feed intake (R²=0.70) ileal digestible energy (R²=0.73) and in vivo viscosity (R² =0.73).

Implications

The need to screen extensively for low-energy wheats using conventional methods is time consuming and impractical, particularly as only very few would be considered to be of low AME and therefore of high viscosity. Many measurements were made on a large number of samples to examine possible predictive measures. The in vitro viscosity of wheats but not of diets generally were closely correlated with liveweight gain. Although this was a satisfactory outcome, the methods of extracting viscous material are time consuming.

In order to provide industry with a rapid and simple test to predict low AME wheats, a method based on excreta moisture or stickiness score might be the most useful. But this needs to be tested and then correlated with gut viscosity and bird performance with and without a feed enzyme.

Publications

Researcher: A/Prof David J Farrell and Dr Suzanne Petersen

Organisation: University of Queensland, Dept of Agriculture, ST LUCIA QLD 4072

Contacts: Phone: (07) 3365 2051   Fax: (07) 3365 1177   E-mail: farreld@dpi.qld.gov.au

Determination of true amino acid digestibility of feedstuffs

Objectives

• To determine the true amino acid availability of a range of feed ingredients using guanidinated protein and use these values in feed formulation.
• To predict the magnitude of endogenous amino acid loss from dietary composition.

The project was initiated in response to the need in the poultry industry to develop a better feed formulation system than one based on total amino acids. Amino acid digestibility is not the same for all feed ingredients, with some having lower digestibility than others. The use of digestible amino acid values in feed formulations should therefore more consistently meet the birds’ requirements and improve the efficiency of feed utilisation than the currently employed total amino acid system. However, the range of Australian feed ingredients for which digestible amino acid values are available is limited. This project was therefore directed towards developing a database of digestible amino acid values for a wide range of Australian feed ingredients.

Research

Ileal amino acid digestibilities, both true and apparent, in a range of Australian feedstuffs were generated in a series of digestibility assays. The homoarginine marker was used to distinguish between exogenous and endogenous amino acids, and to determine true digestibility values. A number of studies were undertaken to assess the validity of the basic assumptions underlying the use of this homoarginine technique. While the determination of true ileal amino acid digestibility values (using the homoarginine technique) focused on selected ingredients, apparent ileal digestibility values were determined for a large number of samples with the object of characterising the variability within locally available ingredients.

Outcomes

Comparisons of digestibility estimates at ileal and excreta levels demonstrated that analysis of digesta from the terminal ileum rather than excreta will yield more accurate values of amino acid digestibility in feed ingredients for poultry. A protocol for the determination of endogenous amino acid output under continuous feeding conditions using the homoarginine technique was developed.

True digestible amino acid values for four samples of soybean meal, two samples of cottonseed meal, sunflower meal, meat and bone meal, canola meal, gelatine and three samples of casein were determined. Apparent ileal digestibility values were determined for over 72 samples representing 22 different feed ingredients. A database was compiled of the apparent ileal amino acid digestibilities of Australian feed ingredients for broilers. This database was published by RIRDC and made available to the industry in February 1998.

Studies undertaken also showed that both apparent and true digestibility values are additive and that the digestible amino acid supply in a complete diet can be predicted, with reasonable accuracy, based on amino acid digestibility determined for individual feed ingredients.

Implications

The database of digestible amino acid values generated by this project will enable industry nutritionists to fine-tune their feed formulations, thereby lowering feed costs and improving the feed efficiency of broiler production.

Publications

RIRDC Project Number: US-67CM

Researcher: A/Prof Wayne Bryden and Dr Ravi Ravindran

Organisation: University of Sydney, Dept of Animal Science, CAMDEN NSW 3570

Contacts: Phone: (02) 4655 0658   Fax: (02) 4655 0693

E-mail: wayneb@camden.usyd.edu.au

       Last updated: 17 August 1998 Copyright © RIRDC http://www.rirdc.gov.au/comp98/cm1.htm