Beefing up starch digestion
Any improvements in starch digestion in cattle would undoubtedly be of great benefit to the feedlot industry. There are numerous factors that are likely to vary between animals that may affect both the efficiency and site of starch digestion. The benefits of starch digestion in the small intestine, as opposed to in the rumen, include a higher energetic efficiency, and a reduced risk of acidosis provided that high levels of starch do not reach the hindgut. Recent research has identified genetic differences between similar cattle in their ability to digest starch. The evidence is provided by differences between progeny groups of steers in the level of fermentation occurring in the hindgut. We have also found between-animal differences in total tract starch digestibility that are consistent across diets.
Enhancing Starch Digestion in the Equine Small Intestine
Cereal grains do not form part of the natural diet of equines, however, results from an initial survey conducted, suggest that horses in the Australian thoroughbred industry are currently being fed on average about 7 kg of grain concentrate/day. Horses are not well equipped to digest the starch from cereal grains in the small intestine and as a consequence, the hindgut fermentation of starch, which may lead to hindgut lactic acidosis and diseases such as laminitis, is an evident problem in the thoroughbred industry. Two main factors determine the extent of starch digestion that will occur in the equine small intestine. These are: 1. the attributes of cereal grains that determine starch digestibility; and 2. the ability of an individual horse to digest starch in the small intestine. The general hypothesis for this thesis was therefore that both the attributes of cereal grains that determine starch digestibility and the ability of individual horses to digest starch in the small intestine will determine how much cereal grain starch may be fed 'safely' before problems with hindgut starch fermentation and acidosis will be experienced. A series of experiments were conducted to test this hypothesis and to specifically examine the effect of grain species, grain processing and enzyme supplementation on small intestinal starch digestion in horses. Oats, barley, triticale, corn and rice were the cereal grains studied and expansion, extrusion, steam rolling and micronizing were the processing techniques investigated.
Nutritional effects on mammary development and milk production: the effects of prepartum protein supplements
Sixty mature crossbred ewes were grouped into four different feeding treatments on day 110 of pregnancy until lambing to evaluated the effect of prepartum protein intake on mammary development and subsequent productive performance. Treatments were similar for the amount of crude protein (60 g/h/d) and differed in the quality of protein content. Following parturition, all ewes were fed the same feed. Ewes did not differ in initial body weight and body condition score. Ewes fed the protein diets exhibited greater liveweight gain during gestation and then increased weight loss after lambing. Mean liveweight for the protein fed ewes at parturition was greater than the controls. Change in body condition score was greater for the high UDP group than for the low UDP group at lambing, but riot in early lactation. Lamb birth weight and growth rate did not differ significantly between treatments. Prepartum diets influenced mammary development and subsequent milk production. Ewes given lupin supplement produced more milk (P<0.05) with highest milk protein (P<0.05) production. Milk and milk fat production were influenced by prepartum undegradable protein. Supplemental protein prepartum may improve postpartum performance by minimising mobilisation of maternal labile protein pools to meet foetal and maternal growth requirements in late gestation and subsequently improve lactation performance.
The effects of added fructooligosaccharide (Raftilose®P95) and inulinase on faecal quality and digestability in dogs
A 3x2 factorial experiment was designed to examine the effects of dietary fructooligosaccharides (FOS) level, and the presence or absence of an enzyme (inulinase), on aspects of faecal quality and apparent coefficients of nutrient digestibility in doxs. Three extruded dry diets based on wheat, pearl barley and wheat by-products were formulated to contain (dry matter basis) 1.75g/kg (Diet A), 4.7 g/kg (Diet B) and 61.7 g/kg (Diet C) FOS. The FOS content of Diets B and C was achieved by adding 30 and 60 g/kg (DM) Raftilose®P95, a commercial FOS product. The addition of inulinase (500 ml (1.2x10⁶U) per tonne) was examined for each diet to counteract any potentially negative effects of added FOS on faecal quality and digestibility, and was sprayed onto the diet at feeding at a level of 500 ml per tonne of food. The experiment lasted 13 days with faecal collections occurring on the final 5 days. Measurements taken were: faecal score (one indicating hard faeces, five indicating diarrhoea), coefficients of total tract apparent digestibility (CATTD), faecal pH, and volatile fatty acids (VFA) and lactate concentrations. The CATTD for fat and energy decreased with greater levels of dietary FOS. Increased levels of FOS decreased (P<0.05) faecal pH and the content of dry matter (DM) in the faeces and also increased (P<0.05) the faecal score, although this remained in the 'ideal' range of 1.5-2.5. Addition of inulinase increased (P<0.05) the faecal pH. Faecal lactate concentrations increased with greater levels of FOS (P<0.05; 84.9 versus 142.5 versus 288.7 mmol/kg faeces DM for Diets A, B and C, respectively), suggesting that the growth and (or) activity of lactate-producing bacteria in the colon were enhanced. Higher levels of FOS in an extruded dog food caused faeces to become wetter and more acidic, and consequently the number of dogs that had unacceptable faecal scores increased. However, and at the highest dietary FOS level (61.7 g/kg DM), inulinase caused significantly drier faeces and increased the number of dogs within the 'ideal' range of faecal score.
Using Australian Sheep Breeding Values to increase lean meat yield percentage
This study describes the impact of Australian Sheep Breeding Values (ASBV) for post-weaning weight (PWWT), C-site fatness (PFAT) and eye muscle depth (PEMD) on lamb carcasses within the Australian Sheep Industry CRC Information Nucleus Flock. These results are taken from the 2007 drop progeny, consisting of ~2000 lambs slaughtered at a target weight of 21.5 kg. These lambs were the progeny of sires selected to ensure genetic diversity across various production traits. As expected, the PWWT ASBV increased weight at slaughter, and hot standard carcass weight. Dressing percentage was markedly improved by increasing PEMD ASBV, thus prime lamb producers will be maintaining an animal of similar weight on farm, but delivering a markedly larger carcass at slaughter. Lean meat yield % (LMY%) was highest in the progeny of sires with low PFAT ASBV, which decreased whole carcass fatness and increased muscularity. PWWT ASBV affected carcass composition but had little impact on LMY%, as the decreased fatness was largely offset by increased bone, with relatively little change in muscle content. Lastly, PEMD ASBV had little impact on whole carcass LMY%, but did appear to cause some level of muscle redistribution to the higher value loin cuts, in turn increasing the value of the carcass lean.
Immunisation Against Lactic Acidosis in Sheep and Cattle
Introduction: Lactic acidosis is due to the over production of lactic acid in the rumen by the bacteria, 'S. bovis' or a combination of 'S. bovis' and 'Lactobacillus' when sheep and cattle consume large amounts of grain. It was hypothesised that the risk of lactic acidosis could be reduced by immunisation against the lactic acid producing bacteria. The present studies were conducted to test this hypothesis and investigate several key factors for developing an immunisation strategy against lactic acidosis. ... General discussion: Results from the studies in sheep and cattle support the hypothesis that the risk of lactic acidosis can be reduced by immunisation against 'S. bovis' or 'S. bovis' and 'Lactobacillus'. Live vaccine (using DEAE-dextran combined with mineral oil as an adjuvant) may provide a suitable protection using one booster following a primary immunization administered intramuscularly. This novel approach to reducing the risk of lactic acidosis associated with grain feeding offers a promising alternative to current practices of using feed additives, such as antibiotics active against the lactic acid-producing bacteria.
ASKBILL as a web-based program to enhance sheep well-being and productivity
ASKBILL is a web-based program that uses farm measurements, climate data and information on genetics to predict pasture growth, animal performance and animal health and climate risks. The program uses several biophysical models, which are customised by user inputs, localised daily weather updates and a dynamical probabilistic 90-day climate forecast to enhance sheep well-being and productivity. This approach can minimise the requirement for manual, auto and remote measurements, thus reducing labour requirements and complexity. In this article, the animal growth model provides an example of a biophysical model used to provide predictions. This is an energy-based model and the model parameterisation is designed to be physiologically meaningful and able to be customised for the genetic merit of the animal using a growth coefficient that calibrates growth of body components and energy requirements. A key feature of the animal growth model is its forecast projections, which are based on an ensemble of simulations. The model can estimate supplementary feeding rates required to achieve target liveweights and body condition scores and stocking rates required to achieve target pasture levels. The model can be customised for a farm and its livestock and is updated daily in response to climate data. This dynamic feature enables it to provide early stage alerts to users when animal production targets are unlikely to be met.
The effect of current grain feeding practices on hindgut starch fermentation and acidosis in the Australian racing Thoroughbred
A survey of 72 thoroughbred trainers in several regions of NSW was conducted to better define current grain feeding practices, and the risks involved with grain feeding in the Australian thoroughbred racing industry. Results from the survey indicate that horses in the industry are currently being fed an average of 7.3 ± 0.23 kg of grain concentrate per day, with oats, commercial pre-mixed diets and corn most commonly used. The feeding of extruded, micronised and steam flaked grains was uncommon. The results of grain and faecal sample analyses conducted during the survey indicate that incomplete starch digestion in the equine small intestine and subsequent hindgut starch fermentation and low hindgut pH are common. These observations quantify the adverse impact of current grain feeding practices on faecal measures of gut health and demonstrate that when selecting grains for use in the thoroughbred racehorse, greater emphasis should be placed on the starch digestibility characteristics of grains.
Antibody responses to lactic acid producing bacteria in sheep immunized with experimental acidosis vaccines
Acidosis is an economically important disease of ruminant livestock, involving both reduced productivity and serious animal welfare implications. Major lactic acid producing bacteria in sheep were identified by Al Jassim and Rowe (1999) and it is likely that the proliferation of these bacteria, under certain feeding regimes, leads to acidosis. Antibiotic feed additives are currently used in management of acidosis but there are serious concerns about this approach and, consequently, vaccination against acidosis-producing bacteria as a means of preventing the condition is under active investigation in our laboratory. The aim of this trial was to measure antibody responses to a range of acidosis-producing bacteria, following administration of experimental vaccines. Forty-nine healthy adult merino wethers were used for this study and run together as a single flock throughout the experiment. Animals were randomly allocated into 7 groups, to be immunized with one of six different bacterial isolates, or non-immunized as controls. Vaccines were prepared from pure bacterial isolates (formalin killed), emulsified in Freund's adjuvant, and administered intramuscularly at weeks 0 and 4. Freund's complete adjuvant was used for the primary immunization, and Freund's incomplete adjuvant was used for the secondary immunization. Samples of venous blood were collected before immunisation and every two weeks for ten week. Concentrations of IgG antibodies in serum were determined by ELISA. Antibody levels produced in response to immunizations with each of the 6 isolates are shown in Table 1. Strong antibody responses were produced by the three streptococcal isolates, with peak antibody concentrations at week 6. There was a 12-fold increase produced by the two 'S. bovis' strains, whereas a 57-fold increase was produced by the 'S. equinus'. Antibody responses were also produced by 'Selenomonas ruminantium', with antibody levels reaching a peak at week 10. There was a relatively weak antibody response to 'Lactobacillus vitulinus'.
The use of calcium hydroxide to improve the nutritional properties of whole cottonseed
The continuing decline in the terms of trade of the Australian rural industries is maintaining pressure on agricultural industry to assess and modify the manner in which resources are applied to the production of food and fibre. Management practices in industries based on ruminant livestock are changing, particularly with an increase in the economic importance of grain based feedlots and the use of nutritional supplements for livestock on pasture in the meat, wool and dairy industries. These changes result from a need to use particular feed supplements as a means of manipulating and optimising production systems with respect to some limiting resource or factor. Such factors include periodic reductions in pasture quality or a window of opportunity for feeding to meet the production requirements of a particular market. There is also greater acceptance by the livestock industries of the use of novel feed materials, generally the byproducts of the cropping and horticultural industries, as nutritional supplements for cattle and sheep on pasture. Modification of a novel feed material to change its physical and/or nutritional form is often required before it can be optimally incorporated into a livestock production system. Processing increases the cost of the material. There are therefore financial benefits to the livestock producer in using feed supplements that require little processing. Cottonseed is a significant feed resource for ruminant livestock production in eastern Australia. The irrigation districts of Queensland and New South Wales, currently growing all of Australia's cotton crop, produce on average of 583 kT of cottonseeds each year (1990 to 1996) as a byproduct of cotton lint production (ABARE 1996).