207 research outputs found
Artificially extending photoperiod improves milk yield in dairy goats and is most effective in late lactation
No full textV.M. Russo, A.W.N. Cameron, F.R. Dunshea, A.J. Tilbrook and B.J. Leur
Pigs weaned at 14 D reach slaughter weight at the same time as pigs weaned at 28 D but are fatter
No full textPigs are commonly weaned at 23-27 days of age. However, sow milk production peaks at 10-14 days of lactation after which it is only sufficient for pigs to attain about 50% of their growth potential (Dunshea et al., 1995). By weaning earlier and providing pigs with a suitable diet, it may be possible to capitalize on their potential for rapid growth. The present study was designed to determine the interrelationships between sex, weaning age and weaning weight on subsequent growth performance
Combining a ractopamine feeding regime and porcine somatotropin has additive effects on finisher pig performance
No full textTreatment of finisher pigs with dietary ractopamine (RAC; Paylean®, Elanco Animal Health, NSW) improves daily gain and feed efficiency commensurate with increased protein deposition in finishing pigs (Dunshea et al., 1993). However, effects of RAC on P2 fat deposition are equivocal. Dunshea et al. (1993) found no change in gilts and barrows, whilst a trend towards reduced P2 depth was observed in boars fed dietary RAC. Exogenous porcine somatotropin (pST; Reporcin®, OzBioPharm Pty Ltd, Victoria) improves daily gain and feed efficiency and increases the ratio oflean to fat in carcases of boars, gilts and barrows (Campbell et al., 1989). As both technologies are applied at the end of the finishing phase, it is of interest to determine whether a combination of RAC and pST has additive effects on pig performance
Classification of sheep category using chemical analysis and statistical classification algorithms
No full textIn Australia, dentition (eruption of permanent incisors) is used as a proxy for age to define sheep meat quality. Lamb is defined as having no permanent incisors, hogget as having at least one incisor and mutton is defined as having two or more incisors. Classification of the carcase is done at the abattoir prior to the removal of an animal’s head. Recently, an Australian Senate inquiry into meat marketing reported that there was concern that substitution of hogget and mutton for lamb may be occurring in the industry. At present, no objective method is available that can be used for classifying sheep category. The general aims of this thesis were to i) evaluate whether chemical analysis of branched chain fatty acid (BCFA) content could be used as an objective tool to determine sheep age, ii) understand the effect that some production factors had on BCFA concentrations in Australian sheep and iii) develop new approaches (whether chemical and/or statistical) for determining sheep category (age).
BCFAs are implicated as the main contributors to “mutton flavour”, often associated with the cooked meat of older animals. BCFAs are reported to increase with age, which suggests that chemical analysis of these compounds could be used as an objective method. Concentrations of three BCFAs (4-methyloctanoic (MOA), 4-ethyloctanoic (EOA) and 4- methylnonanoic (MNA) acids) were measured in a survey of fat samples taken from 533 sheep carcases at abattoirs in New South Wales, Victoria and Western Australia. This thesis shows that, on its own, chemical analysis of the BCFAs is not sufficient to discriminate lamb from hogget and mutton as pre-slaughter nutrition is a significant factor in classifying sheep using this approach. Uncertainty at the BCFA concentration ranges found in Australian sheep was determined to be high making it difficult to discriminate between sheep carcases of different ages based on the BCFA level.
Fast gas chromatography was evaluated as the basis for a high throughput chemical technique but was not sufficiently sensitive for BCFA measurements. Solid-phase microextraction (SPME) was also found to be suitable for sampling 3-methylindole and p-cresol, compounds responsible for diet-related “pastoral flavour” in sheep fat, but further work is needed to validate this approach for measurement of these compounds in sheep fat.
Statistical classification algorithms, when applied to the chromatograms measured for the 533 carcasses, showed great promise for predicting sheep category. Specifically, the random forests algorithm, when applied to mean-centred data, gave 100% predictive accuracy when differentiating between lamb, hogget and mutton. This approach could be used for the development of an objective method for determining sheep age and category, suitable for use by the Australian sheep meat industry
The synergistic effects of ractopamine and porcine somatotropin on finisher gilt performance
No full textRactopamine hydrochloride (Paylean®, RAC, Elanco Animal Health Pty Ltd, Macquarie Park, NSW) is an approved ingredient for pigs used to increase lean tissue growth and improve production efficiency (Dunshea et al., 2005). Porcine somatotropin (Reporcin®, pST, OzBioPharm Pty Ltd, Knoxfield, VIC) is a protein naturally produced by the pig that induces the redirection of nutrients towards increased muscle growth and decreased fat growth (Dunshea et al., 2005). Recent research (Rikard-Bell et al., 2009) has shown that combining RAC and pST in the last two weeks of production improves feed efficiency. The aim of this experiment was to evaluate changes in production efficiency obtained by combining RAC and pST in the last four weeks of growth
Altering the timing of an immunocastration vaccine to optimise pig performance
No full textEntire male pigs are more efficient and leaner than surgical castrates, but ’boar taint’ can compromise eating quality. Vaccination of boars with a gonadotropin releasing hormone (GnRH) vaccine (Improvac®, Pfizer Ltd, Parkville, VIC) can eliminate boar taint, and allows pigs to retain all of the performance attributes of entire males up until the time they receive the second vaccination, normally four to five weeks pre-slaughter (Dunshea et al., 2001). However increases in backfat depth (P2) and feed conversion ratio (FCR) compared to entire males has limited the uptake of this technology. If giving the second vaccination closer to the time of slaughter could eliminate boar taint, there would be less of a cost in lost production to producers. An experiment was conducted to test the hypothesis that reducing the time between administration of the second vaccination with the GnRH vaccine and their slaughter will reduce the impact on P2 and FCR while still reducing boar taint
Comparison of a grain-based diet supplemented with synthetic vitamin E versus a lucerne (alfalfa) hay-based diet fed to lambs in terms of carcass traits, muscle vitamin E, fatty acid content, lipid oxidation, and retail colour of meat
No full textDietary supplementation of vitamin E (VitE) in a synthetic or natural form was examined. Forty-eight lambs were assigned (n = 16) to either a grain-based diet at moderate (MOD, 42 mg∙kg−1 VitE as all-rac α-tocopheryl acetate) or supranutritional (SUP, 285 mg∙kg−1 of vitE) levels of synthetic VitE or a lucerne hay-based diet (LUC; 37 mg∙kg−1 VitE) for 8 weeks. Meat from the LUC group had lower muscle n-6 and PUFA levels compared to meat from the MOD and SUP groups. Despite a similar VitE intake, muscle VitE was higher for LUC compared to MOD, while SUP lambs showed the highest VitE. Lipid oxidation did not differ between groups. For fresh meat, redness tended to be higher in LUC fed lambs than the other two groups, but brownness formation was only lower than the SUP group. For aged meat colour stability, redness tended to be higher in lambs fed SUP and LUC, whereas highest browning occurred in the MOD group
Acetyi-CoA carboxylase activity and belly fat of gilts housed conventionally or on deep litter
No full textLipid accretion, or the storage of fat, is characterised by the formation of triglycerides, primarily from free fatty acids (FFA) and glycerol-3-phosphate. In pigs, FFA formation occurs when glucose is metabolised via glycolysis and the citrate cleavage pathway to form acetyl-CoA in the cytoplasm where it can act as a substrate for acetyl-CoA carboxylase, the rate-limiting step of lipogenesis (Dunshea and D'Souza 2003). Trezona et al. (2005) reported that pigs housed conventionally had more belly fat than pigs housed on deep litter. In this study, we hypothesised that acetylCoA carboxylase activity in the belly fat of pigs housed conventionally would be higher than in deep litter pigs
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