V. H. Oddy

Bio: V. H. Oddy is an academic researcher from University of New England (Australia). The author has contributed to research in topics: Beef cattle & Residual feed intake. The author has an hindex of 23, co-authored 79 publications receiving 2352 citations. Previous affiliations of V. H. Oddy include New South Wales Department of Primary Industries & Universidade Federal de Minas Gerais.

Biological basis for variation in residual feed intake in beef cattle 1: Review of potential mechanisms

Abstract: There is a growing body of evidence that there is genetic variation in beef cattle feed intake relative to their liveweight and weight gain Difference in feed intake, above and below that expected or predicted on the basis of size and growth, is measured as residual feed intake Variation in residual feed intake must be underpinned by measurable differences in biological processes This paper summarises some plausible mechanisms by which variation in efficiency of nutrient use may occur and presents several testable hypotheses for such variation A companion paper [Richardson and Herd (2004) Aust J Exp Ag 44, 431–441] presents results from experiments on cattle following divergent selection for residual feed intake There were at least 5 major processes identified by which variation in efficiency can arise These are associated with variation in intake of feed, digestion of feed, metabolism (anabolism and catabolism associated with and including variation in body composition), activity and thermoregulation The percentage contribution of different mechanisms, to variation in residual feed intake, was: 9% for differences in heat increment of feeding; 14% for differences in digestion; 5% for differences in body composition; and 5% for differences in activity Together, these mechanisms may be responsible for about one-third of the variation in residual feed intake The remaining two-thirds were likely to be associated with heat loss due to variation in other processes, such as protein turnover and ion transport There is no shortage of candidate mechanisms that, singularly or in combination, might contribute to genetic variation in energy utilisation in ruminants Further research in beef cattle, to better define these mechanisms and enable their incorporation into breeding programmes, may lead not only to cattle which eat less for the same performance, but are superior in other traits as well

Growth, development and nutritional manipulation of marbling in cattle: a review

Abstract: This review describes the pattern of intramuscular fat accretion in cattle and the potential for its manipulation during both the pasture (or backgrounding) and intensive grain-finishing phases of development. A growth curve for the development of marbling in British and Japanese Black type breeds is discussed with the conclusion that 3 phases of development exist: (i) a period of growth up to ∼200 kg hot carcass weight where intramuscular fat does not increase; (ii) a period of linear development as carcass weight increases from 200 to 450 kg; and (iii) the attainment of mature body size (∼500 kg carcass weight depending on genotype) at which intramuscular fat content appears to reachea maximum. Data are also presented to show that the intramuscular and other fat depots develop at similar rates indicating that intramuscular fat is not a late maturing depot. Pre-finishing growth checks reduce the initial intramuscular fat at the start of finishing and this is translated into lower levels at the end of finishing. It is argued that the greatest potential for the manipulation of intramuscular fat accretion during fattening is via an increase in the net energy of the ration. Increasing net energy can be achieved by increasing the cereal grain content of the diet (grain v. grass); by feeding processed cereal grain, which allows both maximal rumen fermentation and small intestinal digestion of starch, and by increasing the lipid content of the diet. In addition it is proposed that the substrate supply or hormonal milieu can also be optimised, along with the availability of net energy to maximise fat accretion. The role of lipolysis (fat turnover) as a regulator of fat accretion is also discussed.

Body composition and implications for heat production of Angus steer progeny of parents selected for and against residual feed intake

Abstract: Yearling Angus steer progeny of parents selected for low residual feed intake (RFI; high efficiency) or high RFI (low efficiency) were evaluated for feed intake, growth and differences in body composition. RFI is the difference between actual feed intake and expected feed intake based on an animal’s size and growth over a test period. Individual intakes of a high grain content ration and growth rates were recorded for 140 days and then the steers were slaughtered for measurement of body composition. All internal organs and non-carcass fat depots were removed, weighed and ground for chemical analysis. Carcasses were kept overnight in the chiller and the left half of every carcass physically dissected into retail cuts, and then into total fat, lean and bone. Carcass fat and lean were then combined and ground for chemical analysis. Steers from low RFI parents ate less (P<0.05) than the steers from high RFI parents, for similar rates of growth. Improvement in RFI was accompanied by small changes in body composition towards greater lean and less fat in the progeny of low RFI parents. Correlations of sire estimated breeding values for RFI with end of test whole body chemical protein, chemical fat and a principal component that condensed information on fat and lean body composition at the end of the test, were statistically significant. These confirmed there was a genetic association between body composition and RFI, with fatness being associated with higher RFI (i.e. lower efficiency). However, the correlations were small and suggested that less than 5% of the variation in sire RFI was explained by variation in body composition of their steer progeny. There was no evidence that a difference in the chemical composition of gain over the test explained the greater intake of metabolisable energy (ME) by the high RFI steers. The results suggest that the difference in ME intake following a single generation of divergent selection for RFI was due to metabolic processes rather than to changes in body composition.

A universal equation to predict methane production of forage-fed cattle in Australia

Abstract: The methods for estimating methane emissions from cattle as used in the Australian national inventory are based on older data that have now been superseded by a large amount of more recent data. Recent data suggested that the current inventory emissions estimates can be improved. To address this issue, a total of 1034 individual animal records of daily methane production (MP) was used to reassess the relationship between MP and each of dry matter intake (DMI) and gross energy intake (GEI). Data were restricted to trials conducted in the past 10 years using open-circuit respiration chambers, with cattle fed forage-based diets (forage >70%). Results from diets considered to inhibit methanogenesis were omitted from the dataset. Records were obtained from dairy cattle fed temperate forages (220 records), beef cattle fed temperate forages (680 records) and beef cattle fed tropical forages (133 records). Relationships were very similar for all three production categories and single relationships for MP on a DMI or GEI basis were proposed for national inventory purposes. These relationships were MP (g/day) = 20.7 (±0.28) × DMI (kg/day) (R2 = 0.92, P < 0.001) and MP (MJ/day) = 0.063 (±0.008) × GEI (MJ/day) (R2 = 0.93, P < 0.001). If the revised MP (g/day) approach is used to calculate Australia’s national inventory, it will reduce estimates of emissions of forage-fed cattle by 24%. Assuming a global warming potential of 25 for methane, this represents a 12.6 Mt CO2-e reduction in calculated annual emissions from Australian cattle.

Myostatin, a negative regulator of muscle growth, functions by inhibiting myoblast proliferation.

Abstract: Myostatin, a member of the transforming growth factor-β (TGF-β) superfamily, has been shown to be a negative regulator of myogenesis. Here we show that myostatin functions by controlling the proliferation of muscle precursor cells. When C2C12 myoblasts were incubated with myostatin, proliferation of myoblasts decreased with increasing levels of myostatin. Fluorescence-activated cell sorting analysis revealed that myostatin prevented the progression of myoblasts from the G1- to S-phase of the cell cycle. Western analysis indicated that myostatin specifically up-regulated p21Waf1, Cip1, a cyclin-dependent kinase inhibitor, and decreased the levels and activity of Cdk2 protein in myoblasts. Furthermore, we also observed that in myoblasts treated with myostatin protein, Rb was predominately present in the hypophosphorylated form. These results suggests that, in response to myostatin signaling, there is an increase in p21 expression and a decrease in Cdk2 protein and activity thus resulting in an accumulation of hypophosphorylated Rb protein. This, in turn, leads to the arrest of myoblasts in G1-phase of cell cycle. Thus, we propose that the generalized muscular hyperplasia phenotype observed in animals that lack functional myostatin could be as a result of deregulated myoblast proliferation.

Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers.

Abstract: Intramuscular fat (IMF) content plays a key role in various quality traits of meat. IMF content varies between species, between breeds and between muscle types in the same breed. Other factors are involved in the variation of IMF content in animals, including gender, age and feeding. Variability in IMF content is mainly linked to the number and size of intramuscular adipocytes. The accretion rate of IMF depends on the muscle growth rate. For instance, animals having a high muscularity with a high glycolytic activity display a reduced development of IMF. This suggests that muscle cells and adipocytes interplay during growth. In addition, early events that influence adipogenesis inside the muscle (i.e proliferation and differentiation of adipose cells, the connective structure embedding adipocytes) might be involved in interindividual differences in IMF content. Increasing muscularity will also dilute the final fat content of muscle. At the metabolic level, IMF content results from the balance between uptake, synthesis and degradation of triacylglycerols, which involve many metabolic pathways in both adipocytes and myofibres. Various experiments revealed an association between IMF level and the muscle content in adipocyte-type fatty acid-binding protein, the activities of oxidative enzymes, or the delta-6-desaturase level; however, other studies failed to confirm such relationships. This might be due to the importance of fatty acid fluxes that is likely to be responsible for variability in IMF content during the postnatal period rather than the control of one single pathway. This is evident in the muscle of most fish species in which triacylglycerol synthesis is almost zero. Genetic approaches for increasing IMF have been focused on live animal ultrasound to derive estimated breeding values. More recently, efforts have concentrated on discovering DNA markers that change the distribution of fat in the body (i.e. towards IMF at the expense of the carcass fatness). Thanks to the exhaustive nature of genomics (transcriptomics and proteomics), our knowledge on fat accumulation in muscles is now being underpinned. Metabolic specificities of intramuscular adipocytes have also been demonstrated, as compared to other depots. Nutritional manipulation of IMF independently from body fat depots has proved to be more difficult to achieve than genetic strategies to have lipid deposition dependent of adipose tissue location. In addition, the biological mechanisms that explain the variability of IMF content differ between genetic and nutritional factors. The nutritional regulation of IMF also differs between ruminants, monogastrics and fish due to their digestive and nutritional particularities.