This paper reports an experiment examining the effect of age and protein supplementation on growth and fertility of Shorthorn-Devon cross heifers grazing natural pastures in the summer rainfall, subtropical environment of the Upper Clarence valley, north-eastern New South Wales. Heifers born over the period October to January 1963-64 were weaned in June 1964 and allotted at random within age groups (by month of birth) to a supplemented or non-supplemented treatment. The supplemented heifers were given linseed meal during the dry winter period each year from 1964 to 1966 inclusive (May-June to September-October). They were weighed each month and joined with bulls in the early summer of 1965 (2 years) and 1966 (3 years). They were examined for pregnancy in the autumn, and their calves were identified at birth. Supplemented heifers gained weight throughout and non-supplemented heifers generally lost weight in the winter periods. At two years fertility was closely related to liveweight at joining in supplemented heifers, but not in others. Heifers born in January gave the poorest reproductive performance, as the two supplemented ones that became pregnant in 1965 died at calving, and two-thirds of the non-supplemented ones were still empty after joining as 3-year-olds. The advantage of high 2-year-old fertility gained by heifers born in October and November, due to their greater size at joining, was partly offset by low fertility when lactating the following year. It is concluded that a decision as to whether a heifer should be supplemented during a period of nutritional stress prior to joining ought to be based on the probability of her reaching a prescribed target weight at joining as a result of receiving the supplement. The target weight for lactating heifers was at least 100 Ib higher than for dry hdfers. The results also indicate specific areas for further research.
Statistical data from the years 1998–2005 were used to investigate the capacity of the grain industry in eastern Australia to supply the grain necessary for inclusion of 10% ethanol in petrol (E10), in addition to the demands of grain for feedlot cattle. Evidence is provided that the variations in grain yields and grain consumption by cattle in these years are representative of the on-going situation and that interpretations and conclusions have continuing relevance. During 1998–2005, annual production of cereal grains in eastern Australia varied between 10 and 25 million tonnes. Similar fluctuations (11 and 27 million tonnes) in annual grain yields were observed between 2006 and 2014. The Australian potential requirement for E10 ethanol is ~2500 ML annually, with a grain usage of 6.1–7.6 million tonnes depending on the grain sources used. Established national grain demand for ruminant and monogastric livestock, human consumption and other domestic uses is ~7.5 million tonnes per year. In years of average or higher grain yields in Queensland, New South Wales, Victoria and South Australia, the combined grain surpluses are more than sufficient for E10 ethanol to be produced domestically. In the years of the lowest grain yields, the surplus over more traditional usages is sufficient to satisfy only 50% of potential demand for E10. The greatest densities of feedlot cattle are in south-eastern Queensland, northern New South Wales and in the Murrumbidgee region of southern New South Wales. On a regional basis, the grain surplus to feedlot demand in most years in south-eastern Queensland is not sufficient to satisfy requirement for ethanol production without competition for grain. In years of highest yields, the grain surplus was sufficient for a 240-ML ethanol plant. Northern New South Wales could support at least two 400-ML plants in years of average and above yields, once established grain demands are met. The grain shortfall in years of lowest yield for one 400-ML plant is about half a million tonnes. Grain surpluses in average years in the Murrumbidgee region are sufficient to support at least one 400-ML plant. In years of lowest yield, only a 160-ML plant could be supported without competition for grain.
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