Immediate, cumulative and residual effects of short- and long-term low plane of nutrition on milk protein and casein composition

Immediate and residual effects of two lengths of low plane of nutrition (PON) on the synthesis of milk protein and protein fractions were studied at the Mutdapilly Research Station, in south-east Queensland. Thirty-six multiparous Holstein-Friesian cows, between 46 and 102 days in milk (DIM) initially, were used in a completely randomised design experiment with three treatments. All cows were fed on a basal diet of ryegrass pasture (7.0 kg DM/cow.day), barley-sorghum concentrate mix (2.7 kg DM/cow.day) and a canola meal-mineral mix (1.3 kg DM/cow.day). To increase PON, 5.0 kg DM/cow.day supplemental maize and forage sorghum silage was added to the basal diet. The three treatments were (C) high PON (basal diet + supplemental silage); (L9) low PON (basal diet only) for a period of 9 weeks; and (L3) low PON (basal diet only) for a period of 3 weeks. The experiment comprised three periods (1) covariate – high PON, all groups (5 weeks), (2) period of low PON for either 3 weeks (L3) or 9 weeks (L9), and (3) period of high PON (all groups) to assess ability of cows to recover any production lost as a result of treatments (5 weeks). The low PON treatment periods for L3 and L9 were end-aligned so that all treatment groups began Period 3 together. Although there was a significant effect of L9 on yields of milk, protein, fat and lactose, and concentrations of true protein, whey protein and urea, these were not significantly different from L3. There were no residual effects of L3 or L9 on protein concentration or nitrogen distribution after 5 weeks of realimentation. There was no significant effect of low PON for 3 or 9 weeks on casein concentration or composition.

Immediate and residual effects of heat stress and restricted intake on milk protein and casein composition and energy metabolism

The effects of heat stress on dairy production can be separated into 2 distinct causes: those effects that are mediated by the reduced voluntary feed intake associated with heat stress, and the direct physiological and metabolic effects of heat stress. To distinguish between these, and identify their effect on milk protein and casein concentration, mid-lactation Holstein-Friesian cows (n = 24) were housed in temperature-controlled chambers and either subjected to heat stress HS; temperature-humidity index (THI) ~78 or kept in a THI < 70 environment and pair-fed with heat-stressed cows (TN-R) for 7 d. A control group of cows was kept in a THI < 70 environment with ad libitum feeding (TN-AL). A subsequent recovery period (7 d), with THI < 70 and ad libitum feeding followed. Intake accounted for only part of the effects of heat stress. Heat stress reduced the milk protein concentration, casein number, and casein concentration and increased the urea concentration in milk beyond the effects of restriction of intake. Under HS, the proportion in total casein of αS1-casein increased and the proportion of αS2-casein decreased. Because no effect of HS on milk fat or lactose concentration was found, these effects appeared to be the result of specific downregulation of mammary protein synthesis, and not a general reduction in mammary activity. No residual effects were found of HS or TN-R on milk production or composition after THI < 70 and ad libitum intake were restored. Heat-stressed cows had elevated blood concentrations of urea and Ca, compared with TN-R and TN-AL. Cows in TN-R had higher serum nonesterified fatty acid concentrations than cows in HS. It was proposed that HS and TN-R cows may mobilize different tissues as endogenous sources of energy.

Enzymatic activity other than lipase

In this chapter, enzymes (other than lipase) which are present in cream are discussed. The effects of heat treatments on the activities of these enzymes are described. The influence of residual enzyme activiv, remaining after heating, on cream quality is also discussed.

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. II. Distribution and diet

This study used faecal pellets to investigate the broadscale distribution and diet of koalas in the mulgalands biogeographic region of south-west Queensland. Koala distribution was determined by conducting faecal pellet searches within a 30-cm radius of the base of eucalypts on 149 belt transects, located using a multi-scaled stratified sampling design. Cuticular analysis of pellets collected ffom 22 of these sites was conducted to identify the dietary composition of koalas within the region. Our data suggest that koala distribution is concentrated in the northern and more easterly regions of the study area, and appears to be strongly linked with annual rainfall. Over 50% of our koala records were obtained from non-riverine communities, indicating that koalas in the study area are not primarily restricted to riverine communities, as bas frequently been suggested. Cuticular analysis indicates that more than 90% of koala diet within the region consists of five eucalypt species. Our data highlights the importance of residual Tertiary landforms to koala conservation in the region.

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. IV. Abundance and conservation status

Urban encroachment on dense, coastal koala populations has ensured that their management has received increasing government and public attention. The recently developed National Koala Conservation Strategy calls for maintenance of viable populations in the wild. Yet the success of this, and other, conservation initiatives is hampered by lack of reliable and generally accepted national and regional population estimates. In this paper we address this problem in a potentially large, but poorly studied, regional population in the State that is likely to have the largest wild populations. We draw on findings from previous reports in this series and apply the faecal standing-crop method (FSCM) to derive a regional estimate of more than 59 000 individuals. Validation trials in riverine communities showed that estimates of animal density obtained from the FSCM and direct observation were in close agreement. Bootstrapping and Monte Carlo simulations were used to obtain variance estimates for our population estimates in different vegetation associations across the region. The most favoured habitat was riverine vegetation, which covered only 0.9% of the region but supported 45% of the koalas. We also estimated that between 1969 and 1995 -30% of the native vegetation associations that are considered as potential koala habitat were cleared, leading to a decline of perhaps 10% in koala numbers. Management of this large regional population has significant implications for the national conservation of the species: the continued viability of this population is critically dependent on the retention and management of riverine and residual vegetation communities, and future vegetation-management guidelines should be cognisant of the potential impacts of clearing even small areas of critical habitat. We also highlight eight management implications.

Phosphorus concentrations in the leaves of cotton in tropical Australia are determined by temperature.

Previous research on P leaf analysis for detecting deficiencies in cotton (Gossypium hirsutum L.) has not considered temperature as a determining factor. This is despite correlations between leaf P content and temperature being observed in other crops. As part of research into a new cotton farming system for the semi-arid tropics of Australia, we conducted two P fertiliser rate experiments on recently cleared un-cropped (bicarbonate P < 5 mg kg- 1) and previously cropped (bicarbonate P 26 mg kg- 1) soil. They aimed to develop P requirements and more importantly to determine if temperature affects the leaf P concentrations used to diagnose P deficiencies. In 2002, optimal yield on un-cropped, low P soil was achieved with a 60 kg P ha- 1 rate. In 2003, residual P from the 40 kg P ha- 1 treatment produced optimal yield. On cropped, high P soil there was no yield response to treatments up to 100 kg P ha- 1. On low P soil, a positive correlation was observed between P concentration in the youngest fully-unfurled leaf (YFUL), fertiliser rate, and mean diurnal temperature in the seven days prior to sampling. On high P soil, a positive correlation was observed between the YFUL and mean diurnal temperature however there was no correlation with fertiliser rate. These results show that YFUL analysis can be used to diagnose P deficiencies in cotton, provided the temperature prior to sampling is considered.

Fate of applied biosolids nitrogen in a cut and remove forage system on an alluvial clay loam soil

The fate of nitrogen (N) applied in biosolids was investigated in a forage production system on an alluvial clay loam soil in south-eastern Queensland, Australia. Biosolids were applied in October 2002 at rates of 6, 12, 36, and 54dryt/ha for aerobically digested biosolids (AE) and 8, 16, 48, and 72dryt/ha for anaerobically digested biosolids (AN). Rates were based on multiples of the Nitrogen Limited Biosolids Application rate (0.5, 1, 3, and 4.5NLBAR) for each type of biosolid. The experiment included an unfertilised control and a fertilised control that received multiple applications of synthetic fertiliser. Forage sorghum was planted 1 week after biosolids application and harvested 4 times between December 2002 and May 2003. Dry matter production was significantly greater from the biosolids-treated plots (21-27t/ha) than from the unfertilised (16t/ha) and fertilised (18t/ha) controls. The harvested plant material removed an extra 148-488kg N from the biosolids-treated plots. Partial N budgets were calculated for the 1NLBAR and 4.5NLBAR treatments for each biosolids type at the end of the crop season. Crop removal only accounted for 25-33% of the applied N in the 1NLBAR treatments and as low as 8-15% with 4.5NLBAR. Residual biosolids N was predominantly in the form of organic N (38-51% of applied biosolids N), although there was also a significant proportion (10-23%) as NO3-N, predominantly in the top 0.90m of the soil profile. From 12 to 29% of applied N was unaccounted for, and presumed to be lost as gaseous nitrogen and/or ammonia, as a consequence of volatilisation or denitrification, respectively. In-season mineralisation of organic N in biosolids was 43-59% of the applied organic N, which was much greater than the 15% (AN)-25% (AE) expected, based on current NLBAR calculation methods. Excessive biosolids application produced little additional biomass but led to high soil mineral N concentrations that were vulnerable to multiple loss pathways. Queensland Guidelines need to account for higher rates of mineralisation and losses via denitrification and volatilisation and should therefore encourage lower application rates to achieve optimal plant growth and minimise the potential for detrimental impacts on the environment.