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van Wettere W.H.E.J.,University of Adelaide | Mitchell M.,University of Adelaide | Revell D.K.,University of Adelaide | Revell D.K.,Center for Environment and Life science | Hughes P.E.,Pig and Poultry Production Institute
Theriogenology | Year: 2011

The objective was to investigate the effects of moderate restriction of pre- and peri-pubertal liveweight gain on ovarian development and oocyte meiotic competence. At 70 d of age, and 27.7 ± 0.4 kg liveweight (LW), 64 Large White/Landrace crossbred gilts were allocated to two treatment groups (n = 32 gilts/treatment); one group was fed to attain a LW of 70 kg at 161 d of age (LIGHT), while the other group was fed to reach 100 kg LW (HEAVY). At 161 d of age, half of the gilts in each group (n = 16) were fed to gain LW at 0.5 kg/d (LOW), while the remaining half (n = 16) were fed to gain LW at 1.0 kg/d (HIGH) between 161 and 175 d of age, at which point they were killed and ovaries collected. For each gilt, surface antral follicles were counted and aspirated according to three size categories: 1-2.9 mm (small); 3-6 mm (medium); and > 6 mm (large). Follicles were pooled for each size class and treatment. Cumulus-oocyte-complexes (COC) recovered from small and medium follicles were matured in vitro (IVM) for 44 to 46 h, and meiotic maturation assessed. There was an effect of treatment (LIGHT versus HEAVY) on the number of medium sized follicles: 25.1 ± 2.59 versus 34.3 ± 2.60 (P < 0.05). The ovaries of LOW gilts had more small follicles and fewer medium follicles compared to those of HIGH gilts: 92.8 ± 8.35 versus 59.8 ± 5.24, and 25.1 ± 2.59 versus 32.5 ± 2.86 (P < 0.05). Target LW at 161 d did not affect meiotic progression of oocytes. However, LOW compared to HIGH LW gain between 161 and 175 d resulted in fewer oocytes reaching MII (0.40 versus 0.54; P < 0.05). In conclusion, moderately restricting feed intake impaired follicle growth beyond 3 mm and reduced oocyte meiotic competence. Further, although a carry-over effect of long-term feed restriction on follicle growth was evident, acute changes in feed intake during the 14 d prior to ovary collection had the greatest effect on oocyte nuclear maturation in vitro. © 2011 Elsevier Inc.

Robertson M.,CSIRO | Robertson M.,Center for Environment and Life science | Shen Y.,Lanzhou University | Philp J.,University of Western Sydney | And 16 more authors.
Grass and Forage Science | Year: 2015

The current promotion of larger areas of lucerne (Medicago sativa) production on the Loess Plateau in China prompted this study, which investigated lucerne harvesting practices by farmers and the scope for improved harvest yield and quality by optimizing harvest date, interval and height above ground. On-farm surveys were conducted to document the dominant harvesting practices used by farmers and their perceptions of barriers to adoption of alternative harvesting practices. In districts with less emphasis on livestock, less labour and inadequate facilities to store conserved lucerne, smaller areas of lucerne are grown and it is often harvested daily to meet demand from penned livestock. The consequence is that much of the lucerne is harvested either before or after flowering, resulting in suboptimal yield of biomass and crude protein. Field experiments conducted at low and high rainfall locations on the Loess Plateau over three seasons showed that delaying the start to harvest until after mid-June (the date of first flowering), while not affecting total biomass harvested for the season, does reduce leaf biomass harvested and hence crude protein concentration and yield. Lower crude protein is a consequence of a decline in both leaf percentage in harvested biomass and stem nitrogen concentration. Commencing harvests well before flowering with short (3 week) harvest intervals also penalized total and leaf biomass harvested. Raising cutting height from ground level (current farmer practice) to 50 mm (likely with the advent of mechanized harvesting) did not penalize harvested total or leaf biomass. © 2014 John Wiley & Sons Ltd.

Douglas G.B.,Center for Environment and Life science | Kuhnen M.,Australian National University | Radke L.C.,Geoscience Australia | Hancock G.,CSIRO | And 7 more authors.
Environmental Chemistry | Year: 2010

Environmental context. Undisturbed sediments provide a record to past events in a catchment. In this study we examine changes in sources of sediment and their variation over the past century due to changes in climate and extensive modification of the catchment after European settlement. We also highlight how multiple lines of forensic evidence acquired from the sediments can be used to reconstruct catchment history over a range of timescales. Abstract. Enhanced delivery of sediment and nutrients to the Great Barrier Reef has the potential to profoundly influence ecological processes in this natural icon. Within the Fitzroy River Basin (FRB) of north-eastern Australia, natural impoundments such as Crescent Lagoon provide an invaluable archive of accumulated sediment that can be dated using multiple techniques to reconstruct the history of sediment export. During the last century, net rates of accumulation of sediment remain similar; however, large variations in sediment sources are apparent. A major sedimentary and geochemical discontinuity is present between ∼45 to 29 years before present. Within this time interval a redox front is preserved corresponding to a change in organic matter influx; C3 plant detritus derived from the onset of broadscale agriculture within the FRB provided an assimilable carbon source resulting in more reducing conditions within the sediments. Statistical correlations demonstrate a notable correspondence between some sediment fractions supporting the notion of a short-lived disturbance to the sedimentation regime in the 1960-70s. © 2010 CSIRO.

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