Critically endangered Pristis microdon (Elasmobranchii), as a host for the Indian parasitic copepod, Caligus furcisetifer Redkar, Rangnekar et Murti, 1949 (Siphonostomatoida): New records from northern Australia.

This paper presents the first records of the parasitic copepod Caligus furcisetifer Redkar, Rangnekar et Murti, 1949 beyond Indian waters, specifically, on the body surface and head of the critically endangered largetooth sawfish (commonly referred to as the freshwater sawfish in Australia), Pristis microdon Latham, 1794 (Elasmobranchii, Pristidae), in brackish tidal waters of the Fitzroy River in the Kimberley region of Western Australia and the Leichhardt River in the Gulf of Carpentaria in northern Queensland. This represents a geographic range extension of similar to 8000 km for this parasite. Further, it is only the second member of the genus Caligus to be found on an elasmobranch host in Western Australia and it is the first time this species has been reported from the Southern Hemisphere. Male biased dispersal of P microdon may be the vector in which the parasite has dispersed from India across to northern Australia, or vice versa. A decline in populations of the critically endangered P microdon (and possibly other pristid species) in these regions may lead to a concomitant decline in their parasite fauna.

Estimating daily methane production in individual cattle with irregular feed intake patterns from short-term methane emission measurements

Spot measurements of methane emission rate (n = 18 700) by 24 Angus steers fed mixed rations from GrowSafe feeders were made over 3- to 6-min periods by a GreenFeed emission monitoring (GEM) unit. The data were analysed to estimate daily methane production (DMP; g/day) and derived methane yield (MY; g/kg dry matter intake (DMI)). A one-compartment dose model of spot emission rate v. time since the preceding meal was compared with the models of Wood (1967) and Dijkstra et al. (1997) and the average of spot measures. Fitted values for DMP were calculated from the area under the curves. Two methods of relating methane and feed intakes were then studied: the classical calculation of MY as DMP/DMI (kg/day); and a novel method of estimating DMP from time and size of preceding meals using either the data for only the two meals preceding a spot measurement, or all meals for 3 days prior. Two approaches were also used to estimate DMP from spot measurements: fitting of splines on a 'per-animal per-day' basis and an alternate approach of modelling DMP after each feed event by least squares (using Solver), summing (for each animal) the contributions from each feed event by best-fitting a one-compartment model. Time since the preceding meal was of limited value in estimating DMP. Even when the meal sizes and time intervals between a spot measurement and all feeding events in the previous 72 h were assessed, only 16.9% of the variance in spot emission rate measured by GEM was explained by this feeding information. While using the preceding meal alone gave a biased (underestimate) of DMP, allowing for a longer feed history removed this bias. A power analysis taking into account the sources of variation in DMP indicated that to obtain an estimate of DMP with a 95% confidence interval within 5% of the observed 64 days mean of spot measures would require 40 animals measured over 45 days (two spot measurements per day) or 30 animals measured over 55 days. These numbers suggest that spot measurements could be made in association with feed efficiency tests made over 70 days. Spot measurements of enteric emissions can be used to define DMP but the number of animals and samples are larger than are needed when day-long measures are made.