On Farm Validation of ASKBILL - A Sheep Wellbeing and Productivity Application for Australian Industry

Abstract

Introduction: The most economically important endemic diseases impacting Australian sheep wellbeing and productivity include perinatal mortalities, internal parasites, dystocia, weaner ill-thrift and mortality, and flystrike. Collectively, these diseases cost the Australian sheep industry more than A$1.5 billion per annum (Lane et al. 2015). ASKBILL is a web-based application developed to assist sheep producers to better manage these diseases and thereby improve flock wellbeing and productivity. The ASKBILL application encompasses numerous biophysical models that predict pasture growth, animal performance and risk from flystrike, worm infection and weather stress (Kahn et al. 2017). An important component in the on-going development of ASKBILL is on farm validation designed to allow comparison of measured and predicted values for a range of variables. Experimental design: Validation activity is focused on 11 commercial farms across 3 different production environments: summer rainfall (northern tablelands NSW); winter rainfall (mid-north South Australia and southern NSW); and Mediterranean (south-west Western Australia). Two sheep enterprises are included in all regions: Merino x Merino (MxM; n = 6 farms); and Terminal x Maternal (TxM; n = 5 farms). Within each farm, mixed age single bearing Merino (n=100) or multiple bearing maternal (n = 100) ewes plus female MxM weaners (n = 100) or mixed sex TxM weaners (n = 100) were tagged and monitored. Methods: Ewe live weight, body condition score and dag score were recorded at joining, pregnancy scanning, pre-lambing, lamb marking, and weaning. Weaner live weight and dag score were recorded at approximately monthly intervals from weaning for 7 months unless slaughtered (TxM only) prior. Breech cover, breech wrinkle and fleece rot were estimated using industry visual guides, post-shearing, and mulesing status was recorded. Greasy fleece weight of MxM and TxM ewes and MxM weaners were recorded at shearing and mid-side fleece samples taken and analysed for fibre diameter (FD), cvFD, yield, staple length and staple strength. Ultrasound measurements of C-site eye muscle depth and fat were taken from TxM weaners. Hot standard carcase weight, lean meat yield, intra muscular fat and loin weight were collected on these animals following slaughter. Regular bulk faecal samples were taken from ewe and weaner mobs. A drench resistance test was conducted on each farm and flystrike incidence within mobs was recorded on a weekly basis. Australian Sheep Breeding Values were obtained for sires of weaner sheep and genomic profiling was undertaken. At the beginning and end of the validation period, ewe pregnancy status (single or multiple) was determined via ultrasound scanning. Neonatal and off-shears deaths attributed to exposure were kept. Details of supplements fed were recorded (type, amount, and frequency). Pasture biomass was recorded at approximately 6-weekly intervals. Within each paddock, normalized difference vegetation index (NDVI) and pasture height (cm) were recorded every 2 ha (maximum of 30 measurements per paddock). In addition, 12 quadrats (0.5 × 0.5 m) per farm, were used to collect NDVI and pasture height before being cut to ground level and analyzed to determine dry weights to provide within-property calibration to determine pasture biomass values. On each occasion, composite samples were used for pasture quality. Pasture composition was determined via BOTANAL (Tothill et al. 1978) to estimate the percentage contribution to pasture biomass of the dominant pasture species. Soil chemical fertility was assessed from 20–25 core samples (0–10 cm) per paddock. Rainfall was recorded daily. Analysis: The observed and predicted data will be used to determine the accuracy of model predictions for pasture and animal measures through procedures including regression and analysis of distributions. These data provide a validation data set for modelers to enable adjustment of model functions. They also provide user case studies for industry to assist in the adoption and uptake of the ASKBILL application.