Cameron Edward Fisher Clark

Accurate pasture biomass (PB) estimation is critical for tactical grazing management, yet traditional satellite-derived vegetation indices such as Normalised Difference Vegetation Index (NDVI) saturate when canopy density exceeds about 3 t DM ha⁻¹. This limits predictive accuracy because the spectral signal plateaus under dense vegetation, masking further biomass increases. To address this limitation, this study integrated multiple data sources to improve PB estimation in dairy systems. The dataset combined Sentinel-2 spectral bands, rising plate-meter (RPM) PB measurements, daily weather data, and paddock management features. A total of 3161 paired RPM–satellite observations were collected from 80 paddocks across 16 New South Wales dairy farms between November 2021 and July 2024. Eight regression algorithms and four predictor configurations were evaluated using robust cross-validation, including an 80:20 farm/paddock-stratified train–test-set split. The XGBoost model using full-band reflectance and concurrent weather data achieved strong baseline performance (R² = 0.63; MAE = 243 kg DM ha⁻¹) on non-interpolated data, outperforming NDVI-based models. To address temporal gaps between field readings and satellite imagery, Multiquadric interpolation was applied to RPM data, adding roughly 30% new observations. This enhanced dataset improved test performance to R² = 0.70 and MAE = 216 kg DM ha⁻¹, with gains maintained on external validations (R² = 0.41/0.48; MAE = 267/235 kg DM ha⁻¹). A progressive training strategy, which refreshed model parameters with seasonally aligned data, further reduced errors by 30% compared to static models and sustained performance even when farms or seasons were excluded. This fortified Sentinel-2 modelling workflow, combining RPM interpolation and progressive calibration, achieved accuracy comparable to the commercial Pasture.io platform (R² = 0.66; MAE = 240 kg DM ha⁻¹) which uses satellite imagery with higher temporal and spatial resolution, demonstrating potential for automated recalibration and near real-time, paddock-level decision support in pasture-based dairy systems.

Disbudding is a husbandry practice that causes pain and discomfort to calves. As a prominent welfare concern, it is now standard practice for calves to be given analgesic treatment such as a nonsteroidal anti-inflammatory drug (NSAID) injection. Meloxicam is a commonly used NSAID as it provides pain relief for up to 44 h following disbudding. However, since symptoms can persist for up to two weeks, it was hypothesised that more prolonged analgesic treatment would promote better welfare outcomes than the conventional injection. This study tested a novel treatment whereby disbudded calves were fed grain-based pellets medicated with meloxicam over a 7-day period. Lower levels of horn site inflammation were observed for the pellet treatment across the 7-day feeding period in comparison to the conventional injection. The pellet treatment calves also exhibited less pain-specific and more positive social-specific behaviours during and beyond the feeding period. Together, these results suggest that lower levels of inflammation enacted by prolonged meloxicam administration have an active role in reducing pain and maintaining the affectivity of disbudded calves. With the goal of establishing sustained disbudding treatment as a new industry standard, future research will focus on larger-scale results reproducibility and maximising treatment practicality.

Napier grass is widely used across the tropics and subtropics as a feed for dairy and beef cattle, but its quality is poor under current management with resultant poor animal productivity. Current management is focused on achieving high yields and, as such, is harvested at ground level with longer harvest interval when grass reaches 200 cm or higher, which reduces quality. The opportunity to improve the nutritive value of this grass is largely unexplored alongside the opportunity to increase livestock productivity and food security in the tropics and subtropics. Here we determined the impact of leaf number (total) or stage (LS; 6, 9 and 14) at harvest, and harvest severity height (SH; cutting or harvest height from the ground; 5, 10 and 20 cm), on the nutritive value of Napier grass (cv. Pakchong) across one year. Napier grass was sown (from cutting) at a density of 50 cm × 50 cm with three replicates per treatment. Increasing LS from 6 to 14 decreased crude protein (CP) content from 184 g/kg DM to 118 g/kg DM and metabolizable energy (ME) content from 10.4 to 7.3 MJ/kg DM. These results suggest that Napier grass should be harvested at a lower LS to increase plant nutritive value but there was a trade-off between yield and quality as yield decreased by half to improve such quality. The impact of offering Napier grass harvested at 6, 9 or 14 LS on cattle growth was then determined across 113 days in a second experiment. Red Chittagong bulls were enrolled at a weight of a 181.9 ± 2.30 (Mean ± SE) Kg with an age of between 18 and 22 months. The 6 LS treatment cattle had a greater growth rate and higher feed conversion ratio (FCR) than the 14 LS treatment (610 versus 270 g/day and 6.4 versus 16.2, respectively) indicating a trade-off of yield with quality. Our results demonstrate that Napier grass should be harvested at 6 LS with 10 cm SH for feed nutritive value, cattle growth and FCR. Further research is required to ameliorate yield loss associated with this recommended management strategy with a focus on increasing plant density.

Napier grass is widely used across the tropics and subtropics as a feed for dairy and beef cattle, but its quality is poor under current management with resultant poor animal productivity. Current management is focused on achieving high yields and as such is harvested at ground level with longer harvest interval when grass becomes 200 cm or higher, which reduces quality. The opportunity to improve the nutritive value of this grass is largely unexplored alongside the opportunity to increase livestock productivity and food security in the tropics and subtropics. Here we determined the impact of three Napier grass (cv. Pakchong) leaf number (total) or stage (LS; 6, 9 and 14) at harvest, where, 14 LS represents current management practice and three severity height (SH; cutting or harvest height from the ground; 5, 10, and 20 cm) on nutritive value of Napier grass throughout the year. Napier grass was sown (from cutting) at a density of 50 cm x 50 cm with three replicates per treatment. Increasing LS from 6 to 14 decreased crude protein (CP) content from 184 g/kg DM to 118 g/kg DM and metabolisable energy (ME) content from 10.4 to 7.3 MJ/kg DM These results suggest that Napier grass should be harvested at a lower LS to increase plant nutritive value but there was a trade-off between yield and quality as yield decreased by half to improve such quality. The impact of offering Napier grass harvested at 6, 9 or 14 LS on cattle growth was then determined across 113 days in a second experiment. Red Chittagong bulls were enrolled at a weight of a 181.9 ± 2.30 (Mean ± SE) Kg with an age of between 18 and 22 months. The 6 LS treatment cattle had a greater growth rate and lower feed conversion ratio (FCR) than the 14 LS treatment (610 versus 270g/day and 6.4 versus 16.2, respectively) indicating a trade-off of yield with quality. Our results demonstrate that Napier grass should be harvested at 6 LS for feed nutritive value, cattle growth and FCR. Further research is required to ameliorate yield loss associated with this recommended management strategy with a focus on increasing plant density.

This study suggests that by monitoring calves' consumption and visitation frequency using automated calf feeders on day 5, farmers can identify underperforming calves early, allowing for timely intervention to boost their growth potential. Additionally, calves exhibiting higher milk consumption and increased interaction with the feeder during the first 5 days are more likely to achieve a weaning weight exceeding 75 kg.This highlights an opportunity for management intervention in cases where calves fall below these consumption and interaction thresholds.

The impact of abrupt (AB) and fenceline (FL) weaning methods on cattle stress response, live weight gain, and behaviour were determined across 14 days. Thirty-two cow–calf pairs were fitted with ear tag sensors (to continuously record behaviour) and allocated to two weaning treatments. After separation, FL calves were maintained in a pen adjacent to the FL cow paddock. The AB calves were transported to a pen removing all contact with the cows. After 7 d, FL cows were transported away from all calf pens. Body weights and salivary samples were collected for all animals on experimental days 0, 7, and 14. Fenceline-weaned calves had a greater duration of rest and rumination with reduced high activity across the first 3 days after separation as compared to abruptly weaned calves in line with the greater occurrences of pacing observed for AB calves. Fenceline-separated cows had greater levels of rest across the first 7 days but similar levels of rumination compared to abruptly separated cows. Fenceline-separated cow activity levels tended to be greater and eating levels were similar across the first three days. Body weight (BW) and cortisol concentrations were similar for AB and FL cattle, but FL cows had lower overall weight gain than the abrupt cows likely due to reduced eating time on days four to seven. Together, these results suggest that calves be fenceline-weaned for three days followed by total separation.