FEED365 Summer Sheep Grazing: Implications for Paddock Management and Grazing Strategies

By Kate Parker, WMG Project Officer

Introduction

A recent grazing period at the FEED365 site in Warradarge was conducted over a 7-weeks from December to January and has provided valuable insights into the weight gain patterns of sheep and the optimal grazing duration for paddocks. The results confirm previous observations from the main FEED365 sites in Katanning and other studies (Clayton EH et al., 2024), where sheep exhibit high growth rates early in the grazing period (initial 3 weeks) that taper off as the trial progresses (last 3 weeks). This decline can be attributed to the gradual reduction in pasture quality and availability over time, leading to sheep walking greater distances to find grazable parts of the paddock. The findings have important implications for farmers seeking to optimise their grazing management to improve livestock productivity while ensuring sustainability in pasture use.

Key Findings

Weight Gain Patterns: The average daily gain (ADG) data reveals distinct patterns across different quartiles of sheep during the grazing trial:

• Quartile 1 (Q1) saw an initial weight gain of 3.38 kg in the first 21 days, but the rate slowed, dropping to -0.57 kg by day 48.
• Quartile 2 (Q2) exhibited consistent growth, starting with 4.00 kg gain in the first 21 days and maintaining a positive ADG throughout the trial period.
• Quartile 3 (Q3) showed a similar trend to Q2 with a notable 4.42 kg gain in the first 21 days, followed by slower gains.
• Quartile 4 (Q4), the heaviest sheep at the start, experienced the highest gains overall, with a 4.81 kg weight gain in the first 21 days, followed by reduced, yet steady, gains throughout the 7 weeks.

On average, all sheep in the trial saw a weight gain of 5.25 kg, with an average ADG of 0.11 kg/day. Notably, the growth rates were highest in the initial 3 weeks (Change 1) and slowed during the last 4 weeks (Change 2).

Grazing Duration and Groundcover: The trial demonstrated that the paddock could be grazed for a total of 7 weeks without compromising groundcover below 50%. The last measurement of groundcover, taken when the sheep were removed, indicated that grazing beyond this period could potentially harm pasture health. This underscores the importance of rotational grazing and managing paddock rest periods to ensure pasture sustainability.

Sheep Weight Distribution: The weight distribution of sheep shifted significantly over the 7-week period. Initially, the majority of sheep were within the 25-35 kg weight range. By the third week, however, the distribution peaked in the 30-40 kg range, and by the seventh week, more sheep had moved into the 40-45 kg range. This trend highlights how quickly sheep can gain weight in optimal grazing conditions, with most of the flock transitioning into heavier weight classes within the first month. The graph also shows a flattening of the distribution meaning the longer the sheep were in the paddock, the more they spread out in the weight ranges.

Implications for Farmers

Early Growth Optimisation: The trial results confirm that sheep experience the most significant growth during the first three weeks of grazing, which is consistent with findings from the Feed365 Katanning trials. Farmers should consider maximising pasture quality and availability during this period to support the rapid growth phase. This could involve pre-grazing management, such as ensuring the paddock is adequately rested and that pasture conditions are favourable.

Paddock Management: Farmers should be mindful of the grazing duration to avoid compromising pasture health. While the trial demonstrated that 7 weeks of grazing did not reduce groundcover below 50%, it is critical to monitor pasture conditions closely. Rotational grazing and early exit strategies are key to maintaining pasture integrity. Overgrazing or extended grazing beyond the optimal period could lead to reduced groundcover and soil degradation.

Weight Gain and Market Readiness: Farmers targeting market-ready sheep should aim to capitalise on the high growth rates in the first 3 weeks of grazing. By adjusting grazing strategies, they can ensure that sheep enter higher weight categories within a short time frame, enhancing overall productivity and profitability.

Limitations of the Study

• Seasonal Variation: The study was conducted during the summer months (December-January), which may not fully represent grazing conditions across different seasons. Future research should explore grazing patterns in cooler months and how pasture regrowth and sheep growth rates are influenced by seasonal changes.
• Pasture Species: The trial was conducted on a barley paddock, which could have a significant impact on sheep performance. Further studies could investigate the effects of different forage species on weight gain and grazing efficiency.
• Sheep Breed and Age: The trial did not account for potential differences in sheep breed or age, which may influence weight gain rates. Future trials could include a broader variety of sheep breeds and age groups to better understand how these factors impact grazing behavior and performance.

Future Research Directions

To build on the findings of this trial, several areas of research warrant further investigation:

1. Pasture Composition and Management: Research into the impact of different pasture species and management practices (e.g., nitrogen fertilisation, irrigation) on weight gain and sustainability could provide valuable insights for farmers.
2. Grazing Strategies and Rest Periods: Further studies on the optimal rest period for paddocks between grazing cycles could help farmers fine-tune their grazing management practices to maintain both livestock productivity and pasture health.
3. Longer-Term Trials: Extending the trial period beyond 7 weeks could provide a better understanding of long-term grazing impacts on pasture condition and sheep performance, especially in diverse environmental conditions.

Conclusion

This trial provides practical insights into the grazing behavior and weight gain patterns of sheep over a 7-week period. While the sheep experienced the most significant growth in the first three weeks, careful management of grazing duration and pasture health is crucial to achieving optimal livestock productivity. The study reinforces the importance of rotational grazing and monitoring groundcover to maintain both sheep growth and pasture sustainability. By incorporating these insights into their grazing strategies, farmers can enhance their sheep production while ensuring long-term pasture health.

References

Clayton EH et al. (2024) Average daily gain in lambs grazing mixed annual forage species compared with single species and relationship to feed on offer. Animal Production Science 64, AN24102. doi:10.1071/AN24102