Grazing winter crop stubbles

 

How to best use this valuable feed source

 

With dry conditions across the Victoria’s south west, effectively managing crop stubbles is important in helping maintain livestock condition and preserve soil health.

 

By Jessie Wettenhall, Research & Extension Officer, with the Vic Hub’s South-West Node, Southern Farming Systems

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As harvest is wrapping up for many, mixed farming producers may be looking to graze their winter crop stubbles. These can be a valuable source of feed, primarily from residual grain and green shoots from shot grain, weeds or green shoots from spring rains. The standing straw and trash will have a much lower feed quality (both energy and protein) which is below maintenance requirements for all classes of livestock. Therefore, animal weight gain is directly linked to the amount of grain and green material in the stubble.

 

Assessing the amount of grain and green

Research indicates there needs to be at least 40 kilograms a hectare of residual grain or 40kg/ha of green material for a sheep to maintain or gain weight. Below these values, animals lose weight, irrespective of how much straw or leaf trash remains. If either threshold is exceeded, livestock should continue to gain weight.

Table 1 provides a simple guide to help assess the amount of grain in stubble, along with photos of different levels of green materials. It involves using a 0.1m² (32x32cm) quadrat and counting the number of grains and green shoots.

 

Table 1. Cereal grains and green shoot counts needed for kg per hectare.
Number of cereal grains/0.1m2 and approx. quantity of grain/ha		Number of cereal green shoots/0.1m2 and approx. quantity of green/ha as dry matter
Grains counted (number/0.1 m2)	Equivalent quantity of grain (kg/ha)	Green shoots counted (number / 0.1m2)	Equivalent quantity of DM (kg/ha)
6	20	7	20
13	40	14	40
20	60	21	60
26	80	28	80

 

The equivalent of 40kg/ha for crop legumes is approximately four grains per quadrat for lupins, two for field peas and chickpeas and one for faba beans. See Image 1.

Image 1: Indication of green shoot material available for grazing.

 

Variation in stubble value

The value of stubble can vary greatly between crop types and grain vs green (see Table 2). Always compare the feed value to the sheep’s minimum daily requirements (e.g. a 50kg adult dry sheep required 7 megajoules of metabolisable energy (MJ ME) per day and 6% crude protein).

The best way to determine feed quality is with a feed test. However, it can be difficult to measure accurately due to the variability across paddocks and to obtain a sample of what animals are eating.

 

Table 2. Feed value of common stubbles/grains (grain and graze)

	Wheat and barley stubble			Oats
Feed value	Grain	Green	Straw	Grain	Loose trash
Dry matter digestibility (%)	82–87	59–73	38–40	–	40–41
Metabolisable energy (MJ / kg DM)	12.7–13.2	8.5–11.0	5.0–5.3	9.0–11.0	5.3
Crude protein (%)	9.5–13.5	15.9–18.7	1.2–2.8	6.0–12.0	2.0–4.0

 

Supplementary feeding

Supplementary feeding can extend the grazing time of stubbles by helping sheep reduce weight loss as stubbles become depleted and increase the utilisation of low-quality stubble forage.

Providing high protein supplements such as lupins or peas will help sheep meet their protein requirements when grazing cereal stubbles. Table 3 shows the nutritional value of a range of supplementary feeds in comparison to sheep requirements (see “Grazing modern stubbles” at the end of this article).

 

Table 3

Feed		Metabolisable energy (MJ/kg)	Crude protein (%)	Fibre (% ADF)
Grain	Wheat	13	11	3
	Barley	12	11	8
	Oats	11	9	18
	Lupins	14	38	20
	Canola	16	22	24
Hay	Cereal	9	9	29
	Pasture – early cut	10	14	28
	Pasture – late cut	9	10	32
Chaff (Excl. main stems and grains)	Wheat	6.0	4.5	45
	Barley	6.3	5.5	42
	Lupins	7.0	6.5	42
	Canola	6.0	5.0	47
Sheep requirements (for maintenance)	Dry adult ewes	7.1-8.0*	8	~15
	Mid pregnancy (100 days) – single	9.9**	10	~15
	Mid pregnancy (100 days) – twin	11.1**	11	~15
	Weaners (20kg) growing at 50g***	6.5-7.5	11-13	~15

* Lower value condition score two, higher value condition score three.

** Condition score three ewes.

*** Minimum acceptable rate of growth for 20kg animals.

 

When to graze?

The best time to graze is straight after harvest as the feed quality will decrease over time. Stock should be removed once grain and green shoots fall below 40kg/ha. Grazing should be conducted to retain between 50% and 70% groundcover to avoid wind erosion or decrease water infiltration.

Grazing duration

The grazing duration of a paddock varies widely due to numerous factors:

• crop type
• summer rain
• growing season conditions (crop yields, frosts)
• stocking rate
• harvesting conditions (header grain losses)
• weed burden
• paddock conditions

 

However, the general guide from Vic Hub partner Agriculture Victoria is that stock should be removed from the stubble paddock after 6 weeks.

 

Note: This piece is adapted from ‘Insights from the Grain and Graze program’, written by the SW Node’s Cam Nicholson.

 

Additional information:

Sheep nutritional requirements when grazing stubbles – Agriculture Victoria

Five tips for grazing sheep on stubbles – MLA

Grazing modern stubbles – MLA