Grazing Winter Crops – FAQ – 2/3

All this week on Table Talk, we are focusing on the theme of Grazing Crops.

In our first post, we looked at the following questions:

  1. How can cereal grain crops be utilised by livestock?
  2. Does variety matter?
  3. When can I start grazing?
  4. How do I graze? What stocking rate should I use?
  5. When should stock be removed?

Today, we look at:

  1. What is the nutritive value of grazing crops? What growth rates should I expect?
  2. What livestock health issues should I be concerned about?

What is the nutritive value of grazing crops? What growth rates should I expect?

  • Grazing young crops may coincide with the high nutrient requirements of ewes in late pregnancy and lactation.
  • A CSIRO Research paper stated that young crops are highly digestible (>80% dry matter digestibility, DMD) with a high energy density (>12 MJ/kg DM). They also stated that a lower level of feed on offer than would be required with traditional pastures (<500 kg DM/ha). As a result there is a potential to increase whole-farm stocking rates and/or reduce fetal mortality, increase lamb birthweight and survival and improve lifetime production.
  • Grain and Graze3 (GRDC) stated that during winter and early spring when dual-purpose grazing is practised, the quality of cereal forage is extremely high (DM digestibility 80-90%, crude protein 21-26%).
  • NSW DPI stated that residual plant heights of around 5–10 cm for prostrate types and 10–20 cm for upright types will correspond fairly closely to benchmarks of around 1000–1500 kg/ha for lactating ewes and fattening steers.
  • An MLA trial to identify the effect that crop grazing has on ewe condition score (therefore productivity) and crop yield in the Moora-Miling area of WA. They found crop grazing was beneficial to the sheep enterprise, as sheep condition score directly impacts lamb survival, particularly in twin bearing ewes
  • A study in Wagga Wagga sought to sought to identify the advantages of meat production of utilizing dual-purpose wheat for grazing by lambing ewes. They found that FOO at commencement of grazing wheat was low but increased during the period. Even though FOO was below recommendations for temperate pasture, the mean BCS of ewes increased during the period.
  • Phillip Barrett-Lennard of agVivo stated that crops offer significant benefits to livestock due to very high feed quality and feed availability. Very high animal production levels can be achieved as ME levels are consistently in the 12 to 14 MJ/kg range. This compares to the 9 to 11 MJ/kg we have measured in annual pastures.
  • Young sheep grazing dual purpose wheat’s showed significant liveweight gains when supplemented with NaCl (salt) and MgO (eg. Causmag) at a ratio of 1:1 (FarmLink Research through Murrumbidgee Grain & Graze Project (2004-2008))

What livestock health issues should I be concerned about?

  • Pregnancy and lactation are periods of increased susceptibility to metabolic disturbances. The composition of young crops increases this susceptibility. Most young crops (except canola) also have a tetany index >2.2, indicating a high risk of grass tetany (CSIRO Research paper)
  • MLA, UWA and Murdoch University research estimated that the current cost of increased mortality in pregnant ewes resulting from grazing crops is approximately $15,700,000 pa. This is likely to be a significant underestimate of the benefits from providing fail safe grazing strategies.
  • Risks of metabolic disturbance are higher for sheep grazing wheat than other young cereals. Preliminary evidence indicates risks are higher when grazing cereal crops in NSW, Vic and SA than in WA (MLA, UWA and Murdoch University)
  • Wheat forage at this time is commonly deficient in sodium and may also be deficient in magnesium; supplementation with these elements is a cheap and effective insurance policy. (Grain and Graze3 (GRDC))
  • Consultants and producers indicated there is uncertainty around the benefits of mineral supplements. Producers using recommended supplements have still reported metabolic disease and mortality. In some cases, these supplements may even exacerbate the mineral imbalance problems in late pregnancy. The research concluded that:

“Management of ewes grazing cereals in is largely by trial and error as there has been limited evaluation of different grazing strategies.” (MLA, UWA and Murdoch University)

In our final post, well will look at the following questions:

  1. Does grazing winter crops reduce grain yield?
  2. Have any cost benefit analyses been done?
  3. What else should be considered?