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Feeding cows and calves this winter

The winter months on the Tablelands present challenging conditions for both pastures and livestock. Pasture growth is severely restricted by low temperatures and livestock performance is being restricted by the lack of height in our pastures. So, how much additional feed do you need to provide? To answer this question you need to think through a range of factors including the quantity and quality of pasture available, condition of the cow and the level of animal performance you’re targeting.

How big is the nutritional ‘gap’?

The nutritional ‘gap’ is the difference between the animal’s daily nutrient requirement and how much it can obtain out of the pasture being grazed. Figure 1 shows how energy requirements for a 550kg breeding cow change throughout the year. As can be seen, nutrient requirements increase dramatically during the last 3-4 weeks of pregnancy and continue to climb until the cow hits peak lactation, which is around 8 weeks after calving.

Figure 1: Energy requirements of 550kg British Breed Cow – unrestricted feed (calving 1 August)

Figure 1: Energy requirements of 550kg British Breed Cow – unrestricted feed (calving 1 August)

Source: Jeff House 2016

While pasture quality is generally very good during the winter months (i.e. digestibility of 70% +), it’s the lack of height that restricts intake and performance. If your pasture is very short (i.e. 1.0 – 1.5cm in height) it’s likely that your cattle are only getting around half of their daily energy and protein requirements. If a supplement isn’t provided the end result is significant weight loss in the cow, reduced milk supply during lactation and increased risk of cows not getting back in calf.

What supplement do I use and how much do I feed?

Energy is generally the biggest limiting factor when cattle are grazing short green feed – the quality of the pasture is high but intake is restricted by the lack of height. At present there is quite a big variation across the region in terms of the amount of pasture in paddocks. The critical thing to remember is that a small increase in pasture height has a big impact on animal intake and performance, so it’s important to have a close look at what your stock are grazing.

Paddock feed is 2cm or less…

Feeding cows in late pregnancy/early lactation with high quality supplements (e.g. clover or lucerne hay, good quality silage, cereal grain, pellets, dried distillers grains etc.) becomes increasingly important when cattle are grazing very short grass (i.e. 2cm or less). Refer to Table 1 for recommended feeding rates if this is your situation.

Paddock feed is more than 2cm…

Once pasture reaches around 2cm and above, daily energy and protein needs can simply be met by feeding a good quality hay. This of course is assuming that the pasture being grazed is of good quality and highly digestible (70% + digestibility). Refer to Table 2 for recommended feeding rates where pasture is in the 2cm – 5cm range.

Note: The feeding recommendations in Table 1 and 2 are assuming cattle are grazing a short green pick that is highly digestible (i.e. minimal dead herbage in the paddock). If cattle are consuming a significant amount of dead carry-over material  intake will be limited by poor digestibility. In this situation feeding a concentrate that is high in both energy and protein will be required to aid digestion and ensure livestock performance is not compromised.

Other limiting nutrients

A number of herds across the region have already been hit with grass tetany (hypomagnesaemia). Conditions of late have been perfect for this nutritional disorder – cows grazing short, grass dominated pastures under cold, wet, overcast conditions. Cows in the first 6-8 weeks of lactation are most prone to the disorder.

Unfortunately magnesium can’t be stored in the body and therefore some form of supplement is required. This can be done in a number of ways:

  • magnesium lick blocks
  • loose licks in the paddock. These can be either purchased or made on farm. Home made options include:
    • a 1:1:1 ratio of magnesium oxide (e.g. Causmag®), lime and salt; or
    • a mix of magnesium oxide, salt and an attractant like dried distillers grains to help improve palatability and intake
  • treating grain or pellets with magnesium oxide
  • feeding ethanol syrup treated with magnesium oxide (20kg bag of Causmag added to 1000L of DDG syrup). Syrup is fed in tubs ad lib.
  • feeding hay treated with magnesium oxide
  • magnesium capsules

Feeding hay treated with magnesium oxide (e.g. Causmag) is generally the preferred option as magnesium intake tends to be more even across the mob (intake can be highly variable between animals when using blocks or loose licks). When treating hay the recommended rate is 60-100g of Causmag/cow/day.

Further information:

Additional comments:

First calf heifers and cows in backward condition (i.e. fat score 2.5 or less) are the highest priority and need to be carefully managed to ensure they get back in calf. The objective here is to maintain cow condition in the lead up to calving and allocate to the best pasture available post calving.

If your cows are in good condition in the lead up to calving (e.g. fat score 3.5 +) you could save on feeding costs by letting your cows undergo slight weight loss. The aim should be to calve down in fat score 3 (a fat score is equivalent to 50-80kg). Research shows that cow condition at calving has a major impact on how quickly she is able to recover and get back in calf.

If you are purchasing feed it’s important that you either ask for a feed test result or request that a test is done. This way you know exactly what you’re getting for your money. Once you have these details you can compare feeds on an energy and/or protein basis via the NSW DPI feed cost calculator.

The NSW DPI also has Drought Feed Calculator which can be downloaded as an App on your smartphone.

Pre-calving is also an opportune time to administer your annual 5-in-1 or 7-in-1 booster shot. Vaccinating pregnant stock 4 weeks before calving not only provides ongoing protection for the cow, but it also enables passive immunity to be passed on to the newborn calf via the colostrum.

Table 1 Supplementary feeding options for winter calving grazing a short green pick that is 2cm or less

Table 1 Supplementary feeding options for winter calving herds grazing a short green pick that is 2cm or less

Figures in Table 1 have been calculated using Grazfeed. The assumptions are:

  • British breed cattle, 550kg mature cow weight (fat score 3)
  • Cows are grazing a very short green pasture - 600kg DM/ha; 1.2 – 1.5cm in height. Pasture is 72% digestibility and contains 5% legume
  • Cereal grain is 13 ME and 11% protein. This is fed with average quality hay (8.5 ME; 7% protein). Energy and protein values for other feedstuff are provided.

Table 2 Supplementary feeding options for winter calving herds grazing geen pasture that is 2cm – 5cm in height

Table 2 Supplementary feeding options for winter calving herds grazing geen pasture that is 2cm – 5cm in height

*Figures in the table have been calculated using the decision support tool Grazfeed. The assumptions are:

  • British breed cattle (550kg mature cow weight; fat score 3) grazing green pasture at 72% digestibility, 5% legume with pasture height varying from 2cm - 5cm.
  • The hay fed is of good quality (9 MJ ME and 8% protein).

Important note: Feeding rates presented in Table 1 and Table 2 are ‘as fed’ amounts and should be viewed as a guide only. These rates do not account for wastage or the impact of cold weather. Feeding levels should be increased by 20% during severe weather (i.e. wind + rain + cold)