Barley versus maize as supplements for grazing dairy cows

Date: Oct 2004 Author: Brad Granzin

There is an ongoing debate among dairy farmers, nutritionists and researchers around the world about what is the best energy supplement for grazing dairy cows. To date there has been comparatively little research undertaken in Australia examining this topic. This is surprising given that the typical dairy farm can spend more than $20 000 per year on concentrates.

This article reports on some research carried out at Wollongbar Agricultural Institute, where Holstein-Friesian cows were grazed on either ryegrass or kikuyu pasture and were given a grain supplement of either barley or maize.

How maize and barley grain affect milk production

There have been numerous experiments with feedlot dairy cows comparing how maize and barley grain affect milk production. These studies suggest that the energy available from maize is used more efficiently for milk production than the energy available from barley. This is primarily because the majority of the starch from maize is digested in the intestine, whereas barley starch is predominantly digested in the rumen. A cow can use intestinally digested starch more efficiently for milk production.

Key outcomes of the research at Wollongbar Agricultural Institute

The key outcomes from the research are listed below. It should be noted that the milk production data obtained from these studies were from cows in early lactation. (The data are provided in Table 1 and Table 2.)

  • There were no effects of grain type (maize or barley) on milk yield.
  • Milk fat concentrations were higher in cows fed maize while grazing ryegrass. In this study, cows fed maize had higher rumen concentrations of milk fat precursors — higher ratios of (acetate + butyrate):propionate — than cows fed barley.
  • Across both experiments, milk from cows fed maize had higher concentrations of milk protein. This would appear to be related to the better energy utilisation of rumen bypass starch. Low milk-protein concentrations are often caused by cows using milk protein precursors (amino acids) as an energy source. If a cow doesn’t need milk protein precursors as an energy source, then this increases the availability of these precursors for milk protein synthesis.
  • The low milk-fat concentrations of milk from cows grazing kikuyu were caused by a lack of a particular dietary fibre called acid detergent fibre. This was unexpected, as we normally think that cows grazing kikuyu eat adequate levels of fibre.
  • Grain type had no effect on pasture intake or liveweight change.
  • Calculations show that there is an economic advantage of maize over barley at all feeding levels.

Research details and data

There were two experiments conducted at Wollongbar comparing maize and barley as energy supplements for grazing Holstein-Friesian cows in early lactation:

  • In Experiment 1 (August to October 1999), cows grazed ryegrass pastures. There were 32 cows in this study (four groups of 8).
  • In Experiment 2 (January to March 2001), cows grazed kikuyu pastures. There were 48 cows in this study (four groups of 12).

In both studies, cows were fed either a rolled barley or a rolled maize based concentrate at either 5 kg or 9 kg per cow per day. Both concentrates had the same energy content. Milk production data from these studies is shown in Table 1.

Table 1. Effect of supplement grain type and level of feeding on daily milk production of early lactation cows grazing ryegrass or kikuyu
Barley
(kg/cow/day)
Maize
(kg/cow/day)
Real difference between:
5959Treatments Grain type Feeding level
Ryegrass
Milk (L/cow) 22.0 24.7 22.0 23.6 no no yes
Fat (%) 3.6 3.2 3.9 3.8 no yes yes
Protein (%) 2.8 2.8 3.0 3.0 no yes no
Fat
yield (g)
797 786 845 905 no yes no
Protein
yield (g)
634 700 641 707 no no yes
Kikuyu
Milk (L/cow) 20.1 23.2 20.1 23.9 no no yes
Fat (%) 3.5 3.3 3.7 3.2 no no yes
Protein (%) 2.7 2.7 2.9 2.9 no yes yes
Fat
yield (g)
687 750 719 732 no no yes
Protein
yield (g)
530 627 570 665 no yes yes

Economic benefits

Table 2 describes the economics of these experiments for a base price of 30c per litre (calculated on an average of 4.0% fat and 3.2% protein) and 0.335c per 0.1% plus or minus the difference in either fat % or protein % from this average.

These calculations show an economic advantage of maize over barley at all feeding levels. It shows that based on this pay system you could afford to pay between $28 and $74 more per tonne of maize and still have an economic advantage.

It must be noted, however, that the milk production data from these studies were from cows in early lactation. Whether or not we would see the same changes in milk fat and protein concentrations of cows in mid–late lactation is unknown and requires investigation.

Farmers of course should consider current barley and maize prices, and hence the cost of purchasing grain, versus the return received for each additional litre of milk produced, before deciding on a feeding strategy.

Table 2. Economic analysis of feeding barley-based or maize-based concentrates to cows in early lactation grazing ryegrass or kikuyu
  5 kg/cow/day 9 kg/cow/day
BarleyMaizeBarleyMaize
Ryegrass
Milk (L/cow/day) 22.0 22.0 24.7 23.6
Fat (%) 3.6 3.9 3.2 3.8
Protein (%) 2.8 3.0 2.8 3.0
Cents return/L 27.3 29.0 26.0 28.7
Cents return/cow/day 601 638 642 677
Cents difference in returns between grains at same level of feeding +37 +35
How much more could you afford to pay for maize? ($/tonne) +74 +38
Kikuyu
Milk (L/cow/day) 20.1 20.1 23.2 23.9
Fat (%) 3.5 3.7 3.3 3.2
Protein (%) 2.7 2.9 2.7 2.9
Cents return/L 26.6 28.0 26.0 26.3
Cents return/cow/day 535 563 603 629
Cents difference in returns between grains at same level of feeding +28 +26
How much more could you afford to pay for maize? ($/tonne) +56 +28

Acknowledgment

These experiments were supported by the Dairy Research and Development Corporation.