The key principles of feeding concentrates to growing-finishing cattle

With an indoor winter period required on practically all Irish farms, Mark McGee and Edward O’Riordan, Teagasc Grange, share principles on concentrate feeding – a key component of beef production systems.

Energy

Energy is the most important nutrient required by growing-finishing cattle. Comparisons of feedstuffs should always be based on their net energy (and protein) concentrations on a dry matter (DM) basis. It is important to ensure that an adequate level of an appropriate mineral/vitamin mix is included in the ration.

Dry matter digestibility

Dry matter digestibility (DMD) is the primary factor influencing the nutritive value of forage. Consequently, the performance of beef cattle increases with increasing grass silage DMD and the impact of DMD increases as the proportion of silage in the diet increases. For example, in finishing cattle, a one-unit increase in silage DMD was associated with an increase in carcass gain of 21–29 g/d when supplemented with concentrates at 0.20–0.40 of dietary DM intake, but when no concentrates were offered and silage intake was higher the response was greater (33 g/d).

Low DMD forages require higher levels of concentrates to achieve the same growth rate (Table 1). For example, each one-unit decline in DMD of grass silage requires an additional 0.3 to 0.4 kg concentrate daily to sustain performance in finishing cattle. Consequently, providing high-DMD silage for growing/finishing cattle is important.

Target animal growth rates during the first winter and during finishing can be achieved on grass silage supplemented with concentrates as outlined in Table 1.

Table 1: Concentrate supplementation (kg/day) necessary for weanlings to grow at ~0.5 kg and for finishing steers (600 kg) to grow at ~1.0 kg live weight/day, when offered grass silage of varying dry matter digestibility (DMD) to appetite

Ad-lib feeding

When feeding concentrates ad libitum, particularly cereals, there is a risk of acidosis. Therefore, ensure; (i) gradual adaptation to concentrates (over ~3 weeks), (ii) minimum roughage inclusion (~10% of total DM intake) for rumen function, (iii) meal supply never runs out and, (iv) a constant supply of fresh water is provided.

Response to concentrate feeding

Growth response to concentrate feeding is higher in ‘high-growth potential’ animals. Efficiency of feed utilisation by finishing cattle primarily depends on the live weight of the animal (decreases as live weight increases), potential for carcass growth (e.g. breed type, gender, compensatory growth potential) and duration of the finishing period (decreases as length increases). For example, in terms of breed type, research at Teagasc Grange found that, at the same age, Holstein-Friesian steers offered a high-concentrate diet, were lighter, grew more slowly and consumed 10% more feed DM resulting in a 20% inferior feed efficiency compared to suckler-bred Charolais steers. Similarly, bulls are 10 to 20% more feed efficient than comparable steers and heifers.

The optimum level of concentrate supplementation primarily depends on animal production response (kg gain/kg concentrate), forage substitution rate and the relative prices of animal product at sale and feedstuffs.

Compensatory growth

Subsequent compensatory growth (‘catch-up’) at pasture diminishes the advantage of excessive concentrate supplementation of young ‘weanling’ cattle offered grass silage. Research at Teagasc Grange has shown that live weight gains of 0.5 to 0.6 kg/day through the ‘first’ winter are acceptable for steers, heifers and suckler bulls destined to return to pasture in spring. This feeding regime also applies to older ‘store’ cattle in their second winter destined for subsequent finishing at pasture. However, higher level of feeding is generally warranted during the first winter for replacement beef heifers, who have heavier threshold weight targets to achieve earlier in life. Conversely, cattle growing too slowly during winter (<0.5 kg/day) will not be able to compensate sufficiently at pasture, and consequently, will not reach target weights later in life.><0.5kg/day) will not be able to compensate sufficiently at pasture and consequently will not reach target weights later in life.

Substitution rate

Increasing the level of concentrates in the diet reduces grass silage intake but increases live and carcass weight gains, although at a diminishing rate (i.e. curvilinear response) especially when high-DMD silages are offered.

The substitution rate of concentrates for grass silage (i.e. kg reduction in forage DM intake per kg concentrate DM intake) is a function of silage digestibility, and concentrate feed level – it increases with an increase in both. Animal production response to concentrate supplementation is higher with forages of lower DMD. Increasing the level of concentrate supplementation reduces the importance of forage nutritive value, especially when feeding concentrates ad libitum. Where silage DMD is poor (e.g. 60%) or in short supply, and animal growth potential is high, feeding concentrates ad libitum should be considered.

Energy and protein sources

Research at Teagasc Grange has shown that equivalent animal intake and performance is obtained from concentrate rations containing contrasting energy sources (e.g. rapidly-fermentable starch vs. slowly-fermentable starch vs. ‘digestible’ fibre-based), offered as a supplement to grass silage or ad libitum with silage, provided that they are formulated to the same net energy (and protein) concentration.

Teagasc Grange research has also shown that weanling and finishing steers and heifers generally do not require protein supplementation when fed barley-based concentrates and high DMD grass silage, but for suckler bull weanlings, a significant, but small, response to protein supplementation occurred. However, weanling and finishing cattle are likely to respond to supplementary protein in barley-based concentrates when grass silage has moderate to low DMD and/or low protein content.

Concentrate feed ingredients

The primary role of concentrates is to redress the deficit in nutrient supply from forages to allow cattle reach performance targets. In particular, beef cattle rarely consume sufficient grass silage to achieve their production potential and as a result, energy-rich concentrates are routinely supplemented in practice.

Cereals, which make up a substantial proportion of beef ration formulations, are usually supplemented with higher protein-rich feed ingredients to satisfy assumed animal protein requirements.

Ireland has a significant deficit in concentrate feed ingredients and most of the feedstuffs used nationally, especially protein sources, are imported. In order to increase self-sufficiency nationally, there is growing interest in increasing the proportion of ‘home-grown’ feeds, both ‘native’ grains and proteins in livestock rations used in Ireland.

At Teagasc Grange, the ‘standard’ concentrate offered in most beef production system studies contains 862 g rolled barley, 60 g soya bean meal, 50 g molasses, 28 g minerals and vitamins per kg fresh weight fresh weight, prepared as a coarse mixture.

The above was adapted for use on Teagasc Daily from the paper titled: Indoor nutritional management for growing-finishing cattle authored by Mark McGee and Edward O’Riordan and published in the Beef 2024 Open day book. For more insights, access the full publication here.