23 October 1998

Maize maturity under scrutiny

FEEDING beef cattle maize cut at different stages of maturity has little effect on daily liveweight gain, but cost/kg gain varies widely.

These initial results have been released by Reading University researchers. They fed 48 Simmental cross heifers and steers maize silage cut at 30%, 34% and 39% dry matter to determine the effect of crop maturity on animal performance as part of a £250,000 MAFF/MLC funded project.

Performance was recorded from a start weight for steers and heifers of 500kg and 380kg, respectively, and finished at 590kg and 490kg, respectively. The 90% forage maize diet was supplemented with a 60% crude protein concentrate formulated from 65% soya, 35% rape and 5% urea.

According to researcher Mary Browne, all beef cattle achieved daily liveweight gains of about 1.1kg: "Theres little difference in liveweight gain across the three silage maturities. However, feed conversion was better for the low dry matter silage, but at a higher cost/kg gain due to the lower dry matter yield/ha."

The higher cost/kg gain between silages – up to 2.2p/kg -(table 1 and 2) can be marginally offset by a need to feed less protein concentrate to balance the ration with the lower feed intakes.

Total intake for the 30% dry matter silage was about 1kg/head/day lower than for the other silages, adds Ms Browne. "However, increases in cost/kg gain due to lower silage yield outweigh savings in concentrate."

Mike Bryant, senior lecturer in animal production, who is co-ordinating the trial, adds that many of the heifers failed to reach minimum target carcass weights. This shouldnt be taken as an indication maize isnt a good ration for finishing heifers; the trial was not long enough to allow heifers to finish at a heavier weight.

Analysis of beef carcasses also revealed little difference in fat class or conformation with most cattle finishing to R4L and R4H. No metabolic disorders arose, says Dr Bryant.

Research in the two remaining years of the trial will now focus on performance of steers on a combination of maize and grass silage rations; effect on meat quality; and a study of the benefits of supplementing maize diets. &#42

Table 2: Maize silage costs*

Variable costs £/ha

Seed, fert, spray 222

Fixed costs (excl rent)

Cultivations 60

Drilling 25

Appl fert/slurry 17

Spraying (early season) 7

Harvest, haulage

and clamping 110

Source: Reading University

*Based on 1997 costs.

Table 1: Maize data and costings*

MAFF/MLC** beef trial

Dry matter % 30 34 39

Dry matter yield/ha (t) 11.2 14.8 15.3

Cost/t dry matter

(excl wastage) (£) 39.50 29.80 28.90

Intake (kg/head/day)

Silage 8.42 9.45 9.36

Concentrate 0.90 1.04 1.09

DLWG (kg) 1.1 1.1 1.1

Beef costs (p/kg)

Steers – liveweight 52.3 51.8 51.8

Heifers – liveweight 42.7 45.9 43.7

Source: Reading University.

*Based on 1997 costs. **Other sponsors: MGA, Bibby and Tesco.