14 June 2002


Trying out new ration

LOWER sow productivity over the past year drew attention to the problem of maximising finishing weights without sacrificing grading, writes Jasper Renold.

That led us to use a special low-energy, high-fibre, high-lysine ration. Although pig throughput is increasing, we still need to reduce the number of occasions when the average P2 is unacceptable. Two possibilities are being considered. First, we are using semen from the PIC Large White Challenger boar, which is claimed to reduce back fat in the progeny by 0.5mm. PIC estimates that is worth 98p/mm. It also improves feed conversion rate by 0.06 worth 90p for each 0.1 change.

This boar is believed to achieve better leanness because of its reduced appetite in the final stages of finishing. But it leads to a possible reduction in growth rate of 14gms/day that is estimated to cost 3p/gm. All that means a net benefit of 61p per pig from which we need to deduct 30p for the more costly semen.

Some trial evidence suggests there may be no growth rate penalty at all. This semen can be used on the C15 sows and the new gilts from the Closed Herd Rotational Breeding programme. The bacon house gilts being three-quarter Large White still need the Pietrain Solution boar.

An alternative line is the PIC line 62 Adams Pietrain boar. It is similar to the Solution boar but with improved conformation and a potential for lean growth approaching that of the Challenger boar. The Pietrain boar has an extra benefit, like the Solution boar of 1%, of better killing out percentage; currently worth £1 a pig. In addition the abattoir would pay a bonus of 65p per pig for the improved conformation.

But we would have to dedicate all our slaughter pigs to George Adams. But we will await further trial data before taking this potentially attractive route.

The second approach involves testing a range of feeding programmes on a theoretical model of pig growth. Through Allied Livestock Marketing, which sells our pigs, Richard Bull from Pig Production Technical Support at ABN, has been running our pig growth, grading and nutrition data through its model to examine the costs and benefits of different feeding regimes. We have assumed a medium health status for the herd and all test runs are on pigs growing from 19kg lw to 98kg lw.

We tend to feed expensive and nutritionally dense rations at all stages so we were curious to look at the effects of feeding cheaper rations and using some form of restricted feeding in the past five weeks.

Figure 1 shows when the different rations are used and define them in terms of their lysine energy ratio. Figure 2 shows the estimated daily feed intake where pigs eat more in the early stages to compensate for the lower dense ration. We have had to put a ceiling on feed intake in the last five weeks to limit energy intake and fat deposition. The model does not yet take account of how the palatability of different raw materials affects intakes.

I hesitate to enter the contentious area of how theoretical lysine and energy requirements can be squared with the practical problems of achieving good grading while ensuring there is enough energy to drive the growth and enough lysine to maximise lean tissue growth. That is shown in Figure 1 by the wide discrepancy between low theoretical lysine energy ratios at heavy weights compared with those in many finisher rations.

Low lysine energy dry diets often have high figure levels which run the risk of limiting feed intakes and limiting energy and lysine. So we tend to overfeed these and hope the surplus energy is used to de-aminate surplus protein. It is also an insurance against pig weight variability and changes in health status and pigs appetite. That is where wet feeding scores and where feed restriction and formulation are much more flexible.

The table shows the results of using the model comparing the returns from the existing situation with those where less dense rations and feed restriction in the last five weeks were used. Margin over feed has improved by £1.63 from lower feed cost and better grading and P2 has reduced by 1.19mm. But growth has reduced by 20g/day so the pigs are taking four more days to reach the same weight. If no more accommodation is available the finishing weight would be 3kg lighter and the margin over feed is reduced to 63p.

In practice, we feel that using the finishing diets from 19kg could lead to even slower growth and would greatly increase the variability of pig weights over the whole period. But if we could restrict feed intake in the last three or four weeks without too much stress on the pigs, that could have a dramatic effect on back fat levels.

Perhaps we should put metered dump feeders above each straw flow pen and revert to good old-fashioned floor feeding. &#42

Comparison of finishing performance of current & an alternative feed regime

Current Altive

Start weight (kg) 19 19

Finish weight (kg) 98 98

Feed intake

(kg a day) 1.91 1.88

Growth rate

(g a day) 765 736

Growth period

(days) 104 108

Average P2 (mm) 11.29 10.10

Percent lean 57.82 59.17

Percentage of pigs

<12mm 69.99 85.13

Feed cost

(£ a pig) 33.40 32.40

Carcass value

(£ a pig) 72.53 73.07

Feed conversion

ratio 2.49 2.55

Feed cost per

kg lw gain (p) 42.03 40.9

Margin over

feed (£ a pig) 39.13 40.76