Feeding pigs silage offers sustainability gains

Growing and finishing traditional breed pigs on a grass silage total mixed ration (TMR) is a cost-effective way to produce a high-welfare product, research on an Oxfordshire farm shows.

Trials at Food Animal Initiative (FAI) looked at feeding grass and lucerne silage as part of a TMR to Gloucester Old Spot pigs as a more sustainable alternative to grain-based feeds.

Pigs aged eight to 10 weeks were placed in 8.3×4.3m pens in groups of seven to 11, split between males and females.

Groups were fed the TMR for 13 weeks at a chop length of 5-8cm. Rations consisted of lucerne, barley and minerals and were supplemented with either peas, beans or soya as a protein source.

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Woodchip and straw bedding was placed in the back third of each pen, with TMR fed on bare concrete.

Pigs were taken to 85kg achieving growth rates up to 0.85kg/day on the ration containing peas at 20 weeks old.

However, the study, which compared organic soya, beans and peas as a protein source with lucerne silage and barley, is yet to be tested on modern, fast-finishing pigs in a conventional system, says the FAI.

Results

Average daily growth rates of 0.5kg/day through the grower phase have been reported by FAI’s Laura Higham and her colleagues.

While these are short of conventional gains, they are “good for traditional breeds being fed organically”.

Importantly for FAI Farms, CCTV and observation from animal welfare specialists at Oxford University showed no tail or flank biting, which Dr Higham attributes to eating a diet more in keeping with the biology of the animal, promoting the innate desire to forage.

“Pigs can use 50% of their total digestive capacity in the colon by breaking down grasses into volatile fatty acids in the hind gut, much like a horse,” says Dr Higham.

“Feeding pigs grass silage on the floor promotes foraging behaviour with a manipulable material, which, by law, they require.”

The 20% crude protein (CP) lucerne silage allowed the pigs to eat less grain, resulting in “greatly reduced” gastric ulcerations on post-mortem inspection.

“Heavily grain-based rations don’t offer much fibre, predisposing animals to high levels of gastric ulcerations,” adds Dr Higham.

Fundamental change

Further control over feed costs can be achieved when using home-grown barley, lucerne and peas, explains Dr Higham, who admits this approach is a “fundamental change” to pork production and not a minor adjustment.

“By working with the biology of the animal, we may be able to create more of a margin in pork production,” he says.

“Feed is about 65% of cost of production in a typical conventional system, so we are examining opportunities to reduce that significant cost while improving animal welfare and reducing a dependence on soya, as we found peas led to comparable daily weight gains to the soya ration.

“This could work on farms with arable enterprises that can grow good sources of home-grown protein, which could be used to build soil fertility and act as a breakcrop to control blackgrass. We found growth rates were lower in beans, but this could be offset by beans being cheaper to produce in the UK.”

Amino acids

Unable to supply synthetic amino acids, organic feeding systems typically struggle to meet lysine and methionine requirements, explains Dr Higham.

For this reason CP is often “oversupplied”, with Dr Higham adding: “This is the trade-off you accept when feeding organically, but supplying protein is vital as lysine is key for lean muscle and growth.

“Conventional systems don’t have this issue; they can balance for amino acids. And while our system uses organic ingredients, our pigs aren’t organic.

“There are further opportunities to explore in balancing protein in the rations and examining how forage feed sources can be exploited in commercial genetics.”

In the future, Dr Higham wishes to compare the feeding system to conventional rations using commercial genetics.

Fundamental change

Further control over feed cost can be achieved when using home-grown barley, lucerne and peas, explains Dr Higham, who admits this approach is a “fundamental change” to pork production and not a minor adjustment.

“By working with the biology of the animal, we may be able to create more of a margin in pork production,” he says.

“Feed is about 65% of cost of production in a typical conventional system, so what we are examining opportunities to reduce that significant cost while improving animal welfare and reducing a dependence on soya as we found that peas led to comparable daily weight gains to the soya ration.

“This could work on farms with arable enterprises that can grow good sources of home-grown protein, which could be used to build soil fertility and act as a breakcrop to control blackgrass. We found that growth rates were lower in beans but this could be offset by beans being cheaper to produce in the UK.”

Amino acids

Unable to supply synthetic amino acids, organic feeding systems typically struggle to meet lysine and methionine requirements, explains Dr Higham.

For this reason crude protein is often “oversupplied”, with Dr Higham adding:

“This is the trade-off you accept when feeding organically, but supplying protein is vital as lysine is key for lean muscle and growth.

“Conventional systems do not have this issue, they can balance for amino acids.

“And while our system uses organic ingredients, our pigs aren’t organic as they are not outdoors.

“There are further opportunities to explore in balancing protein in the rations as well as examining how forage feed sources can be exploited in commercial genetics.”

In the future, Dr Higham wishes to compare the feeding system to conventional rations, using commercial genetics after having success in FAI’s slower growing Gloucester Old Spots.