Lower protein good
REPLACEMENT gilt diets should be lower in protein than typical grower or finisher rations to increase body fat at mating and increase longevity in the herd.
Thats the view of MLC pig scientist Pinder Gill, reporting on a study at MLCs Stotfold Pig Development Unit which will be featured at the Pig and Poultry Fair. The project aims to determine how much energy and fat reserve gilts require to produce more than six litters. Sows are often culled after just four or five litters, he adds.
A total of 400 gilts from some of the UKs major breeding companies have entered the study. These come onto the unit at 30kg and are fed on different diets to change the amount of lean and fat at first mating to third or fourth oestrus.
The study will not be concluded for another two years. But Dr Gill believes that too much protein is fed when breeding gilts are reared on grower and finisher rations.
"These diets are designed to promote lean growth, and when fed to gilts they can have backfat measurements of only 13mm at mating when the target is 19mm." To achieve these targets at Stotfold, lysine levels in the finisher diet had to be halved, he explains.
"Selection pressure for increased leanness has also meant that breeding gilts have insufficient body fat reserves at first mating."
Fat reserves are important for milk production, explains Dr Gill. It is common for gilts with their first and second litter to eat too little to support the tremendous demand for energy.
"A young sow producing 10 weaned piglets at 7kg each gives 230 litres of milk at 8% fat – thats 18kg of fat. The milk also contains 11kg of lactose. She must supply the energy needed for milk from either feed or body fat reserves," says Dr Gill.
But he urges caution when increasing the gilts fat reserves by reducing feed protein. Very low protein diets will reduce reproductive efficiency, says Dr Gill. He advises reducing protein to some extent to encourage some fat deposition but taking care not to reduce levels too low to protect reproductive performance.
• This is one of 15 MLC, MAFF and commercial funded projects to be featured on the Pork Chain – from breeding to quality display at the Pig Fair. *
Fat reserves are important for milk production, and gilts should be fed lower protein diets to increase their body fat levels suggests MLCs Pinder Gill.
• Lower protein than finisher rations.
• Encourage fat deposition.
• Too little protein reduces reproductive efficiency.