Low protein diets for pig production
Research partners: University of Bristol, Scottish Agricultural College (SAC)
Industrial partners: JSR, Tulip, ABN, Forum Products, BPEX and QMS
Sponsors: This project is funded under the Defra LINK Sustainable Livestock Production programme
Duration: January 2009 – December 2011
Press release (July 2012): http://www.bpex.org.uk/articles/302293/
Effects of low protein diets on lean genotype pigs – growth, feed / N-intake and fat indicators (20th Int. Symp. “Animal Science Days”, Kranjska gora, Slovenia, Sept. 19th−21st, 2012)
This research project is investigating whether protein levels in pig diets can be considerably reduced below current standard levels to allow producers to meet increasingly stringent targets for nitrogen emissions. Dietary protein is the main source of these pollutants. At the same time, diets should support good performance and produce lean carcases. Previous attempts to reduce protein have often resulted in over fat carcases.
The main experimental work in this project is a large growth trial in which pigs of a lean genotype are reared from 40 -115 kg, the carcases are then sent to the University of Bristol for analysis. Carcases from the latest batch of pigs (the preliminary trial) are currently being dissected and meat quality measurements are underway.
This batch of pigs is being used to test three diets, a commercial standard diet and two low protein regimes:
Protein is reduced from 20% to 16% as liveweight increases
Low protein 1 (LP1)
Protein is reduced from 17% to 14% and amino acid levels are maintained at the same level as in the commercial treatment
Low protein 2 (LP2)
Protein is reduced to 11% in the finishing stage but amino acids are lower than in the LP1 treatment. This regime will determine whether manipulating amino acid levels can increase muscle fat (marbling fat) and pork juiciness.
During growth the pigs are being scanned three times using the computerised tomography (CT) facility at SAC. This will chart fat deposition in the different parts of the body as overall fatness increases. An outstanding question surrounding the use of diets with different protein levels is whether they change fat distribution, for example between fat in the gut, backfat and marbling fat. Such changes influence carcase classification, how much fat has to be trimmed during processing and the juiciness of pork.
After ad libitum feeding the final liveweights of the pigs in the preliminary batch were similar in both the Commercial and LP1 trials, both of these being higher than in LP2. Commercial and LP1 pigs had similar daily gains and feed conversions, both superior to LP2. The results show that pigs given the LP1 diet, supplying considerably less protein than the Commercial regime, performed just as well. The LP2 diet supplied less lysine and other essential amino acids than the other two diets and the poorer performance was presumably due to this.
Initial results show that subcutaneous fat thickness did not differ between the three treatments. The group fed the LP2 diet had the highest concentration of marbling fat in the loin muscle with those fed the LP1 diet having intermediate levels. This effect of low protein diets on marbling fat has been seen before but not in the absence of an effect on subcutaneous fat thickness as seen here. Loins from the three groups have been aged and presented to the taste panel at Bristol following griddling; the results are awaited.
Following this preliminary batch there will be three main trial batches which will receive similar nutritional treatments. In these batches, AutoFOM carcase classification data on the pigs will be collected. The links between CT scans and AutoFOM measurements will be established for their ability to measure carcase composition and meat quality.
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