Fat deposition in pigs up due to night feeding

That was the conclusion of a study presented by PhD student Rik van Erp at the symposium ‘Digestion Kinetics in Pigs’ on October 3 in Wageningen, the Netherlands.

Time of feed intake can be influenced by several factors, such as a high stocking density and heat stress. Mr Van Erp, attached to Wageningen University & Research, said, “Small pigs housed in high stocking density will be chased away by dominant pigs, and are forced to eat on different times. Also pigs experiencing heat stress will have different feeding times.”

The question of the study was, in case timing of feed intake indeed matters, how then will it affect energy metabolism? During the study 1 group of pigs was fed at normal feeding times during the day and the other group was fed during the night.

Higher energy retention for pigs fed at night

Results of the study showed that digestibility of dry matter, energy and nitrogen were similar in both groups. However, the researching team observed a metabolic difference. Heat production of the day fed pigs was higher than of the night fed pigs. That all resulted in a higher energy retention for the pigs fed at night.

Mr Van Erp said, “We observed no difference in retention of protein, so all extra energy was stored as fat. The night fed group stored 7% more fat than the group fed at day time.”

That extra storage of fat resulted in 1.7kg more final fat mass and 0.6mm higher back-fat thickness. The percentage of meat decreased with 1.1% and carcass weight remained unchanged.

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Lower heat production of pigs at night

Mr Van Erp said that the increase in fat deposition can be explained through the lower heat production of these pigs. He said, “Heat production can be divided in heat production related to activity and heat production due to resting metabolic rate (RMR). Looking at the 2 groups, 60% of the difference between heat production was related to RMR and 40% to activity heat.

That indicated that the difference in fat deposition is related to differences in metabolic processes, not only by activity.” Activity heat production during the study in the night fed group could be explained by the activity of pigs during feeding times and because of lights in the morning.

However, there was also an activity heat peak at 4pm in the afternoon that the researcher couldn’t explain. He said, “There were no external circumstances at that time that could have an effect on the pigs. It is probably related to the circadian rhythm of ad lib fed pigs.”