Some European producers have elected to formulate relatively low crude protein diets in an effort to reduce environmental nitrogen excretion (pollution). In addition. lowering crude protein is believed to reduce hind gut fermentation of undigested protein that can increase the risk of post-weaning scour. Pigs that are fed low protein diets may spend increased amounts of time investigating their environment and foraging for food in an effort to find what they are lacking. When environmental enrichment is very poor the pigs may increasingly redirect their behaviours towards pen mates. If the act of “nibbling” on a penmate should happen to produce some blood the pigs will become very interested in the blood since it can be an easy source of amino acids and other nutrients that are missing from the diet. These Dutch researchers investigated the effect of supplementing a low protein diet with indispensable (essential) amino acids (IAA) or providing additional environmental enrichment on tail biting. Undocked pigs (n = 48 groups of 12) received either a normal protein diet (NP), a low protein diet (LP), an LP diet with supplemented IAA (LP+), or LP diet with extra environmental enrichment (LP-E+) during the starter, grower, and finisher phase. All treatments in the nursery phase had a jute bag (1.1 × 0.6 m) and a rope (2.85 m in length) that was standard enrichment. The extra environmental enrichment consisted of a rope (2.85 m in length, with three nodes), a wooden beam (1 × 0.095 × 0.045 m) hanging from the pen walls with metal chains, and a provision of 350 g of chopped straw (approximately 15 cm long) per day.
The researchers found the following:
- LP and LP-E+ had a lower feed intake, growth, and gain-to-feed ratio, and were more active than NP and LP+ pigs. (Not a big surprise)
- LP-E+ pigs interacted most often with enrichment materials, followed by LP, LP+, and NP pigs. ( They seemed to make use of the extra enrichment)
- LP pigs showed more tail biting than all other groups during the starter phase when compared to NP and LP+ pigs.
- LP-E+ reduced tail biting only in the starter phase. It did not help in grower or finisher.
- LP+ reduced tail biting in starter, grower and finisher
- Tail damage was more severe in LP pigs than in NP and LP+, with LP-E+ in between.
Take Home Messages:
- This study confirms previous findings that pigs that are fed low crude protein rations can be at greater risk of tail biting behaviour.
- IAA supplementation largely counteracted the negative effects that the low protein IAA deficient diet had on feed intake, average daily gain, and damaging behaviour.
- Supplementing the low crude protein diet with the required indispensable amino acids was more effective at reducing tail biting than only relying of the provision extra environmental enrichment.
- The researchers point out that pigs on the low protein diet will actually start to reduce intake of the deficient diet and choose to spend more time foraging for a diet that can satisfy their needs. More time spent foraging and consequently “nibbling” on penmate’s body parts can be a nasty consequence.
References: Ilaria Minussi , Walter J J Gerrits , Alfons J M Jansman , Rosemarijn Gerritsen , William Lambert , Johan J Zonderland , J Elizabeth Bolhuis Amino acid supplementation counteracts negative effects of low protein diets on tail biting in pigs more than extra environmental enrichment Sci Rep . 2023 Nov 7;13(1):19268. doi: 10.1038/s41598-023-45704-0.
