Effect of sweet potato leaf silage as a protein source on growth performance, physiological and serum biochemical response of growing pigs under moderate heat stress

In the context of climate change, feeding pigs with agricultural co-products could reduce the carbon footprint of pig production and improve pig response to Heat Stress (HS). The aims of the present experiment were: 1) to investigate the effects of replacing 70% of the crude protein (CP) by sweet potato (SP) leaves silage on growth performance, slaughter traits and serum biochemical response and 2) to evaluate the effect of this diet on heat tolerance compared to a diet based on soybean meal (SBM). Forty-eight Large White barrows were allocated to two diets differing in their protein source: the control diet (CON) composed of green banana ( ad-libitum ) and SBM, or the silage diet (SIL) in which 70% of CP from SBM was replaced by ensiled SP foliage, supplemented with 3 essential amino acids (Methionine, Lysine and Threonine) and with green banana ( ad-libitum) . Within each diet, pigs were allocated to two environmental treatments, Thermoneutral (TN) vs. Heat Stress (HS). Results showed that irrespective of temperature, the SIL diet reduced daily feed intake and increased nitrogen excretion. Biochemical blood parameters confirmed that protein metabolism was affected by the SIL diet with reduced total protein, blood urea nitrogen and albumin. However, average daily gain and carcass weight were unaffected by soybean CP replacement. There was no effect of temperature or interaction diet x temperature on performance, probably due to moderate heat stress during experiments. Nevertheless, thermoregulatory parameters were reduced in the SIL diet, suggesting lower heat production when replacing soybean CP by SP leave silage.