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

Abstract 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 dietary 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 silage diet (SIL) was formulated with a protein source based mainly on local resources: SP silage replacing 70% of SBM and supplemented with 3 synthetic AA, DL-methionine, L-Lysine and L-Threonine, while the protein source of the control diet (CON) was 100% SBM. 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. Total protein, blood urea nitrogen and albumin in the serum were reduced in the SIL diet, confirming protein metabolism changes. 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. Nevertheless, thermoregulatory parameters were reduced in the SIL diet, suggesting lower heat production when replacing soybean CP by SP silage.