Comparative efficacy of plant and animal protein sources on the growth performance, nutrient digestibility, morphology and caecal microbiology of early-weaned pigs

The present study was conducted to evaluate and compare the effects of various animal and plant protein sources on piglet's performance, digestibility of amino acids and gut morphology in weaned pigs until 28 days after weaning. The plant protein sources used :were soybean meal (SBM), fermented soy protein (FSP), rice, protein concentrate (RPC); and animal protein sources tested were, whey protein concentrate (WPC) and fishmeal (FM). Iso-proteinous (21%) diets were formulated and lysine (1.55%) content was similar in all the diets. The level of each protein source added was 6% by replacing SBM to the same extent from the control diet containing 15% SBM. The ADG was higher (p<0.05) in the groups fed animal proteins as compared with plant proteins at all the levels of measurement, except during 15-28 days. The highest ADG was noted in WPC and FM fed diets and lowest in SBM fed diet. The feed intake was higher in animal protein fed groups than plant proteins at all phases, but the feed:gain ratio was not affected by protein sources except during overall (0 to 14 day) measurement which was improved (p<0.05) in animal protein fed diets compared to plant protein sources. The digestibilities of gross energy, dry matter and crude protein were higher in animal protein fed groups than for plant protein fed sources. The apparent ileal digestibilities of essential amino acids like Leu, Thr, and Met were significantly (p<0.05) higher in animal proteins fed animals as compared with plant protein fed animals. But the apparent fecal digestibilities of essential amino acids like Arg and Ile were significantly higher (p<0.05) in plant protein diets than animal protein sources. The villous structure studied by scanning electron microscope were prominent, straight finger-like, although shortened and densely located in FM fed group as compared with others. The lactic acid bacteria and C. perfringens counts were higher in caecal contents of pigs fed plant proteins than the animal proteins. Overall, it could be concluded that animal protein sources in the present study showed better effects on growth performance, nutrient digestibility and gut morphology than plant protein sources.