ABSTRACT The objective of this study was to evaluate the effects of the addition of the prebiotic fructooligosaccharide and/or alfalfa hay to piglet diets on carcass traits and short-chain fatty acid profiles in the cecal digesta. Seventy-two commercial crossbred piglets of both sexes, with an average initial weight about 6 kg and age of approximately 21 days, were distributed in a randomized block design, using a factorial scheme, which consisted of three alfalfa hay levels (0, 5, and 10%) and two fructooligosaccharide levels (0 and 0.3%). Fiber addition in the presence of the prebiotic exerted an effect on cecal digesta short-chain fatty acid, increasing the acetic and reducing the butyric acid concentrations. The meat quality was also affected by the treatments, water activity, water-holding capacity of meat, and especially the reduction of fat content and the increase of moisture. The treatments did not affect the pH and the ammonia content in the cecal digesta. Most carcass traits were not affected by the treatments, except for carcass weight and backfat thickness in points 1 and 2, that decreased with the inclusions of fiber and prebiotic. The addition of 5% alfalfa hay improves carcass and meat traits in growing pigs without any change in carcass weight, demonstrating the advantage of using this ingredient to obtain a healthy final product to the customers.

RESUMO Foram realizados dois ensaios, ambos utilizando delineamento em blocos casualizados em esquema fatorial (3x2), onde foram avaliados três níveis de inclusão de feno de alfafa (0,0%; 5,0% e 10,0%) e dois níveis de frutoligossacarídeo - FOS (0,0% e 0,3%). No Ensaio 1, com o objetivo de avaliar o desempenho zootécnico, foram utilizados 72 leitões desmamados, de linhagem comercial, de ambos os sexos (1 macho + 1 fêmea/baia), seis repetições, com peso inicial de 5,95 ± 0,73kg, com idade aproximada de 21 dias. Não foi observada interação entre os fatores estudados. No período dos 21 aos 59 dias de idade o ganho de peso não apresentou diferenças entre os tratamentos. O grupo que consumiu ração com adição de 0,3% de FOS apresentou maior consumo em relação ao grupo controle (0,0% FOS). Observou-se melhora na conversão alimentar das dietas que não possuíam inclusão de FOS, porém, não houve diferença significativa entre a dieta controle e as demais dietas em relação aos níveis de alfafa. No Ensaio 2 determinou-se a digestibilidade dos nutrientes, o balanço nitrogenado e as energias digestível e metabolizável das rações. Concluiu-se que a inclusão de FOS incrementou o consumo de dietas ricas em alfafa. A adição do feno de alfafa reduziu os coeficientes de digestibilidade dos nutrientes com exceção do extrato etéreo, porém não influenciou o balanço do nitrogênio

SUMMARY Two assays were accomplished being, both using a randomized block design with factorial schema (3x2) where was evaluated three levels of inclusion of alfalfa hay (0.0%; 5.0% and 10.0%) and two levels of fructooligosaccharide - FOS (0,0% and 0.3%). Assay 1 the aimed was to evaluate the performance, was utilized 72 piglets, commercial lineage,, of both genders (one male + one female/cage), six reps with initial weight of 5.95 ± 0.73kg, aged at approximately 21 days. There was no interaction between treatments. In the period from 21 to 59 days of age,, the gain of weight didn’t show differences between treatments. The group that consumed ration with addition of 0.3% of FOS showed highest consumption in comparation with the control group (0.0% FOS). It was observe an improvement on the feed conversion of the diets that didn’t have inclusion of FOS, however, it hadn’t significant difference between the control diet and the others diets in relation to the levels of alfalfa. Assay 2 the objective was to determine the rations nutrients digestibility, nitrogen balance and the digestible and metabolizable energy. It was concluded that the addition of FOS enhances the consumption of diets with alfalfa hay. The addition of alfalfa hay reduced the digestibility coefficients of nutrients except for ether extract, but did not affect the nitrogen balance.