ABSTRACT: The chemical composition of corn is variable and the knowledge of its chemical and energetic composition is required for an accurate formulation of the diet. This study aimed to determine the chemical composition, that is, dry matter (DM), mineral matter (MM), neutral detergent fiber (NDF), acid detergent fiber (ADF), ether extract (EE), crude protein (CP), gross energy (GE) and energetic values of different varieties (batches) of corn and validate mathematical models to predict the metabolizable energy values (ME) of corn for pigs using near infrared spectroscopy (NIRS). Corn samples were scanned in the spectrum range between 1,100 and 2,500 nm, the model parameters were estimated by the modified partial least squares (MPLS) method. Ten prediction equations were inserted into the NIRS and used to estimate the ME values. The first degree linear regression models of the estimated ME values in function of the observed ME values were adjusted. The existence of a linear ratio was evaluated by detecting the significance to posterior estimates of the straight line parameters. The values of digestible energy and ME ranged from 3,400 to 3,752 and 3,244 to 3,611 kcal kg−1, respectively. The prediction equations, ME1 = 4334 – 8.1MM + 4.1EE – 3.7NDF; ME2 = 4,194 – 9.2MM + 1.0CP + 4.1EE – 3.5NDF; and ME7 = 16.13 – 9.5NDF + 16EE + (23CP × NDF) – (138MM × NDF) were the most adequate to predict the ME values of corn by using NIRS.

ABSTRACT The objective of this study was to evaluate the standardized ileal digestible (SID) valine and SID leucine levels on performance, backfat thickness, longissimus dorsi depth, and biochemical blood parameters of starting gilts. A total of 72 gilts, with initial weight of 15.16±1.15 kg, were distributed in a randomized block design in a 2 × 4 factorial scheme, comprised of two SID leucine levels (1.20 and 1.77%) and four SID valine levels (0.58, 0.73, 0.88, and 1.03%), with nine replicates and one animal per experimental unit. No interactions were observed for growth performance parameters. Final weight and average daily gain presented linear and quadratic effects. Setting data to the quadratic model associated with the Linear Response Plateau model, the optimal level of SID valine for average daily gain was achieved at 0.703%. A quadratic effect was also observed for average daily feed intake (ADFI), estimating the highest ADFI at 0.822% of SID valine. No branched chain amino acid (BCAA) effects were observed for backfat thickness, longissimus dorsi depth, and lean meat percentage. The interaction between levels of BCAA showed that the highest SID leucine levels (1.77%) provided a high plasma urea concentration only at low SID valine levels (0.58 and 0.73%). The SID valine requirement of starting gilts for a maximum average daily gain is achieved at 0.703%, corresponding to 9.72 g day−1, and is not affected by SID leucine levels currently used in conventional diets.

RESUMO O milho é um dos principais alimentos utilizados em rações para suínos, porém existem variações em sua composição química e conteúdo de energia metabolizável (EM). Portanto, são necessários métodos rápidos para se determinar os valores de EM de forma precisa, melhorando as dietas dos leitões. O trabalho determinou e ajustou equações de predição de EM do milho de 1a e 2a safra para leitões. Foram realizados dois experimentos para determinar os valores de EM de 18 cultivares de milho, avaliando-se os milhos de 1ª e 2ª safras. Foram realizadas as análises de matéria seca (MS), amido (AMI), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), proteína bruta (PB), extrato etéreo (EE), matéria mineral (MM), cálcio (Ca), fósforo (P) e energia bruta (EB) dos milhos. Para a determinação dos valores energéticos foram utilizados 40 animais em cada experimento, distribuídos em um delineamento experimental de blocos ao acaso com quatro repetições. Os valores de EM dos milhos de 1ª e 2ª safra variaram de 3281 a 3509 e de 3143 a 3652 kcal/kg MN, respectivamente, as equações ajustadas para predizer a EM apresentaram baixo R2. Os melhores ajustes para predizer a EM do milho para leitões são representados pelas equações EM= - 6306,15 + 400,652FDA + 117,286AMI + 24924,7Ca + 2489,66P - 148,41PB (R2=0,44), para os milhos de 1ª safra; EM = -7560,08 + 2,66895EB - 120,69FDA (R2=0,48), para os milhos de 2ª safra; e para o período completo de safras foi ajustada a equação EM= 2848,95 + 68,5714FDN + 161,938EE - 5563,5Ca - 1454,2P (R2=0,41).

ABSTRACT Corn is one of the primary ingredients in swine diets, but there is a variation in its chemical composition and metabolizable energy (ME) content. Therefore, faster methods are required that can determine more accurate ME values to improve piglet diets. This study determined and predicted the ME of corn from first and second harvests for piglets. Two experiments were conducted to determine the ME values for 18 corn batches, evaluating corn from first and second harvests. The corn batches were analysed to determine the concentration of dry matter (DM), starch (ST), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), ether extract (EE), ash, calcium (Ca), phosphorus (P) and gross energy (GE). To determine the ME values, 40 piglets were used in each experiment, grouped into a randomized block design with four replicates. The ME of the corn from the first and second crops ranged from 3281 to 3509 and from 3143 to 3652 kcal/kg on an as-fed basis, respectively, and the fitted equations to predict the ME presented a low R2. The best fit equation for predicting the ME of corn for piglets was determined to be ME= - 6306.15 + 400.652ADF + 117.286ST + 24924.7Ca + 2489.66P - 148.41CP (R2=0.44) for the first harvest; ME= -7560.08 + 2.66895GE - 120.69ADF (R2=0.48) for the second harvest; and ME= 2848.95 + 68.5714NDF + 161.938EE - 5563.5Ca - 1454.2P (R2=0.41) for the joint harvest.

Two experiments were carried out to evaluate the reduction of crude protein (CP) in diets supplemented with synthetic amino acids for piglets of 15 to 30 kg. In the performance assay (Exp I), 60 piglets with initial weight of 15.34±0.87 kg and final weight of 30.08±1.59 kg were distributed in a randomized block design with six replicates, five treatments and two animals per experimental unit. The treatments consisted of five diets in which the CP was reduced by 1.5 percentage points, resulting in low-protein diets (19.24, 17.74, 16.24, 14.74 and 13.24%), meeting the requirements of amino acids with inclusion of L-lysine, DL-methionine, L-threonine, L-tryptophan, L-valine and L-isoleucine. The average daily gain and feed conversion according to the Linear Response Plateau model (LRP) were estimated at 14.23 and 14.79% of CP, respectively. As the CP levels were reduced, there was an increase in the essential:non-essential amino acids ratio. The plasma urea concentration decreased linearly, indicating that there was a better use for amino acids with the CP reduction. In the nitrogen balance (Exp II), 30 crossbred barrow piglets with average weight of 21.69±4.46 kg were housed in metabolic cages, distributed in a completely randomized design with five treatments and six replicates, and the experimental unit consisted of a piglet. The biological protein value in the diets remained above the ideal (70%), in which the level of 13.24% CP corresponded to the highest value. There was no difference in levels of urea in blood and urine. Reduction of protein levels is efficient in decreasing the pollution effect in the excreta, with lower nitrogen excretion in feces and urine.