Nitrogen balance of barrows (15-30 kg) fed low protein and different digestible isoleucine levels

Abstract

SUMMARYTwenty crossbred castrated barrows, averaging 22.26 ± 1.79 kg of body weight, were used. The animals were individually alloted in metabolic cages, in a randomized blocks design, with five treatments (0.45, 0.52, 0.59, 0.66 and 0.73 % of digestible isoleucine) and four replicates. The diets were based on corn and soybean meal with low crude protein (14.15 %) and different levels of digestible isoleucine. The diets were humidified and supplied twice a day (7 am and 7 pm) to reduce losses and facilitate ingestion. The experimental period lasted 12 days, being 7 days for adaptation to metabolic cages and experimental diets and 5 days for total feces and urine collection. Feces were analyzed for dry matter and nitrogen (N), whereas urine samples were analyzed for N. The plasma urea nitrogen was also determined. Then, the N intake, N excretion (feces and urine), N absorbed, N retention, N retention/N intake, N retention/N absorbed and total N excretion were determined. Only N intake (g/kg BW 0.75 /day) was influenced (p<0.05) by digestible isoleucine levels, showing a linear increase on N intake as digestible isoleucine levels increased in the diets. RESUMOForam utilizados vinte suínos mestiços, machos castrados, com peso vivo inicial médio de 22,26 ± 1,79 kg; distribuídos individualmente em gaiolas de metabolismo, em um delineamento experimental de blocos ao acaso, com cinco tratamentos (0,45; 0,52; 0,59; 0,66; 0,73 % de isoleucina digestível) e quatro repetições. As dietas foram formuladas à base de milho e farelo de soja, com baixa proteína bruta (14,15 %), e diferentes níveis de isoleucina digestível. As dietas foram umedecidas e fornecidas duas vezes ao dia (7 e 19 h) para reduzir perdas e facilitar a ingestão. O período experimental teve duração de 12 dias, sendo 7 dias para adaptação às gaiolas metabólicas e rações experimentais e 5 dias de coleta total de fezes e urina. Posteriormente, foi determinado o teor de matéria seca das fezes e o teor de nitrogênio (N) das fezes e urina, bem como o nitrogênio da uréia plasmática. Foram, então, calculados o consumo de N, excreção de N (fezes e urina), N absorvido, N retido, N absorvido/N retido, N retido/N consumido, N retido/N absorvido e excreção total de N. Obteve-se significância (p<0,05) apenas para o nitrogênio ingerido (g/kg PV 0,75 /dia), em que o modelo linear apresentou aumento nos valores de N ingerido à medida que aumentaram os níveis de isoleucina digestível nas rações.

Efeitos de dietas com baixo e alto teor de proteína bruta suplementadas até o quarto aminoácido limitante para dois cruzamentos comerciais de leitões iniciantes

“…A higher catabolism of amino acids, observed only in N in PIC piglets, promoted an effect on TNE since fecal and urine N are used to determine absorbed and retained N. The highest TNE did not change urine N concentration. This could cause lower N intestinal absorption and greater N usage (Castilha et al, 2013). Additionally, when energy intake is lower than maximum N deposition requirement, urine N excretion would increase (Zhao et al, 2019).…”

“…However, studies have shown that it is necessary to adapt diets according to production systems and tropical conditions, considering genetics and environmental and health conditions (Paul et al, 2007;. Thus, evaluating different ingredients and diet formulations to meet the requirements of modern pig genetics (Rostagno et al, 2017), such as formulating low-crude protein diets (Castilha et al, 2013;Toledo et al, 2014;Souza et al, 2023), have shown positive effects mainly in reduced environmental impact, but starter pigs fed low CP-based diets grew more slowly (Ruusunen et al, 2007), and increased feed intake due to lower essential amino acid content in the diet (Schiavon et al, 2018).…”

Partial replacement of soybean meal with different protein sources in piglet feed during the nursery phase

“…According to Dourmad et al [20], the reduction in urinary N elimination results from the decrease in the amount of N absorbed through of the intestine and the increase in the use of N. The lack of effect of protein sources on the crude protein intake can be correlated to the absence of significance for the variable ingested N, considering that both are interconnected [22]. The net protein utilization of 64.62% to 67.22% in the current study were similar to 65.5% and 60.8% obtained by Oliveira et al [23], who worked with growing pigs and concentrations of 12% and 14% of CP in feeds.…”