Changes in plasma urea concentration can be used to determine protein requirements of two populations of pigs with different protein accretion rates.

Abstract

The experiment had two objectives: 1) to determine the protein requirements of two strains of growing-finishing pigs based on growth performance, carcass characteristics, tissue accretion rates, and organ weights and 2) to evaluate whether protein requirements can be determined from changes in plasma urea concentration. Forty-six Gene Pool (GP) and 46 Hampshire (H) gilts with an initial BW of 28.5 kg were used. Pigs were allotted to two trials of a randomized complete block experiment with a 2 x 6 factorial arrangement of treatments. Five pigs from each strain were randomly selected and slaughtered at the beginning of each of the two trials. The remaining 72 pigs were individually penned and allotted to one of six dietary treatments (10, 13, 16, 19, 22, or 25% CP). Pigs remained on the experiment until the mean weight of a treatment group within each strain reached 115 kg (16 wk for GP and 14 wk for H), at which time all pigs of that strain were slaughtered. The only strain x protein level interactions that were detected were for carcass protein and water accretion rates. Gene Pool pigs grew less rapidly and utilized feed less efficiently than H pigs (P < .001). Average daily gain (quadratic, P < .05) and ADG/ADFI (quadratic, P < .05) were increased as protein level increased until a plateau was reached. Backfat depths were decreased (linear, P < .001) and longissimus muscle areas were increased (linear, P < .001) as protein level increased. Protein accretion rate was lower (P < .01) and fat accretion was higher (P < .01) in GP pigs than in H pigs. Protein accretion increased (quadratic, P < .001) and fat accretion decreased (linear, P < .001) with increasing dietary protein level. Examination of the response of plasma urea concentration over time suggested that GP pigs required 13% CP from 30 to 80 kg and 10% CP thereafter, whereas H pigs required 19% CP from 30 to 45 kg, 16% CP from 45 to 100 kg, and 13% CP thereafter.

Efeito de níveis de lisina digestível verdadeira e proteína bruta na dieta sobre parâmetros morfo-fisiológicos e utilização do nitrogênio em suínos na fase inicial

“…Com relação ao peso do pâncreas, Chen et al (1995) observaram uma redução no peso desse órgão em função dos níveis decrescentes de PB na ração. De acordo com esses autores, a maior produção de enzimas proteolíticas estimuladas pela presença de proteínas intactas no trato digestório seria a responsável por esse aumento.…”

“…Chen et al (1995), os rins, juntamente com o fígado, são os principais órgãos relacionados ao metabolismo do N, exercendo um papel importante na regulação dos níveis de aminoácidos no plasma. Entretanto, há estudos em que o consumo desses nutrientes não modificou o peso desses órgãos em suínos (LE-BELLEGO et al, 2002).…”

Planos de nutrição para leitoas com alto potencial genético para deposição de carne magra dos 65 aos 105 kg

“…Este resultado está de acordo com os de Fialho et al (1998), Gomes (1998) e Gonçalves et al (1999) e discordante dos obtidos por Friesen et al (1994), Chen et al (1995) e Irvin et al (1995).…”

Metabolizable energy requirement for starting barrow pigs (15 to 30 kg) fed on the ideal protein concept based diets

“…Since they have low feed intake, diets with high nutritional density are needed to attend such demands. Through genetic selection, pigs have been proved capable of processing food more efficiently, then, developing carcasses with a higher proportion of muscle and less fat; thus, these animals require a diet with a high concentration of digestible amino acids in order to achieve their genetic potential for lean meat accretion (Chen et al, 1995). Constant progress in management, health, environment, and genetic improvement leads to a permanent need for reevaluation and updating of studies on nutritional requirements (Caldara et al, 2001).…”