Influence of environmental temperature on nitrogen retention, apparent digestibility of protein and amino acids and energy metabolism in growing pigs

Elias Tadeu Fialho, Purdue University

Abstract

Two experiments were conducted. The first one was designed to investigate the influence of temperature (11$\sp\circ$, 17$\sp\circ$, 23$\sp\circ$, 29$\sp\circ$, and 35$\sp\circ$C) on nitrogen, amino acid and energy metabolism. Thirty crossbred castrated male pigs weighing 23.9 kg were assigned to one of five experimental ambient temperatures. The animals were adapted for three weeks to their experimental temperatures before initiating the metabolism assay. The pigs were housed individually in steel metabolism cages in temperature controlled rooms. Feces and urine were collected daily for 5 days. The data were subjected to regression analysis. Linear, quadratic and cubic components were tested using orthogonal polynomials. The estimated values of apparent digestibility of protein (ADP), nitrogen retention (NR), net protein utilization (NPU) and biological value (BV) increased as environmental temperature increased until 29$\sp\circ$C, but decreased after that. Apparent digestibility of amino acids were greater at 29$\sp\circ$C. Digestible energy (DE) and metabolizable energy (ME) values showed that the efficiency of energy utilization increased as environmental temperature increased. The results suggest that temperatures fall between 25$\sp\circ$ and 29$\sp\circ$C are within the thermoneutral zone of 32 kg pigs kept in metabolism cages. The second experiment was conducted to investigate the influence of environmental temperature (25$\sp\circ$ and 35$\sp\circ$C) and dietary protein level (15%, 19% and 23% CP) on nitrogen, amino acid and energy metabolism in growing pigs. Thirty-six crossbred castrated male pigs weighing 23.1 kg were randomly assigned to one of six environmental temperature-dietary protein combinations (2 x 3 factorial arrangement). The methodology was the same as described in experiment 1. The NR was increased significantly (P $<$ 0.01) by increasing the environmental temperature and the dietary protein level. There was, however, a significant interaction (P $<$ 0.01) between environmental temperature and dietary protein level for NR. The variables BUN, ADP, NPU, and BV were significantly (P $<$ 0.01) higher for pigs housed at 25$\sp\circ$C than those at 35$\sp\circ$C. Increasing protein levels resulted in significant (P $<$ 0.01) effects on ADP and NPU values. The protein levels above 19%, had no influence (P $<$ 0.01) on apparent digestibility of amino acids. The DE and ME values were higher (P $<$ 0.01) at 25$\sp\circ$C than at 35$\sp\circ$C. Digestible energy increased as protein level increased (P $<$ 0.01). Based on the improvement of NR, ADP and NPU as dietary protein level increased, at 35$\sp\circ$C, it appears that the protein concentration during heat stress, should be increased in growing pigs.

Degree

Ph.D.

Advisors

Cline, Purdue University.

Subject Area

Livestock

COinS