Changes in Energy, Protein and Fat Retention in Pigs Reared Under a Low Environmental Temperature

Abstract

A total of 42 pigs weighing about 30 to 120kg (non-pregnant) were used for the experiments. These animals were kept individually in metabolism cages and different amounts of feed were given to each pig both under a low environmental temperature (7-8°C, 8-9°C and 13-14°C) and a thermoneutral zone (20.2±0.6°C) for about a month. Then, respiration trials and nitrogen (N) balance trials were conducted for 3 days, and energy and protein retention were determined. Fat retention was estimated using these data. The effects of a low environmental temperature on protein and fat retention were investigated in this study. The results obtained are summarized as follows:
(1) N retention was significantly (P⟨0.01) reduced at a low temperature and accompanied by an increase in the urinary and fecal excretion of N. (2) Energy retention was also significantly (P⟨0.01) reduced at a low temperature and accompanied by an increase in the urinary excretion of energy and heat production. (3) The decreased rate (Ed, kcal/W^0.75kg/day) of energy retention at a low temperature compared with that for a thermoneutral zone linearly increased with an increase in the difference between the lower critical temperature (Tc, °C)and the environmental temperature (T, °C); that is, Ed=5.18+5.67(Tc-T). (4) There was no definite relationship between the decreased rate of protein retention at a low temperature and Tc-T. The average decreased rate of protein retention at a low temperature was 1.9±0.8g/W^0.75kg/day. (5)The decreased rate (Fd, g/W^0.75kg/day) of fat retention at a low temperature compared with that for a thermoneutral zone linearly increased with the increase of Tc-T; that is, Fd=-0.95+0.58 (Tc-T). (6) These results suggest that extra energy for maintaining the body temperature of pigs reared under a low environmental temperature is mainly supplied by decreasing protein retention in the body when the value of Tc-T is relatively small, and by decreasing fat retention when the value of Tc-T is relatively large.