C. W. Holmes

The energy and protein metabolism of pigs growing at a high ambient temperature

1. The experiment was designed to investigate the effect of growth at a high ambient temperature, 33–35°C, on the protein and energy metabolism of pigs, compared with 25°C. The high temperature caused an increase in rectal temperature of 1·4° to 1·7°C. The animals were given two low levels of feeding while growing between 25 and 70 kg live weight; energy and nitrogen retention were measured periodically. 2. The apparent digestibilities of the dietary dry matter and energy were decreased and urinary nitrogen losses were increased at the high temperature. Heat production was increased at the high temperature, by between 2% and 10%, the effect becoming more pronounced during the course of the experiment. Retention of energy and nitrogen was reduced at the high temperature. 3. The net efficiency of utilization of metabolized energy above maintenance was between 63% and 67%, and was not significantly affected by live weight or temperature. The results suggested that maintenance requirement was increased at the high temperature. 4. Analyses of sample joints indicated that the high temperature caused an increase in fat percentage only at the higher level of feeding; this result agreed with fat and protein retention calculated from the balances.

Some aspects of the energy and nitrogen metabolism of boars, gilts and barrows given diets containing different concentrations of protein

Four diets which varied in crude protein concentration from 140 to 240 g crude protein per kg dry matter were given to gilts in experiment 1, and two diets containing 140 and 200 g crude protein per kg dry matter were given t o boars and barrows in experiment 2. Two levels of feeding were offered in both experiments and energy and nitrogen balances were measured at 30 and 90 kg live weight in both experiments, and also at 50 kg in experiment 1. Nitrogen intake had a small negative influence on energy retention by pigs of all sexes, an effect which was independent of the large positive effect of metabolizable energy intake. The ratio of metabolizable energy concentration to digestible energy concentration decreased in association with increases in crude protein concentration of the diets. The results show that comparisons of feeds on the basis of their digestible energy concentrations would lead to overestimation of the energy values of those containing high protein concentrations. Live weight (or age) and metabolizable energy intake exerted positive influences on the amount of energy retained per kg live-weight gain, whereas nitrogen intake exerted a negative influence. Values for energy retained per kg live-weight gain predicted from multiple regression equations, together with calculated values for maintenance and net efficiency, were used to predict the energy retention and growth rate of pigs in various circumstances. Nitrogen retention increased in association with increases in nitrogen intake for pigs of all sexes at 30 kg live weight; there was also a corresponding increase for boars at 90kg live weight, but not for gilts or barrows at this weight. Boars retained more nitrogen than did barrows at 30 and 90 kg live weight only if given the diet with the higher concentration of protein. Metabolizable energy intake appeared to exert a small positive influence on the nitrogen retention by pigs of all sexes at 90kg live weight; however, it appeared to have no influence on nitrogen retention by pigs at 30kg live weight.

Performance of Friesian cows with high and low breeding indexes 1. Stall feeding and grazing experiments and performance during the whole lactation

The performance of 38 Friesian cows with either high or low breeding indexes was measured during the whole lactation and in short-term experiments where the cows were individually given cut pasture in stalls, or grazed on pasture. Cows with high breeding indexes produced more milk fat than did cows with low breeding indexes in the short-term experiments, and during the whole lactation. There was close agreement between the expected differences (predicted from breeding indexes) and the measured differences in milk fat yield. When fresh cut pasture was given ad libitum in stalls the intake per cow was the same between genotypes. However, when intake was expressed per unit of metabolic weight, the mean pasture drymatter intake of the high breeding index cows was 1·05 of that of the low breeding index cows, but the difference was significant in only one of the four indoor feeding experiments. The difference between genotypes in size was not regarded as significant because the differences in mean live weight at calving (high breeding index – low breeding index) of the animals purchased in the 1st and 2nd years were –28 and 9 kg respectively. During the whole lactation, low breeding index cows gained significantly more live weight and lost significantly less body condition than did the high breeding index cows. No significant differences in live-weight and body-condition changes could be detected during the shorter periods (4 to 5 weeks) of the indoor feeding and grazing experiments. It can be calculated that the higher milk production of the high breeding index cows could be explained partly because they eat more (per unit metabolic live weight) and more importantly because they divert a higher proportion of the food they eat to milk production and a lower proportion to live-weight gain than do the low breeding index cows.

A note on the protection provided by the hair coat or fleece of the animal against the thermal effects of simulated rain

The rate of heat transfer from a model animal, covered with one of three animal pelts, was measured when the pelts were dry and when they were exposed to a fine spray of water. Wetting of the pelts increased heat transfer by 192, 114 and 15W/m 2 respectively for the hairless skin, the skin with calfs hair coat (5 to 10 mm) and the skin with the lambs fleece (60 mm). These results demonstrate the considerable protection against the thermal effects of wetting which is provided by animal coats, particularly if these are relatively deep.

Growth and backfat depth of pigs kept at a high temperature

1. Two experiments have been carried out to determine the effect of a high air temperature, 32·33°C, on growth and backfat depth of pigs, by comparison with a thermo-neutral air temperature, 22·24°C. The diet consisted predominantly of whey, since it was expected thatthis would enable appetite to be maintained at the higher temperature. 2. Food intake was reduced by 5% to 7% during the period of exposure to 32°C in Experiments 1 and 2 respectively. Growth rate and FCE were reduced significantly only in Experiment 2. 3. Backfat depths measured above the eye muscle were significantly increased by the hot treatment in both experiments; those measured on the split carcass were consistently greater for the hot treatment.

Growth of pigs fed cool whey at two ambient temperatures.

An experiment aimed at examining the effects of gramine and hordenine, incorporated into diets, on the growth and histological structures of the chicken liver has been carried out at the animal house complex, Analytical Laboratory, and Histology laboratory of the University of New England, Armidale, Australia. Five treatment groups (50 and 500 ppm hordenine or gramine, and standard feed as control) were administered to one-week old broiler chickens. Each treatment group had six heads of chickens and were replicated 6 times. Data collected including body weight and feed intake (recorded weekly), liver tissue collection for histological examination, and determination of gramine and hordenine in the liver. Data were analysed using Analysis of Variance (ANOVA) at 5% level of confident. Results demonstrated that gramine had more effects than hordenine on the animal tested. A high concentration (500 ppm) of either gramine or hoedenine was sufficient to induce changes in liver structure of the chickens as indicated by cell vacuolation even though they were not necessarily associated with reduced feed intake or growth rate of the animals. Scab-like lesions on their feet during weeks 4 and 5 of the experiment were observed from the group of 500-ppm gramine. Key Words : gramine, hordenine, chicken

Effects of exposure to a hot environment on Friesian and Brahman X Friesian cattle, with some measurements of the effects of exposure to radiant heat.

1. Eight calves of each of two breed types, Friesian (Fr) and Brahman × Friesian (FB), were fed ad libitum on one of two diets; the digestibility of the dry matter of the diets was 72% and 63%. Eight calves were kept at 34°C and eight at 17°C. In a second experiment six of the calves previously exposed to 34°C were subjected to daily exposures to a radiant heat load at 32°C air temperature, while fed on the diet of lower digestibility. 2. Rectal temperatures and respiratory rates were higher, and food intakes and growth rates were lower, at 34°C than at 17°C. However there was only a small difference in growth rate between the two temperatures after the effect of temperature on food intake had been removed by regression. 3. At 34°C FB calves had lower rectal temperatures and respiratory rates than Fr calves, and when fed on the diet of higher digestibility FB calves ate more and grew faster than Fr calves at both temperatures; however there were only small corresponding differences between the breed types for calves fed on the diet of lower digestibility at both temperatures. 4. At 34°C FB calves had lighter (weight) hair coats than Fr calves and FB calves had lighter coats at 34°C than at 17°C; the latter difference was not apparent for Fr calves. Nevertheless, neither rectal temperature nor respiratory rate was significantly affected for either breed by removal of the hair coat at 34°C. 5. In the second experiment the rectal temperatures of FB calves increased by smaller amounts during exposure to radiant heat than was the case for Fr calves; FB calves had faster sweating rates than Fr calves during these exposures.

Some thermal effects on the pig of the ingestion of liquid feed at various temperatures.

1. Experiments have been performed to determine the thermal effects, on pigs, of the ingestion of whey at various temperatures while housed at various air temperatures. 2. Measurements of carotid artery and rectal temperatures showed that a general cooling of deep-body tissues occurred after the ingestion of cool whey. 3. Measurements of rectal and skin temperatures, and observations of respiratory rate and shivering activity, indicated that thermo-regulatory responses were induced by the ingestion of cool whey; the nature of the responses was dependent on the air temperature. 4. The results indicate that the temperature of liquid food offered to animals is a significant parameter in their climatic environment.

A note on the metabolism of ca, P, Mg, Na and K by pigs growing at a high ambient temperature

Two levels of feeding were offered at each of two air temperatures, 25° or 33°C, to pigs while they grew from 20 to 70 kg live weight; two pigs were subjected to each of the four treatments. Significant increases occurred in the urinary excretion of Ca and K by the two pigs fed on the higher level and exposed to 33°C. However these effects could not be related in an obvious way to the lameness which developed in the latter pigs.

SOME ASPECTS OF THE ENERGY METABOLISM OF GROWING PIGS FED ON DIETS CONTAINING DIFFERENT CONCENTRATIONS OF PROTEIN

Energy and nitrogen balances were measured with 16 gilts at live weights (LW) of 30, 50 and 90 kg. Two levels of feed intake were offered with four diets which differed in protein concentration. The pooled data provided estimates for partial efficiency for growth, and maintenance requirement, of 0.62 and 0.45 MJ/kg 0.75 metabolizable energy (ME) daily. Multiple regression analyses showed that when ME was kept constant the energy retained (ER) decreased slightly in association with increases in nitrogen intake (NI). Energy retained as protein in pigs of 50 kg LW was influenced by both ME intake (MEI) and NI; however, MEI had no such effect on pigs of 30 kg LW whereas NI had no such effect for pigs of 90 kg LW.