R. M. Livingstone

Effects of progressive feed restriction on the growth and carcass composition of pigs: comparative responses of gilts and castrates

A barley-based diet, containing 16% protein, was given at average daily rates of 1·2–2·5 kg (16–32 MJ, metabolizable energy (ME)) to 32 female and 32 castrated male pigs during their growth from 25 to 90 kg. At high intakes there was no difference in growth rate between the sexes, but with progressive feed restriction the growth of males was more severely retarded than that of the females. Both sexes achieved their minimum feed conversion ratios at approximately 25 MJ. The reductions of fat thickness with progressive feed restriction were greater by approximately 20% in the females than in the males. The two sexes had the same mean back fat thickness when the gilts had 4·7 MJ more ME per day than the castrates. It was inferred that the energy requirement for maintenance was 15% greater in the males than in the females.

Moist barley for growing pigs: some effects of storage method and processing.

Forty-eight pigs were used to compare the feeding value of barley which had been stored dry, and then hammer-milled, with that of barley stored moist, either anaerobically or treated with 1·3% propionic acid, and then rolled. The pigs were fed from 30 kg live weight for a period of 11 weeks and during this period all consumed the same allowance of dry matter. The growth rate and feed conversion ratio of the pigs given the rolled moist barley were significantly poorer than those of others given dry milled or acid treated rolled barley. There were no treatment differences in carcass attributes. Microbiological counts made throughout the experiment showed that there was no significant fungal or bacterial development on the acid treated barley. Similar numbers of bacteria were present on the dry barley as on the moist, but the fungal count for the moist grain was always at least 500 times higher than that of the corresponding dry sample. The dominant organisms were identified. In a further experiment the apparent digestibility of dry matter and nitrogen of diets containing dry, moist or propionic acid treated barley, processed either by milling or rolling, were determined. The highest values were obtained for dry barley. Acid treated moist barley had lower values than moist barley. The method of processing did not affect the apparent digestibility of the dry matter, but that of the N was significantly lower for the rolled barleys.

Copper sulphate as a growth stimulant for pigs : effect of level and purity.

Two 2 × 4 factorial experiments each involved 8 litters of 8 pigs, one pig from each litter being allocated to each treatment. Diets containing supplements of a commercial grade of copper sulphate were compared with others containing Analar (Experiment 1) or micro-analytical reagent grade copper sulphate (Experiment 2). Four levels of each of two grades of CuSO 4 .5H 2 O, providing 16, 62, 125 or 250 p.p.m. Cu in the diets, were given in each experiment. The pigs were put on experiment at 8—9 weeks of age and most were slaughtered as their individual weights reached about 200 lb. The exceptions were 4 litters in Experiment 1 which were taken off experiment at that weight but not slaughtered. The pigs were fed in individual compartments, meal allowances being determined from a fixed scale based on live-weight. Purity of copper sulphate did not affect growth rate, feed conversion efficiency or carcass measurements in either experiment. Response to level of copper sulphate between about 45 and 100 lb. liveweight differed somewhat between experiments. In Experiment 1 pigs receiving 125 or 250 p.p.m. in the diet grew 4 or 9% faster and had better feed conversion efficiencies than those receiving 16 or 62 p.p.m. Cu. In Experiment 2, pigs receiving 62, 125 or 250 p.p.m. Cu all grew about 4–5% faster and had 1–5 % better feed conversion efficiencies than those receiving 16 p.p.m. Cu, but the effect on feed conversion efficiency was not statistically significant. Increase in copper sulphate above the trace level supplying 16 p.p.m. Cu in the diet had no effect on growth rate or feed conversion efficiency between 100 and 202 lb. live-weight or on killing-out percentage or carcass measurements. Comparison of the results with those from a previous experiment showed that in pigs fed according to a fixed scale the greatest consistent increases in growth rate and feed conversion efficiency have occurred with copper sulphate as 0·1% of the diet, giving 250 p.p.m. Cu. This supplement has only improved performance between 100 and 200 lb. live-weight in one experiment out of five.

The early weaning of pigs. VIII. Copper sulphate as a growth stimulant

The effects of copper supplements on the performance up to 45 lb. live weight of early weaned pigs were measured in two experiments. Copper sulphate included as 0·1% of the diet had no apparent adverse effect on the piglets, even when it was introduced immediately after weaning at about 8 lb. live weight, but improved rate of gain by 6 and 12% and feed conversion efficiency by 5 and 6% in the two experiments, respectively. The length of the period of slow growth after weaning was reduced in both experiments. There was no clear advantage in delaying the introduction of the high-copper diet until the pigs weighed 17 or 26 lb. The second experiment was a 2 x 2 factorial, the second factor being the presence or absence in the diet of antibiotic (present throughout in the first experiment). Antibiotic appeared to have slight beneficial effects on growth rate and feed conversion, which were additive to the effects of copper so that the best results were obtained from the diet containing both copper and antibiotic. In a continuation of the first experiment it was found that the early copper treatment had no effect on rates of gain and feed conversion between 55 and 200 lb. live weight or on carcass measurements. The inclusion of a copper supplement in the diet from 55 to 200 lb. improved feed conversion by 4% and rate of gain by 3·5%, reduced the thickness of streak and increased the ratio of width to depth of eye muscle. None of these responses was affected by the copper treatment prior to 55 lb. live weight.

A note on the growth of pigs in metabolism cages.

The growth of pigs kept continuously or intermittently in metabolism cages was compared with that of animals penned in groups. The ten continuously caged grew more slowly and contained more fat at slaughter than their penned littermates.

A note on the effect of sudden changes in the composition of the diet of growing pigs

Two diets, one based on barley and white-fish meal and the other on oats, wheat and meat and bone meal, with similar concentrations of digestible energy, crude protein, lysine and methionine+cystine were used to investigate the effects of sudden changes in the composition of the diet on the performance of pigs growing from 32 kg live weight, over a period of 77 days. The diets were given separately, alternated weekly with sudden changes from one diet to the other, or as a 1:1 mixture. Changes in diet per se had insignificant effects on performance.