A major constraint to protein deposition in the pig is energy intake. Ractopamine (RAC) isa b-agonist which has been shown to increase protein deposition under both ad libitum and restrictive feeding regimes. To assess the interactions between energy intake, sex, and dietary RAC, 104 crossbred pigs (52 boars and 52 gilts) were used in a slaughter-balance experiment conducted over the growth phase of 60-90 kg liveweight. To obtain initial body composition, 4 pigs of each sex were slaughtered at 60 kg. The remaining 96 pigs were allocated to a 2 6 2 factorial experiment. The respective factors were sex (boar or gilt), dietary digestible energy (DE) intake (21·2, 24·7, 28·2, 32·7, 36·7MJ DE/day and ad libitum), and dietary RAC (0 and 20 mg/kg of ractopamine.HCl). Average daily gain increased with DE intake and was faster for boars than gilts. Dietary RAC increased averagedaily gain in both boars and gilts independent of DE intake. Neither dietary RAC nor sex had any effect on ad libitum feed intakes while effects on feed : gain ratio reciprocated growth rates. Protein deposition increased with DE intake and was higher in boars than in gilts. Although protein deposition was increased by dietary RAC in both boars and gilts across the range of DE intakes investigated,ad libitum feed intakes were necessary to maximise protein deposition. Fat deposition increased with DE intake and was greater in gilts than in boars. Whereas dietary RAC had no effect on the rateof fat deposition or backfat depths, the fat content of the empty body was lower due to increased protein deposition and lower fat : protein ratio. Dietary RAC improves growth performance and carcass composition in both boars and gilts independent of DE intake. However, ad libitum feed intakes maybe necessary if responses are to be maximised.

Twelve Large White × Landrace sows nursing litters of 6 boars and 6 gilts were used in this study. Six litters suckled the sow only, whereas the other 6 litters received supplemental liquid skim milk (200 g/L) ad libitum from Day 10 until Day 20. On Day 20 the 4 heaviest pigs of each sex were allocated to 2 pairs and were weaned. Each pair was offered either pelleted or pelleted plus liquid feed. For the first 2 days post-weaning, each pair of liquid-supplemented pigs received liquid skim milk (250 g/L). On Day 23, pelleted feed was added to the milk. The ratio of liquid to pelleted feed was adjusted daily until, on Day 28, pigs were provided with pelleted feed only until 41 days of age. Supplemental skim milk increased growth (223 v. 291 g/day, P < 0.001) between Days 10 and 20 of age so that by weaning supplemented pigs were 10% (6.13 v. 6.74 kg, P = 0.038) heavier than unsupplemented pigs. Skim milk intake increased linearly from 190 to 600 g/day per pig over the 10 days of supplementation. Supplemental milk feeding did not alter sow liveweight change (−31.9 v. −30.3 kg for sows nursing litters with and without supplementation, respectively, P = 0.894) or change in P2 backfat thickness (−5.3 v. −4.2 mm, P = 0.279) between farrowing and Day 20 of age. Pigs weaned onto skim milk and pellets ate more (257 v. 30 g dry matter (DM)/day, P < 0.001) and grew better (213 v. −151 g/day, P < 0.001) over the first 2 days post-weaning than pigs weaned onto only pellets. Piglets provided with liquid feed after weaning continued to grow faster beyond Day 22, resulting in the benefit of weaning onto liquid feed being maintained until at least 41 days of age (14.1 v. 12.8 kg, P < 0.001). In conclusion, skim milk feeding before and after weaning can result in cumulative improvements in growth performance in the nursery.

A Hologic QDR4500W dual energy X-ray absorptiometer (DXA) was used to measure body composition in 60 sheep half carcasses ranging from 8 to 28 kg. Half carcasses were from ewes and wethers of mixed genetics. Values determined by DXA, including total tissue mass (TTM), lean tissue mass (LTM), fat tissue mass (FTM) and bone mineral content (BMC), for the half carcass were evaluated by comparison with chemically determined composition. In the case of BMC, the relationship was with chemically determined ash content. Liveweight and chemically determined lean, fat and ash were strongly related to DXA-derived values for TTM, LTM, FTM and BMC, respectively (R2 = 0.999, 0.986, 0.989 and 0.920, respectively). However, because DXA estimates were different from chemically determined values in this sample of carcasses, they needed to be adjusted with the use of appropriate regression equations to correct the in-built algorithms. These data demonstrate the efficacy of DXA as a non-destructive method for determining the composition of the sheep half carcass.

A production experiment was conducted with 96 fourteen-day-old weaned male piglets to compare diets containing preparations of freeze-dried porcine plasma (P) and freeze-dried bovine colostrum (C) for 35 days after weaning. These diets were compared with a diet consisting of soybean meal (SP) and a diet with animal protein sources (AP). All diets contained varying proportions of bloodmeal, fishmeal, meat and bone meal, and skim milk powder. The levels of colostrum and porcine plasma were reduced from 60 g/kg to 25 g/kg after the first week of weaning. There were no effects of diet on performance in the first 4 days after weaning. However, between 18 and 21 days of age, pigs fed the SP diet ate less (P < 0.001) and grew slower (P = 0.002) than pigs fed diets containing AP, C, or P. In the second week after weaning, pigs fed diets with C and P showed a tendency to perform better (P�=�0.11) than those fed AP or SP. By 35 days of age, pigs fed diets containing colostrum and plasma were, on average, 6% heavier (P = 0.037) than pigs fed the AP and SP diets. The effects of dietary protein on voluntary feed intake were most pronounced up to 28 days of age in pigs fed the SP diet. There appeared little benefit of feeding C and P to early-weaned pigs over feeding a predominantly animal protein diet, although daily gain was 6% less (P�= 0.47). There were no differences (P > 0.05) in feed intake and growth rate between 28 and 35 days of age, and feed conversion efficiency was not altered by dietary protein source. Under these experimental conditions the use of bovine colostrum and a combination of animal protein sources was comparable with using freeze-dried porcine plasma in diets for early-weaned pigs. Inclusion of soybean meal in diets, however, resulted in inferior performance.

Five hundred and ten multiparous sows were allocated at 66 days after mating to one of 6 dietary treatments that were imposed for the subsequent 35 days. The dietary treatments were 5 feeding levels of 2.2, 2.6, 3.0, 3.4, and 3.8 kg/day of a gestation diet containing 12.9 MJ DE/kg, 127 g crude protein/kg, and 5.6 g lysine/kg, plus a protein intake treatment where sows received 2.8 kg/day of a lactation diet containing 13.8 MJ DE/kg, 168 g crude protein/kg, and 8.3 g lysine/kg. After the treatment period, all sows were offered the lactation diet at the common feeding level of 3.0 kg/day and after farrowing, all sows were offered this diet ad libitum throughout lactation. Increasing feeding levels between Day 66 and Day 101 of pregnancy increased (P < 0.001) liveweight gain prior to farrowing but increased (P < 0.001) liveweight loss during lactation. The majority of the extra maternal energy intake during mid to late gestation was deposited as maternal gain. These linear weight responses during lactation were explained by the significant inverse relationship between voluntary daily feed intake in lactation (FI) and average daily digestible energy intake in the previous gestation (DE): Neither increasing the feeding level during mid to late gestation nor increasing the protein content of the diet had any significant effect on litter birth weight, average piglet birth weight, or the standard deviation of individual piglet birth weight within the litter. In addition, there were no significant effects of gestation feeding treatments on litter size weaned or weaning weight. Furthermore, neither increasing the feeding level during mid to late gestation nor increasing the protein content of the gestation diet had any significant effect on subsequent fertility or litter size. In conclusion, when average individual piglet birth weight is already well in excess of 1.5 kg, there is no significant response to feed intake levels between 2.2 and 3.8 kg/day when offered between Day 66 and Day 101 of gestation.