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Much of our understanding of energy metabolism in the pig has been derived from studies in which the energy supply was controlled through regulated feed intake. In commercial situations, where ad libitum feeding is practiced, dietary energy concentration, but not daily feed intake, is under producer control. This study evaluated the interactive effects of dietary energy concentration and feeding level (FL) on growth, body composition, and nutrient deposition rates. Individually penned PIC barrows, with an initial BW of 9.5 +/- 1.0 kg, were allotted to 1 of 9 treatments in a 3 x 3 factorial arrangement plus an initial slaughter group (n = 6) that was slaughtered at the beginning of the trial. Three NE concentrations (low, 2.15; medium, 2.26; and high, 2.37 Mcal of NE/kg) and 3 feeding levels (FL: 100, 80, or 70% of ad libitum access to feed) were investigated. Daily feed allowance for the restricted-fed pigs was adjusted twice per week on a BW basis until completion of the experiment at 25 +/- 1 kg of BW. Average daily gain, ADFI, and G:F were unaffected by NE (mean = 572 g, 781 g, and 0.732 g/g, respectively). Average daily gain and ADFI, but not G:F, increased (P < 0.05) with FL. Empty body lipid concentration increased with dietary NE concentration and with FL; a significant (P < 0.01) interaction revealed that empty body lipid concentration increased most rapidly as ADFI increased on the highest energy diet. Empty body lipid concentration was greatest in pigs with ad libitum access to the high-NE diet. Empty body protein concentration decreased with increasing NE (P < 0.05) but was not affected by FL. Empty body protein deposition (PD) increased with increasing FL (P < 0.001), but not with NE. Empty body lipid deposition (LD) and the LD:PD ratio increased (P < 0.01) in pigs with ad libitum access to the high-NE diet. In conclusion, NE did not interact with FL on growth, body protein concentration, or PD, suggesting that the conclusions regarding energy utilization obtained from experiments using restricted feed intake may not easily be applied to pigs fed under ad libitum conditions. The interactive effects of NE and FL on body lipid concentration, LD, and the LD:PD ratio indicate that changes in dietary energy concentration alter the composition of gain without necessarily changing overall BW gain. Consequently, the composition of gain is an important outcome in studies on energy utilization.

Amino acids should be defined in relation to dietary energy concentration in diets for young pigs. However, the literature contains diverse estimates of the optimum lysine:digestible energy (DE) ratio for weanling pigs performing at levels commonly observed in commercial practice. Further, there is a poor understanding of the reponse of the weanling pig to dietary energy concentration. A growth experiment was conducted to define the optimum total lysine:DE ratio for pigs from 4 to 8 wk of age. Dietary treatments were arranged as a 2 × 5 factorial: low (LDE, 3.4 Mcal kg-1) or high DE (HDE, 3.6 Mcal kg-1) and the following total lysine:DE ratios: 3.7, 4.0, 4.3, 4.6, or 4.9 g Mcal-1). The experiment ran for 28 d, beginning 7 d post-weaning, using four pigs per pen and six pens per diet for a total of 240 pigs (27 ± 2 d; 7.5 ± 1.1 kg). No DE × lysine:DE ratio interactions were detected for any performance parameter (P > 0.05). The average daily feed intake (ADFI) was 4% greater with pigs on LDE than HDE diets (DE,P < 0.05), but was not affected by lysine:DE ratio (P > 0.05). Conversely, DE did not affect average daily gain (ADG) (P > 0.05), but increased quadratically (day 0 to 14; P < 0.05) and (day 0 to 28; P < 0.10) with increasing lysine:DE ratio. Feed efficiency increased linearly with increasing lysine:DE ratio (P < 0.05) and was 4% greater with the HDE than LDE diets (P < 0.05). The optimum total lysine:DE ratio for ADG was determined to be 4.46 and 4.27 g Mcal-1 for pigs between 7.5 to 13 kg and 7.5 to 22.5 kg BW, respectively. Key words: Pig, total lysine, digestible energy, growth

Amino acid intake declined either in constant proportion to energy or at a reduced rate when feed intake treatments represented 100, 70, 60 or 50% of ad libitum. Amino acid intake affected feed conversion, and energy and lysine utilization (P < 0.05). Energy studies involving feed restriction may be confounded by amino acid supply. Key words: Pigs, energy intake, amino acid intake

The present study investigated the effect of ergot alkaloids on performance and clinical symptoms in weaned pigs. Wheat ergot sclerotia (1880 mg alkaloid kg-1; ergocristine, ergotamine, ergosine, ergocryptine, and ergocornine constituting 40, 36, 11, 7, and 6% of the total, respectively) were added on a weight basis to a basal diet at 0.00 (control), 0.05, 0.10, 0.25, 0.50, and 1.00% and fed to 192 weaned pigs (20.4 ± 3.4 d; 6.9 ± 1.3 kg; mean ± SD) for 28 d, beginning 7 d post-weaning. Pigs fed the 1.00% diet gained 82 and 38% less than the control (P < 0.001, 211 vs. 39 g d-1, wk 1 and 432 vs. 269 g d-1, wk 2) and body weight on day 28 was reduced quadratically by alkaloids (P < 0.005). Ergot alkaloids decreased average daily feed intake (ADFI) quadratically (P < 0.04) and feed efficiency linearly (P < 0.03) (0.62 vs. 0.44; control vs. 1.00%) over the entire period, but ADFI was not affected during the initial 14 d (P > 0.20). Ergot alkaloids decreased serum prolactin quadratically (P < 0.002) and urea nitrogen concentrations (P < 0.05). The maximum tolerable ergot level in the diet was 0.10 and 0.05% based on average daily gain (ADG) and ADFI, respectively, corresponding to 2.07 mg and 1.04 mg alkaloid kg-1 diet. Key words: Pig, ergot, alkaloid, toxicity, performance, prolactin

Much of our understanding of energy metabolism in the pig has been derived from studies in which the energy supply was controlled through regulated feed intake. In commercial situations, where ad libitum feeding is practiced, dietary energy concentration, but not daily feed intake, is under producer control. This study evaluated the interactive effects of dietary energy concentration and feeding level (FL) on growth, body composition, and nutrient deposition rates. Individually penned PIC barrows, with an initial BW of 9.5 +/- 1.0 kg, were allotted to 1 of 9 treatments in a 3 x 3 factorial arrangement plus an initial slaughter group (n = 6) that was slaughtered at the beginning of the trial. Three NE concentrations (low, 2.15; medium, 2.26; and high, 2.37 Mcal of NE/kg) and 3 feeding levels (FL: 100, 80, or 70% of ad libitum access to feed) were investigated. Daily feed allowance for the restricted-fed pigs was adjusted twice per week on a BW basis until completion of the experiment at 25 +/- 1 kg of BW. Average daily gain, ADFI, and G:F were unaffected by NE (mean = 572 g, 781 g, and 0.732 g/g, respectively). Average daily gain and ADFI, but not G:F, increased (P0.05) with FL. Empty body lipid concentration increased with dietary NE concentration and with FL; a significant (P0.01) interaction revealed that empty body lipid concentration increased most rapidly as ADFI increased on the highest energy diet. Empty body lipid concentration was greatest in pigs with ad libitum access to the high-NE diet. Empty body protein concentration decreased with increasing NE (P0.05) but was not affected by FL. Empty body protein deposition (PD) increased with increasing FL (P0.001), but not with NE. Empty body lipid deposition (LD) and the LD:PD ratio increased (P0.01) in pigs with ad libitum access to the high-NE diet. In conclusion, NE did not interact with FL on growth, body protein concentration, or PD, suggesting that the conclusions regarding energy utilization obtained from experiments using restricted feed intake may not easily be applied to pigs fed under ad libitum conditions. The interactive effects of NE and FL on body lipid concentration, LD, and the LD:PD ratio indicate that changes in dietary energy concentration alter the composition of gain without necessarily changing overall BW gain. Consequently, the composition of gain is an important outcome in studies on energy utilization.