Determination of the optimum digestible isoleucine to lysine ratios for male Yield Plus × Ross 708 broilers between 1.0 and 4.0 kg body weight utilizing growth performance and carcass characteristics.

Three experiments (Exp) were conducted to determine optimal digestible Ile to Lys ratios for male Yield Plus × Ross 708 broilers from approximately 1.0 to 4.0 kg BW. Broilers were fed dose-response diets with inclusions of blood cells that were formulated to contain a gradient of digestible Ile to Lys ratios (0.46 to 0.83). Treatments for Exp 1 to 3 were fed from 21 to 35, 28 to 42, and 35 to 49 d of age, respectively, to target market weights from 2.5 to 4.0 kg. Experiments utilized positive control (PC) diets that did not contain blood cells and were formulated to the same Ile ratios as Treatment 5. Birds and feed were weighed by pen on the first and last days of the experimental period to determine growth performance. Selected broilers were processed and deboned to determine carcass characteristics. For all Exp, quadratic effects (P ≤ 0.001) were observed with BW gain, feed conversion ratio (FCR), breast meat weight, and breast meat yield (BMY) as digestible Ile to Lys ratios increased. Contrasts between PC and Treatment 5 for each Exp displayed no effect of blood cell inclusion with the exception of FCR in Exp 1 (P = 0.001) and BMY in Exp 3 (P = 0.017). Optimum digestible Ile to Lys ratios for Exp 1 were determined to range from 0.640 to 0.725 for growth from 1.0 to 2.5 kg BW (P ≤ 0.001) and breast meat characteristics. In Exp 2, optimum ratios ranged from 0.664 to 0.682 for growth and breast meat characteristics from 1.6 to 3.1 kg BW (P ≤ 0.001). For growth and breast meat characteristics of broilers in Exp 3, optimum ratios ranged from 0.625 to 0.730, from 2.6 to 3.9 kg BW (P ≤ 0.001). Based on these findings, optimum digestible Ile to Lys ratios were determined to range from 0.63 to 0.73 for broilers from 1.0 to 4.0 kg BW.

Dose-response evaluation of the standardized ileal digestible tryptophan : lysine ratio to maximize growth performance of growing-finishing gilts under commercial conditions.

Environmental regulations as well as economic incentives have resulted in greater use of synthetic amino acids in swine diets. Tryptophan is typically the second limiting amino acid in corn-soybean meal-based diets. However, using corn-based co-products emphasizes the need to evaluate the pig's response to increasing Trp concentrations. Therefore, the objective of these studies was to evaluate the dose-response to increasing standardized ileal digestible (SID) Trp : Lys on growth performance of growing-finishing gilts housed under large-scale commercial conditions. Dietary treatments consisted of SID Trp : Lys of 14.5%, 16.5%, 18.0%, 19.5%, 21.0%, 22.5% and 24.5%. The study was conducted in four experiments of 21 days of duration each, and used corn-soybean meal-based diets with 30% distillers dried grains with solubles. A total of 1166, 1099, 1132 and 975 gilts (PIC 337×1050, initially 29.9±2.0 kg, 55.5±4.8 kg, 71.2±3.4 kg and 106.2±3.1 kg BW, mean±SD) were used. Within each experiment, pens of gilts were blocked by BW and assigned to one of the seven dietary treatments and six pens per treatment with 20 to 28 gilts/pen. First, generalized linear mixed models were fit to data from each experiment to characterize performance. Next, data were modeled across experiments and fit competing dose-response linear and non-linear models and estimate SID Trp : Lys break points or maximums for performance. Competing models included broken-line linear (BLL), broken-line quadratic and quadratic polynomial (QP). For average daily gain (ADG), increasing the SID Trp : Lys increased growth rate in a quadratic manner (P<0.02) in all experiments except for Exp 2, for which the increase was linear (P<0.001). Increasing SID Trp : Lys increased (P<0.05) feed efficiency (G : F) quadratically in Exp 1, 3 and 4. For, ADG the QP was the best fitting dose-response model and the estimated maximum mean ADG was obtained at a 23.5% (95% confidence interval (CI): [22.7, 24.3%]) SID Trp : Lys. For maximum G : F, the BLL dose-response models had the best fit and estimated the SID Trp : Lys minimum to maximize G : F at 16.9 (95% CI: [16.0, 17.8%]). Thus, the estimated SID Trp : Lys for 30 to 125 kg gilts ranged from a minimum of 16.9% for maximum G : F to 23.5% for maximum ADG.

Modeling the effects of standardized ileal digestible isoleucine to lysine ratio on growth performance of nursery pigs.

Two experiments evaluated the effects of increasing standardized ileal digestible (SID) Ile:Lys ratio on growth performance of nursery pigs. In both experiments, dietary treatments consisted of 40, 44, 48, 52, 54, 58, or 63% SID Ile:Lys ratio. Diets were formulated using analyzed ingredient AA values and NRC (2012) SID coefficients. A combination of field peas and spray dried blood cells were used to ensure a low enough Ile diet concentration while minimizing the excess of Leu. The experiments consisted of 8 pens per dietary treatment with 5 pigs per pen for a total of 280 nursery pigs per experiment (Exp. 1: PIC 327 × 1,050, initially 6.7 ± 1.0 kg BW; Exp. 2: DNA 600 × 241, initially 6.0 ± 0.97 kg BW). Data were analyzed using mixed models with heterogeneous variance, where appropriate. The dose response was further characterized using quadratic polynomial (QP), broken-line linear (BLL), or broken-line quadratic (BLQ) functional forms. For Exp. 1, diets were initiated 6-d post-weaning and fed for 12-d followed by a common diet from d 12 to 28. From d 0 to 12, increasing dietary SID Ile:Lys ratio increased ADG (linear, P < 0.005) and ADFI (quadratic, P < 0.017) but G:F decreased (quadratic, P < 0.043). For ADG, the QP, BLL, and BLQ models resulted in maximum ADG at 64.7, 52.0, and 52.0 SID Ile:Lys ratios, respectively. For ADFI, the BLL breakpoint occurred at 50.6 and the QP predicted maximum ADFI at 56.2 SID Ile:Lys ratio. In Exp. 2, diets were initiated 6-d post-weaning for 7 pens and 3-d post-weaning for one heavier block and fed for 18-d followed by a common diet from d 18 to 32. From d 0 to 18, ADG and ADFI increased (quadratic, P < 0.016) with no evidence for difference in G:F as SID Ile:Lys ratio increased. For ADG, the QP and BLL had similar fit with breakpoints or maximums occurring at 58.3 and 51.8% SID Ile:Lys ratio, respectively. For ADFI, the BLQ breakpoint occurred at 52.0 SID Ile:Lys and the QP maximum ADFI at 57.2% SID Ile:Lys ratio. In conclusion, broken-line models reported maxima of 52.0% Ile:Lys ratio while quadratic models were as high as 64% of Lys to maximize ADG and ADFI of 6- to 11-kg nursery pigs. However, for the QP models 99% of the maximum response was achieved with a dose comparable to that from the broken line models. Therefore, these results are similar to the NRC (2012) requirement estimate of 51.1 Ile:Lys ratio.

Modeling the effects of standardized ileal digestible valine to lysine ratio on growth performance of nursery pigs.

Two experiments evaluated the effects of increasing Lys and Val on growth performance of nursery pigs. In Exp. 1,300 nursery pigs (PIC 327 × 1,050, initially 6.7 ± 1.4 kg BW) were randomly allotted to 1 of 6 diets containing 1.10, 1.20, 1.30, 1.40, 1.50, or 1.60% standardized ileal digestible (SID) Lys, with 10 pens per dietary treatment and 5 pigs per pen. Linear and nonlinear mixed models were fitted to estimate dose responses. From d 0 to 14, and for the overall 28 d period, ADG and G:F increased (linear, P < 0.001) as SID Lys increased, with no evidence of differences in ADFI. Dose response modeling indicated the SID Lys requirement for ADG and G:F was at 1.45% using a broken line linear (BLL) and greater than 1.60% using a quadratic polynomial (QP) model. In Exp. 2, 280 nursery pigs (PIC 327 × 1,050, initially 6.5 ± 1.3 kg BW) were allotted to 1 of 7 diets containing SID Val:Lys ratios of 50, 57, 63, 68, 73, 78, or 85%. The dietary SID Lys concentration 1.24% SID Lys which was below the estimated requirement from Exp. 1 and ensured the Val:Lys ratio was not underestimated. From d 0 to 14, ADG, ADFI, and G:F increased (quadratic, P < 0.039) with increasing SID Val:Lys. For ADG, the best fitting model was a BLL, with a breakpoint estimate of 62.9% SID Val:Lys [52.2, 73.7] ratio while for G:F the best fit model was a quadratic polynomial with a maximum G:F at 71.7% SID Val:Lys (95%CI:[58, > 85]). Average daily feed intake was also modeled with a quadratic polynomial and maximized at 73.7% Val:Lys (95% CI: [61, > 85]). In conclusion, the Val requirement ranged from approximately 63 to 74% of Lys depending on the response criteria modeled.

Evaluation of the optimal standardized ileal digestible tryptophan:lysine ratio in lactating sow diets.

Three hundred and fifteen primiparous and multiparous sows were evaluated in a study to determine the effect of standardized ileal digestible (SID) Trp:Lys ratio in lactating sow diets. Camborough sows (PIC USA, Hendersonville, TN) ranging from first parity to eighth parity were blocked by parity and randomly allotted to 1 of 4 experimental diets containing different levels of added L-Trp (0.006, 0.026, 0.045, and 0.064%, respectively) while soybean meal, 30% corn dried distiller's grain with solubles (DDGS), and L-Lys levels were held constant. The SID Lys level for the rations was 0.95% so that the SID Trp:Lys ratios were formulated to be 14, 16, 18, and 20%, respectively. All diets were formulated to have 3.2 Mcal ME/kg and to contain vitamins and minerals that exceeded NRC (1998) recommendations. Sows were fed twice a day with a Howema computerized feed system and were allowed a maximum intake (5.9 kg/d). Average daily feed intake had a tendency to be quadratically improved when the SID ratio was increased (5.11, 5.28, 5.24, 5.21 kg/d, P = 0.09). In addition, sow wean to estrus (6.71, 5.53, 5.58, 6.33, P < 0.02) was quadratically improved as SID Trp:Lys ratio increased. Percent of sows bred by 10 d (84.39, 90.82, 90.28, 90.61) was not linearly (P = 0.25) or quadratically (P = 0.40) improved. There was no difference in litter gain (2.44, 2.52, 2.60, 2.57 kg/d, P = 0.16). Based on a broken-line quadratic model, when sows are fed 30% DDGS, the SID Trp:Lys ratio of 17.6 is required for optimal sow average daily feed intake and 17.2 for wean to estrus interval.

Effects of dietary fiber on the ideal standardized ileal digestible threonine:lysine ratio for twenty-five to fifty kilogram growing gilts.

Four experiments were conducted to determine effects of fiber on the ideal Thr:Lys ratio for 25- to 50-kg gilts. In Exp. 1, the objective was to determine the requirement for standardized ileal digestible Lys for gilts from 25 to 50 kg BW. Seventy gilts (24.54 ± 3.28 kg BW) were used in a growth assay with 2 pigs per pen, 5 diets, and 7 replicate pens per diet. The 5 diets were based on corn and soybean meal and contained between 0.80 and 1.32% SID Lys. Results indicated that 1.09% SID Lys was needed to optimize ADG and G:F. In Exp. 2, the objective was to determine the standardized ileal digestibility of AA in corn, soybean meal, field peas, fish meal, and soybean hulls. Six ileal-cannulated gilts (26.5 ± 0.74 kg BW) were allotted to a 6 × 6 Latin square design with 6 diets and 6 periods. Values for standardized ileal digestibility of AA were calculated for all ingredients. In Exp. 3, the objective was to determine the effect of fiber on the ideal SID Thr:Lys ratio for gilts from 25 to 50 kg BW. A total of 192 gilts (26.29 ± 4.64 kg BW) were used in a growth assay with 2 pigs per pen and 8 replicate pens per treatment. Six low-fiber diets and 6 high-fiber diets were formulated using the same batches of ingredients as in Exp. 2. Within each level of fiber, diets with SID Thr:Lys ratios ranging from 45:100 to 90:100 were formulated using the SID values calculated in Exp. 2. In both types of diets, ADG and G:F linearly and quadratically ( < 0.05) increased as the Thr:Lys ratio increased. Regression analysis estimated the ideal SID Thr:Lys ratio at 0.66 and 0.63 for ADG and G:F, respectively, for pigs fed low-fiber diets and at 0.71 and 0.63, respectively, for pigs fed high-fiber diets. In Exp. 4, the objective was to determine the N balance in pigs fed low-fiber or high-fiber diets that were formulated to have SID Thr:Lys ratios of 45:100 or 60:100. The 4 diets were formulated using the same batches of ingredients as in Exp. 2, and the SID values determined in Exp. 2 were used in diet formulations. Thirty-six gilts (29.0 ± 0.74 kg BW) were individually housed in metabolism crates with 9 replicate pigs per diet. Retention of N (% of intake) was greater (P < 0.05) for pigs fed the low-fiber diets compared with pigs fed the high-fiber diets regardless of the Thr:Lys ratio. Results of these experiments indicate that increased fiber levels in diets fed to growing gilts increase the requirement for Thr and that diets with higher fiber levels should be formulated to a greater SID Thr:Lys ratio.

Effects of standardized ileal digestible tryptophan: lysine ratio on growth performance of nursery pigs.

Two experiments were conducted to estimate the standardized ileal digestible (SID) Trp:Lys ratio requirement for growth performance of nursery pigs. Experimental diets were formulated to ensure that lysine was the second limiting AA throughout the experiments. In Exp. 1 (6 to 10 kg BW), 255 nursery pigs (PIC 327 × 1050, initially 6.3 ± 0.15 kg, mean ± SD) arranged in pens of 6 or 7 pigs were blocked by pen weight and assigned to experimental diets (7 pens/diet) consisting of SID Trp:Lys ratios of 14.7%, 16.5%, 18.4%, 20.3%, 22.1%, and 24.0% for 14 d with 1.30% SID Lys. In Exp. 2 (11 to 20 kg BW), 1,088 pigs (PIC 337 × 1050, initially 11.2 kg ± 1.35 BW, mean ± SD) arranged in pens of 24 to 27 pigs were blocked by average pig weight and assigned to experimental diets (6 pens/diet) consisting of SID Trp:Lys ratios of 14.5%, 16.5%, 18.0%, 19.5%, 21.0%, 22.5%, and 24.5% for 21 d with 30% dried distillers grains with solubles and 0.97% SID Lys. Each experiment was analyzed using general linear mixed models with heterogeneous residual variances. Competing heteroskedastic models included broken-line linear (BLL), broken-line quadratic (BLQ), and quadratic polynomial (QP). For each response, the best-fitting model was selected using Bayesian information criterion. In Exp. 1 (6 to 10 kg BW), increasing SID Trp:Lys ratio linearly increased ( 0.05) ADG and G:F. For ADG, the best-fitting model was a QP in which the maximum ADG was estimated at 23.9% (95% confidence interval [CI]: [<14.7%, >24.0%]) SID Trp:Lys ratio. For G:F, the best-fitting model was a BLL in which the maximum G:F was estimated at 20.4% (95% CI: [14.3%, 26.5%]) SID Trp:Lys. In Exp. 2 (11 to 20 kg BW), increasing SID Trp:Lys ratio increased ( 0.05) ADG and G:F in a quadratic manner. For ADG, the best-fitting model was a QP in which the maximum ADG was estimated at 21.2% (95% CI: [20.5%, 21.9%]) SID Trp:Lys. For G:F, BLL and BLQ models had comparable fit and estimated SID Trp:Lys requirements at 16.6% (95% CI: [16.0%, 17.3%]) and 17.1% (95% CI: [16.6%, 17.7%]), respectively. In conclusion, the estimated SID Trp:Lys requirement in Exp. 1 ranged from 20.4% for maximum G:F to 23.9% for maximum ADG, whereas in Exp. 2 it ranged from 16.6% for maximum G:F to 21.2% for maximum ADG. These results suggest that standard recommendations may underestimate the SID Trp:Lys requirement for nursery pigs from 11 to 20 kg BW.

Effects of weaning and weaning weight on neuroendocrine regulators of feed intake in pigs.

A depression in feed intake and growth often occurs in the weaned pig. Spray-dried plasma is often added to nursery diets in an attempt to stimulate feed intake during this lag. The current study evaluated gene expression of appetite regulators in hypothalamus and adipose tissue 4 d after weaning. Barrows (2 wk of age) were cross-fostered to a sow (SOW, n = 8) or weaned and fed a nursery diet containing either 0 or 7% spray-dried plasma (NP, n = 8, and SDP, n = 8, respectively). Piglets were allocated such that 2 size groups existed within each experimental group: small (3.5 to 4.3 kg of BW piglets) and large (4.6 to 5.7 kg of BW piglets) subsets, based on weaning weight (WW), existed within each experimental group: small (3.5 to 4.3 kg piglets) and large (4.6 to 5.7 kg piglets). Animals were killed 4 d after weaning for tissue collection. There was a weaning group x WW interactive effect (P < 0.05) on hypothalamic neuropeptide Y messenger RNA expression, such that expression was least in the small SDP piglets. No WW or weaning group effects were seen on adipose leptin, hypothalamic leptin receptor, or hypothalamic proopiomelanocortin gene expression. An effect of WW was seen on hypothalamic neuropeptide Y, agouti-related protein, orexin, and type 2 orexin receptor gene expression, such that large pigs expressed greater amounts of these transcripts (P < 0.002). Strong positive correlations in gene expression were found among all of these genes, whose products are known to stimulate appetite. Partial correlation controlling for initial WW revealed that preweaning size explained most if not all of these associations. These data suggest that the postweaning expression of appetite-regulating genes is more dependent on preweaning conditions than on weaning diet.

The dietary valine requirement for prolific lactating sows does not exceed the National Research Council estimate.

Two studies were conducted to determine the effect of increasing the valine:lysine (V:L) ratio in diets of lactating sows above the minimum proposed by the NRC (1998). The first experiment involved 189 PIC, Camborough product sows (parity 1 to 4) that were allotted to 1 of 3 dietary treatments. Diets were formulated to achieve total dietary V:L ratios of 0.90, 1.05, or 1.25:1, respectively, and were corn and soybean meal-based. The second experiment involved 279 PIC, Camborough sows (parity 1 to 5) that were allotted to 1 of 4 treatments. Diets 1 and 3 were formulated using corn and a fixed inclusion of soybean meal (16.7%), with 0.27% L-lysine HCl. The V:L ratios in diets 1 and 3 were 0.73 and 1.25:1, respectively. Diets 2 and 4 were typical corn-soybean meal diets containing 0.05% L-lysine HCl, with a fixed inclusion of soybean meal (22.7%). The V:L ratios in diets 2 and 4 were 0.86 and 1.25:1, respectively. In both experiments, each litter was standardized to a minimum of 10 pigs, which achieved litter growth rates of 2.22 and 2.56 kg/d in Exp. 1 and 2, respectively. In Exp. 1, increasing the dietary V:L ratio beyond 0.90:1 did not improve (P > 0.10) the number of pigs weaned, survival rate, or piglet growth rate, even though sows were nursing more than 10 pigs per litter for 19 d. In Exp. 2, total lysine intake was similar among treatments and ranged from 52.1 to 55.3 g/d. Valine intake increased as the diet valine concentration increased (diet 1 vs. 3 and diet 2 vs. 4, P < 0.001), ranging from 40.0 to 66.1 g/d. Litter gain tended to improve (P = 0.14) when the 0.27% L-lysine HCl control (0.73 V:L) was supplemented with valine to achieve a 1.25:1 V:L ratio. In contrast, no aspect of sow or litter response was improved when the practical control diet containing 0.05% L-lysine HCl (0.86 V:L) was supplemented with valine to achieve a 1.25:1 V:L ratio. Collectively, this research shows that a V:L ratio in excess of 0.86 does not conserve maternal tissue loss or improve piglet growth rate, but a V:L ratio of 0.73 may compromise litter growth rate.

Pigs weaned from the sow at 10 days of age respond to dietary energy source of manufactured liquid diets and exogenous porcine somatotropin.

Previous research indicates that the neonatal pig does not alter feed intake in response to changes in the energy density of manufactured liquid diets. Also, the limited response of IGF-I to exogenous porcine ST (pST) previously observed in young pigs may be influenced by the source of dietary energy. Our objectives were to 1) determine the effect of a high-fat (HF; 25% fat and 4,639 kcal/kg ME; DM basis) or low-fat (LF; 2% fat and 3,481 kcal/kg ME; DM basis) manufactured liquid diet on pig performance; and 2) determine whether the limited response to exogenous pST in young pigs depends on the source of dietary energy. Two replicates of 60 pigs (n = 120; barrows and gilts distributed evenly), with an initial BW of 4,207 +/- 51 g, were weaned from the sow at 10 d of age and used in a randomized complete block design. Pigs were assigned by BW to one of six pens. Diets were formulated to provide a constant lysine:ME ratio and were fed on a pen basis for a duration of 9 d. On d 5, barrows and gilts within a pen were assigned randomly to receive either 0 or 120 microg of pST.kg BW(-1).d(-1) for 4 d. Pigs gained 336 +/- 9 g/d, which resulted in an ending BW of 7,228 +/- 120 g, regardless of dietary treatment (P > 0.15). Pigs fed the LF diet consumed 17% more DM per pen daily than pigs fed the HF diet (2,777 +/- 67 vs. 2,376 +/- 67 g/d, P < 0.01), but calculated ME intake did not differ between dietary treatments (P > 0.20). The G:F was 24% greater in HF- than in LF-fed pigs (P < 0.01). Plasma urea N concentrations were higher in the HF-fed pigs (11.0 +/- 0.6 mg/dL) than in pigs fed the LF diet (6.2 +/- 0.6 mg/dL; P < 0.05). Treatment with pST increased circulating IGF-I (P < 0.01) and decreased PUN (P < 0.01) concentration 32 and 25%, respectively, regardless of dietary treatment (P > 0.30). Circulating leptin averaged 1.8 +/- 0.1 ng/mL and was not affected by dietary treatment (P > 0.35) or pST (P > 0.40). These results suggest that the ST/IGF axis is responsive in the young pig and the increase in circulating IGF-I and growth is independent of the source of dietary energy. Also, young pigs respond to a lower energy density liquid diet with increased feed intake, without altering growth performance, apparently utilizing a mechanism other than circulating leptin.

Effects of emulsification, fat encapsulation, and pelleting on weanling pig performance and nutrient digestibility.

Two experiments were conducted to evaluate the effect of lysolecithin on performance and nutrient digestibility of nursery pigs and to determine the effects of fat encapsulation by spray drying in diets fed in either meal or pelleted form. In Exp. 1, 108 pigs (21 d of age; 5.96 +/- 0.16 kg BW) were allotted to one of four dietary treatments (as-fed basis): 1) control with no added lard, 2) control with 5% added lard, 3) treatment 2 with 0.02% lysolecithin, and 4) treatment 2 with 0.1% lysolecithin in a 35-d experiment. Added lard decreased ADG (P = 0.02) and ADFI (P < 0.06) during d 15 to 35 and overall. Lysolecithin improved ADG linearly (P = 0.04) during d 15 to 35 and overall, but did not affect ADFI or G:F. Addition of lard decreased the digestibility of DM (P = 0.10) and CP (P = 0.05) and increased (P = 0.001) fat digestibility when measured on d 10. Lysolecithin at 0.02%, but not 0.10%, tended to improve the digestibility of fat (P = 0.10). On d 28, digestibilities of DM, fat, CP, P, (P = 0.001), and GE (P = 0.03) were increased with the addition of lard, and lysolecithin supplementation linearly decreased digestibilities of DM (P = 0.003), GE (P = 0.007), CP, and P (P = 0.001). In Exp. 2, 144 pigs (21 d of age, 6.04 +/- 0.16 kg BW) were allotted to one of six treatments in a 3 x 2 factorial randomized complete block design. Factors included 1) level (as-fed basis) and source of fat (control diet with 1% lard; control diet with 5% additional lard; and control diet with 5% additional lard from encapsulated, spray-dried fat) and 2) diet form (pelleted or meal). Addition of lard decreased feed intake during d 0 to 14 (P = 0.04), d 15 to 35 (P = 0.01), and overall (P = 0.008), and improved G:F for d 15 to 35 (P = 0.04) and overall (P = 0.07). Encapsulated, spray-dried lard increased ADG (P = 0.004) and G:F (P = 0.003) during d 15 to 28 compared with the equivalent amount of fat as unprocessed lard. Pelleting increased ADG (P = 0.006) during d 0 to 14, decreased feed intake during d 15 to 35 (P = 0.01), and overall (P = 0.07), and increased G:F during all periods (P < 0.02). Fat digestibility was increased (P = 0.001) with supplementation of lard, and this effect was greater when diets were fed in meal form (interaction, P = 0.004). Pelleting increased the digestibility of DM, OM, and fat (P < 0.002). Results indicate that growth performance may be improved by lysolecithin supplementation to diets with added lard and by encapsulation of lard through spray drying.

Liquid egg as an alternative protein source in calf milk replacers.

The use of alternative proteins in milk replacer has been evaluated for their ability to decrease the cost of milk replacers without negatively impacting performance of the calf. Three studies were conducted to evaluate the performance of calves fed milk replacer utilizing liquid egg as an alternative protein and to determine the optimal concentration of liquid egg to include in milk replacers. Calves in trials 1 and 2 were assigned to a control diet of all milk protein replacer (MILK) or a diet formulated to contain 5% of the diet (13.5% of the protein) from liquid egg (5% EGG). Calves in trial 3 were assigned to one of four diets: the control (MILK) and 5% EGG diets fed in trials 1 and 2, or diets formulated to contain either 10 or 15% of the diet (27 or 40.5% of the protein) from liquid egg (10% EGG, 15% EGG). For all experiments, milk replacers were formulated to contain 20% protein, 20% fat and were fed at 454 g/d reconstituted to 12% DM. Production of the diets containing egg protein utilized breaker eggs that were pasteurized during manufacturing. Holstein bull calves (n = 44 for experiment 1, n = 38 for experiment 2, and n = 120 for experiment 3), were purchased from an area sale barn. Calves were housed in individual hutches with water available free choice starting on d 0. A commercially available calf starter was offered free choice beginning on d 7 for experiments 1 and 2 and on d 1 for experiment 3. Feed intake, scour scores, and antibiotic treatments were recorded daily. For experiment 1, calves fed 5% EGG had greater weight gains than calves fed MILK. No differences in average daily feed intake were observed. For experiment 2, weight gains tended to be lower with 5% EGG, whereas feed intakes and gain to feed ratios were similar between calves fed MILK or 5% EGG. For experiment 3, as the amount of egg in the diet increased, weight gain decreased in a linear fashion during the milk replacer feeding period, but the decrease in gain was significant only with the 15% EGG diet. These results indicate that egg is an effective alternative protein source to milk protein in calf milk replacers when fed at levels up to 10% of the diet in a conventional feeding program of 0.45 kg per head per day.

Effect of spray-dried plasma and lipopolysaccharide exposure on weaned pigs: II. Effects on the hypothalamic-pituitary-adrenal axis of weaned pigs.

A study was conducted with 20 weaned barrows (14 d, 4.98 +/- 0.21 kg) to determine the effect of feeding spray-dried plasma (SDP) after weaning on the pig's stress response to a lipopolysaccharide (LPS) challenge. After weaning, pigs were fed a diet containing 0 or 7% SDP for 7 d. On d 6 after weaning, all pigs were nonsurgically fitted with a jugular catheter. On d 7 after weaning, the pigs were given i.p. injections of either saline or LPS (150 microg/kg BW) followed by serial blood collection every 15 min for a 3-h period. Following the 3-h blood collection, all pigs were killed and tissue was collected for mRNA analysis. Pig weight on d 7 after weaning was not affected by dietary treatment (P > 0.21). Pigs fed the diet with SDP had lower (P < 0.05) levels of hypothalamic corticotropin-releasing hormone (CRH) mRNA, pituitary gland CRH receptor mRNA, and adrenal gland adrenocorticotropin-releasing hormone (ACTH) receptor mRNA. Dietary treatment did not affect pituitary gland proopiomelanocortin (POMC) mRNA. No effect of LPS treatment was observed in any of the mRNA levels examined. For both serum ACTH and cortisol, there was a significant diet x LPS treatment interaction (P < 0.01) such that both the ACTH and cortisol responses to the LPS challenge were greater in the pigs fed the diet with SDP than in the pigs fed the diet without SDP. For pigs given the saline injection, diet did not affect basal serum cortisol concentration; however, basal serum ACTH concentration was lower in those pigs fed the diet with SDP (P < 0.0001). A diet x LPS treatment interaction (P < 0.024) was observed for adrenal gland mRNA expression for steroidogenic acute regulatory (StAR) protein such that the LPS-induced increase in StAR mRNA was greater in the pigs fed SDP than in pigs fed the diet without SDP. These results demonstrate that pigs fed a diet with SDP have an increased activation of the pituitary-adrenal axis following an LPS challenge compared to pigs fed a diet without SDP.

Effect of spray-dried plasma and lipopolysaccharide exposure on weaned pigs: I. Effects on the immune axis of weaned pigs.

A study was conducted with 20 weaned barrows (14 d, 4.98 +/- .21 kg) to determine the effect of spray-dried plasma (SDP) on the pig's immune response to a lipopolysaccharide (LPS) challenge. After weaning, pigs were fed a diet containing 0 or 7% SDP for 7 d. On d 6 postweaning, all pigs were fitted with a jugular catheter. On d 7 postweaning, the pigs were given an i.p. injection of either saline or LPS (150 microg/kg BW) followed by a 3-h blood collection every 15 min. Following blood collection, all pigs were killed and tissue was collected for mRNA analysis. Additionally, the small intestine was collected for measurement of villus height, crypt depth, and villus height:crypt depth ratio (VCR) at three sites (25, 50, and 75% of the total length). Feeding SDP resulted in reduced (P < 0.05) mRNA expression of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) mRNA in the adrenal gland, spleen, hypothalamus, pituitary gland, and liver. Additionally, expression of IL-6 mRNA was reduced (P < 0.05) in the spleen and pituitary gland for pigs fed SDP. For pigs fed the diet with SDP, LPS administration did not affect (P > 0.10) cytokine mRNA expression, whereas LPS reduced expression of TNF-alpha mRNA in the spleen and IL-1beta mRNA in the adrenal gland, spleen, and thymus for pigs fed the diet without SDP. For pigs fed the diet with SDP, LPS caused serum TNF-alpha to increase 150-fold compared to a 60-fold increase for pigs fed the diet without SDP. Similarly, interferon-gamma (IFN-gamma) increased 110-fold for pigs fed the diet with SDP compared to a 16-fold increase for pigs fed the diet without SDP. For pigs fed the diet with SDP, LPS caused major villus atrophy, whereas for pigs fed the diet without SDP, LPS had no effect on intestinal morphology. These results demonstrate that the basal activation of the immune system appears to be less for pigs fed the diet with SDP compared to pigs fed the diet without SDP after weaning. Additionally, for pigs fed the diet with SDP, there appeared to be an overresponse of the immune system following LPS administration, which resulted in major damage to the mucosa of the gastrointestinal tract.

Effects of weaning on somatotrophic gene expression and circulating levels of insulin-like growth factor-1 (IGF-1) and IGF-2 in pigs.

The present study evaluated somatotrophic gene expression in liver, muscle and adipose tissue 4 d after weaning, a time point corresponding to greatly reduced serum concentrations of insulin-like growth factor (IGF)-1 and IGF-2 in pigs. Two-week-old barrows were either cross-fostered to a sow (SOW, n = 8) or weaned and fed a phase 1 diet containing either 0 or 7% spray-dried plasma (NP, n = 8 and SDP, n = 8; respectively). Piglets were allocated such that two size groups were equivalently represented in each experimental group (small, 3.5-4.3 kg and large, 4.6-5.7 kg). Animals were weighed daily and sacrificed 4 d after weaning for blood and tissue collection. Daily gains of the SOW piglets were significantly greater than those of the weaned pigs for the first 3 d of the experiment (P < 0.0001). Weight gains in the SOW and SDP pigs between d 3 and 4 were equivalently elevated relative to the NP pigs (P < 0.0001). Serum IGF-1 and IGF-2 concentrations were decreased in both NP and SDP compared to SOW (P < 0.0001). Serum IGF-2 levels were significantly lower in small piglets (P = 0.006). A Weaning Group X Size interaction was noted for liver IGF-2 mRNA (P < 0.03), reflecting a higher level of expression in large SOW piglets relative to small SOW piglets. Weaning did not affect IGF-1, IGF-2, or growth hormone (GH) receptor mRNA levels in liver, muscle, or fat (P > 0.05). Liver IGF-binding protein (IGFBP)-3 and acid-labile subunit (ALS) mRNA levels also were unaffected by weaning. Small pigs had lower levels of liver ALS (P = 0.0003), muscle IGF-2 (P = 0.02), and muscle GH receptor (P = 0.006) mRNAs. In contrast, adipose tissue IGF-1 and IGF-2 mRNA levels were greatest in the small piglets (P = 0.001 and 0.029, respectively).

Cloning of porcine prepro-orexin cDNA and effects of an intramuscular injection of synthetic porcine orexin-B on feed intake in young pigs.

Early growth is an important determinant of gain and efficiency in growing pigs. A major limiting factor of piglet growth is feed intake. Orexins, newly discovered neuropeptides, may be important regulators of appetite. The orexin gene, which encodes orexin-A and -B, was recently identified in rodents and man. The objectives of this study were to clone the cDNA for porcine orexin, utilize the cDNA sequence information to produce synthetic hormone, and evaluate the effect of orexin administration on feed intake in weanling pigs. Oligonucleotide primers were designed for reverse transcription polymerase chain reaction production of porcine orexin cDNA. The polymerase-chain-reaction products were cloned, sequenced, and found to be 88.5% homologous to the human orexin sequence. Predicted translation of porcine orexin cDNA revealed orexin-A and -B amino acid sequences that were 100% and 96% homologous to the known human peptides, respectively. Porcine orexin-B was synthesized according to the predicted sequence. Twenty-six cross-bred piglets were utilized in three replicates (n = 8-10/replicate). Piglets were weaned between 2-3 wk of age. One week after weaning, equal numbers of animals in each replicate received intramuscular (i.m.) injections of orexin-B (3 mg/kg body weight) or vehicle (sterile water). Feed intake was monitored from -24 to 24 h relative to injection (time 0). The orexin-injected pigs ingested an additional meal at 12 h when compared with the control animals (P = 0.02). Cumulative feed intake was increased by orexin-B administration from 12 to 24 h postinjection (P < or = 0.05). Total feed intake at 24 h was improved by 18% in orexin-treated pigs (P = 0.05). The ability to stimulate appetite during critical periods of early growth, particularly following weaning, could result in significant improvements in swine-production efficiency.

The use of synthetic lysine in the diet of lactating sows.

We conducted an experiment to determine the proportion of the lysine requirement of lactating sows that can be met using L-lysine x HCl. A total of 247 Pig Improvement Company (PIC) sows (parity one to four) were randomly allotted to one of five experimental diets containing .79% apparently digestible lysine. The first four diets contained 0, .075, .150, and .225% L-lysine x HCl replacing the intact lysine, primarily derived from soybean meal. Dietary crude protein was reduced from 17.9 to 16.9, 15.8, and 14.8% respectively. The fifth diet contained .174% L-lysine x HCl (15.5% CP) with added synthetic methionine, threonine, and tryptophan to restore the ratios of these amino acids to lysine to those in the control diet with no synthetic amino acids. The average lactation length was 15.7 +/- .3 d. Diet did not affect ADFI, sow backfat loss, sow loin eye area loss, or weaning-to-mating interval. Sows consumed an average of 4.6 kg/d and were provided 36 g/d of digestible lysine. Replacing soybean meal with increasing levels of L-lysine x HCl did not affect sow weight change. The number of pigs weaned decreased and preweaning mortality increased linearly (P = .08) with increasing levels of L-lysine x HCl. Litters from sows fed the .174% L-lysine x HCl with added methionine, threonine, and tryptophan grew slower and had a higher mortality rate than litters from sows fed no synthetic amino acids (P < .05). The addition of synthetic methionine, threonine, and tryptophan to the .174% L-lysine x HCl diet did not improve litter growth rate, but it did increase preweaning mortality (P = .05) and decrease the number of pigs weaned (P = .06) compared to the .15% L-lysine x HCl with no additional synthetic amino acids. These additions also resulted in an increased sow weight loss (P = .10). These results suggest that when more than .075% L-lysine x HCl is used to meet the lysine requirement preweaning mortality is increased and the number of pigs weaned is decreased. Supplementation with methionine, threonine, and tryptophan failed to ameliorate the negative response associated with L-lysine x HCl, which suggests that other amino acids may be limiting.

The lysine requirement of lactating primiparous sows.

We conducted an experiment with 289 primiparous sows to evaluate the effect of lysine intake on lactation and subsequent reproductive performance. Sows were randomly allotted to one of five experimental corn-soybean meal lactation diets. The first four diets contained incremental levels of apparently digestible lysine (.67, .86, 1.06, and 1.25%) and provided digestible lysine intakes of 27, 34, 41, and 48 g/d. All lysine was derived from intact protein sources. Synthetic valine, threonine, and methionine were used to maintain ratios to lysine that were equal to those of the .67% lysine diet. The fifth diet contained 1.06% digestible lysine and provided 43 g/d digestible lysine, but no additional synthetic amino acids were added. The average lactation length in this study was 16.9 +/- .2 d. Lysine intake during lactation did not affect number of pigs weaned, litter growth rate, sow backfat loss, or weaning to mating interval. Sow weight loss and loin eye area loss decreased quadratically (P < .05) with increasing lysine intake. These were minimized at 45 and 48 g/d digestible lysine, respectively. Removing synthetic amino acids from the 1.06% digestible lysine diet resulted in an increased litter growth rate (1.98 vs 2.15 kg/d, P < .05). Increasing dietary lysine intake while maintaining amino acid ratios to lysine for valine, threonine, and total sulfur amino acids during the first lactation resulted in a linear (P < .05) decrease in second litter total born. However, removal of synthetic amino acids from the 1.06% digestible lysine diet resulted in an increased second litter total born (12.9 vs 11.2, P < .05), which tended to be higher compared with the .67% digestible lysine treatment (12.9 vs 11.7, P = .13). The results suggest that primiparous sows are able to mobilize sufficient body reserves to maintain a high level of milk production at low levels of lysine intake during a 17-d lactation. Higher levels (45 to 48 g/d) of digestible lysine are required to minimize body protein loss. The source or composition of amino acids in the lactation diet may have an effect on second litter size.