Two groups of 240 pigs (PIC 337 X 1050, PIC Genus, Hendersonville, TN) with initial body weight (BW) 13.20 ± 3.05 kg were used to investigate interactions between the branched-chain amino acids (BCAA). At weaning, pigs were placed into 40 pens with three barrows and three gilts per pen and fed a common diet for three weeks. On day 21 post-weaning, pens were randomly assigned to one of 15 dietary treatments arranged in a rotatable central composite design. Experimental diets were formulated to various levels of standardized ileal digestible (SID) leucine, isoleucine, and valine by replacing corn starch and glycine with L-leucine, L-isoleucine, and L-valine in the base diet. Levels of BCAA were expressed as ratios to SID lysine and ranged from 98 to 180 for Leu, 46 to 64 for Ile, and 51 to 78 for Val. Diets were formulated to be sub-limiting in lysine at 1.19% SID Lys and exceed all other essential amino acid requirements. Additionally, diets were formulated to be isocaloric and isonitrogenous and met or exceeded NRC (2012) vitamin and mineral requirements. Pen weights and feed intake were measured for the 21-day experiment to calculate daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (G:F). Data were fit as a second-order response surface model according to the central composite design in R version 4.2.1 (R Core Team, 2022). The model included linear and quadratic effects of Leu, Ile, and Val, and their cross-products. Pen was the experimental unit, and parameters were considered significant at P ≤ 0.10. Valine linearly and quadratically impacted ADG and G:F, regardless of Leu and Ile levels. There was an interaction between Leu and Ile for ADG (P = 0.079) and G:F (P = 0.031), where, at increasing levels of Leu, decreasing Ile improved ADG and G:F. Conversely, ADG and G:F decreased as both Leu and Ile increased. Isoleucine did not impact ADFI (P ≥ 0.458); however, there was an interaction between Leu and Val (P = 0.088), where Leu negatively impacted ADFI at low levels of Val, but did not influence ADFI at higher levels of Val.
Article Quarter: FY23 Q3
Concentrations of digestible and metabolizable energy, ileal digestibility of amino acids, and digestibility of phosphorus in a new variety of soybeans fed to growing pigs
The objective was to test the hypothesis that digestible energy (DE), metabolizable energy (ME), standardized ileal digestibility (SID) of amino acids (AA), and standardized total tract digestibility (STTD) of P in soybean meal produced from a new variety of soybeans (Photoseed) are not different from conventional soybean meal (SBM-CV). In Exp. 1, thirty pigs (18.3 ± 1.3 kg) were randomly allotted to a corn diet or 2 diets containing corn and Photoseed or corn and SBM-CV. Pigs were housed in metabolism crates and feces and urine were collected for 4 d after 5 d of adaptation. Feces and urine were analyzed for gross energy and DE and ME were calculated for each ingredient. The statistical model included ingredient as fixed effect and replicate as random effect and pig was the experimental unit. Results indicated that DE and ME of Photoseed were not different from DE and ME in SBM-CV (Table 1). In Exp. 2, nine barrows (30.0 ± 1.5 kg) with a T-cannula in the distal ileum were allotted to a triplicated 3 × 3 Latin Square design with 3 diets and 3 periods in each square. An N-free diet and diets containing SBM-CV or Photoseed were used. Pigs were housed individually in fully slatted pens and ileal digesta were collected on d 6 and 7 of each period. Digesta samples were lyophilized, ground, and analyzed for AA, and SID of AA was calculated. The statistical model included diet as fixed effect and square, period, and pig as random effects, and pig was the experimental unit. Results indicated that the SID of Arg, Ile, and Lys were not different between the two ingredients (Table 2), but the SID of other indispensable AA were greater (P < 0.05) in SBM-CV than in Photoseed. In Exp. 3, forty-eight barrows (12.0 ± 1.6 kg) were allotted to 6 diets with 8 pigs per diet. The SBM-CV or Photoseed were included in diets with 3 levels of microbial phytase (0, 500, or 1,000 units/kg). Pigs were housed in metabolism crates and feces were collected quantitatively for 4 d after 5 d of adaptation. Fecal samples were dried and analyzed for P and the STTD of P was calculated. The statistical model included ingredient, phytase, and the interaction between ingredient and phytase as fixed effects and replicate as the random effect. The pig was the experimental unit. Results indicated that inclusion of phytase in the diets increased (P < 0.05) the STTD of P, but STTD of P in Photoseed was not different from the STTD in SBM-CV (Table 3).
Effect of soybean meal inclusion on grow-finish pig performance and nitrogen balance
Two hundred and forty mixed-sex pigs (PIC 337×1050; 23 ± 4.7 kg) were utilized to evaluate the effects of soybean meal (SBM) inclusion on the growth performance and nitrogen balance of grow-finish pigs. Pigs were assigned across 60 split-sex pens, and pens were randomly assigned to one of three dietary treatments (10 pens/trt/sex). Diets were formulated with increasing SBM for an approximate 3% incremental difference in crude protein (CP) between treatments. The treatments were: 1) low SBM (L-SBM) corn-soy diet supplemented with synthetic amino acids, 2) medium SBM diet (M-SBM) with SBM formulated to replace all synthetic lysine and equal to L-SBM in SID lysine, and 3) high SBM diet (H-SBM) contained excess levels of all amino acids. Diets were fed in four feeding phases ranging from approximately 25–50, 51–75, 76–105, and 106–135 kg for phases 1–4, respectively. From phases 1 to 4, SBM inclusion ranged from approximately 26–48% (SID Lys 1.06–1.32%), 19–41% (SID Lys 0.89–1.15%), 15–35% (SID Lys 0.76–1.01%), and 13–29% (SID Lys 0.68–0.86%), respectively. Additionally, diets within each phase were isocaloric. Pig BW and feed intake were measured for each phase to calculate ADG, ADFI, and G:F. On day 66, 18 gilts (n=6/trt) were placed into metabolism stalls for total urine and feces collection over a 72h period to assess CP digestibility and nitrogen balance. Pigs were marketed at approximately 134 kg BW, and carcass weight, backfat depth, and loin depth were measured at the harvest facility. Data were subject to ANOVA in SAS 9.4. Pen was the experimental unit, and the results were significant at P ≤ 0.05. Overall (d0–98) pig ADFI, ADG, or G:F did not differ across treatments (P ≥ 0.202). However, there was a significant diet-by-phase interaction for ADG (P=0.045) and G:F (P=0.008), where H-SBM fed pigs grew faster in phase two compared to the M-SBM (1.07 vs. 1.02 kg/d; P=0.026) or L-SBM (1.07 vs. 1.02 kg/d; P=0.028) fed pigs. Consequently, in phase two, H-SBM pigs had improved G:F compared to M-SBM (0.47 vs. 0.44; P=0.005) or L-SBM pigs (0.47 vs. 0.44; P=0.001). However, these effects were not evident in the other phases. Apparent total tract digestibility of CP and nitrogen retention were similar between treatments (P ≥ 0.762). However, as expected, nitrogen retention as a proportion of intake, linearly decreased (P < 0.001) as SBM inclusion increased, which translated to an approximate 130% increase in total nitrogen excretion in pigs fed H-SBM compared to L-SBM (40.8 vs. 17.7 g/d; P < 0.001).
Evaluation of diet composition on early post-weaned feed intake and intestinal health
Weaning is an inevitable early life stressor in commercial production that can cause an immediate reduction in voluntary feed intake and growth during a critical period of gastrointestinal development. Further, the reduction in voluntary feed intake is strongly correlated with the risk of disease during that period. Therefore, our objective was to test the effect of different dietary interventions on early nursery pig feed intake, performance, fecal consistency, and histological parameters. Over 2 repetitions, a total of 90 newly weaned gilts (19-21 d of age, BW 5.62 ± 1.1 kg) were selected, individually penned and randomly assigned to 1 of 5 dietary treatments (n = 18 pigs/trt) that included: 1) Control diet (CON), 2) CON + 5% sugar beet pulp (BP), 3) CON + 10% high fructose corn syrup (HFCS), 4) CON + 5% soyhulls (SH), or 5) CON + 3,000 ppm Zn and 200 ppm Cu (d 0-7), and 2,000 ppm Zn and 200 ppm Cu (d 8-14; ZC). Each repetition was conducted over a 14-d period consisting of 2 phases (phase 1: d 0-7, phase 2: d 8-14). Pigs were all sourced from a natural endemic enteric pathogen positive nursery flow and confirmed positive for rotavirus, coccidia and F18 E. coli. Fecal consistency was scored and feed disappearance was recorded daily. On d 0, 7 and 14, pig BWs were collected. Weekly feed disappearance and BWs were used to calculate ADG, ADFI and feed efficiency (G:F) within phase and overall. On d 14, all pigs were euthanized, and fixed sections of ileum and colon were collected to assess histopathology including incidence of villus atrophy and colitis. Pig was the experimental unit, and performance and histology data were analyzed by dietary treatment. Daily measures of feed intake were analyzed by repeated measures with the fixed effects of diet, day, and their interaction. Starting body weight did not differ across dietary treatments (P = 0.845). Over the 14-d test period, HFCS and ZC treatments tended to increase ADG (0.20 and 0.15 kg/d, respectively) compared to CON, BP and SH (0.09, 0.12, and 0.13 kg/d, respectively; P = 0.076). Further, the addition of a sweetener (HFCS) did not improve daily feed intake, while SH reduced daily feed intakes by 32% compared to all other treatments (P < 0.001). Although all pigs had some degree of diarrhea, fecal consistency did not differ between dietary treatments (P= 0.618). Histopathology scoring for intestinal atrophy (ileum) and colitis (colon) were not different (P = 0.645 and 0.440, respectively).
Formulating U.S. swine diets in a time of high energy costs
The cost of dietary energy has greatly increased in the last few years and this trend of historically higher prices is expected to remain in the future. This has led to shifts in diet formulation and a need to reevaluate pig responses to changing dietary energy density. As part of the evaluation, nutritionists should review whether energy loadings for their ingredients are accurate. Is the relative change in dietary energy reflected accurately by changes in feed efficiency? If there is not a 1:1 relationship between dietary energy and feed efficiency, dietary energy is not being accurately represented. Because of the linear relationship between diet energy and feed efficiency, that portion of the economic equation is easy to measure. However, the impact of dietary energy on growth performance is more difficult to predict. Does daily gain increase linearly over the entire range of possible energy levels or, if not, when does it plateau? This relationship must be known or estimated to determine the value of changes in energy density. Furthermore, if alternative ingredients with high fiber content are used, at what point does fiber content prevent pigs from increasing feed intake to maintain energy intake? Another key practical concept with energy is how fast the pig adjusts feed intake to changes in diet energy density. Over the long term, pigs adjust their level of consumption to the energy density of the diet; however, it takes time for pigs to make this adjustment. Thus, in the short term, pigs consume the same amount of total feed resulting in increased energy intake and gain if dietary energy is increased or reduced energy intake if diet energy is reduced. When changing dietary energy, the lysine:calorie ratio and phosphorus:calorie ratio should be adjusted to maintain proper amino acid and phosphorus intake to support optimum growth. The high cost of energy has increased the search for other methods to increase pig performance. The ratios of several key amino acids to Lys should be reviewed to take advantage of their impact on feed intake (ex. Trp, Val, etc). From a practical standpoint, the rise in energy costs has led to the removal of added fat from most pig diets unless essential to maintain pellet quality. Alternative ingredients are being used wherever economical.
The global energy situation: Outlook for energy availability for fuel and feed
The cost of dietary energy has greatly increased in the last few years and this trend of historically higher prices is expected to remain in the future. This has led to shifts in diet formulation and a need to reevaluate pig responses to changing dietary energy density. As part of the evaluation, nutritionists should review whether energy loadings for their ingredients are accurate. Is the relative change in dietary energy reflected accurately by changes in feed efficiency? If there is not a 1:1 relationship between dietary energy and feed efficiency, dietary energy is not being accurately represented. Because of the linear relationship between diet energy and feed efficiency, that portion of the economic equation is easy to measure. However, the impact of dietary energy on growth performance is more difficult to predict. Does daily gain increase linearly over the entire range of possible energy levels or, if not, when does it plateau? This relationship must be known or estimated to determine the value of changes in energy density. Furthermore, if alternative ingredients with high fiber content are used, at what point does fiber content prevent pigs from increasing feed intake to maintain energy intake? Another key practical concept with energy is how fast the pig adjusts feed intake to changes in diet energy density. Over the long term, pigs adjust their level of consumption to the energy density of the diet; however, it takes time for pigs to make this adjustment. Thus, in the short term, pigs consume the same amount of total feed resulting in increased energy intake and gain if dietary energy is increased or reduced energy intake if diet energy is reduced. When changing dietary energy, the lysine:calorie ratio and phosphorus:calorie ratio should be adjusted to maintain proper amino acid and phosphorus intake to support optimum growth. The high cost of energy has increased the search for other methods to increase pig performance. The ratios of several key amino acids to Lys should be reviewed to take advantage of their impact on feed intake (ex. Trp, Val, etc). From a practical standpoint, the rise in energy costs has led to the removal of added fat from most pig diets unless essential to maintain pellet quality. Alternative ingredients are being used wherever economical.
