Effects of Increasing Levels of Copper from Either CuSO 4 or Combinations of CuSO 4 and a Cu-Amino Acid Complex on Growth Performance , Carcass Characteristics , and Economics of Finishing Pigs

A total of 1,089 pigs (PIC 280 ×1050; initially 82.2 lb) were used in a 105-d experiment to determine the effects of increasing added Cu from either CuSO4 alone or a 50/50 blend of CuSO4 and Cu-AA (Availa®-Cu, Zinpro Corporation, Eden Prairie, MN) on growth performance, carcass characteristics, and economics of finishing pigs. All 6 dietary treatments contained 17 ppm Cu from CuSO4 from the trace mineral premix. Additional treatment diets contained added CuSO4 to provide 70 and 130 ppm total Cu or a 50/50 blend of added Cu from CuSO4 and Cu-AA to provide 70, 100, and 130 ppm total Cu. There were 25 or 26 pigs per pen and 7 replicate pens per treatment. Overall, added Cu above 17 ppm did not influence ADG; however, pigs fed 70 and 130 ppm added Cu from the 50/50 blend of CuSO4 and Cu-AA had decreased (P = 0.045) ADFI and improved feed efficiency (P = 0.048) compared with those fed 70 and 130 ppm of added Cu from CuSO4 only. Similar to the F/G response, pigs fed diets that contained CuSO4 alone had poorer (P = 0.030) carcass F/G than those fed added Cu from the 50/50 blend of CuSO4 and Cu-AA. Neither Cu source nor level influenced economics. In conclusion, these data suggest pigs fed diets that contained added Cu from CuSO4 alone consume more feed but have poorer feed efficiency which translates into poorer carcass F/G compared to those fed a 50/50 blend of CuSO4 and Cu-AA. Copper level did not impact growth performance. Based on our study, it appears that the 50/50 blend of CuSO4/Cu-AA optimized feed efficiency and carcass feed efficiency of pigs marketed on a constant time basis.

Overall, added Cu above 17 ppm did not influence ADG; however, pigs fed 70 and 130 ppm added Cu from the 50/50 blend of CuSO 4 and Cu-AA had decreased (P = 0.045) ADFI and improved feed efficiency (P = 0.048) compared with those fed 70 and 130 ppm of added Cu from CuSO 4 only. Similar to the F/G response, pigs fed diets that contained CuSO 4 alone had poorer (P = 0.030) carcass F/G than those fed added Cu from the 50/50 blend of CuSO 4 and Cu-AA. Neither Cu source nor level influenced economics.
In conclusion, these data suggest pigs fed diets that contained added Cu from CuSO 4 alone consume more feed but have poorer feed efficiency which translates into poorer carcass F/G compared to those fed a 50/50 blend of CuSO 4 and Cu-AA. Copper level did not impact growth performance. Based on our study, it appears that the 50/50 Introduction Feeding high concentrations of Cu from CuSO 4 has been associated with improved growth performance of growing pigs. However, the responses observed in different trials are variable and may depend on feeding period or concentration. Coble et al. (2015) 4 reported ADG tended to increase when pigs were fed added Cu from tri-basic copper chloride during the early finishing period. However, Feldpausch et al. (2015) 5 reported no growth promoting benefit of 150 ppm added Cu from CuSO 4 during either the early or late finishing periods. Further investigation is warranted to better understand how high levels of Cu will impact growing and finishing pig performance. Furthermore, it is not well understood if the specific source of Cu will lead to differences in pig performance. Therefore, the objective of this study was to determine the effects of increasing Cu provided from either CuSO 4 alone or a 50/50 blend of CuSO 4 and Cu-AA on growth performance, carcass characteristics, and economics of finishing pigs housed in a commercial environment.

Procedures
The Kansas State University Institutional Animal Care and Use Committee approved the protocol used in this experiment. The experiment was conducted in a commercial research facility in southwestern Minnesota. The facility was double-curtain-sided with completely slatted concrete flooring. The barn contained 42 pens with 25 or 26 pigs (mixed gender) in each, equipped with a 4-hole conventional dry self-feeder (Thorp Equipment, Thorp, WI) and 1 cup-waterer, providing ad libitum access to feed and water. A computerized feeding system (FeedPro; Feedlogic Corp., Willmar, MN) delivered and recorded daily feed additions of each diet to the respective pen. Pigs were weighed and feed disappearance was measured approximately every 2 weeks to calculate ADG, ADFI, and F/G. On d 79 of the trial, pens were weighed and the 3 heaviest pigs from each pen were removed and transported 59 miles to JBS USA (Worthington, MN) for harvest. These pigs were used in calculation of pen growth performance, but not carcass characteristics.
On d 105, final pen weights were recorded and feed disappearance was measured. The remaining pigs in the barn were individually tattooed with a pen identification number to allow individual carcass measurements to be recorded, and transported to the same aforementioned harvest facility for carcass data collection. Carcass yield was calculated using HCW at the plant divided by average individual live weight at the farm. Standard carcass measurements of backfat (BF), loin depth (LD), and percentage lean (Lean, %) were measured, with pen as experimental unit and carcass as the observational unit. Fat depth and loin depth were measured with an optical probe [Fat-O-Meter (SFK, Herlev, Denmark)] inserted between the third and fourth last rib (counting from the ham end of the carcass) at a distance approximately 2.76 in. from the dorsal midline.
Economic comparisons were made based on both a constant ending weight and a constant day basis. Total feed cost per pig, cost per pound of gain, carcass ADG, F/G, carcass gain value, and income over feed cost (IOFC) were calculated. An assumed carcass yield of 75% was used to calculate initial HCW at the beginning of the experiment. Hot carcass weight ADG was calculated by subtracting initial HCW from the final HCW obtained at the plant, then divided by 105 d on test. Hot carcass weight F/G was calculated by dividing the pen total feed intake by pen total carcass weight gain. Feed cost was calculated by multiplying total feed intake per pig by a weighted mean diet cost on a per pen basis. Prices used for corn, soybean-meal, and DDGS at the time of the experiment were $0.06, 0.14, and 0.05/lb, respectively. Prices used for the Cu-AA and CuSO 4 were $2.14 and $1.00/lb, respectively. Carcass price at time of slaughter was calculated at $0.74 per pound. Cost per pound of gain was calculated by dividing the total feed cost per pig by the total carcass pounds gained overall. The value of the carcass weight gained during the experiment (gain value) was calculated by multiplying the carcass value by the pen final carcass weight. Income over feed cost was calculated by subtracting total feed cost from gain value. The income over feed and facilities cost Swine Day 2016 (IOFFC) was calculated for the constant market weight evaluation because pigs with faster growth rates will reach a 210 lb carcass sooner, therefore decreasing housing costs. Facility cost was calculated by multiplying the number of overall days the pigs need to reach a 210 lb carcass based on their respective growth rate by $0.11 per head per day facility cost.
Data were analyzed as a randomized complete block design using PROC GLIMMIX (SAS Institute, Inc., Cary, NC) with pen as the experimental unit. Hot carcass weight was used as a covariate for carcass characteristics including percentage lean, loin depth, and backfat. Effects of Cu source and linear and quadratic effects of Cu level were analyzed with significance defined as P ≤ 0.05 and marginally significant as P > 0.05 and ≤ 0.10.

Results and Discussion
The chemical analyses of the complete diets were similar to the intended formulation (Tables 1, 2 Of the 30 experimental diets, 6 diets were outside the analytical variation limits for Cu (25%, AAFCO, 2014) 7 . In Phase 1, the diet formulated to contain 70 ppm Cu from CuSO 4 was slightly lower and the diet formulated to contain 130 ppm Cu from the 50/50 blend was lower in analyzed Cu concentration than expected. In Phase 2, the control diet was slightly higher in analyzed Cu than expected. In Phase 3, the control diet and the diet formulated to contain 70 ppm Cu from the 50/50 blend were higher in analyzed Cu than expected and the diet formulated to contain 130 ppm Cu from CuSO 4 alone was much lower in analyzed Cu than expected.
All other total Cu values for each diet were within the acceptable analytical limits described by the AAFCO (2014) given that 17 ppm of Cu from CuSO 4 was provided by the trace mineral premix and accounting for the Cu provided by ingredients used in formulation. Corn, soybean meal, and corn DDGS can contain on average 15, 50, and 52 ppm Cu, respectively (NRC, 2012). Based on these Cu concentrations, corn, soybean meal and corn DDGS may have contributed up to 14 ppm Cu to the complete diet in our study. Thus, some of the variation observed in the Cu analysis may partially be explained by the Cu concentrations provided by major ingredients used in formulation.
From d 0 to 43, neither Cu source nor level influenced growth performance (Table 5).
From d 43 to 105, ADFI was lower (P = 0.037) for pigs fed the 50/50 blend of added Cu from CuSO 4 and Cu-AA compared to those fed added Cu from CuSO 4 alone. Feed efficiency tended to be improved (linear, P = 0.057) as level of Cu increased.

Swine Day 2016
Overall, d 0 to 105, neither Cu level nor source influenced ADG. Pigs fed 70 and 130 ppm added Cu from the 50/50 blend of CuSO 4 and Cu-AA had lower (P = 0.045) ADFI and improved feed efficiency (P = 0.048) compared with those fed the same amount of added Cu from only CuSO 4 . Due to the decreased ADFI and improved F/G of pigs fed the 50/50 blend of added Cu from CuSO 4 and Cu-AA, carcass F/G also improved (P = 0.030; Table 6) compared with those fed added Cu from CuSO 4 alone.
Regarding economics, neither Cu source nor level influenced economics when reported on a constant time or constant weight basis (Table 7).
Although there are limited data available describing the effects of Cu blends, a variety of experiments have demonstrated conflicting results on the growth-promoting benefits of added Cu above that provided by the trace mineral premix. Hastad et al. In summary, our study suggests differences exist between feeding added Cu as either a blend or single source on growth performance, carcass characteristics or economics. These data suggest pigs fed diets that contain added Cu from CuSO 4 had greater ADFI but are less efficient. Furthermore, carcass F/G worsened when diets contained CuSO 4 compared to those fed a 50/50 blend of CuSO 4 and Cu-AA, which is likely explained by the poorer F/G of pigs fed CuSO 4 alone. Our data suggest a 50/50 blend of CuSO 4 and Cu-AA has the potential to improve F/G as a result of reduced feed intake but no difference in overall gain or ending BW. Based on our study, it appears a 50/50 blend of CuSO 4 and Cu-AA optimizes feed efficiency and carcass feed efficiency for pigs marketed on a constant time basis.        Corn, soybean-meal and DDGS were calculated at 0.06, 0.17 and 0.05 $/lb, respectively. Test ingredients used were Cu-AA (Availa® Cu) and CuSO 4 and calculated at 2.14 and 1.00 $/lb, respectively. 7 Carcass gain value calculated using (total carcass gain × carcass price). 8 Income over feed cost = carcass gain value -feed cost. 9 Adjusted to constant final carcass weight of 210 lb. 10 Facility cost at 0.11 $/hd/day.

11
Income over feed and facility cost = IOFC -facility cost.