Master of Science / Department of Animal Sciences and Industry / John M. Gonzalez / Pigs fed ractopamine-HCl (RAC) are more prone to fatigue and exhaustion when improperly handled. Wireless electromyography (EMG) can be used to directly measure median power frequency (MdPF) and root mean square (RMS) as indicators of action potential conduction velocity and muscle fiber recruitment, respectively. The objectives of this study were to determine the effect of RAC on exhaustion, EMG measures, and muscle fiber type characteristics when barrows were subjected to increased levels of activity. Thirty-four barrows were assigned to one of two treatments: a commercial finishing diet containing 0 mg/kg (CON) RAC or a diet formulated to meet the requirements of finishing barrows fed 10 mg/kg RAC (RAC+) for 35 d. After 32 d of feeding, barrows were walked around a circular track at 0.79 m/s until subjective exhausted was reached. Time, distance, and speed were measured. Wireless surface EMG sensors were affixed to the Deltoideus (DT), Triceps brachii lateral head (TLH), Tensor fasciae latae (TFL), and Semitendinosus (ST) muscles. After harvest, samples of each muscle were collected for fiber type, succinate dehydrogenase, and capillary density analysis. Speed was not different (P = 0.82) between treatments, but RAC+ barrows reached subjective exhaustion quicker and covered less distance than CON barrows (P < 0.01). The end-point MdPF was not affected by the RAC diet. The RAC diet did not change end-point RMS values in the DT or TLH; however, the RAC+ barrows tended to have decreased ST and increased TFL end-point RMS values (P < 0.07). The percentage of type I fibers tended to be greater (P = 0.07) in RAC+ barrows, but the RAC diet tended to increase (P = 0.07) size of type I fibers and increase (P = 0.03) the size of type IIA fibers. Succinate dehydrogenase was not different between treatments. The RAC+ barrows had more (P = 0.03) capillaries per fiber than CON barrows. A diet containing RAC contributes to increased onset of subjective exhaustion, possibly due to rapid loss of active muscle fibers and chronic loss of oxidative muscle fibers with no change in muscle metabolism.

Master of Science / Animal Sciences and Industry / John M. Gonzalez / Pigs fed ractopamine-HCl (RAC) are more prone to fatigue and exhaustion when improperly handled. Wireless electromyography (EMG) can be used to directly measure median power frequency (MdPF) and root mean square (RMS) as indicators of action potential conduction velocity and muscle fiber recruitment, respectively. The objectives of this study were to determine the effect of RAC on exhaustion, EMG measures, and muscle fiber type characteristics when barrows were subjected to increased levels of activity. Thirty-four barrows were assigned to one of two treatments: a commercial finishing diet containing 0 mg/kg (CON) RAC or a diet formulated to meet the requirements of finishing barrows fed 10 mg/kg RAC (RAC+) for 35 d. After 32 d of feeding, barrows were walked around a circular track at 0.79 m/s until subjective exhausted was reached. Time, distance, and speed were measured. Wireless surface EMG sensors were affixed to the Deltoideus (DT), Triceps brachii lateral head (TLH), Tensor fasciae latae (TFL), and Semitendinosus (ST) muscles. After harvest, samples of each muscle were collected for fiber type, succinate dehydrogenase, and capillary density analysis. Speed was not different (P = 0.82) between treatments, but RAC+ barrows reached subjective exhaustion quicker and covered less distance than CON barrows (P < 0.01). The end-point MdPF was not affected by the RAC diet. The RAC diet did not change end-point RMS values in the DT or TLH; however, the RAC+ barrows tended to have decreased ST and increased TFL end-point RMS values (P < 0.07). The percentage of type I fibers tended to be greater (P = 0.07) in RAC+ barrows, but the RAC diet tended to increase (P = 0.07) size of type I fibers and increase (P = 0.03) the size of type IIA fibers. Succinate dehydrogenase was not different between treatments. The RAC+ barrows had more (P = 0.03) capillaries per fiber than CON barrows. A diet containing RAC contributes to increased onset of subjective exhaustion, possibly due to rapid loss of active muscle fibers and chronic loss of oxidative muscle fibers with no change in muscle metabolism.

Doctor of Philosophy / Department of Animal Sciences and Industry / Michael D. Tokach / Four experiments were conducted to determine the interactive effects of dietary L-carnitine and ractopamine HCl (ractopamine) on finishing pig growth performance. In analysis of treatments common to all experiments, ractopamine increased (P < 0.01) ADG and G:F compared to pigs not fed ractopamine. Added L-carnitine tended to increase (P < 0.07) ADG and improved (P < 0.01) G:F compared to pigs not fed L-carnitine. Three experiments were conducted to determine the effects of L-carnitine and ractopamine on carcass characteristics and meat quality. In Exp. 1, drip loss decreased (linear, P < 0.04) in pigs fed increasing L-carnitine. In Exp. 2, drip loss decreased (P < 0.04) with increasing L-carnitine when fed with ractopamine. Percentage lean was higher (P < 0.01) for pigs fed ractopamine. In Exp. 3, lean percentage increased (P < 0.03) in pigs fed L-carnitine or ractopamine. Pigs fed L-carnitine tended (P < 0.06) to have decreased drip loss. These results suggest that ractopamine increases carcass leanness and L-carnitine reduces drip loss when fed in combination with ractopamine. Two experiments were conducted to determine the effects of L-carnitine and ractopamine on the metabolic response to handling. Non-gentle handling increased (P < 0.01) lactate and rectal temperature, and decreased pH. In Exp. 1, non-gentle handled pigs fed ractopamine had decreased (P < 0.01) pH and increased temperature and tended (P < 0.09) to have higher lactate than other pigs. In Exp. 2, lactate and temperature changes from immediately post-handling to 1 h post-handling were not different for pigs fed L-carnitine or ractopamine suggesting that L-carnitine did not decrease recovery time of pigs subjected to non-gentle handling or fed ractopamine. These results suggest that pigs fed ractopamine are more susceptible to stress when handled aggressively. Because carnitine did not alleviate the negative effects of handling for pigs fed ractopamine, the improvement in drip loss from feeding carnitine must be due to a different mode of action.

Master of Science / Department of Animal Sciences and Industry / Joel DeRouchey / Mike Tokach / Six experiments using 3,862 pigs were conducted to evaluate effects of ractopamine HCl (RAC) feeding programs, dietary L-Carnitine and dried distillers grains with solubles (DDGS) on growth, carcass traits, loin and jowl fat quality of pigs, and energy and protein sources in nursery diets. In Exp. 1 and 2, RAC-fed pigs had greater (P<0.05) ADG, G:F and HCW compared with the control. Within RAC treatments, there were no differences in growth. Pigs fed step-up RAC had increased (P<0.01) percentage lean, fat-free lean index and loin depth but decreased (P<0.01) backfat than the control or constant treatment. In Exp. 2, pigs fed step-up RAC program had greater (P<0.05) ADG and G:F than the constant treatment. Pigs fed constant RAC had greater (P=0.002) carcass yield than controls. There were no overall differences in other carcass traits among treatments. In Exp. 3, dietary L-Carnitine improved (P<0.02) ADG and final BW. A DDGS × L-Carnitine interaction (quadratic, P<0.01) was observed for G:F. Pigs not fed DDGS had similar G:F, but in DDGS diets pigs fed 50 ppm L-Carnitine had worse G:F than those fed 100 ppm. Pigs fed L-Carnitine had greater (P<0.02) HCW compared with those not fed L-Carnitine. Increasing L-Carnitine up to 100 ppm increased HCW (quadratic, P<0.03) and backfat (quadratic, P<0.04), with the maximum response at 50 ppm dietary L-Carnitine. Increasing L-Carnitine increased (linear, P<0.04) purge loss of loin. Feeding DDGS increased (P<0.001) linoleic acid and iodine value of jowl fat compared with feeding no DDGS. However, feeding L-Carnitine did not change jowl fatty acid composition. In Exp. 4, 5 and 6, nursery pigs fed choice white grease (CWG) had improved (P<0.02) G:F than pigs fed a control diet or an alcohol based energy source. Also, pigs fed CWG had greater (P<0.04) ADG in Exp. 4 and 6 and had reduced (P<0.01) ADFI in Exp. 5. The alcohol based energy source improved (P<0.04) ADG and ADFI with no change in G:F in Exp. 4; but did not affect growth in Exp. 5 and 6. In Exp. 6, pigs fed AV-E Digest had equal performance as nursery pigs fed other specialty proteins.

Master of Science / Department of Animal Sciences and Industry / Joel M. DeRouchey / A total of 6,858 pigs were used in 6 experiments to evaluate the effects of crude glycerol, dried distillers grains with solubles (DDGS), Ractopamine HCl (RAC), NutriDense corn, and feeder adjustment on growing and finishing pig performance. In Exp. 1, pigs were fed diets with 0, 2.5, or 5% crude glycerol with 0 or 20% DDGS. Adding DDGS increased ADFI and decreased G:F with no differences for pigs fed glycerol. Neither glycerol nor DDGS affected any carcass characteristics. Pigs fed DDGS had increased iodine value in carcass fat. In Exp. 2, pigs were fed diets with 0 or 5% glycerol with 0 or 7.5 ppm RAC. Feeding RAC increased ADG and G:F and decreased ADFI while glycerol tended to improve G:F. Ractopamine HCl improved carcass traits. Loin chop drip loss worsened when glycerol and RAC were added separately, however, drip loss decreased when the combination of both were fed. Glycerol did not affect loin characteristics. Neither RAC nor glycerol influenced iodine value of carcass fat. Exp. 3 and 4 were conducted to determine the 4th limiting amino acid in diets containing NutriDense corn. In Exp. 3, pigs fed the positive control and the diet with added Ile, Trp, and Val (in combination) had greater ADG. Pigs fed added Ile or Trp had greater ADG than pigs fed the negative control indicates these amino acids were co-4th limiting for 37 to 59 kg pigs. In Exp. 4, pigs fed the positive control, added Trp, or the combination of added Ile, Trp and Val had greater ADG then pigs fed the negative control or pigs fed either Ile or Val indicates these amino acids were co-4th limiting for 77 to 100 kg pigs. Exp. 5 and 6 evaluated feeder adjustment on growth performance of finishing pigs. In Exp. 5, reducing feeder opening decreased ADFI. In Exp. 6, pigs were fed at three feeder opening and either a corn-soybean meal or byproduct-based diet. Diet type did not affect pig performance. Widening feeder openings increased ADG and ADFI. Feeder setting tended to influence G:F with the best G:F at the intermediate opening.

Doctor of Philosophy / Department of Animal Sciences and Industry / Michael E. Dikeman / Sixty cull cows were utilized to investigate the effects of feeding a single or sequence of β-adrenergic agonists (β-AA) on performance, mRNA expression, carcass traits, economics, meat palatability, and ground beef color. Treatments included: 1) concentrate fed for 74 d (C); 2) concentrate fed for 49 d then supplemented with ractopamine-HCl for 25 d (RH); 3) concentrate fed for 51 d then supplemented with zilpaterol-HCl for 20 d (ZH); 4), concentrate fed for 26 d then supplemented with RH for 25 d followed by ZH for 20 d (RH + ZH). No differences existed among treatments for performance or carcass characteristics. However, cows supplemented with ZH (ZH and RH + ZH treatments) had increased LM areas (P = 0.18) compared to control and RH cows. Sequential feeding of RH followed by ZH had no influence on β2-adrenergic receptor (AR) mRNA expression. However, β2-AR mRNA was increased (P < 0.05) in the RH and ZH treatments when RH or ZH was supplemented during the last 20 to 25 d of feeding. Myosin heavy chain (MHC) Type IIa mRNA decreased (P < 0.05) from d 24 to 51 in all cows, while MHC-IIx increased (P < 0.05) in the ZH and RH + ZH treatments during ZH supplementation. No differences were observed in ground beef color shelf-life among treatments. Effects of β-AA supplementation on meat palatability varied among muscles. Infraspinatus steaks had improved (P < 0.05) WBSF values with β-AA supplementation. Psoas major steaks from the RH + ZH treatment were rated as more tender than steaks from all other treatments. Non-enhanced LM steaks from ZH supplemented cows had higher (P = 0.12) WBSF values along with decreased (P < 0.0001) percentages of degraded desmin compared to control and RH cows. Collagen solubility of the LM was increased with ZH supplementation compared to RH and control cows. Enhancement of steaks with 0.1 M calcium lactate improved LM tenderness of β-AA supplemented cows. Implanting and feeding cull cows for 74 d, regardless of β-AA supplementation, added value by transiting cows from a “cull” cow to “white” cow market.