Master of Science / Department of Animal Sciences and Industry / Melvin C. Hunt / The objective of this study was to determine the effects of Zilmax® feeding duration (7.56 g/ton Zilmax for 0, 20, 30, or 40 d) on color development and stability of crossbred beef (B) and Holstein (H) semimembranosus (SM) steaks packaged in polyvinyl chloride overwrap (PVC), high-oxygen (80% O2, 20% CO2, HiOx) modified atmosphere packaging (MAP), and low-oxygen (0.4% CO, 30% CO2, 69.6% N2, LoOx) MAP. A 7.62-cm thick portion from beef and Holstein SM muscles (n = 120 total, 30 from each feeding duration) was removed, vacuum packaged, and stored until d 21 when two, 2.54-cm thick steaks were cut, overwrapped with PVC, and placed into retail display for 0 or 3 d. On d 10, the remaining muscle of the SM was enhanced, and five, 2.54-cm thick steaks were cut and assigned to 0, 3, or 5 d (HiOx) and 0 or 9 d (LoOx) of display. Measurements taken on the deep (DSM) and superficial (SSM) portions were: pH, L*, a*, b*, hue angle, and saturation indices, initial color, display color, and discoloration. No Diet × Display Day (P > 0.05) interaction occurred for display color or discoloration scores of B steaks in PVC. On d 1, PVC 30 d H steaks were brighter (P < 0.05) than 40 d H steaks in PVC; no differences (P > 0.05) in H PVC display color due to diet occurred on d 0, 2, and 3. For steaks in HiOx, the DSM of 20 and 30 d B steaks on d 4 and the DSM of 20 d B steaks on d 5 was brighter (P < 0.05) red than 40 d Zilmax B DSM. HiOx 20 d H steaks were darker red (P < 0.05) on d 5 of display and more discolored (P < 0.05) on d 3 to 5 than HiOx H steaks from all other diet regimens. For LoOx, 30 d B steaks were brighter (P < 0.05) red than 0 or 40 d steaks on d 0 and 9 of display. The DSM and SSM of LoOx H steaks from cattle fed Zilmax tended (P > 0.05) to be brighter red than control H steaks through 9 d of display. In conclusion, both HiOx and LoOx minimized color differences due to SM muscle areas. Feeding B cattle Zilmax for 20 or 30 d yields steaks equal to or better in color traits than cattle fed 0 or 40 d when packaged in PVC, HiOx, or LoOx. H steaks in LoOx had slight benefits in color stability when cattle were fed Zilmax for any duration, whereas H steaks in PVC had color advantages with only the 20 and 30 d durations. Packaging 20 d H steaks in HiOx resulted in less desirable color characteristics than all other feeding treatments. Keywords: zilpaterol, beef, Holstein, display color, modified atmosphere packaging, semimembranosus

In this study, 14 typical South African feedlot bulls received no beta-adrenergic agonist for the last 30 days of the finishing period (C), 14 received 120 mg R-salbutamol per animal per day for the last 30 days of the finishing period (S30), 13 received 120 mg Rsalbutamol per animal per day for the last 40 days of the finishing period (S40) and the last group of 13 bulls received 60 mg zilpaterol hydrochloride per animal per day for the last 30 days of the finishing period (Zh). All animals were slaughtered after a 3-day withdrawal period. Parameters included weight gain, feed intake, feed conversion rate, warm and cold carcass mass, dressing %, subcutaneous fat thickness, hide yield %, internal carcass fat distribution, % bone, % fat and % muscle of the prime rib-cut, carcass classification code, conformation, compactness, post-mortem carcass pH profiles, cooking loss, shear force, blood urea nitrogen, creatinine and residue levels of the beta-adrenergic agonists. No differences were observed between any of the four treatment groups concerning live feedlot performance. Bulls receiving the S30 and Zh treatments had lower internal carcass fat distribution compared to C bulls (P <0.05). Bulls receiving the S40 treatment had a lower % fat in the prime rib-cut compared to Zh bulls (P <0.05). Carcasses from S30 bulls had higher pH values 24 hours post mortem compared to carcasses from Zh bulls (P <0.01). Meat samples from Zh bulls had higher shear force, which indicates less tender meat, compared to samples from S40 bulls (P <0.05). Change in serum creatinine levels increased only in Zh treated bulls from the start to the end of treatment and may reflect a higher protein turnover in Zh bulls. The results of this study indicate that R-salbutamol has a more pronounced effect on fat metabolism in feedlot bulls compared to zilpaterol hydrochloride, while zilpaterol hydrochloride has a more pronounced effect on protein metabolism. The residue levels in samples of the liver, kidney, muscle and feaces from zilpaterol hydrochloride and R-salbutamol treated bulls were well below acceptable limits. / Dissertation MSc(Agric)--University of Pretoria, 2014 / gm2015 / Animal and Wildlife Sciences / MSc(Agric) / Unrestricted

Master of Science / Department of Animal Sciences and Industry / Michael E. Dikeman / The longissimus lumborum (LL) muscle from 117 steers and the LL, gluteus medius (GM), and triceps brachii (TB) from 132 heifers were obtained to evaluate the effects of feeding zilpaterol hydrochloride (Zilmax®; ZH) (7.56g/907kg on a 100% DM basis) on tenderness. Both genders were blocked by initial weight into 6 blocks of 4 pens. Pens were assigned to treatments of either 0, 20, 30 or 40 d on ZH, with a 3 d withdrawal. One steak was removed from each muscle for proximate analysis and three 2.54 cm thick steaks were vacuum aged for either 7, 14 or 21 d. Steaks were cooked to 70 ˚C and six 1.27 cm diameter cores were removed for Warner-Bratzler shear force (WBSF) determinations. All muscles from steers and heifers fed 30 and 40 d with ZH, had higher (P < 0.05) WBSF compared with controls. The WBSF of steer LL and heifer TB from the 20 d treatment was higher (P < 0.05) than controls. There were no treatment by aging interactions (P > 0.05) for WBSF of steaks from steer LL, heifer LL or heifer TB, but there was a treatment by aging interaction (P < 0.05) for WBSF of steaks from heifer GM. There were no differences (P > 0.05) in percent intramuscular fat for any muscle due to treatment. When using percent intramuscular fat as a covariate, differences in WBSF of steer LL and heifer TB were not altered, but there were slight differences in heifer LL and GM WBSF due to treatment when compared with not using percent fat as a covariate. Percentages of steaks with WBSF ≥ 5 kg increased as days on ZH increased and decreased as days of aging increased. Warner-Bratzler shear force values among the three aging times for steer LL control, 20 and 40 d treatments; all heifer LL treatments, and heifer TB 20 d were all positively correlated (P < 0.01) with each other. Feeding ZH for 20 d generally increased WBSF values, but means were still acceptable. Feeding ZH for 40 d was very detrimental to tenderness.

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.

Reports of endocrine disrupting potential of common environmental chemicals and the effects on reproductive health are well documented in literature. It has been suggested that deteriorating male reproductive health could be due to in utero exposures to these chemicals. The effects mediated through endocrine disrupting chemicals (EDCs) are on the fetus and may therefore be trans-generational. Ultimately, these chemicals land up in aquatic systems and affect wildlife and humans. Humans are exposed to these chemicals through multiple routes including atmosphere, water, occupational, domestic and food consumption. South Africa (SA) is an important livestock producer with about 13.8 million cattle within the feedlot industry contributing up to 80% of the total beef production. Veterinary growth stimulants (VGS) are used by beef producers to enhance growth in cattle. In SA, the following five VGS have been approved for use in beef products under the Register Act 36 of 1947, estradiol, progesterone and testosterone (natural), α'-zearalanol and trenbolone (synthetic). These VGS and their metabolites are environmentally stable compounds. The excretions from the animals are not treated and land up in the local aquatic systems, indirectly posing a health risk. In SA no research has been done on VGS associated with feedlot activities. The aim of this study was to investigate the effects of a mixture of VGS, as possible EDCs on the reproductive health and thyroid function in male rats in utero, during lactation and life-time exposure. The (anti)estrogenic and (anti)androgenic activity in water from specific feedlots was determined by using a battery of screening bio-assays. Water samples were collected over a period of a year and assessed for EDC activity in the recombinant yeast screen (YES), the T47D-KBluc (estrogenic) and the MDA-Kb2 (androgenic) bioassays. The OECD (Organization for Economic Co-operation and Development) 415 protocol, (1983) for a one-generation reproduction toxicity study, was modified to accommodate one control and three experimental groups. The experimental groups were orally gavaged with mixtures of: zilpaterol, diethylstilbestrol (DES) and α-zearalanol (Group 2; estogenic); with β'-trenbolone and methyltestosterone (MT) (Group 3; androgenic); a combination of compounds (Group 4; estrogenic and androgenic) and the Control group received cottonseed oil only. The bio-assay results indicated that water samples analysed from selected feedlots contained compounds with estrogenic activity. The shorter anogenital distance (AGD) (Group 3), decreased seminal vesicle mass (Group 4), decreased prostate mass (Group 4), increased lumen diameter (Group 3 and 4), lowered sperm concentration (Group 3), and increased T4 (Group 2 and 3) differed significantly from the control. The body weight of the males in Group 2 in the F2 generation was significantly lower than the control. The F2 females in Group 2, 3 and 4 were also significantly lower than the control. The reduced AGD, decreased seminal vesicle and increased T4 (thyroxine) might be the result of an estrogenic effect. The reduced sperm concentration might be the result of in utero and lactation exposure to these VGS. The bio-assays confirmed estrogenic activity in the feedlot water sources. The reproductive toxicology study findings confirm the hypothesis that VGS can act as EDCs and could therefore be responsible for negative reproductive effects and thyroid function. More research is needed to investigate the effects of VGS mixtures at different concentrations on male reproductive health, thyroid function and their offspring. AFRIKAANS : Goed gedokumenteerde literatuur dui aan dat chemikalieë wat algemeen in die omgewing gevind word, die potensiaal het om die manlike voortplantingstelsel aan te tas. Dit word gespekuleer dat in utero blootstelling verantwoordelik kan wees vir hierdie agteruitgang. Die fetus en daarop- volgende geslagte se gesondheid kan ook beÏnvloed word deur chemikalieë. Hierdie chemikalieë het die potensiaal om die watersisteme te bereik en gevolglik dier en menslike gesondheid te beÏnvloed. Blootstelling kan plaasvind deur verskeie roetes wat die atmosfeer, water, werksomstandighede, huishoudelike produkte en gekontamineerde voedsel insluit. Suid-Afrika (SA) is 'n belangrike produsent van vleisprodukte met omtrent 13.8 miljoen beeste wat bydra tot 80% van die vleisproduksie. Veterinêre-groei-stimulante (VGS) word gebruik om die vleisproduksie te verbeter. Vyf groei stimulante naamlik estradiol, progesteroon, testosteroon (natuurlike), α-zearalanol en trenboloon (sinteties) is goedgekeur onder die Wet 36 van 1947, vir groei produksie van beeste. Hierdie VGS en hul metaboliete is stabiel in die natuur. Die fekale en urinere uitskeidingsprodukte van die diere word nie behandel nie en eindig op in ons waterstelsels. Geen navorsing is nog in SA gedoen om die potensiële bydraes wat voerkrale tot die besoedeling van water lewer, te bestudeer nie. Die doel van die studie was om die gesamentlike effekte van mengsels VGS as moontlike endokrien-ontwrigtende chemicalieë (EOC) op die manlike voortplantingstelsel en tiroïdhormone van mannetjiesrotte na in utero-, gedurende laktasie- en na 'n leeftyd-blootstelling te bepaal. Die (anti)estrogeniese en (anti)androgeniese aktiwiteit in water vanaf spesifieke voerkrale is met behulp van 'n reeks biologiese seltoetse bepaal. Watermonsters is geanaliseer met die gisseltoets (YES)(estrogenies), die T47D-KBluc (estrogenies) en die MDA-Kb2 (androgenies). Die OECD 415 protokol (1983) vir een generasie reproduktiewe toksologie toets was aangepas om een kontrole en drie eksperimentele groepe te huisves. Die eksperimentele groepe rotte is oraal gedoseer met 'n mengsel van zilpaterol, dietielstilbestrol (DES) en α-zearalanol (Groep 2); β-trenboloon en metieltestosteroon (Groep 3); 'n kombinasie van al bogenoemde (Groep 4); en 'n kontrole groep wat katoensaad olie VGS ontvang het nie. Estrogeniese aktiwiteit en sitotoksisiteit was teenwoordig in die water vanaf die voerkrale. Die verkorte anogenitale afstand (AGD) (Groep 3), kleiner seminale vesikel (SV) massa (Groep 4), kleiner prostaat massa (Groep 4), groter lumen deursneë (Groep 3 en 4), laer spermtelling (Groep 3), verhoogde T4 (Groep 2 en 3), het almal statisties-betekenisvol van die kontrole groep verskil. In die F2 generasie het die liggaamsmassas van die mannetjies in Groep 2 en liggaamsmassas van die wyfies in Groepe 2, 3 , 4, almal statisties-betekenisvol laer as die kontrole Groep. Die verkorte AGD, kleiner SV en verhoogde T4 kan moonlik wees as gevolg van 'n estrogeniese effek en die verlaagde sperm konsentrasie weens 'n in utero en laktasie blootstelling. Die biologiese seltoetse het die teenwoordigheid van estrogeniese aktiwiteit in voerkrale se water bevestig. Die gevolge van die blootstelling van EOC mengsels op voortplantings-parameters bevestig die moontlikheid van EOC effek geassosieer met VGS. Verdere navorsing is nodig om die dosisresponsverhoudings van verskillende VGS te ondersoek. Copyright / Dissertation (MSc)--University of Pretoria, 2011. / School of Health Systems and Public Health (SHSPH) / Unrestricted