An experiment was conducted using forty-one Bonsmara steers (age ± 7 months) to determine the effect of zilpaterol hydrochloride (ZH) on the growth performance and carcass characteristics. The trial was structured using a completely randomized design with two treatments, control and ZH group. The steers were fed ZH for 28 consecutive days at the end of the finishing period and ZH was withdrawn from the diet 2 days prior to slaughter of the animals. The steers were placed in individual pens and weighed fortnightly throughout the 4 months trial. Zilpaterol hydrochloride (ZH) was included in the diet at a rate of 8.3 mg/kg of DM. Feeding of ZH increased (P< 0.05) body weight (BW) gain and ADG (1.102 vs. 1.444) and tended to increase (P = 0.067) feed efficiency (F:G) during the last month of the finishing period. There were no significant differences (P> 0.05) in daily dry matter intakes (DMI). For the control group, high treatment weight gains were significantly associated with high initial weight (r = 0.424, P = 0.049) and also high pre-treatment body weight (r = 0.678, P= 0.001). Treatment weight gain increased as the initial and pre-treatment weight gain increased in the control group. For the steers that were fed ZH, there was no significant correlation between the treatment body weight gain with initial weight (r = 0.097, P = 0.694) and also pre- treatment live weight (r = 0.393, P = 0.096). Supplementation of ZH significantly increased (P < 0.0001) the dressing percentage (56.4% vs. 58.4%) and had no significant (P>0.05) effect on the carcass weight. The outcome of the study suggest that supplementation of ZH in the diet during the last month of the finishing period enhances growth performance and shows the repartitioning capacity of the feed additive as a beta- agonist. / Agriculture and  Animal Health / M. Sc. (Agriculture (Animal Science)

An experiment was conducted using forty-one Bonsmara steers (age ± 7 months) to determine the effect of zilpaterol hydrochloride (ZH) on the growth performance and carcass characteristics. The trial was structured using a completely randomized design with two treatments, control and ZH group. The steers were fed ZH for 28 consecutive days at the end of the finishing period and ZH was withdrawn from the diet 2 days prior to slaughter of the animals. The steers were placed in individual pens and weighed fortnightly throughout the 4 months trial. Zilpaterol hydrochloride (ZH) was included in the diet at a rate of 8.3 mg/kg of DM. Feeding of ZH increased (P< 0.05) body weight (BW) gain and ADG (1.102 vs. 1.444) and tended to increase (P = 0.067) feed efficiency (F:G) during the last month of the finishing period. There were no significant differences (P> 0.05) in daily dry matter intakes (DMI). For the control group, high treatment weight gains were significantly associated with high initial weight (r = 0.424, P = 0.049) and also high pre-treatment body weight (r = 0.678, P= 0.001). Treatment weight gain increased as the initial and pre-treatment weight gain increased in the control group. For the steers that were fed ZH, there was no significant correlation between the treatment body weight gain with initial weight (r = 0.097, P = 0.694) and also pre- treatment live weight (r = 0.393, P = 0.096). Supplementation of ZH significantly increased (P < 0.0001) the dressing percentage (56.4% vs. 58.4%) and had no significant (P>0.05) effect on the carcass weight. The outcome of the study suggest that supplementation of ZH in the diet during the last month of the finishing period enhances growth performance and shows the repartitioning capacity of the feed additive as a beta- agonist. / Agriculture and  Animal Health / M. Sc. (Agriculture (Animal Science)

Thesis (M. Tech.) - Central University of Technology, Free State, 2010

Thesis (MScAgric)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Research conducted on beef cattle in Botswana investigated both growth and reproduction. These studies however, did not specifically determine the influence of the different environmental factors on growth in the Tswana and Composite beef cattle breeds. The establishment of a national beef herd recording and performance testing scheme requires knowledge on the appropriate adjustment methods of field data for the fixed effects such as sex of calf and age of dam. A fair comparison of birth and weaning weights between male and female calves, and calves born from young, mature and old dams will be derived from these adjustment factors. There is no information on adjustment factors for the Tswana and Composite cattle breeds in the country. Genetic parameters for growth traits in these breeds are not known and are needed for the implementation of the performance scheme in Botswana. The Composite breed resulted from a controlled crossbreeding programme using the Simmental, Brahman, Tswana, Tuli and the Bonsmara breeds. The Tswana animals are indigenous to the country and were sourced locally at the beginning of the growth evaluation trial in the two breeds. The objectives of the study were to use data collected from Tswana and Composite cattle breeds to estimate the influence of non-genetic factors on growth traits in the two breeds; to develop adjustment factors for the effects of sex of calf and age of dam; and to estimate genetic parameters (heritabilities and genetic correlations) for future genetic evaluations in both breeds. Data were collected over the period 1988 to 2006. A total of 2 257 records for the Composite breed and 5 923 records for the Tswana breed were available for analyses. Growth characteristics of interest in this study were birth weight (BW), weaning weight (WW), pre-weaning average daily gain (ADG1), 18 months weight (18MW) and post-weaning average daily gain (ADG2). Study 1 indicated that non-genetic effects of breed of calf, sex of calf, month and year of birth, previous parous state, weight of cow at parturition, age of dam, and age of calf at weaning significantly affected BW, WW, 18MW, ADG1 and ADG2 in both breeds. The Composite breed had higher BW, ADG1 and WW whereas the Tswana had higher ADG2 and 18MW. Pre-weaning growth rate increased with an increase in the age of the dam, reaching a peak in mature (5-12 years) cows and declined in cows 13 years and older. Conversely, post-weaning growth rates declined as age of dam advanced but increased in old (13 years and older) dams. Male calves were heavier than female calves for all the growth traits. Birth weight increased as calving season progressed whilst a decrease in WW was observed over the same period. Heifers gave birth to lighter calves when compared to mature multiparous dams. The Composite breed can therefore be considered for weaner production under ranch conditions while the Tswana can be reared under extensive systems due to its adaptability to the environment. Additive correction factors for effects of sex of calf and age of dam on BW and WW were studied separately for the Tswana and Composite in study 2. The least squares means procedure was used to derive age groups and the adjustment factors. The three age groups were young (4 years and below) dams, mature (5-12 years) dams and older (13 years and above) dams. Male calves were heavier than their female counterparts. The sex of calf adjustments for BW and WW were 2.75 and 8.21 kg in the Tswana, and corresponding values for the Composite 2.84 and 10.11 kg, respectively. Birth weight and WW increased as age of dam increased, reached maximum in mature dams and declined in older dams. Age of dam adjustment factors for BW in the 3, 4 and 13+ years age groups for the Tswana were 1.74, 0.96 and 1.87 kg, respectively. The corresponding values for the Composite were 2.28, 0.94 and 2.06 kg, respectively. Age of dam adjustment factors for weaning weight in the Tswana were 10.36 and 5.46 kg for age groups 3-4 and 13+ years, respectively. Adjustment factors for WW in the Composite were 13.84, 3.20 and 9.58 kg for age groups 3, 4 and 13+ years. The differences in adjustment factors obtained between the two breeds emphasize the need to compute and apply these factors within breed. Study 3 involved the estimation of genetic parameters for BW, WW, ADG1, 18MW and ADG2. Single-trait and multi-trait analyses were used in the estimation of (co)variance components by fitting an individual animal model (AM) and the animal maternal model (AMM) for the two breeds. Direct heritabilities for BW, WW, ADG1, 18MW and ADG2 in the Tswana were 0.45, 0.32, 0.37, 0.31 and 0.31, respectively from a single-trait AM analysis. Fitting the AMM resulted in direct heritabilities of 0.31, 0.20 and 0.16 for BW, WW and ADG1, respectively, while the maternal heritabilities were 0.11, 0.15 and 0.21, respectively. For the Composite the direct heritabilities for BW, WW and ADG1 were 0.58, 0.32 and 0.30, respectively with single-trait AM. Partitioning using the AMM resulted in the direct heritabilities for BW, WW and ADG1 of 0.55, 0.17 and 0.14, respectively, while corresponding maternal effects were 0.09, 0.15 and 0.15, respectively. The genetic correlations between direct and maternal effects were positive and ranged from 0.20 to 0.89. When using the multi-trait analysis and fitting the AM, the direct heritabilities for the Tswana were 0.45, 0.37, 0.34, 0.39 and 0.31 for BW, WW, ADG1, 18MW and ADG2, respectively. Genetic correlations between the growth traits ranged from 0.16 to 0.97. Direct (and maternal) heritabilities for BW, WW and ADG1 were 0.31(0.11), 0.19(0.15) and 0.14(0.17), respectively, in the Tswana. Correlations between direct heritabilities for BW, WW and ADG1 ranged from 0.45 to 0.95, while maternal effects ranged from 0.12 to 0.99. The magnitude of the heritabilities indicates an existence of the opportunity to make genetic progress through selection in both breeds. Selection based on WW seems to be the ideal procedure to bring genetic improvement in the Tswana without detrimental long term effects. / AFRIKAANSE OPSOMMING: Navorsing wat op die vleisbeesrasse in Botswana gedoen is, het hoofsaaklik op beide groei en reproduksie gehandel. Hierdie studies het egter nie spesifieke gefokus op die bepaling van die invloed wat verskillende omgewingsfaktore op die groei van saamgestelde (d.i. Composite) en die Tswana vleisbeesrasse het nie. Die bepaling van ʼn nasionale vleisbees rekordhouding- en prestasietoetsskema verg kennis van die mees gepaste metode om velddata vir vaste effekte soos geslag van die kalf en ouderdom van die moeder aan te pas. Hierdie aanpassingsmetodes sal lei tot die regverdige vergelyking van geboorte- en speengewigte tussen manlike en vroulike diere, sowel as van kalwers gebore van jong, volwasse of ou moeders. Tans is daar geen inligting oor aanpassingfaktore vir die Tswana en saamgestelde vleisbeesrasse in Botswana bekend nie. Geen genetiese parameters vir groei-eienskappe vir geeneen van die rasse is beskikbaar nie en word benodig vir die implementering van die prestasie skema in Botswana. Die saamgestelde ras is die produk van ʼn beheerde kruisteeltprogram, wat onderskeidelik die Simmental, Brahman, Tswana, Tuli en die Bonsmara beesrasse ingesluit het. Die Tswana ras is inheems aan Botswana en vanaf plaaslike bronne vir die groei evaluasie studie bekom. Die doelwitte van die studie was eerstens die analisering van data wat van beide die Tswana en saamgestelde rasse ingesamel is, om die invloed van nie-genetiese faktore op die groei eienskappe te bepaal om ten einde aanpassingsfaktore vir die effek van geslag van die kalf en ouderdom van die moederdier te ontwikkel. ʼn Tweede doelwit was die bepaling van genetiese parameters (oorerflikhede en genetiese korrelasies) vir die gebruik in toekomstige genetiese evaluering van beide rasse. Data is vanaf 1988 tot 2006 ingesamel. ʼn Totaal van 2 257 waarnemings vir die saamgestelde ras en 5 923 waarnemings vir die Tswana ras is ontleed. Groei eienskappe wat in die studie ondersoek is, het geboortegewig (BW), speengewig (WW), voorspeen gemiddelde daaglikse toename (ADG1), 18-maand gewig (18MW) en naspeense gemiddelde daaglikse toename (ADG2) ingesluit. Studie een het aangedui dat nie-genetiese effekte van die ras van die kalf, die geslag van die kalf, maand en jaar van geboorte, vorige dragtigheidsstatus, koei se gewig met geboorte van kalf, ouderdom van die moederdier en die speenouderdom van die kalf het ʼn betekenisvolle invloed op BW, WW, 18MW, ADG1 en ADG2 van beide rasse gehad. Die saamgestelde ras het hoër waardes vir BW, ADG1 en WW gehad, terwyl die Tswana ras hoër waardes vir ADG2 en 18MW geopenbaar het. Voorspeense groeitempo het toegeneem met ʼn toename in die ouderdom van die moederdier, met ʼn piek in volwasse (d.i. 5-12 jaar ouderdom) moeders en ʼn afname in koeie 13 jaar en ouer. Omgekeerd het naspeen groeitempo afgeneem met ʼn toename in die ouderdom van die moederdier en weer begin toeneem vir ou (d.i. 13 jaar en ouer) koeie. Geboortegewig het toegeneem met die verloop van die kalfseisoen, terwyl ʼn afname in WW vir dieselfde periode aangeteken is. Verse het, wanneer hulle met volwasse koeie vergelyk is, het geboorte aan ligter kalwers gegee. Die saamgestelde ras kan dus oorweeg word vir die produksie van speenkalwers onder kommersiële intensiewe toestande, terwyl die Tswana ras, op grond van sy beter aanpassing by ekstensiewe omstandighede waar die moederlike invloed nie voorkom nie, vir produksie onder ekstensiewe omstandighede gebruik kan word. In studie 2 is die additiewe korreksie faktore vir die invloed van geslag van die kalf en moederouderdom op BW en WW apart vir die twee rasse bestudeer. Die geslag van die kalf x ouderdom van die moederdier interaksie was nie betekenisvol vir enige van die rasse nie. Dus kan geen aanpassing vir die ouderdom van die moeder binne geslagte vir enige van die twee rasse gemaak word nie. Die kleinste kwadraat gemiddeldes metode is gebruik om die ouderdomsgroepe en aanpassingsfaktore te bepaal. Die drie ouderdomsgroepe was jong (d.i. 4 jaar en jonger) koeie, volwasse (d.i. 5-12 jaar ouderdom) en ouer (d.i. 13 jaar en ouer) koeie. Daar is gevind dat manlike kalwers swaarders as hulle vroulike eweknieë is. Die aanpassingswaarde vir die geslag van die kalf vir BW en WW was 2.75 kg en 8.21 kg in die Tswana en 2.84 kg en 10.11kg vir die saamgestelde ras. Geboortegewig en WW het toegeneem met ʼn toename in die ouderdom van die moeder. Dit het ʼn maksimum bereik in volwasse koeie en afgeneem vir koeie ouer as 13 jaar. Die aanpassingsfaktore vir die ouderdom van die moederdier vir BW in die 3, 4 and 13+ jarige ouderdomsgroepe vir die Tswana ras was onderskeidelik 1.74 kg, 0.96 kg en 1.87 kg. Die ooreenstemmende waardes vir die saamgestelde ras was onderskeidelik 2.28 kg, 0.94 kg en 2.06 kg. Aanpassingsfaktore vir WW vir die Tswana ras was 10.36 kg en 5.46 kg vir onderskeidelik die 3-4 jaar en 13+ jaar en ouer ouderdomsgroepe. Aanpassingsfaktore vir WW in die Composite ras was 13.84 kg, 3.20 kg en 9.58 kg vir onderskeidelik die 3 jaar, 4 jaar en 13 jaar en ouer ouderdomsgroepe. Verskille in die onderskeie parameters vir die twee rasse beklemtoon die noodsaaklikheid vir die berekening en toepassing van die onderskeie aanpassingfaktore vir en binne elke ras. Studie 3 het die bepaling van die genetiese parameters vir BW, WW, ADG1, 18MW en ADG2 behels. Enkel- en multivariaat analises is gebruik vir die skatting van die (ko)variansie komponente deur ʼn direkte diermodel (AM) en ʼn dier-maternale model (AMM) vir die twee rasse te pas. Direkte oorerflikhede vir BW, WW, ADG1, 18MW en ADG2 vir die Tswana ras was onderskeidelik 0.45, 0.32, 0.37, 0.31 en 0.31, vir ʼn enkelvariaat AM analise. Die pas van ʼn AMM het direkte oorerflikhede van 0.31, 0.20 en 0.16 vir onderskeidelik BW, WW and ADG1 gegee, terwyl die maternale oorerflikhede onderskeidelik 0.11, 0.15 en 0.21 was. Vir die saamgestelde ras was die direkte oorerflikhede vir BW, WW en ADG1 onderskeidelik 0.58, 0.32 en 0.30 vir die enkelvariaat AM analise. Verdeling (partisie) van die AMM het direkte oorerflikhede vir BW, WW en ADG1 van onderskeidelik 0.55, 0.17 en 0.14 gegee, terwyl die ooreenstemmende maternale effekte onderskeidelik 0.09, 0.15 en 0.15 was. Die genetiese korrelasies tussen die drekte en maternale effekte was positief en tussen 0.20 en 0.89. Met die multivariaat analise en die pas van die AM, is direkte oorerflikhede van 0.45, 0.37, 0.34, 0.39 en 0.31 vir onderskeidelik BW, WW, ADG1, 18MW en ADG2, vir die Tswana ras bereken. Genetiese korrelasies tussen die groei eienskappe het gewissel tussen 0.16 tot 0.97. Direkte (en maternale) oorerflikhede vir BW, WW en ADG1 was onderskeidelik 0.31(0.11), 0.19(0.15) en 0.14(0.17), vir die Tswana ras. Korrelasies tussen die direkte oorerflikhede vir BW, WW en ADG1 het gewissel tussen 0.45 en 0.95, terwyl die maternale effekte tussen 0.12 en 0.99 gewissel het. Die grootte van die oorerflikhede dui op die moontlikheid van genetiese vordering wat deur seleksie in beide rasse gemaak kan word. Seleksie op grond van WW blyk die mees gepaste wyse te wees waarmee genetiese vordering binne die Tswana ras gemaak kan word, sonder enige langtermyn nadelige effekte.

No description available.

In KwaZulu-Natal the production of beef in summer from veld is a common enterprise. Many techniques are available to optimise the productivity of this enterprise, from improving the quality of the grazing resource (planted pastures) to improving the diet of animals using nutritional supplements. To gain an insight into the production potential and financial returns possible from such improvements a trial was established at the Ukulinga Research Farm during two consecutive summer growing seasons (1997-1998 and 1998-1999). The aim was to determine the optimum beef production system for the area from both veld and kikuyu pastures. To evaluate the benefits of supplying supplementary nutrition, four alternate feed supplements, namely: 1) a Standard commercially available molasses-based protein/mineral/energy supplement; 2) a Brewers grain based protein/mineral/energy supplement, and two supplements consisting of the Brewers grain ration with either; 3) Avoparcin (an additive that improves dietary energy) or 4) Bentonite (an additive that increases the bypass of protein) were compared. As stocking rate has been shown to influence the quality of the diet consumed, the kikuyu pasture was grazed at both the recommended (1.92 LSD ha¯¹) and half the recommended stocking rate for the region. In addition, a commercial hormonal implant was applied to half of the cattle in each treatment. Grazing was monitored using the falling plate disc meter to measure pasture bulk density and laboratory analyses of herbage grab samples for digestibility and crude protein percentage. Cattle were weighed on a weekly basis and their condition was scored prior to slaughter. All enterprise costs and returns were recorded to facilitate financial analyses of the five treatments. Low rainfall and high midsummer temperatures had a detrimental effect on the productivity of the grazing and hence it was difficult to optimise production in either season. In the first season, a midsummer drought decreased the quality and quantity of both veld and kikuyu, limiting mass gain during the latter part of the season. A delay in the onset of rain at the start of the second season limited the available grazing season to 121 days as opposed to 154 days, though fodder production during the season was not limited. Trends in herbage production (quality and quantity) from veld showed moderate quality (Crude protein 7.02%; digestibility 50.2%) with an average available herbage of 1670 kg DM ha¯¹. As anticipated, kikuyu had higher quality (Crude protein 10.84%; digestibility 53.5%) and available herbage (2730 kg DM ha¯¹). These results were similar to regional benchmarks. The variable rainfall highlighted both the drought tolerance of veld and the minimum water requirements of kikuyu pastures. Lighter stocking rates tended to reduce the negative impact of moisture stress on Kikuyu pastures. The best method of producing beef (averaged over two seasons) was from heavily stocked Kikuyu pastures using the Standard supplement (1107.63 kg livemass ha¯¹). Cattle grazing veld and utilising the Avoparcin supplement produced beef at a rate of 95.96 kg ha¯¹. In comparison, the unsupplemented cattle grazing Kikuyu produced 834.87 kg ha¯¹, whilst veld grazing produced 64.43 kg ha¯¹. Hormonal implants significantly (P≤0.05) improved beef production from all sources of grazing. A lack of rain limited grazing time, causing all the cattle to be marketed whilst too lean - this negatively affected live mass gain and, hence, net financial. Although improved biological production is desirable, it is important to ensure that these gains are financially sustainable. Within the trial environment, implanted cattle fed the Standard supplement and grazing Kikuyu pastures at a high stocking rate provided the highest average gross margin of R 859.59 ha¯¹. Changing to this production system from unsupplemented veld improved expected profit by R 632.58 ha¯¹ (averaged over both seasons). Further financial analyses indicated that beef purchase price had the greatest influence on the added profit from switching from the control treatment. From a scientific standpoint these data are conclusive but it is important to remember that consumer pressure and concerns can often limit the introduction of production improvements. Such is the case with both hormonal implants and antibiotic feed additives (Avoparcin) although considering the impact of such limitations is speculative and beyond the scope of this trial. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Leptin, a 16 (kilo Dalton) kDa hormone secreted predominantly by white adipocytes, regulates reproduction, energy intake and expenditure, and is involved in immune system function. Previous studies have identified associations between polymorphism E2FB in the leptin gene (lep) of cattle and milk quality and quantity, feed intake, and fat deposition in dairy and beef cattle though further studies have shown inconclusive results. Furthermore, indigenous South African cattle have not been involved in lep investigations or the applicability of the marker in South African beef grading systems. An investigation was conducted into the association of an SNP of a cytosine (C) to thymine (T) SNP (single nucleotide polymorphism) mutation in exon 2 of the bovine lep (leptin) gene with weight gain, body condition, carcass fat content and quality in a population of indigenous Nguni cattle (n = 70) as well as a population of exotic British Hereford cattle (n = 54). The Hereford population had higher T-allele frequencies and a lower P-value (P = 0.172) for the E2FB genotypes than the Nguni population (P = 0.958). The resulting E2FB lep genotypes CC, CT and TT did not show an association with the pre- and post-slaughter traits initial live weight (ILW), body condition score (BCS), slaughter live weight (SLW), carcass fat content (FAT), carcass conformation (CFN) or warm carcass mass (WCM) for either population though t-tests revealed an association with the CT genotype with increased ILW than TT and a significantly higher WG in the TT genotypes than the CT (P<0.05). Subsequently, differences in pre- and post-slaughter traits in both populations were largely attributable to breed differences. The Hereford population exhibited significantly higher WG, CFN, SLW, WCM and CCM (P<0.05) than the Nguni population. The Nguni displayed significantly higher ILW and BCS values when graded in terms of the commercial South African AAA feedlot system. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Perennial ryegrass (PRG, Lolium perenne) is a hardy cool-season grass that is infected with the endophytic fungus Neotyphodium lolii, which enables the plant to be insect repellant and drought resistant, lowering the use of insecticides and fertilizers. However, this fungus produces the compound lolitrem B (LB, m/z 686.4) which causes the tremorgenic neurotoxicity syndrome 'ryegrass staggers' in livestock consuming forage which contains <2000 ppb LB. Ergovaline (EV, m/z 534) is a vasoconstrictor normally associated with tall fescue (Festuca arudinacea), but has also been found in endophyte-infected PRG. Past research has shown a strong linear correlation between levels of LB and EV in PRG. The purpose of this study was to examine the linear relationship between EV and LB in feces and determine common metabolites. To accomplish this, four groups of steers (n=6/group) consumed endophyte- infected PRG over 70 days consumed the following averages of LB and EV: group I 2254ppb LB/633 ppb EV; group II 1554ppb LB/ 373ppb EV, group III 1011ppb LB/259ppb EV, and group IV 246ppb LB/<100ppb EV. Group I in week 4 was inadvertently given a washout period at which time the steers consumed the amount of LB and EV given to group IV (control). Both feed and feces samples were extracted using difference solid phase extraction methods and quantified by HPLC-fluorescence for LB and EV. Concentrations of EV and LB obtained through HPLC-fluorescence in both PRG and feces showed a linear relationship. Additional screening for metabolites was conducted LC-MS/MS and showed possible oxidation and reduction metabolites for both toxins. / Graduation date: 2013

Made available in DSpace on 2015-03-26T13:55:24Z (GMT). No. of bitstreams: 1 texto completo.pdf: 520868 bytes, checksum: 2d8a7216ec49d2191fe503c2a550a5bb (MD5) Previous issue date: 2014-02-21 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The present work was conducted aiming to evaluate the effects of feed restriction during post-weaning growing phase on animal performance, carcass traits and meat quality of Nellore feedlot finished with high-grain diet. To better discussing, the data were divided into two chapters; the first is about animal performance and carcass traits, while the second chapter is about meat quality. 39 young bulls with 8.5 ±0.2 months old and initial body weight of 230.4 ±5.6 kg, were used in this trial. At the beginning, five animals were slaughtered as reference group and the thirty-five remaining were allocated in one of the treatments, that were: low gain in growing phase and high gain in finishing (LH), medium gain in growing phase and high in finishing (MH) and high gain in both phases (HH). At the end of growing phase 5 LH, 6 MH and 6 HH animals were slaughtered and the remaining started the finishing phase and were slaughtered in the end of this phase. The intakes of dry mater (DM) and all nutrients did not differ (P>0.05) among the treatments when expressed as kg/d. However when DM and NDFap were expressed in g.kg BW-1.d- , were higher (P<0.05) for MH and LH than HH. The LH animals showed in the finishing phase greater (P<0.05) daily gain of body weight (BW) and empty body weight (EBW), greater carcass gain, greater carcass protein gain and greater carcass water gain than MH and HH. The LH and MH gain of non-carcass components was greater (P<0.05) than HH. The LH treatment had greater (P<0.05) feed efficiency and better carcass feed conversion than MH and HH. The BW and the EBW at the end of finishing phase were greatest for the HH animals, lowest for the LH and intermediate for MH that did not differ than HH and LH. The carcass weight and carcass dressing percentage were higher (P<0.05) for HH than others treatments. The HH treatment had greater (P<0.05) fat thickness. About the beef quality, at the end of growing phase significant difference (P>0.05) was observed for the final sarcomere length, with the highest average value to HH treatment, the lowest to LH and intermediate for MH that did not differ from the others two treatments. At the end of growing phase, the LH treatment showed a lower (P<0.05) redness (a*) than MH and HH treatments, that did not differ among themselves. At the end of growing phase, was found significant difference (P<0.05) for the beef yellowness (b*), the HH treatment had the highest average value, the LH treatment had the lowest and the MH had intermediate value, which did not differ from the others. At the end of finishing phase did not significant differences (P>0.05) were observed among the treatments for all evaluated beef traits. It is concluded that young Nellore cattle previously submitted to qualitative and quantitative food restriction, have higher daily gains of body components and are more efficient to convert food to carcass. Young Nellore cattle when previously submitted to qualitative restriction, exhibit complete catch up during finishing phase, without exhibit compensatory gain. Previously restricted animals have greater relative intakes of DM and fiber, higher gain of non-carcass components, lower transference from live weight gain to carcass gain, lower carcass dressing percentage and produce lighter and leaner carcasses. About the beef quality, it is concluded that dietary restriction post- weaning does not affect the beef quality after a long finishing phase. The evidences suggest that in the chilling conditions of this trial, the carcasses should be a minimum of 3.6 mm back fat thickness to prevent negative impacts of cold shortening on final sarcomere length and consequently on meat tenderness. / O presente trabalho foi desenvolvido com o objetivo de avaliar o efeito da restrição alimentar na fase de crescimento, após o desmame, sobre o desempenho produtivo e as características da carcaça e da carne produzida por tourinhos Nelore terminados em confinamento com dieta de alto grão. Os dados foram apresentados em dois capítulos, sendo no primeiro descrito o desempenho produtivo e as características de carcaça, enquanto o segundo capítulo abordou as características qualitativas da carne. Foram utilizados 39 machos não castrados Nelore, com idade média inicial de 8,5 ±0,2 meses e peso corporal médio de 230,4 ±5,6kg, que foram confinados. Inicialmente, foram abatidos cinco animais para determinar a composição corporal inicial, os demais foram distribuídos nos tratamentos, que consistiram de baixo ganho na fase de crescimento e alto na terminação (BA, n=10), médio ganho na fase de crescimento e alto na terminação (MA, n=12) e alto ganho em ambas as fases (AA, n=12). Ao final da fase de crescimento cinco animais do tratamento BA e seis dos MA e AA foram abatidos. Os demais permaneceram no experimento sendo abatidos ao final da fase de terminação. O consumo em kg/d de MS e dos nutrientes na terminação não diferiram (P>0,05) entre os tratamentos. O consumo de MS e FDNcp, quando expressos em g.kg BW-1.d-1, não diferiram (P>0,05) entre os tratamentos MA e BA, que foram maiores que o AA. O tratamento BA apresentou maiores (P<0,05) ganhos médios diários de peso vivo (PV), peso de corpo vazio (PCVZ), de carcaça e de proteína e água na carcaça em relação aos tratamentos MA e AA que não diferiram (P>0,05) entre si. O ganho de componentes não carcaça foi menor para o tratamento AA em relação aos demais e não diferiu (P>0,05) entre os tratamentos BA e MA. O tratamento BA apresentou maior eficiência alimentar e melhor conversão alimentar de carcaça que os demais tratamentos. O PV e o PCVZ ao final da fase de terminação foi maior (P<0,05) para o tratamento AA, menor para o BA e intermediário para o MA que não diferiu (P>0,05) dos demais tratamentos. Os valores de peso de carcaça e rendimento de carcaça foram maiores para o tratamento AA em relação aos demais. Os animais do tratamento AA apresentou maior (P<0,05) espessura de gordura subcutânea. Ao final da fase de crescimento, foi observada diferença significativa (P>0,05) para o comprimento final do sarcômero, sendo o valor médio maior para o tratamento AA, menor para o BA e intermediário para o MA que não diferiu dos outros dois tratamentos. Ao final da fase de crescimento foi observado também, um menor (P<0,05) valor de intensidade de vermelho (a*) para os animais do tratamento BA em relação aos tratamento MA e AA, que não diferiram entre si. No abate ao final da fase de crescimento, foi encontrado diferença significativa (P<0,05) para o valor de intensidade de amarelo (b*) da carne, sendo o maior valor médio obtido para o tratamento AA, o menor para o BA e valor intermediário foi obtido para o tratamento MA, que não diferiu dos demais. Não foram observadas diferenças significativas (P>0,05) para as demais características avaliadas nos bifes obtidos ao final da fase de crescimento. Não foi observada nenhuma diferença significativa (P>0,05) entre os valores médios dos tratamentos para as características qualitativas avaliadas nos bifes obtidos ao final da fase de terminação. Conclui-se então que, animais Nelore jovens submetidos à restrição alimentar quali e quantitativa prévia, apresentam maiores ganhos diários dos componentes corporais. Quando submetidos previamente à uma moderada restrição qualitativa, compensam na fase de terminação todo o peso que deixaram de ganhar durante a restrição, sem no entanto aumentarem expressivamente o seu ganho médio diário. Animais previamente restritos, apresentam maior consumo relativo de MS e de fibra, maior ganho de componentes não constituintes da carcaça, menor transferência do ganho de peso vivo para a carcaça, menor rendimento de carcaça e produzem carcaças mais leves e mais magras. Apesar dos animais em crescimento compensatório terem apresentado melhor conversão alimentar de carcaça na fase de terminação, considerando o período total do experimento, os animais em crescimento contínuo são mais eficientes na conversão de alimento em carcaça. Quanto às características qualitativas da carne, pode-se concluir que a restrição alimentar após o desmame não afeta as características qualitativas da carne quando os animais passam por longo período de terminação. Os resultados obtidos sugerem que, em condição de resfriamento da carcaça similar à do presente trabalho, as carcaças devem ter um mínimo de 3,6 mm de espessura de gordura subcutânea para prevenir impactos negativos do cold shortening sobre o comprimento final do sarcômero e consequentemente sobre a maciez da carne.

The objective of the study was to evaluate cow reproductive performance in the sweetveld and sourveld communal grazing areas of the Eastern Cape Province, South Africa. In the first experiment, farmer perceptions were obtained using participatory rural appraisals. Farmers ranked lack of fences, tick-borne diseases, poor animal condition during winter and poor breeding practices, respectively as major constraints limiting cattle production in the Eastern Cape. Cattle, sheep and goats, in that order, were ranked as the most important livestock species and were mainly kept for meat, cash and ceremonies, respectively. The non-descript cattle breed was the most common breed found in the smallholder areas. Most farmers preferred Nguni breed because of its adaptive attributes. In the second experiment, structured questionnaires were administered, between June and August 2006, to a total of 551 farmers from 10 communities of the Eastern Cape. There was a significant association (P<0.05) between the use of pregnancy diagnoses and community. About 87 and 77 % of the interviewed farmers did not respond on the extent of pregnancy and calving rates in their herds. A higher proportion of farmers from Hekele (51%) and from Upper Mnxe (45.3%) communities reported low number of bulls as a major constraint to cow reproductive performance. Body condition and ovarian activity were measured in the sweet and sour veld types. Body condition score of animals was measured from March iii 2007 until January 2008 and ovarian activity of cows was performed by a veterinarian through rectal palpation in June, August and October 2007 and January 2008. From March to July, there was a marked decline in body condition on both veld types. In the sweetveld, body condition improved from September until January, whereas in the sourveld the improvement in body condition started in October. The cows in both veld types conceived throughout the year. Most cows in the sweetveld were cycling in January and August (P<0.05) whereas in the sourveld there was no distinct period when the animals were cycling. Overall, there were no differences in the proportion of cows that were cycling between the sour and sweet veldts (P>0.05). There were more cows cycling in sourveld in October than in the sweetveld. Reproductive performance of cows in communal areas could, therefore, be determined by levels and quality of nutrition. Keywords: Participatory rural appraisals; Structured questionnaires; Farmer participation; Farmer perceptions; Body condition scoring; Ovarian activity; Pregnancy diagnoses.