I examined the influence of cyclic feeding regime on fillet yield and quality and their genetic architecture in rainbow trout (Oncorhynchus mykiss). Two lots of half-sib families produced in September and December were exposed to periods of reduced ration followed by increased ration. Fish fed cyclically reduced rations weighed less and had smaller fillets and body proportions relative to controls. They also had less estimated muscle and visceral lipid but also more proportional visceral mass. Lots and families within lots differed significantly for the majority of traits. Genotypic analysis with 23 microsatellite markers spanning 19 linkage groups detected QTL for all traits over multiple linkage groups that were not necessarily consistent between feeding regime and parental lot. Linkage groups RT-9 and 29 had the largest QTL effects for fillet composition traits and overall body size across the greatest number of parents sampled.

Processes that regulate site of fat deposition in beef cattle are poorly understood. For the producer to procure the greatest profit, it is ideal to maximize intramuscular fat. Furthermore, to understand the physiological mechanisms affecting fat depots, it is necessary to evaluate hormones involved in growth regulation. Using a 2 x 2 factorial design of treatments, four experiments were conducted to examine two adipogenic compounds, chlortetracycline and dexamethasone. Synovex-S® and Revalor-S® were used to investigate potential interactions between growth implants and adipogenic compound. Growth performance, carcass quality, organ and fat mass and plasma hormone concentrations were measured in these studies. In Exp. 1, 24 steers received either 0 or 350mg chlortetracycline/d, with or without Synovex-S®. On d 30, 56 and 106, steers received a bolus injection of 1 ug/kg BW thyrotropin-releasing hormone and 0.1 ug/kg BW GH-releasing hormone and serial blood samples were collected. Synovex-S® increased (P ≤ 0.009) rate and efficiency of gain and decreased (P = 0.05) time to peak for GH concentrations. Chlortetracycline attenuated (P ≤ 0.05) the effects of implant on triiodothyronine release, slaughter weight and carcass quality. In Exp. 2, 96 steers received either 0 or 39.6 ppm chlortetracycline/d, with or without Revalor-S®. Implant increased (P < 0.0001) ADG; however, efficiency of gain was greater for implanted steers in the absence of chlortetracycline (interaction, P ≤ 0.03). In Exp. 3, 144 steers received either 0 or 0.09 mg dexamethasone/kg BW on d 0, 28 or 56, with or without Revalor-S®. Average daily gain was lower (P = 0.0003) for implanted steers receiving dexamethasone compared to those receiving no dexamethasone (interaction, P = 0.05). Omental fat mass was greater (P = 0.01) for non-implanted steers receiving dexamethasone compared to no dexamethasone (interaction, P = 0.006). In Exp. 4, 96 steers received either 0 or 0.09 mg dexamethasone/kg BW on d 0, 28, 56 or 84, with or without Revalor-S®. Average daily gain and efficiency of gain were both 13% greater (P ≤ 0.05) with implant. Conversely, DEX lowered ADG by 10% (P = 0.007). There were no effects of treatment on fat mass weights.

Minimising variability in carcass quality to better meet market specifications is a priority for Australian pig producers, however issues with variability in carcass fat distribution have recently been raised, particularly in the belly primal. There has been a rapid increase in the use of low-cost, deep-litter (DL) housing systems in Australia over the past 15 years for rearing pigs. The inherent differences between the physical, thermal, and social environments of conventional (C) and DL production systems may well alter the growth path of the pig and subsequently alter fat metabolism and hence fat deposition and distribution. The general industry view is that pigs finished in DL housing are fatter and grow less efficiently than pigs finished in C housing, however contrasting carcass and growth performance results have been reported between housing systems. It is likely that the different housing environments affect the maintenance energy requirements of the growing pig, thereby affecting the availability of substrates for fat deposition and/or the requirements for fat mobilisation. Hence, raising pigs in C and/or DL production systems was identified as a likely contributor to variability in carcass fat distribution via the effects of the disparate environments on fat metabolism. The overall purpose of this thesis was to establish the effect of keeping pigs in C and/or DL housing systems on fat metabolism, and therefore fat deposition in the growing pig and fat distribution in the finished carcass. Industry considers that finishing pigs in C facilities allows greater flexibility in feeding and marketing decisions, allowing growth efficiency and backfat to be managed more effectively than in a DL system. Therefore an aspect of this thesis was to also examine the effects of an alternative management strategy, raising pigs in a combination of DL and C housing, on growth performance and fat deposition and distribution in the carcass. The presence of straw bedding is a major difference between C and DL housing systems. This was identified as a probable contributor to the differences in growth performance and carcass fat distribution found between pigs raised in the different housing systems, via its thermal properties and/or the ingestion of the straw on pig growth. Experiment 1a and 1b were designed to test the hypothesis that the growth path differs for pigs raised in C and DL housing systems, affecting biochemical indicators of fat metabolism and therefore fat accretion and distribution in the carcass. The study was conducted as a serial slaughter of pigs housed in C and DL systems allowing the pattern of fat accretion, and therefore the distribution of fat in the carcass, to be determined from 15¨C185 kg live weight (LW). The results confirmed the hypothesis that the growth path, fat accretion and fat distribution in the carcass differed for pigs raised in C and DL housing systems. In Experiment 1a, elevated lipogenic enzyme activities, higher percentages of saturated fatty acids (SFA) and higher concentrations of plasma glucose and lactate indicated lipogenesis was elevated in C pigs to 13 weeks of age, compared to young DL pigs, suggesting that fat accretion was higher in young C pigs. At 24 weeks of age however there was a shift in lipogenic enzyme activities, the percentage of SFA in backfat and the concentration of plasma glucose were higher in DL-housed pigs than C-housed pigs, indicating higher rates of lipogenesis. Elevated concentrations of plasma non-esterified fatty acids (NEFA) and glycerol in DL pigs indicated that lipolysis, or fat mobilisation, was higher in DL-housed pigs for the entire growth period. The results from Experiment 1b clearly indicated that during early growth, C pigs grew faster than DL pigs (0.71 vs 0.66 kg/day, P¡Ü0.05) and were heavier between 8-23 weeks of age (P¡Ü0.05). Therefore in conjunction with the results of Experiment 1a, it was expected that young C pigs would be fatter than DL pigs of the same age. However, dissection indicated no treatment differences in total carcass composition, although there was an effect of housing on carcass fat distribution with a trend (P=0.087) for a lower ratio of fat:lean in the belly primal of DL pigs compared to C pigs at 13 weeks of age. After 20 weeks of age however, growth rates were similar for pigs in both housing treatments and by 26 weeks of age there were no treatment differences in live weight (LW) but the rate of fat accretion in DL pigs, particularly in the loin and belly primals, increased rapidly. Differences in the thermal environments of C and DL housing, and therefore differences in the energy demand for thermoregulation, were likely to have contributed to the differences measured in lipogenesis, growth performance and carcass fat distribution. Experiment 2a and 2b tested the hypothesis that moving pigs from DL to C housing for finishing would improve overall growth performance and reduce carcass fatness compared to pigs raised in wean-to-finish DL housing. The biochemical measurements indicated few differences in the rate of lipogenesis between 13-week-old C and DL pigs. However, and in agreement with the findings from Experiment 1a, elevated plasma NEFA concentrations in DL pigs suggested higher rates of lipolysis. Up to 13 weeks of age, pigs in the DL housing system grew faster than C pigs, however similar to the findings of Experiment 1b, DL pigs were less efficient. In addition, P2 backfat depth was less in DL pigs, indicating they were leaner than C pigs, and though not reflected in total carcass composition, again there was an effect of housing on fat distribution. The move to an unfamiliar housing environment affected growth performance, reduced enzyme activity in backfat and the ratio of SFA in belly fat, suggesting these pigs had lower rates of lipogenesis. However in contrast to Experiment 1a, where lipogenesis was higher in older DL pigs compared to older C pigs, pigs finished in the DL housing had a trend for lower enzyme activity in belly fat (P=0.063), suggesting lower rates of lipogenesis, and higher plasma glycerol concentrations, suggesting a higher level of lipolysis compared to C-finished pigs. The carcass composition data (Experiment 2b) found that though there were no differences indicated by differences in P2 depth, there was a strong trend (P=0.057) for DL-finished pigs to have 2-6% less fat in the carcass as a result of significantly less fat in the shoulder (15% vs 17%) and belly (29% vs 33%) primals compared to C-finished pigs. The difference in belly primal composition was a reflection of the lower enzyme activities in belly fat and higher plasma glycerol concentrations in DL finished pigs. The results suggest that the type of housing during the finishing growth period has a greater impact on fat accretion and carcass composition than the type of housing during the grower period, or changing housing environment during growth. However, changing housing environment at 13 weeks of age affected growth, where there was a temporary reduction in daily LW gain, and therefore significantly lower (P¡Ü0.001) LW at slaughter (117 kg LW), compared to pigs that had remained in C or DL housing from wean-to-finish (123 kg LW). Moving pigs from DL to C housing to control carcass fat and improve growth performance compared to pigs grown wean-to-finish in DL housing, was not successful, and had a negative impact on performance and carcass quality by reducing growth efficiency and LW and increasing carcass fatness. The results also showed that contrary to the industry view that DL raised pigs are fatter, pigs in this experiment finished in DL housing had a lower fat:lean ratio in the carcass than pigs finished in the C system (P¡Ü0.05). The effects of straw on growth performance and carcass composition were evaluated in Experiment 3a and 3b by including straw in the grower and finisher diets (St+) and/or providing straw bedding (Bed+) to C-housed pigs. The experiment tested the hypothesis that the presence of straw alters the growth paths of pigs, affecting fat distribution in the carcass. Straw, as bedding and in the diet, affected pig growth paths and altered carcass fat distribution and, consistent with the findings for DL pigs in Experiments 1b and 2b, there was a trend for pigs with access to straw to have less fat in the belly (P=0.072). Elevated activity of key enzymes involved in lipogenesis, measured in Experiment 3a in belly fat and backfat from pigs fed the St+ diet, and a higher ratio of SFA in belly fat of pigs housed on concrete without straw bedding, suggested that in this experiment straw ingestion increased lipogenesis in belly fat and backfat of the growing pig, whilst straw bedding reduced lipogenesis in belly fat. Experiment 3b demonstrated an additive effect of straw on growth where average LW at slaughter for pigs without access to straw was significantly lower (110 kg), compared to pigs with access to one source of straw either via the diet or bedding (115 and 114 kg LW respectively), and pigs that had two sources of straw available (119 kg LW) (P¡Ü0.05). Although LW differed between treatments there were no differences in total carcass fat (P>0.10), yet there was an effect of straw on fat distribution. Pigs with access to straw had a lower ratio of fat and a higher ratio of lean tissue in the belly primal (P=0.072) compared to pigs that did not have straw. The effect of straw ingestion on lipogenesis and fat deposition may have occurred via the effects of dietary fibre (DF) on the dilution of dietary energy density. Pigs were able to compensate for the energy/nutrient dilution by increasing VFI and therefore growth was not affected, however fat acts as an insulator, and localised differences in fat distribution may have been related to increased heat production (HP) from the digestion of greater volumes of feed. In response, fat deposition may have been directed away from the belly location in order to facilitate heat loss. Floor type may have also affected fat distribution via differences in thermal conductivity. Straw has a lower thermal conductivity than concrete, hence pigs housed on concrete flooring may have a greater requirement for fat in the belly to reduce conductive heat loss. Results from Experiment 3a and 3b provided evidence that pigs housed on bedding consume straw in sufficient quantities. Pigs fed the straw diet had significantly higher concentrations of plasma acetate than pigs fed the control diet (P¡Ü0.001), and there was a trend for pigs housed on straw bedding to have higher levels than pigs without access to straw. An increase in plasma acetate can indicate increased microbial activity in gut, which occurs in response to higher levels of DF. In addition, pigs bedded on straw had higher gastrointestinal tract weights, which can also indicate higher levels of DF intake. Regression analyses of data across experiments showed that P2 backfat depth, the primary carcass composition prediction tool, accounted for less than 50% of the variation in percent carcass fat (R2=0.41). Furthermore, across experiments, P2 accounted for very little of the variability in percent belly fat (R2=0.01). These results highlight the inconsistency of P2 depth as a reliable indicator of carcass composition and the need for the development of additional criteria to be used in the selection of carcasses for specific markets as the composition of the belly primal was not indicated by the current carcass measurement system. From the results obtained in this thesis, it was proposed that: 1) The growth path of pigs is altered by the housing system in which they are reared and the more variable ambient temperature of the DL housing system would increase the energy requirement of young pigs for thermoregulation. As a consequence of the altered growth paths, fat metabolism differs for pigs raised in DL and C production systems. Lower rates of lipogenesis may occur in young DL pigs compared to C pigs and this can change as pigs grow, however fat mobilisation remains higher in DL pigs during growth. 2) Differences in the rate of lipogenesis, indicated by the biochemical measures, were generally not reflected in total carcass composition, however there were differences in carcass fat distribution where pigs raised in DL systems consistently had less fat in the belly primal. Rearing environment may provide an additional criterion when selecting carcasses for specific markets where variability in belly composition is an issue. 3) Pig raised in the DL environment are not always fatter than pigs housed in C facilities, and moving pigs from one housing environment to another during the growing-finishing period disrupts the growth path reducing growth performance and can increase carcass fatness. 4) Straw bedding, via ingestion and via its physical thermal properties, affects pig growth and fat distribution and may explain in-part the differences in pig growth performance and carcass quality found between C and DL housing systems.

No description available.

A candidate gene approach was used to identify single nucleotide polymorphisms (SNPs) and their associations with body fat deposition and carcass merit traits in beef cattle. In total, 37 SNPs from 9 candidate genes have been genotyped on 463 hybrid, 206 Angus and 187 Charolais steers for association analyses with 10 different fat deposition and carcass merit traits. In single SNP analyses, 28 SNPs of 9 genes have been found significantly (P<0.05) associated with different traits in the cattle populations. Gene-specific linkage disequilibrium assessment of SNPs revealed the existence of haplotype blocks within 4 genes. Haplotype analyses have identified 31 haplotypes of 6 genes having significant associations (P<0.05) with different fat deposition and carcass merit traits in the cattle populations. These findings will provide insight into the genetic mechanism regulating body fat deposition in beef cattle and will assist the beef industry to improve beef quality through marker assisted selection. / Animal Science

O objetivo doestudo foi estimar o crescimento dostecidos muscular e adiposo por ultrassonografia e verificar as possíveis diferenças entre grupos genéticos no crescimento e características produtivas de novilhas Angus e Brangus com idade inicial de oito meses, e novilhos Angus, Braford e Brangus com idade inicial de sete meses, recriados sobre pastagem. Para avaliação entre as raças de novilhas foramconsideradas as seguintes características: peso vivo (PV) área de olho de lombo (AOLUS), espessura de gordura subcutânea (EGSUS) e espessura de gordura na picanha (EGPUS), observação de cio e prenhez. As avaliaçõesdos novilhos foram realizadas utilizando-se as características, PV, AOLUS, EGSUS, EGPUS, peso de carcaça (PC), rendimento de carcaça (RC), peso de cortes primários (PCP) e rendimento de cortes primários (RCP). O peso vivo inicial (PVI) 224,37 kg das novilhas Angus não prenhas foi superior (p<0,05) a 219,30 kg das prenhas. A espessura de gordura subcutânea inicial (EGSIUS) em novilhas Angus prenhes 0,95 mm foi superior (p<0,05) a0,80 mm a das não prenhes. O PVI em novilhas Brangusnão prenhas 223,33 kg foi superior (p<0,05) a214,11 kg das prenhas. A espessura de gordura subcutânea final (EGSFUS) das novilhas Brangus prenhes 2,08 mm foi superior (p<0,05) a1,89 mm das não prenhes. Houve diferença (p<0,05) quanto a taxa de prenhez 88,22% das novilhas Angus e 73,91% das Brangus. O PVI 228,74 kg dos novilhos Angus foi superior (p<0,05) a195,92 kg dos Braford porém o PVI dos novilhos Brangus 220,26 kg não apresentou diferença entre médias. A área de olho de lombo inicial (AOLIUS) dos novilhos Angus 42,44 cm² foi superior (p<0,05) a 38,32 cm²dos Braford. Não houve diferença da AOLIUS40,69 cm² dos novilhos Brangus com os demais grupos genéticos. A EGSIUS 1,90 mm dos novilhos Angus e 2,20 mm dos Brangus não apresentaram diferença significativa, no entanto, as médias foram superiores (p<0,05) a 0,70 mm dos novilhos Braford. As características das carcaças dos novilhos coletadas ao abate não apresentaram diferença entre médias de peso e rendimento. Novilhas com maior espessura de gordura subcutânea final (EGSFUS) apresentaram maior número de animais com manifestação de 1º cio e prenhez. As variações ambientais ocorridas pelas estações do ano no sistema de produção, não influenciaram diferenças derendimento dos cortes primários das carcaças dos novilhos ao abate. / Theaim of this study was to estimate the growth of muscle and adipose tissues by ultrasound and check for any genetic differences between groups in growth and production characteristics of Angus and Brangus heifers with initial age of eight months and steers Angus, Brangus and Braford with initial age of seven months, recreated on pasture.For evaluation between breeds heifers were deemed the following characteristics, body weight (PV) rib eye area (AOLUS), backfat thickness (EGPUS) and fat thickness on the rump (EGPUS), observing estrus and pregnancy.The evaluation between breeds of steers was performed using the characteristics, PV, AOLUS, EGSUS, EGPUS, carcass weight (PC), carcass yield (RC), weight of primal cuts (PCP) and income primal cuts (RCP). Weight and characteristics evaluated by ultrasound showed no significant difference between breeds of Brangus and Angus heifers.In genetic group Angus initial body weight (PVI) of pregnant heifers 219.30 kg and not pregnant 224.37 kg was significantly different (p<0.05). The initial thickness of subcutaneous fat (EGSIUS) Angus heifers was significantly different (p <0.05) in animals pregnant 0.95 mm and non-pregnant 0.80 mm.In Brangus heifers the PVI was different (p<0.05) between heifers pregnant 214.11 kg and non-pregnant 223.33 kg. The final thickness of subcutaneous fat (EGSFUS) in Brangus heifers was significantly different (p<0.05) for pregnant animals 2.08 mm and non-pregnant1.89 mm.There were differences (p <0.05) as the pregnancy rate 82.22% of Angus heifers and 73.91% of Brangus. The PVI Angus steers 228.74 kg was higher (p<0.05) to the Braford steers 195.92 kg but Brangus steers 220.26 kg no differences between means of genetic groups.The initial ribeye area (AOLIUS) Angus steers 42.44 cm² was higher (p<0.05) of Braford steers 38.32 cm² with no difference of Brangus steers 40.69 cm² AOLIUS with other genetic groups.The EGSIUS Angus steers 1.90 mm and Brangus 2.20 mm showed no significant difference significantly, however the means were higher (p<0.05) of the steers Braford 0.70 mm.The characteristics of the carcasses of steers collected at slaughter showed no difference in mean weight and yield.Heifers with higher EGSUS showed higher participation in the number of animals with expression of 1st estrus and pregnancy. Environmental variations by the seasons in the production system did not influence differences in yield of the primary cuts of carcasses of steers for slaughter.

O objetivo doestudo foi estimar o crescimento dostecidos muscular e adiposo por ultrassonografia e verificar as possíveis diferenças entre grupos genéticos no crescimento e características produtivas de novilhas Angus e Brangus com idade inicial de oito meses, e novilhos Angus, Braford e Brangus com idade inicial de sete meses, recriados sobre pastagem. Para avaliação entre as raças de novilhas foramconsideradas as seguintes características: peso vivo (PV) área de olho de lombo (AOLUS), espessura de gordura subcutânea (EGSUS) e espessura de gordura na picanha (EGPUS), observação de cio e prenhez. As avaliaçõesdos novilhos foram realizadas utilizando-se as características, PV, AOLUS, EGSUS, EGPUS, peso de carcaça (PC), rendimento de carcaça (RC), peso de cortes primários (PCP) e rendimento de cortes primários (RCP). O peso vivo inicial (PVI) 224,37 kg das novilhas Angus não prenhas foi superior (p<0,05) a 219,30 kg das prenhas. A espessura de gordura subcutânea inicial (EGSIUS) em novilhas Angus prenhes 0,95 mm foi superior (p<0,05) a0,80 mm a das não prenhes. O PVI em novilhas Brangusnão prenhas 223,33 kg foi superior (p<0,05) a214,11 kg das prenhas. A espessura de gordura subcutânea final (EGSFUS) das novilhas Brangus prenhes 2,08 mm foi superior (p<0,05) a1,89 mm das não prenhes. Houve diferença (p<0,05) quanto a taxa de prenhez 88,22% das novilhas Angus e 73,91% das Brangus. O PVI 228,74 kg dos novilhos Angus foi superior (p<0,05) a195,92 kg dos Braford porém o PVI dos novilhos Brangus 220,26 kg não apresentou diferença entre médias. A área de olho de lombo inicial (AOLIUS) dos novilhos Angus 42,44 cm² foi superior (p<0,05) a 38,32 cm²dos Braford. Não houve diferença da AOLIUS40,69 cm² dos novilhos Brangus com os demais grupos genéticos. A EGSIUS 1,90 mm dos novilhos Angus e 2,20 mm dos Brangus não apresentaram diferença significativa, no entanto, as médias foram superiores (p<0,05) a 0,70 mm dos novilhos Braford. As características das carcaças dos novilhos coletadas ao abate não apresentaram diferença entre médias de peso e rendimento. Novilhas com maior espessura de gordura subcutânea final (EGSFUS) apresentaram maior número de animais com manifestação de 1º cio e prenhez. As variações ambientais ocorridas pelas estações do ano no sistema de produção, não influenciaram diferenças derendimento dos cortes primários das carcaças dos novilhos ao abate. / Theaim of this study was to estimate the growth of muscle and adipose tissues by ultrasound and check for any genetic differences between groups in growth and production characteristics of Angus and Brangus heifers with initial age of eight months and steers Angus, Brangus and Braford with initial age of seven months, recreated on pasture.For evaluation between breeds heifers were deemed the following characteristics, body weight (PV) rib eye area (AOLUS), backfat thickness (EGPUS) and fat thickness on the rump (EGPUS), observing estrus and pregnancy.The evaluation between breeds of steers was performed using the characteristics, PV, AOLUS, EGSUS, EGPUS, carcass weight (PC), carcass yield (RC), weight of primal cuts (PCP) and income primal cuts (RCP). Weight and characteristics evaluated by ultrasound showed no significant difference between breeds of Brangus and Angus heifers.In genetic group Angus initial body weight (PVI) of pregnant heifers 219.30 kg and not pregnant 224.37 kg was significantly different (p<0.05). The initial thickness of subcutaneous fat (EGSIUS) Angus heifers was significantly different (p <0.05) in animals pregnant 0.95 mm and non-pregnant 0.80 mm.In Brangus heifers the PVI was different (p<0.05) between heifers pregnant 214.11 kg and non-pregnant 223.33 kg. The final thickness of subcutaneous fat (EGSFUS) in Brangus heifers was significantly different (p<0.05) for pregnant animals 2.08 mm and non-pregnant1.89 mm.There were differences (p <0.05) as the pregnancy rate 82.22% of Angus heifers and 73.91% of Brangus. The PVI Angus steers 228.74 kg was higher (p<0.05) to the Braford steers 195.92 kg but Brangus steers 220.26 kg no differences between means of genetic groups.The initial ribeye area (AOLIUS) Angus steers 42.44 cm² was higher (p<0.05) of Braford steers 38.32 cm² with no difference of Brangus steers 40.69 cm² AOLIUS with other genetic groups.The EGSIUS Angus steers 1.90 mm and Brangus 2.20 mm showed no significant difference significantly, however the means were higher (p<0.05) of the steers Braford 0.70 mm.The characteristics of the carcasses of steers collected at slaughter showed no difference in mean weight and yield.Heifers with higher EGSUS showed higher participation in the number of animals with expression of 1st estrus and pregnancy. Environmental variations by the seasons in the production system did not influence differences in yield of the primary cuts of carcasses of steers for slaughter.

O objetivo doestudo foi estimar o crescimento dostecidos muscular e adiposo por ultrassonografia e verificar as possíveis diferenças entre grupos genéticos no crescimento e características produtivas de novilhas Angus e Brangus com idade inicial de oito meses, e novilhos Angus, Braford e Brangus com idade inicial de sete meses, recriados sobre pastagem. Para avaliação entre as raças de novilhas foramconsideradas as seguintes características: peso vivo (PV) área de olho de lombo (AOLUS), espessura de gordura subcutânea (EGSUS) e espessura de gordura na picanha (EGPUS), observação de cio e prenhez. As avaliaçõesdos novilhos foram realizadas utilizando-se as características, PV, AOLUS, EGSUS, EGPUS, peso de carcaça (PC), rendimento de carcaça (RC), peso de cortes primários (PCP) e rendimento de cortes primários (RCP). O peso vivo inicial (PVI) 224,37 kg das novilhas Angus não prenhas foi superior (p<0,05) a 219,30 kg das prenhas. A espessura de gordura subcutânea inicial (EGSIUS) em novilhas Angus prenhes 0,95 mm foi superior (p<0,05) a0,80 mm a das não prenhes. O PVI em novilhas Brangusnão prenhas 223,33 kg foi superior (p<0,05) a214,11 kg das prenhas. A espessura de gordura subcutânea final (EGSFUS) das novilhas Brangus prenhes 2,08 mm foi superior (p<0,05) a1,89 mm das não prenhes. Houve diferença (p<0,05) quanto a taxa de prenhez 88,22% das novilhas Angus e 73,91% das Brangus. O PVI 228,74 kg dos novilhos Angus foi superior (p<0,05) a195,92 kg dos Braford porém o PVI dos novilhos Brangus 220,26 kg não apresentou diferença entre médias. A área de olho de lombo inicial (AOLIUS) dos novilhos Angus 42,44 cm² foi superior (p<0,05) a 38,32 cm²dos Braford. Não houve diferença da AOLIUS40,69 cm² dos novilhos Brangus com os demais grupos genéticos. A EGSIUS 1,90 mm dos novilhos Angus e 2,20 mm dos Brangus não apresentaram diferença significativa, no entanto, as médias foram superiores (p<0,05) a 0,70 mm dos novilhos Braford. As características das carcaças dos novilhos coletadas ao abate não apresentaram diferença entre médias de peso e rendimento. Novilhas com maior espessura de gordura subcutânea final (EGSFUS) apresentaram maior número de animais com manifestação de 1º cio e prenhez. As variações ambientais ocorridas pelas estações do ano no sistema de produção, não influenciaram diferenças derendimento dos cortes primários das carcaças dos novilhos ao abate. / Theaim of this study was to estimate the growth of muscle and adipose tissues by ultrasound and check for any genetic differences between groups in growth and production characteristics of Angus and Brangus heifers with initial age of eight months and steers Angus, Brangus and Braford with initial age of seven months, recreated on pasture.For evaluation between breeds heifers were deemed the following characteristics, body weight (PV) rib eye area (AOLUS), backfat thickness (EGPUS) and fat thickness on the rump (EGPUS), observing estrus and pregnancy.The evaluation between breeds of steers was performed using the characteristics, PV, AOLUS, EGSUS, EGPUS, carcass weight (PC), carcass yield (RC), weight of primal cuts (PCP) and income primal cuts (RCP). Weight and characteristics evaluated by ultrasound showed no significant difference between breeds of Brangus and Angus heifers.In genetic group Angus initial body weight (PVI) of pregnant heifers 219.30 kg and not pregnant 224.37 kg was significantly different (p<0.05). The initial thickness of subcutaneous fat (EGSIUS) Angus heifers was significantly different (p <0.05) in animals pregnant 0.95 mm and non-pregnant 0.80 mm.In Brangus heifers the PVI was different (p<0.05) between heifers pregnant 214.11 kg and non-pregnant 223.33 kg. The final thickness of subcutaneous fat (EGSFUS) in Brangus heifers was significantly different (p<0.05) for pregnant animals 2.08 mm and non-pregnant1.89 mm.There were differences (p <0.05) as the pregnancy rate 82.22% of Angus heifers and 73.91% of Brangus. The PVI Angus steers 228.74 kg was higher (p<0.05) to the Braford steers 195.92 kg but Brangus steers 220.26 kg no differences between means of genetic groups.The initial ribeye area (AOLIUS) Angus steers 42.44 cm² was higher (p<0.05) of Braford steers 38.32 cm² with no difference of Brangus steers 40.69 cm² AOLIUS with other genetic groups.The EGSIUS Angus steers 1.90 mm and Brangus 2.20 mm showed no significant difference significantly, however the means were higher (p<0.05) of the steers Braford 0.70 mm.The characteristics of the carcasses of steers collected at slaughter showed no difference in mean weight and yield.Heifers with higher EGSUS showed higher participation in the number of animals with expression of 1st estrus and pregnancy. Environmental variations by the seasons in the production system did not influence differences in yield of the primary cuts of carcasses of steers for slaughter.

No description available.

Mais de 200 milhões de bovinos, em sua maioria animais da raça Nelore ou produtos de cruzamento com Nelore, compõem o rebanho do maior exportador de carne in natura do mundo, o Brasil. No entanto, o faturamento por kg de carne exportada poderia ser elevado se a qualidade do produto atendesse a mercados mais exigentes. A maciez da carne, a quantidade de gordura entremeada, a cobertura de gordura da carcaça e área do músculo Longissimus dorsi são fatores relevantes na procura por qualidade e padronização. A seleção genética assistida por marcadores moleculares poderá ter impacto positivo no melhoramento animal, principalmente em características de mensuração tardia e difícil para o pecuarista. Polimorfismos dos genes da tiroglobulina (TG), &micro;-calpaína (CAPN1) e calpastatina (CAST) são hoje marcadores disponíveis comercialmente, implicados na maciez e na marmorização da carne. Os genes do diacilglicerol O-aciltranferase (DGAT1) e da leptina (LEP) são candidatos pesquisados no desenvolvimento de marcadores relacionados à qualidade da carne. Leptina, tiroglobulina e diacilglicerol O-aciltranferase influenciam no metabolismo energético e na deposição de gordura. A calpastatina inibe a atividade proteolítica de &micro;-calpaína regulando o processo de amaciamento da carne no postmortem. Este trabalho avaliou as freqüências alélicas e genotípicas de polimorfismos dos genes CAPN1, CAST, LEP, TG e DGAT1 e relacionando os com qualidade de carne. Os polimorfismos escolhidos foram alterações de ponto (SNP) observadas pelo método da reação da polimerase em cadeia seguida de restrição enzimática (PCR-RFLP). Entre animais de raça Nelore e Canchim e cruzamentos de Nelore com Bos taurus (Rubia Gallega, Brangus, Pardo Suíço) foram genotipados 147 animais. Os mesmo foram abatidos com idade entre 15 e 19 meses, os animais foram avaliados quanto à maciez da carne (Warner-Bratzler Shear Force - SF - e Índice de Fragmentação Miofibrilar - MFI), à deposição de gordura (intramuscular e de cobertura) e à área de olho de lombo (AOL - Longissimus dorsi). O estudo de associação entre genótipos e fenótipos utilizou o procedimento General Linear Model do programa SAS e o teste F. Com o nível de significância de 5%, as freqüências alélicas de CAPN1/PsyI foram semelhantes entre os grupos genéticos estudados, mas as freqüências dos demais polimorfismos diferiram entre os grupos. Um achado inovador do trabalho foi a presença das duas variantes dos polimorfismos CAST/XmnI e DGAT1/CfrI na raça Nelore. Neste estudo o polimorfismo de TG/PsuI não foi informativo para raça Nelore, pois todos os animais apresentaram o mesmo genótipo (CC). Os resultados não mostraram associações significativas entre os polimorfismos e as análises da carne, exceto pelo efeito de CAST/XmnI cujo genótipo AA foi superior ao AB com relação ao MFI. Mais estudos semelhantes se fazem necessários para desenvolver marcadores adicionais e descartar os não informativos, adequando as novas ferramentas de seleção ao gado zebuíno brasileiro e respectivos cruzamentos. Os cinco genes estudados continuam como candidatos, apresentando diversos polimorfismos para serem pesquisados. No futuro, estudos com maior número de bovinos poderão validar o polimorfismo CAST/XmnI como indicador da maciez da carne. / Over 200 million bovines, mostly Nellore breed and its crosses, form the herd of the world biggest meat in natura exporter, Brazil. Even so, profit per kg of traded meat would improve if the product\'s quality achieved selective markets. Tenderness, marbling, backfat thickness and Longissimus dorsi área are traits to consider when pursuing meat quality and standardization. Marker assisted selection (MAS) can have positive impact over genetic improvement in livestock, mainly over traits such as the above mentioned, which are measured late in the production system and are hard to measure at the farm. Polymorphisms of thyroglobulin (TG), &micro;-calpain (CAPN1) and calpastatin (CAST) genes are commercially available markers assumed to predict meat tenderness and marbling. The genes encoding diacylglycerol O-acyltranferase (DGAT1) and leptin (LEP) are candidats researched to develop new markers related to meat quality. Thyroglobulin, Diacylglycerol O-acyltranferase and leptin influence energy metabolism and fat deposition. Calpastatin inhibits &micro;-calpain proteolysis regulating postmortem meat tenderization. This study evaluated allelic and genotype frequencies of polymorphisms located at CAPN1, CAST, LEP, TG and DGAT1 and tried to correlate the polymorphisms with meat quality. In each gene a single nucleotide polymorphism (SNP) was assessed by polymerize chain reaction followed by restriction enzyme digestion (PCR-RFLP). Including Nellore, Canchim and crosses of Nellore with Bos taurus breeds (Rubia Gallega, Brangus and Brown Swiss) a total of 147 animals were genotyped. Slaughterd aging 15 to 19 month, the animals were evaluated for meat tenderness (Warner-Bratzler Shear Force - SF - Myofibrillar fragmentation index - MFI), fat deposition (intramuscular and backfat) and rib eye area (REA - Longissimus dorsi). The assossiation study between genotypes and phenotypic traits used the linear regression model of SAS and the least square means were compared by the F test. Allelic frequencies of CAPN1/PsyI were similar in every genetic group of the study, but other polymorphisms allele frequencies differed between groups. A novel finding was the occurrence of both variants of CAST/XmnI and DGAT1/CfrI in the Nellore breed. In this study, the TG/PsuI polymorphism was uninformative for Nellore animals since only CC genotype was found. The results shwoed no significant assossiation between polymorphisms and the meat chacacteristics, except for the effect of CAST/XmnI over MFI, the AA genotype was superior to AB, predicting AA animals to have more tender meat. Further research is required to develop additional markers, disposal uninformative ones and to adequate molecular selecting tools to Brazilian zebu cattle and its crosses. The five genes here presented remain as candidates, in attendance to several polymorphisms yet to be carefully evaluated. Future studies, with bigger animal numbers, may validate CAST/XmnI as a meat tenderness indicator.