Best management practices are methods that have been determined to be the most effective and practical means of preventing or reducing pollution. Best Management Practices (BMPs) relating to surface water pollution abatement for North Dakota beef cow operations are of particular importance due to the importance of the agriculture industry in North Dakota. North Dakota has yet to address the use of voluntary BMPs to address potential surface water pollution regulations. Probit models were used to estimate the likelihood of North Dakota beef cow operators adopting specific production practices to reduce potential surface water pollution through the use of BMPs. The six BMPs discussed in this research include nutrient management, rotational grazing, filterstrjps, riparian buffers, streambank fencing, and streambank bridging/crossing. Number of beef cows on operation, education, awareness of cost share programs, contact with extension service, ownership structure, debt level, record keeping method, and pasture season usage were found to be significant in the likelihood of adopting a BMP.

The cattle industry is very competitive which is forcing cow-calf producers to strive for efficiency. Research has shown that as a cows mature weight increases, feed efficiency decreases, as well as reproductive efficiency and other production factors. The purpose of this paper is to (1) identify the economically optimum cow size when charging for grazing public lands on a true Animal Unit Equivalent (AUE) basis and (2) determine if the current practice of charging on a per head basis for grazing public lands has an effect on the optimal cow size. To simplify the complexity of this problem, three different resource bases common in the Intermountain West (resource base 1, time grazing = 100%; resource base 2, time grazing = 75%; and resource base 3 time grazing = 50%) were defined, as well as three different weights of cattle (small, medium and large). Grazing plans were created for each resource base and winter rations were balanced to ensure adequate nutrition and accurate budgeting. Linear programming was used to determine an optimal cow size for each resource base when charging on a per head basis and by a true AUE. When grazing on public land was charged on a true AUE basis, the small cows generated the highest net returns on all resources. Also, each resource base was able to maintain a larger number of the smaller cows than the medium or large cows under these conditions. When grazing on public lands was charge on a per head basis, as is typical, the large cow generated the greatest net returns on resource base 1 and 2. However, the small cow generated the greatest net return on resource base 3. These findings suggest that the current practice of charging for grazing public land on a per head basis does have an impact on cow size.

No description available.

This 2-yr experiment evaluated productivity of wild-type, endophyte-infected tall fescue (E+) and novel endophyte-infected tall fescue (NE) summer stockpiled (SS) pastures and the performance of fall-calving beef cow/calf pairs stocked on each cultivar. Fescue cultivars used were KY-31 and MaxQ for E+ and NE treatments, respectively. Pregnant Simmental x Angus cows (128 total, 64 each yr) were stratified by BW, BCS, and expected calving date and then allotted to 1 of 10 pasture groups within each yr (20 groups total, 10 per treatment). Forage growth was stockpiled from April until the initiation of strip-grazing on August 31 of 2017 and 2018. Cows grazed treatment pastures for 52 d from 23 ± 14 d prepartum to 29 ± 14 d postpartum, and calved on treatment pastures. Forage quadrats were clipped from the grazed and ungrazed portions of each pasture to determine weekly forage mass. Total ergot alkaloid (TEA) concentrations were analyzed for all pastures at the beginning of the experiment and every subsequent 2 wk for E+ tall fescue. Cow BW was recorded on 2 consecutive d and BCS determined at the start and end of the experiment. In yr 2, ultrasound 12th rib fat thickness (FT) was measured at the beginning and end of the treatment period Milk production was estimated using the weigh-suckle-weigh technique at 29 ± 14 d postpartum. Initial TEA concentrations for NE (Yr. 1 = 112 µg/kg; Yr. 2 = 632 µg/kg) were decreased (P ≤ 0.01) compared to E+ (Yr. 1 = 1831 µg/kg; Yr. 2 = 2903 µg/kg). TEA concentrations for E+ pastures did not differ (P < 0.23) by sample date. However, average TEA concentrations were greater for yr 2 than yr 1(P ≤ 0.01). Fescue cultivars were not different (P ≥ 0.06) in forage CP, Ash, Ether Extract, and grazed or ungrazed forage mass. However, differences were observed (P ≤ 0.02) for ADF, NDF, and TDN by fescue cultivar. Cow BW, BCS, and FT at the beginning and end of grazing were not different (P ≥ 0.41) by treatment. Milk production was greater (P < 0.01) for cows grazed on E+. Calving date, calf BW, calf ADG were not different (P ≥ 0.65) by treatment. Neither AI nor overall conception rates differed (P ≥ 0.23) between cultivars. Performance of fall-calving cows pre-exposed to E+ was not hindered when grazed on E+ relative to NE in a SS system. / Master of Science / Wild-type, endophyte-infected tall fescue (E+) is the predominant forage of use for producers within the southeastern United States. Endophyte-infected tall fescue gained notoriety due to its drought and pest resistance as well as climate adaptability. These advantages are the result of a symbiotic relationship with an endophytic fungus that has been shown to decrease in animal performance through the production of toxic ergot alkaloids. Development of improved fescue cultivars provided producers with an alternative forage, known as novel endophyte-infected tall fescue (NE), that maintains the agronomic advantages noted with E+ fescue without negative impacts on animal gain and reproductive performance. In adopting NE tall fescue, producers are faced with the financial challenge of renovating existing stands of E+ with NE fescue; leaving pastures unusable during times of normal grazing behavior. This constraint has highlighted the need to explore forage utilization and strategies that can extend the grazing period that do not require the significant cost of total renovation with NE. Fall stockpiled tall fescue has provided producers an option to extend grazing from late November through February when pasture growth ceases and hay supplementation is normally needed. However, a 60 to 90 d period between summer and fall stockpiled grazing leaves producers looking for an additional strategy to provide standing forage for their herds. Summer stockpiling (SS), is a novel grazing strategy that bridges summer and fall stockpiled grazing through proper accumulation of 25 % of total pasture to help extend producers grazing season. The objective of the current experiment is to evaluate both E+ and NE SS pastures and its effect on animal performance, forage availability, and nutritive value. Cow BW and BCS were measured at the initiation, conclusion, and before artificial insemination. Calf BW and ADG were assessed 48 h post-calving and at weaning. Ungrazed and grazed forage mass was collected weekly, while measurements of ADF, NDF, CP, TDN, ether extract, and ash were measured every 2 weeks. After a 52 d treatment period, forage mass was similar across both cultivars, with ADF, NDF, and TDN favoring E+ tall fescue. Additionally, animal performance across both E+ and NE pastures were similar, however increased milk production was observed for cows grazed on E+. This experiment helps shed light on the concept of strategic renovation. Strategic renovation can be best utilized by producers who are interested in maximizing pasture utilization through rotationally grazing E+ and NE tall fescue pastures. By following this renovation strategy, proper allocation of NE tall fescue during times of enhanced ergotism and E+ tall fescue during low thresholds will develop a more specific rotation thus decreasing renovation costs for producers when ergotism is lowest.

Master of Agribusiness / Department of Agricultural Economics / Rodney D. Jones / After remaining stable for several decades, corn price has recently had unprecedented price increases and volatility. United States Department of Agriculture (USDA) predicts an average corn price of $5.80 per bushel for 2008, which is 232% of its 28-year (1980-2007) average price of $2.50. The record increase in corn price was the result of increased starch-based ethanol production associated with increased energy costs, and other factors such as a declining value in the United States dollar, and increased global commodity demand. High corn prices have impacted the profitability of the livestock feeding industry. It was less clear how the record high corn prices would affect the cow-calf industry since corn is not a significant input for cow-calf enterprises. This study quantified the relationship between cow-calf profitability and corn price. Because feed costs for a cow-calf producer are among the highest variable costs for the operation, both grazing and non-grazing feed costs were estimated as a function of corn price. Models were estimated to determine if a relationship between corn price and Returns Over Variable Costs (ROVC) at the cow-calf level could be identified. Corn price from 1978-2007 explained none of the variability in grass grazing rental rate, however when the projected 2008 corn price was included in the analysis, corn price explained 10% of the variation in grass grazing rates. Year (linear time trend) and corn price from 1978-2008 explained 88% of historical grass grazing rental rate variability, 71% of alfalfa price variability, and 63% of other hay price variability in Kansas. These results suggest that the new corn market paradigm likely will increase the relationship between corn price and feed costs at the cow-calf level. Several models were evaluated using bulk diesel fuel price, feeder calf price, corn price, alfalfa price, other hay price, and grass grazing rental rate to estimate Kansas cow-calf producer ROVC. Models that included diesel fuel price, feeder calf price, grazing rent, and one of the harvested feeds (corn, alfalfa, or other hay) price explained 90-91% of the variability in ROVC. Models that included diesel fuel price, feeder calf price, and either grazing rent or corn price explained less of the variability in ROVC; using grazing rent explained 89% and using corn price explained 79%. Including grass grazing rental rate along with corn price, feeder calf price, and bulk diesel fuel price improved the model's ability to predict ROVC, explaining 91% of the variability. While cow-calf producers might use very little corn directly in their operations, this research shows that corn price is an important determinant of cow-calf production returns, and corn price can be used by producers to plan for future rising costs in order to maximize returns.

Thesis (MScAgric)--University Stellenbosch, 2001. / ENGLISH ABSTRACT: The aim of this study was to estimate genetic parameters as well as to evaluate the influence of some genetic factors on preweaning growth traits in a multi breed beef cattle population. These preweaning growth traits were birth weight (BW), weaning weight (WW) and average daily gain (ADG). Three aspects were addressed in this particular study; namely the Estimation of (co)variance components and genetic parameters, the effect of sire breeds and dam genotypes and the contribution of Charolais and Angus breeding levels on weaning traits in a multibreed beef cattle herd. Variance components and resulting genetic parameters of BW, WW and ADG in the population were estimated by Restricted Maximum Likelihood (REML) procedures. Four different unitrait and multitrait animal models were fitted ranging from a simple model with the animal direct effects as the only random effect to the model allowing for both genetic and permanent maternal environmental effects. The model that included directgenetic and permanent maternal environmental effects generally best described the data analysed. The simple model ignoring maternal effects most likely inflated direct heritability estimates. Direct heritability estimates were 0.11, 0.19, and 0.15 for BW, WW and ADG, respectively, fitting a multitrait model that comprised of both the genetic and maternal environmental effects. Under this comprehensive model, maternal heritabilties were low under both analyses, ranging from 0.02 to 0.10. Permanent maternal environmental effects were more important than maternal additive genetic effects for WW and ADG. Direct and maternal genetic correlations range from 0.42 to 0.44 for BW, -0.22 to -0.25 for WW and -0.17 to -0.23 for ADG, while the corresponding estimates ofunitrait analysis varied from 0.58 to 0.61 for BW, -0.43 to-0.53 for WW and -0.49 to -0.79 for ADG. The effect of Charolais and Hereford sires and dam breed genotypes on BW and WW in calves of Hereford, F I, two and three breed rotational as well as terminal crosses among the Charolais, Hereford, Angus and Bonsmara breeds were investigated. BW and WW of the Charolais sired calves were significantly (P<O.OOl) heavier than the Hereford sired calves. Angus dams produced calves of smaller (P<0.05) BW than those of purebred and crossbred dams. The majority of the crossbred dams were not significantly different in BW of calves. With regard to WW, with the exception of 3/4H1I4A, all crossbred dams were superior (P<0.05) to Angus and Hereford dams. Calves of crossbred dams were on the average 8% heavier at weaning than calves of purebred dams. Crossbred dams, with intermediate Charolais contribution tend to wean heavier calves. Data collected were also analysed to determine the optimum breeding levels of Charolais and Angus, fitting a unitrait animal model. Further, the estimated heritabilities were subsequently used to predict direct and maternal breeding values (Best linear unbiased predictions) for individual animals. Best linear unbiased estimates (BLUEs) were also calculated for the traits. BLUEs, direct and maternal breeding values per genetic group estimated were regressed on proportions of Charolais and Angus breeding, respectively. BLUEs of BW, WW and ADG increased with increasing the proportion of Charolais while they decreased with increasing Angus breeding levels. In general, maternal breeding values increased with increasing the proportions of both breeds. Direct breeding values of Charolais increased and reached maximum values at 35, 38, and 45% proportion of Charolais for BW, WW and ADG, respectively. No optimal Angus proportion was found within these specific environmental conditions. In this herd it may be suggested that increasing the proportion of Charolais to intermediate levels would tend to improve the performances of preweaning traits. / AFRIKAANSE OPSOMMING: Die doel van die studie was om genetiese parameters in 'n meerras vleisbeeskudde te beraam, sowel as om die invloed van sekere genetiese faktore te evalueer. Die voorspeense groei-eienskappe het geboortegewig (BW), speengewig (WW) en gemiddelde daaglikse toename (ADG) ingesluit. Drie aspekte is in dié betrokke studie ondersoek, naamlik; die beraming van (ko )variansiekomponente en genetiese parameters, die invloed van ras van vader en moedergenotipe en die invloed van Charolais en Angus bydrae op speeneienskappe in 'n meerras vleisbeeskudde. Variansiekomponente en afgeleide genetiese parameters vir BW, WW en ADG in die kudde is met behulp van die Beperkte Maksimum Waarskynlikheidsprosedure (REML) beraam. Vier verskillende enkel- en meereienskapmodelle is gepas, wat vanaf 'n eenvoudige model wat slegs die direkte effek as enigste toevallige effek, tot dié model waarin beide die genetiese en permanente mateme omgewingseffekte ingesluit is. Die model wat beide die direkte en permanente mateme effekte ingesluit het, het die data die beste gepas. Die eenvoudige model, wat die mateme effekte nie insluit nie, het in alle waarskynlikheid die direkte oorerflikhede oorberaam. Die direkte oorerflikheidsberamingsas onderskeidlik 0.11, 0.19 en 0.15 vir BW, WW en ADG met dié meereienskapmodel wat beide genetiese en mateme effekte ingesluit het. Met die omvattende model was die mateme oorerflikhede laag en het van 0.02 tot 0.10 gewissel. Die permanente mateme omgewingseffekte was belangriker as die direkte mateme effekte vir WW en ADG. Die genetiese korrelasies tussen direkte en mateme effekte het vir BW tussen 0.42 en 0.44, vir WW tussen -0.22 en -0.25 en vir ADG tussen -0.49 en -0.79 gewissel. Die invloed van Charolais en Hereford bulle en moederrasgenotipes op BW en WW van Hereford, F 1, twee- en drieras rotasie sowel as terminale kruisings tussen die Charolais, Hereford, Angus en Bonsmara is ondersoek. BW en WW van kalwers van Charolais bulle was betekenisvol (P<O.OOl) swaarder as kalwers van Hereford bulle. Angus koeie het kalwers met laer (P<0.05) BW as die van ander suiwer en kruisraskoeie geproduseer. Kalwers van die meerderheid kruisraskoeie het egter nie in BW verskil nie. Wat WW betref, maar met die uitsondering van %HYtA, was alle kruisraskoeie beter (P<0.05) as beide Angus en Hereford koeie. Kalwers van kruisraskoeie was gemiddeld 8 % swaarder met speen as kalwers van suiwerraskoeie. Kruisraskoeie met intermediêre vlakke van Charolaisbydrae het geneig om die swaarste kalwers te speen. Die data is verder ook geanaliseer om die optimum vlakke van Charolais en Angus, deur die passing van 'n enkeleienskap dieremodel, te bepaal. Die beraamde oorerflikhede is vervolgens gebruik om direkte en mateme teelwaardes (Beste liniêre onsydige voospellers ) vir individuele diere te voorspel. Beste liniêre onsydige beramings (BLUE's) is ook vir elke eienskap bereken. Die regressies van BLUE's, direkte en mateme teelwaardes per genetiese groep bereken, is vervolgens op proporsie Charolais en Angus bydraes onderskeidelik gepas. BLUE's vir BW, WW en ADG het met toename In Charolaisproporsie toegeneem, terwyl dit met toename in Angusbydrae afgeneem het. In die algemeen het mateme teelwaardes met toename in die bydrae van beide rasse toegeneem. Direkte teelwaardes van die Charolais het toegeneem en maksimum waardes by 35, 38 en 45 % proporsie Charolais vir onderskeidelik BW, WW en ADG bereik. Vir die Angus is geen optimum proporsie in dié spesifieke omgewing gevind nie. In dié kudde word intermediêre Charolais vlakke vir die verbetering van voorspeense eienskappe aanbeveel.

Resumo: Este estudo avaliou o efeito dos níveis de energia (NDT) e proteína bruta (PB) consumidos por vacas de corte durante a gestação sobre o peso dos fetos aos quatro (PF4) e oito meses (PF8) e dos bezerros ao nascimento (PN); sobre o peso pós-natal aos 60 (PV60), 100 (PV100), 180 (PV180) e 205 (PV205) dias de vida; sobre o peso, a idade, o ganho médio diário (GMD), a área de olho de lombo (AOL), o marmoreio e a espessura de gordura (EG) ao abate. Foi conduzida uma revisão sistemática da literatura e uma metanálise (MA) a partir de duas bases de dados eletrônicas (Scopus e Web of Science). A MA para efeitos randomizados foi realizada para cada resultado com as médias do grupo controle e tratado, conduzida com os níveis de NDT e PB em relação às exigências das vacas (NRC, 1996). Foram avaliadas 46 publicações, correspondentes a 50 estudos, 135 ensaios e 9.379 animais. Não houve efeito do consumo de PB e NDT pelas vacas sobre o PF4. Quando as vacas consumiram PB e NDT em níveis iguais às suas exigências, no primeiro (1TRI) e segundo trimestre (2TRI) da gestação, houve redução no PF8 (DM= 2,236kg; P<0,001). O PN reduziu nos bezerros filhos de vacas que consumiram PB igual ou acima das suas exigências no terceiro trimestre da gestação (3TRI) (DM= -2,954kg; P<0,001 e DM= -0,453kg; P=0,045, respectivamente) ou 140% das exigências de NDT (DM= -2,709; P = 0,001). Quando o consumo de NDT foi igual à recomendação do NRC (1996), observou-se aumento de 2,029kg no PN dos bezerros (P<0,001). O PV60 foi inferior quando as vacas consumiram PB (DM= -1,923kg; P<0,001) e NDT (DM= -1,676kg; P<0,001) acima de suas exigências no 3TRI. O PV205 foi 3,122kg inferior (P<0,001) quando as vacas consumiram até 120% de NDT no 2TRI e 3TRI. Os novilhos cujas mães consumiram PB e NDT acima de suas demandas, no 3TRI, foram abatidos 5,5 dias antes (P= 0,015) que os demais. O GMD, o marmoreio e a EG foram superiores em vacas que consumiram NDT e PB acima das suas exigências no 3TRI (P<0,05). Em síntese, os níveis de PB e NDT, consumidos pelas vacas, acima das recomendações do NRC, estão negativamente relacionados com o desenvolvimento dos fetos e com o PN, sendo que esse efeito permanece até os 205 dias de idade. Por outro lado, na fase de terminação o excesso de PB e NDT passa a contribuir com o GMD, o marmoreio e a EG da carcaça das progênies. / Abstract: This study evaluated the effect of total digestible nutrients (TDN) and crude protein (CP) levels, consumed by cows during gestation, on fetal and postnatal development and on carcass traits. We conducted a systematic review of the literature and a metanalysis (MA) on two electronic databases (Scopus and Web of Science). Inclusion criteria were complete studies using pregnant beef cows receiving different diets that analysed fetus weight at four (FW4) and eight months (FW8), and birth weight of calves (BW); postnatal weight at 60 days (PW60), 100 days (PW100), 180 days (PW180) and 205 days (PW205) of life; and on weight, age, mean daily gain (ADG), loin eye area (LEA), marbling and fat thickness (FT) at slaughter. Random effect MA were conducted for each indicator separately with the mean of control and treated group. The analysis was conducted with the TDN and CP levels in relation to cows’ requirements (NRC, 1996). We evaluated 46 publications, reporting 50 studies, 135 trials and 9,379 animals. The CP and TDN level consumed by pregnant cows showed no change on FW4. Cows that consumed CP and TDN in a level equal to their requirements, in the first (1TRI) and second trimester (2TRI) of gestation, showed a reduction in FW8 (DM= 2,236kg; P<0.001). The BW reduced in cows that consumed CP equal to or above their requirements in the third trimester of gestation (3TRI) (DM= -2.954kg, P<0.001 and DM= -0,453kg, P=0.045, respectively), or 140% of TDN requirements (DM= -2.709, P=0.001). The calves of cows that consumed TDN equal to NRC (1996) requirements, increased the BW in 2,029kg (P<0.001). The PW60 was lower when cows consumed CP (DM= -1.923kg; P<0.001) and TDN (DM= -1.676kg; P<0.001) above their requirements in the 3TRI. The PW205 was lower (DM= 3.12kg; P<0.001) when cows consumed 120% of TDN in the 2TRI and 3TRI. Steers whose mothers consumed CP and TDN above their requirements in the 3TRI were slaughtered 5.5 days earlier (P= 0.015) than the others. The ADG, marbling and FT were higher when cows consumed TDN and CP above the NRC (1996) requirements in the 3TRI (P<0.05). In summary, the CP and TDN levels, consumed by cows, above the NRC recommendations, are negatively associated to fetal development and birth calf weight, and this effect remains until 205 days of age. Alternatively, in the feeder phase, CP and TDN in excess contribute to average daily gain, marbling and fat thickness of the progeny.

Este trabalho propõe uma metodologia para auxiliar o empresário rural no momento de decidir qual a tecnologia menos arriscada para aumentar a taxa de prenhez em seu sistema de produção de bezerros. Para tanto, foram avaliadas as percepções de especialistas quanto a sete fatores a partir dos quais foi desenvolvida uma equação para calcular este risco. Tais parâmetros e suas definições foram apresentados em questionários aos 18 especialistas, selecionados por amostragem não probabilística. Neste documento foram listadas 32 tecnologias, avaliadas de acordo com os parâmetros conforme a escala Likert de cinco níveis. Foram utilizados os parâmetros relacionados diretamente ao risco das tecnologias, atribuindo-se um valor conforme a nota dos especialistas, de forma a ajusta-las conforme sua influência no risco, se positiva ou negativa. Não houve diferença significativa entre o risco calculado e o estimado pelos especialistas, além de ambos apresentarem alta correlação, validando esta metodologia. As tecnologias de insumo se apresentaram mais arriscadas, indicando custo, complexidade operacional e conhecimento técnico mais elevados do que as de processo. Da mesma forma, as tecnologias de manejo demonstraram menor risco em relação às nutricionais e reprodutivas, que não apresentaram diferença entre si. As tecnologias consideradas inovadoras foram mais arriscadas do que as consolidadas, apresentando todos os parâmetros mais elevados, com exceção da flexibilidade. Dessa forma, a metodologia desenvolvida foi capaz de determinar o risco das tecnologias, obtendo resultados semelhantes às percepções dos especialistas. / This study proposes a methodology to assist the farmers in deciding which technology is less risky to reduce the inefficiencies of their cow-calf production. Thus, were evaluated the perceptions of experts about seven factors predetermined from which were developed a formula to calculate this risk. These parameters and their definitions were reported in questionnaires to 18 experts, selected by nonprobability sampling. This document listed 32 technologies evaluated according to the parameters in the Likert scale of five levels. Were used the parameters directly related to the risk, assigning a value to the experts notes, in order to adjust these as their influence on the risk, whether positive or negative. There was no significant difference between the calculated and the estimated risks; they also had a high correlation, validating this methodology. The innovative technologies were more risky, indicating cost, operational complexity and technical knowledge higher than the process technologies. Likewise, the management technologies showed less risk than the nutritional and reproductive ones, which appear to have no difference among them. The innovative technologies were riskier than the consolidated ones, with all the standards higher, with the exception of flexibility. The methodology was able to determine the risk of technologies, obtaining similar results to the perceptions of the experts.

Resumo: Este estudo avaliou o efeito dos níveis de energia (NDT) e proteína bruta (PB) consumidos por vacas de corte durante a gestação sobre o peso dos fetos aos quatro (PF4) e oito meses (PF8) e dos bezerros ao nascimento (PN); sobre o peso pós-natal aos 60 (PV60), 100 (PV100), 180 (PV180) e 205 (PV205) dias de vida; sobre o peso, a idade, o ganho médio diário (GMD), a área de olho de lombo (AOL), o marmoreio e a espessura de gordura (EG) ao abate. Foi conduzida uma revisão sistemática da literatura e uma metanálise (MA) a partir de duas bases de dados eletrônicas (Scopus e Web of Science). A MA para efeitos randomizados foi realizada para cada resultado com as médias do grupo controle e tratado, conduzida com os níveis de NDT e PB em relação às exigências das vacas (NRC, 1996). Foram avaliadas 46 publicações, correspondentes a 50 estudos, 135 ensaios e 9.379 animais. Não houve efeito do consumo de PB e NDT pelas vacas sobre o PF4. Quando as vacas consumiram PB e NDT em níveis iguais às suas exigências, no primeiro (1TRI) e segundo trimestre (2TRI) da gestação, houve redução no PF8 (DM= 2,236kg; P<0,001). O PN reduziu nos bezerros filhos de vacas que consumiram PB igual ou acima das suas exigências no terceiro trimestre da gestação (3TRI) (DM= -2,954kg; P<0,001 e DM= -0,453kg; P=0,045, respectivamente) ou 140% das exigências de NDT (DM= -2,709; P = 0,001). Quando o consumo de NDT foi igual à recomendação do NRC (1996), observou-se aumento de 2,029kg no PN dos bezerros (P<0,001). O PV60 foi inferior quando as vacas consumiram PB (DM= -1,923kg; P<0,001) e NDT (DM= -1,676kg; P<0,001) acima de suas exigências no 3TRI. O PV205 foi 3,122kg inferior (P<0,001) quando as vacas consumiram até 120% de NDT no 2TRI e 3TRI. Os novilhos cujas mães consumiram PB e NDT acima de suas demandas, no 3TRI, foram abatidos 5,5 dias antes (P= 0,015) que os demais. O GMD, o marmoreio e a EG foram superiores em vacas que consumiram NDT e PB acima das suas exigências no 3TRI (P<0,05). Em síntese, os níveis de PB e NDT, consumidos pelas vacas, acima das recomendações do NRC, estão negativamente relacionados com o desenvolvimento dos fetos e com o PN, sendo que esse efeito permanece até os 205 dias de idade. Por outro lado, na fase de terminação o excesso de PB e NDT passa a contribuir com o GMD, o marmoreio e a EG da carcaça das progênies. / Abstract: This study evaluated the effect of total digestible nutrients (TDN) and crude protein (CP) levels, consumed by cows during gestation, on fetal and postnatal development and on carcass traits. We conducted a systematic review of the literature and a metanalysis (MA) on two electronic databases (Scopus and Web of Science). Inclusion criteria were complete studies using pregnant beef cows receiving different diets that analysed fetus weight at four (FW4) and eight months (FW8), and birth weight of calves (BW); postnatal weight at 60 days (PW60), 100 days (PW100), 180 days (PW180) and 205 days (PW205) of life; and on weight, age, mean daily gain (ADG), loin eye area (LEA), marbling and fat thickness (FT) at slaughter. Random effect MA were conducted for each indicator separately with the mean of control and treated group. The analysis was conducted with the TDN and CP levels in relation to cows’ requirements (NRC, 1996). We evaluated 46 publications, reporting 50 studies, 135 trials and 9,379 animals. The CP and TDN level consumed by pregnant cows showed no change on FW4. Cows that consumed CP and TDN in a level equal to their requirements, in the first (1TRI) and second trimester (2TRI) of gestation, showed a reduction in FW8 (DM= 2,236kg; P<0.001). The BW reduced in cows that consumed CP equal to or above their requirements in the third trimester of gestation (3TRI) (DM= -2.954kg, P<0.001 and DM= -0,453kg, P=0.045, respectively), or 140% of TDN requirements (DM= -2.709, P=0.001). The calves of cows that consumed TDN equal to NRC (1996) requirements, increased the BW in 2,029kg (P<0.001). The PW60 was lower when cows consumed CP (DM= -1.923kg; P<0.001) and TDN (DM= -1.676kg; P<0.001) above their requirements in the 3TRI. The PW205 was lower (DM= 3.12kg; P<0.001) when cows consumed 120% of TDN in the 2TRI and 3TRI. Steers whose mothers consumed CP and TDN above their requirements in the 3TRI were slaughtered 5.5 days earlier (P= 0.015) than the others. The ADG, marbling and FT were higher when cows consumed TDN and CP above the NRC (1996) requirements in the 3TRI (P<0.05). In summary, the CP and TDN levels, consumed by cows, above the NRC recommendations, are negatively associated to fetal development and birth calf weight, and this effect remains until 205 days of age. Alternatively, in the feeder phase, CP and TDN in excess contribute to average daily gain, marbling and fat thickness of the progeny.

Este trabalho propõe uma metodologia para auxiliar o empresário rural no momento de decidir qual a tecnologia menos arriscada para aumentar a taxa de prenhez em seu sistema de produção de bezerros. Para tanto, foram avaliadas as percepções de especialistas quanto a sete fatores a partir dos quais foi desenvolvida uma equação para calcular este risco. Tais parâmetros e suas definições foram apresentados em questionários aos 18 especialistas, selecionados por amostragem não probabilística. Neste documento foram listadas 32 tecnologias, avaliadas de acordo com os parâmetros conforme a escala Likert de cinco níveis. Foram utilizados os parâmetros relacionados diretamente ao risco das tecnologias, atribuindo-se um valor conforme a nota dos especialistas, de forma a ajusta-las conforme sua influência no risco, se positiva ou negativa. Não houve diferença significativa entre o risco calculado e o estimado pelos especialistas, além de ambos apresentarem alta correlação, validando esta metodologia. As tecnologias de insumo se apresentaram mais arriscadas, indicando custo, complexidade operacional e conhecimento técnico mais elevados do que as de processo. Da mesma forma, as tecnologias de manejo demonstraram menor risco em relação às nutricionais e reprodutivas, que não apresentaram diferença entre si. As tecnologias consideradas inovadoras foram mais arriscadas do que as consolidadas, apresentando todos os parâmetros mais elevados, com exceção da flexibilidade. Dessa forma, a metodologia desenvolvida foi capaz de determinar o risco das tecnologias, obtendo resultados semelhantes às percepções dos especialistas. / This study proposes a methodology to assist the farmers in deciding which technology is less risky to reduce the inefficiencies of their cow-calf production. Thus, were evaluated the perceptions of experts about seven factors predetermined from which were developed a formula to calculate this risk. These parameters and their definitions were reported in questionnaires to 18 experts, selected by nonprobability sampling. This document listed 32 technologies evaluated according to the parameters in the Likert scale of five levels. Were used the parameters directly related to the risk, assigning a value to the experts notes, in order to adjust these as their influence on the risk, whether positive or negative. There was no significant difference between the calculated and the estimated risks; they also had a high correlation, validating this methodology. The innovative technologies were more risky, indicating cost, operational complexity and technical knowledge higher than the process technologies. Likewise, the management technologies showed less risk than the nutritional and reproductive ones, which appear to have no difference among them. The innovative technologies were riskier than the consolidated ones, with all the standards higher, with the exception of flexibility. The methodology was able to determine the risk of technologies, obtaining similar results to the perceptions of the experts.