<p dir="ltr">Consistent intake and feeding behavior records collected on a per-cow basis are useful measures for optimization of feed efficiency, production, and ultimately, resource and economic sustainability of dairy operations. However, current methods for collection are often labor-intensive and impractical to maintain for both individual- and group-housed cows. Across the dairy industry, total mixed rations (TMR) are fed to promote balanced nutrient intake and satisfy evolving energy requirements. TMR intake is an extensively investigated phenotype of dairy cattle and is known to be highly variable due to both intrinsic and extrinsic determinants, which can include composition and palatability of offered TMR, intensity of environmental stressors, and biological aspects of the individual animal. Reductions in TMR intake negatively impact health and production; thus, industry demand has heightened for precise intake monitoring systems. Cyber-physical systems that employ cameras as a sensing device are proposed solutions to ambiguity in existing feeding strategies. Prior studies have demonstrated the efficacy of camera systems to monitor other phenotypes of dairy cattle including body condition, locomotion and gait, social interaction, and early detection of negative health events. In this study, an OAK-D PoE stereo vision camera system was employed to estimate volume of TMR and monitor feeding behavior in a dynamic barn environment. The system leveraged open-source Python software to measure relative depth in near real time and autonomously estimate the amount of TMR present in a feed bunk. Image data were processed to generate a point cloud for which volume of TMR was estimated at a rate of approximately 50 estimates/min. Two experiments were conducted in which mass, volume, and density of TMR, as well as feeding behavior (exclusive to Exp. 2) were manually recorded to be compared to volume estimates of TMR output by the camera system. In Exp. 1, diet type (high-density vs. low-density; HD and LD, respectively), lighting (10,000 Lm vs. existing barn lighting; on vs. off, respectively), and shape of offered TMR (undisturbed vs. simulated post-meal bout; no divot vs. divot, respectively) were assessed for impact on system accuracy across five intervals of known TMR volume. In Exp. 2, system volume estimates were evaluated over time when a cow was present and exhibiting normal feeding behavior. The system accurately estimated volume of TMR across evaluated conditions in Exp. 1, despite significance of the divot condition. As TMR disappeared over time in Exp. 2, system volume estimates decreased with a similar pattern. When the cow was removed and measured TMR volume was unchanged at 2 h collection timepoints in Exp. 2, system volume estimates also remained unchanged and consistent. Post-collection of replicates in Exp. 2, frequency and duration of meal bout events were estimated based on differences in volume when cows were eating. Estimated frequency and durations were similar to manually recorded data and indicated feasibility of behavioral monitoring as an opportunity for further system development. Prior studies have integrated machine learning approaches for refinement of camera monitoring systems and mitigation of reported environmental impact on accurate quantification of TMR volume. Further development of the current system through integration of machine learning applications will improve accuracy and industry applicability as an automated feed bunk management tool for collection of TMR intake and behavioral data on a per-cow basis.</p>

Embora possua o maior rebanho comercial do mundo, o Brasil está longe de liderar pesquisas relacionadas ao melhoramento genético de bovinos de corte para eficiência alimentar. Alguns países investiram em estudos para seleção de animais eficientes e identificação de marcadores moleculares associados a esta característica. A seleção genética de animais eficientes representaria economia de alimentos, reduziria o impacto ambiental e aumentaria a rentabilidade da atividade. Obviamente é um desafio identificar animais mais eficientes em um rebanho de 205 milhões de cabeças, pois, além da mensuração ser cara, os resultados são obtidos a longo prazo. As associações entre eficiência alimentar e desempenho de bovinos de corte são conhecidas, porém avaliações envolvendo os impactos da seleção para eficiência sobre composição corporal e qualidade de carne de novilhos Nelore ainda são incipientes. O objetivo neste trabalho foi estudar relações entre eficiência alimentar, composição corporal, características de carcaça e qualidade da carne em bovinos Nelore confinados. Foram confinados, em dois anos, 322 novilhos para avaliação de características de carcaça e qualidade de carne. Deste total, 159 foram confinados em baias individuais, dos quais 92 foram avaliados quanto ao consumo alimentar residual (CAR). Foram calculadas a eficiência alimentar, eficiência parcial de crescimento, taxa relativa de crescimento, índice de Kleiber e CAR. No abate foram obtidos dados de rendimento, comprimento e profundidade de carcaça, área de olho de lombo, espessura de gordura subcutânea, peso do coração, fígado, rins e gordura interna. Foram obtidas variáveis de qualidade da carne de amostras não maturadas do Longissimus dorsi (pH, força de cisalhamento, cor da carne e gordura, perdas por cocção, capacidade de retenção de água e extrato etéreo). Foram analisados os coeficientes de regressão linear entre as variáveis avaliadas e o CAR. Animais mais eficientes apresentaram consumo no mínimo 12% menor que os ineficientes (P <0,05). A variação do CAR em 1 kg MS/dia melhorou a eficiência alimentar em 7% para o mesmo ganho de peso. Houve relação positiva entre CAR e espessura de gordura subcutânea (P <0,05). Características de carcaça, peso do coração e do fígado, gordura interna e parâmetros de qualidade da carne não foram relacionados com CAR (P>0,05). No entanto, a diminuição do CAR reduziu a deposição de gordura subcutânea, avaliada por ultrassom (P<0,05). Consistente com essa redução, o conteúdo de gordura intramuscular diminuiu (P = 0,08), indicando uma relação positiva entre CAR e deposição de gordura. A energia retida, estimada pela composição corporal, foi reduzida em 0,4 Mcal / dia. Isto significa que mudanças na composição corporal foram capazes de explicar 36% das diferenças no consumo de alimentos entre animais eficientes e ineficientes quanto ao CAR. A margem de contribuição (lucro) foi positivamente relacionada ao CAR (P<0,05), mas foi muito melhor correlacionada com a eficiência alimentar e ganho de peso. A associação de CAR com rentabilidade foi tão boa quanto medição de área de olho de lombo. O CAR está associado com a composição do ganho dos animais e pouco correlacionado com a lucratividade em confinamento. Animais eficientes quanto ao CAR apresentaram redução na deposição de gordura subcutânea. / Although Brazil has the largest commercial beef cattle herd of the world, research on genetic improvement of beef cattle for feed efficiency is incipient. Some countries have invested in studies to identify feed efficient animals and to find molecular markers associated with this characteristic. Genetic selection of efficient animals can resulting lower costs, reduced environmental impact and increased profitability. Obviously identifying the most efficient animals is a challenge in a herd of 205 million head as measurement of feed intake is expensive. Associations between feed efficiency and performance of beef cattle are known, but possible impacts of selection for efficiency on body composition and meat quality of Nellore are still unknown. The objective of this study was to investigate relationships of feed efficiency with corporal composition, carcass characteristics and meat quality in Nellore steers finished in the feedlot. To evaluate carcass characteristics and meat quality, 322 steers were fed over a two year period. Of this total, 159 were housed in individual pens and 92 were evaluated for feed consumption. Feed efficiency, residual feed intake (RFI) partial efficiency of growth, relative growth rate and Kleiber´s index were calculated. Variables evaluated were: dressing, yield carcass linear measurements, loin eye area, fat thickness and weights of heart, liver, kidneys and internal fat. Longissimus dorsi pH, shear force, color of meat and fat, cooking losses, holding water capacity and ether extract were collected. The linear regression coefficients between these variables and RFI were calculated. Efficient and inefficient animals were separated as those that had 1 unit difference in RFI. The efficient animals intake were 12% lower than the inefficient animals (P<0.05). The variation of RFI by 1 kg DM/day improved feed conversion efficiency by 7%. There was a positive relationship between RFI and subcutaneous fat thickness (P<0.05) as well as with fat thickness deposition (P<0.05). Carcass characteristics, heart and liver weight, internal fat and meat quality parameters were not related to RFI (P>0.05). Consistent with the reduction in subcutaneous fat deposition there was a decrease in the fat content (P=0.08), indicating a positive relationship between RFI and fat deposition. The retained energy, estimated by the difference in body composition, was reduced by 0.4 Mcal/day in inefficient vs efficient animals. This means that the change in estimated body composition was able to explain 36% of the difference in feed intake between RFI efficient and RFI inefficient animals. Individual profit was calculated and it was positively associated to RFI (P<0.05). However, profit had much greater association with feed conversion efficiency (r=0.75) as well as with weight gain (r=0.53). The association of RFI with profitability was low (0.23) and about as good as the measurement of loin eye area (r=0.20). In this work RFI was associated with leaner composition of weight gain and was not well correlated with profitability in the feedlot.

Embora no passado a seleção para eficiência alimentar tenha sido relegada a um segundo plano pela indústria da carne bovina, hoje há um crescente interesse por estudos abordando eficiência alimentar de bovinos de corte e esta discussão norteou o primeiro capítulo desta tese. No segundo capítulo foram analisados dados de consumo de MS de 36 tourinhos do rebanho Nelore Seleção (NeS) e 36 do rebanho Nelore Controle (NeC) oriundos da Estação Experimental de Zootecnia de Sertãozinho. A média obtida para consumo alimentar residual (CAR) foi de 0,00±0,41 kg/dia, com valores mínimo e máximo de -0,73 e +0,95 kg/dia, confirmando que há uma satisfatória variabilidade para esta característica em animais Bos indicus. Tourinhos NeS apresentaram maiores pesos inicial e final e ganharam peso mais rapidamente que tourinhos NeC. Tourinhos NeS apresentaram consumos de MS superiores aos consumos de tourinhos NeC, quando expressos em kg/dia ou em g/kg PV0,75. Tourinhos NeC apresentaram índices de eficiência alimentar mais altos e estimativas de CAR mais baixas que tourinhos NeS. Enquanto que tourinhos NeS apresentaram valores de energia retida 11,7% superiores que tourinhos NeC, a produção de calor dos animais selecionados foi 17,9% maior. Tourinhos NeS apresentaram ainda maiores estimativas de exigência energética para mantença. As equações de predição de consumo de MS do NRC foram desenvolvidas com dados obtidos principalmente de bovinos europeus, implantados e alimentados com dietas de alta proporção de concentrado e com ionóforos. O terceiro capítulo estimou e validou uma equação de predição de consumo para zebuínos. Métodos de meta-análise foram aplicados em 17 experimentos com bovinos Nelore. Entre as 193 unidades experimentais, a concentração energética da dieta variou de 51,2 a 78,0% NDT. A equação sugerida para estimar o consumo alimentar de bovinos Bos indicus é: CMS (kg/d) = (PVj0,75 * (0,2039*ELm - 0,03844*ELm 2 - 0,07376))/ELm Bovinos Bos taurus apresentaram consumos de MS progressivamente mais altos que bovinos Bos indicus, quando a concentração da ELm foi superior a 1,4 Mcal/kg. Os resultados demonstraram que o comportamento ingestivo do Bos indicus em diferentes concentrações energéticas é incorretamente estimado pelas equações do NRC. No quarto capítulo foram desenvolvidas curvas de consumo de MS e eficiência alimentar no tempo para tourinhos em confinamento. O experimento foi realizado na Embrapa Pecuária Sudeste e utilizou 188 machos não-castrados da raça Nelore (NE) e cruzados ½Canchim + ½Nelore (CN), ½Angus + ½Nelore (AN) e ½Simental + ½Nelore (SN), distribuídos em três anos e 85 baias. Os animais foram distribuídos nas baias, de acordo com o grupo genético e tratamento experimental no período anterior ao confinamento. Machos NE apresentaram menor consumo de MS (kg/dia) do que machos cruzados AN, CN e SN. A presente análise não indicou menor eficiência dos machos NE em relação aos mestiços. Quanto ao efeito de tratamento anterior, o ganho de peso compensatório parcial e a melhor eficiência alimentar dos bovinos que não receberam concentrado no período anterior ao confinamento, reduziram as vantagens da suplementação em pastejo. Os efeitos de raça e sexo sobre características de desempenho em dois grandes confinamentos comerciais foram avaliados no quinto capítulo. Após impor restrições ao arquivo original, restaram 116.376 animais distribuídos em 608 lotes. Animais cruzados apresentaram taxas de ganho de peso e estimativas de consumo de MS mais altas que animais Nelore. Conseqüentemente, não foi observada diferença significativa na eficiência alimentar entre animais cruzados e zebuínos. O ganho de peso diário foi numericamente mais alto para os bovinos inteiros. Quando o consumo de MS foi expresso em kg/dia, lotes de animais inteiros apresentaram maiores consumos que lotes de animais castrados. Não foram observadas diferenças significativas entre bovinos inteiros e castrados para eficiência alimentar. As equações de predição de consumo de MS analisadas subestimaram os consumos reais observados, o que sugere uma grande heterogeneidade dos animais na entrada do confinamento e a ausência de fatores de ajuste para ganho compensatório. / Although selection for feed efficiency was withdrawn to a minor role by the beef industry in the past, nowadays there is a growing attention by studies dealing with feed efficiency traits in beef cattle and this subject was discussed in the first chapter. The second chapter analyzed dry matter (DM) intake data of 36 Nellore young bulls from the Selected Nellore (NeS) line and 36 from the Control Nellore (NeC), both from Experimental Station of Sertãozinho. Overall average for residual feed intake (RFI) was 0.00±0.41 kg/day, with minimum and maximum RFI estimates of -0.73 and +0.95 kg/day. These estimates confirm that there is enough variability for this new trait among Bos indicus animals. Selected Nellore young bulls were heavier at the beginning and at the end of the trial and they grown more rapidly than NeC young bulls. Selected Nellore young bulls showed larger DM intakes than NeC young bulls, when expressed on kg/day or g/kg mid-BW0.75. Control Nellore young bulls were more efficient and showed lower RFI estimates than NeS young bulls. While NeS young bulls showed retained energy estimates 11.7% greater than NeC cattle, NeS estimates for heat production were 17.9% larger. Lastly, NeS young bulls showed greater maintenance requirements than NeC young bulls. Current prediction equations for DM intake from NRC were mainly obtained from Bos taurus breeds, from cattle implanted with a growth-promoting implant and fed low forage diets, supplemented with ionophores. The third chapter developed and validated a DM intake prediction equation for Zebu cattle. Meta-analyses methods were applied to 17 experiments conducted with Nellore cattle. Among the 193 experimental units, dietary energy concentration ranged from 51.2 to 78.0% TDN. The suggested equation to predic feed intake by Bos indicus cattle is: DMI (kg/d) = (SBW0,75 * (0.2039*NEm - 0.03844*NEm 2 - 0.07376))/NEm Above 1.4 Mcal/kg the new equation predicted progressively lower intakes for Nellore than European genotypes. These results showed that the intake behaviour from Bos indicus cattle in a broad range of dietary NEm concentration is incorrectly predicted by the current NRC equations. The fourth chapter described the relationships of dry matter intake and feed efficiency to days on feed for young bulls in feedlots. The trial was conducted on Embrapa Pecuária Sudeste, and included records from 188 beef young bulls from four different genetic groups: purebred Nellore (NE), ½Canchim + ½Nellore (CN), ½Angus + ½Nellore (AN), and ½Simental + ½Nellore crossbreds (SN), distributed on three years and 85 pens. Animals were distributed on pens in a ramdomized block design by genetic group and previous experimental treatment. NE young bulls showed a lower DM intake (kg/day) than AN, CN and SN crossbreds bulls. The analysis did not show a lower feed efficiency for NE bulls compared with the feed efficiency estimated for the remaining genetic groups. Partial compensatory growth and better feed efficiency for the bulls that were not supplemented with a concentrate before being fully fed during the experimental period diminished the advantages of supplementation during the grazing period. The fifth chapter evaluated the effects of breed and gender on performance traits em two large commercial feedlots in the Brazilian Central Region. After editing the original data set, it remained 116,376 animals distributed on 608 pens. Crossbreds showed higher average daily gains and DM intakes than Nellore animals. Consequently, it was not observed significant differences on feed efficiency between crossbreds and Bos indicus cattle. Average daily gain was higher for the bulls. When DM intake was expressed as kg/day, bulls showed higher intakes than steers. There were not statistically differences between bulls and steers for the feed efficiency traits analyzed. The equations to predict DM feed intake clearly underestimated the observed intakes. This suggests a large heterogeneity among animals coming into a feedyard and the absence of adjusting factors for compensatory growth.

A manutenção das matrizes suínas fora da zona de conforto térmico compromete o seu desempenho, em especial no período lactacional, devido a redução no consumo voluntário de ração e na produção de leite. O estresse por calor é um desafio devido a dificuldade da espécie em dissipar calor, tendo como principal alternativa o uso da respiração para perder calor em situações de alta temperatura. Alternativas estruturais, como ventilação, gotejamento, resfriamento de piso e uso de processo evaporativo adiabáticos servem para amenizar as perdas produtivas. O objetivo do estudo foi analisar a influência de três sistemas de ambiência utilizando as variáveis temperatura e umidade relativa do ar, sobre os aspectos produtivos de fêmeas suínas e suas leitegadas. Foram utilizadas 244 fêmeas, em três tratamentos e três repetições. Ambiente climatizado - AC (n= 79), temperatura da sala de maternidade controlada por um sistema de resfriamento evaporativo adiabático, associado à ventilação negativa; Ar sobre as fêmeas - ASF (n= 82), saída individual de ar refrigerado sobre as fêmeas associado ao manejo de cortinas; Manejo de cortinas - MC (n= 83). Nas matrizes foi avaliado; o peso, a espessura de toucinho (ET), o escore corporal visual (ECV) pós-parto e ao desmame, e o intervalo desmame-estro (IDE) e o consumo médio diário de ração (CMR) na lactação. Dos leitões foi registrado o peso na uniformização, aos 14 dias e ao desmame. As mínimas e máximas diárias das variáveis temperatura e umidade relativa do ar (UR) foram mensuradas, bem como calculados as médias destas. As variáveis foram analisadas pelo procedimento GLM. As médias foram comparadas pelo teste de Tukey-Kramer, com nível de 5% de significância. A temperatura média observada no tratamento AC (23,0ºC) foi inferior e a UR (88,5%) superior quando comparada as dos demais. Para o CMR foi observada uma interação significativa entre os tratamentos e as repetições avaliadas. Na primeira repetição, o CMR foi maior no AC do que no MC. Na segunda repetição, não houve diferença entre os sistemas e, na terceira, os três sistemas diferiram entre si, com o maior CMR sendo observado no AC e o menor no MC. Apesar disso não foram observadas diferenças com relação a perda de peso lactacional e IDE. No entanto, o peso dos leitões ao desmame no AC (6164,2 g) foi semelhante aos demais, enquanto no ASF (6205,5 g) foi superior ao MC (5970,2 g). O tratamento ambiente climatizado foi efetivo em diminuir a temperatura ambiente, sendo uma alternativa para prover conforto térmico às fêmeas lactantes. No tratamento AC, o consumo de ração pelas fêmeas foi maior em uma das repetições, mas os leitões dos tratamentos AC e ASF tiveram desempenho semelhante e o primeiro não diferiu do MC, provavelmente por terem mobilizado mais energia para a manutenção da temperatura. / Maintaining sows outside the zone of thermal comfort compromises their performance, especially during lactation, mainly due to reductions in voluntary feed intake and milk production. The heat stress is a challenge because of the difficulty of the sow to dissipate heat with the main alternative use of breathing to lose heat in situations of high temperature. Structural alternatives, such as ventilation, drip, cooling and floor using adiabatic evaporative cooling to mitigate losses arising productive. This study analyzes the influence of three different cooling systems on the productivity of sows and their litters using the variables temperature and relative humidity. Two hundred and forty-four females were divided into three treatment and three replication groups: air-conditioned - AC (n = 79), with farrowing house temperature controlled by a system of adiabatic evaporative cooling combined with negative ventilation; snout cooler - SC (n = 82), with a cold air outlet directed towards females, combined with management of curtains; and management of curtains - MC (n = 83). The following variables were assessed for all sows: weight, backfat thickness (BFT), and visual body condition score (BCS), postpartum and at weaning, as well as weaning-to-estrus interval (WEI) and average daily feed intake (ADFI) during lactation. Piglet weight was recorded at cross-fostering, after 14 days, and at weaning. Minimum and maximum daily temperatures and relative humidity (RH) were measured and averaged. Variables were analyzed using the GLM procedure and means were compared using the Tukey-Kramer test at the 5% level of significance. Lower temperature averages were found for the AC treatment (23.0°C) and higher for RH (88.5%) than for others. There was significant interaction between treatment and evaluation periods for ADFI. In the first period, ADFI was higher in the AC group than in the MC one. In the second, there was no difference between the systems, while the three systems differed significantly in the third, with the largest ADFI found in AC and the lowest in MC. Yet there were no differences with respect to lactation weight loss and WEI. However, piglet weight at weaning in the AC group (6164.2g) was lower than in the SC (6205.5g) and higher than in the MC (5970.2g). The air-conditioned room treatment was effective in decreasing the temperature, and an alternative to provide thermal comfort to the lactating. In the air-conditioned room treatment, feed intake by females was higher in the replications, but the piglets from treatments air-conditioned room and snout cooler were similar and not different from the first management of curtains, probably because they had mobilized more energy to maintain temperature.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2018-03-29T19:44:04Z No. of bitstreams: 2 Dissertação - Adriano Santana Crozara - 2018.pdf: 1759192 bytes, checksum: 3a90741e5bd651adb8ff673e17b16c2a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2018-03-29T19:46:50Z (GMT) No. of bitstreams: 2 Dissertação - Adriano Santana Crozara - 2018.pdf: 1759192 bytes, checksum: 3a90741e5bd651adb8ff673e17b16c2a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-03-29T19:46:50Z (GMT). No. of bitstreams: 2 Dissertação - Adriano Santana Crozara - 2018.pdf: 1759192 bytes, checksum: 3a90741e5bd651adb8ff673e17b16c2a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The objective of this study was to verify the correlation of residual feed intake and gain and body weight variables obtained by traditional weighing methods, every 14 days and fasting animals, and daily weighing using an automated scale, in food efficiency tests, also verify the feasibility of reducing the duration of the test using the automated system, identifying the amount of minimum and adequate days for accurate measurement of residual feed intake, weight gain, dry matter intake and ratio conversion. A total of 28 Nellore and 16 Guzera cattle were used, not castrated and aged between 18 and 21 months. The test had a duration of 70 days, with an initial weighing, four intermediate and final weighing. The animals were also weighed daily by means of electronic scales coupled to drinking fountains. The variables measured to generate the food efficiency information (RC, FE and RFI) were: dry matter intake (DMI, kg/day); average daily gain (ADG, kg / day); live weight (LW, kg); subcutaneous fat thickness (mm) and, later, residual feed intake (RFI, kg/day). Cattle effects went through analysis of variance of repeated measures, to verify the need to analyze it separately. Averages test was performed for initial and final weight characteristics, ADG, RC and FE for the two scales. For RFI, originating from traditional and automated weighing information, was made a correlation between them, to verifying their magnitude. Significance of the slopes of the weight regression curves from the two scales was verified. Correlations were made between the weights from the traditional and automated scale, considering the six weighings by the traditional balance during the efficiency test and automated weighing disregarding the days of possible interference in weight due to fasting (one day before and one after the fast). To verify the possible reduction of time for food efficiency tests, using the automated weighing system, the variables of RFI, BW, ADG and DMI were grouped, obtaining an average value every four days. These data are representative for days 14, 18, 22, 26, 30, 34, 38, 42, 46, 50, 54, 58, 62 and 66 and 70. Thus, from the sequential information of the four characteristics, the Pearson and Spearman correlation coefficients were generated in relation to the final information (70th day) for the same characteristics and their variations. The moment when the correlation was significant at 0.1% and difference between variances below 1% for each characteristic was considered as adequate for the conclusion time for respective characteristic in food efficiency test. No differences were found between means of the two scales for initial and final weights, RC and FE, only for ADG. The Pearson and Spearman correlations of the RFI between the values obtained by weighing using the traditional and automated scale were, respectively, 0.75 and 0.76. The slopes of the lines for weights between the two scales were statistically similar. To reduce the test time, considering the reduction of the variances and the correlation coefficients, it is recommended that for the characteristics of ADG and RC it is possible to reduce to 58 days, for DMI 38 days and for RFI 34 days. The use of automated scale can serve as an option for RFI information in food efficiency tests. By conducting them using these it is possible to reduce the test period according to the desired characteristic, average gain and ratio conversion 58 days, for dry matter intake 38 days and for residual feed intake 34 days, obtaining reliable results. / Objetivou-se com o presente estudo verificar a correlação do consumo alimentar residual e variáveis de ganho e peso corporal obtidos por métodos de pesagem tradicional, a cada 14 dias e animais em jejum, e pesagem diária via balança automatizada, em testes de eficiência alimentar, também verificar a viabilidade de redução do tempo de duração do teste utilizando o sistema automatizado, identificando a quantidade de dias mínimos e adequados para mensuração acurada do consumo alimentar residual, ganho em peso, consumo de matéria seca e conversão alimentar. Foram utilizados 28 bovinos da raça Nelore e 16 da raça Guzerá, não castrados, com idade entre 18 e 21 meses. A prova teve duração de 70 dias, com uma pesagem inicial, quatro intermediárias e final. Os animais também foram pesados diariamente por meio de balanças eletrônicas acopladas aos bebedouros. As variáveis mensuradas para gerar as informação de eficiência alimentar (CA, EA e CAR) foram: consumo de matéria seca (CMS; kg/dia); ganho médio diário (GMD, kg/dia); peso vivo (PV; kg); espessura de gordura subcutânea (EG, mm) e, posteriormente, consumo alimentar residual (CAR; kg/dia). Efeitos de raça passaram por análise de variância de medidas repetidas, para a verificação da necessidade de analisa-la separadamente. Foi feito teste de médias para as características de peso inicial e final, GMD, CA e EA para as duas balanças. Para CAR, oriundo via informações da pesagem da balança tradicional e automatizada, foi feita a correlação entre eles, verificando sua magnitude. Foi verificada significância das inclinações das curvas de regressões de peso provindas das duas balanças. Foram feitas as correlações entre os pesos oriundos a partir da balança tradicional e automatizada, levadas em consideração as seis pesagens via balança tradicional no decorrer do teste de eficiência e as pesagens automatizadas inviabilizando os dias de possível interferência no peso devido ao jejum (um dia anterior e outro posterior ao jejum). Para verificação da possível redução de tempo para testes de eficiência alimentar, utilizando o sistema de pesagem automatizado, as variáveis de CAR, PV, GMD e CMS foram agrupadas obtendo valor médio a cada quatro dias. Estes dados sendo representativo para os dias 14, 18, 22, 26, 30, 34, 38, 42, 46, 50, 54, 58, 62 e 66 e 70. Assim, a partir das informações sequenciais das quatro características foram gerados os coeficientes de correlação de Pearson e Spearman em relação a informação final (70º dia) para as mesmas características e suas variações. O momento cuja a correlação foi significativa a 0,1% e diferença entre variâncias abaixo de 1% para cada característica considerou-se como adequado para o momento de conclusão para respectiva característica em teste de eficiência alimentar. Não foram encontradas diferenças entre médias das duas balanças para pesos inicial e final, CA e EA, apenas para GMD. As correlações de Pearson e Spearman do CAR entre os valores oriundos da pesagem via balança tradicional e automatizada foram, respectivamente, 0,75 e 0,76. As inclinações das retas para pesos entre as duas balanças foram estatisticamente semelhantes. Para redução do tempo de teste, levando em considerações a redução das variâncias e os coeficientes de correlação, recomenda-se que para as características de GMD e CA é possível uma redução para 58 dias, para CMS 38 dias e para CAR 34 dias. A utilização das balanças automatizadas pode servir como opção para informação do CAR em testes de eficiência alimentar. Ao conduzi-los utilizando estas é possível reduzir o período de teste de acordo com a característica desejada, ganho médio e conversão alimentar 58 dias, para consumo 38 dias e para consumo alimentar residual 34 dias, obtendo resultados confiáveis.

Embora no passado a seleção para eficiência alimentar tenha sido relegada a um segundo plano pela indústria da carne bovina, hoje há um crescente interesse por estudos abordando eficiência alimentar de bovinos de corte e esta discussão norteou o primeiro capítulo desta tese. No segundo capítulo foram analisados dados de consumo de MS de 36 tourinhos do rebanho Nelore Seleção (NeS) e 36 do rebanho Nelore Controle (NeC) oriundos da Estação Experimental de Zootecnia de Sertãozinho. A média obtida para consumo alimentar residual (CAR) foi de 0,00±0,41 kg/dia, com valores mínimo e máximo de –0,73 e +0,95 kg/dia, confirmando que há uma satisfatória variabilidade para esta característica em animais Bos indicus. Tourinhos NeS apresentaram maiores pesos inicial e final e ganharam peso mais rapidamente que tourinhos NeC. Tourinhos NeS apresentaram consumos de MS superiores aos consumos de tourinhos NeC, quando expressos em kg/dia ou em g/kg PV0,75. Tourinhos NeC apresentaram índices de eficiência alimentar mais altos e estimativas de CAR mais baixas que tourinhos NeS. Enquanto que tourinhos NeS apresentaram valores de energia retida 11,7% superiores que tourinhos NeC, a produção de calor dos animais selecionados foi 17,9% maior. Tourinhos NeS apresentaram ainda maiores estimativas de exigência energética para mantença. As equações de predição de consumo de MS do NRC foram desenvolvidas com dados obtidos principalmente de bovinos europeus, implantados e alimentados com dietas de alta proporção de concentrado e com ionóforos. O terceiro capítulo estimou e validou uma equação de predição de consumo para zebuínos. Métodos de meta-análise foram aplicados em 17 experimentos com bovinos Nelore. Entre as 193 unidades experimentais, a concentração energética da dieta variou de 51,2 a 78,0% NDT. A equação sugerida para estimar o consumo alimentar de bovinos Bos indicus é: CMS (kg/d) = (PVj0,75 * (0,2039*ELm – 0,03844*ELm 2 – 0,07376))/ELm Bovinos Bos taurus apresentaram consumos de MS progressivamente mais altos que bovinos Bos indicus, quando a concentração da ELm foi superior a 1,4 Mcal/kg. Os resultados demonstraram que o comportamento ingestivo do Bos indicus em diferentes concentrações energéticas é incorretamente estimado pelas equações do NRC. No quarto capítulo foram desenvolvidas curvas de consumo de MS e eficiência alimentar no tempo para tourinhos em confinamento. O experimento foi realizado na Embrapa Pecuária Sudeste e utilizou 188 machos não-castrados da raça Nelore (NE) e cruzados ½Canchim + ½Nelore (CN), ½Angus + ½Nelore (AN) e ½Simental + ½Nelore (SN), distribuídos em três anos e 85 baias. Os animais foram distribuídos nas baias, de acordo com o grupo genético e tratamento experimental no período anterior ao confinamento. Machos NE apresentaram menor consumo de MS (kg/dia) do que machos cruzados AN, CN e SN. A presente análise não indicou menor eficiência dos machos NE em relação aos mestiços. Quanto ao efeito de tratamento anterior, o ganho de peso compensatório parcial e a melhor eficiência alimentar dos bovinos que não receberam concentrado no período anterior ao confinamento, reduziram as vantagens da suplementação em pastejo. Os efeitos de raça e sexo sobre características de desempenho em dois grandes confinamentos comerciais foram avaliados no quinto capítulo. Após impor restrições ao arquivo original, restaram 116.376 animais distribuídos em 608 lotes. Animais cruzados apresentaram taxas de ganho de peso e estimativas de consumo de MS mais altas que animais Nelore. Conseqüentemente, não foi observada diferença significativa na eficiência alimentar entre animais cruzados e zebuínos. O ganho de peso diário foi numericamente mais alto para os bovinos inteiros. Quando o consumo de MS foi expresso em kg/dia, lotes de animais inteiros apresentaram maiores consumos que lotes de animais castrados. Não foram observadas diferenças significativas entre bovinos inteiros e castrados para eficiência alimentar. As equações de predição de consumo de MS analisadas subestimaram os consumos reais observados, o que sugere uma grande heterogeneidade dos animais na entrada do confinamento e a ausência de fatores de ajuste para ganho compensatório. / Although selection for feed efficiency was withdrawn to a minor role by the beef industry in the past, nowadays there is a growing attention by studies dealing with feed efficiency traits in beef cattle and this subject was discussed in the first chapter. The second chapter analyzed dry matter (DM) intake data of 36 Nellore young bulls from the Selected Nellore (NeS) line and 36 from the Control Nellore (NeC), both from Experimental Station of Sertãozinho. Overall average for residual feed intake (RFI) was 0.00±0.41 kg/day, with minimum and maximum RFI estimates of –0.73 and +0.95 kg/day. These estimates confirm that there is enough variability for this new trait among Bos indicus animals. Selected Nellore young bulls were heavier at the beginning and at the end of the trial and they grown more rapidly than NeC young bulls. Selected Nellore young bulls showed larger DM intakes than NeC young bulls, when expressed on kg/day or g/kg mid-BW0.75. Control Nellore young bulls were more efficient and showed lower RFI estimates than NeS young bulls. While NeS young bulls showed retained energy estimates 11.7% greater than NeC cattle, NeS estimates for heat production were 17.9% larger. Lastly, NeS young bulls showed greater maintenance requirements than NeC young bulls. Current prediction equations for DM intake from NRC were mainly obtained from Bos taurus breeds, from cattle implanted with a growth-promoting implant and fed low forage diets, supplemented with ionophores. The third chapter developed and validated a DM intake prediction equation for Zebu cattle. Meta-analyses methods were applied to 17 experiments conducted with Nellore cattle. Among the 193 experimental units, dietary energy concentration ranged from 51.2 to 78.0% TDN. The suggested equation to predic feed intake by Bos indicus cattle is: DMI (kg/d) = (SBW0,75 * (0.2039*NEm – 0.03844*NEm 2 – 0.07376))/NEm Above 1.4 Mcal/kg the new equation predicted progressively lower intakes for Nellore than European genotypes. These results showed that the intake behaviour from Bos indicus cattle in a broad range of dietary NEm concentration is incorrectly predicted by the current NRC equations. The fourth chapter described the relationships of dry matter intake and feed efficiency to days on feed for young bulls in feedlots. The trial was conducted on Embrapa Pecuária Sudeste, and included records from 188 beef young bulls from four different genetic groups: purebred Nellore (NE), ½Canchim + ½Nellore (CN), ½Angus + ½Nellore (AN), and ½Simental + ½Nellore crossbreds (SN), distributed on three years and 85 pens. Animals were distributed on pens in a ramdomized block design by genetic group and previous experimental treatment. NE young bulls showed a lower DM intake (kg/day) than AN, CN and SN crossbreds bulls. The analysis did not show a lower feed efficiency for NE bulls compared with the feed efficiency estimated for the remaining genetic groups. Partial compensatory growth and better feed efficiency for the bulls that were not supplemented with a concentrate before being fully fed during the experimental period diminished the advantages of supplementation during the grazing period. The fifth chapter evaluated the effects of breed and gender on performance traits em two large commercial feedlots in the Brazilian Central Region. After editing the original data set, it remained 116,376 animals distributed on 608 pens. Crossbreds showed higher average daily gains and DM intakes than Nellore animals. Consequently, it was not observed significant differences on feed efficiency between crossbreds and Bos indicus cattle. Average daily gain was higher for the bulls. When DM intake was expressed as kg/day, bulls showed higher intakes than steers. There were not statistically differences between bulls and steers for the feed efficiency traits analyzed. The equations to predict DM feed intake clearly underestimated the observed intakes. This suggests a large heterogeneity among animals coming into a feedyard and the absence of adjusting factors for compensatory growth.

Thesis (MSc. (Animal breeding and genetics )) --University of Limpopo, 2006 / The objective of this study was to estimate genetic parameters for weekly body weight of feed intake of individually fed beef bulls at centralized testing stations in South Africa using random regression models (RRM). The model for cumulative feed intake included the fixed linear regression on third order orthogonal Legendre polynomials of the actual days on test (7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77 and 84 day) for starting age group and contemporary group effects. Random regressions on third order orthogonal Legendre polynomials were included for the additive genetic effect of the animal and the additional random effect of weaning-herd-year (WHY) and on fourth order for the additional random permanent environmental effect of the animal. The model for body weights included the fixed linear regression on fourth order orthogonal Legendre polynomials of the actual days on test for starting age group and contemporary group effects. Random regressions on fourth order orthogonal Legendre polynomials were included for additive genetic effects and additional uncorrelated random effects of the WHY and the permanent environment. The residual effects for both traits were assumed to be independently distributed with heterogeneous variance for each measurement period. Variance ratios for additive genetic, permanent environment and WHY for cumulative feed intake at different days on test ranged from 0.07 to 0.10, 0.53 to 0.77 and 0.14 to 0.37, respectively. Variance ratios for additive genetic, permanent environment and WHY for weekly body weights at different test days ranged from 0.26 to 0.29, 0.37 to 0.43 and 0.26 to 0.34, respectively. Estimates of genetic correlation among the same trait (body weight or feed intake) measured at different test days were generally high (>0.80) for any give test pair. The WHY had a significant contribution in variation of performance of bulls on test, despite the 28-day adjustment period. RRM provided the opportunity to study changes in genetic variability within the studied traits over time. Random Regression Models could be used in the National Genetic Evaluation of beef bulls at central performance testing stations in South Africa.

Effects of a deoxynivalenol contaminated diet on feed intake and health status in horses.

Disputats. Universität Hohenheim, 2003. / Haves kun i elektronisk udg.

Die hypocalcämische Gebärparese, insbesondere die subklinische Hypocalcämie, die oft nicht erkannt wird und Ursache vieler sekundär auftretender Folgeerkrankungen ist, stellt in der intensiven Milchviehhaltung ein bedeutendes Problem dar. Inzwischen gibt es eine Reihe verschiedener Vorbeugungsstrategien, wobei der Einsatz von Zeolith A als Ca-Binder in der Ration gegen Ende der Trächtigkeit eine relativ neue Präventionsmöglichkeit darstellt. Da zu diesem Futterzusatzstoff noch wenige Untersuchungen, insbesondere auf Nebeneffekte vorliegen, war das Ziel dieser Studien, den Einfluss von Zeolith A in verschiedenen Dosierungen auf die Futteraufnahme, den Energiestoffwechsel, die Futterverdaulichkeit und den Ca-, Mg- und P-Stoffwechsel sowie in hohen Dosierungen auch auf den Spurenelement-stoffwechsel zu untersuchen. Des Weiteren sollte untersucht werden, wie sich Zeolith A im Verdauungstrakt hinsichtlich der Freisetzung von Al verhält. In einer ersten Studie an 46 Kühen (≥ 3. Laktation), die in zwei Gruppen unterteilt wurden, wurde Zeolith A in einer Dosierung von 90 g/kg Trockensubstanz (T) in den letzten 2 Wochen der Trächtigkeit bis zum Kalbetag in eine totale Mischration (TMR), welche zur freien Aufnahme vorgelegt wurde, eingemischt. Die Zeolith A-Zulage ante partum zeigte peripartal eine stabilisierende Wirkung auf die Ca-Konzentration im Serum (> 2 mmol/l). Der Rückgang der Häufigkeit der Hypocalcämie (< 2 mmol/l) am Tag der Kalbung lag bei 76 %. Die mittlere Mg-Konzentration im Serum war bei den Kontrolltieren am Tag der Kalbung und 1 Tag post partum signifikant höher im Vergleich zu den Tieren der Versuchsgruppe, lag aber in beiden Gruppen im physiologischen Bereich (0,75-1,30 mmol/l). Auf die Spurenelement-konzentrationen (Cu, Zn, Mn und Fe) im Plasma wurde kein Zeolith A-Effekt festgestellt. Allerdings zeigten die Zeolith A-supplementierten Kühe ante partum einen signifikanten Rückgang in der Futteraufnahme, welche in einer negativen Energiebilanz mit einem signifi-kanten Anstieg der freien Fettsäuren und des Beta-Hydroxybutyrats im Serum resultierte. Dieser Effekt hatte allerdings keine Auswirkung auf die Futteraufnahme post partum und auf die Milchleistung in den ersten 105 Tagen der Folgelaktation. Des weiteren war die mittlere Konzentration des anorganischen Phosphats (Pi) bereits 7 Tage nach Beginn der Zeolith A-Zulage signifikant niedriger im Vergleich zu den Tieren der Kontrollgruppe und lag bis zum Tag der Kalbung deutlich unter der unteren physiologischen Grenze von 1,25 mmol/l. Die zweite Studie war ein Dosis-Wirkungsversuch an 80 Milchkühen (1.-7. Laktation) mit verschiedenen Zeolith A-Dosierungen (0, 12, 23 bzw. 43 g Zeolith A/kg T TMR). Dazu wurden die Tiere ca. 4 Wochen ante partum in 4 Gruppen und für die Untersuchung des Mineralstoffwechsel noch in zwei Untergruppen (1. + 2. Laktation bzw. ≥ 3. Laktation) unterteilt. Die Tiere erhielten eine TMR ad libitum vorgelegt. In den letzten zwei Wochen erhielten die Tiere Zeolith A in die Ration eingemischt. Eine Einmischung von 43 g Zeolith A/kg T TMR zeigte auf den Ca-, Mg- und Pi-Stoffwechsel sowie auf die Futteraufnahme und den Energiestoffwechsel vergleichbare Effekte wie in der ersten Studie bei einer Zulage von 90 g/kg T TMR. Eine Zeolith A-Zulage von 23 g/kg T TMR bei einem Zeolith A/Ca-Verhältnis von 5,6:1 hatte ebenfalls noch einen stabilisierenden Effekt auf den peripartalen Ca-Stoffwechsel (> 2 mmol/l) bei Kühen ≥ 3. Laktation, jedoch ohne markanten Rückgang in der Futteraufnahme. In dieser Tiergruppe war ein Rückgang der Häufigkeit der Hypocalcämie um 71 % zu verzeichnen. Diese Tiere zeigten auch nur eine moderate Hypophosphatämie. Eine Zeolith A-Zulage von 12 g/kg T TMR zeigte dagegen keine Effekte. In einem Stoffwechselversuch an 8 doppelt fistulierten Milchkühen (Pansen und proximales Duodenum) wurde schließlich der Einfluss von Zeolith A auf verdauungsphysiologische Para-meter und den Mineralstoffwechsel, insbesondere des Phosphors im Verdauungstrakt, sowie auf die Freisetzung von Al aus dem Zeolithverband untersucht. Die Tiere erhielten Mais- und Grassilage und Kraftfutter. Es wurde 0, 10 bzw. 20 g Zeolith A/kg T über einen Zeitraum von 3 Wochen mit dem Kraftfutter verabreicht. Eine Zeolith A-Zulage führte zu einer signifikant reduzierten scheinbaren ruminalen Verdaulichkeit der T sowie der ruminal fermentierten organischen Substanz. Allerdings waren in der fäkalen Ausscheidung der Nährstoffe keine signifikanten Unterschiede zwischen den Fütterungsgruppen festzustellen. Es zeigte sich kein Effekt auf die Ca- und Mg-Verdauung. Dagegen korrelierte die Konzentration des löslichen P im Pansen signifikant negativ mit der mittleren Zeolith A-Aufnahme. Des Weiteren hatten die Kühe mit einer Zeolith A-Zulage von 20 g/kg T eine signifikant höhere fäkale Ausscheidung des Gesamtphosphors im Vergleich zu den Tieren der Kontrollgruppe. Die herabgesetzte Bio-verfügbarkeit von P resultierte in einer signifikant erniedrigten Pi-Konzentration im Serum. Gleichzeitig war eine signifikant erhöhte Konzentration des gelösten Al im Pansen und ein signifikant höherer Fluss des gelösten Al im Duodenum festgestellt worden was auf eine Instabilität des Zeolithverbands beruht. Da eine Zeolith A-Dosierung von 12 g/kg T keinen Effekt auf den Ca-Stoffwechsel und eine Dosierung 43 g/kg T unerwünschte Effekte zeigte kann anhand dieser Untersuchungen geschlussfolgert werden, dass eine Einmischung in einem Bereich von 20 bis 30 g Zeolith A/kg T TMR, was bei einer mittleren täglichen T-Aufnahme von 10 kg ca. 200 bis 300 g Zeolith A/Tier/Tag entspricht, bei einem Zeolith A/Ca-Verhältnis von 6 bis 10:1 in der Ration in den letzten 2 Wochen der Trächtigkeit zur Vorbeugung der peripartalen Hypocalcämie zu empfehlen ist, ohne dass negative Effekte auf die Tiergesundheit zu erwarten sind. / Parturient paresis is known to be a frequent problem in high-yielding dairy cows. Subclinical hypocalcemia around calving is especially of particular importance, because it often remains undetected and may cause secondary diseases. In practice different preventive methods have been established, whereas feeding of zeolite A (synthetic sodium-aluminium-silikate) as a calcium binder in the last two weeks of pregnancy is a new strategy to prevent parturient hypocalcemia. However, there exists only little information about side effects of zeolite addition. The aim of this study was to investigate the influence of zeolite A, in several doses, on feed intake, energy metabolism, nutrient digestibility, as well as on calcium (Ca), magnesium (Mg) and phosphorus (P) metabolism, and in high doses on trace element metabolism. Further, it was to investigate the mechanism of zeolite A in the gastrointestinal tract, focused on releasing aluminium (Al). In a first study with 46 cows (≥ 3rd lactation) zeolite A was tested in a dose of 90 g/kg dry matter (DM) in the last two weeks of pregnancy. Therefore the cows were divided in two groups (control and zeolite supplemented group). All cows were fed a total mixed ration (TMR) ad libitum. The supplementation of zeolite A had a stabilising effect on Ca concentration in serum (> 2 mmol/l) around calving. The reduction of the hypocalcemia incidence (< 2 mmol/l) was 76 % on the day of calving. The Mg-concentration in serum was significantly higher for the cows without zeolite A supplementation compared to the cows of the experimental group on the day of calving and on the day after calving. However, the mean serum Mg concentration stayed in the physiological range (0.75-1.30 mmol/l) for both groups. No significant effect of the zeolite A supplementation was observed on the mean plasma concentration of trace elements (copper, zinc, manganese, iron). However, the zeolite A supplementation led to a significantly reduced feed intake ante partum, which resulted in a negative energy balance. Furthermore, non esterified fatty acid and beta-hydroxybutyrate in serum were increased significantly. However, no significant differences were observed in feed intake post partum as well as in milk yield in the first 105 days in the subsequent lactation between the two groups. Furthermore, zeolite A supplementation decreased significantly the concentration of inorganic phosphate (Pi) in serum. Seven days after beginning zeolite A supplementation, on the day of calving, the mean Pi-concentration was considerably below the physiological limit of 1.25 mmol/l. In the second study, zeolite A was tested in several lower doses. Therefore 80 dairy cows (1st – 7th lactation) were divided into four groups in the last 4 weeks of pregnancy. Additionally, the cows of each group were divided in two subgroups (1st + 2nd lactation and ≥ 3rd lactation) to determine the influence of zeolite A on mineral metabolism. All animals were fed a TMR ad libitum. In the last two weeks the cows received a daily dose of 0, 12, 23 and 43 g zeolite A/kg DM. Zeolite A supplementation of 43 g/kg DM showed comparable effects on Ca, Mg, and Pi metabolism, as well as on feed intake and energy metabolism as in the first study. For older cows (> 3rd lactation), supplementation of 23 g zeolite A/kg DM, and a zeolite A-Ca ratio of 5.6:1 resulted also in a stabilising effect on Ca metabolism (> 2 mmol/l) around calving without significant reduction of feed intake. The incidence of hypocalcemia was reduced by 71 %. The cows showed only a moderate hypophosphatemia. A zeolite A supplementation of 12 g did not have any preventive effects. In a metabolic-study with eight double fistulated dairy cows (rumen and proximal duodenum), the influence of zeolite A supplementation on several physiological parameters of digestion and on mineral metabolism, especially P in the rumino-intestinal-tract, was determined. Further releasing of Al from the zeolite structure was investigated. The cows were fed a maize/grass-silage (60:40 % based on DM) and concentrate. Several doses of zeolite A (0, 10 and 20 g/kg DM) were added to the concentrate over a period of three weeks. Zeolite A supplementation resulted in a significantly reduced ruminal digestibility of dry matter (DM) and fermentation of organic matter. No effect was observed on faecal digestion of DM and OM. Digestion of Ca and Mg in the rumino-intestinal tract was not influenced by zeolite A supplementation. However, the concentration of soluble P in rumen fluid correlated negatively with the mean zeolite A intake. The faecal excretion of total P increased significantly for cows with a zeolite A dose of 20 g/kg DM compared to the control group. The reduced bioavailability of P resulted in a significantly decreased concentration of Pi in serum. The zeolite A supplemented cows further showed a significantly higher concentration of soluble Al in rumen fluid as well as a significantly higher flow of soluble Al at the duodenum, which is a consequence of an instability of the zeolite structure. According to these results it can be concluded that a daily amount of 20 to 30 g zeolite A/kg DM, which complies a daily amount of 200 to 300 g zeolite A/cow at a daily DM intake of 10 kg, with a zeolite-Ca ratio of 6–10 to 1, for two weeks ante partum seems to be an adequate dose for reducing subclinical hypocalcemia in older cows without negative side effects on animal health. At an expected daily mean DM intake of 10 kg it is a daily amount of 200 to 300 g zeolite A/cow. A zeolite dose of 12 g/kg DM did not have any effect on Ca metabolism, and a dose of 43g/kg DM showed negative side effects.