How Divergence for Feed Efficiency Traits Affects Body Measurements and Metabolites in Blood and Ruminal Parameters on Pre-Weaning Dairy Heifers.

The objectives of this study were: (1) to evaluate feed efficiency indexes and their relationships with body measurements and blood and ruminal metabolites in the pre-weaning period; (2) to determine if such measurements can be used as feed-efficiency markers during the pre-weaning period. Holstein-Gyr heifer calves (n = 36), enrolled between 4 and 12 weeks of age, were classified into two residual feed intake (RFI) and residual body weight gain (RG) groups: high efficiency (HE; RFI, n = 10; and RG, n = 9), and low efficiency (LE; RFI, n = 10; and RG, n = 8). Calves were fed whole milk (6 L/day) and solid feed ad libitum. Body developments were measured weekly and feed intake (milk and solid feed) daily during the whole period. Blood samples were collected at 12 weeks of age and analyzed for glucose, insulin and ß-hydroxybutyrate (BHB). Samples of ruminal content were collected on the same day and analyzed for pH, NH3-N, and volatile fatty acids (VFA). Among the growth characteristics, only the initial hip width differed between the RFI groups, and withers height differed between the RG groups. Concentration of BHB was greater and glucose: insulin ratios tended to be greater in LE-RG animals. Butyric acid proportions were similar among RFI groups, but tended to be greater for HE-RG than for LE-RG. Overall, correlation coefficients between RFI or RG and blood, rumen, or morphometric markers were low. Thus, it is unlikely that measurements of metabolic indicators, per se, will be useful in the early identification of more efficient animals. Understanding the underlying physiological basis for improved feed efficiency in dairy heifers requires further investigation.

Control of Haematobia irritans in the Minas Gerais Semiarid / Controle de Haematobia irritans no Semiárido de Minas Gerais

Background: Beef cattle is considered to be one of the most important economic activities, however, it presents problems in the production chain such as the occurrence of parasites that reduce the growth, performance, productivity and may cause mortalities occasionally. The chemical control is the most used alternative to reduce ectoparasites. Nevertheless, inappropriate management of insecticides has contributed to the selection of population resistant to the products available on the market. This paper aimed to evaluate the practices of management and the application of insecticides used to control horn flies in farms of dairy cattle in the North of the state of Minas Gerais. Materials, Methods & Results: It was visited 62 rural properties, which produce milk. Semi-structured questionnaires were applied in order to obtain information on the characteristics of the properties (location, size and type of the cattle), on the knowledge about the epidemiology of the horn flies, and on the practices adopted to the control of those parasites. The practices adopted include the moment of application of the insecticides, frequency of the cattle treatment, used products, method of application, number of animals treated, and choice and substitution criteria of insecticides. The data collected were tabulated in contingency tables, and they were analyzed using the chi-square test [...](AU)

Control of Haematobia irritans in the Minas Gerais Semiarid / Controle de Haematobia irritans no Semiárido de Minas Gerais

Background: Beef cattle is considered to be one of the most important economic activities, however, it presents problems in the production chain such as the occurrence of parasites that reduce the growth, performance, productivity and may cause mortalities occasionally. The chemical control is the most used alternative to reduce ectoparasites. Nevertheless, inappropriate management of insecticides has contributed to the selection of population resistant to the products available on the market. This paper aimed to evaluate the practices of management and the application of insecticides used to control horn flies in farms of dairy cattle in the North of the state of Minas Gerais. Materials, Methods & Results: It was visited 62 rural properties, which produce milk. Semi-structured questionnaires were applied in order to obtain information on the characteristics of the properties (location, size and type of the cattle), on the knowledge about the epidemiology of the horn flies, and on the practices adopted to the control of those parasites. The practices adopted include the moment of application of the insecticides, frequency of the cattle treatment, used products, method of application, number of animals treated, and choice and substitution criteria of insecticides. The data collected were tabulated in contingency tables, and they were analyzed using the chi-square test [...]

Diagnosis of the control and efficacy of acaricides to bovine tick in the semiarid of North of Minas Gerais / Diagnóstico do controle e eficácia de acaricidas para o carrapato bovino no Semiárido do Norte de Minas Gerais

Background: Among the major ectoparasites of farm animals, Rhipicephalus microplus is the largest negative impact onthe economy of dairy farms. The spread of this mite is higher in tropical countries such as Brazil, and in cattle with predominance of taurine. The use of acaricides is most effectively used in their control, however, inadequate management hascontributed to the selection of resistant populations to products available in the market. Little is known about the controland resistance to these products for cattle in semi-arid conditions. Thus, we aimed to evaluate the management practicesused to control in dairy herds in semiarid region of northern Minas Gerais, checking the sensitivity of R. microplus todifferent acaricides.Materials, Methods & Results: A total of 62 properties located in nine municipalities in northern Minas Gerais were visited. Bocaiúva, Francisco Drumont, Francisco Sá, Icaraí de Minas, Juramento, Montes Claros, Pedras de Maria da Cruz,São Francisco and Varzelândia. The sensitivity of the ticks from cattle herds with high infestations was evaluated usingthe technique of biocarrapaticidograma. Semi-structured questionnaires were applied to characterize breeding systems,racial composition of the flock, season of greatest infestation, active ingredients used in tick control, forms of applicationof acaricides and the general management of the farm. The predominant type of exploitation was the dairy cattle representing 67.7% of the farms. The extensive system was predominant (58.06%) and crossbred...(AU)

Diagnosis of the control and efficacy of acaricides to bovine tick in the semiarid of North of Minas Gerais / Diagnóstico do controle e eficácia de acaricidas para o carrapato bovino no Semiárido do Norte de Minas Gerais

Background: Among the major ectoparasites of farm animals, Rhipicephalus microplus is the largest negative impact onthe economy of dairy farms. The spread of this mite is higher in tropical countries such as Brazil, and in cattle with predominance of taurine. The use of acaricides is most effectively used in their control, however, inadequate management hascontributed to the selection of resistant populations to products available in the market. Little is known about the controland resistance to these products for cattle in semi-arid conditions. Thus, we aimed to evaluate the management practicesused to control in dairy herds in semiarid region of northern Minas Gerais, checking the sensitivity of R. microplus todifferent acaricides.Materials, Methods & Results: A total of 62 properties located in nine municipalities in northern Minas Gerais were visited. Bocaiúva, Francisco Drumont, Francisco Sá, Icaraí de Minas, Juramento, Montes Claros, Pedras de Maria da Cruz,São Francisco and Varzelândia. The sensitivity of the ticks from cattle herds with high infestations was evaluated usingthe technique of biocarrapaticidograma. Semi-structured questionnaires were applied to characterize breeding systems,racial composition of the flock, season of greatest infestation, active ingredients used in tick control, forms of applicationof acaricides and the general management of the farm. The predominant type of exploitation was the dairy cattle representing 67.7% of the farms. The extensive system was predominant (58.06%) and crossbred...