Mara Regina Bueno de Mattos Nascimento

Physiology, cell dynamics of small intestinal mucosa, and performance of broiler chickens under heat stress: a review

Summary High room temperature reduces production efficiency of broiler chickens. Different factors contribute to this situation: fast growth, physiological variations, and changes in the small intestine mucosa. This review aims to define the concept of heat stress and its effects on several physiological aspects related to the development of the small intestine mucosa and the performance of broiler chickens. Heat stress triggers a corticosteroid increase and a circulating triiodothyronine hormone (T3) reduction, increases respiratory frequency, which triggers respiratory alkalosis, diminishes food intake, and leads to changes in the cellular dynamics of the small intestine mucosa. These changes depend on animal genotype, intensity, and duration of the stressor. Acute heat stress leads to a reduction in enterocyte proliferation and also to a decrease in crypt depth, without affecting villus height or villus/crypt ratio. On the other hand, chronic stress diminishes villus height and jejunum weight. These changes affect the capacity of broilers to digest and absorb the nutrients required for maintenance and production. Keywords: corticosteroids, enterocyte proliferation, gastrointestinal tract, microscopic findings, morphological findings. Resumen Una alta temperatura ambiente disminuye la eficiencia de la produccion de pollos de engorde. Diversos factores contribuyen a esta situacion: crecimiento rapido, cambios fisiologicos, y anomalias de la mucosa del intestino delgado. El objetivo de la presente revision fue definir el concepto de estres calorico y sus efectos sobre algunos aspectos de la fisiologia, en el desarrollo de la mucosa del intestino delgado, y en el rendimiento de pollos de engorde. El estres calorico desencadena un aumento de los niveles de corticosteroides, reduccion de la hormona triyodotironina (T3) circulante, aumento en la frecuencia respiratoria que resulta en alcalosis respiratoria, disminuye la ingesta de alimentos y provoca cambios en la dinamica celular de la mucosa del intestino delgado. Estos cambios dependen del genotipo del animal y de la intensidad y duracion de la accion del factor estresante. El estres calorico agudo causa una disminucion en la proliferacion de enterocitos, reduccion de la profundidad de las criptas sin cambio en la altura de las vellosidades y en la relacion vellosidades/cripta. Ya el estres cronico disminuye la altura de las vellosidades y el peso del yeyuno. Estos cambios afectan la capacidad del pollo de engorde para digerir y absorber los nutrientes para su mantenimiento y produccion. Palabras clave: corticoesteroides, hallazgos microscopicos, hallazgos morfologicos, proliferacion de enterocitos, tracto gastrointestinal. Resumo A temperatura ambiente elevada diminui a eficiencia produtiva de frangos de corte. Diferentes fatores contribuem para esta situacao: crescimento rapido, mudancas fisiologicas e alteracoes na mucosa do intestino delgado. Nesta revisao, o objetivo foi definir o conceito de estresse pelo calor e seus efeitos sobre algunos aspectos da fisiologia, no desenvolvimento da mucosa do intestino delgado e o desempenho de frangos de corte. O estresse pelo calor desencadeia aumento nos niveis de corticosteroides e reducao do hormonio triiodotironina (T3) circulante, aumenta a frequencia respiratoria, resultando em alcalose respiratoria, diminui a ingestao de alimentos e desencadeia alteracoes na dinâmica celular da mucosa do intestino delgado. Essas alteracoes dependem do genotipo do animal e da intensidade e duracao da acao do agente estressor. O estresse pelo calor agudo promove diminuicao na proliferacao dos enterocitos, reducao na profundidade das criptas sem alteracao na altura das vilosidades e na relacao vilo/cripta. Ja o estresse cronico diminui a altura das vilosidades e peso do jejuno. Estas alteracoes afetam a capacidade do frango de corte de digerir e absorver nutrientes para sua manutencao e producao. Palavras chave: achados microscopicos, achados morfologicos, corticosteroide, proliferacao de enterocitos, trato gastrointestinal.

Suplementação com zinco e selênio em frangos de corte submetidos a estresse cíclico de calor

Frangos criados sob estresse de calor (EC) podem ter padrao antioxidante reduzido, e, a suplementacao de zinco e selenio podem amenizar este efeito. Assim sendo, o objetivo deste trabalho foi avaliar os efeitos da suplementacao de zinco e de selenio, nas formas orgânica e inorgânica, sobre o desempenho, a peroxidacao lipidica e o rendimento de carcaca em frangos submetidos a estresse ciclico de calor (EC). Para isso, foram utilizados 2.400 pintos machos de um dia de idade, criados em conforto termico ate o 14o dia, quando 1200 foram submetidos a EC. O delineamento foi o inteiramente casualizado em arranjo fatorial 2 x 5, sendo dois ambientes [conforto (C) e estresse de calor EC] e cinco niveis de suplementacao: [S1) racao controle; S2) S1 + 40 mg/kg de Zn inorgânico; S3) S1 + 40 mg/kg de Zn orgânico; S4) de S1 + 40 mg/kg de Zn inorgânico e 0,2 mg/kg de selenio orgânico, e S5) S1 + 40 mg/kg de Zn orgânico e 0,2 mg/kg de selenio orgânico], totalizando dez tratamentos, com oito repeticoes de 30 aves cada. Foram avaliados os niveis sanguineos de substâncias reativas ao acido tiobarbiturico, temperatura cloacal (TC), ganho de peso, consumo de racao, conversao alimentar, peso vivo e rendimento de carcaca e cortes. No 35° e no 42° dias, aves sob EC apresentaram elevacao de TC. Ganho de peso, conversao alimentar e carcaca eviscerada foram influenciados negativamente pelo calor. O ambiente e os niveis de suplemento nao alteraram o rendimento de peito com e sem osso, sobrecoxa e coxa, e asas. Nas condicoes ambientais e nutricionais, nao se identificou a necessidade de adicao suplementar de zinco orgânico e inorgânico e selenio orgânico.

INTEGRIDADE ÓSSEA DE TÍBIAS DE FRANGOS DE CORTE SUBMETIDOS AO ESTRESSE CÍCLICO DE CALOR

Macroscopic and microscopic changes in the epiphyseal region of the tibia were recorded in the 42nd day of life of broilers subjected to one-hour heat stress in different rearing phases. The treatments comprised both broilers reared under room temperature and humidity conditions from the 1st to the 42nd day of life (control) and broilers subjected to heat stress from the 16th to the 21st, from the 22nd to the 42nd, and from the 16th to the 42nd day of life. The adopted design was completely randomized with six replicates; 35 broilers were used in each experimental unit. Fragments from the epiphyseal region were extracted and sectioned lengthwise for macro and microscopic analyses. Data on tibia lesion scores were analyzed by Kruskal Wallis test at 5%. The one-hour cyclic heat stress did not change the morphologic integrity in the epiphyseal region of the tibia in the different treatments. Broilers subjected to one-hour cyclic heat stress did not develop lesions that suggested tibial dyschondroplasia, regardless of the rearing phase.

Most Appropriate Heat Stress Index for Half-blood Dairy Heifers

Background: Heat stress indexes integrate several variables of the thermal environment in a single figure and predict their impact on animal welfare and performance. The correct interpretation of these indexes is of help in the choice of more adequate measures to attenuate the stress caused by the heat. Therefore, the aim of this research is to examine some of the heat stress indexes mentioned in the literature and to decide which ones best reflect the potential impact of meteorological conditions on the thermal homeostasis of half-blood dairy heifers bred in Uberlândia, Triângulo Mineiro area, Minas Gerais, Brazil. Materials, Methods & Results: Eight half-blood dairy heifers were exposed to direct sunlight from 9 h to 13 h in the months of November and December of 2016, and also January and February of 2017, 5 days per month on average, in Uberlândia, MG, Brazil. After this challenge, the respiratory rate and the rectal temperature were measured. Simultaneously to the collection of physiological variables, the temperatures of dry bulb and wet bulb, as well as that of black globe, were quantified, as was the wind speed. Afterwards, the solar radiation, the relative humidity, the mean radiant temperature and some heat stress indexes were calculated, the latter being Temperature-Humidity Index, Black Globe-Humidity Index, Equivalent Temperature Index, Environmental Stress Index, Respiratory Rate Index, Thermal Load Index, Environmental Specification Index, Thermal Comfort Index for Dairy Cattle, Comprehensive Climate Index and Cattle Heat Stress Index. These indexes were, then, correlated with the physiological variables. The averages of room temperature, black globe temperature, solar radiation, wind speed, radiant temperature and relative humidity were, respectively, 29.96°C, 41.73°C, 831.02 W/m2, 0.11 m/s-1, 318.14 K and 50.51%. Rectal temperature averaged 38.8oC while respiratory rate averaged 41.97 breaths per minute-1. Correlating the 10 heat stress indexes with these two physiological variables, it was verified that the highest values, with a confidence of 95%, were demonstrated by the Equivalent Temperature Index (0.200 and 0.317, respectively), followed by the Cattle Heat Stress Index (0.186 and 0.314, respectively). Discussion: Room temperature was within the thermoneutral zone for half-blood dairy cattle. Nevertheless, the mean radiant temperature and the black globe temperature were higher, due to intense solar radiation. Wind speed was not very expressive and relative humidity was close to what was required. The average values of rectal temperature and respiratory rate were normal, which indicated the heifers are adapted to the thermal environment. Regarding the heat stress indexes, the Equivalent Temperature Index was recommended, as it presented the highest amount of meaningful correlations with the physiological variables, followed by the Cattle Heat Stress Index and the Environmental Stress Index. The average value of the Equivalent Temperature Index remained in the “caution” category, according to the literature’s two existing scales for interpretation of said index’s results, indicating the occurrence of stress by heat, albeit not severe. In conclusion, the Equivalent Temperature Index is considered the most appropriate heat stress index for evaluating a heat stress situation in half-blood dairy heifers bred in Uberlândia, Triângulo Mineiro, followed by the Cattle Heat Stress Index and the Environmental Stress Index.

Análise descritiva de algumas características reprodutivas de um rebanho bovino leiteiro mestiço no Município de Coromandel-MG

We determined some reproductive characteristics of a dairy cattle herd Figueredo mestizo farm in the town of Coromandel, Minas Gerais, Brazil. We used the SAS program in order to carry out the descriptive study of the gestation period (GP), calving interval (CI) and days open (DO) in crossbred dairy cows. The GP averaged 273.57 days (9.11 months) with a standard deviation of 5.47 days (0.18 months), being the most frequent value of 271 days (9.06 months), with a coefficient of variation of 0, 02% in 111 observed data. The mean CI was 470.75 (15.69 months) with a standard deviation of 159.76 days (5.32 months) being the most frequent value of 385 days (12.83 months), with a coefficient of variation of 0, 34% in 75 notes processed. DO The average was 197.54 days (6.58 months) with a standard deviation of 163.92 days (5.44 months), being the most frequent value of 60 days (2 months), with a coefficient of variation of 0.83% in 102 records processed. The calving interval and days open showed up the dairy farm is considered appropriate to efficiently and economically.

Estratégias para amenizar os efeitos do estresse por calor em matrizes suínas

The reproductive processes in swine is of fundamental importance in the economic performance of the activity. It is known that not enough just good nutritional standards and best management practices on the roster, but also achieve reproductive goals. The present study attempts to report appropriate bioclimatic practices to minimize the inconvenience caused by heat stress in sows. Among the factors that could cause reproductive disorders are highlighted changes in temperature, relative humidity and ventilation. The high ambient temperatures, which occur at certain times of the year, let the pigs out of their comfort zone heat, and may cause disorders in the reproductive performance. The adaptation of the facilities, taking into account the location, solar orientation, ceilings, roofing materials, trees, shading and natural ventilation, and practices such as fogging, ventilation, drip, cooling and floor using evaporative adiabatic processes are alternatives to minimize productive losses. Considering the importance of the sow in pig production process, and dependence of environmental and heat factors, it is necessary to better SILVA, M.C.A. et al. Estratégias para amenizar os efeitos do estresse por calor em matrizes suínas. PUBVET, Londrina, V. 7, N. 9, Ed. 232, Art. 1532, Maio, 2013. planning and monitoring the bioclimatic practices. The artificial factors should be a complement to the naturals, since the sows depends of these ways to express their genetic potential.

Níveis de hormônios tireoideanos circulantes, desempenho e qualidade de carcaça e carne de suínos em crescimento e terminação

The objective of this study was to compare serum concentrations of the hormones triiodothyronine (T3) and thyroxine (T4) in pigs on commercial line beginning and end of growing-finishing phase, correlating them with productive performance and quality characteristics of carcass and meat. Blood samples were collected from 48 animals at the beginning and end of growing-finishing phase by puncturing the jugular vein, around the same time (08:00 to 10:00a.m.). Measurements of serum thyroid hormones were made by enzyme-immunoassay. It was evaluated the performance and quality of carcass and meat. At the beginning and end of the housing, serum T3 concentrations were 1.85 and 1.32nmol L-1, respectively, and T4 of 100.33 and 86.53nmol L-1, respectively. There was negative correlation between T3 and low-end and average daily weight gain, final weight and backfat thickness. Inicial T4 was moderately and moderately negatively correlated with initial weight. The values of T3 and T4 in pigs early in the growing-finishing phase are larger than in termination. The thyroid hormones are associated with the initial and final weight, backfat thickness at the last lumbar, pH45min and pH24h of growing-finishing pigs.