Effect of heat stress during the dry period on milk yield and reproductive performance of Holstein cows.

This study aimed to determine the influence of heat stress during the dry period on milk yield and reproductive performance of Holstein cows in a hot environment. Breeding and milk production records of cows, as well as meteorological data between 2017 and 2020 from a commercial dairy herd (n = 12,102 lactations), were used to determine the relationship between climatic conditions during the dry period (average of the temperature-humidity index (THI) at the beginning, middle, and end of the dry period) and reproductive efficiency and milk yield traits. THI was divided into < 70 (no heat stress), 70-80 (moderate heat stress), and > 80 (severe heat stress). First-service pregnancy rate of cows decreased (P < 0.01) with increasing hyperthermia during the dry period (9.5, 7.3, and 3.4% for THI < 70, 70-80, and > 80, respectively). All-service pregnancy rate was highest (P < 0.01) for cows not undergoing heat stress during the dry period (60.2%) and lowest (42.6%) for cows with severe heat stress during the dry period. Cows not experiencing heat stress during the dry period required a mean ± SD of 5.6 ± 3.8 services per pregnancy compared with 6.5 ± 3.6 (P < 0.01) for cows subjected to THI > 80 during the dry period. Cows not suffering heat stress during the dry period produced more (P < 0.01) 305-day milk (10,926 ± 1206 kg) than cows subjected to moderate (10,799 ± 1254 kg) or severe (10,691 ± 1297 kg) heat stress during the dry period. Total milk yield did not differ (P > 0.10) between cows not undergoing heat stress (13,337 ± 3346 kg) and cows subjected to severe heat stress during the dry period (13,911 ± 4018 kg). It was concluded that environmental management of dry cows during hot months is warranted to maximize reproductive performance and milk yield in the following lactation.

Genotoxicity studies of organically grown broccoli (Brassica oleracea var. italica) and its interactions with urethane, methyl methanesulfonate and 4-nitroquinoline-1-oxide genotoxicity in the wing spot test of Drosophila melanogaster.

Broccoli (Brassica oleracea var. italica) has been defined as a cancer preventive food. Nevertheless, broccoli contains potentially genotoxic compounds as well. We performed the wing spot test of Drosophila melanogaster in treatments with organically grown broccoli (OGB) and co-treatments with the promutagen urethane (URE), the direct alkylating agent methyl methanesulfonate (MMS) and the carcinogen 4-nitroquinoline-1-oxide (4-NQO) in the standard (ST) and high bioactivation (HB) crosses with inducible and high levels of cytochrome P450s (CYPs), respectively. Larvae of both crosses were chronically fed with OGB or fresh market broccoli (FMB) as a non-organically grown control, added with solvents or mutagens solutions. In both crosses, the OGB added with Tween-ethanol yielded the expected reduction in the genotoxicity spontaneous rate. OGB co-treatments did not affect the URE effect, MMS showed synergy and 4-NQO damage was modulated in both crosses. In contrast, FMB controls produced damage increase; co-treatments modulated URE genotoxicity, diminished MMS damage, and did not change the 4-NQO damage. The high dietary consumption of both types of broccoli and its protective effects in D. melanogaster are discussed.

Desempeño académico de universitarios en relación con ansiedad escolar y auto-evaluación / Academic performance, self-evaluation, and school anxiety among college students / Desempenho acadêmico dos universitários, respeito da ansiedade escolar e auto-avaliação

Los especialistas en comportamiento escolar han subrayado la necesidad de diseñar programas para reducir los efectos adversos que puede tener la ansiedad sobre el desempeño escolar a nivel universitario y atender oportunamente a los estudiantes en riesgo. El presente estudio explora la relación entre rendimiento académico y ansiedad escolar medida conductualmente, con el fin de corroborar si las relaciones entre esas variables y el sentido de las mismas, corresponde a las documentadas por estudios previos. Participaron 22 estudiantes de una universidad pública, sometidos a 25 evaluaciones académicas semestrales y a tres de auto-reporte, que produjeron respectivamente un promedio y un índice de estudio. La ansiedad escolar se midió mediante una tarea de discriminación basada en el paradigma de Stroop modificado. Los resultados señalan que los alumnos con los promedios más bajos presentaron los indicadores más elevados de ansiedad conductual. Adicionalmente, se encontró que los alumnos que de manera sistemática se ubicaron en el rango más bajo en su índice de estudio, mostraron mayor ansiedad escolar. El desasosiego emocional registrado mediante el monitoreo fisiológico se manifestó a partir de la presión sistólica, previa o posterior a la prueba conductual, según se tratara de los índices de estudio bajos, o del promedio bajo en los exámenes, respectivamente. Se concluye que el empleo de indicadores conductuales y fisiológicos corrobora las tendencias reportadas en la literatura sobre la relación inversa entre ansiedad y rendimiento académico, y la relación directa entre auto-concepto académico y promedio de calificaciones, en una situación en la que ex profeso se minimizó el efecto emocional de la exposición a exámenes académicos múltiples.

Behavioral researchers in the field of education have stressed the need for designing programs aimed to reduce adverse effects of anxiety on academic performance among high risk students. This study was designed to corroborate the relationship between academic performance and school anxiety reported in the literature, and to verify if the direction of this relationship is the same when behavioral indexes of school anxiety are employed. The study was conducted with 22 college students of a public university. They were subjected to 25 academic exams and three self rated measures which produced an average grade and a study index respectively. School anxiety was measured by means of a discrimination task based on a modified version of Stroop’s paradigm. Results showed that under-achievers produced the highest indicators of behavioral anxiety. Additionally, it was found that students who had been systematically located in the lower levels of the study index showed the highest levels of anxiety. Emotional arousal was registered by means of a systolic blood pressure measurement taken before or after the behavioral task depending on whether it was dealt with students who showed low-study indexes or low-average grades. The use of behavioral and physiological indexes of anxiety supports previous findings on the inverse relationship between anxiety and academic performance and the direct relationship between the academic self concept and school grades in a situation designed to minimize the emotional effect associated with the exposure to multiple exams.

Os especialistas no comportamento escolar têm destacado que é preciso desenhar programas para diminuir os efeitos contrários da ansiedade no desempenho estudantil universitário e atender oportunamente aos estudantes que correm o risco. Este estudo explora a relação entre rendimento escolar e ansiedade, medida comportamentalmente, para comprovar se as relações entre programas variáveis e o sentido das mesmas corresponde as documentadas nos estudos anteriores. Participaram 22 estudantes de uma universidade pública, submetidos a 25 avaliações acadêmicas semestrais e três de auto-reporte, que produziram, respectivamente, uma média e um índice de estudo. A ansiedade escolar foi medida mediante uma tarefa de discriminação, baseada no paradigma de Stroop alterado. Os achados mostram que os alunos com as médias mais baixas apresentaram os indicadores mais altos de ansiedade. Ademais, foi achado que os alunos situados sistematicamente nas posições mais baixas no índice de estudo mostraram maior ansiedade escolar. O desassossego emocional registrado mediante monitoramento fisiológico manifestou-se na pressão sistólica, antes e depois da prova comportamental, segundo trataram-se dos índices de estudo baixos ou da média baixa nos exames, respectivamente. É concluso que o emprego de indicadores comportamentais e fisiológicos corrobora as tendências reportadas na literatura sobre a relação inversa entre ansiedade e rendimento acadêmico, e a relação direita entre auto-conceito acadêmico e média de qualificações em uma situação em que, ex professo, foi minimizado o efeito emocional da exposição aos diversos exames acadêmicos.