RESUMO
A greater understanding of factors influencing fertility is essential to improve pregnancy rates and reduce the occurrence of embryonic mortality in beef herds. The objective of the current study was to evaluate retrospective data of pregnancy per artificial insemination (P/AI) and pregnancy loss in Nelore females subjected to timed-AI (TAI) in Brazil. Data from 40,104 TAI collected from six breeding seasons (2016-2022) were analyzed, and the effects of animal category (e.g., classification based on age and parity), farm, month of parturition, sire, sire breed (Nelore vs Angus), estrus expression at TAI, animal temperament, and body condition scores (BCS) were evaluated. P/AI and pregnancy loss were affected (P < 0.001) by animal category. There was also an effect of farm (P = 0.0013) on P/AI and pregnancy loss (P = 0.001), as P/AI ranged from 49.28% and 55.58% and pregnancy loss from 3.37% to 6.89% across the herds evaluated. Month of parturition also affected (P < 0.001) P/AI and was higher for cows that became pregnant at the beginning of the previous breeding season. Calmer animals, presenting lower velocity scores while exiting the chute following TAI, achieved higher P/AI (P < 0.001). Lower BCS at TAI was associated (P < 0.001) with increased pregnancy loss, and BCS gain following AI was associated (P < 0.001) with reduced rates of embryonic mortality. There was a major effect (P < 0.001) of sire on P/AI and pregnancy loss, as P/AI ranged from 11% to 79%, and embryonic mortality from 0% to 40% for the bulls used in the study, highlighting the importance of the sire fertility on overall pregnancy success. Results from the current study reinforce the idea that animal age and parity at the beginning of the breeding season, BCS at the onset of estrous synchronization, BCS gain following AI, estrus expression at TAI, sire, and month of parturition are important factors influencing P/AI and rates of embryonic mortality in beef herds.
RESUMO
Dois surtos de fotossensibilização foram observados em ovinos em pastagens de Brachiaria decumbens no Estado de Mato Grosso do Sul. O quadro clínico incluía edema e dermatite da face, orelhas e pálpebras, conjuntivite, descarga ocular, cegueira e aumento nos níveis séricos de ASTe GT. Alguns ovinos recuperaram-se e outros morreram em 3-7 dias. O fígado apresentou leve aumento de volume e consistência e coloração amarelo-esbranquiçada ou marrom-amarelada. Os ductos biliares e a vesícula biliar estavam dilatados. A principal alteração histológica foi a presença de cristais birrefringentes, eticamente ativos nos ductos biliares e no citoplasma de hepatócitos periportais. Necrose do epitélio dos ductos biliares, fibrose periportal com infiltração de células inflamatórias e proliferação de ductos biliares também foram observadas. Grupos de células grandes com núcleo excêntrico e citoplasma espumoso ocorriam nas regiões periportal e centrolobular. Numerosos grupos destas células também foram observadas no córtex e na medula dos linfonodos hepáticos. Não foram encontradas quantidades contáveis de esporos de Pithomyces chartarum nas amostras da pastagem onde estavam os ovinos; de 30 culturas de P. chartarum isoladas dessas amostras, apenas uma produziu esporidesmina. Conclui-se que a intoxicação foi causada pela ação tóxica de Brachiaria decumbens.
Two outbreaks of photosensitization were observed in sheep grazing Brachiaria decumbens in the state of Mato Grosso do Sul, Central Brazil. Clinical signs included swelling and dermatitis of the face, ears and eyelids, conjuntivitis. ocular discharge, blindness, and increased serum levels of AST e GT. Some sheep recoveredand others died within 3-7 days. The livers were sligthy enlarged and firm with white-yellowish or brown-yellowish discoloration. The bile ducts and gall bladder were sligthly enlarged. The main histological changes were the presence of optically active birefringent crystals in the bile ducts and within hepatocytes of periportal áreas. Necrosis of the bile duct epithelium, periportal fibrosis with infiltration of inflammatory cells and bile duct proliferation were also observed. Groups of large cells with excentric nuclei and foamy eosinofilic cytoplasm werepresent in the periportal and centrilobular áreas. Numerous groups of such cells were also observed in the cortex and medulla of the hepatic lymph nodes. No couhtable amounts of spores of Pithomyces chartarum were observed in the samples from the pasture where the seep grazed; from 30 cultures isolated from these samples, only one produced sporidesmin. It is concluded that the toxicosis was due the ingestion of Brachiaria decumbens.
