Heat stress on breeding value prediction for milk yield and composition of a Brazilian Holstein cattle population

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Salvian, Mayara ; Silveira, Robson Mateus Freitas ; Petrini, Julina ; Rovadoscki, Gregori Alberto ; Iung, Laiza Helena de Souza ; Ramirez-Diaz, Johanna ; Carrara, Eula Regina ; Pertile, Simone Fernanda Nedel ; Cassoli, Laerte Dagher ; Machado, Paulo Fernando ; Mourao, Gerson Barreto

• Tipo de documento: Artigo Científico
• Fonte: INTERNATIONAL JOURNAL OF BIOMETEOROLOGY; v. 67, n. 2, p. 8-pg., 2022-12-29.

Resumo

Due to the high milk production of Holstein cows, many countries have chosen to import semen to improve local dairy herds. This strategy would be more effective if this semen was used in the same environment conditions in which the bulls were selected. If the effect of genotype by environment (G x E) interaction is not considered, the estimated breeding values (EBVs) may vary, potentially reducing the selection response. We evaluate the impact of heat stress on selection for milk yield and composition of Holstein cows using random regression models. To verify the interference of heat stress in milk yield (MY) and composition traits (fat, protein, total saturated, and total unsaturated fatty acids content in milk), temperature-humidity index (THI) on test-day milk records was used. The threshold value to divide the environments using test-day information from Brazilian Holstein cows was 72 units of THI, i.e., < 72 represented no heat stress and > 72 represented heat stress. Legendre polynomials of second-order (Leg 2) model and two lactation points (33 and 122 DIM) were used to estimate heritabilities and EBVs for five important dairy traits. The heritabilities of milk components and fatty acids were low (0.09-0.29), regardless of lactation period and degree of heat stress, with the exception of protein content (0.30-0.35). Fat content was the only milk component that was reduced according to the degree of heat stress and lactation period. The EBVs tended to decrease in heat stress conditions, thus animals with high genetic potential demonstrated evidence of G x E interaction. However, acclimatization of dairy cows to heat stress in the farm production systems may have been responsible for the low differences among genetic parameters and EBVs with and without heat stress found in this study. (AU)

• Processo FAPESP: 12/15948-7 - Incorporação de informações genômicas no desenvolvimento de índices econômicos para a seleção de bovinos leiteiros
• Beneficiário: Juliana Petrini
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 10/12929-6 - Análise genética quantitativo-molecular para características de produção, perfil de ácidos graxos e qualidade do leite
• Beneficiário: Gerson Barreto Mourão
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 12/24788-3 - Interações epistáticas entre SNPs associados à composição e perfil de ácidos graxos no leite bovino
• Beneficiário: Laiza Helena de Souza Iung
• Modalidade de apoio: Bolsas no Brasil - Mestrado