RESUMO
ABSTRACT During the first weeks of lactation, the energy balance of dairy cows is generally negative, allowing for decompensation in a variety of tissues and systems, especially the immune system. The energy levels of a cow's diet during the first third of lactation, in specialized dairying, will modulate the immune system functionality of the mammary glands. The aim of this study was to assess the sanitary quality of milk through the somatic cell score (SCS), the colony-forming units (CFU), and the isolated bacteria of Holstein cows with different energy levels in the diet. Thus, 24 Holstein cows were studied during their first third of lactation, after the lactation peak (50 to 100 lactation days). They were assigned into 4 treatments, taking into account the energy requirements of each animal: Isoenergetic (ISO), Hypoenergetic (HYPO), Hyper energetic (HYPER), and Isoenergetic plus sunflower oil supplementation (OIL). Milk samples were taken for the somatic cell count (SCC) and CFUs, and isolated pathogens in milk were identified by microbiological culture. The diet had a significant effect on SCS with a value p of 0.0331, but not on the CFUs (p< 0.5141). 11 pathogens were identified and in 33.9% of samples, microorganisms were not isolated. The Isoenergetic diet favors the presence of some microorganisms and the increase of SCS.
RESUMEN En las primeras semanas de lactancia, generalmente, el balance energético de la vaca lechera es negativo, determinando una descompensación en diferentes tejidos y sistemas, en especial, el inmunológico. Los niveles de energía en la dieta de vacas, en primer tercio de lactancia en lechería especializada, modularán la funcionalidad del sistema inmune en glándula mamaria. El objetivo del presente trabajo fue evaluar la calidad sanitaria de la leche, a través de la medición de células somáticas (SCS), las unidades formadoras de colonias (UFC) y las bacterias aisladas de vacas Holstein, con diferentes niveles de energía en la dieta. Se usaron 24 vacas Holstein en el primer tercio de gestación, posterior al pico de lactancia (entre 50 y 100 días de lactancia), dispuestas en 4 tratamientos, de acuerdo con el cubrimiento de los requerimientos energéticos del animal: isoenergético (ISO), hipoenergético (HIPO), hiperenergetico (HIPER) e isoenergético más suplementación con aceite de girasol (ACEITE). Se tomaron muestras de leche para el recuento de células somáticas (RCS) y UFC y se identificaron patógenos en leche, por cultivos microbiológicos. La dieta tuvo un efecto significativo sobre el SCS, con un valor p de 0.0331 y no sobre las UFC (p<0.5141). Se identificaron 11 patógenos y en 33,96% de las muestras no se aislaron microorganismos. La dieta isoenergética favorece la presencia de algunos microorganismos y el aumento del SCS.
RESUMO
Our goal was to define the effect of the energy intake in Holstein cows' diet in the first third lactation on gene expression profile of immune system in mammary gland through RNA-seq. Twelve Holstein cows were used in the first third of lactation, arranged in four treatments or diets: (a) hypocaloric (HYPO, 85% of the net energy of lactation (NEl) requirements), (b) isocaloric (ISO, 100% of the NEl requirements, control diet), (c) hypercaloric (HYPER, 115% of the NEl requirements) and (d) isocaloric plus sunflower oil supplementation (OIL, 106% of the NEl requirements). A biopsy of mammary gland tissue was carried out after 25 days per diet, from which the RNA was extracted and sequenced using the Illumina HiSeqTM 2,500 sequencer. The analysis of reads obtained from the sequencing in the QIAGEN® CLC Genomics Workbench 10.0 bioinformatics software was performed. From 27,368 genes annotated in the reference genome, 17,429 genes expressed in the evaluated treatments were identified. Moreover, 1,743 differentially expressed genes (DEGs) were found, of which 15 DEGs were found in the ISO vs. OIL comparison, 1,196 DEGs in the ISO vs. HYPO comparison and 532 DEGs in the ISO vs. HYPER comparison. Thus, of the 1,743 DEGs, 401 correspond to genes involved in the functioning of the immune system, encompassing 23% of the total number of DEGs involved in the analysis, and 13.6% of the total number of genes involved in the functioning of the immune system. The energy intake in Holstein cows' diet has impact in the expression of immune genes CXCL13, TRDC among others, present in the regulation of immune system processes. This immune system altered might increase the somatic cells score and therefore reach some diseases. It is recommended to measure the energy intake according to the animals' energy requirements and to cover them the closest to the 100%.
