Effect of dietary crude protein degradability and corn processing on lactation performance and milk protein composition and stability

Autor(es)

Martins, C. M. M. R. ^[1] ; Fonseca, D. C. M. ^[1] ; Alves, B. G. ^[1] ; Arcari, M. A. ^[1] ; Ferreira, G. C. ^[1] ; Welter, K. C. ^[2] ; Oliveira, C. A. F. ^[3] ; Renno, F. P. ^[1] ; Santos, M. V. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Sch Vet Med & Anim Sci, Dept Anim Nutr & Prod, BR-13635900 Pirassununga, SP - Brazil

^[2] Univ Sao Paulo, Sch Food Engn & Anim Sci, Dept Anim Sci, BR-13635900 Pirassununga, SP - Brazil

^[3] Univ Sao Paulo, Sch Food Engn & Anim Sci, Dept Food Engn, BR-13635900 Pirassununga, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF DAIRY SCIENCE; v. 102, n. 5, p. 4165-4178, MAY 2019.
• Citações Web of Science: 0

Resumo

The present study aimed to evaluate the effect of crude protein degradability and corn processing on lactation performance, milk protein composition, milk ethanol stability (MES), heat coagulation time (HCT) at 140 degrees C, and the efficiency of N utilization for dairy cows. Twenty Holstein cows with an average of 162 +/- 70 d in milk, 666 +/- 7 kg of body weight, and 36 +/- 7.8 kg/d of milk yield (MY) were distributed in a Latin square design with 5 contemporaneous balanced squares, 4 periods of 21 d, and 4 treatments (factorial arrangement 2 x 2). Treatment factor 1 was corn processing {[}ground (GC) or steam-flaked corn (SFC)] and factor 2 was crude protein (CP) degradability (high = 10.7% rumen-degradable protein and 5.1% rumen-undegradable protein; low = 9.5% rumen-degradable protein and 6.3% rumen-undegradable protein; dry matter basis). A significant interaction was observed between CP degradability and corn processing on dry matter intake (DMI). When cows were fed GC with low CP degradability, DMI increased by 1.24 kg/d compared with cows fed GC with high CP degradability; however, CP degradability did not change DMI when cows were fed SFC. Similar interactions were observed for MY, HCT, and lactose content. When cows were fed GC diets, high CP degradability reduced MY by 2.3 kg/d, as well as HCT and lactose content, compared with low CP degradability. However, no effect of CP degradability was observed on those variables when cows were fed SFC diets. The SFC diets increased dry matter and starch total-tract digestibility and reduced beta-casein (CN) content (% total milk protein) compared with GC diets. Cows fed low-CP degradability diets had higher glycosylated kappa-CN content (% total kappa-CN) and MES, as well as milk protein content, 3.5% fat-corrected milk, and efficiency of N for milk production, than cows fed high-CP degradability diets. Therefore, GC and high-CP degradability diets reduced milk production and protein stability. Overall, low CP degradability increased the efficiency of dietary N utilization and MES, probably due to changes in casein micelle composition, as CP degradability or corn processing did not change the milk concentration of ionic calcium. The GC diets increased beta-CN content, which could contribute to reducing HTC when cows were fed GC and high-CP degradability diets. (AU)

• Processo FAPESP: 15/03942-2 - Estabilidade do leite durante o processamento térmico de pasteurização e UAT (Ultra Alta Temperatura)
• Beneficiário: Cristian Marlon de Magalhães Rodrigues Martins
• Modalidade de apoio: Bolsas no Brasil - Doutorado