Sources of fat alters performance and metabolism of dairy cows grazing a tropical pasture

Author(s)

Jonas de Souza

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2014-02-07

Examining board members

Flavio Augusto Portela Santos; Alexandre Vaz Pires; Geraldo Tadeu dos Santos

• Advisor: Flavio Augusto Portela Santos

Abstract

The objective of this study was to evaluate inclusion of different sources of fat as calcium salts in the diet on performance and metabolism of early lactation cows grazing tropical pastures. In Chapter 3, a meta-analysis was performed to evaluate the effects of fat supplementation to grazing dairy cows on milk yield and milk composition. Milk yield increased with fat supplementation, and supplementation with unsaturated sources depressed milk fat content. In Chapter 4, the objective was to compare the use of titanium dioxide (TiO2) as an external marker to replace chromium oxide (Cr2O3) to estimate fecal excretion and calculate forage intake and digestibility. Fecal excretion tended to be greater for values estimated by Cr2O3. The Cr2O3 overestimated and TiO2 tended to overestimate fecal excretion compared to total fecal collection. Forage intake and total DM intake were overestimated by Cr2O3, while no differences were observed between the observed values of consumption and estimated by TiO2. The apparent DM digestibility was underestimated by both Cr2O3 and TiO2. In the chapter 5, it was evaluated the effects of fed different sources of fat to early lactation cows (from 15 to 105 DIM) grazing a tropical pasture on production variables throughout lactation (until 280 DIM). Calcium salts of soybean oil (CSSO) increased milk yield compared to control, but was lower than the production of animals supplemented with calcium salts of palm oil (CSPO). Despite the increase in milk yield with CSSO, this treatment decreased milk fat content and yield when compared with control and CSPO. During the residual period (from 106 to 280 DIM) the group that received CSPO had greater milk yield and reflected in the greater milk yield throughout lactation (7328 kg lactation-1) compared to CSSO (6575 kg lactation-1) and the control (6094 kg lactation-1). In chapter 6, the objective was to evaluate the supplementation with two sources (CSSO vs. CSPO) and two doses (400g vs 700g/day) of calcium salts of fatty to mid lactating dairy cows grazing a tropical pasture on performance, milk composition, ruminal and metabolic parameters and energy balance. Milk yield was increased by the addition of fat, being influenced by source and by dose. The milk fat was influenced by source of fat supplementation. The ruminal pH was not affected by experimental treatments. Supplementation with CSSO damaged the fiber degradation, reduced production of VFA \'s, reduced microbial synthesis and the production of milk fat compared with the source of CSPO. In conclusion, DM intake and digestibility were better predicted with the use of titanium dioxide as a marker. Furthermore, supplementation with calcium salts of palm oil increased milk production in lactating without decreasing DM intake and degradation of the fiber. (AU)

• FAPESP's process: 11/15934-3 - Effect of different sources of rumen protected fat to dairy cows kept in elephant grass pasture
• Grantee: Jonas de Souza
• Support Opportunities: Scholarships in Brazil - Master