Gérmen integral de milho extra gordo em dieta para vacas em lactação

Abstract

The objective was to investigate the effects of extra-fatty whole corn germ (EFWCG) on nutrient intake and digestibility, nitrogen (N) utilization efficiency, blood metabolites, mycobrian protein production, milk production and composition, acid profile fatty acids (FA) from milk fat from lactating cows. Ten Holstein cows with 90 ± 10 days of lactation and production of 24.2 ± 3.5 kg of milk/day were assigned to diet treatments consisting of increasing levels of EFWCG (0; 4; 8; 12 and 16%) based on dry matter (DM) in a 5 x 5 Latin square design replicated with periods of 21 days. All diets contained similar proportions of forage cactus (Opuntia stricta [Haw]. Haw), sugarcane (Saccharum officinarum) and concentrate (34:32:34, respectively), but cornmeal was gradually replaced (0; 25; 50; 75 and 100%) by EFWCG in the concentrate.With the exception of EE consumption, which increased linearly, the consumption of all nutrients decreased linearly with the inclusion of EFWCG. The digestibility of DM, MO and NDF reduced, while that of EE increased linearly with the inclusion of EFWCG. The inclusion of EFWCG decreased N consumption and daily N excretion in urine and feces, while the N utilization efficiency increased linearly with the inclusion of EFWCG. Maximum N excretion was estimated at 130 g/day with 7.15% inclusion of EFWCG. Milk production varied quadratically, with the highest milk production estimated at 25.4 kg/day with 7.6% inclusion of EFWCG. Milk production varied quadratically, with the highest milk production estimated at 25.4 kg/day with 7.6% inclusion of EFWCG. On the other hand, the production of milk corrected for fat (MCF) linearly reduced with the inclusion of EFWCG. The concentration of fat and total solids decreased linearly, while the concentrations of milk protein and lactose were not altered with the inclusion of EFWCG. Serum cholesterol levels increased linearly (756 to 1.480 mg/L) with the inclusion of EFWCG. With the exception of the trans-16:1 isomers, the proportions of short- and medium-chain fatty acids in milk fat decreased linearly or showed a quadratic behavior with the inclusion of EFWCG, while the opposite was observed for the 18:0 and of 18:1/18:2, including those with conjugated double bonds. There was a change from trans-11 to trans-10 (linear increase) with the inclusion of EFWCG, resulting in a quadratic behavior in the concentrations of trans-11 18:1 (maximum of 2.51g/100g of total FA, estimated with 9.17% EFWCG) and cis-9, trans-11 CLA (maximum 1.31g/100g total FA, estimated at 8.88% EFWCG) and linear increase in trans-10 18:1, trans-10, cis-12 CLA and trans-9, cis-11 CLA. EFWCG should be considered as an alternative to vegetable oils in feeding programs intended for the production of milk enriched with CLA. However, the inclusion of EFWCG in diets based on forage palm (34%) and sugar cane (32%) reduces the fat content of cow's milk, and this can bring financial losses to the milk producer.