Gérmen integral de milho extra gordo como alternativa Lipídica para vacas em lactação

Abstract

Alternative lipid sources have been studied to improve performance and the fatty acid profile of milk fat in ruminants. Full-fat corn germ (FFCG) is pointed out as a potential lipid ingredient to improve performance and manipulate the fatty acid profile of milk from dairy cows. However, its effects are dependent on forage sources included in the diet. Hence, the objective of this study was to evaluate the effects of replacing corn with FFCG in diets containing forage cactus and sugarcane bagasse on performance, nutrient intake and digestibility, nitrogen balance, milk composition, and milk fatty acid profile of crossbred cows. It was hypothesized that replacing corn with FFCG in a basal diet containing forage cactus and sugarcane bagasse would promote productivity gains and enrich milk with CLA and other health-beneficial fatty acids beneficial without negative effects on nutrient intake and digestion. The experiment involved 10 multiparous Girolando cows (5/8 Holstein x 3/8 Gir), with an initial live weight of 500 ± 66 kg and lactation period of 90 ± 15 days. The cows were pre-adapted to the experimental conditions for 15 days and then distributed in two 5 x 5 Latin Squares. Each experimental period was composed of 21 days (14 days for adaptation to the experimental diets and 07 for data and sample collection), totalizing 105 days of experiment. The diets were formulated with “Orelha de Elefante Mexicana” cladodes, sugarcane bagasse and concentrate, in which corn was progressively replaced with FFCG (0%, 25%, 50%, 75%, and 100% of substitution). The following variables were analyzed: nutrient intake and digestibility, milk production and composition, nitrogen balance, and milk fatty acid profile. Full-fat corn germ improved (P < 0.05) milk production and synthesis of fat, lactose, and total solids in milk. Replacing corn with FFCG quadratically increased (P < 0.05) the intake of dry matter, crude protein, and total digestible nutrients, and linearly reduced (P < 0.05) the intake of total non-fiber carbohydrates (NFC). Except for ether extract and NFC, FFCG did not alter (P > 0.05) nutrient digestibility. Adding FFCG to the diets reduced (P < 0.05) excretion of urea-N in milk and N excretion via urine. Furthermore, the substitution of corn for FFCG reduced (linearly or quadratically) the concentration of £C16 saturated fatty acids (FA, g/100 g of total FA), odd branched-chain FA, and C18:3 n-3 (as well as other n-3 FA) in milk fat. In contrast, there was a linear or quadratic increase in the proportion of long-chain fatty acids (³ C18), isomers of cis/trans C18:1 (except cis-11 C18:1), CLA isomers (especially cis-9, trans-11 CLA), C18:2 n-6 and other n-6 FA. These changes resulted in reduction in saturated FAs, an increase in mono- and polyunsaturated FAs (quadratic and linear effect, respectively), and a linear increase in the trans C18:1/C18:0, trans-11 C18:1/C18:0, and n-6:n-3 ratios. In addition, activity indices of the SCD-1 enzyme were reduced either linearly (SCD14, SCD16, and SCDCLA) or quadratically (SCD18) by increasing levels of FFCG in the diet. The results obtained indicate that substitution of corn by FFCG (up to 63.5%) can be a nutritional strategy to improve the production efficiency and fatty acid profile of milk fat from crossbred cows fed cactus cladodes. The use of sugarcane bagasse circumvents the deleterious effects of FFCG associated with milk fat depression.