Níveis de amido na dieta de cabras em lactação

Abstract

Starch energetically thickens diets of lactating animals and starch causes divergent productive responses among ruminant species. The objective was to evaluate the effects of dietary starch levels on the productive, digestive, behavioral and metabolic parameters of lactating goats. The experiment was carried out at the Experimental Animal Bioterium for Goats and Sheep at the Federal University of São João del-Rei (UFSJ), using 16 lactating Saanen goats, with a body weight of 48.7 ± 4.7 kg, a body condition score of 2 .3 ± 0.6, milk production of 1.9 ± 0.8 kg/day and 116 ± 3 days in lactation, distributed in a replicated Latin square with periods of 21 days and four diets: 17%, 24%, 31 % and 38% starch in dry matter (DM). The animals were fed ad libitum obeying 10% leftovers. The evaluations occurred between d15 and d21 of each experimental period. Data were analyzed with SAS PROC MIXED. The effects of starch levels were submitted to ANOVA and F test with P ≤ 0.05 and PROC REG was used to determine the regression equation with linear, quadratic or cubic effect. DM intake (1.578; 1.687; 1.847 and 2.058 kg/d), protein (CP; 0.250; 0.265; 0.277 and 0.309 kg/d) and starch (ST; 0.318; 0.466; 0.637 and 0.810 kg/d) increased linearly , while consumption of neutral detergent fiber (NDF; 0.651; 0.539; 0.562 and 0.538 kg/d) and physically effective NDF (FDNfe>8; 0.212; 0.161; 0.118 and 0.082 kg/d) decreased (P<0.05 ) with the increase of starch. All animals showed preferential ingestion of short particles, while the refusal of long particles increased (73; 69; 66 and 65) in response to the increase in starch (P<0.05). The increase in dietary starch did not affect (P>0.05) DM (73.39%) and ST (97.72%) digestibility, but linearly reduced (P<0.05) CP digestibility (82. 5; 78.59; 78.68 and 76.58%) and NDF (56.36; 48.58; 47.72 and 45.62%) and linearly increased (P<0.05) fecal starch (2 .08; 2.05; 2.63 and 3.25%) and fecal score (2.08; 2.18; 2.57 and 3.42). The animals linearly reduced (P<0.05) the chewing time (694; 627; 579 and 543 min/d) and duration of meals (69; 56; 48 and 37 min/d), while they linearly increased (P< 0.05) idle time (588; 631; 645 and 698 min/d) and the number of meals (4; 5; 5 and 7 meals/d) with increased starch. There was a reduction in serum cholesterol concentration (84.8; 77.0; 74.69 and 73.2 mg/dl) and an increase (P<0.05) in glucose (59.67; 60.43; 62.63 and 63.61 mg/dl) and gamma glutamyl transferase (52.94; 55.13; 59.5 and 63.73 U/L) by increasing starch levels. The production of milk (1.717; 1.871; 1.940 and 2.073 kg/d), fat (0.046; 0.050; 0.052 and 0.056 kg/d) and protein (0.040; 0.046; 0.046 and 0.050 kg/d) were increased with an increment of 17 to 38% of starch in the diets, without altering the milk composition. Lactating goats support diets with up to 38% starch, increase nutrient intake, milk and fat production (kg/d), with effects on energy metabolites and liver enzymes.