Effect of dietary non-fiber carbohydrate source and inclusion of buffering on lactation performance, feeding behavior and milk stability of dairy cows

Abstract

The present study hypothesized that partial replacement of ground corn (GC) by pelleted citrus pulp (PCP) and buffering (BF) inclusion in diets of lactating cows does not change lactation performance, but does reduce milk concentration of ionic calcium (iCa), increasing its stability at ethanol test and heating at 140 °C (heat coagulation time – HCT). We evaluated the effect of PCP and buffer inclusion on digestive metabolism, feeding behavior, milk yield, and milk stability of lactating cows. Sixteen Holstein cows (average milk yield of 28 ± 4.8 L/d and days in milk of 130 ± 81.0; mean ± SD) were distributed in a Latin square design with 4 replicated squares, 4 periods of 21 d (14 d for adaptation and 7 d for sampling) and 4 treatments in a 2 × 2 factorial arrangement. Treatment factor 1 was the partial replacement (134 g/kg) of GC by PCP and factor 2 was the inclusion of buffer (7.1 g/kg of Na bicarbonate plus 2.4 g/kg of Mg oxide; DM basis) in diets composed of 40:60 of forage: concentrate ratio. The partial replacement of GC with PCP reduced dry matter intake (DMI) by 1.35 kg/d, increased dry matter (DM) and neutral detergent fiber assayed with a heat stable amylase and expressed exclusive of residual ash (aNDFom) digestibility, and ruminal concentration of acetic and butyric acids, but no change was observed on milk yield, resulting in higher production efficiency. The partial replacement of GC with PCP also reduced the ruminal concentration of iso-butyric and iso-valeric acids, milk urea nitrogen concentration, and casein content and tended to reduce HCT. There was no isolated effect of GC replacement or buffer addition or their interaction on iCa concentration and milk stability at the ethanol test. For diets without the inclusion of PCP, cows increased drinking time by 8 min/d. When cows were fed diet with the inclusion of PCP, the rumination time decreased 57 min/kg physical effective aNDFom (peNDF) intake compared to when cows were fed diets without partial replacement of GC with PCP. The buffer inclusion increased milk fat content and urinary pH. However, milk stability at ethanol test did not change in response to treatments and HCT tended to be reduced when GC was replaced by PCP. The results of our study suggested that, although partial replacement of GC with PCP and BF inclusion altered DMI, short chain fatty acids (SCFA) concentration, and urinary pH, those factors did not change milk yield and milk stability.