Including chicory or plantain in a perennial ryegrass/white clover-based diet of dairy cattle in late lactation: Feed intake, milk production and rumen digestion

In temperate grass-based dairy cattle grazing systems, summer dry conditions can reduce feed availability and quality, and limit milk production. This study reports the effects of including high nutritive value, drought tolerant forbs, chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.), in a grass-based diet of dairy cattle on intake, milk production and digestion. Forty-two mixed aged cattle in late lactation were randomly allocated to one of five dietary treatments in late summer: perennial ryegrass/white clover (PRG) or ryegrass/white clover (ryegrass) with either chicory (CHI) or plantain (PLA) comprising either 20 or 40% of the daily dry matter intake (DMI). Each treatment group included three cattle with a permanent rumen fistula. The experiment was conducted in an indoor feeding facility to allow individual intakes to be determined and comprised of two independent measurement weeks (Week I and Week II). Over the two measurement weeks, milk production and DMI were similar across diets and there were only minor differences in milk composition. Different effects of including chicory or plantain in the diet were observed, however, between measurement weeks. In Week I, DMI of cattle offered chicory or plantain (forbs) was 10% less than cattle offered PRG (14.7 vs. 16.4 kg dry matter (DM)/cow/d, p = 0.039) but milk yield (12.3 +/- 0.53 kg/cow/d) and milk component (fat + protein) yield (1.01 +/- 0.05 kg/cow/d) were similar across diets. In Week II, DMI was similar (14.2 kg DM/cow/d), but cattle offered forbs produced 19% more milk and 17% more milk component yield than those offered PRG. The decrease in DMI and milk production from Week I to II on the PRG treatment was accompanied by a decline in the estimated nutritive value of the ryegrass in the diets. In sacco incubations of fresh forages showed slower rates of DM degradation of ryegrass, relative to chicory or plantain (0.11 vs. 0.22 and 0.19%/h respectively; p < 0.001). Total rumen volatile fatty acid concentration and molar proportions measured in 6-hourly spot samplings was similar across diets. Rumen ammonia (NH3) and urine nitrogen (N) concentrations, however, were reduced by up to 37 and 38% in cattle where forb was included in the diet, with greater reductions observed with increasing percentage of forb in the diet (p < 0.01). This study suggests that chicory and plantain are suitable species to include in the diet of cattle grazing temperate grass-based swards to maintain or improve milk production in summer. Furthermore, the reductions in rumen NH3 and urine N observed, indicate potential environmental benefits could be gained from feeding forbs.