Effect of forage conservation method, concentrate level and propylene glycol on intake, feeding behaviour and milk production of dairy cows

The current study was conducted to establish if effects on animal performance due to differences in forage composition resulting from conservation method could be compensated for by increases in concentrate feeding or supplements of a gluconeogenic substrate. Thirty-two Finnish Ayrshire dairy cows were used in a cyclic change-over experiment with four 21-day experimental periods and a 4 X 2 X 2 factorial arrangement of treatments to evaluate the effects of forage conservation method, concentrate level and propylene glycol (PG), and their interactions, on intake, feeding behaviour and milk production. Experimental treatments consisted of four conserved forages offered ad libitum, supplemented with two levels of a cereal-based concentrate (7 or 10 kg/day) and PG (0 and 210 g/day) offered as three meals of equal size. Forages were prepared from primary growths of timothy and meadow fescue swards and ensiled using no additive (NA), an inoculant enzyme preparation (IE) or a formic-acid based (FA) additive or conserved as hay 1 week later. Cows given silage-based diets had higher (P < 0.001) forage dry-matter (DM) intakes (mean increase 0.76 kg/day), spent less (P < 0.001) time eating and chewing (mean response -159 and -119 min/day, respectively) and produced more (P < 0.05) energy-corrected milk (ECM), milk fat and milk lactose (respective mean responses 1.52, 0.098 and 0.033 kg/day) than animals given hay-based diets. Use of an additive during ensiling further improved (P < 0.05) silage DM intake, ECM yield and milk protein secretion (mean 0.72, 0.70 and 0.038 kg/day, respectively). Dietary inclusion of PG decreased forage DM intake for hay, IE and FA silage-based diets (mean -0.14, -0.16 and -0.42 kg/day, respectively) but elicited positive responses (mean 0.57 kg/day) for cows given NA silage. Furthermore, PG supplementation had no (P > 0.05) effects on ECM yield or milk protein output but depressed (P < 0.05) mean milk fat content from 46.6 to 45.6 g/kg. Increases in concentrate feeding were associated with a reduction in the total amount of time cows spent eating, chewing and ruminating and elicited (P < 0.001) mean DM intake, ECM yield, milk fat and milk protein responses of 1.5, 1.62, 0.061 and 0.064 kg/day, respectively. Use of a gluconeogenic substrate or increases in concentrate feeding were unable to compensate for variations in animal performance due to forage conservation method.