The rate of intake of sweet, salty and bitter concentrates by dairy cows

Abstract

AbstractChanges in the formulation and flavour of concentrate foods may temporarily reduce their acceptability to cattle, leading to reduced intake when they are offered for a limited time during milking. The rate of intake of 12 dairy cows offered 1 kg of salty or bitter concentrates was compared with a sweet concentrate, with or without an artificial sweetener to mask adverse flavours. The cows were offered the test concentrates twice a day in a Latin-square design with seven feeding occasions per period and the apparent and actual (excluding non-feeding time) food intake rates were recorded for all seven feeding occasions. Both apparent and actual intake rates were slower for the bitter compared with the salty and sweet flavoured concentrate.For the first two feeding occasions the intake rate was recorded separately for the 1st min and the subsequent period until the end of feeding. The intake rate was faster in the 1st min because of more rapid prehension of the food and fewer interruptions to the feeding process. Where no mask was included there was no effect of flavour on the apparent intake rate in the 1st min of the first feeding occasion but in the 1st min of the second feeding occasion the apparent intake rate of the salty concentrate was less than that for the sweet or bitter concentrates. The actual intake rates of the bitter and salty concentrates were less than for the sweet concentrate. The mask increased the apparent intake rate of the bitter and sweet concentrates in the 1st min of both the first and second feeding occasions, by reducing the non-feeding time and it also increased the actual intake rate of salty concentrates.After the 1st min the apparent intake rate of the salty concentrate was faster than that of the bitter and sweet concentrates, where no mask was included. The mask increased the apparent intake rate of the sweet concentrates at this time but reduced it for salty and bitter concentrates. It therefore reduced the acclimatization to the salty and bitter concentrates and enhanced the attractiveness of the sweet concentrates.There was a residual effect from the previous period of concentrates which were eaten slowly i.e. salty concentrates, which reduced the 1st min intake of foods that were eaten rapidly, i.e. sweet concentrates, in the subsequent period. This was largely due to increases in the time spent pausing between bouts of food ingestion. After the 1st min the apparent intake rate of cows receiving salty concentrate for a second consecutive period was increased, suggesting acclimatization. The opposite effect was observed for the sweet concentrate, probably because the novelty of the sweetness had diminished, making it relatively less attractive to the cow. This experiment therefore provides evidence that bitter and to some extent salty concentrates are consumed at a slower rate than sweet concentrates, except for the 1st min in which they are offered to cattle and that a reduced concentrate intake rate may persist after the flavour is removed from the food. Cattle did, however, demonstrate an ability to acclimatize to salty concentrate over time.