Increasing sodium bicarbonate level in high-concentrate diets for heifers. I. Effects on intake, water consumption and ruminal fermentation

Abstract

Four ruminally fistulated Holstein heifers (BW 5 264 6 12 kg) were used in a 4 3 4 Latin square design experiment to determine the effect of increasing levels of sodium bicarbonate (BICARB; 0%, 1.25%, 2.50% and 5%, on concentrate dry matter (DM) basis) on DM intake (DMI), water consumption and ruminal fermentation. Sampling was carried out in the last week of each four 21-day experimental periods. Heifers were offered concentrate (13.4 6 0.04% crude protein (CP), 13.3 6 0.44% NDF, 51.7 6 0.97% starch) and barley straw once daily at 0830 h ad libitum. There was a linear decrease in concentrate DMI and a linear increase in straw DMI with increasing buffer level in the diet, resulting in a tendency towards a linear decrease in total DMI. Intake of concentrate was 6.89, 7.66, 6.72 and 5.72 6 0.83 kg/day, whereas straw intakes were 0.73, 0.84, 0.94 and 1.06 6 0.14 kg/day, for the 0%, 1.25%, 2.5% and 5% BICARB, respectively. Water consumption was not affected by treatments when expressed as l/day or percentage of BW, but increased linearly when expressed as l/kg of DMI. The percentage of total daily water drunk in the morning (from 0830 to 1230 h) increased linearly with the level of buffer. Mean ruminal pH and total area under the pH curve were not affected with increasing buffer level. The lowest daily pH (5.65 6 0.09) was not affected by treatments. A quadratic tendency (P < 0.10) was observed in the number of hours and the area under the pH curve in which ruminal pH was below 5.8, with high values only at the 0% BICARB. Additionally, increasing bicarbonate level caused a linear increase in the ruminal pH at 2 and 4 h after feeding. Daily average NH 3 N (2.4 6 0.9 mg N/100 ml) and total volatile fatty acids (VFA) (143 6 12 mM) concentrations were not affected by treatments. Daily average molar proportion of propionate decreased linearly, and acetate proportion and the acetate-to-propionate ratio were increased with increasing buffer level in the diet. Molar percentage of butyrate, isobutyrate and isovalerate, and branched-chain VFA concentration increased linearly as the level of bicarbonate increased in the diet. Results indicate that high levels of BICARB to finishing heifers fed high-concentrate diets may result in a decreased DMI without significant effects on mean ruminal pH, which may affect animal performance. All individual VFA proportions, except valerate, were changed by the addition of bicarbonate.

Increasing sodium bicarbonate level in high-concentrate diets for heifers. II. Effects on chewing and feeding behaviors

“…The proportion of time spent drinking was not affected by treatments (Table 2), which is in agreement with the lack of effect on total daily water consumption (Gonzá lez et al, 2008). Heifers spent an average of 2.48 6 0.16% of the day on drinking activities.…”

“…Feed intake behavior Linear increases of BICARB level decreased linearly the amount of concentrate intake and increased that of barley straw, resulting in a tendency to decrease the total DMI (Gonzá lez et al, 2008). This was achieved through linear decreases in the number of meals per day.…”

“…Animals, experimental design and housing Animals, diets and the experimental design were described in the study by Gonzá lez et al (2008). Briefly, four Holstein heifers (average initial BW of 264 6 12 kg, final BW of 361 6 23) were used in a 4 3 4 Latin square design with four 21-day periods.…”

“…Diets contained 0% (control diet), 1.25%, 2.5% and 5% of added BICARB to the concentrate, dry matter (DM) basis. Additional information on ingredients, chemical composition and processing can be obtained in the study by Gonzá lez et al (2008). To record the feed intake from days 14 to 18 of each experimental period, an automated system was used.…”

“…The experimental unit and statistical models used are described elsewhere (Gonzá lez et al, 2008). All variables were averaged to generate period means for each heifer period that represented a mean daily value.…”