| Summary: | The effects of a nonionic surfactant, Tween 80 (T-80), on the performance and
nutrient digestibility of dairy cows fed a total mixed ration (TMR) were evaluated.
Fifteen, multiparous Holstein cows in early lactation were randomly assigned to
treatment groups in a replicated 3 x 3 Latin Square design involving three, 28 d
experimental periods. Treatment groups were balanced in terms of days in milk and
estimated 305 d milk production. Cows had ad libitum access to one of the following
diets: 1) TMR consisting of 45% dairy concentrate, 33% grass silage and 22% corn
silage (Control); 2) TMR treated with 0.1% T-80; and 3) TMR treated with 0.2%T-80; all
on a DM basis. Individual feed intake and milk yield were recorded daily. Milk, blood,
and rumen fluid samples were taken during the third week of each period. Total
collection of urine and feces from twelve cows (four from each group) occurred during
the last five days of each experimental period.
Average daily intake and milk yield was not influenced by level of T-80 in the TMR
(P>0.05). Differences in milk protein percentage (P<0.05) with 0.2% T-80 having lower
milk protein than the Control was compensated by higher milk yield when expressed as
daily protein yield (kg d⁻¹). No differences were observed for fat, lactose or somatic cell
count (P>0.05). Blood urea nitrogen was approaching significance (P=0.08) and
implicative of 0.2% T-80 having positive effects on N-utilization over the Control. Cows
consuming 0.2% T-80 had higher rumen levels of acetate (mol 100 mol"1) (P<0.05) than
cows consuming 0.1% T-80, however, neither treatment was different (P>0.05) from the
Control. Observed differences in acetate molar percentages between treatments did not
contribute to differences in molar percentages of volatile fatty acids within treatments.
The acetate to propionate ratio between T-80 treatments was approaching
significance (P=0.08) with 0.2% T-80 having increased acetate production and 0.1% T-
80 increased propionate production, however, neither treatment was different (P>0.05)
from the Control. No differences (P>0.05) were observed in apparent digestibility
estimates of dry matter, crude protein, acid-detergent (ADF) or neutral-detergent fiber
(NDF). A P-value of 0.10 was suggestive of apparent NDF digestibility being lower in
0.2% T-80 treated cows, and when compared to ADF, indicative of decreased
hemicellulose degradation. No treatment difference (P>0.05) was observed for
efficiency of milk yield.
Further research is required before definite conclusions concerning the
experimental treatment levels of T-80 are made. Future work to: 1) investigate prefeeding
aerobic nutrient losses from the TMR as a result of T-80 application; 2) confirm
the effective level of T-80 in prepared diets; and 3) complete a detailed examination of
the effects of T-80 on the rumen microbial population balance and acclimatization rates
were suggested. === Land and Food Systems, Faculty of === Graduate
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