Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2001
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: It is common for dairy producers to increase dietary phosphorus (P) above NRC requirements in an attempt to increase expression of estrus. The objective of this study was to determine the effect of dietary P concentrations of .38 or .48% of the TMR (DM basis) on estrous behavior of lactating cows as measured by a radiotelemetric system (HeatWatch DDX, Denver, CO). At calving 48 Holstein cows were randomly assigned to one of the dietary treatments. Cows were housed in a free-stall barn and received a radiotelemetric transmitter on d 45 postpartum to record estrous standing activity. Observation on estrous behavior presented here are from the first year of a two-year study published elsewhere (J. Dairy Sci. 83:1052). The radiotelemetric system was employed only during the first year of that study. The total number of estrous periods recorded for the 48 cows was 83. The mean duration of estrous cycles was 22+/0.8 d with a range of 17 to 26 d and 21 +/0.6 d with a range of 16 to 29 d for cows fed the .38 and .48% P diets, respectively (P=0.82). The mean duration of estrus was 9.1+/1.0 and 8.8+/1.1 h for cows fed the .38 and .48% P diets, respectively (P=0.82). The average number of mounts during estrus was 7.5+/1.2 and 8.0+/1.5 (P=0.81) and the total mounting time was 29.6+/1.0 and 31.9+/5.8 s (P=0.75) for cows fed the .38 and .48% P diets, respectively. Phosphorus treatment had no detectable effect (P=0.87) on intensity and duration of estrous behavior.