30500
document
Effects of application in spring of urea fertiliser on aspects of reproductive performance of pasture-fed dairy cows . AIMS To assess if raising concentrations of crude protein ( CP ) in pasture in spring by the frequent application of urea fertiliser would affect ovarian follicular dynamics , luteal function , onset of oestrus and reproductive performance of dairy cows under farming conditions in New Zealand . METHODS Spring-calved dairy cows were grazed for 101 days in paddocks that were either not fertilised ( Control ; n=20 ) during the course of the study , or were fertilised with 40-50 kg nitrogen ( N ) /ha every 4-6 weeks ( High-N ; n=20 ) . Similar generous pasture allowances were offered to both groups . Concentrations of CP in pasture , urea in serum and progesterone in milk were measured . Ovarian follicular and luteal dynamics were determined using ultrasonography . Oestrous behaviour and the number , time and outcome of inseminations were also recorded . RESULTS Mean concentrations of CP in pasture and urea in serum was higher in the High-N than the Control group ( 25.2 vs 21.6 and 8.3 vs 5.4 mmol/L for CP and urea , respectively ; p < 0.001 ) . Intervals between calving and first oestrus , first insemination and conception , the time of first emergence of a dominant follicle , milk progesterone concentration , and the diameter of the corpus luteum ( CL ) in the first luteal phase did not differ significantly between groups . The interval from calving to first ovulation tended ( p=0.10 ) to be lower and the diameter of the dominant follicle of the oestrous cycle at which cows conceived was greater ( p=0.02 ) in Control than High-N cows . CONCLUSIONS The use of large amounts of urea fertiliser during spring and the consequent increases in concentrations of CP in pasture and urea in serum did not negatively affect any of the parameters of reproductive performance of pasture-fed dairy cows that were assessed in this study .
30501
Intervention_Pharmacological
urea fertiliser
30502
Intervention_Pharmacological
urea fertiliser
30503
Intervention_Control
not fertilised
30504
Intervention_Pharmacological
fertilised
30505
Intervention_Pharmacological
40-50 kg nitrogen
30506
Intervention_Pharmacological
urea fertiliser
30507
Outcome_Physical
ovarian follicular dynamics
30508
Outcome_Physical
luteal function
30509
Outcome_Physical
onset of oestrus
30510
Outcome_Physical
reproductive performance
30511
Outcome_Physical
Concentrations of CP in pasture
30512
Outcome_Physical
urea in serum
30513
Outcome_Physical
progesterone in milk
30514
Outcome_Physical
Ovarian follicular and luteal dynamics
30515
Outcome_Other
Oestrous behaviour and the number , time and outcome of inseminations
30516
Outcome_Physical
Mean concentrations of CP in pasture
30517
Outcome_Other
and
30518
Outcome_Physical
urea in serum
30519
Outcome_Physical
Intervals between calving and first oestrus
30520
Outcome_Physical
first insemination and conception
30521
Outcome_Physical
the time of first emergence of a dominant follicle
30522
Outcome_Physical
milk progesterone concentration
30523
Outcome_Physical
diameter of the corpus luteum ( CL ) in the first luteal phase
30524
Outcome_Physical
interval from calving to first ovulation
30525
Outcome_Physical
diameter of the dominant follicle of the oestrous cycle at which cows
30526
Outcome_Other
conceived
30527
Outcome_Physical
concentrations of CP in pasture
30528
Outcome_Other
and
30529
Outcome_Physical
urea in serum
30530
Outcome_Physical
reproductive performance
30531
Participant_Condition
pasture-fed
30532
Participant_Sample-size
n=20
30533
Participant_Sample-size
n=20