Ž .
Pulster, Objective Software, Sydney, Australia . This package used the pulsar algorithm Ž
. described by Merrium and Wachter 1982 . The ‘‘G parameters’’ were set as G1 s 3.8,
G2 s 2.6, G3 s 1.9, G4 s 1.5, G5 s 1.2. The precision profile was optimised with the Ž
. Ž
. Ž
. coefficient of variation CV option as LH CV s 19.4–18.9 LH Mean .
Breed differences in liveweight and BSC at calving were analysed by Student’s t-test. Categorical data were analysed by chi-square methods, both in an Excel spreadsheet
Ž .
Ž .
Microsoft, USA and by the SAS CATMOD procedure SAS Institute, Cary, USA . Ž
. Continuous data were analysed by the general linear model GLM option of SAS v6.10
Ž .
Ž .
SAS Institute, Cary, USA , or Minitab v10.51Xtra Minitab, PA, USA . If measure- ments were repeated over time, a split plot GLM was used. Each result is presented as
mean SEM, unless stated.
3. Results
3.1. Animals Ž
. The F cows were heavier at calving 340 11 vs. 298 9 kg; F vs. J; p - 0.01 and
Ž .
had a greater BCS 4.6 0.07 vs. 4.4 0.05; F vs. J; p - 0.05 . One cow was
diagnosed with metritis and excluded from the trial. Four J cows were also excluded as they ovulated their first DF before treatment allocation. An additional J cow allocated to
the control group ovulated on day 2. No F cows ovulated before or during the treatment period. With these exclusions, there were eight treated and eight control F cows, and
eight treated and six control J cows. These numbers were the effective n for all variables tested.
3.2. Plasma progesterone concentrations Progesterone was not detected in any samples obtained before insertion of a CIDR
Ž .
device on day 0 and control cows had low plasma progesterone - 0.08 ngrml throughout the entire sampling period. Concentrations increased rapidly after device
insertion, reaching a plateau of 2.8 0.15 ngrml by 45 min and with no further increase in the next 5 h. The mean daily plasma progesterone concentrations were
Ž .
Ž greatest on day 1 4.0 0.07 ngrml; p - 0.05 , then decreased on day 4 2.6 0.1
. Ž
ngrml; p - 0.01 , with no difference between days 4 and 5 2.6 0.14 vs. 2.5 0.14 .
Ž .
ngrml . Concentrations had returned to baseline 0.13 0.07 ngrml within 4 h after device removal. There was no breed effect on mean plasma progesterone concentrations
Ž .
during device insertion 3.3 0.15 vs. 3.0 0.18 ngrml; J vs. F . 3.3. Pulsatile LH concentrations
Representative profiles of LH concentrations on days y1, 1, and 4 are presented for J Ž
. Ž
. cows Fig. 1 and F cows Fig. 2 . Analysis of pulsatile LH data showed a significant
Ž .
effect of breed and treatment on LH pulse frequency p - 0.05 , but only a treatment
Ž .
effect on mean concentrations p - 0.05 . The breed by treatment interaction was not
Ž . Ž
. Ž .
Fig. 1. Typical profiles of LH concentrations for a a Jersey heifer a3501 in the control group and b a Ž
. Jersey heifer a3530 in the treated group.
significant for either LH mean or frequency. Data presented are for the main effects only.
Ž .
Overall frequency of pulsatile LH secretion was greater for J 2.5 0.3 pulsesr8 h Ž
. than F cows 1.4 0.3 pulsesr8 h; p - 0.05 . Pulse frequency was reduced in both
Ž .
breeds on day 1 compared with days y1 and 4 Table 1 . Mean LH concentrations were
Ž . Ž
. Ž .
Fig. 2. Typical profiles of LH concentrations for a a Friesian heifer a3780 in the control group and b a Ž
. Friesian heifer a3805 in the treated group.
Ž .
not affected by breed 0.27 0.02 vs. 0.24 0.02 ngrml; J vs. F . Treatment signifi- Ž
. cantly decreased mean LH concentrations on day 1 0.18 vs. 0.27; SED 0.01; p - 0.05
Ž .
Ž .
compared with days y1 0.27 vs. 0.27; SED 0.01 and 4 0.26 vs. 0.28; SED 0.01 . 3.4. OÕarian follicle dynamics
Observations of ovarian follicles before 12 days post-partum were incomplete in some cows due to the difficulty in locating ovaries with the uterus still enlarged. Many
Table 1 Ž
. The effect of breed and progesterone treatment on the frequency of LH pulses mean pulsesr8 h on the day
Ž .
Ž .
before progesterone treatment day y1 , the day after the insertion of the progesterone device day 1 and the Ž
. day before removal of the progesterone device day 4
Day Control
Treated J
F JqF
J F
JqF
a b
d a
b d
y1 3.0
1.0 2.0
3.1 1.5
2.3
a b
d c
c e
1 2.8
1.5 2.2
0.6 0.5
0.6
a b
d a
b d
4 2.5
1.9 2.2
2.9 2.0
2.4 SEM
0.57 0.49
0.38 0.49
0.49 0.35
a, b, c, d, and e refer to differences within treatment where p- 0.05.
DF1 were already large and in a plateau stage of development. Subsequent post-partum Ž
. DFs DF2 and DF3 were observed from emergence.
3.4.1. Breed effect on post-partum follicle deÕelopment The pattern of follicular development differed between breeds for the DF1 and DF2.
Ž The DF1 was larger at 8 days post-partum for J cows 9.1 0.68 vs. 6.8 0.68 mm; J
. Ž
vs. F; p - 0.02 and reached its maximum diameter earlier 10.5 0.8 vs. 12.6 0.7 .
days post-partum; J vs. F; p - 0.05 . Thus, the post-partum follicle development was earlier in the Jersey breed than the Friesian breed.
Maximum diameter of DF1 was not different among breeds or treatment groups Ž
. Ž
Table 2; p 0.1 . The DF2 emerged earlier in J cows 10.4 0.68 vs. 13.1 0.62 .
days post-partum; J vs. F; p - 0.02 resulting in a larger mean DF2 diameter from 11 to 18 days post-partum for the J cows. The increase in maximum diameter between DF2
Ž .
and DF1 was greater in the J cows p - 0.05; Table 2 .
3.4.2. Breed effect on the DF at the start of progesterone treatment As the emergence of DF2 was earlier for the J breed, there was a predominance of
DF2 compared with DF1 on the first day of progesterone treatment for the J cows, Ž
compared with a similar distribution of DF2 and DF1 for the F cows 12 vs. 2 and 9 vs. .
7, respectively; p - 0.02 . To account for the variation of the DF at the time of
Table 2 Ž
. The effect of breed and treatment on the mean maximum size of DF1 and DF2, and the difference increase in
the size of the successive DF Jersey
Friesian Control
Treated Combined
Control Treated
Combined
a a
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
DF1 11.2 1.3
10.3 1.1 10.7 0.8
12.4 1.1 12.9 1.1
12.6 0.8
a a
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
DF2 13.2 1.1
14.1 0.9 13.6 0.7
12.8 0.9 13.9 0.9
13.3 0.6
a b
Ž .
Ž .
Difference 2.0
3.8 2.9 0.8
0.4 1.0
0.7 0.8 Ž
. a and b refer to significant differences within each row
p- 0.05 .
Ž .
treatment, two DFs were identified. The DF observed at the time of treatment day 0 Ž
. was identified as DF , and the DF observed after treatment day 6 as DF .
6
3.4.3. Follicle deÕelopment relatiÕe to the time of treatment The size of the DF
on day 0 was a significant indicator of subsequent follicle dynamics. If the DF on day 0 was at least 9 mm, then a new DF was observed by the
time of device removal in every one of the nine T cows compared with 4r9 C cows Ž
. p - 0.01 . If the DF on day 0 was at - 9 mm, then a new DF was observed by the
time of device removal in only 1r7 T cows compared with 2r5 C cows. Associated with the consistent loss of dominance of a large DF
in T cows was the earlier Ž
. emergence of DF
day 0.7 0.54 vs. day 3.7 0.56; T vs. C; p - 0.01 . The DF was
6 6
Ž .
G 9 mm for at least 40 h after device removal in 13r16 T cows solid line plots Ž
. compared with 2r14 C cows dashed plots; p - 0.05 .
The three T cows that did not have a large follicle were Friesian. They did not have a single pulse of LH in the 8-h sampling period on days 1 and 4. Two of these cows had a
large DF at the time of device insertion, but a new DF did not emerge until days 3 and 4 resulting in a smaller, growing DF at device removal. The third cow did not have a
follicle 9 mm throughout the entire experimental period.
3.5. PE concentrations
2
Ž .
PE concentrations did not differ on days 6 and 8 Table 3 . A difference in PE
2 2
Ž .
between breeds was observed p - 0.01 , but there was no treatment effect, nor a breed by treatment interaction. Regression analyses of the PE on day 6 showed an increase
2
Ž .
with a larger-diameter DF p - 0.05 , and a greater plasma concentration in the J cows
6
Ž
2
than F cows; but there was no treatment effect. The revised regression model R s .
Ž 39.5; p - 0.05
is plotted in Fig. 3. The regression equation was PE on day
2
. Ž
. Ž
. 6 s 1.10 q 0.0813 DF on day 6 y 0.705 Breed , where Jersey s 0 and Friesian s 1.
6
3.6. Response to treatment A surge in LH concentration, ovulation and oestrus was observed in only two treated
J cows and one control J cow. Cows that ovulated tended to have a greater pulse
Table 3 Ž
. The effect of breed and treatment on mean plasma oestradiol concentrations pgrml on days 6 and 8
Ž .
a and b refer to significant differences within each row p- 0.05 .
Day Jersey
Friesian Control
Treatment Mean
Control Treatment
Mean
a b
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
6 1.7 0.3
2.3 0.3 2.1 0.2
1.1 0.4 1.2 0.4
1.2 0.3
a b
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
8 2.2 0.3
1.8 0.3 2.0 0.2
1.1 0.4 1.3 0.4
1.2 0.3
a b
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Mean 2.0 0.3
2.0 0.2 2.0 0.2
1.1 0.2 1.3 0.2
1.2 0.2
Fig. 3. The relationship between DF diameter and plasma oestradiol concentration on day 6. The fitted Ž
. Ž
2
regression model: y s1.10q0.0813 x y0.705 Breed , where Jersey s 0 and Friesian s1 R s 39.5; p- .
0.05 .
Ž .
frequency on day y1 1.8 0.28 vs. 3.5 1.01 pulsesr8 h; p - 0.15 . An LH surge was not detected for cows that did not ovulate.
4. Discussion
