H. Quesnel et al. Animal Reproduction Science 64 2000 77–87 81
Table 1 Influence of feeding level on ovarian characteristics on day 19 of the oestrous cycle in gilts mean ± SEM,
Experiment 1 Variable
Feeding group Significance
H L
Number of gilts 10
10 Ovarian weight g
17.3 ± 0.7 13.5 ± 0.7
P = 0.001 Number of follicles ≥5 mm
20.6 ± 1.1 16.9 ± 0.8
P = 0.016 Maximum follicular diameter mm
8.2 ± 0.4 7.3 ± 0.3
P = 0.100
3. Results
3.1. Experiment 1 The weight of the ovaries and the number of follicles ≥5 mm on day 19 of the cycle were
decreased by feed restriction P 0.001 and P 0.05, respectively, Table 1 whereas the maximum diameter of follicles was not significantly affected P = 0.1, Table 1.
Concentrations of progesterone measured on days 8 and 15 i.e. in the mid-luteal phase and 24 h after luteolysis induction were not significantly different between treatment groups
56.5 ± 3.6 and 36.4 ± 4.4 ng ml
− 1
on days 8 and 15, respectively. 3.2. Experiment 2
3.2.1. Plasma insulin, glucose and IGF-I system in response to treatments As expected, plasma insulin levels measured 4 h after insulin administration on day 18
were significantly higher in insulin-treated than in not-treated gilts Table 2. This was
Table 2 Influence of exogenous insulin 0.5 IU live weightkg, once daily and feeding level on concentrations of insulin,
glucose, IGF-I and IGFBPs in plasma 4 h after the injection on day 18 of the oestrous cycle in gilts mean ± SEM, Experiment 2
a
Variable Group
H H-I
L-I Number of gilts
8 8
7 Plasma insulin mIU ml
− 1
37 ± 8 a 77 ± 6 b
73 ± 8 b Plasma glucose mg l
− 1
933 ± 45 a 697 ± 70 b
266 ± 38 c Plasma IGF-I ng ml
− 1
316 ± 23 a 290 ± 47 a
136 ± 17 b Plasma IGFBPs arbitrary units
43–39 kDa 214 ± 32
207 ± 20 169 ± 29
34 kDa 15 ± 3
14 ± 2 21 ± 4
29 kDa 8 ± 2
7 ± 1 9 ± 2
24 kDa 2.4 ± 0.6
1.7 ± 0.4 1.4 ± 0.3
a
Means within row with different letters a, b, c differ P 0.05.
82 H. Quesnel et al. Animal Reproduction Science 64 2000 77–87
Table 3 Influence of exogenous insulin 0.5 IU live weightkg, once daily and feeding level on the number and diameter
of follicles in gilt ovaries removed on day 19 of the oestrous cycle mean ± SEM, Experiment 2
a
Variable Group
H H-I
L-I Number of follicles ≥5 mm
19.4 ± 2.0 17.6 ± 0.7
15.3 ± 1.4 Maximum follicular diameter mm
8.7 ± 0.3 x 8.4 ± 0.2 x
7.6 ± 0.4 y Mean diameter of the largest 10 follicles mm
7.7 ± 0.3 x 7.5 ± 0.2 x
6.7 ± 0.3 y
a
Means within row with different letters x, y tend to differ P 0.1.
accompanied by hypoglycaemia which was more pronounced in L-I than in H-I gilts Ta- ble 2. Concentrations of IGF-I were significantly lower in L-I than in H-I and H gilts.
Autoradiography of IGFBPs in plasma revealed five bands data not shown, likely cor- responding to IGFBP-3 43–39 kDa and BP-2 34 kDa, and to unidentified IGFBPs 29
and 24 kDa. Their levels did not significantly differ between groups Table 2. The ratio of IGF-I:43–39 kDa IGFBP 1.8; 1.4 and 0.9 in H, H-I and L-I gilts, respectively tended to
be lower in L-I than in H females P 0.07 and was intermediate in H-I gilts.
3.2.2. Number and diameter of follicles On day 19, the number of follicles ≥5 mm in diameter did not significantly differ between
groups of gilts Table 3. The maximal diameter and the mean diameter of the 10 largest follicles tended to be lower in L-I than in H-I and H females Table 3.
3.2.3. Steroid hormones Although the majority of follicles had an oestradiol concentration in incubation medium in
excess of 1.5 ng ml
− 1
2 h
− 1
, some follicles produced low level of oestradiol, suggesting that they were atretic. Health assessment, by histology of follicles chosen at random confirmed
that atretic follicles had an oestradiol concentration in the incubation medium 1 ng ml
− 1
2 h
− 1
whereas healthy follicles produced 1.5 ng ml
− 1
2 h
− 1
. Using this oestradiol threshold of 1 ng ml
− 1
2 h
− 1
to discriminate healthy and atretic follicles, 6.5 of large follicles were identified as atretic. This percentage was not influenced by treatments P 0.1.
Oestradiol and testosterone concentrations released in the incubation medium by healthy follicles did not significantly differ between groups of females 6.8 ± 0.6 and 12.8 ±
1.1 ng ml
− 1
2 h
− 1
for oestradiol and testosterone, respectively. They were highly correlated with follicular diameter P 0.01 and correlated with each other P 0.001, Fig. 1. The
ratio oestradiol:testosterone was not significantly influenced by treatments 0.64 ± 0.05. 3.2.4. Follicular insulin, glucose and IGF-I system on day 19
Levels of insulin 12.8 ± 0.7 mUI ml
− 1
and IGF-I Fig. 2 in large follicles were not sig- nificantly affected by treatments. Concentrations of IGF-I in large follicles were positively
correlated to follicular diameter r = 0.28, P 0.004. Autoradiography of IGFBPs in large follicles revealed only three bands data not shown, likely corresponding to IGFBP-3
43–39 kDa and BP-2 34 kDa. Levels of 43–39 kDa IGFBP were lower in L-I than in H females P 0.05 and intermediate in H-I gilts, and levels of 34 kDa IGFBP were not
H. Quesnel et al. Animal Reproduction Science 64 2000 77–87 83
Fig. 1. Relationship between oestradiol and testosterone concentrations in culture medium ng ml
− 1
2 h
− 1
for large follicles ≥5 mm from H, H-I and L-I gilts; H: high level of feeding; H-I: high level of feeding + insulin;
L-I: low level of feeding + insulin.
Fig. 2. Glucose, IGF-I and IGFBPs 43–39 and 34 kDa in the follicular fluid of large follicles ≥5 mm removed on day 19 of the oestrous cycle of H, H-I and L-I gilts; H: high level of feeding; H-I: high level of feeding + insulin;
L-I: low level of feeding + insulin.
ab
Means with different superscripts differ P 0.05.
influenced by treatments Fig. 2. Glucose concentrations in large follicles differed between groups of females P 0.05 and are significantly higher in L-I than in H females Fig. 2.
For most gilts, intrafollicular glucose levels varied little between the five follicular fluids collected. Levels of glucose in medium-sized follicles were higher in L-I than in H and H-I
females P 0.05; 843 ± 9; 819 ± 74 and 1074 ± 80 in H, H-I and L-I, respectively. They were highly correlated to glucose levels in large follicles r = 0.68, P 0.004.
4. Discussion
