Foetal and postnatal exposure to high temperatures alter growth pattern but do not modify reproductive function in male rabbits

Figures & data

Figure 1. Schematic illustration of gestation and lactation period and time of exposure to high temperatures in the experimental groups. G⁻&L⁻, control animals raised in standard laboratory temperatures during both gestation and lactation; G⁺&L⁻, animals exposed to high temperatures during gestation; G⁻&L⁺, animals exposed to high temperatures during lactation; G⁻&L⁺, animals exposed to high temperatures during both gestation and lactation.

Figure 2. Representative images of haematoxylin and eosin stained sections from rabbit seminiferous tubules. (A) and (B) seminiferous tubules without a lumen; (C) seminiferous tubules without a lumen with presence of spermatids in the seminiferous epithelium; (D) seminiferous tubules without a lumen; (E) presence of spermatids in the seminiferous epithelium; (F) presence of spermatozoa in the lumen of the seminiferous tubules. Microphotographs (A) and (D) were observed under a light microscope at ×100. Microphotographs (B), (C), (E) and (F) were observed under a light microscope at ×400.

Table 1. Ejaculates and sperm parameters and motility assessment of male rabbits exposed to high temperatures during pregnancy and the postnatal period.

	Semen parameters
Environmental conditions	Volume (mL)	Concentration (10^6)	Production (10^6 spz)	Subjective motility (%)	Viability (%)	Intact apical ridge (%)	Abnormal sperm (%)
Gestation
G^−	0.68 ± 0.073	203.5 ± 19.68	139.6 ± 18.64	79.6 ± 4.00	78.7 ± 2.13^a	77.2 ± 1.83^a	20.0 ± 1.88
G^+	0.88 ± 0.074	189.7 ± 20.22	166.8 ± 19.26	82.8 ± 4.14	86.3 ± 2.18^b	82.9 ± 1.83^b	22.2 ± 1.94
Lactation
L^−	0.79 ± 0.074	192.7 ± 19.14	149.4 ± 18.81	82.5 ± 4.04	83.4 ± 2.07	81.4 ± 1.78	20.3 ± 1.83
L^+	0.77 ± 0.076	200.5 ± 20.84	157.1 ± 19.55	79.9 ± 4.20	81.6 ± 2.24	79.1 ± 1.93	21.9 ± 1.99
Cross
G^−&L^−	0.69 ± 0.097	224.1 ± 25.31	157.5 ± 24.76	80.4 ± 5.31	82.5 ± 2.77	80.0 ± 2.35	19.7 ± 2.42
G^+&L^−	0.67 ± 0.112	182.9 ± 30.89	121.7 ± 28.76	78. ± 6.17	74.8 ± 3.35	74.3 ± 2.94	20.4 ± 2.96
G^−&L^+	0.88 ± 0.109	161.4 ± 28.34	141.2 ± 27.76	84.5 ± 5.96	84.3 ± 3.02	82.0 ± 2.63	20.9 ± 2.71
G^+&L^+	0.88 ± 0.100	218.1 ± 28.54	192.4 ± 26.64	81.2 ± 5.72	88.3 ± 3.17	83.9 ± 2.65	23.5 ± 2.74

G⁻, animals raised in standard laboratory temperatures during gestation; G⁺, animals exposed to high temperatures during gestation; L⁻, animals raised in standard laboratory temperatures during lactation; L⁺, animals exposed to high temperatures during lactation; spz, spermatozoa.

^a,bData in the same column that are in a group with a different superscript are different (p value <0.05). Data are expressed as least-squares mean ± standard error of the mean.

Table 2. Sperm motility assessment of male rabbits exposed to high temperatures during pregnancy and postnatal period.

	Motion parameters (determined by computer-assisted semen analysis)
Environmental conditions	VCL (μm s^−1)	VSL (μm s^−1)	VAP (μm s^−1)	LIN (%)	STR (%)	WOB (%)	ALH (μm)	BCF (Hz)
Gestation
G^−	85.2 ± 4.33^a	30.1 ± 1.65^a	51.6 ± 2.81^a	36.3 ± 1.57	59.8 ± 1.92	60.3 ± 1.16	2.5 ± 0.11^a	8.2 ± 0.25
G^+	103.6 ± 4.71^b	35.1 ± 1.80^b	62.3 ± 3.12^b	34.1 ± 1.71	56.2 ± 2.08	60.3 ± 1.26	2.9 ± 0.11^b	8.5 ± 0.27
Lactation
L^−	97.7 ± 3.99	35.7 ± 1.52^a	60.8 ± 2.61	37.4 ± 1.45	59.5 ± 1.76	62.4 ± 1.07^b	2.8 ± 0.10	8.6 ± 0.23
L^+	91.1 ± 4.79	29.3 ± 1.83^b	53.1 ± 3.12	33.8 ± 1.74	56.5 ± 2.12	58.1 ± 1.28^a	2.7 ± 0.10	8.1 ± 0.27
Cross
G^−&L^−	90.3 ± 5.34	33.7 ± 2.04	56.2 ± 3.51	38.3 ± 1.93	60.9 ± 2.35	62.4 ± 1.42	2.7 ± 0.13	8.6 ± 0.30
G^+&L^−	80.1 ± 6.90	25.6 ± 2.65	46.9 ± 4.54	34.2 ± 2.52	58.8 ± 3.07	58.1 ± 1.86	2.3 ± 0.17	7.8 ± 0.39
G^−&L^+	105.2 ± 5.91	38.0 ± 2.26	65.4 ± 3.91	36.6 ± 2.15	58.1 ± 2.61	62.4 ± 1.58	2.9 ± 0.15	8.6 ± 0.33
G^+&L^+	102.0 ± 7.14	32.1 ± 2.72	59.3 ± 4.62	31.8 ± 2.59	54.2 ± 3.15	58.3 ± 1.90	3.0 ± 0.18	8.4 ± 0.41

G⁻, animals raised in standard laboratory temperatures during gestation; G⁺, animals exposed to high temperatures during gestation; L⁻, animals raised in standard laboratory temperatures during lactation; L⁺, animals exposed to high temperatures during lactation; VCL, curvilinear velocity; VSL, linear velocity; VAP, average velocity; LIN, linearity coefficient (calculated as [VSL/VCL] × 100); STR, straightness coefficient; WOB, wobble coefficient (VSL/VAP × 100); ALH, amplitude of lateral movement of the head; BCF, track crossing frequency.

^a,bData in the same column that are in a group with different superscripts are different (p value <0.05). Data are expressed as least-squares mean ± standard error of the mean.

Table 3. Serum testosterone levels of male rabbits exposed to high temperatures during gestation and/or lactation at pubertal age (16 weeks old) and mature, sexually active ages (24 and 36 weeks old).

	Age (weeks)
Environmental conditions	16	24	36
Gestation
G^−	3.1 ± 0.77	2.6 ± 0.85	3.7 ± 0.65
G^+	5.2 ± 0.77	4.8 ± 0.85	3.9 ± 0.65
Lactation
L^−	2.8 ± 0.77^a	2.8 ± 0.85	4.3 ± 0.65
L^+	5.6 ± 0.77^b	4.6 ± 0.85	3.3 ± 0.65
Cross
G^−&L^−	2.8 ± 1.08^a	1.6 ± 1.28	4.6 ± 0.92
G^+&L^−	3.5 ± 1.08^a	3.6 ± 1.28	2.8 ± 0.92
G^−&L^+	2.7 ± 1.08^a	3.6 ± 1.28	4.0 ± 0.92
G^+&L^+	7.7 ± 1.08^b+	6.0 ± 1.28	3.8 ± 0.92

G⁻, animals raised in standard laboratory temperatures during gestation; G⁺, animals exposed to high temperatures during gestation; L⁻, animals raised in standard laboratory temperatures during lactation; L⁺, animals exposed to high temperatures during lactation.

^a,bData in the same column that are in a group with different superscripts are different (p value <0.05). Data are expressed as least-squares mean ± standard error of the mean.

Figure 3. Analysis of testicular histometry and histology of male rabbits exposed to high temperatures during gestation (G⁺&L⁻), lactation (G⁻&L⁺), both gestation and lactation (G⁺&L⁺), and control group (G⁻&L⁻) at pubertal age (16 weeks old) and mature, sexually active ages (24 and 36 weeks old). (A) Histometry: testis weight, length and width. (B) Histology: percentage of seminiferous tubules with presence of lumen, percentage of seminiferous tubules with presence of spermatids and the percentage of seminiferous tubules with presence of spermatozoa.

Table 4. Fertility and prolificacy of male rabbits exposed to high temperatures during pregnancy and postnatal period.

	Environmental	Fertility	Kits born
conditions	n	rate (%)	Total	Alive	Stillborn
G^−&L^−	161	0.91 ± 0.022	8.4 ± 0.38	7.9 ± 0.37	0.5 ± 0.13
G^+&L^+	160	0.89 ± 0.024	8.6 ± 0.38	8.1 ± 0.37	0.6 ± 0.13

G⁻&L⁻, animals raised in standard laboratory temperatures during both gestation and lactation; G⁺&L⁺, animals exposed to high temperatures during both gestation and lactation; n, number of artificial inseminations. Data are expressed as least-squares mean ± standard error of the mean.

Figure 4. Average growth curves estimated with the Gompertz function during the first 36 weeks for male rabbits exposed to high temperatures during gestation (G⁺&L⁻), lactation (G⁻&L⁺), both gestation and lactation (G⁺&L⁺) and control group (G⁻&L⁻).

Table 5. Comparison Gompertz growth curve parameters of male rabbits exposed to high temperatures during pregnancy and the postnatal period weighed weekly from 1 to 36 weeks old.

Environmental	Gompertz parameter
conditions	b	k	a
Gestation
G^−	5.24 ± 0.088	0.228 ± 0.003	3748.2 ± 39.15^a
G^+	5.36 ± 0.100	0.230 ± 0.100	3576.2 ± 44.82^b
Lactation
L^−	5.29 ± 0.097	0.234 ± 0.041	3710.2 ± 43.39
L^+	5.30 ± 0.091	0.224 ± 0.038	3614.2 ± 40.72
Cross
G^−&L^−	5.23 ± 0.133	0.230 ± 0.0051	3822.98 ± 59.29
G^+&L^−	5.25 ± 0.114	0.226 ± 0.0049	3673.3 ± 51.14
G^−&L^+	5.36 ± 0.142	0.238 ± 0.0050	3597.3 ± 63.38
G^+&L^+	5.35 ± 0.142	0.222 ± 0.0050	3555.1 ± 63.38

G⁻, animals raised in standard laboratory temperatures during gestation; G⁺, animals exposed to high temperatures during gestation. L⁻, animals raised in standard laboratory temperatures during lactation; L⁺, animals exposed to high temperatures during lactation; a, b and k are the parameters of the Gompertz function (y = ae^(−be^(−kt)). a can be interpreted as the mature body weigh; b is a timescale parameter related to the initial body weight; k is a parameter related to the rate of maturing (growth rate).

^a,bData in the same column with different superscripts are different (p value <0.05). Data are expressed as least-squares mean ± standard error of the mean.

Table 6. Live weight of male rabbits exposed to high temperatures during pregnancy and postnatal period at pubertal age (16 weeks old) and mature, sexually active ages (24 and 36 weeks old).

Environmental	Age (weeks)
conditions	16	24	36
Gestation
G^−	3352.7 ± 51.90^a	3751.4 ± 57.51^a	3835.1 ± 67.77^a
G^+	3037.1 ± 54.81^b	3518.0 ± 60.74^b	3622.2 ± 71.45^b
Lactation
L^−	3267.1 ± 55.76	3663.7 ± 61.75	3751.4 ± 72.63
L^+	3158.7 ± 50.90	3605.4 ± 56.42	3706.0 ± 66.36

G⁻, animals raised in standard laboratory temperatures during gestation; G⁺, animals exposed to high temperatures during gestation; L⁻, animals raised in standard laboratory temperatures during lactation; L⁺, animals exposed to high temperatures during lactation. Data in the same column that are in a group with different superscripts are different (p value <0.05). Data are expressed as least-squares mean ± standard error of the mean.

Table 7. Comparison carcass traits at 36 weeks old of male rabbits exposed to high temperatures during pregnancy and postnatal period..

Environmental	Traits weight (g)
conditions	CCW	RCW	HW	LvW	KiW	TW	LoW	HPW	MW	BW	SFaW	PFaW
Gestation
G^−	2457.6 ± 68.3^a	2139.7 ± 59.9^a	194.9 ± 10.9	79.1 ± 5.5	17.1 ± 0.5	243.6 ± 13.89	643.6 ± 20.7^a	709.8 ± 14.9^a	272.7 ± 7.3^a	40.8 ± 0.9	37.0 ± 4.1^a	165.2 ± 15.4^a
G^+	2225.6 ± 56.8^b	1905.4 ± 49.8^b	180.7 ± 8.6	75.5 ± 4.6	16.1 ± 0.4	236.3 ± 11.56	580.1 ± 17.1^b	653.0 ± 12.4^b	247.6 ± 6.1^b	38.5 ± 0.7	23.7 ± 3.4^b	111.5 ± 12.8^b
Lactation
L^−	2298.3 ± 66.6	1990.2 ± 58.4	190.1 ± 10.6	79.4 ± 5.4	16.4 ± 0.5	254.8 ± 13.55	588.0 ± 20.2	682.6 ± 14.5	259.2 ± 7.2	40.3 ± 0.9	27.4 ± 4.0	124.9 ± 15.1
L^+	2384.8 ± 58.7	2054.3 ± 51.5	185.5 ± 8.86	75.2 ± 4.8	16.9 ± 0.4	225.2 ± 11.95	635.7 ± 17.8	680.2 ± 12.8	261.1 ± 6.3	39.0 ± 0.8	33.4 ± 4.0	151.8 ± 13.3
Cross
G^−&L^−	2392.7 ± 103.1	2091.7 ± 90.6	195.2 ± 17.0	82.6 ± 8.4	16.7 ± 0.8	261.4 ± 21.00	611.5 ± 31.3	710.4 ± 22.5	271.7 ± 11.1	40.7 ± 1.3	34.4 ± 6.1	151.2 ± 23.4
G^+&L^−	2522.5 ± 89.3	2186.6 ± 78.4	194.6 ± 13.5	75.7 ± 7.2	17.5 ± 0.7	225.8 ± 18.18	675.7 ± 27.1	709.3 ± 19.5	273.6 ± 9.2	40.8 ± 1.2	39.6 ± 5.3	178.8 ± 20.2
G^−&L^+	2204.0 ± 84.2	1888.8 ± 73.9	184.9 ± 12.7	76.3 ± 6.8	16.0 ± 0.6	248.2 ± 17.14	564.5 ± 25.5	654.9 ± 18.4	246.7 ± 9.1	39.9 ± 1.1	20.4 ± 5.0	98.3 ± 19.1
G^+&L^+	2247.1 ± 76.2	1921.9 ± 66.9	176.4 ± 11.5	74.8 ± 6.2	16.3 ± 0.6	224.5 ± 15.51	595.8 ± 23.1	651.1 ± 16.6	248.5 ± 8.2	37.2 ± 1.0	27.1 ± 4.5	124.7 ± 17.2

G⁻, animals raised in standard laboratory temperatures during gestation; G⁺, animals exposed to high temperatures during gestation; L⁻, animals raised in standard laboratory temperatures during lactation; L⁺, animals exposed to high temperatures during lactation. CCW, chilled carcass weight (g); RCW, reference carcass weight (g); HW, head weight (g); LvW, liver weight; KiW (g), kidneys weight (g); TW, thoracic cage weight (g); LoW, loin weight (g); HPW, hind part weight (g); SFaW, scapular fat of chilled carcass weight (g); PFaW, perirenal fat of chilled carcass weight (g). From the hind part a hind leg was carefully dissected to separate bone from the muscle. MW, muscle weight (g); BW, bone weight (g). a,b superscript: Data in the same column that are in a group with different superscript are different (p value <0.05). Data are expressed as least-squares mean ± standard error of the mean.