The mean values (±SD) of P4 and biochemical metabolites concentrations measured during different physiological phases (premating, pregnancy and lactation) in Damascus and crossbred goats are shown in Table 1, 2 and 3.
The P4 concentration (Table 1) increased as gestation progressed and dropped to basal levels after kidding in both groups. The highest levels were registered in late gestation in crossbred does. The significant influence of physiological status (p<0.01, p<0.001) was noted between the premating period and early lactation and stages of pregnancy (early, mid, late) in both groups, while significant differences between goat breeds were observed in early (p<0.01) and mid-gestation (p<0.001).
No significant differences in glycemia were present among the different samples in Damascus goats (Table 2) while it increased significantly in the crossbred group, in late pregnancy compared to mid-gestation. A significantly lower cholesterolemia (p<0.05) was noted at early lactation compared to the premating sample in crossbred goats. For uremia, a significant decrease (Table 3) was recorded in the Damascus group at early lactation compared to pregnancy stages. Triglycerides and creatinine profiles showed no differences between physiological stages. No significant breed effect was noted for all considered biochemical parameters.
Mean serum P4 concentrations were at basal levels (<1 ngml
-1) in both groups before sponge insertion in accordance with earlier studies
(Talebi et al., 2012; Yede et al., 2023), suggesting that goats were in an anestrous period or early estrus (
Pineda, 2003). The significant increase after mating indicated that estrus was efficiently induced in females. The rising trend with gestation advance observed in both groups and the decline to basal levels after kidding were reported earlier
(Kadzere et al., 1996). Since the main site of production of P4 in pregnant goats is the ovary, the irregular increase of progesteronemia observed in literature during gestation may be attributed to the possible differences in corpus luteum composition and activity
(El-Tarabany et al., 2020). On the other hand, the highly significant effect of gestation stage observed on circulatory P4 was previously described by
Sousa et al., (1999). After parturition, P4 dropped to its basal level as a result of corpus luteum regression
(Talebi et al., 2012).
In the current experiment, the significant variation in P4 levels between Damascus and crossbred females at early and mid-gestation may be related to breed in agreement with
Mmbengwa et al., (2009) who referred large variations in P4 concentrations within and between goat breeds and nutritional regimens. The investigations conducted by
Abd El-Hamid et al., (2017) disagreed with these findings. The difference between groups could also be attributed to age, parity, or litter size (
Hussain, 2015;
Madan et al., 2020). According to
Jarrell and Dziuk (1991), progesterone levels seem to be adjusted to the needs of gestation progress rather than the number of corpus luteum or fetuses suggesting great individual variation between females during different reproductive stages.
No significant effect of reproductive status on glycemia was recorded in Damascus does in agreement with
Allaoua et al., (2021). The increasing trend during late pregnancy in crossbred does, also reported in sheep by
Kandiel et al., (2010), indicates increased metabolic needs with advanced pregnancy. Additionally, rising levels noted in early lactating Damascus females compared to high pregnant ones were described earlier but with significant variation
(Cepeda-Palacios et al., 2018). This rise may be related to the elevation of thyroid hormone during lactation which represents an adjustment to mobilize glucose for lactogenesis (
Mbassa and Poulsen,1991), as glucose is the principal precursor of lactose synthesis by mammary epithelial cells
(Kaniamuthan et al., 2022). It may also be ascribed to the recovery of feed intake and the improvement in the energetic status of females after kidding
(Mohammed et al., 2016).
No statistical difference exists between goat breeds’ glycemia during different reproductive stages. In contrast, great variation was reported by
Cepeda-Palacios et al., 2018). The difference could be attributed to age, feed intake, differences in the animal’s metabolism, litter size, season, or region
(Gamit et al., 2019; Khan et al., 2020).
Cholesterol concentrations were not significantly affected by physiological status in Damascus goats which conforms with earlier reports
(Allaoua et al., 2021). On the contrary, crossbred does show lower values in the lactation period (p<0.05) compared to the premating period in line with the findings of
Liotta et al., (2021) and
Berrani et al., (2021). Variations may be due to the direct involvement of cholesterol in reproductive processes and its intensive utilization by the mammary glands for milk synthesis. The difference between both groups may also be explained by the age of the female goats (
Karaşahin et al., 2019). Additionally, there was no significant breed effect on blood cholesterol concentrations which is supported by the results of
Al-Bulushi et al., (2017).
The comparison among the different physiological periods revealed no significant change in TG content in Damascus and Crossbred does. Similar finding was reported by
Jimoh et al., (2019). In contrast,
Abdul-Rahaman et al., (2019) described an increasing profile in pregnant goats compared to non-pregnant ones related to elevated hepatic synthesis or deficient energy intake. No such differences were registered throughout the current experiment suggesting adequate nutrient intake in both groups.
No significant impact of reproductive status on uremia was registered in Crossbred females in support to observations of
Waziri et al., (2010). The marked decline (P<0.05) in early lactating Damascus goats compared to pregnant ones, is compatible with their significantly higher nitrogen requirements
(Madan et al., 2020). However, the results are in contradiction to those previously observed by
Idamokoro et al., (2019), who noted increased levels (P<0.05) in lactating goats, attributed to an altered protein metabolism during the lactation period, or enhanced muscle protein catabolism during the mobilization of body reserves. In addition, the non-significant effect of the breed is consistent with the findings of
Castagnino et al., (2015).
The creatinine results concur with those of
Berrani et al., (2021), who found no significant variation related to the reproductive status. In contrast,
Soares et al., (2018) recorded higher values in pregnant than lactating goats due to increased energy requirement, to maternal mobilization of protein for fetal muscle development and the elimination of the fetal organic residues in maternal circulation. Increased CRE could also be observed in goats after water deprivation
(Abdelatif et al., 2010). This evolution was not shown in the present study suggesting the absence of maternal muscle protein catabolism or water restriction and indicative of the renal health of animals. On the other hand, results demonstrated no significant difference in CRE levels across all the reproductive stages between crossbred and Damascus does. A similar finding was reported by
Abd El-Hamid et al., (2017) in Damascus and Baladi does. On the contrary, reports by
Mohammed et al., (2016) confirmed that creatininemia differs significantly (p≤0.01 respectively) among breeds.
