Seasonal and parity effects on ghrelin levels throughout the estrous cycle in dairy cows

Combined Metabolomics and Biochemical Analyses of Serum and Milk Revealed Parity-Related Metabolic Differences in Sanhe Dairy Cattle

The production performance of dairy cattle is closely related to their metabolic state. This study aims to provide a comprehensive understanding of the production performance and metabolic features of Sanhe dairy cattle across different parities, with a specific focus on evaluating variations in milk traits and metabolites in both milk and serum. Sanhe dairy cattle from parities 1 to 4 (S1, n = 10; S2, n = 9; S3, n = 10; and S4, n = 10) at mid-lactation were maintained under the same feeding and management conditions. The milk traits, hydrolyzed milk amino acid levels, serum biochemical parameters, and serum free amino acid levels of the Sanhe dairy cattle were determined. Multiparous Sanhe dairy cattle (S2, S3, and S4) had a greater milk protein content, lower milk lactose content, and lower solids-not-fat content than primiparous Sanhe dairy cattle (S1). Moreover, S1 had a higher ratio of essential to total amino acids (EAAs/TAAs) in both the serum and milk. The serum biochemical results showed the lower glucose and total protein levels in S1 cattle were associated with milk quality. Furthermore, ultra-high-resolution high-performance liquid chromatography with tandem MS analysis (UPLC-MS/MS) identified 86 and 105 differential metabolites in the serum and milk, respectively, and these were mainly involved in amino acid, carbohydrate, and lipid metabolism. S1 and S2/S3/S4 had significantly different metabolic patterns in the serum and milk, and more vitamin B-related metabolites were significantly higher identified in S1 than in multiparous cattle. Among 36 shared differential metabolites in the serum and milk, 10 and 7 metabolites were significantly and strongly correlated with differential physiological indices, respectively. The differential metabolites identified were enriched in key metabolic pathways, illustrating the metabolic characteristics of the serum and milk from Sanhe dairy cattle of different parities. L-phenylalanine, dehydroepiandrosterone, and linoleic acid in the milk and N-acetylornithine in the serum could be used as potential marker metabolites to distinguish between Sanhe dairy cattle with parities of 1-4. In addition, a metabolic map of the serum and milk from the three aspects of carbohydrates, amino acids, and lipids was created for the further analysis and exploration of their relationships. These results reveal significant variations in milk traits and metabolites across different parities of Sanhe dairy cattle, highlighting the influence of parity on the metabolic profiles and production performance. Tailored nutritional strategies based on parity-specific metabolic profiles are recommended to optimize milk production and quality in Sanhe cattle.

Metabolic Changes in Serum and Milk of Holstein Cows in Their First to Fourth Parity Revealed by Biochemical Analysis and Untargeted Metabolomics

The performance of dairy cows is closely tied to the metabolic state, and this performance varies depending on the number of times the cows have given birth. However, there is still a lack of research on the relationship between the metabolic state of Holstein cows and the performance of lactation across multiple parities. In this study, biochemical analyses and metabolomics studies were performed on the serum and milk from Holstein cows of parities 1-4 (H1, N = 10; H2, N = 7; H3, N = 9; H4, N = 9) in mid-lactation (DIM of 141 ± 4 days) to investigate the link between performance and metabolic changes. The results of the milk quality analysis showed that the lactose levels were highest in H1 (p = 0.036). The total protein content in the serum increased with increasing parity (p = 0.013). Additionally, the lipase activity was found to be lowest in H1 (p = 0.022). There was no difference in the composition of the hydrolyzed amino acids in the milk among H1 to H4. However, the free amino acids histidine and glutamate in the serum were lowest in H1 and highest in H3 (p < 0.001), while glycine was higher in H4 (p = 0.031). The metabolomics analysis revealed that 53 and 118 differential metabolites were identified in the milk and serum, respectively. The differential metabolites in the cows' milk were classified into seven categories based on KEGG. Most of the differential metabolites in the cows' milk were found to be more abundant in H1, and these metabolites were enriched in two impact pathways. The differential metabolites in the serum could be classified into nine categories and enriched in six metabolic pathways. A total of six shared metabolites were identified in the serum and milk, among which cholesterol and citric acid were closely related to amino acid metabolism in the serum. These findings indicate a significant influence of blood metabolites on the energy and amino acid metabolism during the milk production process in the Holstein cows across 1-4 lactations, and that an in-depth understanding of the metabolic changes that occur in Holstein cows during different lactations is essential for precision farming, and that it is worthwhile to further investigate these key metabolites that have an impact through controlled experiments.

Effects of Rumen-Protected L-Tryptophan Supplementation on Productivity, Physiological Indicators, Blood Profiles, and Heat Shock Protein Gene Expression in Lactating Holstein Cows under Heat Stress Conditions

In this study, we examined the effects of rumen-protected L-tryptophan supplementation on the productivity and physiological metabolic indicators in lactating Holstein cows under heat stress conditions. The study involved eight early lactating Holstein cows (days in milk = 40 ± 9 days; milk yield 30 ± 1.5 kg/day; parity 1.09 ± 0.05, p < 0.05), four cows per experiment, with environmentally controlled chambers. In each experiment, two distinct heat stress conditions were created: a low-temperature and low-humidity (LTLH) condition at 25 °C with 35-50% humidity and a high-temperature and high-humidity (HTHH) condition at 31 °C with 80-95% humidity. During the adaptation phase, the cows were subjected to LTLH and HTHH conditions for 3 days. This was followed by a 4-day heat stress phase and then by a 7-day phase of heat stress, which were complemented by supplementation with rumen-protected L-tryptophan (ACT). The findings revealed that supplementation with ACT increased dry matter intake as well as milk yield and protein and decreased water intake, heart rate, and rectal temperature in the HTHH group (p < 0.05). For plateletcrit (PCT, p = 0.0600), the eosinophil percentage (EOS, p = 0.0880) showed a tendency to be lower, while the monocyte (MONO) and large unstained cells (LUC) amounts were increased in both groups (p < 0.05). Albumin and glucose levels were lower in the HTHH group (p < 0.05). The gene expressions of heat shock proteins 70 and 90 in the peripheral blood mononuclear cells were higher in the ACT group (HTHH, p < 0.05). These results suggest that ACT supplementation improved productivity, physiological indicators, blood characteristics, and gene expression in the peripheral blood mononuclear cells of early lactating Holstein cows under heat-stress conditions. In particular, ACT supplementation objectively relieved stress in these animals, suggesting that L-tryptophan has potential as a viable solution for combating heat-stress-induced effects on the cattle in dairy farming.

The Role of the Gastric Hormones Ghrelin and Nesfatin-1 in Reproduction

Ghrelin and nesfatin-1 are enteroendocrine peptide hormones expressed in rat X/A-like and human P/D1cells of the gastric mucosa. Besides their effect on food intake, both peptides are also implicated in various other physiological systems. One of these is the reproductive system. This present review illustrates the distribution of ghrelin and nesfatin-1 along the hypothalamus–pituitary–gonadal (HPG) axis, their modulation by reproductive hormones, and effects on reproductive functions as well as highlighting gaps in current knowledge to foster further research.

The Role of the Gastric Hormones Ghrelin and Nesfatin-1 in Reproduction

Ghrelin and nesfatin-1 are enteroendocrine peptide hormones expressed in rat X/A-like and human P/D1cells of the gastric mucosa. Besides their effect on food intake, both peptides are also implicated in various other physiological systems. One of these is the reproductive system. This present review illustrates the distribution of ghrelin and nesfatin-1 along the hypothalamus-pituitary-gonadal (HPG) axis, their modulation by reproductive hormones, and effects on reproductive functions as well as highlighting gaps in current knowledge to foster further research.

The Role of the Gastric Hormones Ghrelin and Nesfatin-1 in Reproduction

Ghrelin and nesfatin-1 are enteroendocrine peptide hormones expressed in rat X/A-like and human P/D1cells of the gastric mucosa. Besides their effect on food intake, both peptides are also implicated in various other physiological systems. One of these is the reproductive system. This present review illustrates the distribution of ghrelin and nesfatin-1 along the hypothalamus–pituitary–gonadal (HPG) axis, their modulation by reproductive hormones, and effects on reproductive functions as well as highlighting gaps in current knowledge to foster further research.

Age, gestational and heat stress effects on ghrelin secretion in dairy cattle

It is known that heat stress decreases dry matter intake in cattle with impacts on milk production and fertility. Ghrelin is an orexigenic hormone with suppressive effects on reproduction. In this study, we investigated the effects of heat stress and gestational status on ghrelin secretion and its possible associations with DMI in Holstein cattle. The study was conducted in a dairy farm without any artificial cooling measures. The animals were fed a total mixed ration twice daily; each morning the leftovers were removed and weighted. Lactating cows and heifers were used during the winter and the summer; in each season 8 groups were formed as following: non-pregnant cows (n = 10) and non-pregnant heifers (n = 10) and pregnant cows (3 groups, each n = 8) and heifers (3 groups, each n = 10), being at the 1st (days 65-90), the 2nd (days 114-144) and the 3rd (dry cows, days 198-220; heifers, days 192-230) trimester of gestation. In each season the blood samples were collected from all groups on the same day, 1 h prior to morning feeding. In the winter, the Temperature Humidity Index (THI) was 58 in the winter and 73 in the summer. Normal and acidified sera were stored at -20 °C and analyzed for cortisol, total and acylated ghrelin concentrations, respectively. T-Test and Welch-Satterthwaite were performed for continuous data comparison, while two-way ANOVA to test for differences between gestation and season. Feed refusals were higher (p < 0.01) during the summer compared to the winter. In cows, total ghrelin levels differed between gestation stages in winter and summer(p < 0.04), while acylated ghrelin levels differed by gestation stage in winter (p < 0.001) but not in summer. There was an effect of season by the gestational stage in the pattern of acylated (p < 0.001) but not of total ghrelin. In heifers, the pattern of total and acylated ghrelin secretion was not affected by season or gestation stage (p > 0.05). Both in cows and heifers, acylated ghrelin levels were lower in summer compared to winter, (p < 0.002). During the summer months the low ghrelin levels might explain the reduced feed consumption of heat stressed animals. We infer that the lactation-induced altered metabolic status of the animals governed the different ghrelin levels at various gestational stages in cows and heifers.

Cooling management effects on dry matter intake, metabolic hormones levels and welfare parameters in dairy cows during heat stress

This research paper addresses the hypothesis that intensive cooling management during the summer improves the secretion of metabolic hormones in dairy cows. To test this hypothesis, we characterized the effect of different cooling managements on the different ghrelin isoforms and leptin secretion of 20 Israeli-Holstein dairy cows during 5 weeks during heat stress. The cows were divided into two groups: one was exposed to 5 cooling sessions per day (5 CS) and the other to 8 cooling sessions per day (8 CS). Blood was collected and leptin and ghrelin isoforms level were radioimmunoassayed. Analysis of the interaction between coolings and the week of the experiment showed that the 8 CS group consumed more food and produced more milk, although neither difference was statistically significant. In addition, the 8 CS group exhibited higher blood levels of acyl-ghrelin and leptin as compared to the 5 CS group. Conversely, the blood levels of total ghrelin were lower in the cows exposed to 8 CS as compared to cows from the 5 CS treatment. Furthermore, a significant correlation was found only between total ghrelin levels and the weeks, but not with other parameters examined. We further compared digestibility as well as stress parameters between the groups. We found that the 8 CS group cows ruminated and lay down more hours during a day and simultaneously had better activity time. No significant difference was detected between groups in milk yield and digestibility parameters. Our results suggest that intensive cooling management during the hot season influences the levels of metabolic hormones in the circulation and helps to mitigate the detrimental effect of heat stress on dairy cow welfare and production.

Days-in-Milk and Parity Affected Serum Biochemical Parameters and Hormone Profiles in Mid-Lactation Holstein Cows

It is well known that serum biochemical parameters and hormones contribute greatly to the physiological and metabolic status of dairy cows. However, few studies have focused on the variation of these serum parameters in multiparous mid-lactation cows without the interference of diet and management. A total of 287 Holstein dairy cows fed the same diet and maintained under the same management regime were selected from a commercial dairy farm to evaluate the effects of days-in-milk (DIM) and parity on serum biochemical parameters and hormone profiles. Milk yield and milk protein content were affected by DIM and parity (p < 0.05). Milk protein yield showed a numerically decreasing trend with parity, and it was relatively constant in cows with parities between 2 and 4 but lower in cows with parity 6 (p = 0.020). Ten and five serum biochemical parameters related to protein status, energy metabolism, liver and kidney function, and oxidative stress were affected by DIM and parity, respectively (p < 0.05). Glucagon, insulin-like growth factor 1 concentration, and the revised quantitative insulin sensitivity check index were significantly different (p < 0.05) among cows with different DIM. Parity had no effect on hormone concentrations. An interaction between DIM and parity effect was only detected for glucagon concentration (p = 0.015), which showed a significantly increasing trend with DIM and overall decreasing trend with parity. In summary, DIM and parity played an important role in affecting the serum biochemical parameters and/or hormones of dairy cows, with serum parameters affected more by DIM than parity.

A study on ghrelin and LH secretion after short fasting and on ghrelin levels at perioestrual period in dairy cattle

In two experiments, we studied (a) the changes of LH secretion in heifers under different feeding schedules and (b) total ghrelin concentration at oestrus in cows and heifers. In experiment one, synchronized heifers were allocated in three groups (R, regularly fed controls; F, fasted; and F-F fasted-fed). One day after the completion of the oestrous induction protocol, group F and F-F animals stayed without feed for 24 hr; thereafter, feed was provided to R and F-F cattle; 2 hr later, GnRH was administered to all animals. Blood samples were collected for ghrelin, progesterone, LH and cortisol concentrations. Fasting caused increased ghrelin concentrations in groups F and F-F, while in response to GnRH, LH surge was significantly attenuated in groups F and F-F compared to R. In experiment 2, lactating cows and heifers were used. On day 9 of a synchronized cycle, PGF2α was administered, and blood samples were collected twice daily until the third day after oestrus and analysed for progesterone, estradiol, ghrelin, glucose and BHBA concentrations. No difference was recorded between groups in steroids and BHBA concentrations. In comparison to mid-luteal values, ghrelin concentrations significantly increased at perioestrual period in cows, but not in heifers. This study provides evidence that starving-induced elevated ghrelin concentrations can have suppressing effect on LH secretion, even after ghrelin's restoration to basal values and that during oestrus, ghrelin secretion is differently regulated in cows and heifers, likely being independent from oestradiol concentrations. Further research is required to identify the determining factors that drive the different regulation of ghrelin secretion in cows and heifers.

On the Molecular Evolution of Leptin, Leptin Receptor, and Endospanin

Over a decade passed between Friedman's discovery of the mammalian leptin gene (1) and its cloning in fish (2) and amphibians (3). Since 2005, the concept of gene synteny conservation (vs. gene sequence homology) was instrumental in identifying leptin genes in dozens of species, and we now have leptin genes from all major classes of vertebrates. This database of LEP (leptin), LEPR (leptin receptor), and LEPROT (endospanin) genes has allowed protein structure modeling, stoichiometry predictions, and even functional predictions of leptin function for most vertebrate classes. Here, we apply functional genomics to model hundreds of LEP, LEPR, and LEPROT proteins from both vertebrates and invertebrates. We identify conserved structural motifs in each of the three leptin signaling proteins and demonstrate Drosophila Dome protein's conservation with vertebrate leptin receptors. We model endospanin structure for the first time and identify endospanin paralogs in invertebrate genomes. Finally, we argue that leptin is not an adipostat in fishes and discuss emerging knockout models in fishes.