Hair characteristics and cortisol hair analysis as indicators of fertility in dairy cows

S Lamari, T Madani and L Allouche¹

Department of Agronomy Faculty of Nature and Life Sciences, University of Ferhat Abbas (Sétif), Algeria
lamarisara@gmail.com
¹ Département of Biology and Animal Physiology, Faculty of Nature and Life Sciences, University of Ferhat Abbas, (Sétif), Algeria

Abstract

Our study investigates the relationship between hair and coat characteristics, hair cortisol level, and fertility of 28 Fleckvieh and 67 Montbéliarde cows during hot and cold season in a commercial farm. The following characteristics of hair and coat have been measured: hair weight (W), hair length (L), hair diameter (HD), hair medullar diameter (MD), number of hairs per unit area (N), percentage of white coat color (C %) and hair cortisol level (C). Fertility parameters were estimated: interval from calving to first service (ICS), services per conception (SPC), and interval from calving to conception (IC). In Montbéliarde breed, HD was negatively correlated with SPC in winter (r = - 0.34, p=0.01) indicating that Montbéliarde cows, with large total hair diameter, required reduced number of SPC to be pregnant, while in summer hair coat traits were not correlated with all fertility parameters. In Fleckvieh cows, coat color was correlated with ICS and IC (r=0.67, p=0.02; r=0.60, p=0.04, respectively) during summer and with SPC during winter (r=0.86, p=0.01). No association between hair cortisol level and fertility was observed. Proportion of white color in Fleckvieh cows significantly affected fertility. These results indicate that reproductive efficiency parameters were related to coat characteristics; this association was more expressed in Fleckvieh than in Montbéliarde breed. Also, possibility exists to select more adapted animals to our warm climate regions : Montbeliarde cows with large hair diameters, Fleckvieh cows with large white surface.

Keywords: Algeria, cold season, hair coat, hot season

Introduction

Heat stress can reduce fertility in cattle (Ealy et al 1993; Ryan et al 1992). The mechanism by which heat stress causes embryonic mortality is multifactorial, as heat stress can alter several aspects of reproductive physiology, including blood flow to the reproductive tract (Roman-Ponce et al 1977), and ovarian steroid concentrations ; similarly, increased culture temperatures can compromise fertilization rate. To better clarify the physiological adaptations of dairy cows in the semiarid climate, it seemed interesting to follow the reproduction of cows and changes in the activity of the adrenal glucocorticoid versus the axis during a reproductive hypophyso gonadic cycle. Body surface traits of cattle are of great importance as for the relationships between the animals and their ambience. In semi arid regions, animals must be able to dissipate the heat excess through the skin and from the respiratory surfaces. At the same time they must avoid thermal energy incoming from the environment. The protective properties depend on the morphological characteristics of the skin (color) and of the hair coat (thickness, number of hairs per unit area, diameter of the hairs, length of the hairs),which allow to exchange heat with the environment (DaSilva 2000). Therefore, genetic progress towards a hair coat, appropriate for hot and humid environments, could be a strategy to enhance reproductive function of cows in Algeria. The present study was about the relationship between characteristics of hair coat, hair cortisol level and reproduction of Fleckvieh and Montbéliarde cows during two seasons, hot (summer) and cold (winter) seasons.

Materials and methods

Animals

This work was conducted from August 2012 to August 2013 on 95 dairy cows comprising two breeds, 28 Fleckvieh and 67 Montbéliarde cows reared in a commercial dairy farm. Animals were primiparous and multiparous cows and in different stages of the reproductive cycle, without any visible signs of clinical disease. Cows were separated into two groups according to month of mating. Detection of estrus was made by sires and natural service was preferred by the manager. Individual records included cow identification number, parity, dates of natural services and calving dates for all cows. Three fertility parameters were estimated: interval from calving to first service (ICS), interval form calving to conception (IC) and number of services per conception (SPC).

Sampling and morphological characteristics of hair coat

Measurements of percentage of white coat color (C%) were carried out and hair sampling as well. To obtain the percentage of white color relative to the body surface area, pictures were taken using a digital camera. Then the pictures were transferred to special software (IPWin32) to estimate, at the same magnification, both sides of each animal, except the tail, head, legs, and belly regions, according to the method of Becerril and Wilcox (1992).

Hair samples were taken from the center of the thorax of each animal about 20 cm below the dorsal line by means of an electrician’s pliers adapted in such a way that all the hairs in an 1 cm² area could be plucked out (DaSilva et al 1988; Silva 2000a). Hair samples were stored in plastic envelopes and measurements [hair weight (W), hair length (L); number of hairs per unit area (N), hair total diameter (HD), diameter of hair medulla (MD)] were done later in the laboratory. The average hair length (mm) of each sample was calculated from the 20 longest hairs of the sample by using a thin metal ruler, according to the method of Udo (1978) ; number of hairs (hairs/cm²) was obtained by direct counting of all hairs present in the sample ; an ocular micrometer scale of microscope (Leica DM1000) was used to measure hair total diameters and medullar hair diameters (μm) of the same hairs used for length measurement, to about 10 µm of the hair root.

Hormone analysis

Samples were taken from the scapula (shoulder) in August and February respectively for summer and winter seasons. On the scalp, hair growth rate is between 0.2 mm/day and 1.12 mm/day, or 6 to 33.5 mm/ month (Harkey 1993). In order to avoid the effect of calving stress on level of cortisol, only animals that calved more than one month before hair sampling were included in the study. Hair samples were stored in dry conditions at room temperature in the dark, until analysis. To prepare the hair samples, 250 mg hair samples were weighted and washed twice in 9 ml polypropylene tubes containing 5 ml methanol (Sigma-Aldrich), as proposed by Davenport et al (2006), and then the samples were gently mixed on a rotator at room temperature for 3 min per wash. The hair was then allowed to dry for approximately 5 days (Paulsen et al 2001), then weighed and minced into 3-4 mm pieces with fine scissors. To extract cortisol, 50 mg of hair were placed in a glass vial with 3 ml of methanol for 18h at 37° C. Samples were then centrifuged (15 min/1000 rpm) in a centrifuge (Hettich EBA 20) as suggested by Comin et al (2013), and the supernatant collected and transferred to a glass test tube. The supernatant (0.6 ml) was taken from the top, and aliquot was dried using a dry bath SBH200D / 3 Stuart at 37 ° C (Davenport et al 2006; Bennett and Hayssen 2010) and reconstituted with 0.3 ml of phosphate buffer. The samples were analyzed for cortisol using a commercially available enzyme-linked immunosorbent assay (ELISA) (Human), in duplicates. The average inter- and intra-assay CV was 4.65% and 9.86%, respectively.

Statistical analysis

The mean and standard deviation were calculated and the test for normality (Kolmogorov-Smirnov) was performed for all parameters. Correlation was used to estimate the relationship between characteristics of hair coat, cortisol concentration and reproduction parameters using Pearson correlation, and Spearman’s correlation rank when variables were not normally distributed. All statistical analyses were performed using the SPSS package program, version 21.

Results

Changes in hair coat characteristics and cortisol concentration are summarized in Table 1 and 2. In summer (Table 1), Fleckvieh cows showed low density coat (394 hairs/cm²); longer hairs (16.5 mm); large hair and medulla hair diameter (88.5; 57.5 μm respectively ) and colored coat (32,6%). However, Montbéliarde cows presented white coat (42.5%), with short hairs (15.8 mm) and many hairs (415 hairs/cm ²) little hair and medulla hair diameter (83.8; 49.5 μm respectively). The cortisol concentration of the hair of both breeds was comparable during this season (table 1).

According to the Table 2, the phenotype of the cows (Montbéliarde and Fleckvieh) of the winter season was characterized by a decrease compared to the warm season, the density of the hairs and the cortisol concentration with a higher concentration in Fleckvieh (16.1±3.0 ng / ml).

Table 3 depicts correlations between hair coat traits in summer and winter seasons of Montbéliarde and Fleckvieh breeds and reproduction efficiency parameters. For Montbéliarde breed, HD was negatively correlated with SPC (r = - 0.34, p<0.05) in winter indicating that Montbéliarde cows, with large total hair diameter, required reduced number of SPC to be pregnant, while in summer hair coat traits were not correlated with all fertility parameters. For Fleckvieh cows, coat color was correlated with ICS and IC (r=0.67, p<0.05 ; r=0.60, p<0.05 respectively) during summer, while association was observed only between C% and SPC (r = 0.86, p=0.01) in winter.

Discussion

The overall mean and standard error of the hair coat characteristics, showed that the cows had a large proportion of white hairs and had a thin coat with short hairs and many number of hair per cm² in summer and the opposite in winter. Bertipaglia et al (2005) reported Holstein coats having average low thickness (2.64 mm), low density (1050 hairs/cm²), with short (12.8 mm), thick hairs (63 μm); these findings were interpreted as indicating successful adaptation to the hot conditions in the State of São Paulo, Brazil.

The results indicate that reproductive efficiency parameters are related to coat characteristics. Coat cover affects temperature regulation and fertility of temperate climate breeds when transposed to warm climate regions (Turner 1964). Our results also showed that Fleckvieh cows, presented significantly correlated between coat color and ICS and IC respectively during summer, in addition an association between C% and SPC in winter. On the other hand Montbéliarde cows, with large total hair diameter, required reduced number of SPC to be pregnant, while in summer hair coat traits were not correlated with all fertility parameters. The association was more expressed for Fleckvieh than for Montbéliarde breed. Fleckvieh cows with light colored coat had significant lower fertility, particularly during hot and dry season. Becerril et al (1993) observed negative, but no significant regression coefficient, for Holstein cows reared under sub tropical climate, while King et al (1988) observed, during winter months, that white Holstein cows required fewer services per conception and had fewer open days than black cows. But Maia et al (2003) showed that traits of black hair coat were different from that of the white hair coat. Black hair coat was less dense, with shorter and ticker hair fibres in order to ease the heat dissipation, while the white hair coat was denser with longer hairs, which favored protection against direct solar radiation. Differences in environmental conditions and management were probably the causes of the differences reported.

Conclusion

• The study of the relationship between hair cortisol level, hair and coat characteristics and fertility of Montbéliarde and Fleckvieh cows in semi- arid area shows that cows with thicker hairs during cold season were associated to improved number of mating per conception for Montbéliarde breed, suggesting that the difference was probably generated by the ability of cows to be more adapted to cold season, although the correlation coefficient was moderate.
  
  
• Fleckvieh cows with light colored coat had significant lower fertility, particularly during hot and dry season.
  
  
• Our results suggest the possibility to incorporate certain characteristics of the hair in the selection animals to facilitate their adaptation to this type of local environment. The characteristics to select here could be: Montbeliarde cows with large hair diameters, Fleckvieh cows with small white surface for the best reproduction performance.

Acknowledgment

The authors acknowledge the efforts of all the personnel of the farm who spared their valuable time and participate fully in data collection without which this work would not have been possible.

References

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Received 18 January 2018; Accepted 14 February 2018; Published 1 March 2018

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