Evaluation of milk productivity of Sahraoui and Targui dromedaries and growth of calves in South-East Algeria

S Kadri, M Karabi¹, A Adamou and H Senoussi

Laboratoire de Bioressources Sahariennes, Préservation et Valorisation
Kadri.soumeya3@gmail.com
¹ Laboratoire de Biogéochimie des Milieux Désertiques Université Kasdi Merbah, Faculté des Sciences de la Nature et de la Vie - Ouargla, 30.000 Algérie

Abstract

In order to evaluate the performance of the two main populations of Algerian dromedary camels in terms of milk productivity, lactation curve parameters, and growth of calves, 10 Sahraoui and 10 Targui multiparous dairy she-camels (Camelus dromedarius) were managed under similar semi-intensive management over a fixed 455 days (about 15 months) of lactation. To estimate the lactation curve components, the biweekly milk yield was regressed on the lactation period according to Wood’s equation. To examine the growth performance of their offspring, 20 camels’ calves, 10 Sahraoui and 10 Targui, were studied. The obtained records were subjected to a T-test to evaluate the effect of the she-camels’ type on production performance, lactation curve parameters, and growth of calves. The lactation performance of Sahraoui and Targui she-camels as well as the growth rate of their calves were statistically similar (p˃0.05). The overall mean values were milk yield, 2589 ± 248 L; daily milk yield, 6.16 ± 0.60 L; lactation length (fixed), 455 days; persistency, 90 %; and the number of days to hit peak yield, 103. Regarding the incomplete gamma function, the overall means of initial milk yield (a), the increasing rate (b) and the decreasing rate (c) were (1.74 ± 0.07), (0.4 ± 0.1) and (0.004 ± 0.001), respectively. The resultant overall value of the determination coefficient (R2) obtained between actual milk production and predicted milk production was 0.64 ± 0.04. On average, for both types of camels (n = 20), the birth weight of the calves was 41.0 ± 2.2 kg. With a daily growth rate of 408 ± 9 g, the calves gained 124 ± 4 kg in 304 days. This study showed the great production potential that the populations of Algerian dromedary camels represent. Those production performances can be further increased under optimal feeding and management conditions.

Key words: growth rate, lactation curve, milk performance, Ouargla, semi-intensive management

Introduction

As a great producer and a meagre consumer, the dromedary contributes in its own way to the protection of its environment and plays a providential role in the food security of Saharan communities (Kadri et al 2020). In these arid regions, where other species are affected by heat and the lack of water and food, camelids (dromedaries) occupy a major place in the supply of these areas' vital products, especially meat and milk.

In Algeria, faced with climate change and socio-economic changes, for the past thirty years we have witnessed an increase in the numbers of camels in arid and semi-arid regions after several decades of decline (Senoussi et al 2017). Algeria has indeed marked an increase in number over the period 2000-2020, to count about 435 200 head in 2020 (FAO stat 2022). Although the valuation of dromedary camel breeding products in Algeria could strongly contribute to strengthening food security in the Saharan regions. Milk has never been valued before; it was shared between the calves and the breeder’s family, or simply offered for free. However, in recent years, we have seen the establishment of small farms using the dromedary as a dairy animal following a strong demand from consumers who buy it mainly for its health claims (Adamou 2008). The increased interest in camel milk in a more urbanized world has boosted research activities on dairy camel selection (Faye 2018). Overall, a number of data on milk production from this animal are reported in the literature. They indicate that the quantities of milk per lactation vary according to the breeds considered, the stages of lactation and the farming systems (Faye 2004).

However, in Algeria, we do not have precise information on the dairy potential of the Algerian she-camel. Few comprehensive studies on lactation production are available (Chehma 2004). Most of the research work on the dairy potential of Algerian she-camels is based on either occasional surveys or estimates due to the fact that, in an extensive system, it is difficult, if not impossible, to follow the production of constantly moving animals.

In order to better our knowledge and have an idea of ​​the potential of dromedary camels reared in Algeria, many studies have been carried out on the characterization of local populations over the last 20 years, which have focused on their phenotypic and morphometric variability (Oulad Belkhir et al 2013, Babelhadj et al 2016a, Meghelli et al 2020). Our work aims to deepen the knowledge of Algerian dromedary camels by carrying out a characterization of the productivity performance of the two main populations of Algerian dromedary camels (Targui and Sahraoui) through: (i) the evaluation of milk production performance of lactating dromedary she-camels reared under semi-intensive conditions and the estimation of the lactation curve parameters of both populations; (ii) an assessment of their calves' growth rate and daily gain. This work is essential for the development of any strategy for the exploitation and sustainable conservation of the species.

Material and methods

Study area

The study was conducted at a private dairy farm located in the peri-urban area of the Ouargla region at 31°57'27" N and 5°19'40" E (south-eastern Algeria, 820 km from the capital Algiers).

Animals and management

Twenty lactating dromedary camels were used in this study. They were divided into two equal groups (Sahraoui and Targui types) of 10 animals. The she-camels were 5–22 years old, had a parity of 1–8 and had a mean live body weight of 444 ± 50 kg. A plastic number tag placed around the neck identified each of the selected females. The two herds were housed in open-air pens where they were reared under semi-intensive management and subjected to the same feeding conditions. Just after the morning milking at 5:00, the animals were brought to pasture (07:00 to 18:00 h) at a low stocking rate (approximately one camel per 13 ha) and allowed to browse the available plants. The dominant vegetation species of the natural pasture are halophyte species (Cornulaca monacantha, Ouednya africana, Stipagrostis pungens, Randonia africana and Zygophylum album). At sunset (18:00h), the she-camels and their calves returned to the shelters, where they were fed with straw and a commercial feed concentrate mixture composed of 60% barley and 40% wheat bran at a flat rate of 2 kg /head/day. Free access to clean water was provided ad-libitum by a water tank.

Milking practice and data collection

In order to estimate the daily milk yield, camels were milked biweekly between January 2019 and March 2020. The milk was only given to the calves during 25 days after birth. The initial milk samples were collected at 25 days postpartum and continued for about 14 successive months. So the milk production was followed about 15 months. All camels were hand milked using a clean container after stimulation by the calf for a few seconds, and then the calves were removed. The volume of extracted milk was then measured using a graduated cylinder. The calves were separated from their mothers for 13 hours each day. Milking was done on two quarters (one posterior and one anterior). The two udders were completely emptied, leaving the remaining two to be suckled by the calf, and the volume collected was doubled. 560 records were used in the present study. From this data, the total milk production, lactation length, and daily milk production were calculated.

Camel calves’ growth rate

To assess the weight growth of calves in relation to lactation, twenty (20) camel calves (born during the months of December to January 2019 were selected on the first day of birth. With consideration of type (Sahraoui and Targui), they were divided equally into two comparable groups. The initial weight of calves was recorded just after birth, and then weighing was performed every two months until ten months of age, as the restraining of the calves had become very difficult. Calves’ weights were determined using a digital weighing scale. Calves begin grazing the grass around the age of eight weeks.

Estimation of the lactation curve

To describe the lactation curve, the incomplete gamma function was used according to Wood’s equation (Wood, 1967).

Y_t = a t ^b e ^{– c t}

Where:

Y_t: is the milk yield at day t

t: number of days

a: is linked to initial milk yield

b: slope of increase milk yield before peak yield

c: slope of decrease milk yield after peak yield.

From the lactation parameters (a, b, and c), the lactation curve was fitted and several lactation curve characteristics were estimated, including the following (Wood 1967):

Time of peak milk yield (T) = b/c

Peak yield (Py) = a (b/c) ^b e^−b

Persistency (P) = − (b + 1) ln (c)

The percentage of persistence was calculated using the following formula (Musaad et al 2013):

PP=[1-((Ym -Y455) * (30d/dbt))/Ym] * 100

Where PP is percentage persistency, y_m is daily milk yield at peak lactation, y₄₅₅ is milk yield at the end of lactation, 30d is 1 month, and dbt is the number of days between tests.

The determination coefficient (R²) was obtained for each animal between actual milk production and predicted milk production by the curve components.

Statistical analysis

Data from the current study were analyzed using the Statistical Package for Social Sciences (IBM SPSS Statistics v 26). Milk yield, lactation curve, and growth rate of camel calves were classified based on camel type. A T-test was used to compare the data for independent samples was performed.

Results and discussion

Table 1 shows that the similarity of the both she-camel groups (Sahraoui and Targui) in the total milk yield, lactation length, and daily milk yield indicated that there were no significant differences (p˃ 0.05) between the two she-camel groups.

The overall average daily milk yield was about 6.16 ± 0.59 L. The average total milk production was an average of 2589 ± 248 L for 455 days of lactation (fixed), with a range between 1634 and 3035 L.

Similarly, these observations are in agreement with the findings of Zayed et al (2014) who studied the milk production traits and lactation curve parameters of three types of Sudanese dromedary she-camels and concluded that the three types of camel had the same potential for milk production. Some authors claim, based on molecular genetic analyzes of camels and dromedaries, that there would be few racial differences between large camelids within a given species (Jianlin et al 2000).

The overall means of total milk yield and daily milk yield in our study were comparable to those reported by Bakheit et al (2008). In contrast, the findings of the present study were higher than the recorded figures by Ishag et al (2017) who reported that the average total milk yield, daily milk yield, and lactation length of the camel population in Sudan in a semi-intensive system were 907 L, 2.8 L, and 327 days, respectively.

According to Faye (1997), the lactation length varies between 8 and 18 months and seems to depend on some practices such as the feeding conditions and frequency of milking. However, in this study, the lactation period was dependent on the weaning age under the controlled conditions (Elkhider and Makkawi 2016). Indeed, among the management practices used on the farm was the induced weaning of camel calves. At 455 days (approximately 15 months), all calves were separated from their dams, who were pregnant again. These were conducted in grazing husbandry and replaced with a new herd of lactating she-camels who had just calved. Consequently, this system of alternation makes it possible to have milk and calves every year. This finding is in agreement with Baloch (2001), who noted that the lactation period in Pakistan was 450 days.

Lactation curve parameters and characteristics

Table 2 shows the initial milk yield (a), the slope of increased milk yield before peak yield (b), the slope of decreased milk yield after peak yield (c) and the determination coefficient (R²⁾. The results revealed that the lactation curve’s parameters of the two she-camel types were all statistically non-significant (p˃ 0.05). Regarding the incomplete gamma function, the overall means of a, b, and c parameters were 1.74 ± 0.07, 0.44 ± 0.09 and 0.004 ± 0.0007, respectively.

The present parameters of the average lactation curve are in line with the findings of Jemmali et al (2016), who studied the milk yield and modeling of lactation curves of Tunisian she-camel.

In this study, the coefficient of determination (R²) was 0.64 ± 0.04. Ishag et al (2017) recorded the same results.

Regarding the lactation curve characteristics in this study, the overall average time (in days) to hit peak yield of 8.86 L was 110 days postpartum. Kamoun et al (2012) cited that peak production happened roughly between the 3rd and 4th months of lactation. The present result was higher than that of Zayed et al (2014). The present persistency and the average persistency percentage of milk yield from the peak to 455 days of lactation were about 7.95 and 90%, respectively. These results were close to those recorded by Musaad et al (2013). On the other hand, Ishag et al (2017) obtained higher values of persistency than those reported in the present study. In Ethiopian camels, a little decline in milk yield was reported as the stage of lactation advanced (Zeleke 2007) due to the high persistency observed in camels. This discrepancy between the findings may be attributed to variation in camel types, husbandry practices, environmental factors, data set size and/or models used to estimate parameters of the lactation curve (Aziz et al 2016).

Growth of camels' calves

Birth weight

In the present study, the provisory results (Table 3) indicated that the overall mean birth weight of 20 calves was 41.0 ± 2.2 kg.

The results of the present study are in line with Khanna et al (2004). The high birth weight recorded in our study may be attributed to the feeding that the dams received during gestation (Bakheit et al 2012). However, the findings of our study are higher than the results of Azhar et al (2016). They mentioned that there is a strong link between the maternal body size, age, and the prenatal growth rate of the fetus. However, Harmas et al (1990) reported that the age of the dam has a significant effect on birth weights; on the other hand, it varies widely between regions, breeds and within the same breed (Kadim et al 2008).

The growth rate of camels' calves

After 304 days of trial period, the calves gained 124 ± 4 kg. The average growth rate of camel calves recorded at 2-month intervals varied from 22.3 ± 0.6 to 28.4 ± 1.3 kg, respectively. The most possible justification for a meaningful gain by calves might be the personal attention their owners give them, because on the farm, male calves are used for fattening and meat production while females are used for herd renewal.

For both groups, a progressive decline happened at six months (Figure 1). There are two possible reasons for this: firstly, this lower growth coincided with the summer temperature rise, which affected the milk production of dams and resulted in reduced feed consumption of calves (Iqbal et al 2000). The second reason that could explain this gradual decline was the change in milker. In their study, Jemmali et al (2016) reported that when the usual milker changed, significant milk retention was often observed. The results of the present study were in line with Bissa et al (1998), who stated that the shape of the curve estimated from birth to one year showed a decreasing rapid growth from birth to six months; while the growth rate remained slow from 6 to 9 months.

Figure 1. Evolution of the average daily gain (ADG) and body weight of camel’s calves

Average daily gain

The results showed that the difference of average daily gain between Targui and Sahraoui calves was non-significant (p> 0.05). The overall mean of the average daily gain was 408 ± 9g/d.

The findings of our study were lower than those of Bakheit et al (2012), who studied the effect of management system on camel calves’ growth rate and daily gain in Sudan. After an 18-month trial period, they reported a daily growth rate of 534g/d in a semi-intensive management system. Our results, on the other hand, outperform those of Bhakat et al (2008), who investigated the growth performance of Indian camel calves reared under intensive and semi-intensive feeding management systems. They used only 10 camel calves aged 7-10 months in their study and divided them equally into two comparable groups. The average initial body weight of the two groups was almost similar. The average growth rate was 319 g/d in semi-intensive system management. This difference in results may be due to the variation of camel breeds or/and to the management practices.

The growth in this study was very higher than the growth rate recorded by Chibsa et al (2014), who studied milk productivity of camels and growth of calves in eastern Ethiopia managed in traditional ways, and the overall average daily weight gain of calves recorded was 243 g/d.

Overall, the difference was not significant (p > 0.05) between the means of the birth weight, overall weight gain, and the average daily gain in the two studied camel calves’ types (Sahraoui and Targui). Babelhadj et al (2016b), who studied the barymetry performance of two Algerian camel populations in the region of Ouargla, support this finding. They used a sample of 60 Sahraoui and 60 Targui dromedaries and they mentioned that the differences observed between the mean values of the two types were not significant.

All the results of this study indicated that the lactation performance of Sahraoui and Targui she-camels as well as the growth rate of their camel calves were similar. Consequently, the null hypothesis of equality of means cannot be rejected. The most possible justification for these findings might be herd management, especially the random selection of breeding animals, which can increase the level of genetic mixing between different populations (Piro et al 2020). This result is consolidated by Kadri et al (2020), who studied the effects of genotype, on milk composition of dromedary camels in South-East Algeria. They revealed the difficulty of defining the standard of a given local population due to the large fusion of blood between individuals (Photo 1). Babelhadj et al (2016a) mentioned that the species Camelus dromedarius seems particularly homogeneous in terms of overall variability. Interracial variability remains low, evidence of a recent morphological divergence on the evolutionary scale and subject to genetic exchange.

Photo 1. Consequences of the large intermixing of blood between the two populations: on the right, a Targui she-camel in a white coat is accompanied by her offspring in brown coat color; on the left, a Sahraoui she-camel in a brown coat with her white camel calf

Conclusion

• The study concluded that the Sahraoui and Targui dromedary camel types have shown similar production performance. The findings obtained assume that this similarity is considered mainly due to the large fusion of blood between both camel types over the years and to a similar management.
  
  
• The results of the present study are indicative of the great production potential the she-camels and their calves represent, characterized by a daily milk yield, peak yield, persistence percent, and average daily gain relatively high. These production performances can be further increased under optimal feeding and management conditions.
  
  
• However, further studies on larger sample sizes are recommended. Also, to further consolidate the results of this study, it is necessary to conduct a study on the genetic variability of the two main populations of Algerian dromedary camels (Targui and Sahraoui), with the perspective of a better characterization of Algerian populations.

Acknowledgement

We acknowledge Dr Bernard Faye for the guidance he offered during the experiment.

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