Non-genetic factors affecting milk yield and milk composition of traditionally managed camels (Camelus dromedarius) in Eastern Ethiopia
Z M Zeleke
Alemaya University, P.O.Box 54, Dire Dawa, Ethiopia
Zeleke_Mekuriaw@yahoo.co.uk
Abstract
The study was conducted to asses the effects of non-genetic factors on milk yield and milk composition of camels kept under traditional management conditions in eastern arid and semi- arid areas of Ethiopia.
The overall mean daily yield and composition of fat, protein, lactose and dry matter of milk were 3.75 liters, 2.47%, 2.67%, 4.67% and 10.44%, respectively. Stage of lactation, parity and season of the year had significant (P<0.01) effects on daily milk yield, composition of fat, protein and dry matter. The percentage composition of lactose remained unaffected by all variables considered. The highest average daily milk yield was recorded during the first 3 months of lactation (4.04 ±0.10 liters), whereas the least was after 9 months of lactation. There was no significant difference in daily milk yield until 9 months postpartum. The percentage compositions of fat and protein were also the highest during the first 3 months of lactation period (3.24±0.11 and 2.98±0.06, respectively). Similarly, the highest average daily milk yield and percentage composition of protein, fat and dry matter were recorded from camels of 3rd parity (5.43±0.19 liters, 5.32±0.44, 3.16±0.26 and 13.33±0.63, respectively). The least milk yield was obtained from camels of parity six. The highest daily milk yield (4.21±0.11 liters) was recorded during wet season as compared to dry season (3.54±0.10 liters).
This study indicated that camels are reliable sources of milk in hostile regions of the country with persistent yield and composition throughout most periods of lactation. However, culling strategy of old dams (after parity five in this case) and provision of adequate feed and water during dry season would result in better productivity.
Key words: Camel, Ethiopia, milk composition, milk yield, non-genetic factors
Introduction
The Ethiopian pastoral areas are estimated to occupy about 61-65% of the total area of the country and, are homes to 12-13% of the total human population. Furthermore, out of the total estimated livestock population of the country, the pastoral areas constitute approximately 49% of the cattle, 47.5% of the sheep, 51.5% of the goats and 100% of the camels (Beruk 2003). The climatic condition in pastoral areas is arid and semi-arid which is characterized by shortage of feed and water and occurrence of recurrent drought. The shortage of feed and water resources accompanied by high ambient temperature limited the productivity of crops and livestock in these areas.
In these hostile environments, camels are the most preferred
livestock species as they can well adapt and withstand the
aforementioned limitations. By virtue of their adaptability in arid
and semi-arid areas, camels play a significant role as a source of
milk for the inhabitants who have little alternative source of
food. Their contribution as dairy animals is more substantial
especially during dry season of the year when milk from cattle and
small ruminants becomes scarce. Nevertheless, there is a paucity
of information regarding environmental factors limiting milk
production potential of camels and the composition of their milk
under Ethiopian pastoral management conditions. Identification of
environmental factors that affect milk production potential of
camels and the quality of their milk is crucial for designing
improvement measures and thereby improve the living standard of
pastoralists. This study was, therefore, initiated to assess the
effects of major environmental factors on milk yield and
composition of traditionally managed camels in Eastern
Ethiopia.
Materials and methods
Study site
The study was conducted at Errer valley, eastern Ethiopia. The valley is situated in a transitional zone between the intensively cropped areas of the north-western highlands and the Jigjig plains. The annual precipitation of the area ranges from 400 to 500mm with two peaks (March to April and July to September). There is one long dry season (October to February). Vegetation commonly consists of dwarf shrubs (Indigofera species) interspersed with numerous large shrubs and trees such as Acacia and Boscia species, and densely populated Cacti plants (Tamire 1986). Forage and water availability is highly seasonal. During wet season water and browse are plenty whereas availability of both of them severely declines during dry season of the year.
Management of camels
All of the camels used for this study were owned by pastoralists and kept under extensive management systems of their owners. They were entirely fed on range vegetations. No supplementary feed was provided except salt which was given two-to-three times a month. The animals were watered every five to seven days during dry seasons, whereas there was no intentional provision of water during wet season.
Sampling procedure
To estimate daily milk yield, camels were completely milked bimonthly by hand into a clean container following stimulation by the calf for one minute. A total of 517 milk samples were taken for estimating daily yield and analyzing chemical composition. The extracted milk volume was then measured using graduated cylinder. Hundred milliliter milk samples per milking were taken after thorough mixing for analyzing percentage composition of fat, protein, lactose and dry matter. The analysis of milk composition was done using Mid Infrared Transmission Spectroscopy (MIRIS), an automated Milk Analyzer system (FMA2001, var.2.23).
Data analysis
Data were analyzed using Statistical Analysis system (SAS) 1999.
Means were separated by Duncan's multiple range tests.
Results and discussion
The least square means and standard errors for daily milk yield and percentage composition of fat protein, lactose and dry matter are depicted in Table 1. The overall mean daily milk yield was 3.75 liters while the percentage composition of fat, protein, lactose and dry matter were 2.47, 2.67, 4.67 and 10.44, respectively.
|
Table 1. Factors affecting daily milk yield (l) and milk composition (%) of camels |
||||||
|
Factor |
|
Variables |
||||
|
Stage of lactation, months |
N |
Yield |
Fat |
Protein |
Lactose |
Dry matter |
|
1-3 |
238 |
4.04±0.10 a |
3.24±0.11a |
2.98±0.06a |
4.74±0.06a |
11.66±0.15 a |
|
4-6 |
157 |
4.01±0.12 a |
3.10±0.13 a |
2.70±0.08a |
4.47±0.07 a |
10.81±0.19 ab |
|
7-9 |
67 |
3.92±0.16 a |
2.10±0.17b |
2.39±0.10b |
4.45±0.09a |
9.45±0.24b |
|
³10 |
58 |
3.01±0.15 b |
2.60±0.16b |
2.59±0.10ab |
4.24±0.09 a |
10.04±0.23ab |
|
Parity |
|
|
|
|
|
|
|
1st |
97 |
3.23±0.10 c |
1.92±0.11c |
2.65±0.07 b |
4.76±0.06 a |
9.94±0.158 c |
|
2nd |
275 |
3.69±0.06bc |
2.19±0.07b |
2.50±0.04 b |
4.59±0.04 a |
9.86±0.100 c |
|
3rd |
88 |
5.43±0.19a |
5.32±0.44a |
3.16±0.26 a |
4.31±0.11 a |
13.33±0.63 a |
|
4th |
25 |
4.92±0.40ab |
2.73±0.21b |
2.48±0.12 b |
4.39±0.23 a |
10.07±0.30 b |
|
5th |
26 |
3.72±0.20bC |
2.79±0.21b |
2.55±0.13 b |
4.35±0.11 a |
10.30±0.31 b |
|
6th |
6 |
3.01±0.11c |
2.62±0.12b |
2.64±0.07 b |
4.59±0.06 a |
10.45±0.17 b |
|
Season |
|
|
|
|
|
|
|
Wet |
259 |
4.21±0.11 a |
2.27±0.12 b |
2.43±0.07 b |
4.59±0.07 a |
9.90±0.18 b |
|
Dry |
258 |
3.54±0.10 b |
3.25±0.11 a |
2.89±0.07 a |
4.31±0.06 a |
11.09±0.16 a |
|
Overall |
517 |
3.75 |
2.47 |
2.67 |
4.67 |
10.44 |
|
abc = Means with different superscript letters in a column under the same factor are significantly different (P£ 0.01) N = number of samples |
||||||
The mean daily milk yield recorded in this study is inline with the previous findings of Reta and Mekonnen (2002). Similarly, the overall percentage values for fat, protein, lactose and dry matter recorded in this study are in agreement with the findings of Elamin and Wilcox (1992) and Kappeler (1998) for Kazakhstan camels. The percentage of fat obtained in the present study was lower than the percentage values reported by Knoess (1979), Elamin (1980) and Mohammed et al (1989) from Ethiopian, Sudanese and Somali camels, respectively. In fact, lower fat and protein percentage values than the present results have also been reported by Sawaya et al (1984) and Raghvendar et al (2004) from Saudi Arabian and Indian camels, respectively. The discrepancy in the percentage values of fat and protein might have emanated from differences in genotype, feeding management and physiological status of camels.
Effect of stage of lactation on yield and composition of milk
The stage of lactation of camels significantly affected their daily milk yield, percentage composition of fat, protein and dry matter but had no significant effect on percentage composition of lactose. There was no significant reduction in milk yield until the 9th month of lactation. Thereafter, a significant (P<0.01) reduction in daily milk was observed. The ability of camels to maintain higher daily milk yield for a period of nine months is very advantageous to pastoralists who may not get milk from cows and goats during dry periods of the year due to shortage of feed. This witnesses the special merits of camel production in arid and semi-arid areas in providing food for pastoralist in the form of milk.
Similarly, the percentage of milk fat was significantly higher during the first six months of lactation as compared the later stages of lactation (Table 1) which is in agreement with the previous findings (Iqbal et al 2001; Raghvendar et al 2004; Riek and Gerken 2006). The higher milk fat percentages during the first six months of lactation noticed in the present study indicate unique properties of camel milk. Regarding the effects of stage of lactation on percentage composition of milk protein, there was no clear pattern of variability. However, significantly lower percentage of milk protein was observed in camels at 7-9 months of lactation compared to camels at 1-3, 4-6 and above 9 months of lactation. The percentage of dry matter was significantly higher (P<0.00) in milk extracted during the first 3 months of lactation as compared to 7-9 months of lactation. There was no significant difference in the percentage of dry matter in milk among the rest of lactation groups. The variability in dry matter content might have been contributed due to changes in mineral content of milk as there was no clear relationship with fat, protein and lactose in this study.
Effect of parity on yield and composition of milk
Likewise, parity of camels significantly (P<0.00) influenced daily milk yield, percentage of fat, protein and dry matter. An increasing trend in daily milk yield was observed as the parity of camels advanced from the first to the third (Figure 1), the third parity yielding the highest volume of milk per day whereas camels at the first and sixth parities producing significantly lower milk volumes compared to the rest of the parity groups.
|
|
Production of the least volume of milk during the first parity is logical in that camels in the first parity are still growing and nutrients are partitioned for body building purpose and milk production. Similarly, reduction in daily milk yields from older camels (parity six) as compared to intermediate age groups may be due to wear of teeth, reduction in the number and potency of milk secreting cells, and general weakness due to old age. The percentages of milk fat, milk protein and dry matter were significantly higher (P<0.00) in parity three camels as compared to other parity groups.
Effect of season on yield and composition of milk
Season of the year imparted significant effect on yield and composition of camel's milk in the present study. Daily milk yield was significantly higher during wet months as compared to dry months which is in conformity with the previous findings of Zeleke and Bekele (2001) and Bekele et al (2002). Significantly higher milk yields recorded during wet than dry months may be due to better availability of feed and water during wet months as compared to dry months. The lower milk yield obtained during the wet season implies the need for improved feed and water supply during dry season of the year. On the contrary, the compositions of milk fat, protein and dry matter were significantly higher during dry season than during wet season (Table 1 and Figure 2).
|
|
|
Figure 2. Relationship between monthly rainfall and daily yield and composition of camel milk |
The higher composition
of fat, protein and dry matter during dry months may be due to less
moisture content of feed during dry season than during wet moths.
In addition to that the percentage of milk fat has a negative
correlation with milk yield.
Conclusions
-
Camels are found to be the most persistent milk producers in
arid and semi-arid areas of eastern Ethiopia with little decline in
milk yield as stage of lactation advances.
-
Camels beyond fifth
parities have to be culled as they yield lower volume of milk and
still compete for scarce feed and water resources.
-
Seasonal effects
on milk production potential of camels need to be mitigated by
improving supply of feed and water during dry season of the
year.
Acknowledgement
The author is thankful to pastoralists in eastern Ethiopia who
allowed their animals for this study.
References
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Received 13 November 2006; Accepted 23 February 2007; Published 4 June 2007