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Effect of age at first calving on lactation and reproduction of dairy cows reared in semi arid region of Algeria

T Madani, H Yakhlef* and M Marie*

Department of Agronomy, Faculty of Sciences, University of Ferhat Abbas, Sétif, 19000, Algeria
*Department of Animal Sciences, Institut National Agronomique El Harrach, 16200, Algeria
**Ecole Nationale Supérieure d’Agronomie et des Industries Alimentaires, 2 Avenue de la Forêt de Haye B. P. 172, 54505 Vandoeuvre lès Nancy, France


This study investigated effects of age at first calving on milk yield and reproductive performance among Montbéliarde heifers during six first lactations on 4 dairy farms in Algerian semi arid region. Data for reproduction of 492 cows and lactation of 352 cows were used. Heifers were classified according to age at first calving as early (24 to 30 months), medium (31 to 36 months), and late (37 to 42 months). Effects of herd, season of calving, parity and age at first calving were evaluated.


Average age at first parturition was 33.1 months. Average milk production during second and third lactations was 20 to 24% lower than in other parities and cows calving in summer produced 23 and 24% lower milk per lactation than did cows calving respectively in winter and spring. Milk yield was similar between all age groups at first and third lactations; however early calving group produced 20 and 24% less milk yield during second lactation compared respectively to medium and late calving groups, yielded 1162 and 1037 kg less cumulative milk yield for three first lactations, and 11 and 11.5% reduced cumulative 305-days milk yield for six first lactations. Early calving group recorded significantly delayed interval between calving and conception and calving interval (20 to 22 days) at first parity and had comparable performances to older calving classes during previous parities. Dissimilarity of body weight and energy balance across groups of age was probably the major factors that influenced reproductive and milk yield efficiency of cows. Optimum age at first calving for this study was 30 to 36 months.

Keywords: energy balance, lifetime production, milk yield, Montbéliarde, reproduction efficiency


Algerian development policy of dairy production is based on a massive introduction of exotic cattle breeds originate from temperate regions. Local production still however weak and cover less than 40% of market demand (Bedrani and Bouaita 1998). Lack of adaptation of exotic breeds to Mediterranean breeding conditions and management practices are generally advanced as main justifications of limited productivity of cows (Bourbouze et al 1989; Flamant 1991 ; Sraïri and Baqasse 2000; Srairi et al 2007).


Since last 30 years, Montbéliarde breed had been imported from France and mainly adopted by breeders of the region of Sétif, situated in semi arid highlands of North-eastern part of Algeria. Thus, Montbéliarde breed composed more than 80% of dairy cattle at the regional level (Madani 2000). However level of milk yield and reproductive performances still lesser than those performed in its native environment; the average of milk production per lactation fluctuated between 2200 and 3500kg, and variability between animals and herds still highly significant and had been associated to the effect of environmental factors and management practices (Madani 2000; Mouffok 2007).


Management of dairy replacement heifers is one of the most important factors affecting post-partum performances by determining body weight, and age at first calving (Pirlo et al 2000; Simerl et al 1992). Age at first calving (AFC) had also been identified as a significant factor affecting total cost of raising replacements in dairy cattle. Expenses related to rearing period of heifers in temperate climate constitute 15 to 20% of the total expenses related to milk production (Heinrichs 1993), and such costs can be reduced by accelerating growth and early breeding (Gardner et al 1988). Although first lactation production decreased, cows calving earlier produced more milk per day of herd life (Gardner et al 1977; Lin et al 1986; Nilforooshan and Edriss 2004). To maximize lactation performances and reduce rearing costs, Heinrichs (1993) recommended an average AFC in Holsteins to be ≤ 24 months. However, under South Mediterranean conditions understanding of age at first calving effects on reproductive and productive performances of foreign dairy breeds still lacking.    


The aim of this study was to investigate the effect of AFC on milk yield and reproductive efficiency of successive lactations and on total lifetime production of dairy cows reared in semi arid area of Algeria.


Materials and methods 

This study was achieved in the semi arid high plains of Sétif province, situated in North Eastern part of Algeria (36° 09’ North, 05° 26’ East). Precipitations occurred predominantly from November to May, were irregular in time and space and fluctuated from 300 to 500mm per year. Altitude ranges from 800 to 1300m above sea level. Temperatures fluctuated according to the season; summer is hot and dry and winter is cold and wet. Data collected during last 25 years showed that the average lowest minimum temperature was recorded in January (5.0° C), whereas the month of July recorded the highest average maximum temperature (26.1° C). Sétif is characterized by a large period of frost, till 45 days per year, which occur from November to April, and hot winds of Sirocco during summer.


Feeding management of herds was based on grazing of natural pastures in spring and autumn, cereals straws and corn or sorghum in summer and zero grazing during late autumn and winter, period during which animals received hay, and concentrate. Level of concentrate varied according to age of animals, pasture quality and level of milk yield.




Performances were recorded in four State farms. For this study only data from heifers born in Algeria were retained. Heifers selected for replacement were added to the herd at 15 months of age. Because of management errors several heifers were bred before 15 months of age. There was little use of artificial insemination. Thus, only records related to natural breeding were considered. Data were examined and records of lactations with more than 350 days in length, interval from parturition to conception < 20 days, records of cows with missing age at first calving or calving date were excluded. Remaining data concerned information about AFC of 557 females, reproduction of 492 heifers collected over 18 years (1984-2004), and a total of 1042 calving/lactation records of 352 cows collected from 1995 to 2004 inclusive. Monthly milk recording and daily reproduction parameters records constituted the data of the study. Records were collected by the technicians of the farms and than gathered and processed at the University of Sétif.


For analysing the effect of AFC on productive and reproductive traits 9 dependent variables had been retained: 305-days milk yield for the first, second, and third lactations considered individually, and for the three first lactations as a whole, cumulative milk yield for six lactations, cumulative 305-days milk yield for six lactations, interval between calving and first service (ICFS), interval between calving and conception (ICC) and calving interval (CI) for the first six parities. Independent parameters measured were herd, year of calving, season of calving, parity and AFC. Season of calving included winter (December, January and February), spring (March, April and May), summer (June, July and August) and autumn (September, October and November). Parity number included the first six parities. AFC was defined to be 24 to 42 months of age, and the proportion of the data on heifers that calved out of this interval was excluded. Freshening heifers were grouped according to the distribution of age at mating and divided into three classes: early AFC (24 to 30 months), medium AFC (31 to 36 months) and late AFC (37 to 42 months)


Data analysis


Data related to AFC was submitted to descriptive analysis (average, standard deviation and distribution). Data for reproductive traits were not normally distributed. Thus, data were transformed to a logarithmic scale. Then treatment was by least square factorial analyses using general linear model, SPSS procedure (SPSS 2001). The model included main effects of herd, year of calving, season of calving, AFC and interactions between main effects. Data were initially analyzed with all interactions in the model and then reanalyzed after removing no significant interactions. Year of calving was included in the model in initial analyses, levels of significance were similar whether year was included or not. As data size was small for five years, year variable was not integrated in the model.    



Age at first calving


Distribution of AFC for 557 heifers is presented in figure 1.

Figure 1.  Frequency of age at first calving

Average age at first calving was 33.1 ± 6.19 (S.D) months and coefficient of variation was 18%. Only 2% of heifers calved before 24 months of age, 25%, 43% and 21% calved respectively from 24 to 30, 31 to 36 and 37 to 42 months of age, while 9 % calved from 43 to 57 months of age.


Lactation performance


Data from analysis of variance showed effect of parity (P<0.004), season of calving (P<0.001), herd (0.04), AFC (0.01), interaction between AFC and season of calving, and interaction between AFC and number of lactation.


Average 305-days milk yield per lactation were lower in second and third lactations than in the other parities (table 1).

Table 1.  Least square means (LSM) and standard errors (SE) for 305-days milk yield according to parity, season of calving and herd



305 days milk yield

Parity number













3065a ± 125

2395b ± 131

2354b ± 137

2959a ± 156

2957a ± 146

3093a ± 110

Season of calving









3081a ± 175

3150a  ± 189

2380b ± 143

2664ab ± 131










2491a ± 46

2929b± 44

2882b ± 84

2790b ± 101




2776 ± 97

a, b Within each factor, means in the same column with different superscripts are significantly different (P<0.05)

Changes in milk production for second and third lactations represent a total lactation loss of 20 to 24% of milk when compared to the other parities. If level of milk production for lactations beginning in autumn was intermediate, cows calving in summer had lower values for average 305-days milk yield per lactation than cows starting lactation in winter and spring. This resulted in 23 and 24% lower 305-days lactation milk production in summer than respectively in winter and in spring. Mean milk production differed for cows of herd 1 when compared to the other herds and revealed variability of effect of heat stress and level of rainfall on feed resources quality.

Milk production was similar for all 3 groups for first and third lactations, and was comparable for medium and late calving for the three first lactations (table 2). But, during second lactation early AFC group produced significantly less milk than respectively medium (487 kg) and late (648 kg) calving groups, accounting for the significant AFC × number of lactation interaction (P<0.05). Although 305-days milk yields difference during first and third lactations between early calving group and other groups was not significant, the P-value (0.07) was near the critical P-value (0.05). This resulted in a loss of 11 to 13% milk production for early calving group. Cumulative 305-days milk yield for three first lactations was significantly lower (P<0.05) for early calving heifers; difference represented a total lactation loss of 1162 and 1037 kg of milk when compared respectively to heifers in the medium and late AFC groups. Similar cumulative milk yield and 305-days milk yield for first six lactations were observed for medium and late calving heifers. While, early calving group produced 11 to 11.5% reduced cumulative 305-days milk yield and 7 to 8% cumulative complete milk yield compared to the other groups.

Milk production was similar for heifers in medium and late groups for all seasons (table 3). Heifers in early calving class had the lowest performance when calving in autumn and lower average 305-days milk yield per lactation when calving in winter than did heifers in late calving class. The main difference of milk yield in 305 days for winter calving was 467 kg lesser for early AFC group compared to late calving group; in autumn, medium and late calving cows produced respectively 408 and 283 kg in 305 days more milk than did early AFC group.  

Table 3.  Least square means of 305-days milk yield per lactation (kg) by season of calving according to age at first calving

Age at first calving


= 24-30 months


= 31-36 months


= 37-42 months









2566a ± 161

2702 ± 131

2592 ± 164

2564a ± 136





2765ab ± 82

2885 ± 79

2690 ± 97

2972b ± 78





3033b ± 92

2904 ± 82

2670 ± 110

2849b ± 98

a, b Within each factor, means in the same column with different superscripts are significantly different (P<0.05)

Reproduction performance


Results from analysis of variance indicated that there were effect of parity and AFC and no interaction between AFC and all independent parameters (Table 4).     

Table 4.  Least square means (LSM) and standard errors (SE) of reproduction performances for the six first parities according to age at first calving 

Age at first calving

Early = 24-30 months

Medium= 31-36 months

Late= 37-42 months









Interval between calving and first service, days
















119 ± 7.2

99 ± 7.5

93 ± 8.4

108 ± 10.4

89 ± 10.9

97 ± 11.7

103 ± 5.2








128 ± 4.1

117 ± 4.6

109 ± 5.9

95 ± 6.4

104 ± 8.1

111 ± 8.7

113 ± 3.4








122 ± 6.3

103 ± 6.9

106 ± 6.5

90 ± 8.2

91± 8.9

94 ± 9.3

101 ± 4.4

Interval between calving and conception, days

















178a ± 8.2

156 ± 9.3

152 ± 9.9

160 ± 10.5

139 ± 11.2

 148 ± 13.4

129 ± 4.9








156b ± 8.0

150 ± 8.5

151 ± .9.6

155 ± 10.1

137 ± 10.5

161 ± 11.1

139 ± 3.5








158b ± 9.3

162 ± 9.8

153 ± 10.2

168 ± 10.5

137 ± 10.8

158 ± 11.3

127 ± 5.1

Calving Interval,



















456a ± 9.1

435 ± 9.4

431  ± 10.5

440 ± 12.7

419 ± 14.2

438 ± 15.7

434 ± 5.2








434b ± 6.6

429 ± 6.7

430 ± 8.1

434 ± 9.7

417 ± 10.8

441 ± 11.5

433 ± 3.4








435b ± 8.1

441 ± 9.1

433 ± 12.6

448 ± 13.5

418 ± 15.3

438 ± 17.7

436 ± 4.8

a, b Within each factor, means in the same column with different superscripts are significantly different (P<0.05)

Cows in lactation five had the best reproductive performance for the interval between calving and conception and calving interval.


For first lactation, heifers calving early had significant longer ICC than contemporaries calving respectively at medium (22 days) and late (20 days) AFC; as ICFS was similar, higher number of services per conception at first postpartum probably affected conception rate of early AFC group and delayed interval from calving to conception (table 4). As a consequence, calving interval were longer for early AFC group than respectively medium (22 days) and late (21 days) AFC groups.



Under semi arid conditions large variability of AFC between animals was probably caused by factors affecting growth rates and reproductive efficiency during breeding, and confirmed results observed by Van Amburgh et al (1998).  Differences between herds for mean milk yield per lactation reflected effect of heat stress on milk production and feed resources quality. Although all farms are subject to low level of rainfall and heat stress, farm 1 is situate more southerly, received less rainfall in general (300 to 400 mm/year) than the other farms (400 to 500 mm/year), and had probably shorter vegetation period duration and pastoral resources quality.


In summer, ambient temperatures prevalent in semi arid region are recurrently above 30°C. Cows calving in summer had lower values for 305-days milk production than did cows calving in winter and spring. These findings agree with results reported by Kaya et al (2003) for Holsteins in Turkey. Rodriguez at al (1985) reported that milk production in Florida were optimal when maximum temperatures were below 19.4°C. Decreases in level of milk production were significant from first to second lactation. But from second to third lactation, milk production trends accused non significant improve or a slight decrease. Main effects of lactation number in semi arid region were opposing to trends of milk yield observed in temperate regions. Bath et al (1978) and Ray et al (1992) showed that milk production increased significantly, but at a decreasing level, with lactation number till third or fourth parity. This suggested that under semi arid conditions, as dairy cows had higher level of competition between growths needs, reproduction, lactation and the obligatory bodily functions during second and third lactations, animals are facing more environmental constraints compared to more favourable breeding conditions.


Trends of milk yield during successive lactations showed decreasing tendency for all groups till second parity. During second lactation reduction was, however, more severe for early AFC group than in other groups. Energy balance was probably more negative because of growth needs were more required for early calving heifers during second lactation than in older calving heifers in order to reach physiological maturity. Effect of interaction between AFC and season of calving on 305 days milk yield showed that the greatest average seasonal range among AFC groups was in autumn and winter. The significant large variability in autumn and winter resulted from reduced performance for early calving group, indicating that cows had probably higher sensitivity to quality of forage. During stall feeding, in autumn and winter, animals received dry forages and concentrate; under semi arid climate high temperatures during growth and harvest of plants may greatly affect forage quality by increasing fiber and lignin content, reduces digestibility and intake potential (Van Soest et al 1978). As early AFC cows were probably smaller than older calving groups, their intake potential were highly influenced. Whereas, milk production was comparable between all groups in spring and summer; due to effect of high temperatures in summer, milk yield of all animals was probably affected and annulated effect of AFC between all groups.       


For Montbéliarde breed under Algerian semi arid conditions there was effect of parity on interval between calving and conception and calving interval; cows in lactation 5 had the highest reproductive performances suggesting that the competition between reproduction and lactation were less severe than in previous parities. This finding disagree with reports from temperate regions, where older cows are more susceptible to effects of higher milk production on involution of the cervix and uterus, which delayed first postpartum ovulation (Fonseca et al 1983), and concur with reports of Asimwe and Kifaro (2007) for dairy cows under tropical environment. Biological antagonism between energy balance and reproductive cycling during early lactations may be the most factor affecting resumption of ovulation (Lee et al 1997) and lead to a delayed physiological maturity.   


Cows calving between 24 and 30 months of age observed during first lactation lower reproductive efficiency, consequence of inferior fertilization and embryonic survival. Ettema and Santos (2004) observed an effect of AFC on days open at first lactation for Holsteins in USA, although feeding management and climatic conditions of heifers were better compared to cows reared in semi arid region. Differences of body weight and energy balance across groups of AFC were most likely the major factors that influenced reproductive efficiency of cows. Negative energy balance affects oocyte size and quality (Kendrick et al 1999), and resumption of reproductive activity (Veerkamp et al 2000)


As early calving heifers were probably smaller, they faced more competition for energy to support growth, lactation and reproduction at first parity than did older AFC groups. Even under temperate regions improved dairy cows usually are in negative energy balance in early lactation (Berglund and Danell 1987), return to positive energy balance at around 40 to 80 days post partum (Sutter and Beever 2000; Coffey et al 2001), where cumulative body energy loss in the first lactation is, on average, only fully recovered at 200 days post partum (Coffey et al 2001).


If during second lactation calving interval was similar between all groups, medium and late calving groups produced significant higher milk yield than did early calving group. Medium and late AFC groups calved probably with further body weight, while early calving heifers were probably under more negative energy balance, affected less energy to reproduction than did older cows at first parity and yielded less milk during second parity. According to Coffey et al (2002), cows may not regain all lost body energy in the first lactation leading to a greater deficit to be recovered in the second. This may result in carryover effects from one lactation to the next, and on both yield and non yield traits such as health and fertility.


Although AFC had an effect on calving interval during first calving, cows calving at younger ages had similar reproductive efficiency during subsequent parities compared with heifers calving at later ages, and no advantage in reproduction was observed among heifers calving at older ages. But during their life time cows performing first parturition before 30 months of age produced for both traits of cumulative milk yield significantly less milk compared to other groups. Heifers calving after 30 months of age calved probably with higher body weight and had more body condition that could less aggravate negative energy balance early post partum and thus produced more milk. Effect of AFC was probably amplified by the fact that Montbéliarde is a late maturing breed. Therefore, for Montbéliarde heifers reared as in the present study, reproductive programs should be managed such that animals become pregnant to calve at the optimal age of 30 to 36 months.





This study would not have been possible without the support of four state farms, namely Khababa, Logmara, Chakhchouk and Makhloufi. The authors acknowledge their cooperation in relation to access to their dairy herds and to their farm records. The authors wish to thank also C Mouffok, L Smara, and F Z Aoufi for assistance with data collection.



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Received 21 February 2008; Accepted 2 April 2008; Published 10 June 2008

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