Assessing dairy potential and lamb growth performance in Algerian Rembi sheep

Mokhtar Benchohra, Karim Amara*, Houari Hemida, Ahmed Yacine Kalbaza** and Hebib Aggad

Laboratoire d’Hygiène et de Pathologie Animale (LHPA),
PO Box 78, Tiaret University, Algeria
mok.benchohra@yahoo.fr
* Laboratoire d’Agro-Biotechnologie et de Nutrition en Zone Semi-aride (LABNZSA), Tiaret University, Algeria
** Institute of Veterinary Science, Tiaret University, Algeria

Abstract

The aim of this study was to estimate milk yield of Rembi ewe by weigh-suckle-weigh (WSW) and oxytocin plus hand milking (OHM) methods during the suckling period, to determine male and female lamb weight at given age and correlation between daily milk yield and body weight gain throughout lactation. Thirty-six ewes with single lambs were used. Mean±SD age and body weight (BW) were 40.6±7.1 months and 51.2±4.7 kg. Measurement of milk yield started on day 14 after lambing and continued each 14 days to weaning.

Lactation curve peaked at 2^nd week and estimated mean daily milk yield and total milk yield were 1000±323g day⁻¹; 1077±306g day⁻¹ and 62.7; 55.3 kg for OHM and WSW methods, respectively. Milk yield estimated by OHM method was 11.8% higher than WSW method during the entire lactation period. Mean weights at birth and weaning were 4.29±0.44; 4.11±0.53 and 18.8±3.05; 18.0±2.37 kg for male and female lambs, respectively. During whole lactation period (120 days) mean daily weight gain was 121±25.7 and 119±17.6 g day^-1 for male and female lambs, respectively. Daily milk yield estimated using double weighing-suckling method was strongly related to lamb growth throughout lactation period. The present study brings the first data on lamb growth and milk production potentials of Rembi sheep breed showing a low milk production with acceptable male and female lamb weights at weaning.

Keywords: milk yield, hand milking, oxytocin, weigh-suckle-weigh

Evaluation du potentiel laitier et des performances de croissance des agneaux chez le mouton algérien de race Rembi

Résumé

Le but de cette étude était d'estimer la production de lait chez la brebis allaitante de race Rembi par la méthode de pesée avant et après tétée ( PAAT ) et par la méthode hormonale (MH), et la détermination des poids vifs des agneaux durant la période de l’allaitement. Les résultats ont montré que la production de lait estimée par la méthode hormonale (62,74kg) était supérieure de 11,8 % (p < 0,01) à celle de la PAAT (55,3kg). Les poids moyens des agneaux, à la naissance et au sevrage, étaient de 4,29 ± 0,44 ; 4,11 ± 0,53 et 18,8 ± 3,05 ; 18,0 ± 2,37 kg, respectivement, pour les agneaux mâles et femelles. Par ailleurs, la production laitière journalière estimée par la méthode PAAT était fortement liée à la croissance des agneaux, tout au long de la période de lactation, avec 0,86 et 0,87, respectivement, pour les agneaux mâles et femelles. La présente étude rapporte les premières informations sur le potentiel laitier des brebis de race ovine algérienne Rembi et sur la croissance de leurs agneaux ; ainsi, cette race montre un faible potentiel laitier avec un poids vif acceptable des agneaux au sevrage.

Mots clés: croissance, méthode hormonale, méthode PAAT, production laitière

Introduction

Morocco and Algeria are the biggest producers of small ruminants with 22 million of head in each country. North African sheep breeds are of low milk productivity and the milk self-consumed by the pastoralist households. However, in Algeria 22% of milk production is provided by small ruminants (Dutilly-Diane 2006). Rembi sheep (Photo 1) is indigenous of Center-West of Algeria. Tiaret region is the cradle of this breed devoted to lamb production in extensive and semi-intensive conditions. Rembi is the largest thin-tailed sheep in Algeria, ram body weight 90 Kg and ewe 60 Kg. This breed has considerable adaptability to hard environment conditions. It is one of the main Algerian sheep breeds with a total number close to 2 million head (Commission Nationale AnGR 2003). In prospect to improve sheep milk production in Algeria it can be useful to compare indigenous sheep breeds, but mainly to put on an selection plan to exploit intra breed variability (Benyoucef and Ayachi 1991). In Morocco and Tunisia, many studies have been conducted to estimate the dairy aptitude of main local sheep breeds. However, in Algeria, the only sheep milk production study published by Benyoucef and Ayashi (1991) was carried out with Hamra local breed. In addition, there are no published data on Rembi ewe production.

Photo 1. Rembi ewe and lamb

Study of dairy potential of some breeds traditionally considered for meat purpose is of great importance to lamb production. Milking ability of an ewe is one of the principal factors influencing weights of lambs during pre-weaning period (Ünal et al 2007), furthermore, it provides information for realization of optimum management and feeding strategies for ewes and their lambs (Torres-Hernandez and Hohenboken 1980; Snowder and Glimp 1991). It is difficult to measure exactly milk yield by hand milking from ewes that were not accustomed to milking, especially ewes from local sheep breeds (Ünal et al 2007). Thus, it is better to measure milk yield by hand milking after oxytocin injection instead of only hand milking (Reynolds and Brown 1991; Morgan et al 2000). The weigh-suckle-weigh method is one of the most frequently cited methods for measuring milk production (Snowder and Glimp 1991; Benson et al 1999; Ünal et al 2007). However, this method has limitations for estimating milk production due to its inability to measure exactly small amounts of milk consumed by young lambs, changes in lamb appetite during measurement times and ignoring urine and fecal losses between weighing (Benson et al 1999). Many authors (Geenty 1983; Benson et al 1999; Ünal et al 2008) have compared the estimated milk yield using injection of oxytocin plus hand or machine milking with that obtained by weighing of lambs before and after suckling. The produced milk difference was higher in favor of the hormonal method during the entire lactation period.

The objective of this study was to estimate milk yield of Rembi sheep by the double weighing-suckling and the double oxytocin injection-milking methods and to ascertain milking traits of this breed. In addition, to determine male and female lamb weight at determined age and correlation between daily milk yield and lamb growth during whole lactation.

Material and methods

The study was carried out in a Pilot Farm belong to Société d’ Evaluation et de Valorisation des Fermes et Périmètres Agricoles (SEVFPA), located in Rahouia region, Tiaret district in Western Algeria, 35 °31' latitude North and 1 °1’ longitude East and elevation 620 meters.

Sheep farming and feeding

Thirty-six multiparous Rembi ewes weighting 51.2 ± 4.7 kg (mean± standard deviation) aged about 40.6 ± 7.1 months and rearing single lambs (18 males; 18 females) were used in this study. Lambing occurred between November and December 2012. Lambs were kept with their mothers during the entire experimental period, suckling and receiving forage mixture with their dams. Lamb weaning occurred late at 120 days. During the last month of gestation, ewes received barley grain (500 g/head) and wheat straw (500 g/head). After lambing, lactating ewes received a diet containing ground barley (500 g/head), wheat bran (400 g/head), wheat straw (500 g/head) and 1% of vitamins-mineral premix. Fresh water was provided once in the morning.

Data collection

Lambs were weighed within 6 hours after birth, using an analytical balance and repeated weekly until weaning; weighings were performed in early morning before feeding. Lambs were identified with earrings. Milk measurements started on the 14^th day after lambing and continued each 14 days until the 112^th day. Two methods were used to estimate milk production: weigh-suckle-weigh (WSW) and oxytocin injection plus hand milking (OHM).

In the first test day, estimation of milk yield was carried out by the WSW method, over 6 hours with two suckling periods: lambs were separated at 8:00h until 11:00h (morning separation) followed by a 20 minutes suckling period. The operation was repeated after a second period of separation (midday separation). Lambs have been weighed before and just after suckling using an electronic scale of 10g accuracy. Milk consumption was defined as the difference between pre - and post suckling weights and indirectly as 3 hours milk yield. The second test day, lambs were separated from their mothers at the same time, 2 minutes following an intravenous (IV) injection of 10 IU oxytocin, the udder was milked out rapidly by hand. After 6 hours of separation, milk yield obtained at the second udder emptying was multiplied by four to determine the production of 24 hours. Milk amounts estimated by 28-day intervals until weaning (d112) were calculated using data collected from control days according to Fleishman method (Boujenane et al 1996; Ünal et al 2008; Moujahed et al 2009). Daily milk yield recorded in the first control (d14) was extrapolated to the seventh day after birth.

Data were analyzed using Microsoft office software (Excel 2007) for mean and standard deviation and STATISTICA 8.0 software to compare milk yield estimate at different periods of lactation using both methods and lambs growth with Student’s test (t-test). Correlation between milk production and lamb growth rate was characterized by correlation test.

Results and discussion

Milk production, lactation curves and persistency

Total milk yield estimated every 28 days using two methods are presented in Table 1. To further evaluate variation in milk production, the lactation was divided into three different periods: early (d 6 to 21), middle (d 24 to 42), and late lactation (d 45 to 112) (Benson et al 1999). Daily milk yield (DMY) obtained by WSW and OHM methods peaked around the 2^nd week of lactation; mean levels were 1077 ± 306 and 1000 ± 323 g day^-1, respectively. However, values of daily milk yield estimated at last control (weaning) were 292 ± 162 and 129 ± 127 g day^-1, for OHM and WSW methods, respectively. Estimated total milk yield (ETMY) was 62.7 and 55.3 kg for OHM and WSW methods, respectively, with 11.8% difference (p <0.01). In Bafra sheep (Turkish breed), use of oxytocin and machine milking gave an amount 6.3% higher than obtained by WSW method (Ünal et al 2008). Milk yield obtained during early and mid lactation periods was slightly higher for the WSW method (Table1) which was in correlation with results obtained by Ünal et al (2008). Conversely, during late lactation milk production was higher with OHM method (p <0.001). This was explained by the decrease in the frequency and duration of suckling after consumption of significant amounts of concentrate feed by the lambs, plus the fact that mothers did not tolerate suckling (Ricordeau et al 1960). Compared to the morning separation period, amount of milk suckled after midday separation was higher (p<0.001) during the first month of lactation (Figure 1) that was in agreement with Ünal et al (2008). However, there was no difference between suckled milk in both separation periods during mid and late lactation. Total milk yield (TMY) of ewes suckled by female lambs (57.4 kg) was slightly higher (p>0.05) than that obtained from ewes suckled by male lambs (54.2 kg), despite the superiority of male weight at birth. This is in contrast with Kahtuei et al (2008) who found that milk yield for ewes nursing male was higher than for those nursing female.

Figure 1. Suckled milk according to lamb separation period

During whole lactation period, the shape of lactation curves in both methods was comparable (Figure 2). For the first 6 weeks the WSW curve was slightly higher than OHM; both peaked in the 2^nd week. The curves intersected at day 42 and then dropped for the following period; at this time the fall of the curve for the WSW method was severe compared to OHM curve. For the OHM method, daily milk yield decreased gradually and persistency coefficients were satisfactory in general (Table 1).

Figure 2. Evolution of daily milk yield for WSW and OHM methods in Rembi ewes

 In a study conducted in Algeria with Hamra sheep (42.3 kg BW), using OHM method to estimate milk yield, Benyoucef and Ayachi (1991) found an amount of 56 kg during 42 days. Results obtained in the present study using the same method were much lower (30.14 kg), suggesting that Hamra ewes have a good milking potential. Boujenane et al (1996) have studied milk production of three Moroccan local sheep breeds (Timahdite, Sardi and Beni Ghil) using WSW method, they observed that peaks have occurred at the 2^nd week in all breeds and TMY values were 38.4, 40.6 and 42.7 kg for Sardi, Beni Guil and Timahdite sheep breeds, respectively, at day 56 of lactation; peaks were alike to Rembi ewes in this study and TMY was similar to that obtained with Beni Ghil ewes for the same period. Milk production of D'man Moroccan sheep breed (45 kg BW) estimated by the WSW method (Boujenane and Kerfal 1992) displayed higher performances with peak lactation of 1.72 kg day^{-1 in the 2nd} week and a TMY of 113.9kg (day 84) compared to 50.51kg obtained in this study. Tunisian Sicilo-Sarde dairy breed tested by OHM method and weaned at 90 days display an average milk production of 109.2 kg in 180 days (Mohamed et al 2008). However, Moujahed et al (2009) report a TMY of 74.9 kg in 225 days of lactation for the same breed weaned at day 75 and authors concluded that late weaning causes a significant decrease (20%) in milk production. In this study lambs were kept with their dams all over experimentation in order to respect similar weaning mode adopted by Tiaret region breeders.

Ewes explored in this study ranged from 3 to 4 years old. In a review, Talafha and Mohammed (2011) reported that dam’s age was a factor that influence milk yield of unimproved Awassi ewes; effect of ewe age on milk yield was greatest for 5 than 3 years old ewes (Kahtuei et al 2008). Feeding is a determining factor in milking performance, then, low feed intake seems to be the major reason for low milk production. In Middle East, milk yield of lactating Awassi ewe, receiving about 950 g day^-1 of concentrate was lower than that receiving 1350 g day^-1; milk amount was 58.5 and 93.3 kg, respectively, during a 9 weeks lactation period (Al Jassim et al 1999). This suggests that improvement of nursing Rembi diet could increase milk production. Lastly, in a review of Talafha and Mohammed (2011), the unimproved Awassi sheep breed reared in similar conditions with Rembi breed in current study, displayed an amount of 40 to 60 kg of milk per 150 lactation days (suckling period not included), however, authors concluded that improved Awassi sheep under intensive feeding system was the second best milk-producing breed of the world.

Lamb growth

Progress of body weight means from birth until day 120 are shown in Table 2. At birth, mean male lambs BW was slightly higher than female BW with 4.29±0.44 and 4.11±0.53 kg, respectively. Live BW reached at weaning was 18.8±3.05 and 18.0±2.37 kg for male and female lambs, respectively. There was no difference between male and female BW at any weighing time point, but a high BW standard deviation value was observed in each sex group. The highest DWG was recorded during the first month and mean values were 145±39.4 and 126±32.6 g day^-1 for male and female, respectively. During whole lactation period (0-120 days), mean DWG was 121±25.7 and 119±17.6 g day^-1 for male and female lambs, respectively.

Growth rate of both sexes of lambs was similar over the lactation period (Tables 2 and 3), thus lamb sex has no effect on lamb growth, which is in agreement with results reported by Sadraoui et al (2012) in Queue Fine de l’ Ouest and Noire de Thibar Tunisian sheep breeds. Conversely, Chikhi (2006), Aksakal et al (2009) and Daskiran et al (2010) showed that male lambs have higher growth performance than females. In a recent study conducted with Ouled Djellal lambs, Boussena et al (2013) recorded higher DWG values compared to Rembi lambs in this study (Tables 2 and 3) in similar weaning period (120 days). Maximum growth rates of 207 and 251 g day^-1, occurred at 0-30 and 30-60 day periods, respectively and weaning weight was higher (25.8 kg). Rekik et al (2008) found that D’man lambs reared in Tunisian Oasis had 11.4±3.5 and 13.1±3.6 kg BW at days 70 and 90, respectively. Mean DWG values were 120 and 140 g during 30-70 and 30-90 day periods, respectively. This result was lower than that obtained in our study for BWs and DWG at 30-70 days period (Table 3). In contrast, DWG for 30-90 days period was higher in previous study. In data published by Chikhi and Boujenane (2003), mean BWs of Sardi lambs were 4.10, 10.9 and 22.5 kg, at birth, 30 and 90 days, respectively. Growth was faster in Sardi lambs with 224 and 194g day^-1 for 0-30 and 30-90 day periods than Rembi lambs (Table 3). Many studies revealed that weaning weight of lambs is affected by ewe age; with lambs suckling old ewes having higher body weight (Chikhi 2006; Kahtuei et al 2008; Annett et al 2011).

Correlation between DMY and DWG

Milk production of Rembi ewes estimated by WSW method was closely related to growth of suckling lambs. Correlation coefficients were 0.87 and 0.86 on 1^st month of lactation for male and female lambs, respectively; the high correlation coefficient is explained by suckled milk dependency of lambs during this period. Then it became equal ( r = 0.71) for both sexes in the 3^rd month. Lamb live weight and milk production are highly correlated during early and mid lactation, and correlation coefficients declined as lactation progressed according to Ünal et al (2007). At last month of lactation, the coefficient was 0.63 and 0.61 for females and males, respectively. While a significant decrease of milk consumed by lambs was observed in the late lactation period a continuous rise of the growth curve has been shown. Diminishing correlations over the lactation period indicate decreased lamb dependency to milk as a unique feeding source and increased dependence upon solid feed (Snowder and Glimp 1991; Benson et al 1999; Ünal et al 2007).

Conclusions

• Estimated daily milk yield was different between methods (WSW vs OHM) according to lactation period. Oxytocin injection before hand milking induced 11.8% over-estimation of milk yield during the entire lactation period.
  
  
• Rembi ewes do not have a high milk production potential.  Growth rates of male and female lambs were comparable and lamb growth was not affected by decrease in milk during late lactation, as a result Rembi lambs can be weaned early after the second suckling month.
  
  
• Daily milk yield estimated using double weighing-suckling method was strongly related to lamb growth throughout the lactation period.
  
  
• The present study brings the first data on milk production and lamb growth potential in Rembi sheep breed. It revealed that daily milk production and lamb weights showed a large inter-individual variations during all study periods. Thus, production potential of Rembi ewes could be improved by selection and enhancing of feeding system.

Acknowledgements

This research has been conducted in partnership between Laboratoire d’Hygiène et de Pathologie Animale (LHPA) of Tiaret University and Pilot Farm of Rahouia (Tiaret District) belonging to Société d’ Evaluation et de Valorisation des Fermes et des Périmètres Agricoles (SEVFPA), Agricultural and Rural Development Ministry (MADR), Algeria. Authors thank the farm manager and the technical staff for their assistance.

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Received 21 November 2013; Accepted 21 November 2013; Published 1 December 2013

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