|Livestock Research for Rural Development 27 (3) 2015||Guide for preparation of papers||LRRD Newsletter||
Citation of this paper
Milk production and body weight changes were studied in the Algerian Rembi sheep breed. Thirty two lactating ewes, 3 to 5 years old, were divided into two groups of heavier (HG) and lighter (LG) body weights. The average weights were 56.6±2.4 and 47.5±3.9 kg for HG and LG groups, respectively. Milk yield was measured using oxytocin plus hand milking method and ewes were weighed weekly.
Daily and total milk yield were 587±200g and 63.9 kg; 527±202g and 57.3 kg, for heavy and low ewes, respectively, with 10.3% difference (p>0.05), in spite of a highly significant difference in means of live weights between both groups (p<0.001). During the first 7 suckling weeks, mean weight loss for HG and LG groups was 6.3% (p<0.001) and 6.9% (p<0.05), respectively. Body weight variations during the whole suckling period were not important in both groups; hence, ewes recovered almost all the initial live weight in the late experiment period.
Keywords: compensatory growth, oxytocin, suckling
Les effets des écarts en poids vif (PV) sur la production laitière (PL) et les variations corporelles, au cours de la période d’allaitement, ont été étudiés chez deux lots de brebis algériennes de race locale Rembi. Un effectif de 32 brebis, âgées entre 3 et 5 ans, a été réparti en deux lots de 16 têtes chacun; la moyenne du PV des brebis du lot lourd (HG) était de 56,6± 2,4 kg et celle des brebis du lot léger (LG) était de 47,5 ± 3,9 kg. Pendant les 16 semaines de l’expérimentation les animaux, dans les deux lots, avaient reçu une ration alimentaire identique. Les niveaux de la production laitière ont été estimés par traite manuelle précédée d’une injection d’ocytocine, avec pesées hebdomadaires des brebis.
La moyenne de la production laitière journalière et de la production totale étaient de 587±200 g et 63,9 kg; 527±202g; et 57,3 kg, respectivement, pour HG et LG, avec une différence de 10,3% (p>0,05). Par ailleurs, la différence en PV entre les deux lots était hautement significative (p<0,000) et le maximum des pertes a été enregistré pendant les 7 premières semaines de l’allaitement avec 3,56 kg pour les brebis HG, soit 6,3% du PV (p <0,001), contre 3,29 kg (6,9%), chez les brebis LG (p<0,05). La présente étude révèle une PL supérieure associée à une mobilisation en réserves corporelles plus importantes en faveur des brebis lourdes (HG), suivie par une récupération plus précoce en PV; toutefois, la mobilisation des réserves corporelles, dans les deux lots, n’était pas très importante par rapport aux poids des animaux. En conséquence, ses résultats confirment l’existence de deux lignées de brebis Rembi selon le PV (lourd et léger). Par ailleurs, le rationnement suivi durant cette expérimentation (identique à celui adopté enconditions semi-intensives dans la région de Tiaret) aurait couvert l’essentiel des besoins en énergie (entretient et production) des brebis Rembi de différents poids.
Mots-clés: croissance compensatoire, l'ocytocine, l'allaitement
The Rembi sheep is an indigenous breed of Tiaret district; producing high-quality meat, desired in Center and West of Algeria. Wools and skins constitute the secondary productions of this breed. Tiaret region ranks third with more than 1 miLGion heads of sheep; furthermore, Sougueur's livestock market assigns them a national notoriety (Zoubeidi and Chehat 2011). In large geographic distribution, plane and steppe zones, Rembi sheep was produced mainly under extensive or semi-intensive systems. In those conditions, food resources in spring and summer are limited to sole availability (fallow and crop residues) while in winter, animals in sheep fold receive barley and straw.
Body weight is a very important characteristic in animal husbandry due to selection criteria and economical profit (Cam et al 2010). So, live weight might be affected by the different management, environment and feeding conditions; that, increases in body weight involve improvement reproduction efficiency and profitability in ewes (Aliyari et al 2012). However, in harsh nutritional conditions, it would be beneficial to select lambs according to dam reserve mobilizing ability (Atti et al 2004).
In Algeria the most commonly used method by the sheep breeder to increase prolificity in the sheep is recourse to the hormonal treatments (for estrus induction and superovulation) without preliminary knowledge of the milking capacity and body weight aptitude of ewe; that causes a high mortality in twin lamb and an early degradation of the general condition of mothers.
The wide inter individual variations revealed, in milk production and body live weight in studying Rembi ewes by Benchohra et al (2013), need more investigation to assess the impact of heavy and low body weight, of this sheep breed, on milk production levels and related corporal changes, throughout the suckling period.
The study was conducted on experimental farm, of the Rahouia area in Tiaret district (western Algeria), belonging to the Agriculture and Rural Development Ministry (MADR), located between 35° 31' N and 1° 1' E, with 620 m of altitude, in cereal plane.
32 multiparous ewes rearing single lambs, aged between 3 and 5 years, were divided into two groups, 16 each; according to their live weight (LW). The average LW of the heavy group (HG) was 56.6 ± 2.4 kg and that of the low group (LG) was 47.5 ± 3.9 kg. Body condition score ranged between 2.5 and 3 in each animal group, at the beginning of the experiment. Animals were clinically healthy at the onset and through all the 16 weeks of experimental period; groups were housed together, in a semi-covered pens. Each ewe received daily, on average, 900 g of a mixture of ground barley (55%) and wheat bran hay (45%), 500 g of wheat straw and 1% of minerals and vitamins supplement; fresh water was procured in the morning.
Milk production was estimated using a manual milking method after oxytocin injection (Ricordeau et al 1960). Milk controls started the second postpartum week (PP) and have continued every 14 days until the 16th week. Estimation of milk production during lactation was performed according to the Fleischman method (Ruiz et al 2000). The ewes were weighed at lambing and regularly every week until the end of the experiment, before feeding, using an electronic scale with 100 g of accuracy.
Collected data (absolute body live weights, absolute daily milk yields, relative evolution of body live weights, and relative evolution of milk production) for each LW group and trial day were analyzed by Student and correlation tests. Means were considered significantly different when p<0.05. Statistical analysis was performed using the Statistica 8.0 software (Tulsa, Ok., USA).
Estimated milk yield and average means of daily production, for both groups, are summarized in tables 1 and 2. Daily milk peak at the amount of 1010±382 g and 926±268 g, respectively, for HG and LG, in the 2nd week; then, it has markedly diminished to reach 325±169 g and 243±154 g at the last control (16th week). Average daily milk yield for the whole lactation period was 587±200 g and 527±202 g respectively for HG and LG.
Comparison of cumulative milk production at the end of each month in two groups (Table 1), have not shown any significant differences (p>0.05). At the end of lactation period total milk yield was 63.9 and 57.3 kg for HG and LG, with 10.3% of difference (p>0.05).
Lactation curves in both groups are shown in Figure 1. Peaks occurred during the second week; then both curves fall rapidly. However, the line of lactation curve for HG was above that of LG from the 1st control to the day 84. The curves intersect from 12 to 14 weeks and then dropped for the following stage; until the end of milking period the line of LG curve continues to fall, whilst HG makes a notable redress.
|Figure 1.Evolution of lactation curves in heavy and low lots.|
|Table 1. Milk production and body weight change during each month of lactation periods|
|Lactation period (days)||Live Weight changes (kg)||Milk Yield (kg)|
|HG: Heavy lot; LG: Low lot|
The values of body changes occurring during suckling months and days are shown in Tables 1 and 2. At lambing, the average live weight of ewes in HG was higher of 9.15 kg (16.2%) than those in LG; the difference is highly significant (p<0.000). The first week postpartum, ewes in LG have shown a corporal gain of 1.18 kg, while LW of HG ewes remained constant. The maximum of mobilization in corporal reserves, in both trial groups, occurred in the first 7 weeks of suckling period (Figure 2); the cumulative losses were -3.56 kg for HG (6.3% of LW; p<0.001), against -3.28 kg for LG (6.9% of LW; p <0.05). After a month of lambing, the loss recorded in the HG was -2.91 kg (p<0.01), whereas it was lower in the LG (-1.89 kg; p<0.01). Until the end of the second suckling month, continual, but slight, weight losses were observed (-0.338 kg; p>0.05), in LG ewes; however, in heavy ewes a gain of + 0.137 kg of BW (p>0.05) was seen. Thereafter, during the 3rd month, LW means have tracked the same evolution with the previous month, with an increase of 0.244 kg and a loss of -0.112 kg, respectively, for HG and LG. At the end of suckling period, heavy ewes continued their gradual weight increase (+0.419 kg), against a significant recovery of reserves for the LG (+1.368 kg); with no statistically significance. On the other hand, the observation of the traced shapes of body weight changes, in heavy and low weight lots, at different suckling phases had shown, in general, a same evolution (Figure 2). Finally, for HG or LG, the statistical analysis did not establish a relationship between the relative values of LW changes and daily milk yield, during the entire suckling period, the respective coefficients were r = 0.009 and r = -0.057.
|Figure 2. Evolution of body weight in heavy and low lots during whole suckling period.|
|Table 2. Evolution of mean (±SEM) daily milk yield, live weight and daily variations in body reserves during each lactation month|
|1st month||2nd month||3rd month||4th month|
|DMY in HG (g/d)||935 ± 317||644 ± 168||446 ± 157||324 ± 157|
|DMY in LG (g/d)||814 ± 235||596 ± 242||414 ± 166||285 ± 164|
|BW in HG (kg)||53.7 ± 3.11||53.8 ± 3.45||54.1 ± 3.16||54.5 ± 3.38|
|BW in LG (kg)||45.6 ± 5.31||45.2 ± 4.59||45.1 ± 5.27||46.5 ± 5.98|
|BW variation in HG (g/d)||-97.06||+4.56||+8.13||+13.96|
|BW variation in LG (g/d)||-63.10||-11.26||-3.73||+45.60|
|DMY: daily milk yield, BW: body weight, HG: heavy lot, LG: low lot|
Regarding milk yield, heavy ewes in this study have produced 10.26% more than low weight ewes, this result is in accordance with those reported by Robinson et al (1968) in Grey face breed; Ruleas and Zarazua (1982) in Pelibuey breed and Attiand Nefzaoui (1995) in Barbarine breed. Accordingly, Gonzalo et al (2002) consider that weight and genetic character of the ewe are among the factors that have an influence on milk production. However, Marie et al (1996) have observed, in the Lacaune dairy breed, a 22% difference in milk yield between two lines of ewes, identified as high and low, despite their similar body weights, implying the importance of the genetic factor. To date, no study has been conducted to demonstrate the relationship between the production potential and the genetic factor in Rembi sheep. In addition, several authors (Caballero et al 1992; Alexandre et al 2001; Bocquieret al 2002; Gaias 2012) have reported that a good level of food intake allows the ewes to express their dairy potential. In this study, Rembi ewes’ feeding was adjusted according to conditions of semi-intensive production system, adopted by a breeder in the study area.
The high significant difference (p< 0.000) in the averages live weights, for both groups, besides the comparable live weight changes curves (Figure 2) confirm the existence of two different lines of body weight, heavy and low, in the studied Rembi ewes.
About changes in live weight during suckling months, maximum of losses was recorded during the first four weeks (Table 1), which is in accordance with the results reported by several authors (Abu Ishmais et al 2004; Flores 2004; Lakhssassi and El Fadili 2011). This important reserve mobilization in the first month of lactation can be explained by an achievement of a maximal milk production in the second week (Degen and Benjamin 2005) (Figure 2); period during which milk is practically the only food for the lambs (Lakhssassi and El Fadili 2011). During this first phase of lactation period Lakhssassi and El Fadili (2011) have observed in Timahdite ewes, with BW and ML closes to those of Rembi sheep (Benchohra et al 2013), a daily weight decrease of -66 g, comparable in particular with the LG of this study (Table 2). Lakhssassi and EL Fadili (2011) add that D'man ewes have lost -3.96 kg (132g/d), these values are higher compared to those recorded in both groups of ewes in our study; it may be explained by the high production level reported in the D'man breed (81.2 kg in 10 weeks) (Boujenane and Lainiri 1992). The Queue Fine de l’Ouest and Noire de Thibar ewes, also dairy breeds, have mobilized, respectively, 5.0 and 4.2 kg of their body reserves during the first month (Sadraoui et al 2012). The same report was made by AbouIshmais et al (2004) who observed an average corporal loss higher than 5 kg in the suckling Awassi ewes; with a milk yield twice more important than that of the milked ewes, which presented, in contrast, a constant increase in LW. Therefore, losses accumulated in 42 first days of suckling period, in both groups of this trial, shall not exceed 1 point of body scoring (< 4 kg) is still within INRA (1988) recommendation.
In summary, according to results discussed above, the increased level of mobilization in body weight reserves is closely related to milk production rank; ewes with high milk production are those who lose most of LW. Thus, at the end of suckling phase, moment corresponding to the lowest milk production level, recovery in body reserves was evident, particularly, in LG ewes allied to its markedly milk production decrease (Table 2), as stated by Degen and Benjamin (2005).
In Ouled Djellal, the main Algerian sheep breed, which received a diet of 500g/head/d, weight loss cumulated during the first 27d post lambing was -8.2 kg (-273 g/d), these losses are significantly higher than those recorded in our study (Table 2). After 20 days of the end of feed supplementation, the losses have increased of -3.3 kg, and at weaning day (77d post lambing) Ouled Djelgal ewes had lost 21.7% of average LW (Chemmam et al 2009). Contrary to what was presented by Chemmam et al (2009), after the first 60 days of lactation, we observe in our study an insignificant decrease (p>0.05) of body weight in LG ewes, against a weight increase in HG ewes. It should be noted that the milking capacity of the Ouled Djellal breed remains unknown to date.
At the end of lactation period ewes, in both groups, have shown a marked corporal recovery as observed by Flores (2004); Rembi ewes have lost 3.7% and 2 % of mean body weight recorded at lambing, respectively, for HG and LG. This slight variability in LW whole suckling period, in both studied groups, seem resulted of the moderate milk production level; despite the fact that HG ewes have produce more than the LG ewes; and, in return, they mobilize more corporal reserves. As well, the comparable live weight evolution shapes (Figure 2) observed, on entire suckling phase, may be due to maternal behaviour of ewes in relationship to their genetic ability to use body reserve as supposed by Atti et al (2004).
On the other hand, this result suggests that animal feed rationing throughout the study period was correct, which is in agreement with the results reported by Genty (1979) in lactating Romney sheep, Dorset and their crossbreed; breed; Joseph and Foot (1990) in Corriedale and South Australian Merino sheep breeds; Caballero et al (1992) in Manchega lactating ewes; Alexandre et al (2001) in suckled Martinik ewes and Lakhssassi and El Fadili (2011) in D’man and Timahdite sheep breeds. Atti and Nefzaoui (2004), on their share, have suggested that fatty ewes of Barbarine breed, with a higher milk production level, have lost more weight than thin; because of stored reserves in late pregnancy. To sum up, all authors concluded that the limited body weight change, occurring during the lactation period, indicates that a favourable feeding program had applied.
This work is a part of the objectives set by the Laboratory of Agro-Biotechnology and Nutrition in Semi-arid Zones and the Laboratory of Hygiene and Animal Disease of Tiaret University, relating to conservation and enhancement of genetic patrimony of Rembi sheep and promotion of sheep farming in Tiaret district.
Thanks are due to staff at the Experimental Farm of Rahouia and, also, to Mr. Mhamed Redda for manuscript revision.
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Received 20 December 2014; Accepted 8 January 2015; Published 3 March 2015
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