Effect of dietary supplementation on reproductive performance of Sudanese Desert sheep

A O Idris*, C Kijora** , F M El-Hag*** and A M Salih****

* Faculty of Natural Resources and Environmental Studies, Peace University, P.O. Box 20, El Fulla, Sudan
abuelgoni2003@hotmail.com
** Department of Plant and Animal Sciences, Humboldt-University of Berlin, Philippstr.13, Building No. 9, 10115 Berlin, Germany
*** Agricultural Research Corporation, Elobied Research Station, Box 429, El Obeid, Sudan
**** Faculty of Animal Production, University of Khartoum, P.O. Box 32, Khartoum-North, Sudan

Abstract

This study evaluated the effect of diet supplementation on body condition score (BCS) and reproductive performance of Sudanese Desert ewes in comparison with farmer practice without any feed supplementation. A total of 341 ewes aged 1-6 years, were maintained in four groups of similar initial body weight and age. Group 1 (60 ewes) was the control (no feed supplementation). Groups 2 to 4 (92, 97 and 92 ewes, respectively) received feed supplementation containing local available feed resources in amounts of 0.45 kg every three days at watering time during two periods (45 days mating period and 45 days before lambing).

Results indicated supplementation improved (P>0.05) BCS, lambing rate, fertility rate, prolificacy, fecundity, pregnancy, weaning rate and decreased abortion rate. Ewes of first parity number had higher (P>0.05) BCS. There were no effects of birth type, sex of lamb and parity number on gestation days. The reproductive performance was improved (P>0.05) as ewe's age increased.
 

This study indicated that a moderate diet supplementation, every three days, is an efficient strategy to reduce nutritional stress in Sudanese desert ewes and increase their reproductive performance.

Keywords: body condition score, ewes, Kordofan, reproductive performance, supplementation, Sudan

Introduction

The Sudan national sheep flock is estimated to be 50.9 million head (FAO 2009). More than 65% of the sheep in Sudan are of the Sudan Desert type; they are kept mainly in the northern parts where they are maintained under rangeland conditions. Sheep herds, owned by various pastoral and agro-pastoral tribes, undergo extensive seasonal migratory movements in search of pasture and water, as well as to avoid the biting range flies and flood and muddy conditions in high rain fall areas. The pattern of these seasonal movements varies from region to region, according to the prevailing climatic conditions, namely the degree of rainfall. The movements are also governed by the availability of the surface water supply and the distribution of permanent watering points (Idris 2000).

Sheep herds, under this extensive system of animal husbandry, are subjected to a series of environmental stresses during the dry season, mainly inadequate nutrition and inadequate drinking water. Additional energy expenditure for movement to watering and range areas does exist.

The reproduction of the Desert Sheep is seasonal with mating period starting in January and lambing season in July and August, during the rainy season, when abundant feed is available. The reproductive performance is highly affected by feed availability in the dry season, when mating occurs. Armstrong and Evans (1983) and Gordon (1997) indicated that environmental conditions and feed availability influenced super-ovulation response of sheep under multiple ovulation. Literature considering the effect of feed intake on the ovulation rate in temperate sheep is confusing and contradictory. Rhind (1992) and Gunn (1983) suggested that ovulation rate was dependent on short term flushing only in ewes within the intermediate range of body condition. McEvoy et al (1995) showed that flushing ewes before mating did not increase ovulation rate, but improved the body condition of the ewes. El-Hag et al (2001) reported that the nutritional limitations under rangelands and harsh environment (high ambient temperature, scarcity of feed and water) conditions have a negative effect on the reproduction of the sheep in semi arid area of Kordofan State.

The objectives were to study the effects of a moderate dry season feed supplementation in two physiological stages (mating period and pre lambing period) on ewe productivity and reproductive performance. Different local feed resources were tested to evaluate the best supplementation

Materials and methods 

Study area

The study was conducted over a period of 18 months at El Obeid Agricultural Research Station, North Kordofan State, Sudan (Latitudes 11˚:15̀-16˚:30̀N, longitudes 27˚-32˚E). The average maximum temperature varies between 30 and 35ºC during most of the year with peaks above 40ºC during April, May and June. The rainy season extends from July to October, reaching its peak in August. Annual rainfall ranges from 75 mm in the extreme north to about 500 mm in the south (Technoserve 1987, El-Tahir et al 1999). The natural vegetation consisted mainly of the grass species Panicum tugidum, Arisdia spp, Cympopogons spp., Ctenium elegan, Dactylocteniun aegyptium and Eragrostis tremula (Harrison and Jackson 1958).

Traditional animal management

Management of experimental sheep was done according to farmer practice in the Kordofan region. Sheep raising in northern Kordofan State varies from sedentary systems around settlements (villages) to nomadic systems over considerable areas (Mufarrih 1991). The flock movement depends on the forage and water availability and two main grazing periods per day. The first started shortly after dawn and continued up to midday and the second was at the evenings extending up to midnight. During midday grazing, every three days animals were brought to watering points. There they were housed and rested under trees and shrub shade.

Experimental Animals and Treatments

A total of 341 mature Sudanese Desert ewes (1 to 6 years old) maintained on natural rangelands were selected during the normal breeding (mating) season in February and March. Experimental animals were vaccinated against diseases and injected with Ivomic for external and internal parasites. Ewes were then divided into four groups of similar initial body weight and age and randomly assigned to the treatment groups. One group (60 ewes) without any feed supplementation was used as a control (CTL) (emulating traditional farmer practice). The second group (92 ewes) was supplemented with ration A composed of 99% ground nut cake, 0.75% common salt, and 0.25% salt lick (GNC), the third group (97 ewes) was supplement with ration B composed of 89% groundnut seed cake, 10% molasses, 0.75% common salt and 0.25% salt lick (GNC-M) and the fourth group (92 ewes) was supplemented with ration C composed of 89% Roselle seeds (Hibiscus sabdariffa ), a species native to the Old World tropics, 10% molasses, 0.75% common salt, and 0.25% salt lick (RS-M). Each group was kept separately, animals were offered individually and were allowed an adaptation period of three weeks. The supplements were offered at the rate of 0.45 kg/head during the watering time every three days. The supplements were given during two periods of the experiment: flashing period (45 days at mating time) and steamed-up period (45 days pre-lambing time).

For mating, eighteen mature rams were introduced to the experimental ewes at the ratio of 1 ram:20 ewes. All rams were supplemented with same ration B (GNC-M) at the rate of 600 g/ram every three days. Rams were allowed to mix with the ewes twice daily: at 6:00 and 18:00 Hours.

Data collection

The BCS measurements were determined on a 1 to 5 scale (Khan et al 1992, Russel 1991), with the optimum value of 3, at breeding, mid pregnancy and lambing. Ewes that returned to oestrous were recorded; dates at first, second, third services were also recorded. Gestation period for each ewe was calculated as days elapsing from date of service to date of delivery. Number of ewes that were mated, pregnant, lambed, and aborted was noted. Characterization of lambs, number of live births, type of birth and sex of lamb, weaned lambs and lamb weight at birth were also recorded.

Reproductive and productivity parameters were calculated according to Landais and Cissoko (1986), as follows:

Lambing rate (%) = (number of ewes lambing /number of ewes mated) x 100.

Fertility rate (%) = (number of ewes pregnant / number of ewes mated) x 100.

Litter size (prolificacy) = (number of lambs / number of ewes lambing) x 100

Weaned rate a (%) = (number of lambs weaned /number of ewes mated) x 100.

Weaned rate b (%) = (number of lambs weaned /number of lambs born) x 100.

Fecundity rate (%) = (number of live births / number of ewes mated) x 100.

Abortion rate (%) = (number of ewes aborted / number of ewes mated) x 100.

Pregnancy rate a (%) = (number of ewes pregnant / ewes present to rams) x 100.

Analytical procedures and statistical analyses

The analysis performed to experimental diets were dry matter (DM) crude protein (CP) and ether extract (EE) according to A.O.A.C. (1995) and cell walls by the methods of Goering and Van Soest (1991) for neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL). The content of the metabolizable energy (ME, MJ/kg DM) was calculated from table values of energy content of the components.

The statistical analyses were conducted using GLM procedure of SAS (SAS 1994). The mathematical model for the analysis of reproductive parameters included fixed effect due to supplementation rations, ewe's age and residual error. Chi-square (χ2) analysis was then used to evaluate reproductive parameters differences. Significant differences (P ≤ 0.05) between means with respect to BCS, gestation days and services were tested using Duncan's multiple range test (Duncan 1955).

Results 

Composition of diets

The chemical composition of the supplements is documented in Table 1.

Diets A and B differed considerably from diet C. The CP concentration in the diets containing ground nut cake was greater while crude fibre and fat concentration were considerably lower than diet in C (89% Roselle seeds). The Ca:P ratio is not optimal in all diets, but the unbalanced ratio is much higher in diets A and B due to the very low Ca concentration in ground nut cake.

Body condition score

Body condition score increased during the mating season for all treatments (Table 2), with the greatest scores being (P<0.05) for ewes that were steamed-up with GNC-M and RS-M than those on GNC and control group.

However, the condition score decreased progressively with time with steamed-up ewes  maintaining higher scores (P<0.05) in comparison with those of the control group. Again, the condition score decreased sharply at lambing in July (the beginning of the rainy season) with steamed-up and flushed ewes having a better score than the controls. The ewe parity number had an (P<0.05) effect on the BCS, with primeparous ewes recording the highest BCS at mating and in mid-pregnancy.

Reproductive performance

Minor variations were found in gestation period as a result of flushing and steaming-up (Table 3); overall average gestation period was 150 days, ranging from a relatively shorter average of 149 days for ewes on CTL to a comparatively longer gestation period of 150 days for ewes on RS-M. Furthermore, ewe parity, sex of lamb and lamb type of birth exerted no main effects on gestation period.

Supplementation and ewe age had (P<0.05) main effects on the services to conception. Supplementation improved the percent of ewes that became pregnant in the first service. The conception from the first service was highest (P<0.05) on ewes fed with GNC-M and RS-M while the control group recorded highest non-pregnant ewes. Ewe age had an (P<0.05) effect on conception from the first service; adult ewes had the highest rates (P<0.05) followed by medium and , finally, the ngest ewes. But younger ewes had the lowest number of non-pregnant animals (Table 4).

Fertility, prolificacy, fecundity, pregnancy, weaning and abortion rates were shown in Table 5.

Supplementation improved (P<0.05) reproductive performance and ewes on GNC-M recording the best reproductive performance. Ewe age also had a (P<0.05) main effect on ewe reproductive performance.

Discussion 

The breeding season in north Kordofan State is usually planned for January-March so that lambing time is in the rainy season. This exposes breeding and pregnant stock to nutritional stress, as the breeding and gestation periods are thus in the dry season when the rangelands are at their lowest nutritional quality. The situation is critical during the dry season which extends from November to June. This is reflected in a seasonality of reproduction, high mortality rates in both young and adult animals and low reproductive performance (El-Hag et al 1998). The results of the control group in our experiment are comparable with the results of El-Hag et al (1998 and 2007).

The flushing and steaming up with feed supplement has proved to be advantageous in correcting the pasture deficit and improving the BCS and survival of sheep during this stressful period. Similar responses were obtained by Stephenson and Bird (1992). Poor nutrition leads to reduce conception, embryonic loss, and reducing lambing rates and high ewe mortality (Yoder et al 1990).

Due to the costs of concentrate feeding, El-Hag et al (1998) recommended a strategic feed supplementation during different physiological stages of ewes. They supplemented groundnut seed cake in amounts of 150g/day/head prior to the mating period and late pregnancy over 45 days each. The result was an increase in the reproductive performance and lower losses of animals (lambs and ewes). In spite of the higher feed costs they calculated a higher profit for the farmers who are practicing supplementation. Groundnut seed cake is a very good protein source, but rather expensive. In our experiment we used the alternative protein source Roselle seeds, which are widely available and cheaper. To guarantee a better rumen microbial activity, the supplementation of 10% molasses was done in GNC-M and RS-M diets. A comparison between the molasses-containing diets with only the supplementation of groundnut seed cake confirmed our hypothesis.

The differences in CP concentration of groundnut cake and Roselle seeds is considerable (56.3 and 33.0%, DM basis, respectively), resulting in differences in the reproductive performance between the two groups in some reproductive performance parameters indicated in Table 5. Group GNC-M had the greatest fertility rate, weaning rate and pregnancy and lowest abortion numbers.

In this study, a moderately high BCS was associated with supplementation (Table 2), the effect of supplementation being more pronounced at the mating period (breeding season) than at lambing (Montgomery et al 1988, Forcada et al 1992, Abecia et al 1993). An increase of ovulation rate in the breeding season has been associated with a high BCS (Rhind et al 1989 Xu et al 1989, Forcada et al 1992), with direct positive impacts on the reproductive parameters (Bukhari 2005 and El-Toum 2005).

Supplemented ewes were serviced and subsequently conceived within a shorter time than ewes in the farmer practice control group that had needed repeated services to conceive (Table 4). This agreed with the findings of El-Hag et al (2007), Holness et al (1978) and El-Hag et al (1998). Flushing and steaming-up had increased lambing, fertility, prolificacy, fecundity, pregnancy, weaning rate, and reduced abortion rate (Table 5), as observed for Sudanese desert sheep by Wilkins (1997), El-Hag et al (2006), El-Toum (2005) and Bukhari (2005).

Conclusion 

• Nutrition was a major limiting factor in the productivity of ewes in the region, and supplementation of ewes in breeding season had great advantages compared with farmer practice. Therefore, flushing and steaming-up should be demonstrated to more farmers and extension agents to improve Sudan Desert sheep in the semiarid zone of north Kordofan State, Sudan. The different supplementations in this experiment indicate that good protein sources together with molasses as an energy source are a promising strategy.

Acknowledgements

This study was funded in part by the German Academic Exchange Service (DAAD). We thank the technicians of the Department of Animal Breeding in the Tropics and Subtropics, Institute of Animal Sciences, Humboldt University of Berlin especially G. Sarsour and M. Heller for the chemical analysis, and we appreciate the facilities provided by the Department of Animal Breeding in the Tropics and Subtropics. We thank the technicians of the Elobied of Agricultural Research Station; B. Elffaki, H. Yassin and G. Khairi. Sincere thanks are to farmers at Fargalla village especially A. E. Amara for their cooperation.

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Received 24 March 2010; Accepted 3 June 2010; Published 1 August 2010

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