Effects of Lablab purpurues and concentrate mixed supplements on reproductive performance and pre-weaning growth of Horro sheep grazing natural pasture in Ethiopia

Highlights

• •Supplementation enhanced lamb birth weight, ewe weight gain during pregnancy and reproductive features studied.
• •The pre-weaning growth patterns of lambs from different dietary groups were unaffected by any of the supplemented diets.
• •Utilizing either of the forage legumes is preferable to using conventional supplements for supporting the reproductive and productive performance of sheep due to its low cost and accessibility to small-scale farmers.

Abstract

The goal of this study was to compare the productivity and reproduction of Horro ewes treated with concentrate supplements (T1), and Gebis-17 (T2) and Beresa-55 (T3) Lablab purpurues varieties. Horro ewes (n = 21, 7 ewes per treatment) with a mean premating weight of 26.3 + 2.1 kg (Mean + SD) were employed in the study. Ewes with uniform parity were selected from the Bako Agricultural Research Center sheep breeding flock. They were then blocked based on the premating weight into seven groups of three ewes each, and within each group randomly allocated to one of the three dietary treatments assigning seven ewes per treatment. Over an 8-month period, the ewes were supplemented with respective feed regimens, which encompassed 5 months of gestation and 3 months of lamb growth up to weaning. The results showed that supplementation enhanced lamb birth weight (3.01 vs. 3.42 vs. 3.42 kg) and ewe weight gain during pregnancy (76.94 vs. 42.11 vs. 58.05 g/day) for T1, T2, and T3, respectively as well as all reproductive features studied, except for abortion instances that occurred in ewes fed a diet in T2 and T3. The causes of abortion in T2 and T3 cannot be ascertained because the experimental ewes were grazing during the day. Even though the T1 diet improved ewe performance in a similar way to T3 and T2, the use of such supplements is usually limited due to their high cost and inaccessibility to smallholder farmers. This emphasizes the importance of seizing the chance to replace conventional protein supplements with low-cost, on-farm cultivated forage legumes like the one studied in this study. As a result, enhancing Horro ewes' performance with either T2 (Gebisa-17) or T3 (Beresa-55) diets throughout their mating season is a promising strategy for maximizing their genetic potential. Future research should focus on the effect of supplements on lambs' post-weaning growth rate and survival.

1. Introduction

Ethiopia has a diversified indigenous sheep population, with meat production being one of the most important aspects of the country's economy (Abegaz et al., 2011). Their production is, however, characterized by low productivity in terms of growth rate, meat production, and reproductive performance (Abegaz et al., 2011). Sheep reproductive performance and productivity are significantly hampered as a result of their low nutrition. Thus, targeted feeding can be employed to manipulate reproduction and productivity. As reported by Dwyer et al. (2003), who looked at the cost of undernutrition at each stage of pregnancy, nutrition has a greater impact on intrauterine growth than inheritance. According to the author, poor nutrition causes fetal losses, low lamb birth weight, reduced milk supply, and ewe mortality, all of which reduce sheep productivity. Due to the effects on lamb birth weight, colostrums, and milk production, as well as the ability to suckle, Dwyer et al. (2003) observed that ewe nutrition was directly validated as a primary driver for boosting newborn survival.

Ewes require proper nutrition throughout the production cycle, beginning with weaning and continuing through gestation and lactation (Ptáček et al., 2017). The number of fetuses generated, as well as oocyte/follicular maturation, ovulation, embryo development, and implantation, are all affected by pre- and post-tupping nutrition. As the pregnancy advances, this includes fetal survival, birth weight, liveliness, and colostrum production (Ptáček et al., 2017). Nutrition has long-term implications for the next generation's reproductive potential, in addition to the short-term effects on the parents' reproductive activity (Fowden et al., 2012). As a result, any animal production system will only be successful if flock nutrition is adequate throughout the reproductive cycle and both male and female requirements are met.

Legume forages are one of the supplements that have been employed in ruminant nutrition (Bell et al., 2018). Because of their easy availability on the farm, high nutritional content, and low feeding cost, forage supplements have significant promise for ruminant production in the tropics (Kebede et al., 2016). According to Melaku et al. (2004) supplementing Menz ewes with Leucaena pallida 14203 has no adverse effects on the ewes` reproductive performance, so it will be a suitable supplement for pregnant ewes fed on a basal diet of Teff (Eragrostis tef) straw. This finding highlights the importance of seizing the chance to substitute conventional, high-cost protein supplements with low-cost, farm-grown forage legumes in smallholder farmers' situations.

Several studies have shown that forage legumes can help sheep gain weight and produce more carcass (Abebe & Tamir, 2016; Diba et al., 2015; Taddesse et al., 2014; Diribsa et al., 2016; Tulu et al., 2018; Gemechu et al., 2020). On the other hand, there is still a scarcity of information on the use of such feed resources as a supplement to improve reproduction success. The lack of such data is predicted to stymie the establishment of a more effective sheep breed improvement program, both in the current study area and across the country. As a result, the purpose of this study was to see how supplementing the two Lablab purpureus varieties named as, Beresa-55 and Gebis-17, with a concentrate mixture affected the reproductive and productive performance of Horro sheep under free-grazing settings.

2. Materials and methods

2.1. Study area

The study was conducted at the Bako Agricultural Research Center (BARC). The location symbolizes western Ethiopia's mid-altitude sub-humid maize-growing agroecology. The center is located at a height of 1650 meters above sea level, with a latitude and longitude of 9° 06′ N and 37° 09′ E, respectively. The area receives an average annual rainfall of about 1316.7 mm, with monthly minimum and maximum temperatures of 11.2°C and 31.7°C, respectively.

2.2. Ethical statement for the experimental animal care

The experiment protocol utilized in this study was based on the Ethiopian Animal Experiments Inspectorate's institutional guidelines for animal experiments, which are part of Ethiopia's ministry of livestock and fisheries. The experiment was carried out following the regulations for the management of experimental animal care.

2.3. Feed preparation

Two varieties of Lablab purpurues (Beresa-55 and Gebisa-17) were planted on about one hectare of land at the Bako Agricultural Research Centre. Seeds of both Lablab purpurues varieties were sown in rows with 50cm between rows and 40cm between plants, while all plots were fertilized with 100kg/ha di-ammonium phosphate at planting. Weeds were controlled by hand weeding and hoeing until the crops were ready to be harvested for fodder. It was harvested at 50% flowering, chopped to 3-5 cm in length with a Maskinfabriken-Taarup chopping machine to make it more consistent and accessible to the animal, field-cured for 2-3 days depending on the weather, then baled, and stored in a roofed hay barn. Wheat bran (WB) and Noug seed cake (NSC) thought to be sufficient for the full study period were acquired from nearby wheat and oil processing companies. A mixture of NSC 49.5% and WB 49.5% ratio with 1% salt was formulated and provided to one of the treatment groups considered as a positive control.

2.4. Experimental ewes feeding, design, and treatment

A total of 21 ewes of the same parity weighed a mean premating weight of 26.3 ± 2.1 kg (Mean ± SD) were employed in the study. The experiment was conducted using a randomized complete block design with three treatments, each with seven ewes. To limit variation among experimental ewes, ewes were grouped based on pre-mating weight, and just one ram was allowed to breed with all ewes to eliminate the ram effect. Ewes were flushed with quality hay for around 45 days during mating. After successful mating, ewes were then given supplemental feed for 8 months in succession, comprising 5 months for pregnancy, and 3 months for lamb growth up to their weaning periods, as per the treatment plan. Except for one hour every morning when each ewe was separated to receive their respective nutritional treatments, all ewes were kept in the same Cynodon dactylon (Couch grass) dominated pasture to graze for eight hours every day. The dietary treatments are, T1: grazing + concentrate mixture (positive control); T2: grazing + Gebisa-17; T3: grazing + Beresa-55.

The standards for Ethiopian indigenous sheep and goat breeds developed by Yami, (2016) were used to calculate the level of supplementation at each stage of pregnancy. The author recommends that native sheep/goat breeds receive a mixed concentrate at a rate of 200 g/head/day during the first stage of pregnancy, 300 g/head/day during the middle of pregnancy, and 450 g/head/day during the last stage of pregnancy. Based on this recommendation, one of the treatment groups (T1) received a mixed concentrate containing 49.5% wheat bran, 49.5% Noug seed cake, and 1% salt of 200 g/head/day (early stages of pregnancy), 300 g/head/day (mid-stage of pregnancy), and 450 g/head/day (late stages of pregnancy), in the hopes that such levels of concentrate supplements would meet the nutrient requirements of pregnant ewes. As a result, the diet in T2 and T3 that is being supplemented at each pregnancy stage was determined based on their crude protein content to make them iso-nitrogenous to the concentrate mixed supplements. Ewes were also given 200 g/head/day of mixed concentrate during lactation, which is a general rule of thumb that should be supplemented for each offspring being fed and adjusted accordingly (Yami, 2016).

2.5. Measurements of live weight and reproductive parameters

At parturition, the ewes' weight at lambing, litter size, lamb birth weight, and abortion rate are all recorded. The reproductive characteristics of each sheep were recorded, including pregnancy rate, prolificacy rate, fecundity rate, lambing rate, abortion rate, and gestation length. The pre-mating weight was taken to determine the ewe's initial body weight, and then a weight record was taken every fifteen days in the morning before releasing the animals for grazing. Similarly, newborns were weighed shortly after delivery to determine their initial birth weight, and then every ten days until weaning age (3 months). For each sheep and her lambs, the average daily BW gain was computed as follows (Ksal et al., 2000):

For ewes:

$$\text{Average}\text{daily}\text{BW}\text{gain}=\frac{\text{final}\text{weight}\text{-}\text{pre-mating}\text{weight}}{\text{Gestation}\text{length}\left(150\text{days}\right)}$$

For lambs:

$$\text{Average}\text{daily}\text{BW}\text{gain}=\frac{\text{weaning}\text{weight}\text{-}\text{birth}\text{weight}}{\text{Time}\text{to}\text{weaning}\left(90\text{days}\right)}$$

2.6. Chemical analysis

Dry matter (DM), crude protein (CP), and ash were analyzed according to the AOAC, (1990) procedure. Crude protein (CP) was estimated by multiplying the N value by a factor of 6.25. Neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) were analyzed using the procedures of Soest et al., (1991). In vitro, organic matter digestibility was determined using the Tilley & Terry, (1963) method.

2.7. Statistical analysis

The GLM procedure of SAS software (SAS, 2002) version 9.1.3 was used to analyze the data from this experiment and substantially different means were separated using the least significant difference test at a 5% level of significance.

3. Results and discussion

3.1. Feed chemical composition

Table 1 shows the results of the chemical analysis of the experimental feeds utilized in this investigation. The dry matter content of the experimental feeds was similar, but the fiber and non-fiber nutritional contents varied.

Table 1.

Chemical composition of experimental feeds.

Feed samples	DM%	Nutrient composition (%DM)
		Ash	CP	NDF	ADF	ADL	DOMD
Noug seed cake	92.33	7.02	29.43	34.56	19.2	5.17	71.04
Wheat bran	91.88	3.82	16.54	39.06	7.96	1.04	75.32
Gebis-17	91.85	10.08	22.92	48.34	32.8	5.57	62.28
Beresa-55	91.99	13.46	23.46	44.3	30.31	5.64	63.88

DM = dry matter; CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; ADL = acid detergent lignin; DOMD = digestible organic matter in dry matter

Gebis-17 and Beresa-55 had greater ash, neutral detergent fiber, acid detergent fiber, and acid detergent lignin fiber constituents than the concentrate mixes, but had lower digestible organic matter content than the concentrate mixes. The crude protein level of Noug seed cake was greater, wheat bran was lower, and the two leguminous forage components were intermediate in this parameter. The fiber and non-fiber contents found in this investigation were comparable to those found in prior studies (Wegi et al., 2018; Mediksa, 2016; Diribsa et al, 2016; Tulu et al., 2018; Tesfay et al., 2018).

3.2. Horro ewes' feed consumption during pregnancy

Table 2 shows the average daily dry matter and nutrient intakes of Horro ewes based on their supplemental feeding. Except for total crude protein intake (P > 0.05), the remaining parameters were substantially different (P 0.01) among the dietary regimens. Ewes fed a T3 diet consumed more total ash than ewes fed a T2 or T1 diet. The increased ash content of the T3 diet compared to the T2 and T1 diets could be the cause of this variation.

Table 2.

Daily feed and nutrient intake of pregnant Horro ewes supplemented with Beresa-55, Gebis-17, and concentrate mixture kept under the free-grazing conditions.

Treatments	DMI (g/day)	Nutrient intake (g/day)						ME (MJ/day)
	Supplements	Ash	CP	NDF	ADF	ADL	DOMD
T1	286.93	15.56c1	65.99	105.61c	38.99c	11.79c	209.97a	3.36a
T2	287.48	28.98b	65.89	138.97a	94.29a	16.01a	179.04b	2.86b
T3	280.45	37.75a	65.79	124.24b	85b	15.82b	179.15b	2.87b
SEM	-	0.08	0.16	0.29	0.2	0.04	0.42	0.01
P-level	-	***	ns	***	***	***	***	***

¹Means within columns followed by different letters differ significantly (P<0.05); ***=(P<0.001); SEM= standard error of means; DMI= dry matter intake; CP= crude protein; NDF= neutral detergent fiber; ADF=acid detergent fiber; ADL= acid detergent lignin; DOMD= digestible organic matter in dry matter; ME= metabolizable energy; T1-T3= treatments.

Ewes in T2 consumed more fiber components (NDF, ADF and ADL) than those in T1 and T3. This disparity is most likely due to differences in fiber content among the supplemental diets employed in the study, as the Gebis-17 had greater NDF, ADF, and ADL values than the Beresa-55 and concentrate mixture. T1 ewes had higher total digestible organic matter (DOMD) and metabolizable energy (ME) intake than T2 and T3, even though both were statistically equal. Because the current study lacks enough information to estimate intake from grazing, it is impossible to draw a precise conclusion on the daily total dry matter and nutrient intake parameters of the experimental ewes.

3.3. Live weight gain in pregnant ewes and lambs

3.3.1. Pregnant ewes

Except for premating weight (P > 0.05), all growth indicators showed significant differences, as shown in Table 3. Ewes fed a diet in T1 and T3 had the highest final body weights, followed by T2. T1 vs. T3 weight increase and T2 vs T3 weight gain are statistically equal. When compared to T1, ewes in T2 grew at a slower pace of 4.8 kg. This appears to be related to T2 ewes' increased total fiber intake (Table 2), which most likely limits feed intake and digestibility due to differences in the digestible elements available for absorption and metabolism (Edwards et al., 2010). The body weight change and daily weight increase characteristics found for ewes in the respective feeding treatments do not follow the same pattern as their final body weight gain. The ewes fed a diet in T1 gained more weight than those ewes fed a diet in T2 and T3, but T2 and T3 are statistically at par.

Table 3.

Live weight gain and feed conversion efficiency of pregnant Horro ewes supplemented with Beresa-55, Gebis-17, and concentrate mixture kept under the free-grazing conditions.

Parameters	Treatments			SEM	P-level
	T1	T2	T3
Ewes
Premating body weight (kg)	25.85	26.71	26.29	0.93	ns
Final body weight (kg)	37.1a1	32.34b	34.23ab	1.16	*
Body weight change (kg)	11.24a	5.63b	7.94b	0.83	**
daily weight gain (g/day)	76.94a	42.11c	58.05b	4.44	**
Lambs
Birth weight (kg)	3.01	3.42	3.42	0.21	ns
Weaning weight (kg)	10.89	9.87	11.57	0.9	ns
Weight change (kg)	7.89	6.45	8.15	0.98	ns
Daily weight gain (g/day)	87.63	71.67	90.55	10.89	ns

¹Means within columns followed by different letters differ significantly (P<0.05); *=(P<0.05); **=(P<0.01), SEM= standard error of means; ; ns= not significant; T1 to T3= treatments

Daily weight gain, on the other hand, was higher for ewes in T1, T3, and T2, in that order. This disparity could have resulted not only from the different weight changes seen among the dietary regimens but also from the different gestation lengths. The live weight increase during pregnancy, which is the result of intrauterine growth and maternal body weight change, is commonly used as a measure of nutritional sufficiency and to compare the impact of various dietary treatments (Amoah et al., 2018). As a result, the final body weight gain achieved by ewes fed diets in T1 and T3 demonstrated that the diets had a higher nutritional content than the diet in T2. The final weight gain obtained in this study is significantly higher than that reported by Melaku et al., (2004), who evaluated the productive and reproductive performance of Menz sheep and reported a result ranging from 20.3 to 25.2 kg. This difference is most likely due to the different types of sheep breeds and extra diets employed in the trials.

Fig. 1 depicts the trend in the ewes' body weight changes throughout their gestation period. Even though there was no statistical difference (P > 0.05) between ewes in T1 vs T3 and T2 vs T3, ewes in T1 and T3 had a faster growth rate than ewes in T2. Nonetheless, it can be concluded from the current study that all treatment diets increased the live body weight of the ewes during the gestation period. The nutritional value of the two Lablab purpureus varieties in general, and that of the Beresa-55 variety in particular, can be inferred to be comparable to the nutritional value of concentrate feed used to supplement Horro ewes during their gestation periods.

Fig. 1.

Bodyweight change trend of Horro ewes supplemented with Gebisa-17 and Beresa-55 varieties and concentrate mixture under free grazing conditions.

3.3.2. Lambs

Table 3 shows the mean birth weight (BW) of lambs produced from ewes fed their various supplemental diets, as well as their daily weight gain (DWG), weaning weight (WW), and body weight change (BWC). It was hypothesized that lambs born to ewes fed a concentrate mixture would grow faster than lambs born to Gebis-17 and Beresa-55 varieties. Although there was no significant data (P > 0.05) in this regard, it is interesting to note that the lambs from the various dietary groups performed similarly. According to Bell et al. (2018), the nitrogen in Lablab purpureus degrades quickly in the rumen, which is beneficial in meeting the requirements of rumen bacteria for efficient degradation of low-quality diets, resulting in improved animal performance.

The lack of statistical difference in WW, BWC, and ADG features among lambs borne under the various dietary regimens indicated that the supplements were equal in terms of their ability to give nutrients to lactating ewes throughout lactation. The weaning weight recorded in this study is greater than that reported by Silva et al., (2014) with values ranging from 9.03 to 9.15 kg but comparable to the value reported in a range from 9.8 to 10.1 kg (Amole et al., 2017), and the mean value of 11.81 kg (Solomon et al., 2000). The birth weight of lambs measured in this study is higher than that reported in the literature. For example, Solomon et al., (2000), for the same sheep breed, found that lambs' birth weights ranged from 2.63 to 2.77 kg. Mukasa-mugerwa et al., (2000) also recorded lambs' birth weights of 2.4 kg for Horro sheep and 2.1 kg for Menz sheep. Furthermore, birth weights ranging from 2.1 to 2.97 kg for Ethiopian indigenous sheep breeds were reported also in the literature (Awgichew, 2000; Mukasa-mugerwa et al., 2000; Melaku et al., 2012). The considerably higher lamb birth weight observed in the current study shows that supplementing ewes with high-quality feed sources throughout the gestation period benefits lamb birth weight, as lambs with higher birth weights have a better chance of survival and future growth.

Fig. 2 depicts the changes in lamb body weight (kg) over the weaning periods. The weights of lambs in T1, T2, and T3 grew positively, with similar growth rates. This shows that the supplements were comparable in their ability to provide nutrients to lactating ewes throughout lactation to alleviate nutritional stress.

Fig. 2.

Bodyweight change trend of lambs borne from the respective ewes supplemented with Gebisa-17 and Beresa-55 varieties and concentrate mixture under free grazing conditions.

3.4. Ewe reproductive performance

Horro ewes fed with the two Lablab pureurues (Beresa-55 and Gebis-17) varieties and concentrate mixed diets exhibited significant (P 0.01) variation only in the rate of pregnancy and abortion, but not (P > 0.05) in the other reproductive parameters studied (Table 4). Neither of the dietary interventions resulted in the birth of twins in any of the ewes. Ewes given T2 (150.5 days) diets had shorter gestation lengths than ewes fed T1 (151.8 days). However, T3 ewes had intermediate gestation lengths (151.2 days). This finding is consistent with reports in the literature (Solomon et al., 2000; Mukasa-mugerwa et al., 2000; Melaku et al., 2004; Idris et al., 2010).

Table 4.

Reproductive performance of Horro ewes supplemented with Beresa-55, Gebis-17, and concentrate mixture kept under the free-grazing conditions.

Parameters	Treatments			SEM	P-level
	T1	T2	T3
No. of ewes	7	7	7	-	-
No. of lambs lambed	6	6	6	-	-
Gestation length (day)	151.8	150.5	151.2	1.18	ns
Pregnancy rate (%)	90b	100a	100a	0	***
Prolificacy (%)	100	100	100	0	ns
Fecundity rate (%)	90	90	90	0	ns
Lambing rate (%)	90	90	90	0	ns
Abortion rate (%)	0b	10a	10a	0	***
Weight at lambing (kg)	33.42a	28.85b	30.89ab	1.14	*

¹Means within columns followed by different letters differ significantly (P<0.05); *=(P<0.05); ***=(P<0.001) SEM= standard error of means; ; ns= not significant; T1 to T3= treatments

Attributed to the presence of one non-pregnant ewe in T1, ewes fed a diet in T1 had a lower pregnancy rate than ewes fed a diet in T2 and T3. In this study, two abortion cases were observed, one from each of the T2 and T3 groups of ewes. To determine the cause of the abortions, more research is needed to look into the existence of potentially hazardous substances in Beresa-55 (T3) and Gebis-17 (T2) that could have hampered embryonic and fetal development in ewes fed those feeds. In addition to the potential existence of anti-nutritional factors contained in Beresa-55 and Gebis-17 that could be linked to the current abortion cases, mineral deficiencies, ingesting poisonous plants, hormonal and physical causes, and stress could all result in abortion in ewes.

Ewes in T1 and T3 gained more weight at lambing than ewes in T2, even though T1 vs T3 and T2 vs T3 are statistically equal in these parameters. The weight of ewes at lambing followed the same pattern as their final weight taken before lambing, though to a lesser extent. The reduced weight of the ewes at lambing is most likely due to parturition stress. Weight at lambing for Sudanese desert sheep ranged from 31.3 to 36.8 kg was reported by Fadlalla & Elmadih, (1998), which was greater than the values seen in this study. However, Melaku et al., (2004) who evaluated the productive and reproductive performance of the Menz sheep breed found lower values ranging from 17.1 to 23.1 kg. The differences between the current study and the previous studies may be attributed to variations in sheep breed, feed type and quality, and the composition of the grazed natural pasture.

4. Conclusion

The current study found that supplementing Horro ewes with high-quality feeds during their gestation phase helped them perform better in terms of productivity and reproduction. There were no significant differences among the dietary regimens studied for nearly all of the productive and reproductive variables evaluated. Even though the T1 (concentrate combo) diet improved the reproduction and production of sheep in a similar way to the Beresa-55 and Gebis-17 varieties, the use of concentrate supplements is usually limited due to their inaccessibility and high cost. As a result, it's critical to seize the chance to replace this conventional and expensive feed with low-cost, on-farm cultivated forage legumes like the ones used in this study. As a result, supplementing Horro ewes with either Beresa-55 or Gebis-17 varieties as an alternate protein source for ewes during their breeding season is a viable strategy for maintaining their genetic potential. Higher birth and pre-weaning live weight gain were the most important factors in determining post-weaning growth rate and survival thus, future studies should focus on demonstrating the effects of supplementation on post-weaning growth rate and survival if the apparently improved birth weight and pre-weaning weight gain were reflected on post-weaning growth rate and survival of lambs.

Author contribution

The following are the contributions of all authors to the preparation of this manuscript: Abuye Tulu; project planning, data analysis, and full paper writing; Tusa Gemechu was in charge of review writing, data collecting, and supervision; while Tesfaye Mediksa was in charge of manuscript editing.

Ethical statement

The experiment protocol utilized in this study was based on the Ethiopian Animal Experiments Inspectorate's institutional guidelines for animal experiments, which are part of Ethiopia's ministry of livestock and fisheries. The experiment was carried out in accordance with the regulations for the management of experimental animal care.

Declaration of Competing Interest

We, the authors of this paper, whose names are listed in the manuscript, have no financial interest to disclose or personal relations that could have influenced the research presented in this paper.