Non-genetic effects on reproductive and growth traits of Draa goats

M Ibnelbachyr, I Boujenane¹ and A Chikhi²

Institut National de la Recherche Agronomique, Center of Errachidia, PO Box 529, Boutalamine, Errachidia, Morocco
m_ibnelbachyr@yahoo.fr
¹ Institut Agronomique et Vétérinaire Hassan II, Department of Animal Production and Biotechnology, Rabat, Morocco
² Institut National de la Recherche Agronomique, Center of Kénitra, PO Box 1133, Kénitra, Morocco

Abstract

The objective of this study was to assess reproductive and growth performance of Draa goats and to estimate the non-genetic effects. Data were collected in the Experimental Station of Errachidia on a total of 148 does with repetitive performances and 667 kids. Reproductive data were analyzed using a mixed model and growth data were analyzed using a fixed model.

Length of pregnancy (LP), litter size at birth (LSB), litter size at 90 days (LS90) and litter weight at 90 days (LW90) averaged 147.5±2.60 days, 1.52±0.50 kids, 1.07±0.72 kids and 9.81±6.92 kg, respectively. Does with an age greater than 48 months had the highest LSB and LS90, whereas does kidding in spring had the highest LSB. Birth weight (BW), weight at 30 (W30), weight at 90 days (W90), average daily gain between birth and 30 days (ADG0-30), and between 30 and 90 days (ADG30-90) averaged 2.26±0.42 kg, 5.17±0.99 kg, 9.29±1.97 kg, 95.8±29.0 g/day, 69.5±24.0 g/day, respectively. Age of dam significantly affect all weights but not ADG. Males and single-born kids had the highest weights at all ages and the highest growth rates. Kids which were born in spring or autumn had the highest BW, whereas summer-born kids had the highest W90 and ADG30-90. It was concluded that these environmental factors should be taken into consideration in the selection program. 

Keywords: Draa breed, environment factors, litter size, body weight

Introduction

With a total of 5.5 million heads, the Moroccan goat herd ranked 13^th worldwide and is composed by several populations; with the most important are Black Mountain goats, goats of North and Draa goats of oases area. The Draa population is composed of about 10,000 heads. Animals have a medium-size with adult weight averaging 30 kg for females and 40 kg for males.

Draa goats are able to reproduce throughout the year (Ezzahiri and Ben Lakhal 1989), with a slight decline in sexual activity from February to April (Derquaoui and El Khaledi 1994). The absence of a marked seasonal anoestrus in Draa goats encourages a free continuous mating that results in kiddings distributed throughout of the year and in low fertility (69.4%) and prolificacy (1.26) (Ezzahiri and Ben Lakhal 1989). However, in a state farm, the same authors reported a fertility of 87% and a litter size at birth of 1.60, which indicate that there is a room for improvement of the Draa breed. Also, the interesting growth performance of kids during the suckling period (166 g/d) (Ezzahiri and Ben Lakhal 1989) led to the raising of Draa goats as a dual purpose breed.

In this context, an organized breeding system of three kiddings in two years will be advantageous for improving farmers’ profitability by increasing the number of kids weaned with a satisfactory growth rate. Such a breeding system was applied for Creole goats (Alexandre et al 1999), Brazilian goats (Nogueira et al 2012) and Omani goats (El Hag et al 2000), and also in D’man sheep (Boujenane et al 2013), but never used for Moroccan goats.

Moreover, besides of genetic effects, the goat performance is submitted to the non-genetic factors. In fact, Mellado et al (2006) reported that the reproductive process is regulated by genetic and non-genetic factors that determine the level and the efficiency of reproduction. In the selection process, non-genetic factors hinder the selection of superior animals to be parents of the next generations by masking the actual breeding values of these candidates to selection (Eltawil et al 1970). The objectives of this study were to assess the reproductive and growth performance of Draa indigenous goats and to determine effects of some non-genetic factors.

Materials and methods

 Site of the study

The study was carried out at the Experimental Station of Errachidia (31°92’01’3 N, 4°44’97’’5 W) located in the South-East of Morocco. The climate is arid, with an average maximum temperature of 38.7°C in July and an average minimum temperature of 0.8°C in January. The mean annual rainfall is 150 mm, with an irregular repartition from 3 mm in July to 27 mm in October.

Herd management

The experimental herd was composed by 80 does and 10 bucks of Draa breed (Figure 1). Animals were mated following a breeding system of 3 kiddings in 2 years. Three different mating periods were chosen: February 1^st - March 15^th, June 1^st - July 15^th and October 1^st - November 15^th, which correspond to births in summer, autumn and spring, respectively. During the mating period, a teaser buck was used twice a day to detect does in oestrus. These were immediately presented to their corresponding mating buck. Each buck was assigned 10 to 15 does, with whom he does not have any genetic relationship. Two groups of 30 to 50 does were mated alternatively. If a doe was not pregnant during a mating period, it was transferred to the group that was mated at the next mating period. The female kids were mated for the first time between 12 and 18 months of age, depending on their birth season.

Does were maintained under intensive feeding system based on straw and green or dried alfalfa, complemented with commercial concentrates (barley, corn grain, sunflower meal, faba bean and dried beet pulp). No grazing was allowed like as in the rearing system applied in the oases. Does received between 400 to 600 g/day of concentrate according to their physiological stage. During the suckling period, kids had free access (creep feeding) to a good alfalfa hay and a concentrate mixture with 18% protein (Figure 2). After weaning, they continued to receive the same diet until the age of 4 months. Then, males were placed on a fattening diet and females on a post-weaning growth regimen.

Animals were vaccinated against enterotoxaemia and treated against internal and external parasites. Additionally, a therapy against mastitis and diarrhoea was applied regularly at each kidding period. More details concerning herd management was presented in Ibnelbachyr et al. (2014).

Data recording and traits studied

Reproductive data were collected from 2006 to 2012 on 148 does with an average age of 38 months and weight at mating of 27 kg. Before mating, does were flushed and weighed. During the mating period, dates of mating were recorded daily. At birth, the kids were ear-tagged and weighted. Information concerning the date of birth, dam identification, sex, type of birth and birth weight was recorded.

Litter size at birth (LSB) is the number of kids born alive or dead per doe kidding. Litter size at 90 (LS90) is the number of kids present at 90 days per doe kidding, while their total weight represents the litter weight at 90 days (LW90) per doe kidding. The length of pregnancy (LP) is the interval between the date of mating and the date of kidding. Lengths of pregnancy lower than 137 days or greater than 156 days were discarded.

Growth data were collected on 667 kids between 2006 and 2012. At birth, the kids were weighed and the sex was identified. After birth, kids were weighted every 21 days until about 90 days old. Weights at 30 and 90 days were calculated by linear interpolation and the average daily gains from birth to 30 days (ADG0-30) and from 30 to 90 days (ADG30-90) were deducted.

Statistical analyzes

Depending on the trait studied, data analyzed varied from 264 to 461for reproductive traits and from 492 to 667 for growth traits. Reproductive traits were analyzed using a mixed model that included the random effect of doe and the fixed effects of age of doe (4 levels: age≤24, 24<age≤36, 36<age≤48, age>48 months), kidding season (3 levels: spring, summer and autumn) and year of kidding (7 levels: 2006, …, 2012), whereas growth traits were analyzed using a model that included the fixed effects of age of dam (4 levels: age≤24, 24<age≤36, 36<age≤48, age>48 months), type of birth (2 levels: single or multiple), sex of kid (2 levels: male, female), season of birth (3 levels: spring, summer and autumn) and the year of birth (7 levels: 2006 to 2012). The interactions between these factors were assumed to be negligible and hence were not tested. When an effect was significant (p<0.05), differences among least-squares means were examined using the pdiff option (SAS 2002).  

Results and discussion

Reproductive performance

The length of pregnancy of Draa does averaged 147.5 days, which is lower than the result reported for the same breed (153 days) by Boujenane et al (2010). For various breeds, such as Alpine, Boer, Jamunapari, Matou, Nubian, Sudano-Nubian, Pygmie andToggenburg, the values reported by Amoah et al (1996), Dickson-Urdaneta et al (2000), Greyling (2000), Moaeen-ud-Din et al (2002) and El-Abid and Abu Nikhaila (2009) varied from 148 and 152 days.

Litter size at birth, litter size at 90 days and litter weight at 90 days per doe kidding averaged 1.52 kids, 1.07 kids and 9.81 kg, respectively, indicating that Draa goats are moderately prolific. The result concerning the litter size at birth was similar to those obtained by Ezzahiri and Ben Lakhal (1989) on the same breed and by Güney et al (2006) on Damascus goats. However, they were lower than those found on the Creole goats, which gave birth to more than 2 kids per kidding (Alexandre et al 1999; Menéndez-Buxadera et al 2003). Litter size at 90 days was 0.45 kids lower than litter size at birth. This difference was due to the mortality of kids because of diarrhoea, hypothermia and enterotoxaemia. Moreover, the litter weight at 90 days was lower than that of the Iranian Cashmere goat (11-13 kg) (Maghsoudi et al 2009), but higher than those of Black Bengal goats (6.37 kg) (Mia et al 2013b) and Creole goats (7.75 kg at 82 days) (Alexandre et al 1999).

Least-squares means and standard errors for length of pregnancy, litter size at birth, litter size at 90 days and litter weight at 90 days are presented in Table 1. Age of does had significant effects on all studied traits. The highest length of pregnancy was recorded for does with an age between 36 and 48 months, whereas the highest litter size at birth and at 90 days were found for does of more than 48 months old. Does of more than 48 months old had a LSB 0.62, 0.36 and 0.25 greater than those of does having an age of 24 months or less, 24-36 months and 36-48 months. Likewise, does of the last two age classes had the highest litter size and litter weight at 90 days. The difference with the other age classes was at least 0.16 for litter size and 1.8 kg of litter weight. This finding was in agreement with that of Zhang et al (2009) who reported that reproductive performance increased as the age of doe increases, but was not consistent with that of Serin et al (2010) who did not observe any significant effect of age on reproductive performance.

Kidding season had significant effects on litter size at birth only. The highest value was recorded for does kidding in spring which corresponds to mating that occurred in October-November. The difference in litter size at birth was 0.07 and 0.15 compared to does kidding in autumn and summer, respectively. Our findings were in agreement with those of several authors (Güney et al 2006; Mellado et al 2006; Singh et al 2002) who found that kidding season had a significant effect on reproductive traits. According to some authors (Malpaux et al 1996; Delgadillo et al 1997; Mellado and Meza-Herrera 2002; Chemineau et al 2004 and 2007), reproductive traits in goats and sheep varied mainly with the photoperiod. In the present study, since the Draa is considered as a non seasonal animal, the seasonal variation in reproductive traits might be attributed to feeding conditions. In fact, Bushara et al (2013) reported that feeding can be a source of seasonal variations in some reproductive traits. The absence of kidding season effect on litter weight at 90 days in the present study was consistent with the result of Kebede et al (2012). This might be due to the high mortality of kids born in spring season compared to those born in other seasons even if the litter size varied significantly between seasons.

Year of kidding had significant effects on litter size and litter weight at 90 days (p<0.05), but not on pregnancy length and litter size at birth (p>0.05). In few studies where the year effect was analyzed (Dickson-Urdaneta et al 2000; Kebede et al 2012; Mia et al 2013a; Singh et al 2002), the reproductive performance varied generally among years according to the feeding and health conditions, which is also the case in the present study.

Growth performance

Birth weight of kids averaged 2.26 kg, which is similar to results reported at Skoura station on the same breed (Ezzahiri and Ben Lakhal 1989; Boujenane and El Hazzab 2008). Based on the weight at birth, it appears that Draa is a medium sized breed, like Serrana Transmontano (Jiménez-Badillo et al 2009) and Iranian Cashmere goats (Maghsoudi et al 2009). For other breeds, such as Jamunapari (Roy et al 2008) and Damascus breeds (Güney et al 2006), the weight at birth exceeded 3 kg. 

Weights at 30 and 90 days of Draa kids averaged 5.17 and 9.29 kg, respectively. This result was in the range of values found at Skoura station by Ezzahiri and Ben Lakhal (1989) (4.7 and 9.3 kg) and Boujenane and El Hazzab (2008) (5.8 and 10.4 kg). The average daily gains were 95.8 g/day from birth to 30 days and 69.5 g/day from 30 to 90 days. These findings were lower than results reported by Ezzahiri and Ben Lakhal (1989); 166 g/ day from birth to 30 days and 77 g/ day from birth to 3 months. Furthermore, Draa kids grew slower than those of  other goat populations, such as Tellicherry goats (Thiruvenkadan et al 2009), Serrana Transmontano goats (Jiménez-Badillo et al 2009and Damascus kids (Güney et al 2006) for which the average daily gain exceeded 100 g/d.

Least-squares means and standard errors for growth traits are presented in Table 2. Age of dam at kidding had significant effects on weights at birth, at 30 days and at 90 days. The highest weights were recorded by kids born from does of more than 36 months old. Weight superiority of kids from these dams was at least 0.31 kg at birth, 0.57 kg at 30 days and 0.72 kg at 90 days comparatively to the other age classes. This result was consistent to that of Boujenane and El Hazzab (2008) who found that the age of dam significantly affected weights at birth and at 30 days of Draa kids. In other studies (Mourad and Anous 1998; Al-Shorepy et al 2002), the effect of age of dam was found to be non significant on growth traits of Emirati goats. The last authors have attributed this to the size and late maturity of the studied breed. In our case, the kids seemed rather dependent to the care and milk production of their mothers during the suckling period, but this dependency decreased with the age. Mia et al (2013a) reported that the mothering ability and milk production increased with the reproductive career of dam.

Birth type had significant effects on all growth traits. The kids born as singles were heavier at all ages and grew faster than those born as multiples. The superiority of single-born kids was 0.34 kg at birth, 0.97 kg at 30 days and 1.67 kg at 90 days. This funding was in agreement with those of several authors (Thiruvenkadan et al 2009; Jiménez-Badillo et al 2009; Mia et al 2013b; Bushara et al 2013). The last authors attributed the difference in birth weight between single and multiple born kids to the uterine environment shared by kids. Thus, single kids do not compete for space and nutrients in their dam’s uterine (Jiménez-Badillo et al 2009), whereas the capacity of dams to provide prenatal nourishment for multiple fetuses is limited (Ebangi et al 1996).

The sex of kid had significant effects on all studied growth traits. At birth, male were heavier than female kids. Several authors (Zeleke 2007; Boujenane and El Hazzab 2008; Jiménez-Badillo et al 2009; Thiruvenkadan et al 2009; Bushara et al 2013; Harikrishna et al 2013) have reported a sex effect on birth weight. At 30 and 90 days old, males were always heavier than females, but the difference did not exceed 1.17 kg. This funding is in agreement with those of several authors (Boujenane and El Hazzab 2008; Jiménez-Badillo et al 2009; Thiruvenkadan et al 2009). The growth superiority of males has been attributed to the anabolic effect of male sexual hormones and their aggressive nature during suckling and feeding (Bushara et al 2013).

Season of birth had significant effects on weight at birth, weight at 90 days and ADG30-90, but not on weight at 30 days and ADG0-30. Kids born in spring and autumn had the highest weight at birth (p<0.05) (2.33 and 2.30 kg) comparatively to those born in summer (2.23 kg). In the same breed, Boujenane and El Hazzab (2008) reported a significant effect of birth season only on birth weight. In some other studies (Ebangi et al 1996; Harikrishna et al 2013), the effect of birth season was also found to be significant on birth weight. The authors had explained this effect by the herd management, some environmental factors (temperature and humidity) and the availability of feed. In the present study, the main reason of the seasonal effect in birth weight might be the climatic conditions; late gestation for does which kid in summer coincided with high temperatures, which could affect negatively the development fetuses. Mia et al (2013b) and Nogueira et al (2012) reported that does gestating during the favorable period give birth to kids with high body weights. However, the highest weight at 90 days and ADG30-90 were recorded by kids born in summer. This might be explained by the fact that the growth period for kids born in summer coincided with temperate conditions (September), whereas that of kids born in spring or autumn coincided with hot (May) or cold conditions (January), respectively.

Year of birth had significant effects on growth traits. Weights at birth, 30 days and 90 days had an improving trend, while growth rate varied randomly among years. The effect of birth year on growth traits was in agreement with the findings of several authors (Zeleke 2007; Boujenane and El Hazzab 2008) who attributed this annual variation to climatic conditions and feed management.

Conclusion

• Reproductive and growth performance of the Draa goats were in general satisfactory. Reproductive traits were influenced mainly by age of does, whereas growth traits were affected by age of dam, sex, birth type, season of birth and year of birth. These factors should be taken into account for the improvement of the herd management and selection programs.

Acknowledgements

The authors acknowledge the technical support of Mr. Chérif Er-rouidi, technician in the Experimental Station of Errachidia.

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Received 16 October 2014; Accepted 13 November 2014; Published 1 December 2014

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