Peri- and post-parturient consequences of maternal undernutrition of free ranging does: A review

E M Idamokoro, V Muchenje and P J Masika¹

Department of Livestock and Pasture Science, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa
patrick.masika@gmail.com
¹ Fort Cox College of Agriculture and Forestry, P O Bag X2187, King William’s Town 5600, South Africa

Abstract

Undernutrition in pregnant goats raised under extensive or intensive systems must be avoided for sustainable goat production. Poor nutrition of does during pregnancy can have both immediate and long-term implications for dams and their offspring. During the last trimester in goats, poor diet and negative energy balance may result into loss of body weight and death of pregnant dams. After parturition undernutrition of does can cause low milk production, poor mother to kid bonding and reduced numbers of kids reared. Furthermore, undernutrition during pregnancy can lead to delivery of weak offspring, kid mortality, slow growth of kids and adversely affect subsequent reproductive performance. The aim of the present review is to highlight the adverse effects of poor feeding of does during their pre-parturient periods and its potential repercussions on dams and their kids before and after gestation. Conversely, the review also suggests some promising browse plants and agro-industrial by-products reported to boost the performance of pregnant does during drought period.

Key words: goats, feed restriction, pregnancy, repercussions

Introduction

Small ruminants play significant roles in agricultural sectors all over the world (Escareno et al 2012) and specifically in developing countries (Webb and Mamabolo 2004). Goats and sheep are common small ruminants that are valuable sources of meat, hide and skin, organic manure and other by-products (Masika and Mafu, 2004). The impact of goat farming is crucial to the livelihoods of many people as it forms an essential economic and ecological vocation especially in developing countries (Devendra 2001). From the world statistics, the number of goats is currently estimated to be about 861.9 million; with Africa possessing the second highest proportion of about 291.1 million (FAOSTAT 2008). For instance, statistics in the National records of South Africa show that, the number of goats in South Africa is about 6.6 million from which 64% are found among rural dwellers (NAMC, 2005), but this figure may however not represent the current status because the numbers of goat fluctuates on a yearly basis. The population of goats in the Eastern Cape Province of South Africa is said to be 3.15 million out of which 59% are raised by small-scale farmers (Estimated Livestock Numbers in the RSA, 2007). Under subsistence agriculture, goats are known to be favourable ruminant animals when compared to other ruminant animals because of their unique ability to adapt and adjust to unfavourable environmental conditions (Lehloenya et al 2005). Most farmers in developing countries keep goats for the production of meat, milk, skins, organic manure and other by-products such as fibre for income generation (Masika and Mafu 2004; Casey and Webb 2010; Iniguez 2011). Goats are also used to control bush encroachment in areas threatened with bush over growth (Nyamukanza and Scogings 2008). However, the reproductive performance of goats is the most valuable trait that determines sustainability and continual use as a valuable resource to improve livelihoods (Devendra 2001).

Pregnancy in ruminant animals including goats and sheep is usually characterised by stress (Harmeyer and Schlumbohm, 2006) and several other metabolic processes such as high demand for glucose and the release of pregnancy-related hormones (Bell and Bauman, 1997). This is as a result of their physiological state (Harmeyer and Schlumbohm 2006; Ingvartsen and Andersen 2000). As a result of this physiological stress, pregnant animals are usually subjected to high biological challenges (Mahmoud and Azab 2014) and their natural mechanisms of coping with stress (Terrazas et al 2012). Ruminant animals may not be able to withstand the physiological stress during pregnancy unless their energy balance meets up with the body demands (Blache et al 2008). The energy balance of goats is usually stabilized from nutrients in animal feeds and which play an essential role in improving the metabolic processes of dams during the demanding period of pregnancy (Hefnawy et al 2010). As pregnancy advances to the third trimester, the daily requirements for pregnant goats increases to about 2.5 times more than that of the non-pregnant ones in order to cater for the energy requirements of both the dam and its foetus (Laporte-Broux et al 2011a).

Of great concern is the fact that most small stock animals raised under extensive system of farming do not perform to their optimum potential (Schlink et al 2010). Pregnant goats under perform in extensive system of farming because of the additional stress of free ranging that result in energy depletion in most instances (Masika and Mafu 2004). During drought periods, pastures on which animals graze may lack sufficient nutrients that can effectively meet the nutrient requirements for maintenance and foetal growth and development (Celi et al 2008). Insufficient nutrients in feed limit the productive potential of goats raised under an extensive system of farming (Escareno et al 2012; Maphosa et al 2009). However, the productive performance of pregnant goats raised under extensive systems of farming may improve when given cheap feed from other available natural resources to augment the unavailable nutrients lacking in natural pastures (Snyman 2010).

Poor feeding of pregnant goats has been reported to cause low productivity as reflected by incidences of high mortalities of offspring after birth (Mellor and Stafford 2004), compromised viability of kids and reduced fertility of offspring in their adult life (Rae et al 2002b). These occurrences in goat husbandry affect their productivity and cause financial losses (Rhind 2004). Thus, the welfare of pregnant ruminant animals (and their unborn offspring) is hampered as a result of undernutrition (Kenyon and Blair 2014). As reported by Wu et al (2006), lack of adequate nutrients in the feed of pregnant dams can also lead to poor foetal growth. Nonetheless, goat production can be improved when there is provision of quality and/or supplementary feeding of dams during pregnancy (Terrazas et al 2012).

During the early stage of pregnancy, undernutrition has been indicated to be one of the major causes of death of embryos among other factors such as body condition score and weight of the dam (Abecia et al 2006; Martin and Kadokawa 2006). In addition, maternal undernutrition during gestation affects kid birth weight, kid weaning weight, dam body condition score and poor production of colostrum milk after parturition (Mellor and Stafford 2004; Terrazas et al 2009). The rate of increase of post-natal death of kids is also a great challenge that has led to decreased productivity in goat husbandry. Several countries have reported cases of post-natal death of offspring. For example, estimated figures for neonatal death cases in some countries like India (15-51%), Mexico (7-25%) and South Africa (12-15%) have been reported (Lall and Singh 1949; Ramirez-Bribiesca et al 2001; Mellor and Stafford 2004). One of the reasons provided for the high neonatal mortality rate in the afore-mentioned countries was undernutrition of dams during pregnancy among other factors including starvation, accident, predation and disease infections.

Over the years, the subject of nutritional recommendations required to improve the productivity of livestock species at their various physiological stages has been addressed (NRC 2007). However, the cost of purchasing conventional feeds for goats by financially constrained farmers maybe practically difficult because most farmers in developing countries keep goats with little or no intention of investing much on them. The search for other cheaper feed resources may provide an alternative to the use of commercially formulated expensive feed to raise livestock in improving goat production. Some locally available feedstuffs could be a potential alternative that can boost the reproductive performance of goats during pregnancy (Blache et al 2008). The aim of the current review is to highlight some repercussions associated with maternal undernutrition during pregnancy in goats raised under free ranging farming systems and also provide information on some selected browse plants and agro-industrial by-products with promising potential to improve the peri-parturient and post-partum welfare of the species.

Energy and protein requirements for does during pregnancy

Quality nutrition for does during pregnancy has a great impact on their performance. Poor maternal feeding during pregnancy consequently leads to low productivity of both the dam and their offspring after birth (Terrazas et al 2012). Goats’ nutritional need largely depends on their physiological status and activities and should also contain allowances for production (e.g milk) and maintenance (Greyling et al 2004). Several other factors including age, breed, body size and the stage of pregnancy influence the nutrient requirements for goats. Ordinarily, the various nutrients that make up the feed of goats include carbohydrate and fat (energy), protein, minerals, vitamins and water (Kawas et al 2010). These nutrients are required in the diet of pregnant goats for optimum performance during gestation.

The nutrient requirement for maintenance of non-pregnant goats is slightly similar to that of the pregnant dam during early stage of pregnancy (NRC 2007). Pointedly, there is an obvious challenge to present data that is gathered from all over the world on the nutrient requirements for ruminant animals due to the various systems of production and breeds of goats. However, a uniform feeding standard has been proposed for goats at different physiological stages (NRC 2007). The nutrient requirement for maintenance for dry non-pregnant goats is 0.42 MJME/kg ^0.75 (NRC 2007). During the first three months of pregnancy the energy requirements of animal is proposed to supply 0.483 MJME/kg ^0.75 and at the last trimester it is given to be 0.756 MJME/ kg 0.75 (NRC 2007). The digestible crude protein requirement for goat ranges between 2.3 - 2.8g/kg ^0.75 for maintenance and it increases to 5.04g/kg 0.75 at the last trimester of pregnancy (NRC 2007). Reduction in the level of energy and protein required for the growing foetus at this stage may impede the health of the dam and the foetus. It was observed that a reduction in the energy level of animal feed during late pregnancy led to pregnancy toxaemia (FAO 2005). This finding further reiterates the importance of energy for goats during pregnancy. The information obtained from studies done with ewes is used to determine the nutrient requirements for pregnant goats (Sutton and Alderman 2000).

Fundamentally, there exist some variations in the different levels of energy and protein requirements in pregnant female ruminants, which may be due to the weight and breed of the dam and also the number of foetus in the dam (Sahlu et al 2004). The energy demand for goats for the early, mid and late stages of gestation are given as 1.38, 3.31 and 6.31 MJ ME/d while the protein requirements for these different stages were reported as 7, 17 and 32 g MP/d, respectively (AFRC 1998). However, in another recommendation the energy requirements for the mid and late pregnancy for goats was reported as 1.35 and 2.59 MJ ME/d for energy while the protein requirements was given to be 31 and 62 g MP/d for protein, respectively (Sahlu et al 2004). The variations that exist in the energy and protein levels recommended for goats from these two studies could be due to the difference in the goat breeds and the number of foetus that they carry (Sahlu et al 2004).

Repercussions of raising pregnant goats solely on rangelands

One of the major challenges to sustainable goat production in developing countries is the fact that most farmers practice extensive systems of farming. Free ranging animals mostly depend on the utilization of grasses and forages from the natural veld which are often subjected to seasonal variation in terms of quality and quantity (Haenlein and Abdellatif 2004; Mellado et al 2004). The variation in the nutritional quality of rangelands is influenced by climate change (Arzani et al 2008); intensity of grazing (Henkin et al 2011) and soil nutrient content (Tessema et al 2011). Pregnant goats grazing solely on poor quality rangelands may face the challenge of meeting the nutrient requirements needed to support their physiological status (Ramirez-Orduna et al 2008). Poor quality forage leads to poor growth of the foetus (Mellado et al 2005) and exposes the dam to possible abortion of its foetus (Mahanjana and Cronje 2000). The incidence of abortion in goats grazing on low quality forage in a study carried out in Mexico was reported to be as high as 70% (Mellado et al 2001). This reiterates the importance of feeding pregnant goats with available potentially nutritious feedstuffs to boost their welfare and performance under the extensive system of farming (Ramirez-Orduna et al 2008).

According to Cerrillo et al (2006), the dry matter intake (DMI) from a shrub-land used for browsing goats in Mexico falls between 40-90 g DM kg ^0.75 across four different seasons. The DMI during autumn (59.8 g DM kg ^0.75) and summer (58.6 g DM kg ^0.75 ) seasons were indicated to be low and cannot effectively support pregnant dams (Cerrillo et al 2006). In another study by Sharma et al (1998), the DMI value (62.8 g DM kg ^0.75) of diets from rangelands used for goats was below the 72 g DM kg ^0.75 that was recommended by the National research Council (NRC 2007) for pregnant dams. Furthermore, the digestibility of diets selected during winter (51.3%) and spring (57.3%) seasons were reported to be inadequate in nutrients to support goat feeding (Cerrillo et al 2006). Supplemental diets for range animals may come from other feed sources if they can effectively complement the digestive intake and also meet the nutrient needs of pregnant goats (Fthenakis et al 2012). Feeding ruminant animals with locally available feedstuffs during periods of drought could be used to improve livestock productivity (Abecia et al 2006; Haenlein and Abdellatif 2004). This is because pregnant goats need to be in good body condition and proper state of health throughout the gestation period, prior to kidding and soon after parturition (Mellado et al 2005).

Pregnancy phases in goats and maternal undernutrition

There are several biological changes that occur in the body of female animals after conception. Understanding these changes, mechanisms and hormonal interactions at the different stages of pregnancy in ruminant animals is essential in improving the welfare of both the dam and its growing foetus. After conception has been initiated in animals, the foetus begins to develop. The development of the foetus in ruminant animals can be divided into three main phases namely: (i) period of ovum fertilization (ii) period of embryonic development which is the early stage of gestation (iii) period of foetal growth and development which is the late stage of gestation (Fthenakis et al 2012). Several studies have indicated the importance of maternal feeding on the health, growth and development of the growing foetus in ruminant animals (Gardner et al 2005; Ford et al 2007; He et al 2013). Maternal mal-nutrition during pregnancy in animals reduces placental growth which has a negative effect on foetal development (Osgerby et al 2002).

The stages in pregnant ruminants can be divided into three, namely; early, mid and late trimesters. The last stage of pregnancy (late trimester) in ruminants is usually characterized by stress (Mahmoud and Azab 2014). Most pregnant ruminant animals especially those bearing more than one foetus are often faced with the challenge of negative energy balance at the last trimester which is an indication of poor feeding (Moallem et al 2012). The condition of negative energy balance in pregnant ruminants causes pregnancy toxaemia and can sometimes result in death of the dam (Laporte-Broux et al 2011a). Ruminant animals with pregnancy toxaemia often show signs of loss of appetite, depression, sluggishness and muscular imbalance. For does to manage the stressful stage of pregnancy, they require energy feed (glucose) which is obtained through the process of glucogenesis (Bell and Bauman 1997). This process is achieved by the mobilisation of nutrients including propionate and glycogen-stored energy in the liver recycled into glucose (Bell and Bauman 1997).

Studies that focused on the adverse effect of maternal feeding of female goats at their later stages of pregnancy are limited (Rhind 2004). Some studies done on ruminant livestock revealed the negative effect of maternal undernutrition on the growth of foetus at all the stages of development starting from the peri-conception period to actual parturition (Figure 1). This gives an indication that each stage of pregnancy in ruminant animals plays crucial roles. Nutrition has a significant impact on the health status and body weight of dam, foetal development and performance of offspring at adulthood (Robinson et al 2006). It is also essential that the nutritional requirements at various developmental stages of the foetus are met in order to avoid stillbirths during pregnancy (Terrazas et al 2012).

Figure 1. Schematic illustration of the effect of undernutrition on pregnant dams (Sources: Rhind et al 1998; Hyttel et al 2000; Rae et al 2001; Rae et al 2002b; Osgerby et al 2004; Rhind 2004; Laporte-Broux et al 2012; Terrazas et al 2012).

Of interest is the fact that there is a wide range of mechanisms involved in the growth of foetus at the different stages of foetal development in ruminant animals (Rhind 2004). Maternal feeding of ruminants during pregnancy plays essential roles at diverse stages of foetal development starting from the formation of the different organs that make up the growing foetus (Rahardja et al 2014). Hyttel et al (2000) reported that maternal nutrition is key to the on-set of cell division for several endocrine and reproductive organs including the pituitary and hypothalamus glands. In addition, nutrition of dams contributes a significant role during the actual differentiation and development process of these organs (Rae et al 2001; 2002a). Compromise due to poor maternal feeding during pregnancy may affect the proper formation of these organs (Rae et al 2002a). However, the mechanism through which the growing foetus detects and reacts to the effect of maternal nutrition for its growth and development is still poorly understood. Recently, some studies have however reported that, the reaction of foetus to the type of feed utilized by their dam may be expressed through changes in the gene expression in the fetal muscle and adipose tissues, with genes associated with tissue and organ development and other metabolic processes such as adipogenesis, lipogenesis etc being differentially expressed, thereby affecting growth and development (Penagaricano et al 2014; Hoffman et al., 2016).

Peri-parturient period of does and the effects of maternal undernutrition

Nutrition plays a significant role during the gestation period of ruminants. Poor feeding during pregnancy may lead to poor growth of foetus, loss of embryo, low body condition of the dam and low birth weight of the kid (Martin and Kadokawa 2006). Although the nutrient requirement for pregnant animals at their early stage of pregnancy is similar to the ones for maintenance animals, it increases as pregnancy advances to the last trimester when the foetus exerts more demand on the tissue of the dam (NRC 2007). There is more pressure for glucose demand on the pregnant dam if it is carrying more than one foetus (Moallem et al 2012). Therefore, it is important to provide adequate feed containing the necessary nutrients for pregnant dams in order to meet their physiological need during pregnancy.

The role of doe undernutrition in relation to pregnancy toxaemia

Nutrition during pregnancy determines the performance of both the dam and it foetus before and after parturition (Rae et al 2002b). Some pregnancy hormones of ruminants that are related to nutritional metabolism including insulin, growth hormone, thyroxin and steroidal hormones are negatively affected by maternal undernutrition (Ismail et al 2008; Hefnawy et al 2010). These hormones play a vital role in regulating the metabolic processes that carter for the welfare and health of the pregnant dam. Furthermore, pregnancy toxaemia can be triggered in goats bearing more than one foetus as a result of maternal undernutrition which may lead to the death of the animal in some cases (Laporte-Broux et al 2011a).

Pregnancy toxaemia is an indication of negative energy balance in goats during the last week of pregnancy. The negative effect of pregnancy toxaemia increases with does carrying more than one foetus (Brozos et al 2011; Moallem et al 2012). Lack of energy nutrients in animal feed is known to be a major reason of pregnancy toxaemia (Laporte-Broux et al 2011a). In addition, goats suffering from insufficient energy reserve normally display poor mothering ability towards their newly born offspring soon after parturition as a result of the physiological distress which they may have experienced during pregnancy (Ramirez-Vera et al 2012). The lack of motherly care received by these kids from their dam immediately after birth could lead to poor growth, starvation and even death.

How undernutrition can negatively affect cardiovascular function of does during pregnancy

The cardiovascular function of animals is very essential to the smooth running of the circulatory system. The nutrients that are derived from feed are transported to other parts of the body for use through the circulatory system. Poor maternal feeding during pregnancy has been indicated to have adverse effects on the cardiovascular system in goats (Abdelaal et al 2013). In a study by Chaiyabutr et al (1980), undernutrition of goats at mid pregnancy stage had a negative effect on the flow of blood from the heart to other parts of the body. The effect of feed restriction also caused a considerably decreased in blood volume and blood flow in the mammary gland (Chaiyabutr et al 1980).

Circulatory failure of blood to carry nutrients from one place to the other may lead to death as a result of insufficient supply of glucose to the body of pregnant goats that are exposed to poor feeding during the critical stage of pregnancy (Rook 2000; Van Saun 2000). Likewise, poor feeding of pregnant does during the last stage of pregnancy may lead to the collapse of body lipid reserves causing the release of ketones (Hefnawy et al 2010). This occurs when there is insufficient energy in the body system of an underfed pregnant animal causing the glucose concentration in the brain to decrease and thereby causing a nervous breakdown of the body system (Abdelaal et al 2013). However, more research needs to be carried out on the effect of poor feeding of goats during pregnancy in association with the actual mechanisms involved in inhibiting the normal functioning of the cardiac system.

Pregnancy related hormones and animal metabolism as affected by maternal undernutrition

The gestation period is often accompanied with stress leading to the release of several pregnancy related hormones and a high interaction of metabolic responses in the dams. The body of a pregnant dam attempts to reset its endocrine function and metabolic reactions which are usually controlled by hormones (thyroid hormones and insulin) to carter for the demand of the growing foetus (Mondal et al 2014). Hormones released during this period help to maintain pregnancy. Compromise in the level (too high or too low) of hormonal concentrations may lead to poor performance of pregnant animals (Devendra 1992). Ordinarily, the compromise in the concentrations of hormones in animal body is influenced by available nutrients in feed.

Consumption of high energy feed by ruminants has a positive correlation with the level of thyroid hormones in livestock (Hefnawy et al 2010). In a study by Hefnawy et al (2011), the deficiency in energy nutrients in the feed of pregnant goats led to decrease in the concentration of thyroid hormone which has a detrimental effect on the animal. A low level energy feed in the diet of pregnant dams was also reported to cause a decrease in the level of blood glucose in goats (Hefnawy et al 2010). Reduction in plasma glucose results in energy imbalance and may pose a risk that may cause abortion of the foetus or death of the pregnant dam (Hefnawy et al 2010). The influence of maternal nutrition as it affects the concentration levels of pregnancy related hormones is further high-lighted in Table 1.

According to Hall et al (1992) and Foisnet et al (2010), high level of progesterone concentration in animals during pregnancy negatively affects the yield of milk produced immediately after birth. Increase in the level of progesterone was also reported to trigger poor mothering behaviour of goats towards their offsprings after kidding (Mahboub et al 2013). This may affect the survival of offsprings after birth (Slayi et al 2014). The increase in cortisol and insulin level due to poor maternal feeding in goats bearing twins was reported to cause pregnancy toxaemia (Hefnawy et al 2010).

Reduction in the concentration of glucose and thyroid hormones in the body of goats also led to a low energy balance at the last stage of pregnancy (Hefnawy et al 2010). The low energy balance is as a result of high demand for glucose by pregnant dam and its growing foetus at this stage which, cause the uterus to utilize every available glucose in the body of the dam as its major source of energy (Bell and Bauman 1997). Conversely, maternal undernutrition during this period may cause hypoglycaemia; reduce uptake of glucose in the uterine wall and within the umbilical cords; lower placental glucose transfer capacity (Leury et al 1990). The ultimate consequence of this could result into the abortion of foetus, poor development of the foetus and compromised wellbeing of dam which may also lead to the death of the pregnant dam (Mellado et al 2005; Laporte-Broux et al 2011a). Abortion in goats could result from an in-built instinct in pregnant dam forcing it to expel its foetus when responding to negative hormonal pressure due to low energy body reserves (Mellado et al 2005). From all these earlier studies, there is an indication that maternal undernutrition negatively affects the endocrine system of pregnant goats which also affect the welfare of the dams and reduce their production efficiency.

Effect of maternal undernutrition during gestation on kids before and after birth

Restricted nutrition of dam during gestation does not only have negative impact on pregnant dams but also on their offsprings. There exist a link between the nutritional status of a pregnant animal and the survival of its embryo. Prior to conception, studies have reported the losses of embryos resulting from poor feeding of pregnant dams in ruminant animals (Abecia et al 2006). These embryos are lost as a result of alterations in the concentrations of hormones (including progesterone and steroid hormones) leading to the modulation of the uterine environment of under nourished dam thereby causing the endometrium to become insensitive to stimulations thus, negatively affecting the survival of embryos (Abecia et al 2006). Wastage of potential off-springs due to embryo losses at early stages of pregnancy may be a substantial threat to sustainable animal production in developing countries. Lozano et al (2003) reported that low energy diet in the feed of ewes during the early stages of embryo development may result in an increase in prostaglandin F2α which also causes alteration in the uterine environment of the dam thereby, inhibiting the survival of embryos. Furthermore, maternal under nutrition during prenatal period negatively inhibits the development of secondary follicles of the skin; hinders muscle formation and alters the reproductive axis of foetus (Martin et al 2004; Reed et al 2014).These organs play crucial roles in enhancing the reproduction efficiency in the adult life of the offsprings. According to Wu et al (2004) undernutrition affects the placenta size of pregnant dams which in turn hinders the growth of foetus.

Conversely, post-partum consequences in offspring resulting from poor maternal feeding have also been reported. In the case of sheep for example, poor nutrition during pregnancy led to the delivery of thin and weak lambs with an incidence of high post-natal mortality rate (Dwyer 2008). According to Terrazas et al (2009), it was observed that there was a poor mother to kid bond in under fed female goats when compared to those that were well fed during pregnancy. After parturition, goats that were not well fed at pregnancy spent lesser time grooming their kids as compared to well fed goats (Terrazas et al 2009). The tendency of newly kidded dams to display lack of motherly affection towards their kids is often exhibited in their unwillingness to breast feed them and this may affect the survival of the kids (Terrazas et al 2009). The need for a strong attachment of newly born offsprings with their dam is vital for it to initiate a cordial bond immediately after birth till the period of weaning; thus, improving it health and welfare.

Martin and Kadokawa (2006) stated that the consequences of poor feeding of dams during pregnancy on their offsprings may sometimes not be evident soon after birth but signs become prominent in the later life of the growing kid. Poor maternal feeding during pregnancy negatively affects digestive functions of offsprings when they are in their adulthood. A study carried out by Trahair et al (1997) reported a reduction in the weight of alimentary canal and alteration in the morphology of the gastro intestinal tracts of lambs from poorly fed pregnant ewes. Laporte-Broux et al (2012) in their study also reported that kids from under-fed mothers exhibited low body weight gain and poor body condition in their adulthood. Poor feeding of pregnant animals affects the reproductive performance of the offspring in their adult life (Todd et al 2009). Reports of the consequences of poor feeding of mother dam as it affects their offsprings in their later life are further highlighted (Figure 2). Maternal nutrition of animals prior to conception has also been reported to negatively affect conception rate and offsprings’ performance after parturition (Velazquez 2015). However, the specific nutrients present in the feed of pregnant goats that induced changes which are observed in the anatomy, physiology and metabolic alterations of off-springs (in their adult life) are sparely known (Caton et al 2007).

Figure 2. Hypotheses to explain the hormonal imbalance, metabolic disorders, abnormal development and organ dysfunction in offspring of under-nourished dams

(i) High plasma glucose in the blood of adult offspring from under nourished dam may result from their inability to maintain glucose homeostasis due to impaired release of insulin into the blood stream which is linked to maternal under-nutrition during pregnancy (Ford et al 2007; Todd et al 2009).

(ii) Restricted muscle growth, lipid accumulation and alteration of muscle fibre type in adult offspring may be due to impaired gene and protein expression of the foetus in dam as a result of under nutrition during gestation period (Reed et al 2014).

Some promising browse plants and agro-industrial by-products as a potential alternative feed resource to improve reproductive performance of ruminant animals

Production losses in livestock can be severe when animals cannot meet their nutritional requirements when they are pregnant. Adopting the use of other readily available feed stuffs different from commercial goat feed may help to improve the performance of pregnant goats. Alternative feed resources are feed materials different from the conventionally formulated feedstuffs and can be used by farmers to feed livestock during feed scarcity. Studies have reported some successes in the use of some browse plant species and agro-industrial by-products that possess the potentials to improve the reproductive performance of livestock animals (Table 2). However, caution should be taken when feeding leaves of some trees or shrubs to pregnant animals in case of the presence of tannins. High tannin content in some plants is detrimental to the reproductive performance of pregnant animals (Blache et al 2008). When tannins are consumed in high concentration they have the capability to bind to nutrients thereby reducing their availability in the digestive tract of animals. Conversely, when tannins are consumed in a moderate or low concentration they have beneficial effects on reproduction (Blache et al 2008). The positive effect of tannins to reproductive performance is attributed to its ability to reduce protein degradation in the rumen and increase the supply of amino acid to the small intestine (Min et al 2000). It is also worthy to mention that the activities of tannins and their toxicity level can be reduced in shrubs and tree fodder using simple feed processing techniques including soaking in aqueous solution of wood ash and sun-drying (Makkar 2003); thereby making them fit for ruminant consumption.

The use of shrubs and tree leaves as feed for ruminants is now gaining relevance especially in developing countries. This development seems to be a right step in the right direction when promoting sustainable animal husbandry in most developing countries because most farmers in these regions may not be able to afford commercial feedstuffs for their animals due to financial constraints. Apart from the several studies shown in Table 2 that have reported the utility potential of browse plants as feed for pregnant goats (as experimental model), a number of other studies have reported the use of browse plants such as Tephrosia candida (Babayemi et al 2006), Ficus religiosa (Bamikole et al 2003),Ficus polita (Abegunde and Akinsoyinu 2010),Artocarpus integrifolia, Leucaena leucocephala, Gliricidia sepium, Sesbania grandiflora (Morand-Ferh 2005) and Acacia karroo (Marume et al 2012; Idamokoro et al., 2016) as feedstuff to improve the performance of non-pregnant goats. It is noteworthy to state that these afore-mentioned browse plants have been used by researchers to investigate their influence in reducing worm infestation, improving growth rate and weight gain, meat quality and blood haematology in goats. A major breakthrough from some of these research findings is the helpful information of the amount of nutrient digestibility, feed intake and nutrition composition of these fodders. Browse plants that have been successfully utilized as feedstuff to improve the productivity of non-pregnant goats may also be used (but with caution, considering the toxicity potential of some browse plants) to investigate their effects on pregnant goat performance before and after parturition in order to increase the data base of non-conventional feedstuffs that can be utilized as feed for pregnant goats. However, it is imperative to know how these forages can best be incorporated into the feeding regime of pregnant goats and at what stage of pregnancy they can best be incorporated in the animal diet without causing any negative effect on dams considering their physiological status which is quite different from that of the non-pregnant goats.

Strategy for incorporating locally available feed resource into the feeding regime of pregnant does raised under extensive system of farming

In extensive system of goat production, seasonal variation in the nutrient composition of forages may limit the performance of animals during high nutrient-demanding phases (such as growth, pregnancy and lactation) in ruminant animals (Lu 2011). Due to these fluctuations in the quality and quantity of forage at different times of the year, farmers may need to adopt innovative strategies to effectively manage pregnant goats. A clear understanding of the nutritional need and the ability to improvise good feeding strategies during scarcity can help to improve goat production. Locally available feedstuffs may be utilized by resource poor farmers to feed pregnant goats. Some strategies that could be adopted by farmers to improve goat welfare may depend on the availability of locally available feed with a nutritional content that can support breeding, pregnancy and lactation periods of goats (Iniguez 2011) and knowledge of harvesting, processing and storing of these potential feed material at times of high availability (Mlambo and Mapiye 2015).

A feeding plan known as “focus feeding” has been postulated to improve pregnancy performance in small ruminants (Blache and Martin 2009). This type of feeding approach involves supplementing bucks and dams that are intended for breeding purposes with rich locally available feedstuff (about 5-8 days prior to mating) in order to boost sperm production in bucks and ovulation rate and litter size of dams. Limitations to this type of feeding strategy include; timing accuracy, quality of supplementary feed and metabolic responses of dams (Blache and Martin 2009). Browse plants can be offered to goats either as a protein source or as leaf meal or pellets to substitute other concentrate feedstuffs in goat diet (Patra et al 2002). They can also be harvested and offered as a sole diet to free ranging animals in the morning before allowing them to browse on poor quality pastures during seasons of food scarcity (Mapiye et al 2009).

Conversely, to improve the feeding welfare of pregnant goats in most developing countries, a more holistic approach which may involve the use of a practicable feeding scheme can be employed in tackling the challenges of feed faced by dams raised under extensive system of farming especially during seasons of poor quality pastures. This approach may involve the contributions of some key players including farmers, researchers and other support agencies (e.g government and non-governmental organisations). Research findings showing scientific evidences on the use of locally available browse plants, tree fodder and agro by-products to improve pregnancy performance of dams can be recommended to farmers as feedstuffs for livestock. Farmers can also be trained on the method of harvesting locally available feedstuffs, feed conservation and feeding techniques as a strategy to equip them with the knowledge of goat nutrition. On the other hand, farmers should be open and willing to adopt the use of these locally available feedstuffs and new techniques of feeding their animals (Mlambo and Mapiye 2015). Additionally, farmers can suggest any locally available browse plants/ feed materials that have not been earlier researched on but, are widely grazed by goats to researchers through agricultural extension officers for further investigation if perhaps they can be used as animal feedstuff. Government and other agencies can provide storage facilities to farmers for conserving validated feedstuffs (e.g hay, silage and legumes) during seasons of plenty in order to feed pregnant animals during the periods of feed shortage. As earlier mentioned, all the major role players can network together in ensuring that pregnant dams are fed with adequate food during seasons of feed shortage in order to ensure sustainable goat husbandry and to further promote food security in developing countries.

Conclusion

• In summary, the review highlighted some research findings resulting from the consequences of poor maternal feeding of free ranging goats during gestation.
  
  
• The repercussions of poor maternal nutrition during pregnancy is expressed on both the pregnant dam and on its offsprings before and after birth and can cause acute or chronic effects.
  
  
• With research findings showing some evidence of limitations in goat production emanating from nutritional constraints especially in developing countries, it is important to give more attention to the subject of adequate feeding of pregnant goats.
  
  
• The possibility of improving the productivity of pregnant does and goat production in general may lie in the use of available alternative natural feed resources including browse plants and agro-industrial by-products that may be readily available and cheaper for financially constrained farmers when compared to the use of conventional animal feed.

Acknowledgements

The authors wish to thank the DST/NRF collaborative postgraduate training programme (ID: 92544) and Govern Mbeki Research Development Centre, University of Fort Hare for financial support.

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Received 9 February 2017; Accepted 15 August 2017; Published 3 October 2017

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