Growth and reproductive characteristics of nigerian southern goats raised by varying management systems
P O Ogebe*, B K Ogunmodede* and L R McDowell**
*University of Ibadan, Ibadan, Nigeria
**University of Florida, Gainesville, FL, USA 32611
Senior author is P O Ogebe, Department of Animal Production, University of Agriculture, PMB 2373, Makurdi, Benue State
Thirty weaned West African Dwarf (WAD) goats were raised to twenty weeks of age under different modifications of the traditional system of management to evaluate growth pattern and reproductive characteristics of these animals. The same experiment was conducted twice in consecutive years. Goats were estimated at three months of age and weighed between 4.3 kg and 5.0 kg at initiation of the study. Animals were randomly divided into five groups, and in addition to natural grazing, were provided with the following modifying elements of the traditional system of management: Group A - provision of simple shelters only, Group B - simple shelters + mineral supplement, Group C - simple shelters + mineral supplement + supplement of crop residues + veterinary care, Group D - simple shelters + mineral supplement + supplement of crop residues, and Group E - completely extensive (free-ranging) (control). Results of both trials were an overall better daily body weight gain to 20 weeks of age when provided with a combination of shelter, supplementary minerals and supplements of crop residues (Group D). Animals which were traditionally raised (Group E), and those which received only shelter as a modifying element of the traditional system (Group A) were observed to perform poorly when compared to other groups. The growth pattern was affected by season, physiological stage, and type of modifying elements in the modification strategy. Increasing management components improved reproductive characteristics to the level of a combination of shelters, feed and mineral supplementation only (Group D), and not in addition to control of occasional health problems such as diarrhoea and nasal and ocular discharges (Group C).
KEY WORDS: Goats, management, crop residues, minerals, shelter
Body growth depends on the multiplication of cells, the increase in cell size and accumulation of extra-cellular substances (Edey 1983), the pattern of which is systematic in normal growth and leads to a good animal body condition scoring. In extensive rearing systems, animals often suffer from prolonged periods of malnutrition, especially during the dry season (Oyenuga 1968). Consequently, animal body growth pattern becomes unsteady, animal development often slows and is improportionate and reproductive ability is affected.
The current advocations for the modification of the extensive or traditional system of goat rearing in Nigeria has not only been occasioned by the decreasing availability of grazing lands as a result of population increase and infrastructural development, but also arising from the pressing need to produce goats with good body growth and improved reproductive performances.
The purpose of this experiment was to investigate the growth pattern and reproductive ability of the Nigerian West African Dwarf (WAD) goat in two trials under modifications of the extensive system of management.
Materials and methods
During each of two trials, experiments were commenced on thirty weaned WAD kids comprised of fifteen male and fifteen female goats each estimated at three months of age. The goats weighed between 4.50 to 4.93 kg (mean 4.76 ± 0.16) in Trial I and 4.33 to 5.00 kg (mean 4.74 ± 0.19) in Trial II. Procedures for trials I and II were identical, with the exception of different goats in consecutive years.
Experimental goats were randomly allotted to five management groups of six goats in each group, comprising of equal male and female animals. The management groups were as follows: Group A - provision of simple shelters only, Group B - simple shelters + mineral supplement, Group C - simple shelters + mineral supplement + supplement of crop residues + veterinary care, Group D - simple shelters + mineral supplement + supplement of crop residues, and Group E - completely extensive (free-ranging) (control). The mineral supplement used in this study was manufactured by Kola and Sons Agrochemicals, Ltd., Ilorin, Kwara State. This mineral supplement was popular, cheap and readily available. The stated mineral composition was as follows: NaCl (97%), Mg (400 ppm), Fe (1000ppm), Mn (200 ppm), Cu (400ppm), and P (1.0%).
In each study group, traditional rearing formed the backbone of management, while provision of shelters, supplementary minerals and crop residues, as well as veterinary health care were modifying elements in the management system.
Management of animals
During the study which lasted for twenty weeks across the two seasons of the year, experimental animals were allowed to browse freely within the extensive fields enclosing the University of Ibadan Teaching and Research Farm and parts of Abadina Village lying to the East of the farm which total over 30 hectares. Predominant forage genus included Leucaena, Gliricidia, Centrosema, Panicum and Cynodon species.
Animals in Group A utilized simple shelters to protect themselves from inclement weather and to rest at night, while the goats in Group B, in addition to shelter, were also supplied with mineral supplements. Group C consisted of goats which were provided with a combination of simple shelters, mineral supplement, supplements of crop residues (such as cassava residues, maize stover and leaves of mango and pawpaw trees) and veterinary care. In Group D, the goats were given only shelters and supplements of both minerals and crop residues. Veterinary interventions were simple health care consisting of treatment of conditions such as diarrhoea and eye and nasal discharges which were treated with teramycin soluble powder and chloramphenicol, respectively, especially at the onset of the wet season. Treatment E in the study was a control where experimental animals were completely left to fend for themselves without any modifying intervention.
Records of weekly body weight were taken early in the morning on empty stomach and curves of cumulative body weights were plotted and growth patterns obtained. Reproductive measurements observed were age at puberty and pubertal characteristics in both the male and female goats.
Results and discussion
From the two trials (Tables 1 and 2) optimum daily body weight gains to 20 weeks (or to puberty) were obtained in the group of goats receiving shelter and also provided supplements of both minerals and crop residues (Group D). Results from animals managed extensively (Group E) were poorest and were similar to results obtained in the group of goats which were provided with shelter only (Group A) as a modifying element of the traditional system. Generally, male goats had better body weight gains compared to their female counterparts.
Provision of veterinary health care did not seem to have any additional impact on weight performances of goats as indicated by the generally better results obtained with animals given simple shelters and supplements of both minerals and crop residues (Group D) compared to those provided with the above elements in addition to veterinary care (Group C).
The importance of modifying the traditional system of goat management for improved productivity has been stated (Ademosun 1987; Bonsma et al 1987; Ademosun et al 1985; ILCA 1979), although the role of individual elements in the modifications or their various combinations has not been studied.
Generally, the growth curves did not produce the normal classical sigmoid growth curves said to be expected in growing animals (Edey 1983; Hafez and Dyer 1969). Growth rates were influenced by a combination of factors which included management type, season of the year and physiological state of experimental animals. During the first 4 to 5 weeks of the experiment, browsing goats incurred declines in body weights in their adjustment to the new environment of experiments and experimental processes imposed.
|Table 1: Growth performance of goats under different modifications of the management systems (Trial I)|
|Cumulative daily LW gain (g):**|
* M = male and F = female
** calculated each time from the initial weight.
|Table 2: Growth performance of WAD goats under different modifications of the management systems (Trial II)|
|Cumulative daily LW gain (g):**|
* M = male and F = female
** Calculated each time from the initial weight.
About the end of the 5th week, absolute growth accelerated, but soon began to decline at the onset of the wet season, corresponding to about the 8th week of experiment. Cold signs such as discharges from the nostrils and eyes, were noticed in experimental animals, as well as diarrhoea which was a reflection of the change in the diet of foraging goats and the rains.
The goats required about two weeks (ie between the 2nd week to the 4th week of April) to adjust completely to the change in weather accompanying the onset of the rainy season. It has been stated (Narjisse 1991; Schacht and Malechek 1989; Feldman et al 1981) that during the wet season total dry matter intake of grazing goats is restricted as a result of high water content of herbage, frequent rainfall which reduces grazing time, as well as the effect of chilling and increased disease and parasitic incidences. At puberty, downward inflections of growth curves were noted in the goats, generally between the 18 th and 20 th week across treatments. At this period, male goats were observed to manifest puberty attainment by neglecting browsing in favour of frequent chasing of each other. Complete behavioral manifestations of puberty observed during the study are summarized in Table 3, the components of sexual manifestations being sexual arousal, ritualized display and mounting. Goats which were provided with a combination of shelter and supplements of minerals and crop residues experienced less declines and instabilities in their cumulative growth curves.
|Table 3: Behavioral manifestations of puberty|
|- Rapid wagging of upturned tail, nudging, sniffing, ritualized|
|approach of female, head turned on side with a motion of foreleg.|
|- Nosing the perineum of female.|
|- Courting grunts.|
|- Forelegs extended and flexed in a short choppy kicking motion|
|while standing along-side the female.|
|- Sniffing and licking of female genitalia.|
|- Grunting and attempting to mount females.|
|- Frequent chasing of females, thus spending less time eating.|
|- Sniffing of male body and frequent bladder evacuation.|
|- Frequent micturation stance without successfully urinating.|
|- Bleating and indiscriminate mounting of each other.|
It was observed that goats which enjoyed protection from bad weather, in addition to being given supplements of minerals and crop residues attained puberty at between 14 to 18 days earlier than those animals which were either raised traditionally, or just provided with shelters (Table 4).
|Table 4: Observed physical characteristics relating to reproduction under different management systems|
|Age at puberty**|
*M = male and F = female
**Including estimated age at commencement of study
The provision of veterinary health care made little or no further improvements when the goats in Group C and D are compared. It is a common fact that animals which are provided with adequate nutrition and shelter could exhibit recovery on their own from some conditions which are precipitated by the simple change in weather or diet.
Alert appearance, bright eyes, agility and good hair coats were characteristics of animals which received shelter and supplements of feeds and minerals, and these are desirable features of breeding animals.
The following observations were obvious from the study conducted with WAD goats:
1. Modifications of the traditional system of management are essential for WAD goats in order to obtain both steady and optimum growth, as well as improved reproductive characteristics.
2. A combination of shelter, feeds and mineral supplements should be made the priority in modification of WAD goat management.
3. Under adequate supplementation of minerals in addition to shelter provision, the administration of veterinary care in conditions such as diarrhoea, nasal and ocular discharges as precipitated by seasonal changes may not provide additional benefits as a modification element in the management package of WAD
4. It is recommended that feed supplementation be intensified: (i) at the commencement of the wet season, and (ii) during the period of pubertal attainment in order to improve feed intake and to arrest the downward growth performance.
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(Received 7 May 1995)