W.A. van Niekerk

The boer goat. I. Origin, adaptability, performance testing, reproduction and milk production

Abstract Boer goats evolved in Southern Africa from indigenous African and introduced European stock. Breed standards of the Boer Goat Breeders Association stipulate color to be white with red head and blaze, pigmented skin and good, functional conformation. Boer goats are hardy, graze a wide spectrum of plants, grasses and shrubs, effectively combating bush encroachment, have low water turnover rates and low internal parasite infestation. Does are early breeders, polyoestrous and may be synchronized with intravaginal progestogen or PMSG. A 70% kidding rate is reported with AI. Anaplasma ovis infection of does, transmitted transplacentally to the fetus causes abortions and neo-natal mortalities. Milk yield averages 1.5 to 2.5 kg/day with 43 g/kg protein and 77 g/kg fat contents. Libido and semen quality of bucks varies seasonally. Performance testing aims to measure dams characteristics pre- and post-weaning, feed efficiency of kids under standardized conditions, and qualitative and quantitative carcass evaluation of sires progeny. The future of Boer goats lies in performance testing for economically important traits.

The Boer goat. II. Growth, nutrient requirements, carcass and meat quality

Abstract Growth rates of Boer goats were generally lower than sheep and, under favorable nutritional conditions, weight gains of more than 200 g per day were obtained, against values of up to 176 g per day under extensive subtropical conditions. Lactation and pregnancy had a marked effect on ME intake, and the latter had an improved feed conversion ratio (6.06 kg/kg) in comparison to that of virgin does (10.96 kg/kg). Below 6% crude protein in the diet, feed intake is reduced and has negative effects on birth weights, growth and milk production. Little information is available on mineral requirements of goats. The carcass of Boer goats is generally leaner, less compact and has different carcass proportions than sheep. The relatively high collagen contents with lower solubility of Boer goat meat, has meant that the eating quality has been regarded as inferior to that of lamb and mutton. Breeding holds the key to improving tenderness of goat meat; different slaughtering techniques can be used as well. Boer goats have high potential as meat animals when yielding three kid crops in 2 years and when fed to gain more than 200 g/day.

Fatty acids in the subcutaneous adipose tissue of intensively fed SA Mutton Merino and Dorper wethers

Recent ambiguity about the role of animal fat in causing coronary heart disease, coupled with the controversy regarding the effect of various levels of energy nutrition on ruminant depot fats, prompted an investigation into the influence of high-energy nutrition, breed and slaughter weight on the fatty acid profiles of ruminants. Two isonitrogenous and isomineral diets containing 11·76 MJ ME/kg DM and 10·18 MJ ME/kg DM were fed to Dorper and SA Mutton Merino wethers of ± 20 kg to 37 and 43 kg live weight. Subcutaneous fat samples and feed samples were collected for fatty acid analysis. Treatment significantly affected the subcutaneous fatty acid profiles of wethers, which includes C15:0, C16:0, C17:0, C17:1, C18:0, C18:1, C18:2 and C18:3. Treatment also influenced the concentration of saturated and unsaturated fatty acids in the subcutaneous adipose tissue as well as the concentration of trans-fatty acids. The results obtained suggest that dietary energy levels may significantly affect the fatty acids in the subcutaneous fat of wethers. Breed differences, after correcting for carcass fatness, occurred in C16:0.

Fatty acid composition of subcutaneous fat of sheep grazed on eight different pastures.

The levels of eight long chain fatty acids (14:0, 16:0, 16:1 17:0, 17:1, 18:0, 18:1, 18:2) were measured in the subcutaneous fat of S.A. Mutton Merino wethers (5 months old, 20-25 kg live mass, 8 per treatment) and, including 18:3, in eight pastures grazed for 84 days (maize stubble, Z. mays; Triticale; L. multiflorum; L. perenne; D. glomerata; D. eriantha; C. dactylon; M. sativa). Respectively, percentage fatty acid contents of subcutaneous fat and pastures were 14:0 5·04 ± 0·86 and 0·67 ± 0·37, 16:0 22·85 ± 0·81 and 17·83 ± 3·00, 16:1 2·07 ± 0·22 and 2·42 ± 1·17, 17:0, 1·68 ± 0·04 and 0·42 ± 0·16, 17:1 0·75 ± 0·06 and 0·17 ± 0·19, 18:0 25·94 ± 2·02 and 4·95 ± 1·68, 18:1 32·27 ± 0·93 and 8·12 ± 11·70, 18:2 1·59 ± 0·36 and 15·89 ± 5·16, 18:3 measured in pastures only 34·51 ± 15·91. The palmitoleic acid (16:1) content of pastures increased (P < 0·05) as the ether extractable lipid content of the pastures increased. Pasture treatments influenced the levels of 14:0, 17:1 and 18:2 highly significantly (P < 0·01) and of 18:0 significantly (P < 0·05). Increasing levels of fatness of ribcut samples were associated with a decrease in 14:0 and an increase in 17:1 (P < 0·01) and an increase in 18:2 (P < 0·05).

Voluntary intake of several planted pastures by sheep and an assessment of NDF and IVDOM as possible predictors of intake

The aim was to study the quality and quantity of pasture selected by sheep on various planted pastures. A further aim was to assess NDF and IVDOM as easy measurable parameters for use in equations to predict intake. Pasture samples were collected using oesophageal‐fistulated sheep and from knowledge of the in vitro digestibility of these samples and the total faeces voided as measured with faeces bags, intake was calculated. Pastures observed included ryegrass, cocksfoot, C. dactylon, Smuts finger, triticale, E. curvula, Eragrostislucerne combination, lucerne and sainfoin. Nitrogen content of oesophageal samples varied between 2,3 and 5,1%, NDF between 33 and 65% and IVDOM between 50 and 80%. Intake of grass DOM varied from 24,4 to 43,3 g/kg W0,75/day for lambs and from 29,0 to 37,4 g/kg W0,75/day for mature wethers. DOM intake on the two legumes was generally poor and varied between 13,7 and 22,9 g/kg W0,75/day. Although some of the variation in voluntary intake is accounted for by the variation in NDF a...

Qualitative evaluation of four subtropical grasses as standing hay: diet selection, rumen fermentation and partial digestibility by sheep

The nutritive value of four subtropical grasses (Panicum maximum, Anthephora pubescens, Digitaria eriantha and Chloris gayana) standing hay were compared in terms of qualitative intake and partial digestibility by sheep. The species differed significantly in terms of diet quality selected by sheep grazing the standing hay. The rumen ammonia nitrogen (NH3-N), total volatile fatty acid and propionic acid concentrations of sheep grazing P. maximum and A. pubescens were higher than those sheep grazing D. eriantha and C. gayana standing hay. Organic matter intake (OMI) (g kg−1 W0.75 d−1), nitrogen intake (g d−1), digesta flow, the total N flow, NH3-N flow, non-ammonia nitrogen (NAN) flow and NAN disappearance (g d−1) in the ileum were higher for sheep grazing P. maximum than for those grazing the other standing hays. The organic matter disappearance in the stomach and small intestine of sheep grazing P. maximum and D. eriantha standing hay was higher than for those sheep grazing either A. pubescens or C. gayana standing hay. The NAN flow/N intake were the highest for sheep grazing P. maximum and A. pubescens compared to C. gayana. The NAN digestibility was, however, not significantly different among the four species. The standing hays (except for C. gayana) seemed to have the capacity to meet the N requirement of the sheep for production, but the OMI (g kg−1 W0.75 d−1) was not sufficient to support maintenance requirement of the sheep.

Influence of moisture stress on growth, dry matter yield and allocation, water use and water-use efficiency of four Indigofera species

The effects of moisture stress were evaluated in four Indigofera species (I. amorphoides, I. arrecta, I. coerulea and I. vicioides) using a pot experiment under glasshouse conditions. The aim was to examine the influence of moisture-deficit stress on physiological attributes and performance of the four Indigofera species. Based on plant available water (PAW) levels, three moisture levels were applied (no stress or 70–100% PAW, 40–70% PAW and 10–40% PAW) as experimental treatments and imposed on each species in a randomised complete block design with four replications. Moisture stress significantly reduced (p < 0.05) the total leaf area of I. amorphoides at moderate levels and that of I. vicioides at the most severe moisture stress level. The relative growth rate was significantly reduced (p < 0.05) in I. amorphoides but not in I. arrecta, I. coerulea or I. vicioides plants subjected to moisturedeficit stress. The reduction in total dry matter yield was due to the effect of moisture stress in reducing both leaf area and leaf area ratio. Drought stress-tolerance indices were not different (p > 0.05) for I. arrecta or I. coerulea grown under no stress and moisture-deficit stress conditions. The root mass fractions of I. amorphoides and I. arrecta were substantially increased (p < 0.05) due to moisture stress. Water-use efficiency was low in I. amorphoides under water deficit conditions, while that of I. vicioides was higher under severe stress conditions compared to non-stress conditions. Transpiration efficiency was, however, higher at moderate moisture-deficit stress levels than under non-stressed or severely stressed plants. Generally, the species investigated exhibited significant variation in terms of physiological attributes and performance response to moisture-deficit stress. Indigofera amorphoides was relatively sensitive while I. vicioides was able to maintain unabated growth under water stress conditions. This is highly relevant to programmes aimed at identifying suitable species as a source of fodder for livestock exposed to long dry seasons and frequent drought phenomena.

Influence of molasses additive and moisture level at ensiling on fermentative characteristics of Panicum maximum

Silages made from directly cut or wilted Panicum maximum treated with or without molasses, were evaluated to determine fermentative characteristics. The grass was harvested at the boot stage of growth and the material of each treatment was ensiled in separate 1kg mini-silos. Compared to day 0 (control), silage pH dropped significantly at day 7 for molasses-treated silage regardless of initial moisture level. In the untreated silage a slightly lower pH was recorded for the unwilted silage. Molasses treatment resulted in a lower silage pH, higher lactic acid and lower acetic acid concentrations starting from day 7 throughout the fermentation period. Compared to prior wilted silages, lower (p < 0.05) pH, higher lactic acid and lower acetic acid concentrations were recorded for directly cut silages throughout the fermentation period. Molasses had no influence on the nitrogen (N) content of silage, but wilting resulted in a higher N content compared to unwilted silage in presence of molasses. Neither the influence of molasses nor the initial moisture level had a significant effect on ammonia nitrogen (NH3-N) concentration on day 7, but an interaction between molasses addition and moisture level was evident on day 21 and 120. The level of ammonia nitrogen increased with fermentation time. The addition of molasses seemed to be beneficial to the fermentation process and resulted in well preserved silage, whereas the effect of initial moisture condition seems to have little significance.

A note on the potential nutritive value of Ziziphus mucronata (buffalo thorn) foliage during different seasons

Foliage of Ziziphus mucronata (buffalo thorn) was collected during the spring, summer and autumn. The chemical composition and in vitro digestibility of organic matter (IVDOM) of these samples were determined. Crude protein concentration ranged between 123–262 g kg DM−1, and tended to be higher in spring than in the other seasons. The acid detergent fibre ranged between 175–312 g kg DM−1 and also tended to be higher in autumn than in either spring or summer. The IVDOM values in this study were high (>700 g kg DM−1) compared to values reported in literature for the same species and other browse species such as Cassia sturtii, Tripteris sinuatum and Sutherlandia microphylla. The concentrations of calcium (Ca), sodium, zinc and manganese (Mn) appear to be higher in autumn while the concentrations of phosphorus (P), magnesium (Mg), potassium and copper (Cu) tended to be lower at this time compared to other seasons. In spring, the concentrations of Ca and Mn appear to be low while those of P, Mg and Cu are relatively high compared to the other seasons. However, the P content of Z. mucronata foliage was deficient in summer and autumn, while Cu was deficient in all seasons.

Influence of mineral composition and rumen degradability of Atriplex nummularia (Hatfield Select F1) plants on selection preference of sheep.

This study examined intraspecific variation in mineral composition and rumen degradability of Atriplex nummularia plants and the influence on selection preferences of sheep. Individual plants were categorised into high, medium and least preference groups by assessing the order in which they were selected by sheep. Nine plants were selected from each group and the regrowth of these plants was analysed for neutral detergent fibre (NDF), crude protein (CP), mineral composition and rumen degradability of dry matter. The data was subjected to one-way and multivariate analyses of variance. Highly preferred plants had a higher concentration of CP, phosphorous (P) and magnesium (Mg) in their edible forage compared to the medium or least preferred plants. Individual preferences of sheep were not, however, associated with the rumen degradability parameters. Principal component analysis revealed that highly preferred plants had lower NDF, manganese (Mn) and zinc (Zn), and higher CP, calcium, P, Mg and potassium values compared to the least preferred plants. In contrast, medium preferred plants exhibited inconsistent patterns, with a tendency to have higher sodium chloride and sodium, and lower Mn, Zn and copper, concentrations in the forage.