N.H. Casey

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.

Genetic differences in fatty acid composition of subcutaneous adipose tissue in Dorper and SA Mutton Merino wethers at different live weights

The effects of breed and slaughter weight on the profile and accumulation of fatty acids in the subcutaneous adipose tissue of wethers were investigated. Dorper (earlier maturing breed) and SA Mutton Merino (later maturing breed) wethers were randomly allocated to a 22 factorially arranged experiment (2 breeds × 2 slaughter weights × 12 replicates). Wethers were slaughtered at either of the two predetermined slaughter weights of 37 or 43 kg. Subcutaneous adipose tissue was sampled for subsequent fatty acid analysis. Thickness of the subcutaneous adipose tissue differed between breeds (P < 0.05) and increased with increasing slaughter weight (P < 0.05). Breed influenced the proportions of myristic (C14:0), heptadecenoic (C17:l) and oleic (C18:1cis) acids, while the effect of slaughter weight was not significant. When breeds were compared at equal body fatness the differences in thickness of the subcutaneous adipose tissue and proportions of heptadecenoic acid (C17:1) and oleic acid (C18:1) were negligible. Concentrations of fatty acids (C14:0, C16:0, C16:1, C18:0 and C18:1) increased (P < 0.05) with increasing live weight. Similar differences were observed between maturity types (breeds) even when compared at an equal degree of maturity, which suggests a genetic basis for differences between these particular sheep breeds.

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).

Influence of freezing method on thaw drip and protein loss of low-voltage electrically stimulated and non-stimulated sheeps' muscle

South African Mutton Merino wethers (n = 32) were slaughtered, yielding carcasses with a mean weight of 22·18 ± 2·11 kg. Sixteen carcasses were electrically stimulated (ES) (21 V, 60 Hz, 120 s) immediately and all carcasses were chilled at room temperature (16°C) for 3 h and then overnight at 4°C, 95% RH. Both left and right Mm. longissimus lumborum et thoracis were excised and cut into six portions (77 g ± 7·8 g), each placed separately in a polyethylene bag and randomly allocated to five freezing treatments. These were: (1) cryogenic, -65°C; (2) cryogenic, -90°C; (3) walk-in-freezer, -21°C; (4) blast freezer, -21°C; (5) domestic freezer, -25°C. The respective freezing rates were 4·4, 6·4, 0·55, 0·35 and 0·51 cm h(-1) to -2·2°C at core depth of 1 cm below the surface. Samples were frozen to core temperatures of -20°C, removed and placed in a storage freezer (-20°C) for 48 h and 2·5 months. Samples were then suspended in perforated bags in a chiller (4°C) to thaw, and drip was collected in outer bags over the periods 0-24, 24-48, 48-72 and 72-96 h and expressed as g (100 g)(-1). Freezing methods had significant (P < 0·01) influences on drip loss in both ES and NES samples. Following storage for 48 h post-freezing at -20°C, total drip (g (100 g)(-1)) over 96 h of both ES and NES samples for the five freezing treatments were respectively: (1) 7·61 and 4·61; (2) 7·35 and 3·29; (3) 9·44 and 4·68; (4) 9·07 and 5·43; (5) 10·58 and 5·15. Following storage for 2·5 months, the total ES and NES drip were respectively, (1) 11·25 and 9·38; (2) 10·36 and 9·15; (3) 13·72 and 12·65; (4) 13·70 and 12·26; (5) 11·92 and 11·29. Total protein in the drip did not differ between freezing treatments. Differences between ES and NES samples did occur in the 48 h storage group. It is concluded that cryogenic freezing results in less thaw drip than the vapour compression systems. This advantage of cryogenic freezing disappears if meat is stored for long periods at -20°C. Electrical stimulation increases the drip loss in samples frozen for 48 h, but the differences are not significant after 2·5 months frozen storage. Protein losses parallel the drip.

Influence of dietary energy levels and form of diet on composition of fatty acids in subcutaneous adipose tissue of wethers

Abstract Effects of dietary energy levels and form of diet on the profile and accumulation of fatty acids in subcutaneous adipose tissue of wethers were investigated. Shorn wethers were randomly allocated to a 2 2 factorially arranged experiment (2 dietary energy levels × 2 dietary presentations × 14 replicates). Two diets were compiled on an isonitrogenous and isomineral basis to contain a medium (M) and high (H) level of metabolisable energy. Diets were presented in either loose or pelleted form and were fed ad libitum to the wethers from an initial weight of 24.9 ± 3.9 kg. Wethers were slaughtered at a predetermined slaughter weight of 43 kg and the subcutaneous adipose tissue was sampled for subsequent fatty acid analysis. Results suggests that dietary energy levels influence mainly the profile, rather than the amount of fatty acids deposited or synthesised. The latter appears to be a function of the degree of maturity of the animal and its residence period (length of grain feeding). It appears that the balance between the proportions of saturated and unsaturated fatty acids becomes increasingly important as greater concentrations of fatty acids accumulate in the subcutaneous adipose tissue. Results also suggest that the pelleting of high density diets may shorten the residence period and limit the accumulation of displeasing concentrations of unsaturated fatty acids in subcutaneous adipose tissue, which may yield more acceptable carcasses.

Fatty acids in carcass fat of steers treated with a β-adrenergic agonist individually or in combination with trenbolone acetate + oestradiol-17β.

Forty steers of medium maturity were allocated randomly to four treatment groups of 10 steers each (C = Control, βA = β-Agonist, TO = Trenbolone acetate + oestradiol-17β and βTO = β-Agonist in combination with trenbolone acetate + oestradiol-17β). After 56 days on treatment, the β-Agonist treatment was stopped and the steers slaughtered on the ninth day after withdrawal. Samples of subcutaneous fat over the 13th rib and M. longissimus dorsi were stored in sealed polyethylene bags at -20 °C for fatty acid analysis. A greater proportion of oleic acid (C18: 1, P < 0.05) was deposited in the subcutaneous fat of steers treated with βA as opposed to those treated with either TO or βTO. Treatments altered the fatty acid composition of the M. longissimus dorsi, particularly through their effects on palmitic acid (C16:0, P < 0.01), palmitoleic acid (C16:1, P < 0.01) and oleic acid (C18:1, P < 0.01). The results suggest a shift (P < 0.01) towards saturated fatty acids in the M. longissimus dorsi of steers treated with either βA or βTO.