The continuing search for improved efficiency has led to the introduction of exogenous growth and lactation promotants to enhance traditional animal production systems. Various species-limited somatotropins have been synthesized by means of recombinant gene technology, thereby allowing milk production in…
Components for a simulation model are described to predict feed intake, amino acid requirements and body composition changes over time on the basis of the inherent potential protein growth rate of pigs varying in genotype. The potential protein growth rate…
Data collected from Nguni calves born at the Bartlow Combine Breeding Station were used to investigate factors affecting live weights at birth (1960-1991), 205 days (1960-1991), 365 days (1974-1990) and 540 days (1975-1990) of age. Sire, year of birth, sex…
The effect of melatonin implants, flushing and teaser rams on the reproductive performance of spring-mated Dohne Merino ewes was investigated. The ewes (n = 534) were randomly allotted to four treatments, namely (1) no treatment (control), (2) melatonin implants (melatonin),…
Two Merino lines were established in 1988 and were subjected to divergent selection for maternal ranking values on lambs weaned/ ewe joined (Lw/Ej). Replacements with high values were selected in the Reproduction `+` line, while progeny of low ranking ewes…
Factors influencing the recalving rate of 2 165 lactating beef cows of four pure breeds (Afrikaner, Hereford, Bonsmara and Simmentaler) and three cross-bred types were investigated on the Mara Research Station between 1972 and 1982. Average recalving rate was 88.3%…
One hundred and thirty Merino ewes were used to test the efficiency of different doses of medroxyprogesterone acetate (MAP) progestagen to synchronize oestrus outside the breeding season. Three treatments, consisting of intravaginal progestagen doses (60 mg, 40 mg, and halved…
The in vitro ammonia production and ruminal in situ disappearance of dry matter, organic matter, protein and ether extract of heat-treated whole cottonseed were determined. Abomasal flow of nitrogen and ether extract and terminal ileal flow of lysine and methionine…
The study was conducted to determine the effect of whole cottonseed (WCS), heat-treated whole cottonseed (HWCS), and whole cottonseed plus lanolin (WCS + Q on feed intake, milk production and milk composition. Eight Holstein heifers in early lactation were fed…
The effect of a shade structure on the feed intake, water intake, milk production and milk composition of Dutch-type Friesian cows in a temperate climate was determined over three summer seasons. The shade structure reduced (P < 0.01) radiation as…
The effect of a shade structure on some physiological parameters of lactating Dutch-type Friesian cows was determined over three consecutive summer periods. Plasma cortisol concentration of no-shade cows was significantly (P < 0.05) higher than that of shade cows during…
The effect of a shade structure on the behaviour of lactating Friesian cows in open camps (dry lots) was determined over two consecutive summer periods. The daily activities of cows were observed and recorded on 9 separate 24-h periods. Shade…
A system of feeder–breeder dimorphism (large, fast growing offspring in feedlots obtained from small, low mainten¬ance cows on natural pastures) would be profitable in South Africa. The possibility of a genetic basis for feeder–breeder dimorphism was estimated by calculating genetic…
Heritability estimates for Kleiber ratios associated with growth were obtained for a Hereford stud, subjected to selection for growth over an 11-year-period. Heritability estimates obtained indicate that growth efficiency in terms of the Kleiber ratio is moderately heritable.
The performance of Bonsmara bulls tested in Phase C of the South African Performance Testing Scheme (intensive test in which individual feed intakes are measured) was compared with the performance of the half-sib bulls tested in Phase D (comparable to…
A study was conducted to examine the effect of using Henderson`s (1988) `average numerator relationship matrix` (ANRM) on the prediction error variance (PEV) of breeding values obtained using an animal model with maternal effects. Genetic trends with and without using…
The diet of free ranging Angora goats in a False Upper Karoo veld type in the south-western Orange Free State is described. Angora goats are inherent browsers feeding on a wide variety of plants. Based on utilization frequency and feeding…
