Daniel Van Der Merwe

• PhD Agriculture (Animal Science)
• Kemin Industries

Feed intake models seldom take breed differences into account. This study investigated various approaches to describing and predicting the feed intake of certain breeds (Dohne Merino, Dormer, Dorper, Meatmaster, Merino, South African Mutton Merino (SAMM) and White Dorper). On weaning at 90 days old, four ram and four ewe lambs from each breed were...

Subcutaneous fat (SF) and Longissimus thoracis et lumborum muscle (LM) depths of growing lambs from six breeds were monitored. Ram and ewe lambs from Dohne Merino, Dormer, Dorper, Meatmaster, South African Mutton Merino and White Dorper breeds were reared together under optimal feedlot management conditions and were subjected to ultrasound scans ev...

Average temperatures are likely to increase, resulting in hotter and dryer conditions in South Africa. The impact of these changes on animal production and welfare is not well-defined. Two trials were conducted to determine the homeothermic response of eight sheep breeds. In 2016, the study included seven breeds, namely Dohne, Dormer, Dorper, Meatm...

This study aimed at estimating models to predict the growth and feed intake of Bonsmara bulls and heifers in backgrounding or pasture-based production systems (Ethical clearance number A16-SCI-AGR-001). Growth and intake data were collected from the Kromme Rhee Bonsmara stud in the Stellenbosch region. The growth curves of steers and heifers were m...

This preliminary study investigated the provision of shade on heat stress indicators of South African Mutton Merino (SAMM) and Dormer lambs shortly after birth, during the autumn 2017 and 2018 lambing seasons. Newborn lambs were assessed to determine whether welfare, as assessed by respiratory response and rectal temperature as heat stress indicato...

In order to investigate the physical leather quality characteristics of different sheep breeds, skins were obtained from Dohne Merino, Dormer, Dorper, Meatmaster, Merino, South African Mutton Merino (SAMM) and White Dorper yearlings from two separate growth studies. The cured skins were stored for 18 months (Group 1) and 9 months (Group 2) prior to...

In this study, the wool growth of Dohne Merino, Dormer, Merino and South African Mutton Merino (SAMM) lambs reared on a feedlot diet (10.62 MJ ME/ kg feed, 20.7% crude protein) was monitored from about two months old until the lambs were shorn as yearlings. The 100 cm 2 patches on the left sides of the lambs were sheared monthly and the clippings w...

In the intensification of sheep production systems, feedlot finishing plays a fundamental role in preparing lambs for slaughter, as well as relieving the grazing pressure on pasture. The profit margins in feedlot operations are often narrow and require the economics of scale to generate a sufficient income. In order to minimise expenses, intensive...

An increasing number of producers opt to finish their lambs in on-farm feedlots. Therefore, detailed production information is required to implement precision finishing of lambs of different genotypes. Precision finishing monitors growth, feed intake and efficiency to optimize management. In this study, feedlot production characteristics of Dohne M...

Accurate diet formulations are required to fulfil the nutrient requirements of birds in order to achieve optimal production. Knowing how the skin, nodule and feather production characteristics vary with diets of different nutrient densities will help in least-cost modelling. Feather growth and nodule development are factors that were previously neg...

This research sought to develop a mathematical model to predict the growth and feed intake of Boer goat kids destined for slaughter. Data were collected from castrated kids that were housed in individual pens and fed diets that varied in energy content (11.3, 12.0, and 12.7 MJ metabolizable energy (ME)/kg feed). Growth and feed intake were monitore...

The effect of production systems on the sensory quality characteristics of Dorper lambs was investigated. Sixty lambs (ewes, rams, castrates) were allocated into two production groups (feedlot or free-range) at weaning with equal numbers of each sex represented in each group. The lambs were fed for five (slaughter group 1) or six (slaughter group 2...

This study compared the carcass characteristics of ram and ewe lambs from South African wool, dual-purpose, meat, and fat-tailed sheep types, reared to produce premium lamb carcasses. The lambs were reared on a feedlot diet (10.41 MJ ME/kg feed and 19.06% crude protein) from weaning (30 kg live weight) until they attained a back-fat depth of ~4 mm,...

In order to determine the growth trends of seven sheep breeds that are popular in South African commercial production systems (Dohne Merino, Dormer, Dorper, Meatmaster, Merino, SA Mutton Merino and White Dorper), body weight data was collected from lambs of each breed from birth until they were assumed to have attained maturity at one year of age....

This study compared the effects of different dietary energy contents (11.3, 12.0 and 12.7 MJ ME/ kg feed) fed ad libitum in a feedlot on the carcass quality characteristics (carcass yield, commercial yield, 3-rib cut) of goats introduced to feedlot at 22.2 ± 3.5 kg (18 weeks of age), and slaughtered at five week intervals. The energy content of the...

Information on feather and skin growth is important for the development of mathematical optimisation nutritional models for ostriches. Ostriches (n = 65) were subjected to a four-stage formulated growth diet programme (pre-starter, starter, grower and finisher), with declining protein and energy content. Nine birds were weighed, stunned, exsanguina...

The objective of this study was to determine the effect of time spent in a feedlot on the size of the various fat depots and the distribution of the main tissues (muscle, bone, and fat) of three common South African sheep breeds. Lambs were supplied with a balanced diet (16% protein, 10 MJ ME/kg feed) ad libitum and had free access to water. Lambs...

The palatability and chemical composition of Longissimus lumborum muscles from 24 Boer goat castrates (eight goats per treatment), finished on diets varying in energy content (9.7, 10.2 and 10.6MJ ME/kg feed), were evaluated by a trained sensory panel on a line scale ranging from low to high intensity for aroma, flavour and texture attributes. Phys...

The effects of three dietary energy treatments on the feedlot production characteristics of Boer goats were investigated, along with the time spent under feedlot conditions. A total of 66 goat kids with an average weight of 22.2 ± 3.51 kg were housed in individual pens at Elsenburg research farm. At the start of the trial, the goats were randomly a...

This study investigated the effect of feedlot production on lamb growth characteristics of three common South African breeds: Merino, South African Mutton Merino (SAMM) and Dorper. Lambs were supplied with a balanced diet (16% crude protein, 9.41 MJ ME/kg feed) ad libitum and had free access to water. Lambs from each breed were divided into six gro...