Selenium (Se) supplementation on the Se status of dairy cows in the Midlands of KwaZulu-Natal

A dose-response trial was conducted with dairy cows on six farms in the Ixopo district of the Midlands of KwaZulu-Natal. Up to 30 cows per farm received a single subcutaneous injection of 5 mL of a long-acting/slow-releasing selenium (Se) supplement containing 50 g Se as barium selenate/mL (Deposel). The same number of matching cows per farm was used as controls. The cows grazed cultivated pastures and received concentrates containing no added Se. Whole blood Se concentrations were determined on day 1 and at ca. three month intervals thereafter. The investigation was conducted for periods ranging from between 300 and 400 days on the different farms. Incidences of retained placenta, metritis, cystic ovaries, mastitis and calf mortality were recorded. Whole blood Se concentrations of the unsupplemented cows ranged from 17 to 90 ng/mL. Accepting that a concentration of >200 ng/mL blood indicates an adequate Se intake, the recorded concentrations suggest that the cows were deficient to marginally deficient in Se. The parenteral Se supplementation at the prescribed dose increased blood Se concentrations by an average of 32.8 ng/mL, but this was insufficient to raise blood Se concentrations to adequate or recommended levels for dairy cows. No significant differences were recorded on the incidence of retained placenta, metritis, cystic ovaries, mastitis and calf mortality. It was concluded that, if not supplemented, dairy cows grazing cultivated pastures in the Ixopo district of KwaZulu-Natal are likely to be deficient to marginally deficient in Se. However, the prescribed dose of 5 mL of the slow-releasing Se supplement was too low to overcome the deficiency. Keywords: Dairy cows; selenium; Ixopo; parenteral supplementation; Deposel South African Journal of Animal Science Vol. 36 (5) 2006: pp.18-2

The chemical composition and potential nutritive value of the foliage of four subtropical tree species in southern Africa for ruminants

The foliage of three Combretum species, C. apiculatum, C. molle and C. zeyheri, as well as that of Colophospermum mopane was collected over a period of two years. The chemical composition, in vitro organic matter digestibility (IVOMD) and the rumen degradability of dry matter (DM) and nitrogen (N) were determined on these samples. Mean values for crude protein (CP) concentration varied from 92 g/kg DM for C. molle to 141 mg/kg DM for C. mopane, the neutral detergent fibre concentration from 323 g/kg DM for C. apiculatum to 392 g/kg DM for C. molle and that of acid detergent fibre from 247 g/kg DM for C. apiculatum to 355 g/kg DM for C. molle. The calcium (Ca) concentration in the foliage was high (8-16 g/kg DM) compared to the phosphorus (P) concentrations of between 0.8-2.1 g/kg DM, resulting in an average Ca: P ratio of 9.3: 1. The foliage contained relatively low levels of sodium (Na), 0.041 g/kg DM, based on beef cattle standards. The IVOMD ranged from 53% for C. mopane to 64% C. apiculatum and the rumen degradability of DM from 78% for C. molle to 94% for C. apiculatum. The DM degradability was substantially higher than that of nitrogen, which varied between 47% for C. apiculatum and 60% for C. zeyheri. It was concluded that the foliage tested would not be suitable sources of N to supplement protein deficiencies in low quality herbage. Furthermore, browsers would require additional sources of P and Na to avoid deficiencies in these elements. Keywords: Leaves, Combretum species, Mopane, Ruminal degradability, In vitro digestibility, Browse South African Journal of Animal Science Vol.33(2) 2003: 132-14

The use of n-alkane markers to estimate the intake and apparent digestibility of ryegrass and Kikuyu by horses

The n-alkane marker (dosed marker, dotriacontane, C32, herbage markers C31, C33 and C35) technique was evaluated for use in feed intake and digestibility studies with horses. The mean retention time of digesta in the digestive tract was determined in horses following a single dose of C32. The n-alkane technique was then employed to estimate dry matter intake and digestibility in horses fed fresh perennial ryegrass (Lolium perenne), fresh Kikuyu grass (Pennisetum clandestinum, Hochst) and Kikuyu hay. The mean retention time of the C32 marker in the horses was estimated to be 27.9 h. On average the C32 had a slightly greater faecal recovery of 0.89 than the odd-chain alkanes (0.80-0.85), though the differences were not significant. The alkane technique, using the n-alkane markers, gave good estimates of dry matter intake, e.g. for fresh ryegrass the measured intake was 8.86?0.23 kg and the estimated intakes from the C31:C32 ratio, 7.9?1.9 kg and from the C32:C33 ratio, 8.3?1.4 kg. However, the effect of the higher recovery of the dosed marker needs further investigation. The estimates of apparent dry matter digestibility corresponded well with measured values, provided the factor for the incomplete faecal recovery of the internal alkanes was included in the calculation. It was concluded that the alkane technique is suitable to estimate feed intake under grazing conditions. However, the proportion of dietary alkanes recovered in the faeces has to be known to obtain an accurate estimate of apparent digestibility. This would be a problem under grazing conditions when faecal grab samples are taken for measuring faecal alkane concentrations. South African Journal of Animal Science Vol.32(1) 2002: 50-5

Potential benefit of trace element supplementation of sheep on a low level of nutrition

A study was conducted to test whether supplementation of trace elements would have any beneficial effect on year-old ewes receiving a submaintenance level of nutrition. The ewes were fed a poor quality hay. The control group received no supplementation (Treatment 1). A solution containing copper (Cu, 5 mg/d), selenium (Se, 1.6 mg/d) and zinc (Zn, 48.2 mg/d) was dosed twice a day to sheep in Treatment 2 while the ewes in Treatment 3 received a double dose of the three elements. Tissue analyses at the end of the 93-day experimental period suggested that the lambs in the control group suffered from a marginal Se deficiency, while the intake of the other elements seemed to be sufficient. Within treatments, weight changes varied tremendously. Therefore, even though differences were not significant, the unsupplemented control group lost weight, while the sheep in the other two treatments maintained their initial body weights during the study. Likewise, the control group tended to have a lower immune response against an injected foreign protein than the supplemented treatments, though differences were not significant. Plasma in the control group showed significantly higher activities of creatine phosphatase and aspartate transaminase than the supplemented groups. This suggested that the supplemented elements protected the body against tissue damage. Although it is traditionally considered that deficiencies in energy and protein, as first limiting nutrients with the highest priority in nutrition, should be overcome before any response to trace element supplementation could be expected, many of the micronutrients are involved in antioxidant activities in the body. Results from this study suggested that positive responses to micronutrient supplementation could be possible if the body is subjected to oxidative stress during submaintenance levels of energy and/or protein nutrition. South African Journal of Animal Science Vol. 36(1) 2006: 20-2

Effect of method of sample preparation on ruminal in situ disappearance of dry matter and nitrogen in annual ryegrass in dairy cows

The objective of this study was to investigate the effect of method of sample preparation on the degradation kinetics of herbage when applying the in situ technique. Ryegrass (Lolium multiflorum cv. Midmar) was harvested at three and four weeks after cutting and fertilizing with 200 kg nitrogen (N)/ha. Freshly cut herbage was used to investigate the following four sample preparation methods. In trial 1, herbage was (1) chopped with a paper-cutting guillotine into 5-10 mm lengths, representing fresh (FR) herbage; (2) chopped and stored frozen at –20 °C in a chest freezer, representing frozen (FN) herbage; (3) chopped, stored frozen at –20 °C for 12 h followed by freeze drying for 48 h and thereafter milled through a 2 mm screen, representing freeze dried (FD) herbage and (4) chopped and oven dried at 65 °C for 48 h and thereafter milled through a 2 mm screen, representing oven dried (OD) herbage. Prepared samples were incubated in three rumen cannulated, lactating Holstein-Friesian cows. The dry matter (DM) and N loss (%) of the FR, FN, FD and OD herbage differed significantly at 0 and 5 hours incubation but not at 24 or 48 hours. Sample characteristics (particle size, wet or dry sample) clearly influenced the degradability of herbage DM and N. Frozen herbage showed similar degradation characteristics to fresh herbage. In trial 2, ryegrass samples were prepared by the same four methods, but at a standardized particle size, namely, chopped into 5–10 mm lengths. The treatments were: chopped fresh, chopped frozen, chopped freeze dried and chopped oven dried. The N losses differed significantly between treatments for the 0, 5 and 10 hour incubations, but not at the 22 and 46 hour incubation periods. Although the a, b and c fractions differed significantly between treatments, the effective degradability did not differ for fresh, frozen and freeze dried chopped samples. Oven dried chopped samples had reduced effective degradability and are not recommended for determining effective degradability. It is proposed that fresh chopped herbage be used in degradability studies.. Keywords: Ruminal disappearance; degradability; nitrogen; annual ryegrass;dairy cows South African Journal of Animal Sciences Vol. 35 (2) 2005: pp.126-13

Milk iodine determination: The suitability of milk samples collected in the South African Milk Recording Scheme

No Abstract

Effect of fibre and nitrogen content on the digestibility of Kikuyu (Pennisetum clandestinum)

No Abstrac

Mineral composition of poultry manure in South Africa with reference to the Farm Feed Act

No Abstrac

Selenium concentration of maize grain in South Africa and possible factors influencing the concentration

A total of 896 maize grain samples were obtained from all the maize silos throughout South Africa (231 silos) and analysed for selenium (Se) content. This information was used to compile a regional distribution map of the Se content of maize grain in South Africa. Of the samples analysed, 94% contained below 50 μg selenium/kg DM and can thus be classified as deficient from an animal and human nutritional point of view. Maize grain in South Africa is therefore a poor source of Se for animals and humans. The geographical distribution of Se values of maize grain is consistent with that of previous studies on the Se status of herbivores in South Africa, suggesting that plants growing in most of the maize-producing areas of the country contain low concentrations of Se. However, these findings contradict those of the soil Se status in the country as reported by the Agricultural Research Council’s Institute for Soil, Water and Climate, which states that the eastern part of the maize-producing areas of the country tends to have adequate to high soil Se levels and the western areas to have low levels. These contradictory results can be explained to a large extent by the varying soil pH throughout the country. Soil pH plays a primary role in the availability of selenium to plants. Although the eastern parts of the country tend to have high Se concentration in the soil, it is not available to the maize plant owing to a low soil pH, while in the western parts of the country, where soil pH may be suitable for Se uptake by plants, there seems to be an inadequate concentration of available Se in the soil.Keywords: Geographical map, soil pH, white maize, yellow maiz

Changes in nutrient composition of kikuyu foggage as winter progressed

Samples of kikuyu foggage (standing hay) were collected in northern KwaZulu-Natal from five adjoining paddocks to measure the changes in nutrient composition of the foggage as winter progressed. Leaves and stems were separated. The first samples collected on the 18th of May contained green to dry material at a ratio of 3 : 1 and that was reduced to practically no green material in July. Although the proportion of leaf decreased from 64.6% to 56.8% as winter progressed, differences were not significant. Crude protein (CP) levels and effective dry matter degradation decreased significantly with time while neutral and acid detergent fibre levels increased. The calcium (Ca) and phosphorus (P) concentrations in the leaves decreased significantly between the first collection and later collections, while these changes were less pronounced in the stems. At all stages the stems contained significantly lower concentrations of Ca than the leaves, while P concentrations between leaves and stems did not differ. Consequently, the Ca : P ratios in the leaves varied between 2.08 and 1.60 and that of the stems between 0.74 and 1.10. These results suggest that the significantly lower Ca levels in kikuyu stems compared to leaves could make a significant contribution to the variation in Ca : P ratios reported for kikuyu. The concentrations of the other elements measured did not differ between the leaves and stems. Concentrations of CP, potassium, magnesium, copper and selenium in the kikuyu foggage decreased rapidly from the first collection that contained a relatively high proportion of green material to later collections when the foggage was dry. Keywords: Standing hay, Pennisetum clandestinum, leaf : stem ratio, calcium : phosphorus ratio, minerals South African Journal of Animal Science Vol. 38 (4) 2008: pp. 342-34