Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Sixty Bonsmara heifers (328 ± 3.9 kg) on planted pastures were used to evaluate the effect of two energy sources and three growth promoters on body weight gain. Two supplementary feeds with dried apple pulp (A) or maize (M) as main energy source were formulated on an iso-nutrient base. One of three different growth promoters was included in each energy supplement: placebo (no growth promoter, designated as Treatments Ap and Mp), ionofore (monensin, designated as Treatments Am and Mm) and essential oil extract (from oregano, designated as Treatments Ao and Mo). A fixed amount of the supplements was offered to the six treatment groups in a growth/finishing study on cultivated grass-legume pastures. Animals were stratified according to initial weight in ten blocks and treatments were assigned randomly to animals in each block. The 66 day growth study was conducted during spring (Sepember to November, 2014) in the Western Cape Province of South Africa near Greyton. The cultivated pastures consisted of a perennial grass-legume mixture. A rotation grazing system was applied and animals were moved to new paddocks once a week. Based on falling plate meter readings, the heifers consumed a calculated mean amount of 4.48 ± 0.08 (SEM) kg DM/day over the entire experimental period. A fixed amount of 4 kg (“as is” basis) of the respective supplements were offered daily during the first 42 days, followed by 5 kg/day from 43 days until the end of the study (66 days). Animals were weighed bi-weekly and average daily gain (ADG) was calculated. The mean ADG of the six treatment groups was 1.44 kg/day. No interactions occurred between the energy sources and growth promoters used in the concentrates and main effects were thus interpreted. The supplements that contained apple pulp as energy source resulted in a higher (P < 0.02) ADG (1.54 kg/day) than the maize containing supplements (1.33 kg/day). There were no differences between any of the growth promoters, with the placebo resulting in similar growth rates than monensin and oregano oil extract. Mean ADG values (kg/day) of the different growth promoter treatments were 1.44 (placebo), 1.49 (monensin) and 1.38 (oregano). All the heifers were slaughtered at the end of the trial. Carcass weight and dressing percentage did not differ between energy sources or growth promoters. The mean dressing percentage was 52.5%. The mean income over feeding cost for the 66 day period of the three maize energy source treatments was R254.20/heifer, while that of the apple pulp treatments was R524.75/heifer. According to this study, concentrate supplements containing apple pulp as main energy source were economically more desirable than those containing maize as primary energy source. / AFRIKAANSE OPSOMMING: Sestig Bonsmaraverse (328 ± 3.9 kg) op aangeplante weiding is gebruik om die invloed van twee energiebronne en drie groeibevorderaars op massatoename te ondersoek. Twee supplemente met gedroogde appelpulp (A) of mielies (M) as hoofenergiebron is op ‘n isonutriëntbasis geformuleer. Een van drie groeibevorderaars is in elk van die energiesupplemente ingesluit: placebo (geen groeibevorderaar, aangedui as Behandelings Ap en Mp), ‘n ionofoor (monensin, aangedui as Behandelings Am en Mm) en ‘n essensiële olie-ekstrak (van oreganum, aangedui as Behandelings Ao en Mo). ‘n Vasgestelde hoeveelheid van die supplemente is aan elk van die ses groepe in ‘n groei/afrondingsproef op aangeplante weidings aangebied. Diere is volgens aanvangsmassa in tien bloke gestratifiseer en behandelings is ewekansig aan diere in elke blok toegeken. Die 66-dae groeistudie is gedurende die lente (September tot November) in die Wes-Kaapprovinsie van Suid-Afrika naby Greyton uitgevoer. Die weidings het uit ‘n meerjarige gras-klawermengsel bestaan. ‘n Rotasiebeweidingstelsel is gevolg en diere is weekliks na nuwe kampies verskuif. Volgens die lesings van ‘n valplaatmeter het die verse ‘n gemiddelde weidingsinname van 4.48 ± 0.08 (SEM) kg DM/dag getoon. ‘n Vasgestelde hoeveelheid van 4 kg (lugdroë basis) van die onderskeie supplemente is daagliks gedurende die eerste 42 dae van die proef aangebied, gevolg deur 5 kg/dag vanaf 43 dae tot aan die einde van die proef (66 dae). Diere is tweeweekliks geweeg en die gemiddelde daaglikse toename is (GDT) bereken. Die gemiddelde GDT van die ses behandelingsgroepe was 1.44 kg/dag. Geen interaksies tussen die energiebronne en groeibevorderaars is waargeneem nie en hoofeffekte is gevolglik geïnterpreteer. Die supplemente wat appelpulp as energiebron bevat het, het tot ‘n hoër (P < 0.02) GDT (1.54 kg/day) gelei as die mieliebevattende supplemente (1.33 kg/dag). Daar was geen verskille tussen enige van die groeibevorderaars nie met die placebo wat soortgelyke resultate as monensin en oreganum olie-ekstrak gelewer het. Gemiddelde GDT waardes (kg/dag) van die onderskeie groeibevorderaars was 1.44 (placebo), 1.49 (monensin) en 1.38 (oreganum). Al die verse is teen die einde van die proef geslag. Karkasmassa en uitslagpersentasie het nie tussen energiebronne of groeibevorderaars verskil nie. Die gemiddelde uitslagpersentasie was 52.5%. Die gemiddelde wins bo voerkoste van die drie energiebronsupplemente was R254.20/vers, terwyl dié van appelpulpbehandelings R524.75/vers was. Volgens hierdie studie was die supplemente wat appelpulp as hoofenergiebron bevat het, meer winsgewend as dié wat mielies as hoofenergiebron bevat het.

Dairy heifers were submitted to high or moderate plane of nutrition before and during first gestation. High plane of nutrition did not increase milk production but negatively affected reproduction and health. In addition, high plane of nutrition decreased growth hormone (GH) concentration and increased prolactin concentration during gestation. There was no effect of previous plane of nutrition on peripartum concentrations of hormones. Milk production was positively correlated with GH concentrations, but was negatively correlated to concentrations of insulin-like growth factor-1(IGF-1) concentrations postpartum. / The effect of GH administration on mammary vasculature and on paracrine secretion of growth factors was investigated in lactating and non-lactating dairy cows. The injection of GH induced a linear increase of IGF-1 concentration in blood and mammary primary lymph, but did not affect concentrations of prostaglandin E$ sb2$ (PGE$ sb2$) concentrations. However, the rate of IGF-1 increase was slower in lymph than in blood, suggesting that blood is the source of most lymph IGF-I. Therefore, GH did not seem to affect paracrine secretion of IGF-1 and PGE$ sb2$ by the bovine mammary gland. Growth hormone administration induced a gradual increase in mammary blood flow in lactating cows while it remained constant in non-lactating animals. Changes in lymphatic, but not blood, concentrations of a stable metabolite of the vasodilatator prostacyclin I$ sb2$ parallelled the changes in blood flow. This indicates that local secretion of this vasodilatator may be responsible for the effect of GH on mammary blood flow. / Mitogenic activity of mammary primary lymph samples taken at different physiological stages was evaluated on mammary epithelial and mammary fibroblast cell lines. The results indicate that the mitogenic activity of lymph in epithelial cells was not related to physiological stage but to PGE$ sb2$ concentration. In fibroblasts, mitogenic activity of lymph was not related to physiological stage or to the content in any of the growth factors assayed.

No description available.

The aim of this study was to evaluate the effects of M. elsdenii (Me) dosing on dairy heifer performance. A secondary set of data (feed intake, heifers birth weights, age and Weight at insemination, and first lactation milk performance) of heifers (dosed and not dosed with Me) was obtained from the dairy herd of the Agricultural Research Council – Animal Production. Data were arranged in a complete randomised design and analysed as repeated measures. Milk, pre-weaning starter and metabolised energy intake did not differ between the control and the Me groups. Post-weaning starter feed intake was higher (p=0.03) for Me fed heifers than control heifers. The post-weaning metabolisable energy intake was also higher (p=0.03) for heifer fed Me than control heifers. The average daily weight gain of heifers dosed with Me was higher during the pre-weaning period (0.66 kg/day; p=0.04) and after weaning (1.12 kg/day; p=0.03) compared to control (0.60 and 0.65 kg/day, respectively). At 42 and 70 days old, the BW of Me-heifers was greater (75.8 ± 2.6 and 91.2 ± 4.6 kg) than control heifers (61.9 ± 2.6 and 77.2 ± 4.6 kg) (p<0.05). There was no difference (P>0.05) in BW at insemination, number of insemination and milk yield between the two groups of cows (p>0.05). Early feeding of Me to heifers in the present study positively affect heifer growth during and early after milk feeding period, confirming previous report. Animal weight at puberty and the subsequent milk production were not influenced by feeding Me. It is possible that Me did not survive long after weaning to continue to express its influence on animal performance. / Agriculture and  Animal Health / M. Sc. (Agriculture)