Typescript (lithograph copy). Thesis (M.S.)--Oklahoma State University, 2000. Vita. Includes bibl... more Typescript (lithograph copy). Thesis (M.S.)--Oklahoma State University, 2000. Vita. Includes bibliographical references.
The objective of this study was to compare the growth performance of two Nguni ecotypes and its c... more The objective of this study was to compare the growth performance of two Nguni ecotypes and its crosses (Nguni x Landim) raised under the same feedlot conditions at the Posto Fomento do Impaputo, in southern Mozambique. Live weight feedlot data, from entry to marketing, were collected every fortnight between 1999 and 2009 from 453 oxen of the Nguni and Landim male ecotypes, as well as the crosses . Year-season of birth had significant effects on live weight at entry in the feedlot and at marketing age. Overall means for average age at entry in the feedlot was 31.8 ± 4 months, with the Landim being younger than the Cross (p=0.07). The average live weight at entry in the feedlot was 390 ± 42.5 kg, with no differences between ecotypes (p>0.05). Males born in dry year-seasons were heavier than males born in wet years-seasons (p<0.0001 to p<0.05).The average age at marketing of the Nguni ecotypes was 34.4 ± 5.08 months, with the Landim being younger (p<0.05) than the Cross. T...
Multiparous nonlactating Holstein cows were used to determine the effect of dexamethasone on ovar... more Multiparous nonlactating Holstein cows were used to determine the effect of dexamethasone on ovarian follicular development and plasma hormone concentrations. Animals were randomly divided into two groups, control (C; n = 5) and treatment (T; n = 6), but managed as one group. Both groups were synchronized with two injections of PGF2alpha (25 mg i.m.) 11 d apart. One day after ovulation (d 0) the T group received a daily injection of dexamethasone (44 microg/kg of body weight; i.m.) until the first dominant follicle stopped growing or up to d 12 postovulation. The C group received vehicle injections. Blood samples were collected daily from all cows. Concentrations of LH and FSH did not differ between the C and T cows, whereas progesterone concentrations were lower in T than in C cows from d 4 onward. Treatment x day interaction influenced plasma insulin concentrations such that T cows had insulin concentrations 2.9- to 6.0-fold those of C cows between d 2 and 9. Dexamethasone decreas...
ABSTRACT In a Nguni-herd of 40 cows managed under extensive range conditions on an experimental f... more ABSTRACT In a Nguni-herd of 40 cows managed under extensive range conditions on an experimental farm in Southern Mozambique oestrus duration and ovulation time was studied by intensive oestrus observation and transrectal sonography of the ovaries. In 30 oestrus cycles an average durantion of standing oestrus of 25.4 h, an average interval between end of oestrus and ovulation of 12h was detected. The mean interval between AI and ovulation was of 23.7h for single inseminated cows and of 11.3 h for cows inseminated twice. The four month-pregnancy rate was 62.6%. The data indicate that the Nguni-cattle show an oestrus behaviour that is more similar to that of European cattle than to that of Zebu cattle. To obtain reliable fertility results after AI it is recommended to perform a first insemination 12h after detection of standing oestrus and repeat this insemination if the cow still presents oestrus symptoms the next day.
To determine the effect of gonadotropins on insulin- and insulin-like growth factor (IGF-I)-induc... more To determine the effect of gonadotropins on insulin- and insulin-like growth factor (IGF-I)-induced bovine granulosa cell functions, granulosa cells from bovine ovarian follicles were cultured for 2 days in the presence of 10% fetal calf serum (FCS), and then cultured for an additional 2 days in serum-free medium with added hormones. In the presence of 0 or 1 ng/mL of insulin or IGF-I, FSH had little or no effect (P &amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05) on estradiol production by granulosa cells from both small (1-5mm) and large (&amp;amp;amp;amp;amp;amp;amp;amp;gt; or = 8mm) follicles. However, in the presence of &amp;amp;amp;amp;amp;amp;amp;amp;gt; or = 3 ng/mL of insulin, FSH increased (P &amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) estradiol production by granulosa cells from small and large follicles such that the estimated dose (ED(50)) of insulin necessary to stimulate 50% of the maximum estradiol production was decreased by 2- to 3-fold from 22 to 28 ng/mL in the absence of FSH to 7-14 ng/mL in the presence of FSH. Similarly, in the presence of &amp;amp;amp;amp;amp;amp;amp;amp;gt; or = 3 ng/mL of IGF-I, FSH increased (P&amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) estradiol production by granulosa cells from small and large follicles such that the ED(50) of IGF-I for estradiol production was decreased by 4- to 5-fold from 25 to 36 ng/mL in the absence of FSH to 5-6 ng/mL in the presence of FSH. In the presence of FSH, the maximal effect of insulin on estradiol production was much greater than that of IGF-I (137- versus 12-fold increase) and were not additive; when combined, 100 ng/mL of IGF-I completely blocked the stimulatory effect of 100 ng/mL of insulin. In the absence of FSH, the maximal effect of insulin and IGF-I on estradiol production was similar. Concomitant treatment with 30 ng/mL of LH reduced (P&amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05) insulin-stimulated estradiol production by 52% on day 1 and 19% on day 2 of treatment. Insulin, IGF-I and FSH also increased (P&amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05) granulosa cell numbers and progesterone production but their maximal effects were less (i.e., &amp;amp;amp;amp;amp;amp;amp;amp;lt; 4-fold increase) than their effects on estradiol production. In conclusion, insulin and IGF-I synergize with FSH to directly regulate ovarian follicular function in cattle, particularly granulosa cell aromatase activity.
The objective of this study was to assess the reproductive performance of two Nguni ecotypes (Ngu... more The objective of this study was to assess the reproductive performance of two Nguni ecotypes (Nguni and Landim) raised in a subtropical environment to enhance strategies for livestock development and restocking programmes within the southern African region. Reproduction data collected between 1996 and 2009 from 365 cows of the Landim and Nguni ecotypes were analysed. From the results, ecotype, place of birth, year and season of birth/calving had significant effects on age at first calving (AFC) and calving interval (CI). Overall means for AFC and CI were 1,071 ± 166 days and 432 ± 85 days, respectively, while average calving rate was 88.0 ± 4.7%. Heifers born in the dry season had lower AFC than heifers born in the wet season. Heifers born at Impaputo Breeding Center were the youngest at first calving, followed by the South African born ones. Heifers of the Landim ecotype also calved younger than heifers of the Nguni ecotype. CI was shorter in wet seasons (main breeding seasons) tha...
Typescript (lithograph copy). Thesis (M.S.)--Oklahoma State University, 2000. Vita. Includes bibl... more Typescript (lithograph copy). Thesis (M.S.)--Oklahoma State University, 2000. Vita. Includes bibliographical references.
The objective of this study was to compare the growth performance of two Nguni ecotypes and its c... more The objective of this study was to compare the growth performance of two Nguni ecotypes and its crosses (Nguni x Landim) raised under the same feedlot conditions at the Posto Fomento do Impaputo, in southern Mozambique. Live weight feedlot data, from entry to marketing, were collected every fortnight between 1999 and 2009 from 453 oxen of the Nguni and Landim male ecotypes, as well as the crosses . Year-season of birth had significant effects on live weight at entry in the feedlot and at marketing age. Overall means for average age at entry in the feedlot was 31.8 ± 4 months, with the Landim being younger than the Cross (p=0.07). The average live weight at entry in the feedlot was 390 ± 42.5 kg, with no differences between ecotypes (p>0.05). Males born in dry year-seasons were heavier than males born in wet years-seasons (p<0.0001 to p<0.05).The average age at marketing of the Nguni ecotypes was 34.4 ± 5.08 months, with the Landim being younger (p<0.05) than the Cross. T...
Multiparous nonlactating Holstein cows were used to determine the effect of dexamethasone on ovar... more Multiparous nonlactating Holstein cows were used to determine the effect of dexamethasone on ovarian follicular development and plasma hormone concentrations. Animals were randomly divided into two groups, control (C; n = 5) and treatment (T; n = 6), but managed as one group. Both groups were synchronized with two injections of PGF2alpha (25 mg i.m.) 11 d apart. One day after ovulation (d 0) the T group received a daily injection of dexamethasone (44 microg/kg of body weight; i.m.) until the first dominant follicle stopped growing or up to d 12 postovulation. The C group received vehicle injections. Blood samples were collected daily from all cows. Concentrations of LH and FSH did not differ between the C and T cows, whereas progesterone concentrations were lower in T than in C cows from d 4 onward. Treatment x day interaction influenced plasma insulin concentrations such that T cows had insulin concentrations 2.9- to 6.0-fold those of C cows between d 2 and 9. Dexamethasone decreas...
ABSTRACT In a Nguni-herd of 40 cows managed under extensive range conditions on an experimental f... more ABSTRACT In a Nguni-herd of 40 cows managed under extensive range conditions on an experimental farm in Southern Mozambique oestrus duration and ovulation time was studied by intensive oestrus observation and transrectal sonography of the ovaries. In 30 oestrus cycles an average durantion of standing oestrus of 25.4 h, an average interval between end of oestrus and ovulation of 12h was detected. The mean interval between AI and ovulation was of 23.7h for single inseminated cows and of 11.3 h for cows inseminated twice. The four month-pregnancy rate was 62.6%. The data indicate that the Nguni-cattle show an oestrus behaviour that is more similar to that of European cattle than to that of Zebu cattle. To obtain reliable fertility results after AI it is recommended to perform a first insemination 12h after detection of standing oestrus and repeat this insemination if the cow still presents oestrus symptoms the next day.
To determine the effect of gonadotropins on insulin- and insulin-like growth factor (IGF-I)-induc... more To determine the effect of gonadotropins on insulin- and insulin-like growth factor (IGF-I)-induced bovine granulosa cell functions, granulosa cells from bovine ovarian follicles were cultured for 2 days in the presence of 10% fetal calf serum (FCS), and then cultured for an additional 2 days in serum-free medium with added hormones. In the presence of 0 or 1 ng/mL of insulin or IGF-I, FSH had little or no effect (P &amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05) on estradiol production by granulosa cells from both small (1-5mm) and large (&amp;amp;amp;amp;amp;amp;amp;amp;gt; or = 8mm) follicles. However, in the presence of &amp;amp;amp;amp;amp;amp;amp;amp;gt; or = 3 ng/mL of insulin, FSH increased (P &amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) estradiol production by granulosa cells from small and large follicles such that the estimated dose (ED(50)) of insulin necessary to stimulate 50% of the maximum estradiol production was decreased by 2- to 3-fold from 22 to 28 ng/mL in the absence of FSH to 7-14 ng/mL in the presence of FSH. Similarly, in the presence of &amp;amp;amp;amp;amp;amp;amp;amp;gt; or = 3 ng/mL of IGF-I, FSH increased (P&amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) estradiol production by granulosa cells from small and large follicles such that the ED(50) of IGF-I for estradiol production was decreased by 4- to 5-fold from 25 to 36 ng/mL in the absence of FSH to 5-6 ng/mL in the presence of FSH. In the presence of FSH, the maximal effect of insulin on estradiol production was much greater than that of IGF-I (137- versus 12-fold increase) and were not additive; when combined, 100 ng/mL of IGF-I completely blocked the stimulatory effect of 100 ng/mL of insulin. In the absence of FSH, the maximal effect of insulin and IGF-I on estradiol production was similar. Concomitant treatment with 30 ng/mL of LH reduced (P&amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05) insulin-stimulated estradiol production by 52% on day 1 and 19% on day 2 of treatment. Insulin, IGF-I and FSH also increased (P&amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05) granulosa cell numbers and progesterone production but their maximal effects were less (i.e., &amp;amp;amp;amp;amp;amp;amp;amp;lt; 4-fold increase) than their effects on estradiol production. In conclusion, insulin and IGF-I synergize with FSH to directly regulate ovarian follicular function in cattle, particularly granulosa cell aromatase activity.
The objective of this study was to assess the reproductive performance of two Nguni ecotypes (Ngu... more The objective of this study was to assess the reproductive performance of two Nguni ecotypes (Nguni and Landim) raised in a subtropical environment to enhance strategies for livestock development and restocking programmes within the southern African region. Reproduction data collected between 1996 and 2009 from 365 cows of the Landim and Nguni ecotypes were analysed. From the results, ecotype, place of birth, year and season of birth/calving had significant effects on age at first calving (AFC) and calving interval (CI). Overall means for AFC and CI were 1,071 ± 166 days and 432 ± 85 days, respectively, while average calving rate was 88.0 ± 4.7%. Heifers born in the dry season had lower AFC than heifers born in the wet season. Heifers born at Impaputo Breeding Center were the youngest at first calving, followed by the South African born ones. Heifers of the Landim ecotype also calved younger than heifers of the Nguni ecotype. CI was shorter in wet seasons (main breeding seasons) tha...
Uploads
Papers by Sonia Maciel