In a Holstein herd (125 cows) the influence of early and late breeding post partum on reproduction and production was investigated. At calving the cows were randomly assigned to two groups. The early bred group was scheduled to be bred at the first visible heat following 50 days post partum which resulted in an average interval of 73 ± 18 days from parturition to the first service. The average interval from parturition to conception was 88 ± 33 days. The cows in the early bred group conceived after an average of 1.50 (range: 1 to 3) services per conception. The late bred group was scheduled to be bred at the first visible heat following 80 days post partum which resulted in an average interval of 93 ± 17 days from parturition to the first service. The average interval from parturition to conception was 120 ± 40 days. The cows in the late bred group conceived after an average of 1.96 (range: 1 to 5) services per conception. The number of services per conception was significantly (P£.05) higher for the late bred group. The early post partum reproductive activity was monitored with milk progesterone analyses. A sample of milk strippings was analysed by a radioimmunoassay technique every second day from 6 days post partum until conception occurred or the animal was removed from the herd. Cows which did not conceive were excluded from the statistical analyses. The average length of the first estrous cycle was 17 ± 7.5 days. The first progesterone detected heat occurred 33 ± 10 days post partum compared to the first visible heat which occurred 48 ± 26 days post partum. Calving associated problems and the calving during the pasture season delayed conception in the late bred group but not in the early bred group. The late bred group produced more fat corrected milk (FCM) in the 305 day lactation and in the first 150 days of the subsequent lactation and also gained more (P≤.05) weight between calvings. Cows calving during the pasture season produced more FCM in the 305 day lactation but gained significantly (P≤.01) less weight between calvings than cows calving in the non-pasture season. There was no difference between early and late bred group, health status groups or groups according to the calving season in terms of average daily milk and FCM yield calculated over the entire period of this experiment (beginning of current lactation to day 150 of the subsequent lactation, including the dry period). Calving difficulties and early post partum reproductive problems were not related to production traits. / Land and Food Systems, Faculty of / Graduate

A glutamina (Gln) e o glutamato (Glu) participam ativamente do metabolismo, sendo fontes de energia para células de intensa proliferação, como enterócitos, células do sistema imune, trofloblastos e embriões. O objetivo geral foi avaliar os efeitos da suplementação de Lglutamina e L-ácido glutâmico (1%) nas dietas: (a) marrãs desde a chegada ao local de experimentação até a manifestação do primeiro estro, seguido do primeiro ciclo estral e flushing (capítulo I), (b) primíparas no terço final da primeira gestação, seguida da lactação, intervalo desmame estro e terços inicial e médio até 73 dias da gestação subsequente (capítulo II); e nas dietas de leitões do desmame aos 49 dias de idade (capítulo III). No capítulo I, as fêmeas suplementadas durante o flushing, foram abatidas aos 5 dias de gestação para avaliação dos embriões e ovário. O número de corpos lúteos do grupo suplementado foi superior numericamente ao grupo controle (20,25 versus 17,88, respectivamente), sugerindo possível efeito da suplementação na taxa de ovulação, acompanhado do maior percentual de células vivas e menor de células mortas, com significância nas variâncias, indicativas de menor variabilidade e melhor homogeneidade das estruturas, levando a possível influência na viabilidade embrionária. No capítulo II, os pesos corporais e as espessuras de toucinho (ET) das primíparas não revelaram diferenças significativas nos períodos analisados. As concentrações de glutamina e glutamato no plasma sanguíneo foram significativas para o tratamento (p<0,05) até o parto, revelando concentrações maiores para as fêmeas suplementadas. Destacou-se diferença significativa na sobrevivência dos leitões no aleitamento em favor do grupo suplementado. Aos 73,45 ± 1,61 dias da segunda gestação, o peso dos fetos do grupo suplementado (p=0,0690) foi maior em relação aos do grupo controle. Os leitões desmamados (Capítulo III) foram avaliados em arranjo fatorial 2x2, sendo um fator a suplementação da mãe e outro a suplementação dos leitões. O peso ao desmame foi significativo para o fator Mãe, destacando maiores pesos para os leitões oriundos de mães controles (p=0,0296), contudo de 21 a 34 dias de idade, a conversão alimentar foi melhor para os leitões oriundos de mães suplementadas (p=0,0522). Ao final da terminação (133 dias de idade), os tratamentos não mostraram diferenças significativas em relação ao desempenho. Considerando que o peso dos leitões de mães controles iniciou superior ao desmame, os grupos se igualaram em relação ao peso final. Os resultados trazem novas perspectivas para futuras pesquisas em relação ao uso da suplementação de L-glutamina e L-ácido glutâmico, principalmente no flushing, nos terços inicial e médio da gestação, pois, pode influir positivamente na taxa de ovulação e desenvolvimento homogêneo e maior peso dos fetos. Além disso, a ação no desenvolvimento dos leitões, sobrevivência no aleitamento e quanto à integridade intestinal no período pós desmame também merecem atenção, o que pode contribuir, na abordagem interativa dos parâmetros, influência positiva na economia da produção. / Glutamine (Gln) and glutamate (Glu) actively participate in metabolism as energy sources for intense cells proliferation, such as enterocytes, immune cells, and embryos trophoblasts. The main objective was to evaluate the effects of L-glutamine and L-glutamic acid (1%) supplementation in the diets: (a) sows since arrival to the experimental place until the appearing of the first heat, followed by the first estrous cycle and flushing (chapter I), (b) gilts at the end of the first third of pregnancy, then lactation, weaning estrus interval and initial and middle thirds of up to 73 days of gestation subsequent (Chapter II); and in weaning diets of piglets at 49 days of age (Chapter III). In Chapter I, the females supplemented during the flushing were slaughtered at the 5th gestation day for embryos and ovary evaluation. The number of corpora lutea in the supplemented group was numerically higher than in the control group (20.25 vs. 17.88, respectively), suggesting a possible effect of supplementation on ovulation rate, accompanied by the highest percentage of live cells and smaller percentage of dead cells with significance on variances, which are indicative of lower variability and better structures homogeneity, leading to possible influence on embryo viability. In Chapter II, primiparous revealed no significant differences in the weights backfat thickness at the end of gestation, lactation and subsequent pregnancy. The glutamine and glutamate concentrations in blood plasma were significant for the treatment (p <0.05) until delivery, showing higher concentrations for supplemented females. Noteworthy the significant difference in the piglets survival during lactation in favor of the supplemented group. At 73.45 ± 1.61 days of the second pregnancy, the fetal weights in the supplemented group (p = 0.0690) was higher compared to the control groupy. Weaned piglets (Chapter III) were evaluated in a 2x2 factorial arrangement, with mother supplementation and piglets supplementation as factors. The weaning weight was significant for the control group, regardless of mothers supplementation (p = 0.0296), however, from 21 to 34 days of age, feed conversion was better for piglets from supplemented mothers (p = 0, 0522). By the end of termination (133 days of age), the treatments did not show significant differences, considering that the weight of controls piglets was heavier at weaning, the animals were equal with respect to final weight. The results open new perspectives for future research regarding the use of L-glutamine and L-glutamic acid supplementation, especially in flushing, in the early and middle thirds of pregnancy, since it can have a positively influence in ovulation rate, homogeneous development and greater fetues weight. Moreover, its effect on piglets development, both in the survival during lactation aspect, as to gut integrity in the post weaning period, also deserve attention, since the interactive approach can provide additives in the production economy.

MSCPNT / Department of Nutrition / Introduction: Iodine is an essential nutrient required by humans for the synthesis of thyroid hormones, which are vital for normal growth and development. Objective: The primary aim of the study was to describe the iodine status of lactating mothers and infants aged from 0 to 6 months in the Vhembe and Mopani Districts. Methods: A cross-sectional study conducted on 246 infant-mother pair, from the Mopani and the Vhembe Districts. Data was gathered using a questionnaire. Breastmilk, mother urine, infant urine, household salt and drinking water were collected to be analysed for iodine content. Results: The median of breastmilk iodine concentration level amongst lactating mothers in the Vhembe District was 101.4 µg/l (IQR 62.9 – 175.1 µg/l) and 154.4 µg/l (IQR 92.6 – 211.8 µg/L) in Mopani. The median UIC of mothers in Vhembe was 98.5 (IQR 57.66 – 153.93), whereas in the Mopani District the median UIC of mothers was 126.08 µg/l (IQR 69.89 – 206.71 µg/L). The median UIC of infants in Vhembe was 220 (IQR 106.67 – 418.43 µg/l) and in the Mopani District was 321.94 µg/l (IQR 167.96 – 482.66 µg/l). Conclusion: The BMIC in the study signifies iodine sufficiency in both the Vhembe and the Mopani Districts. The results of this study suggest that the BMIC be included in studies assessing iodine status in lactating mothers since the UIC only reflects iodine that was consumed recently. The UIC may under estimate the maternal iodine status if it is not complemented by the BMIC data. / NRF

The aim of this thesis was to evaluate changes in resting energy expenditure (REE) in ten lactating women between three weeks and nine months postpartum to find out whether there is any link with the parameters presented in this study. Measurements were taken at four intervals. At three weeks and at three, six and nine months postpartum. They were taken in the morning after a night fast (12 hours) and used indirect calorimetry with a canopy in awake lying subjects for approximately 25 minutes. The room was shaded with minimal noise with a temperature around 20 řC. Urine was collected over 24 hours and was examined for nitrogen concentration. The median REE was 1591,86 kcal/day at 3 weeks postpartum, 1398,08 kcal/day at 3 months, 1401,78 kcal/day at 6 months and 1455,03 kcal/day at 9 months postpartum. Values of REE per kilogram of body weight are 21,8 ± 0,36 kcal/kg and are consistent throughout the measurement period. The oxidation of lipids was dominant compared to other substrates and the lowest was oxidation of sacharides during the whole observation period. Correlations were found in parameters such as, body weight and REE per kilogram, breast milk and respiratory quotient (RQ), length of gravidity with RQ/ volume of exhaled carboxydioxide/ volume of inhaled oxygen. Another was between protein...

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Reports have linked energy balance along with adipocyte derived leptin action to improved fertility. Recent evidence indicates that leptin hormone is present in breast milk and leptin receptors are well expressed in mammary epithelial cells. The hypothesis that insufficiency of leptin restraint in the hypothalamus may underlie infertility in rodents and the failure of lactating breast to express adequate amount of milk was tested. Female Sprague-Dawley rats were injected leptin through intracerebroventricular cannulation (ICVC) of the third ventricle. Female rats were mated with stud males and observed throughout gestation. Compared to the control groups, leptin treatment increased prolactin levels in the dams and increased milk transfer to pup. Hypothalamic mRNA leptin levels and brain size in the offspring from leptin treated dams were significantly higher than the control. These findings support the involvement of leptin in reproduction and could lead to better understanding of leptin transfer from dam to offspring.

A computerized dairy herd simulation was developed to evaluate the economic impact of changing length of lactation relative to length of dry period in a dairy herd. It created weekly production for individual cows in a typical herd. Cows were dried off early if they were producing below a designated daily milk yield. They were replaced with fresh cows to produce more daily milk and increase profit while maintaining a constant number of cows in milk (98 to 102). A two by four factorial of dry off strategies was designed using rates of lactation decline of 6% and 8% and early dry off at 8, 13, 18, and 23 kg. Cows producing less than this for 2 wk consecutively were dried off. There were 100 cows in each herd and each of the eight scenarios was run 10 times (10 herds) for 80 herds total. Dry cow groups at 8, 13, 18, and 23 kg dry off were 14, 17, 23, and 32% of total herds, respectively. Average daily milk (kg) increased for the four dry kg: 30.4, 31.2, 32.3, and 33.7 kg/d per milking cow, whereas RHA decreased. Three different milk-feed income scenarios, (+20%, average, -20%) were combined with three dry cow costs, (+20%, average, and -20%). Nine combinations were analyzed statistically at each rate of decline. Net cash income changed $3561, $1571, and $-3051 from 8 to 13 to 18 to 23 kg dry kg under a normal economic situation. Net farm income under the same scenario changed $3170, $2945, and $-1154. Under the best economic situation, net cash income increased with each successive dry kg, $5086, $4248, and $921. Net farm income also increased by $4695, $5621, and $2819. Net cash income and net farm income were largest at 13 and 18 kg when milk-feed income was low and dry cow cost was high, the worst economy scenario. Only in the most optimistic economic situations does it appear practical for a dairy business to adopt early dry off beyond 13 kg/d per cow given the small gains and the yearly variability. Strategies of dry off at larger dry kg, although not greatly profitable, nevertheless were not extremely unprofitable either. / Master of Science