Thesis (M.S.)--University of Wisconsin--Madison, 1970. / Typescript eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 62-74)

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 101-118).

Thesis (doctoral)--Universiteit Utrecht, 2003. / Includes bibliographical references (158-171).

The pattern of post-partum and ovarian activity was monitored in two herds through the use of radioimmunoassay of progesterone in post-milking strippings. The University of British Columbia, South Campus (UBC) herd was sampled on a twice weekly basis, while the Agriculture Canada Research Station, Agassiz herd was sampled every second day. Sampling began approximately six days post-partum and continued up to 60 days post-conception. The estrous cycle was classified into phases based on the concentration of progesterone in the milk samples. Progesterone concentration immediately post-partum and for a varying length of time thereafter remained at basal levels. This was classified as Phase 0 and represented the stage of quiescence in the ovaries post-partum. Phase 1 of the estrous cycle represented the follicular stage when the concentration of progesterone was low. Phase 2 represented the stage when the corpus luteum was developing and the concentration of progesterone was rising. Phase 3, the fully active corpus luteum stage, was when the concentration was highest, while Phase 4 represented the regressing corpus luteum stage when the concentration was falling. The stage of quiescence, from parturition to the initiation of luteal activity was found to be 21.43 ± 11.84 days for 54 animals in the UBC herd and 19.81 ± 8.85 days for 127 animals in the Agassiz herd. Retained placenta increased the duration of quiescence to 25.62 ± 12.41 days for the 12.6% or 16 animals having the condition in the Agassizherd. The 9.3% or five animals having retained placenta in the UBC herd had a much shorter stage of quiescence of 10.80 ± 6.42 days. Two distinct types of first cycles were found, based on the mean concentration of progesterone and the number of days in the period. A normal first cycle exhibited more luteal activity during Phase 3, and remained in this Phase longer than did the shortened first cycle. This may be associated with follicle luteinization in the shortened first cycle rather than true ovulation as in the normal first cycle. The increased frequency of sampling of the Agassiz herd tended to give a more accurate classification of the phases of the cycle as defined, with more Phase 4 samples being identified. Also days in Phase 1 and Phase 2 for both Type 1 (shortened first cycle), and Type 2 (normal first cycle), were approximately half of those observed from the UBC herd. Standard curves of progesterone concentration vs. time for "normal" cycles of various lengths with standard deviations were derived from the pooling of all cycles classed as normal first cycles and normal cycles without a breeding. These "normal" cycles showed that as the cycle length increased, so did time spent during Phase 1 when the concentration of progesterone remained below 4 ng/ml milk. Progesterone profiles of various animals are included, illustrating the wide variety of profiles found. These include profiles of short stages of quiescence, long stages of quiescence, short cycles, long cycles as well as some abnormalities observed. When used as a test for early detection of pregnancy, a single sample from days 21 to 24 for the UBC herd showed accuracies of 100% in determining non-pregnancy and 86% in determining pregnancy. Test results for days 21 and 22 for the Agassiz herd were again 100% accurate for determining non-pregnancy and 90.5% accurate in determining pregnancy. The accuracy of the non-pregnant determination can be increased by including a sample on day of insemination and eliminating those animals inseminated at an obviously incorrect time. With the two sample test on the combined UBC data the accuracy of the pregnant diagnosis increased to 91.5%. On the combined Agassiz data the two sample test increased the accuracy of the pregnant diagnosis to 93.1%. The use of progesterone pregnancy testing offers a considerable saving in time in identifying those animals not conceiving to insemination and a reasonably accurate means of early detection of pregnancy. The average number of days from conception to positive palpation was 51.02 ± 13.19 days for 97 animals in the Agassiz herd and 60.43 ± 23.59 days for the 42 animals in the UBC herd. / Land and Food Systems, Faculty of / Graduate

Acetonemia is a metabolic disorder common among dairy cattle in the period from 10 days to six weeks post partum. It is during this time that milk production is at its maximum and in addition, the cow is beginning to exhibit regular estrous cycles. Thus, the profound demands for the precursors of milk production are superimposed upon a relatively unstable endocrine environment. The initial objective of this study was a clarification of the interactions between estrogens and endogenous substrates of glucose metabolism in the lactating cow. Since estrogen levels during the bovine estrous cycle had not been convincingly reported at the outset of this work, their measurement was the subject of the first experiment. Both estradiol and estrone exhibited peaks on the two days prior to the day of standing heat. These findings were later substantiated with the appearance of reports where plasma estrogen levels were measured by competitive protein binding and radioimmunoassay. A significant decline in plasma amino nitrogen concentration occurred after the estrogen peak, the decrease being reflected in marked reductions in the concentrations of threonine, methionine, proline and the branched chain amino acids. A notable hypoglycemia occurred somewhat later than the decline in amino acids. These findings were rationalized in terms of increased uterine and mammary uptake and/or decreased tissue mobilization of amino acids which may have given rise to the hypoglycemia as a result of decreased availability of glucogenic substrate. A possible mechanism of decreased tissue mobilization of amino acids was considered to be the inhibition by estrogens of adrenal glucocorticoid output, since glucocorticoids play a major role in regulating amino acid balance in peripheral tissues. In addition, the efficacy of glucocorticoid therapy in the treatment of bovine acetonemia is well recognized. With these considerations in mind, the role of estrogens in the modification of ACTH-stimulated glucocorticoid secretion was assessed in two further experiments. Following suppression of endogenous ACTH secretion by dexametha-sone, both estrogen treated and non-estrogen treated cows were subjected to stimulation with incremental doses of exogenous ACTH. At all levels of ACTH stimulation, estrogen treatment resulted in reduced response when measured in terms of plasma glucocorticoid concentrations. However, estrogen treatment had no effect on plasma binding of glucocorticoids. The concentrations measured were, therefore, a direct reflection of glucocorticoid activity. In the second experiment to test adrenal inhibition by estrogens, plasma ACTH and glucocorticoid levels were measured during the estrous cycles of lactating cows. For this purpose, a radioimmunoassay for ACTH was developed, providing a sensitive, reproducible method for the measurement of this hormone in bovine plasma. A significant increase in circulating ACTH concentration was seen during the estrogenic phase of the estrous cycle. No such increase was noted in the concentration of glucocorticoids, levels fluctuating within the normal, low range. This result implied that during the estrogenic phase of the estrous cycle, inhibition of glucocorticoid secretion by estrogens resulted in a compensatory rise in circulating ACTH concentration, bringing the glucocorticoid level back to normal. The results of these experiments are discussed with reference to the possible role of alterations in endocrine balance in the etiology of bovine acetonemia. / Land and Food Systems, Faculty of / Graduate

In conditions where supplementation of poor quality diets is a major challenge, forage legumes such as Sericea lespedeza can be a good alternative supplement for protein at lower cost than most commercial concentrates. From studies done on Sericea lespedeza it is found plausible and valuable to supplement urea with Sericea lespedeza to strategically combat the deleterious effect of condensed tannins in the Sericea lespedeza and provide nitrogen in the rumen. This study was aimed to evaluate the effect of replacing sunflower oilcake with urea (a rumen degradable protein RDP source) or Sericea lespedeza (rumen undegradable protein RUP source) mixed with urea as nitrogen/protein sources on nutrient utilization, milk yield and milk composition of Saanen dairy goats. A digestibility and lactation study were conducted at the University of Pretoria Research Farm and chemical analysis performed at the University Nutrilab. A 30 days digestibility study was conducted on male Saanen goats after the lactation study, with 23 days adaptation and 7 days data collection period. Nine male goats were randomised and allocated to the three treatments in metabolism cages. In the lactation study 36 dairy goats were blocked according to milk collected on first month of lactation into high, medium and low milk yielders, then allocated to the three treatments of total mixed rations containing sunflower oilcake (T1) at 7% main protein source, T2 (urea at 1%) and T3- Sericea lespedeza at 12.5% mixed with urea according to a complete randomised block design (CRBD). Milk samples were collected from individual goats monthly at two consecutive milking’s. The samples were analysed for milk fat, protein, lactose, somatic cell count and milk urea nitrogen using a Milko-Scan analyser (at Irene Lacto lab). In the digestibility study, dry matter intake was significantly higher for goats fed on Sericea lespedeza with urea (T3) diet than goats fed on T1 and T2 diet. Goats on T3 diet had also significantly higher organic matter and crude protein intake than those goats fed on the other two TMR diets. The results also shows that the mean daily milk yields for the goats in the T1, T2 and T3 were 2.56, 2.46 and 2.52 kg per day respectively. T2 group had higher milk fat % (3.61) and higher milk urea nitrogen (MUN - 25.70 mg N/dl) than the other two treatments. T1 had significantly higher milk protein %. There was a great difference in milk composition of the afternoon milk as compared to the morning milk. The three TMRs had no significant difference in the nitrogen utilization and nitrogen excretion. It is then concluded that Sericea lespedeza mixed with urea can be used as subsititutes for sunflower oilcake in the diets of dairy goats since no negetive effect was found. However further investigations are needed. / Dissertation (MSc Agric)--University of Pretoria, 2017. / DAAD-NRF / International Foundation for Science (IFS) / Animal and Wildlife Sciences / MSc (Agric) / Unrestricted

No description available.

1,032,438 Jersey and 1,162,578 Holstein official Dairy Herd Improvement Association (DHIA) records from 20,380 and 34,000 herd-years, respectively, were used to compute herd-year means and within herd-year standard deviations for individual mature equivalent (ME) milk, fat, and fat percent. These herd-year means and within standard deviations were used to stratify records into five classes. Regressions for individual daughter's modified contemporary deviation (MCD) on sire's predicted difference (PD) were calculated for each class. The within herd-year standard deviations were also used in some of the six different MCD calculations used to compute six different cow indexes (CI) for each cow and trait. The six MCDs calculated were either the current deviation, log adjusted deviation, or the deviation standardized to a constant variance in combination with either the current correction for contemporaries merit or an adjusted correction. The six different CI for each trait were compared by how accurately they predicted the son's MCD trait and the daughter's MCD trait. / Master of Science

No description available.

The effect of genetic selection for milk yield on lactation yield, net energy balance (NEB) and on plasma growth hormone (GH), insulin (INS), prolactin (PRL), nonesterified fatty acids (NEFA) and glucose was studied in primiparous Holstein cows. Net energy balance was calculated and serial blood samples were collected at 0, 45, 90, 180 d postpartum (dpp) and 14 d of the dry period over a 7 h period via jugular cannulae. After 2.5 h of blood collection, growth hormone releasing factor (GRF) was administered at 0, 45, 180 dpp and 14 day of the dry period, while epinephrine was administered at 90 dpp. Nonesterified fatty acids were quantified in 90 dpp samples only. Basal and response periods for each hormone and metabolite were compared by analysis of variance. Milk yield was greater (P<.05), NEB was decreased (P<.05) and plasma GH was greater (P<.05) in selection cows (high-yielders) compared to control cows (low-yielders), while PRL, INS, glucose and NEFA were not different. Growth hormone increased in both groups in response to GRF at all days postpartum measured, while PRL, INS and glucose were not altered. Epinephrine administration at 90 dpp, stimulated an increase in plasma NEFA, glucose and INS in both groups. Control cows showed a greater (P<.01) INS response than selection cows. Results indicate differences exist in GH concentration between genetically selected high- and low-yielding Holsteins during early lactation, but the question remains if these differences are due to energy balance differences or differences in genetic merit for milk yield. / Master of Science