The thesis deals with analysis the influence to effectiveness of Holstein cows bred on the School farm in Haklovy Dvory. I studied the most frequent reasons of culling cows on the farm and the influence on the cost accounts.

The point of the work was to make an analysis of milk production an and fertility and to attest dependence of milk production and fertility in the holstein cattle herd. Background materials were acquired especially from milk production control and cattle accompanying documents. Data of 251 dairy cows were worked up. Big problem of the high producing dairy cows is the low fertility. That is why the work was focused on analysing of milk production and fertility index. Service period, insemination interval and interval were analysed out of the fertility index. Milk production, proteins and fats percentage content represent the efficiency. The results show the high selection of cows out of the herd. It result shows from a number of included heifers. Most frequent reasons of selection are health condition, low milk efficiency and fertility disorders. Average efficiency in control increases. On the other hand the protein contest in milk is weak. A breading aim 3,3% was achieved only in year 2003 (3,32%). Milk production increases from the first to the third lactation. Milk production is decreasing from the fourth lactation. Fat percentage content increases to the third lactation, then it stagnates. The protein content goes down with number of lactation. Required interval length to 400 days is exceed in all lactation. Service period is to high regardless of lactation number. Insemination interval increases to the third lactation, then it decreases, but it is nonconforming all the time. The results show that fat and protein content decreases with milk production. The high milk production was reached on cows calved in autumn (8920,77 kg) and in winter (9231,48 kg). Data of cows calved in spring and in summer are almost the same. The results evidence general rule, that fertility decreases with increasing milk production.

The influence of the nutritive plane on the early growth of the Holstein calf has been investigated. Particular attention has been given to near-maximal growth rates, and to the ability of calves to exhibit compensatory growth after nutrient restriction is removed. A whole milk feeding standard, intended to allow maximum consumption, was established and used as the plane of nutrition for a group of high-plane calves. A second group of calves was fed milk at a lower plane for a period, before being realimentated to the same high plane that their contemporaries had received. Metabolic rate measurements were made on all calves at regular intervals. The animals of both groups were slaughtered at a body weight of 113 kgm (250 lb) and various measurements were taken from the dissected carcasses. The high-plane feeding standard proved to be quite satisfactory and permitted weight gains from 1.09 to 1.34 kgm/ day for the calves reared continuously on this plane. Highly reproducible rates of gain were displayed by the low-plane calves, both during the periods of restriction and realimentation. The growth rates of the low-plane calves in the latter period exceeded those of the high-plane animals, being from 1.45 to 1.6l kgm/day. The possible reasons for this increased growth capability are discussed in relation to the studies of other workers on compensatory growth. Nutrient restriction depressed the metabolic rates of low-plane calves below those exhibited by their high-plane partners of equal weight. Upon realimentation, the metabolic rates of the previously-restricted calves rose quite rapidly to levels commensurate with the heat losses of the high-plane animals. The carcass dissection studies did not reveal extensive modifications in body composition that could be attributed to the treatments. The growth of certain visceral organs was retarded or accelerated by the nutritive planes imposed, but the musculature and skeleton were apparently unaffected by the pattern of growth. The yield of edible meat was essentially the same for both groups of animals, despite a lower consumption of milk by the calves whose growth had been interrupted. A model, for comparison of the relative efficiencies of restricted and unrestricted meat-producing animals, is suggested. / Land and Food Systems, Faculty of / Graduate

Experiment 1 A survey on the β-Carotene status of Holstein cows in different feeding systems In order to make meaningful recommendations with regard to β-Carotene supplementation is it necessary to know whether cows are deficient in β-Carotene. The objective of this study was to generate data on the β-Carotene status of Holstein cows under three different feeding systems in South Africa, namely; pasture-based, silage-based and hay-based feeding systems. A survey was conducted amongst 30 farms with 10 farms utilizing each of the three systems. Twenty multiparous cows were randomly selected from each farm. Blood samples were taken from the tail vein and analysed for plasma β-Carotene using the iCheck™, a hand held spectrophotometer (BioAnalyt, GmbH, Germany). Cows were then classified as deficient (< 1.5 mg/L), marginal (1.5 to 3.5 mg/L) or optimal (>3.5 mg/L). The average plasma β-Carotene levels differed between feeding systems and concentrations were 5.53, 2.98 and 1.71 mg/L for the pasture based, hay-based and silage-based feeding systems respectively. There was a wide variation in average plasma β-Carotene concentrations in cows on farms within the different feeding systems. Average values per farm ranged between 3.84 and 10.81 mg/L for the pasture based farms, 0.91 and 5.00 mg/L for the hay-based farms and between 0.78 and 3.38 mg/L for the silage-based farms. Results suggest cows on a pasture based feeding system have optimal β-Carotene status and do not need supplementation. Cows on hay-based systems are marginal and on farm testing is recommended. Cows on silage-based systems are generally deficient and β-Carotene supplementation is recommended. Experiment 2 Effect of prepartum β-Carotene supplementation on the postpartum β-Carotene status of Holstein cows. It has been recommended that cows be supplemented β-Carotene when blood plasma levels are deficient (< 1.5 mg/L) or marginal (< 3.5 mg/L) especially during the transition period which is characterised by low intakes and significant losses of β-Carotene through colostrum. The objective of this trial was to determine to what extent prepartum β-Carotene supplementation could maintain postpartum plasma β-Carotene concentrations above 3.5 mg/L in cows fed a lucerne hay-based TMR. Twenty multiparous Holstein cows were blocked into two groups of ten cows each and were fed either 8kg/d of a control TMR (DM) or the control diet supplemented with 1200mg of ROVIMIX® β-Carotene 10%. The experimental period was from 60d pre-partum until 56d postpartum; however the period of the β-Carotene supplementation for the one group was only from 60d prepartum until calving. Blood samples were collected from the tail vein once per week and analysed for plasma β-Carotene using the iCheck™, a handheld spectrophotometer (BioAnalyt, GmbH, Germany). Average plasma β-Carotene concentrations prepartum were higher (6.15 mg/L) (P < 0.05) for supplemented cows compared to the control cows (3.10 mg/L). For the first 5 weeks postpartum, plasma β-Carotene was higher (P < 0.05) for supplemented cows compared to control cows (3.00 mg/L vs. 1.39 mg/L), from weeks 6 to 9 there were no differences (P > 0.05). Overall the average postpartum plasma β-Carotene values were 1.50 mg/L for the control cows and 2.43 mg/L for the supplemented cows and did not differ. Supplemented cows maintained sufficient β-Carotene concentrations only for the first 2 weeks postpartum and were either marginal or deficient for the rest of the experimental period. Results suggest a minor carryover effect of β-Carotene after prepartum supplementation. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Animal and Wildlife Sciences / unrestricted

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Production of dairy cows is influenced by many factors, among which are: genetics, nutrition, management, disease and age. Most of these factors can be modified to maintain a high level of production. Age, however, is beyond the influence of mankind; therefore, it is important to understand the effect of age on milk and butter-fat production.

Six nonlactating Holstein cows fitted with rumen and duodenal cannula were used to determine the efficacy of pH sensitive fatty acid polymer encapsulation as a means protecting amino acids from rumen fermentation and as a post-ruminal amino acid delivery system. The cows were arranged in a 2 x 2 factorial in a latin square design. Treatments were 1) the basal ration, and 2) basal ration plus rumen-protected lysine, methionine, and threonine at 10 g each per day. Rumen parameters measured were pH, ammonia, volatile fatty acids, protozoa, liquid, and dry matter rate of passage, total viable bacteria, and viable cellulolytic bacteria. Duodenal parameters measured were crude protein, ammonia, and amino acid concentrations. Total tract apparent digestibility of nutrients was measured. In addition, rumen degradation of the three amino acid products was measured by loss from nylon bags, in the rumen. Loss of product from nylon bags suggested the lysine and threonine products had no significant rumen protection, but that the methionine product had > 50% protection at 12 h in the rumen. None of the rumen parameters measured differed (P>.05) due to treatment. Duodenal crude protein and ammonia concentrations did not differ due to treatment. Duodenal amino acid concentrations were numerically higher for the amino acid supplemented treatment, but the differences were nonsignificant and thought to be confounded by failure of the lysine and threonine products. Total tract apparent nutrient digestibility was not affected by treatment. A second experiment was conducted using 40 post-parturient Holstein cows, and different rumen-protected amino acid products from the first trial. Cows were nesteMwby treatment (control vs rumen-protected methionine 46 g and lysine 22 g) and parity (primiparous vs multiparous). Dry matter intake and milk production were monitored daily, body weight weekly, and milk composition bi-weekly. Total tract apparent nutrient digestibility was measured during the last week of the 10-week trial. There was no significant (P<.05) effect of supplemental rumen-protected lysine and methionine among primiparous animals. Multiparous animals receiving supplemental amino acids had lower dry matter intakes and yield of milk components than control animals.

Ghrelin is a hormone produced mainly by the cells lining the gastric mucosa. Ghrelin was first extracted from human and rat stomachs, and identified as an endogenous stimulator of growth hormone release. Ghrelin is synthesized and produced in several tissues, but the gastric mucosa remains the major source of circulating ghrelin. Besides growth hormone release, ghrelin stimulates appetite and plays some major roles in different organs. In several studies, ghrelin was described as a hormone with multiple functions and diverse biological actions. Ghrelin exists in two major forms, active ghrelin and inactive ghrelin, and only the active from binds to the receptor. The majority of total circulating ghrelin is inactive ghrelin with no identified function. The aims of the present study were to measure active and total ghrelin in dairy cow’s milk and plasma during early lactation, and to observe changes in the ghrelin concentrations over time. We are interested in this period of time since the milk during early lactation contains a variety of biologically active hormones that are vital for newborn calves. In this study, fifteen Holstein dairy cows were selected randomly from different lactations. Milk and blood samples were taken daily from cows at early lactation for 10 days, and from some cows in mid-lactation. A laboratory test was used to measure active and total ghrelin in milk and plasma samples. Supplementary measurements such as milk fat, lactose, protein, and milk yield were recorded. Active and total milk ghrelin concentrations were found to be significantly higher in the first day of lactation during colostrum production. Interestingly, the percentage of active to total ghrelin in milk and blood was constant in all days tested, suggesting that this constant percentage can be used to estimate active or total ghrelin, if one of them is know, from the same sample. However, no correlation was observed between the percentage of milk ghrelin and plasma ghrelin or with other milk components. In conclusion, the presence of ghrelin in colostrum and milk in measurable amounts of both active and total form suggests that it is a critical compound for the metabolic activity of newborn calves and functions transiently to regulate the activity of some physiological processes until the endocrine system of the new calves starts to function independently.

Objective 1 was to investigate effects of heat stress and breed on milk and component yield for Holstein and Jersey cows on the same farm. Objective 2 was to determine the effects of breed on udder health as measured by somatic cell count (SCC) during times of heat stress. Data were collected from DHIA records of 142 Jersey cows and 586 Holstein cows from the University herd at Mississippi State University. During heat stress Jersey milk yield and 4% fat corrected milk (FCM) increased (P<0.01). Holstein milk yield and FCM decreased during heat stress (P<0.01). Heat stress affected somatic cell count (SCC) although effects varied by intensity of heat stress. Breed did not have an affect on SCC. Milk fat and protein percentages declined for both breeds in heat stress conditions. Milk fat but not milk protein of Jersey cows increased as stress increased from mild to severe.

No description available.