In experiment 1, fourteen cows were blocked for milk yields and balanced for days in lactation. Treatments were: (1) Air conditioning (AC), five cows; (2) Evaporative cooling (EC), four cows; and (3) Conventional shade (S), five cows. Sequential samples were taken for 8 h at 12 min intervals starting at 2200 and then at hourly intervals for 13 h. Serum was assayed for insulin, thyroxine (T4), triiodothyronine (T3) and cortisol using a double-antibody radioimmunoassay procedure. Free fatty acids (FFA) were determined in serum by an enzymatic method. In experiment 2, ten cows were blocked for milk yields and days in lactation. Treatments were: (1) Evaporative cooling (EC), five cows; and (2) conventional shade (S), five cows. Blood was drawn at 60 and 90 d of lactation. Blood sampling, hormone and FFA assays were carried out as in experiment 1. Sequential samples were taken for 8 h at 12 min intervals starting at 2300 and then at hourly intervals from 1030 to 1830. In experiment 1, insulin was depressed (P <.05) treatment effects for T3 in either experiment. There were significant treatment differences (P <.05) in respiration rates and body temperatures in experiment 1. Shade were higher than AC or EC cows. These studies demonstrated that summer heat stress depressed insulin and increased FFA with variable effects on T4 and cortisol but no effect on T3.

One hundred and twenty lactating Holstein cows in mid-lactation were offered diets varying in protein level and degradability at two locations during hot and moderate weather. Treatments were: (1) High protein (19%), high degradability (65%); (2) High protein (19%), medium degradability (40%); (3) Medium protein (15.5%), high degradability (65%); (4) Medium protein (15.5%), medium degradability (40%). Diets were individually fed during hot weather at the University of Arizona Dairy Farm and contained 38.4% alfalfa hay, 12.4% cottonseed hulls, 9.8% whole cottonseed, and 39.4% concentrate (dry matter). Diets were group fed during moderate weather at the Brigham Young University Dairy Farm, Provo, Ut, and contained 31.3% corn silage, 14% alfalfa haylage, 9.4% whole cottonseed and 45.3% concentrate (dry matter). Average daily ambient temperatures were 35.1°C for hot and 26.8°C for moderate weather locations. Fat-corrected milk (3.5%, 2 x milkings) and milk persistency were lower for treatment 1 than other treatments. For the respective treatments during hot weather means were: 23.4, 26.6, 28.5, 28.4 kg/d; 83.2, 91.2, 90.9, 90.3%; and for moderate weather means were: (3 x milkings): 34.7, 31.8, 32.2, 32.4 kg/d; 97.0, 93.4, 92.1, 90.3%. Dry matter intakes during hot weather were 21.5, 21.9, 23.3, and 23.1 kg/d. Respiration rate and rectal temperature during hot weather were: 90.1, 87.9, 90.9, 94.7 counts/min; 39.0, 39.3, 39.3, 39.5°C and for moderate weather: 61.2, 58.2, 55.5, 67.4 counts/min; 38.8, 38.6, 38.7, 38.8°C. Serum T₃,T₄ and cortisol were generally unaffected by treatment, but were depressed during hot weather. Serum glucose was not significantly affected by treatments at either environmental locations. Animals consumed more water with highly degradable protein diets at each location along with consuming more water during thermal stress. These data show that 3.5% fat-corrected milk and milk persistency are significantly affected (P <.01; P <.025) by rations high in protein of high degradability during heat stress.

Two production trials were conducted for 84 d each. The first with 22 Holstein cows in late lactation. The second with 46 Holstein cows in early lactation. Treatments were C (control) and AO (A. oryzae 3g/d). Diets were for production trial 1 a 1:1 forage: concentrate ratio; for trial 2 was 2:3. Milk production in trial 1 was higher (P > .05) in AO fed cows during the first weeks of the trial. In trial two AO cows consistently produced more milk (P < .03). Rectal temperatures during hot weather (over 35°C) were consistently lower in AO fed cows, though not significant (P > .10). Two digestibility trials followed the production trials. For all digestion trials, Cr₂O₃ was used as digesta marker. In trial one AO tended to increase digestibility of DM (P > .10). In trial two digestibilities of DM, NDF and ADF were higher in AO fed cows (P < .05). Three other trials were conducted with mature Holstein cows fitted with ruminal and duodenal cannulae. The first trial tested two levels of forage (1:2 vs 2:1; forage to concentrate) and C vs AO in a 4x4 latin square design. AO increased (P < .05) ADF digestibility in the high concentrate died. No change (P > .10) in rumen pH, concentrations and proportions of VFA, and ammonia concentrations resulted from AO treatments. In the second trial C, AO and SC (Saccharomyces cerevesiae 3 g/d) were compared in a repeated 3x3 latin square design. A 1:2 forage to concentrate diet was fed to six lactating cows. Both AO and SC increased (P < .05) rumen NDF digestibility. The third trial compared C vs AO in a swithchback design with four lactating cows fed a 2:3 forage to concentrate diet. AO increased (P < .05) rumen fiber digestion. AO did not affect rates of passage of corn or alfalfa hay; or the potentially digestible DM of milo, alfalfa hay or wheat straw. AO did increase (P < .05) digestion rate of alfalfa DM. In vitro AO increased DM digestibility. That effect can be reproduced by incorporation of the additive at the time of inoculation.

This thesis provides an overview of the literature on reproduction attributes of the Holstein Friesian cattle and its influence on the cattle reproductive indices. One of the goals was to evaluate the influence of selected factors on the reproduction indices for a pre-selected group of dairy cattles. The data has been processed and sorted by the lactation production levels, daily production, order of lactation and the age of the first calving. The data about the used bulls has been processed as well. Another goal of the thesis was acquisition of the data about excluded cows. For the excluded cows, the age, order of lactation, reason for exclusion and life-long production have been recorded. The data for the thesis have been obtained from the production control records and database of breeds in the selected Holstein cattle breeding. The dairy cattles, which got in calf during the years 2017 and 2018 have been evaluated. In particular, for 2017 and 2018, the evaluation was carried out on 190 and 229 dairy cattles respectively, which makes the total of 419 evaluated cows. For those dairy cows, the insemination index data, insemination interval, gestation after first insemination, service period and gestation period has been recovered from the zootechnical register. The evaluation of excluded dairy cows contained 339 dairy cows, which have been excluded during years 2017 and 2018. For the evaluation of the used bulls, the total count and description of how the bull for insemination have been selected is provided. Evaluation the influence of level of lactation production on the reproduction indices has shown a significant (p0,05) statistical relation between production levels and duration of the service period. It has also been proven that this has an influence on the insemination index levels. The lowest values (p0,05) of service period and insemination index have been detected for dairy cattles with production up to 6 999 kg. On the other hand, the highest values of service period and insemination index have been recorded for the dairy cattles with production up to 9 000 kg (p0,05). The influence of daily dairy production levels on the reproduction indices have been evaluated as well. It can be clearly seen from the results that as the daily dairy production increases, the service period increases as well. The lowest values (p0,05) of the service period was recorded for breeds, who had the daily production levels up to 24.99 kg. Opposed to that, the highest values of service period have been recorded for dairy cattles with average daily milk production over 30 kg. The evaluation of order of lactation on the reproduction indices did not show any significant statistical results (p0,05). Furthermore, during the evaluation of first calving, no statistically significant differences have been shown (p0,05). Last reproduction index we have evaluated was gestation after the first insemination. The groups were divided by the production levels, daily milk production, order of lactation and age of the first calving. For each group, the percentage of cattles that got in calf after first insemination has been computed. On average, this value was 36.28%.

No description available.

No description available.

The effects of insulin on milk production were tested employing two different approaches. Firstly, 12 Holstein cows were used to determine the effects of feeding calcium propionate (Ca prop) on dry matter intake (DMI) and production traits. The experimental design was a switchback with 2 treatments (Ca prop at 0 or 300 g/d). The DMI was lower when animals received Ca prop. Ca prop did not affect the yield of milk and its components; however, Ca prop increased protein content. The (acetate+butyrate)/propionate ratio in rumen fluid 2 h after feeding was lower when cows received Ca prop. Plasma insulin concentration was not different between treatments and the putative effect of propionate as an insulin secretagogue was probably related to the maintenance of insulin levels when DMI was lower. In conclusion, Ca prop is a potential feed ingredient to increase protein content in milk. The second approach consisted of intravenous infusion of insulin. A trial was designed to test the effects of insulin, recombinant bovine somatotropin (rbST) and their interaction in lactating dairy cows. Eight Holstein cows were used in a Latin Square design with 4 treatments: (1) intravenous infusion of saline, (2) infusion of saline and administration of 40 mg of rbST per day, (3) intravenous infusion of 12 mg of insulin per day coupled with glucose infusion and (4) rbST administration combined with insulin and glucose infusion. The theory that rbST causes a peripheral resistance to insulin was confirmed. Insulin infusion increased percent protein, percent casein and decreased milk urea content regardless of rbST administration. For milk yield, protein yield, casein yield, lactose percent and lactose yield, there was an interaction between insulin and rbST administration. Similarly, there was an interaction between insulin and rbST on plasma IGF-I levels. Fat yield was higher, with a higher content of long chain fatty acids, during rbST administration, regardless of insulin infusion. I

Glucocorticoids are commonly used to treat cows with clinical ketosis and fatty liver disease. This study investigated the effects of 10 mg/mL of FlucortRTM and PredefRTM 2X on the day of calving on blood metabolites, immune function and milk composition on 30 transitional Holstein cows. Sample of blood and milk were analyzed for energy metabolites (glucose, NEFA, BHB and insulin), mineral metabolites (Ca, P, Na, K, Cl and Mg), energy function parameters (antibody, lymphocyte), milk compositional parameters (protein, fat, lactose, SCC). There were no differences in glucose, Na, Cl, Mg, antibody, lymphocyte and milk fat, were observed among treatments. FlucortRTM treated cows had significantly lower NEFA on D1, higher BHB on D21 and D28, lower insulin on D14, higher Ca on D1 and lower P on D1. PredefRTM 2X treated cows had significantly higher BHB on D21, higher insulin on D7, lower Ca on D1, higher SCC on D1 and higher milk protein on D1. With respect to the significant data in this study, the use of glucocorticoids FlucortRTM and Predef RTM 2X in a single intramuscular injection on d1 for the treatment of ketosis is not warranted.

The objective of this study was to estimate the relationship between survival at various stages of productive life (17, 30, 43, 55 and 96 months of productive life) and type traits in Quebec Holstein and Ayrshire cows. The original data set from the Programme d'Analyse des Troupeaux Laitiers du Quebec contained 559,203 lifetime records calculated from 2,237,081 lactation records including calvings from 1979 to 1995. Lifetime records containing type classification information provided by the respective breed associations were used to study true survival variables (opportunity to survive to 17, 302 43, 55 and 96 months) and functional survival variables opportunity to survive to the same ages, independently of the level of production). K. Meyer's EQREML program was used to analyse these data by fitting a sire model. Heritabilities varied between 0.03 and 0.11 for both breeds. Final score and rear udder were two of the traits most highly correlated with survival. Specifically, in Holsteins, mammary system and fore udder showed the highest genetic correlation with functional survival, and dairy character showed the highest genetic correlation with true survival. In Ayrshires, final score, breed character, dairy quality, style and fore udder had the highest genetic correlations with both true and functional survival across all survival stages. In a second study, lifetime records not having type information and type records without lifetime information were analysed with D. L. Johnson and R. Thompson's AIREML program which enabled linking of sires in common between type and lifetime data sets. Only survival to 96 months was studied here, but the effect of supervised and non-supervised records was considered. In Holstein supervised records, body traits were more highly correlated with survival, whereas udder traits were more highly correlated in the non-supervised records. Ayrshire results were not conclusive.

A series of studies were conducted to evaluate genetic and phenotypic aspects of culling, herd life and survival in Quebec Holstein herds. Data consisted of lactation records obtained from the Programme d'Analyse des Troupeaux Laitiers du Quebec (PATLQ) files, which included 2.2 Million records before the editing procedures. The average productive herd life in Quebec herds was approximately 33 months, corresponding to an average replacement rate of MIND, for both milk recording options. Herds enrolled in the PATLQ official option had cows with longer calving intervals and culled their heifers earlier than herds in the owner sampler option. The probability of being culled for each major reason for disposal was assessed by logistic regression models, and it was shown that culling for low production (voluntary) had a clearly descending trend from 1981 to 1994, while involuntary culling (assumed to include all the reasons other than production) increased in importance mainly because of the ascending trends observed for cuffing due to reproductive problems, mastitis and feet and legs problems. Proportion of cows culled for involuntary reasons increased with parity number, but the opposite occurred for culling due to low production. Herds in the official option culled less for mastitis and sold more cows for dairy purposes than owner sampler herds. After these preliminary studies, a sequence of Weibull models were fitted to analyze different aspects of the data. The genetic study of herd life traits focused on differences between sires regarding true and functional herd life, but also described the effect of different explanatory variables on the failure time variable. Heritability for true and functional herd life was, respectively, 0.09 and 0.08 in the log scale and 0.19 and 0.15 in the original scale. The difference in the median survival time of daughters of bulls with extreme proofs for functional herd life was 1.7 lactations. Quebec dairymen use classification fo