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

Thesis (Ph. D.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 4, 2009) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Aug. 14, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Animal Science, Department of Agricultural, Food and Nutritional Science, University of Alberta." Includes bibliographical references.

Berlin, Humboldt-University, Diss, 2003.

The effect of stage of lactation on milk yield, somatic cell counts, mineral and fatty acid profiles in pasture-based Friesian, Jersey and Friesian × Jersey cows was investigated. Twenty Friesian, twenty Jersey and twenty Friesian × Jersey cows were randomly selected from a dairy herd. A total of 202 milk samples were collected and analysed in three stages of lactation. Genotypic differences were observed in milk yield and fat content. Friesian cows produced the highest yield and lowest fat content whereas the opposite was true for Jersey cows (P<0.01). No significant differences were observed in SCC in the different genotypes, but SCC levels were higher in mid and late lactation (P<0.001). There was no effect (P<0.005) of genotype and stage of lactation interaction on Ca, P, Mg, Na, Mn and Bo concentration. Jersey cows had the least concentration of Fe and Cu in all stages of lactation. Strong positive correlations were observed among Ca and P, Mg and Zn. Aluminium had a strong positive relationship with Bo, Fe, Mn and Zn (P<0.001). Generally, SCC had a weak positive relationship with macro elements but a significant negative relationship with microelements. Yield levels were negatively correlated with Mg, Na, Al, Mn and SCC. Pasture ALA, SFA, n-3, n-6/n-3 and PUFA/MUFA concentration did not differ across the study period. Linoleic acid was highest in the second phase which coincides with mid lactation in cows (P<0.001). Highest moisture content coincided with the least fat free dry matter content in early lactation (P<0.001). Significantly high fat content was observed in late lactation than in early lactation. Highest butyric, caproic, linoleic, n-6 and PUFA were observed for Friesian cows. All other fatty acids ratios were not significantly different among different genotypes. Highest CLA, ALA, LA, SFA, PUFA, n-6, and n-3 and atherogenicity index were observed in early lactation whereas desaturase activity indices were highest in late lactation. Strong positive correlations were observed among milk vaccenic, ALA, LA and CLA concentrations. Inverse relationships were observed between SFA and long chain fatty acids. It can be concluded, it may be of advantage to consume milk from early stage of lactation poses a lower risk to coronary diseases and are much safer to consume.

This study, being part of a larger project - "Canadian/New Zealand GxE Interaction Trial" - is comparing Canadian and New Zealand sired heifers for growth traits within Canada, since differences for growth traits were found in the Polish strain comparison (Jasiorowski et al., 1987) and due to selection programs in the two countries. Twenty Canadian Holstein and twenty New Zealand Friesian progeny tested, A.I. bulls were randomly mated to over 1,000 cows in 10 Canadian herds. 3,539 records of weight and wither height from 475 heifers (i.e. 241 Canadian and 234 New Zealand sired) were generated. Subsets of the data for different stages of heifer maturity were analyzed separately. Herd and strain effects least squares means were estimated using analysis of variance. Genetic and phenotypic and correlations and heritability for weight and wither height were estimated by a Derivative-Free Restricted Maximum Likelihood (DFREML) algorithm and an animal model (AM). No differences were found between sire strains for weight except at 15 and 18 months where sib groups of Canadian (CN) sires were heavier than their New Zealand (NZ) contemporaries (393 vs 386 kg and 447 vs 445 kg, respectively). CN sired heifers were taller at all ages except at birth, 3 and 9 months of age. At 24 months CN heifers were 136 cm while NZ heifers were 133 cm. Heritability estimates for weight at birth was 0.62 for the CN strain and 0.59 for the NZ strain. CN estimates (3 to 6 months) and NZ estimates (3 to 9 months) were close to zero. Between 9 to 24 months CN strain estimates ranged from 0.44 to 0.69 while NZ estimates were 0.17 to 0.51. The joint estimates ranged from 0.10 to 0.66. Heritability estimates for wither height for CN strain at birth and between 9 to 21 months were between 0.34 to 0.66 and close to zero between 3 to 6 and at 24 months. The NZ estimates at birth, 18, 21 and 24 months were between 0.36 to 0.93 but close to zero between 3 to 15 months. The joint estimates ranged from 0.32 to 0.75 between 12 to 24 months. Genetic correlations between weight and wither height ranged from 0.62 to 1.0 for CN strain and from -0.04 to 0.91 for NZ strain between 4.5 to 21 months. At six months of age the genetic correlation for CN strain was -0.01 and NZ strain was 0.54. At birth, both sire groups had a genetic correlation of 1.0. At 24 months NZ strain had a genetic correlation of 0.84 while that of the CN strain was 0. Genetic correlations for the joint analysis ranged from 0.61 to 1.0 for all ages except at 6 months (0.18). Phenotypic correlations between weight and wither height were between 0.33 to 0.60 for CN group and 0.33 to 0.62 for NZ group. The joint estimates were 0.36 to 0.61. There were no differences in the phenotypic variances except at 9, 12 and 15 months. Genetic variances were different at all ages except at birth for weight. / Land and Food Systems, Faculty of / Graduate

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