Data sets from six locations containing 631 dairy heifers and 5409 observations of individual dry matter intake (DMI) were used to develop an equation to predict DMI. Data were contributed by Pennsylvania State University, University of New Hampshire, Purina Mills, Kansas State University, University of Minnesota, and Virginia Tech. Objectives varied by location and trials within locations but all contained DMI (kg/d), BW (kg), age (wk), DM, and CP, and ADF percentages of ration DM. Daily gains (g) were calculated from consecutive BW. Season was expressed as sine wave of Julian day plus 60 d times Ï divided into 180. Average daily temperature, humidity, and wind data were collected from Minnesota and Virginia and analyzed with BW to determine their effect on DMI. Sire PTA milk, protein, and fat of heifers were recorded from all sources to determine the relationship of genetics with DMI. Diet measurements (DM, CP, and ADF percent of ration DM) were analyzed with BW to determine their impact on DMI. Two equations were developed using backwards elimination techniques. The first equation was: DMI = -12.63 + .0587(BW) - .0000264(BW2) - .000 12(BWxDM) - .000477(BWxADF) + .292(DM) - .00103(DM2) - .413(CP) + .01349(CP2) + .181(ADF) - .0025(DMxCP) - .00269(DMxADF) + .00509(CPxADF) with an R2 of .90. Because body weight and diet variables were highly correlated, a smaller model could be created with one diet variable. A smaller model would also be more practical to use if accuracy was not lost. Body weight and ADF were used for second model: DMI = -1.71 + .0429(BW) - .0000246(BW2) - .00023(BWxADF) + .032(ADF) - .00068(ADF2) with an R 2 of .87. Previous DMI prediction equations from Virginia Tech were validated using all data from other locations and had R2 of .90 and .84 with this data set. Body weight raised to the .53 power most accurately described the relationship of DMI and BW. Temperature and DMI had a quadratic relationship. Higher DMI were observed at extreme temperatures between -10 to 27° C. Humidity and temperature x humidity accounted for more variation of OMI than season and other environmental measures, but were not included in the small model due to availability of these measurements and they did not change OMI by .1 kg/SO. Sire PTA milk by groups showed differences among heifer groups although no trends were found. Dry matter percent and CP percent had linear and quadratic relationships with OMI. Maximum OMI plateaued between 75 and 950/0 OM and occurred at extreme percentages for CP between 9 and 27%. Acid detergent fiber percent had a negative linear relationship with OMI between 7 and 45%. / Master of Science

En début de lactation, la vache subit un stress important occasionné par l’impossibilité de combler l’ensemble de ses besoins énergétiques par sa consommation exogène. Cette période spécifique se caractérise par une balance énergétique négative, entraîne une utilisation excessive des réserves corporelles de l’animal et représente un défi métabolique important. Ironiquement, depuis maintenant plus de 40 ans, le système incite les producteurs laitiers à effectuer l’insémination au jour 60 post-partum, c’est-à-dire au moment où la vache rencontre un déficit métabolique. Ce déficit au moment de la conception aurait un impact chez la progéniture, notamment au niveau épigénétique. Ce projet consiste à documenter l’effet de la balance énergétique négative sur la qualité de l’embryon et, en l’occurrence, à proposer des pistes afin d’améliorer la fertilité des bovins laitiers. La mesure du bêta-hydroxybutyrate (BHB) a été effectuée à partir d’échantillons sanguins entre 45 et 60 jours post-partum sur dix-huit vaches de race Holstein. Selon la mesure obtenue, la vache fut classée comme étant faible ou élevée en BHB, afin d’avoir au moins six vaches par groupe. Après un processus de stimulation ovarien, chaque vache fut inséminée et les embryons, récoltés. Pour chaque vache, deux embryons ont été transférés dans deux primipares, afin de déterminer subséquemment la persistance des marqueurs dans le matériel biologique. Grâce à la plate-forme EmbryoGENE, il fut possible de déterminer l’expression génique ainsi que l’état de méthylation de l’ADN des embryons récoltés. Les résultats obtenus soutiennent l’existence d’une altération du métabolisme énergétique au niveau embryonnaire, notamment par la modification de la voie de signalisation de mTOR ainsi que celle des sirtuines. Cette altération semble se traduire par une dysfonction mitochondriale et une inhibition de la transcription, entraînant un freinage au niveau cellulaire, probablement dû à la programmation de l’embryon à utiliser ses réserves lipidiques lors de conditions importantes de stress. / In early lactation, the cow undergoes an important stress generated by the impossibility of filling its entire energetic needs by exogenous consumption. This is characterized by a negative energy balance, excessive use of animal body reserves and represents an important metabolic challenge. Ironically, for more than 40 years now, the system has been encouraging dairy farmers to inseminate on day 60 postpartum, when the cow has a metabolic deficit. This deficit at the time of conception could impact the offspring, especially at the epigenetic level. This project is meant to document the effect of the negative energy balance on the quality of the embryo and to identify ways to improve the fertility of dairy cows. The beta hydroxybutyrate (BHB) measure was done from blood samples between day 45 and 60 postpartum on eighteen Holstein cows. According to the measure obtained, each cow was classified as low or high in BHB, so as to have at least six cows per group. After an ovarian stimulation process, each cow was inseminated and the embryos were harvested. For each cow, two embryos were transferred in two primiparous cows in order to subsequently determine the persistence of the markers in the biological material. With the EmbryoGENE platform, it was possible to determine the gene expression as well as the methylation status of DNA embryos. The results obtained support the existence of an alteration of the energetic metabolism at the embryonic level, especially by the modification of the signaling pathway of mTOR as well as those of the sirtuins. This alteration appears to result in mitochondrial dysfunction and inhibition of transcription, leading to a reduced activity at a cellular level, probably due to programming of the embryo to use its lipid reserves during severe stress conditions.

A total of 114,351 Holstein first lactation records collected by the Quebec Dairy Herd Analysis Service (DHAS-PATLQ) between September, 1979 and January, 1994 were used to study the effects of adjusting records for linear and quadratic effects of 90- and 305-d feed intake measures (total energy, total protein and total dry matter) on estimation of heritabilities of and genetic correlations among yield and composition traits. Genetic parameters of feed intake measures, relationships between feed intake and age and weight at calving, and feed conversion efficiency traits were also examined in a series of studies. A sire model fitted by REML estimated heritabilities of 305-d milk, fat and protein yields, fat and protein percents as .45 +/- .04, .48 +/- .04, .44 +/- .03, .92 +/- .06, and .88 +/- .05, respectively. Correction of 305-d records for differences among cows in feed intake levels reduced heritabilities of milk, fat and protein yields to .35 +/- .03, .52 +/- .04, and .38 +/- .03, respectively. Heritabilities of composition traits (fat and protein percents) remained unchanged. Genetic and phenotypic correlations for yield traits were also reduced (48--170%, and 16--51%, respectively) which may indicate that genetic associations between yield traits are less than what we believed them to be. Heritabilities of 305-d total energy, total protein, total DM intake, grain energy, grain protein, grain DM, base energy, base protein, and base DM were .30 +/- .03, .24 +/- .02, .35 +/- .03, .23 +/- .02, .23 +/- .02, .23 +/- .02, .31 +/- .03, .26 +/- .02, and .40 +/- .03, respectively. Genetic correlations between feed intake measures were very high; they were approaching unity in some cases. Therefore, any one of these feed intake measures can represent the others. A multi-trait REML analysis estimated heritabilities of age and weight at first calving as .11 +/- .01 and .37 +/- .03, respectively. Age at calving was negatively associated with yield traits and with total e

The objective of this thesis was to test for associations between genetic polymorphisms of genes related to immune response (growth hormone (GH), growth hormone receptor (GHR), ornithine decarboxylase (ODC), insuline-like growth factor-1 (IGF-1), adrenocorticotropin hormone (ACTH), corticotrophin releasing hormone (CRH), and prolactin (PRL)) and mastitis resistance traits (incidence of clinical mastitis (ICM), occurrence of clinical mastitis (OCM), culling due to mastitis (CDM), and somatic cell scores (SCS)) in Canadian Holsteins. / Using lactation records of cows enrolled in milking recording in Quebec (Programme d'Analyse des Troupeaux Laitiers du Quebec, PATLQ from 1980 to 1994 (411,291 first, 238,432 second, and 130,983 third lactations, respectively) Estimated Transmitting Abilities of traits were generated with a model that included the random effect of sire, and fixed effects of herd-year-season-of calving, age at calving, and genetic group. 721 bulls which had daughters in the phenotypic data sets were genotyped for twenty polymorphisms of the above genes located on autosomes (BTA) 5, 11, 14, 19, 20, and 23. / Two types of analysis of associations were performed: analysis across-population with a model that included the fixed effect of marker and random effect of the son of grandsire, and within-family analysis with a model that included the fixed effects of the grandsire, marker nested within grandsire, and the random effect of son nested within marker and grandsire. Permutation tests were performed to reduce Type I error probability. / Significant associations were found within families for markers of IGF-1 (BTA5), ODC (BTA11), GH (BTA 19), GHR (BTA 20), and PRL (BTA 23) for ICM, OCM, CDM, and SCS in different lactations. Some of these putative quantitative trait loci (QTL) are located on BTA where other authors have reported QTL affecting SCS and udder conformation. The results from this study may contribute to efforts to dissect the genetic basis of mastitis resistance in dairy cattle.

No description available.

No description available.

Two trials using 32 heifers each evaluated response to undegraded intake protein (UIP) (30 or SO% CP), energy (supporting .S9 or .91 kg ADG), and source of UIP (blood meal or combination protein supplement). Trial one was a 2x2 factorial, with two levels of energy and UIP. High UIP was achieved with blood meal supplementation. From 6-13 mo of age (phase I), high energy increased ADG and DMI, and high UIP decreased DMI. DM efficiencies (kg DMIlkg BW gain) improved with high energy and high UIP, and roN efficiencies (kg IDN/kg BW gain) improved with high UIP. From 13 mo until calving (phase n), heifers were housed together and fed a common diet. Low energy, high UIP treatment had the highest ADG (1.01 kg/day) for phase I, but the lowest for phase n (.33 kg/day), and low energy, low UIP treatment had the lowest ADG (.62 kg/day) for phase I, but the highest for phase n (.S3 kg/day). Overall ADG from 6 mo until calving averaged .S9 kg/day, and was not affected by energy or UIP. In trial 2, two levels of energy and two sources ofUIP were compared, resulting in four treatments: low energy, high UIP with combination protein supplement; low energy, high UIP with blood meal; low energy, low VIP with soybean meal; and high energy, low UIP with soybean meal. Combination protein supplement contained blood meal, com gluten meal, and fish meal. Trial was 300 days long, and began at 6.5 mo. of age. Dry matter intake and ADO were increased with high energy, but not affected by VIP. Overall DM efficiency was not affected by VIP or energy level. Results of both trials indicate VIP may improve feed efficiency of growing Holstein heifers. / Master of Science

Growth and body composition of 121 Holstein heifers (4.6 to 18 mo and 129 to 407 kg) reared on pasture, drylot and pasture-drylot systems were evaluated in 6 experiments. Heifers were switched from drylot to pasture or the reverse to study carry-over effects from previous treatments; both systems were satisfactory. Alternate 28-day periods of supplement feeding to grazing heifers did not affect final body weight nor wither height, but ADF and heart girth varied during 2 yr. When switching drylot heifers previously fed low and high TDN, to pasture, gains were best for heifers fed the lower TDN diet; also, gains on pasture were best for light heifers. Gains by all heifers grazing mainly orchardgrass-clover pasture were acceptable, but supplementing with a 19% CP concentrate or lasalocid, usually improved gains. Heifers with lowest BW during grazing made compensatory gains in drylot. Urea space estimation technique showed that compensatory gains were mainly fat. Lasalocid feeding increased daily gain and subcutaneous fat deposition but reduced feed intake and ribeye area. When moving grazing heifers to drylot a total mixed ration with fishmeal or soybean meal as protein sources gave similar responses. DM intake of grazing heifers ranged from 8.1 to 10.1 kg/d, vs 7.5 kg/d for arylot. Supplementing grazing heifers with degradable or undegradable protein gave similar responses in growth and body composition. Based on growth and body composition, seasonal grazing of Holstein heifers may reduce costs for rearing replacement heifers. A corn silage-alfalfa silage-orchardgrass hay mixed ration without concentrates when fed ad libitum to heifers in drylot resulted in gain of 934 g/d. Pasture alone heifers gained from 368 to 755 g/d depending on drought and heifer age. Calculations of costs of rearing Holstein replacement heifers were prepared accounting for observations of response to grazing, supplements to grazing and drylot diets. Well managed grazing reduces costs of rearing. / Ph. D.

No description available.

Two trials were conducted to determine the effect of protein degradability (low (LD) vs high (HD)) and evaporative cooling (shade cooling vs shade) on performance of 60 lactating Holstein cows in mid-lactation. Cooling and the LD diet increased milk production, 3.5% FCM and feed efficiency in trial 1 (24 cows) while in trial 2 (36 cows) LD diet increased milk production and feed efficiency and cooling did not exert a significant effect. Differences between trials were probably due to higher environmental temperature humidity indexes (77.0 vs 72.0), and a higher quality of the rumen bypass protein in the LD diet in trial 2 than trial 1. Cooling reduced respiration rates in trial 1 and respiration rates, rectal and inner ear temperatures in trial 2. Eating patterns were unaffected by protein degradability or cooling.