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Small ruminant species are utilized for their diverse products including meat, dairy products, and wool. Effective and humane management are essential to maintain high production rates and comfortable animals. To attain this objective, managers needs to have an extensive knowledge of husbandry techniques, understanding of physiological processes, and familiarity with nutritional requirements. We examined the effects of varying feed components on two different ruminal species. In Chapter 1, we conducted a study to evaluate"¯the effects"¯of a low metabolizable energy (LME) and high metabolizable energy (HME) diet on twenty-two Friesian/Lacuane"¯cross ewes and lamb nutritional status."¯Effects on milk production during early lactation stages"¯and the growth of the neonatal lambs were also investigated. We anticipate energy levels will have an effect on milk production and lamb growth. Our results indicate that ewes on the LME diet produced more milk with higher concentrations of fat though this group maintained lower body condition. We concluded that neither the HME nor the LME diet met the needs of the sheep due to the shift in nutrient partitioning towards milk production rather than allocating nutrients to maintaining both body condition and milk production. Limited energy requirements are further evidenced by the decline in back fat (BF) for both the HME and LME groups for the duration of the study. We determined the degradation parameters of grass hay supplemented with soybean meal (SBM) and the effects of SBM on compartment 1 (C1) ammonia and volatile fatty acid (VFA) concentrations in alpacas. Our findings show that the degradation rate was not different for dry matter (DM), but it was for crude protein (CP) (P<0.05). With this data it can be concluded that SBM can be a CP supplement when the diet is insufficient to improve microbial yield. It should be noted that care should be taken to avoid causing a protein-energy imbalance. The results of these two studies indicate shifts in nutrients availability and changes in feeding strategies can affect both the health of the animal and their subsequent offspring.

Until recently, occurrence of milk fever (MF) has been attributed to prepartum calcium intake. However, researchers in Iowa have concluded that high prepartum dietary potassium (K) is the major cause of MF. Potassium concentrations have been increasing on manure fertilized soils over the last 20 years. Grasses grown on these fields mirror the increase in available soil K. When high K forages are fed to dry cows, it has been associated with increased MF in some, but not all cases. Our objective was to identify factors that differed between low and high occurrence of disorders when high K forages were fed. For 1 yr, monthly interviews were conducted on 10 dairies in Western Oregon. Close-up rations, dystocia rating, crowding, and cow comfort data were collected. Cows were diagnosed healthy or having one or more of the following metabolic diseases: MF, retained fetal membranes (RFM), and left displacement of the abomasum (LDA). Feedstuffs were collected each month and analyzed for dry matter, crude protein (CP), acid detergent fiber (ADF), and macrominerals. Of the multiparous cows (n=3,587) included, incidences of MF, RFM and LDA were 3.6, 11.3, and 1.5%, respectively. Increasing MF occurrence was associated with uncomfortable conditions, dystocia, increasing prepartum dietary Na and ADF, and increasing Ca to P ratios; there was also a dietary K by Mg concentration interaction. Increased dietary concentrations of Mg can prevent MF if dietary K is <2.6%. In addition, dietary conditions of K >2.6% and Mg >0.4% increase the occurrence of MF. Inversely, high concentrations of K can prevent MF in a Mg deficient diet. Dietary factors associated with an increase in the occurrence of RFM are increased dietary concentrations of Ca, S, CP, use of anionic salts, and the K forage source. Factors associated with an increase in hypocalcemia in the postpartum cow are crowding, uncomfortable housing, and a dietary K by Mg concentration interaction. In conclusion, improved cow comfort, and the addition of Mg to high K forage diets could decrease the risk of the cow exhibiting MF, RFM, and hypocalcemia. / Graduation date: 1999

Four lactating Holstein cows fitted with ruminal and duodenal cannulae were used in a 4 x 4 Latin square design to determine the effects of feeding raw and heat-treated flaxseed on ruminal fermentation parameters, ruminal fatty acid biohydrogenation (BH), nutrient utilization in various segments of the gastrointestinal tract, and plasma and milk composition of lactating dairy cows. Four diets were formulated: a control diet with no flaxseed (C); a raw flaxseed (RF); a micronized flaxseed (MF); and an extruded flaxseed (EF) diet. Ruminal pH, NH3N and total volatile fatty acids were not affected by dietary treatments. However, feeding flaxseed decreased ( P < 0.01) molar proportion of acetate and increased ( P < 0.01) that of propionate. Ruminal fiber digestion was lower (P < 0.04) for cows fed the flaxseed diets relative to those fed C. Feeding flaxseed had no effect on milk yield, milk fat and protein content, and milk fat yield, but decreased (P = 0.02) milk protein yield. (Abstract shortened by UMI.)

The growth hormone receptor gene (GHR) has been previously documented to be a good candidate gene for detection of a quantitative trait locus (QTL) which influences milk production in Holstein cattle. In this study, the promoter region of the GHR gene and microsatellite markers AGAL29 and BM5004 were studied. Their effects on milk yield (MY), fat yield (FY), protein yield (PY), fat percentage (FP) and protein percentage (PP) were examined. DNA was isolated from 1746 used by the artificial insemination (AI) industry representing 26 half-sibling families. Three polymorphisms in the GHR gene were genotyped (GHRAlu, GHRAcc and GHR Stu) along with both microsatellites. The markers were analyzed in a cross-family analysis. The model included a population mean, a fixed grandsire effect, a fixed allele effect and a random residual error. The data was also analyzed using a nested model in a granddaughter design to investigate a possible consistency in the allelic effect in individual families. Lastly, the data was analyzed using the haplotypes of GHRAlu and GHR Acc, using the same model as the cross-family analysis. It included an analysis of a fixed haplotype effect instead of a fixed allele effect. (Abstract shortened by UMI.)

In dairy cattle, treatment with exogenous growth hormone (GH) affects growth and function of mammary gland. The actions of GH are mediated via interaction with GH receptors (GHR). The first step in signal transduction is homodimerization of two GHR molecules by GH. This step is critical since mutation in either GH or GHR can block dimerization and thus target cell activation. However, association between milk related traits and combination of GH and GHR variations are not known. Accordingly, DNA genotypes in the GH and GHR genes were investigated for association with milk, fat and protein lactation yields in Holsteins. The marker data were obtained on 873 progeny tested bulls by using PCR-RFLP and PCR-SSCP analysis. There were five markers in GH and three in GHR. Estimated breeding values (EBVs) were obtained from Canadian Dairy Network for milk, fat, and protein lactation yields for the 873 genotyped bulls. / There was significant difference among GH6.1 alleles (C-to-G transversion at position 2141) for the milk yield (P < 0.05) and protein yield (p < 0.05). There were significant differences in GHR AluI (A-to-T transversion at -1182) for milk (p < 0.05) and fat (p < 0.05), and GHR StuI (C-to-T transversion at -232) for fat (p < 0.0001) and protein (p < 0.05). Allele frequencies for GH6.1 (C), GHR AluI (A) and GHR StuI (C) alleles in bulls genotyped were 0.95, 0.63 and 0.95, respectively. Bulls with GH6.1 (C/G) genotype had higher milk EBV (p < 0.05) compared to C/C bulls. Bulls with GHR AluI (A/A) genotype had higher milk EBV (p < 0.01) and fat EBVs (p < 0.05). Bulls with StuI (C/C) genotype had higher fat EBV (p < 0.0001) and protein EBV (p < 0.05) compared to StuI (C/T). This study indicates that the combination of GH and GHR markers could serve as a tool to aid in selection for improving milk, fat, and protein production.

Increase in profits corresponding to a one unit increase in Estimated Breeding Value (EBV) for 3 production traits and for 21 type traits were estimated from 31,123 merged "Official" first lactation records, type records and Estimated Breeding Value (EBVs) records of Canadian Holstein cows using multivariate REML and a mixed model accounting for herd and year of calving effects. The same regression model was used to estimate the same profit increases corresponding to a one unit change in EBVs from 336 merged "Non-Official" first lactation records, type records and EBV records of Canadian Holstein Cows to investigate whether purebred breeders are selecting their animals according to type and production performances while commercial producers are selecting animals that maximize their milk profits. Finally, the usefulness of DHAS cow records for increasing milk profits was investigated by comparing the average profit level of cows with "Official" milk records and their time of registration under the DHAS scheme. / Size had the largest negative impact on profits, with estimates ranging from $-$41.70 $ pm$ 6.60 to $-$26.62 $ pm$ 5.91. Chest width and fore attachment had the largest positive impact on profits, with estimates ranging from 4.30 $ pm$ 5.94 to 16.82 $ pm$ 6.00 and from 4.71 $ pm$ 3.52 to 14.57 $ pm$ 3.97 respectively. Grade cows were found to have on average lower EBVs for most type and production traits than purebred cows. However, grade and purebred cows generated similar milk profits. Finally, the efficiency of using information provided by DHAS to increase profits did not increase with the number of years of participation with DHAS.

This trial was carried out in order to elucidate factors affecting milk urea nitrogen (MUN). Twenty-five herds were selected for MUN testing. Three sampling periods were chosen. The first occurred during the months of March and April, the second during July and August, and the third during November and December 1997. A total of 2,686 samples were collected and analyzed. Two different methods were employed for MUN analysis and were referred to as the Macdonald Campus method (MUN-MAC) and the Programme d'Analyse des Troupeaux Laitiers du Quebec method (MUN-P.A.T.L.Q.). The MUN-MAC consists of an enzymatic method while the P.A.T.L.Q. method is an infra-red method. Prior to initiation of the trial, the MUN-MAC method was validated and found suitable for use in this experiment. The results demonstrated that the factors which significantly contributed to the models were the ration's net energy of lactation, season, region, somatic cell count, total dry matter, neutral detergent fiber, non-structural carbohydrates, total fat, crude protein, protein to energy ratio, starch to protein ratio, parity and days in milk. (Abstract shortened by UMI.)

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