Sheep production is an important socioeconomic activity for the small producers and it can represent their primary income source. Gastrointestinal parasites have become the principal limiting factor for this industry around the world, especially because of the anthelmintic resistance phenomenon that has been increasing worldwide. The negligent use of anthelmintics has been reported as the main factor in the development of resistance. Among the parasites that infect sheep, H. contortus is considered the most harmful and also the parasite responsible for the fastest development of nematode resistance in small ruminants. Due to the economic impact this parasite may bring upon producers, the search for alternative methods of control has become a necessity. The use of condensed tannin containing forages and copper oxide wired particles have been shown to produce promising results. Studies have shown that both of these control methods can reduce fecal egg counts, worm fecundity, egg hatchability and larvae development of H. contortus. The general objective of this research was to evaluate the effect of inorganic copper and condensed tannins on fecal egg counts of naturally infected animals and consisted of three trials. No significant differences were observed in the trials using condensed tannins as the main effect in parasite control (p>0.05). It was possible to observe that the number of H. contortus larvae decreased in the treated group, but the differences were not significant (p>0.05). A significant difference in fecal egg counts in the inorganic copper trial was observed (p<0.05). The copper oxide group yielded the greater reduction throughout the study (p<0.001). Copper sulfate was able to reduce fecal egg counts but there was no difference between this group and the control group, which did not receive any treatment (p>0.05). The use of condensed tannins did not show reductions in parasite load, but its use should not be discarded especially in areas where the use of anthelmintics is no longer possible. Inorganic copper has been shown to reduce GIN infection and its concomitant use with other control methods may represent a useful tool in controlling parasites.

The objectives of this research were to determine whether delaying the feeding of a diet with reduced crude protein, supplemented with L-Lysine, for several days post-hatching, would result in improved growth performance of broiler chicks and determine an optimal time to feed such a diet to the chick. All experiments were conducted in brooder batteries from 0- to 14- or 18- days (d) post-hatching. Treatments contained a minimum of 6 replicate pens with at least 6 broilers per pen. Two experiments were conducted to determine whether delaying the feeding of a corn-soybean meal (SBM) diet with reduced CP for either the first 5 or 10 days post-hatching would result in improved growth performance of broilers. The results of these experiments show that even when the diets are not deficient in amino acids (AA), feed efficiency is negatively affected by switching birds to a low CP diet several days after post-hatching; effects on daily gain are minimal until the diet becomes deficient in AA. Two experiments were conducted to determine the optimal time to feed a diet with reduced CP, supplemented with L-Lysine, to the chick. The results of these experiments indicate that as long as the diets are not deficient in AA, overall growth performance during the starter phase is not negatively affected for broilers switched from diets with reduced CP to one with an adequate level, at day 5 or day 10 post-hatching, or those fed the reduced CP diets continuously.

Excess protein in dairy cattle diets unnecessarily increases the cost of production and may contribute to environmental pollution. The objective of this research was to evaluate the effect of feeding dairy cows with two levels of dietary protein on animal performance and manure characteristics. Two experiments were carried out with 24 lactating dairy cows each. Experiment 1 was corn silage based and had a control TMR (HP1) estimated to contain 16.5% CP with SBM and treatment TMR (LP1; 13.5% CP) using DDGS and rumen protected Lys and Met. Experiment 2 was ryegrass haylage based and had a control TMR (HP2) with 15.5% CP with Met and a treatment TMR (LP2) with 13.5% CP with Lys and Met. Experiments were analyzed as a crossover design using the MIXED procedure of SAS with pen as the experimental unit. Experiment 1 had no significant difference between treatments in DMI (21.0 for HP1 and 20.4 kg/cow/d for LP1; P=0.46) and milk yield (20.7 for HP1 and 20.5 kg/cow/d for LP1; P=0.91). Percentage of milk components averaged 4.21, 3.72, 4.54, and 9.15, respectively for fat, protein, lactose, and solids non-fat (P>0.60). Milk urea nitrogen (MUN) decreased (P<0.01) from 17.2 with HP1 to 9.93 mg/dL with LP1. Manure pH was significantly higher for HP1 than LP1 (7.87 and 7.53 respectively, P<0.05). Experiment 2 had no significant difference in cow performance (DMI: 21.4 for HP2 and 20.9 kg/cow/d for LP2; P=0.51; milk yield: 26.4 for HP and 24.4 kg/cow/d for LP2; P=0.19; percentage of milk components averaged 3.48, 3.29 and 4.71, respectively for fat, protein and lactose; P>0.30; MUN decreased (P<0.01) from 9.85 with HP2 to 6.40 mg/dL with LP2). Manure pH was significantly higher for HP2 than LP2 (7.50 for HP and 7.13 for LP, P=0.05). There was no difference in volatilized N between HP2 and LP2. This experiment suggests that performance of late-lactation dairy cows can be maintained with low-protein DDG based diets supplemented with Lys and Met.

Two experiments assessed the potential of altrenogest, an artificial progestogen, and deslorelin acetate, a gonadotropin-releasing hormone (GnRH) agonist, for suppressing estrus and ovulation in cyclic mares. In the first experiment, mares were administered a luteolytic dose of prostaglandin-F2á on d 6 of diestrus, and were then treated with 1 of 3 formulations of altrenogest in slow-release vehicle (6 mares/group): 1) Biorelease altrenogest LA150 (225 mg total as a 1.5 mL injection); 2) Biorelease altrenogest LA225 (225 mg total as a 1.0 mL injection); or 3) Biorelease altrenogest LA225 (450 mg total as a 2.0 mL injection). Six control mares received vehicle. Compared to control mares (10.0 days), time to ovulation was greater (P < 0.01) for all mares receiving altrenogest (17.5 days overall); there was no difference (P > 0.5) among groups receiving altrenogest. Control mares (6 out of 6) first displayed estrus an average of 4.5 days after prostaglandin-F2á injection; of the 18 mares receiving altrenogest, 11 displayed first estrus at an average of 13.5 days (P < 0.02 relative to controls) and there was no difference (P > 0.19) among groups. It was concluded that the 3 formulations of altrenogest were equally effective in delaying estrus and ovulation in cyclic mares. It is suggested that a 10-day injection interval could be used to keep mares out of heat for extended periods of time. The second experiment was similar to the first, except that there were 2 groups: 1) control mares that received a vehicle injection and 2) mares that received an i.m. injection of 1.5 g of deslorelin acetate in biodegradable microparticles. Administration of deslorelin did not affect (P > 0.1) the day of first onset of estrus or the day of ovulation. There was a tendency (P = 0.08) for deslorelin treated mares (3 out of 7 vs. 0 out of 6 controls) to not show estrus at the expected time, even though they experienced luteolysis and ovulation. It was concluded that injection of 1.5 g of deslorelin acetate was not an effective method for suppressing estrus and ovulation in cyclic mares.

Four experiments were conducted in an effort to develop a method, based on prolactin secretion, for assessing the efficacy and duration of activity of dopaminergic agonists for the treatment of pituitary pars intermedia dysfunction (PPID) in horses. In the first experiment, prolactin response to a low dose of the dopamine antagonist, sulpiride, was generally repeatable in estrogen-primed geldings in winter over 8 every-other-day challenges. It was concluded that estrogen-primed, sulpiride-challenged geldings in winter could serve as a model for the study of potential dopaminergic drugs for the treatment of PPID in horses. The second experiment was performed in the summer with mares, and again tested the repeatability of the prolactin responses over a 30-day period. The responses in mares were generally repeatable, and there was no effect due to stage of the estrous cycle. It was concluded that mares could serve as a model for the study of potential dopaminergic drugs as well as geldings, and stage of the estrous cycle did not have to be taken into account. In the third experiment, two formulations of the dopamine agonist, pergolide, were tested (oral administration versus injection) against a single formulation of cabergoline (injected) and control injections (vehicle) for their efficacy to reduce unstimulated plasma prolactin concentrations in geldings. Oral pergolide reduced prolactin concentrations for a few hours, whereas injected pergolide suppressed prolactin concentrations for 24 hours. Cabergoline suppressed prolactin concentrations for up to 5.5 days. It was concluded that the injectable formulations had potential for further study as possible treatments for PPID in horses. The last experiment tested the efficacy of daily pergolide injection versus a single injection of cabergoline, for suppressing the prolactin secretion induced by low dose sulpiride injections in mares. Daily injection of pergolide suppressed prolactin responses as long as the injections were given, plus another 2 days. The single cabergoline injection suppressed prolactin responses for a minimum of 10 days. Based on these results, cabergoline in slow-release vehicle seems to provide an excellent possibility for administering dopaminergic activity to horses with PPID. Whether these results are directly applicable to PPID horses needs to be determined.

Three experiments were conducted to further study the use of intravenous insulin injection to measure insulin sensitivity in horses. In the first experiment, glucose responses to multiple doses of recombinant human insulin were compared in insulin sensitive and insensitive mares. Regression lines describing the responses in insensitive mares had less (P = 0.003) steep slopes and greater (P = 0.006) effective doses at 50% response (ED50) compared to sensitive mares. Curvilinear regression models provided a good fit (R2 = 0.95) for the prediction of ED50 from the individual responses to 50 mU/kg BW insulin. The second experiment estimated the repeatability of the glucose responses to a fixed dose of insulin in 41 horses (mares and geldings) injected twice, between 7 and 14 days apart. Overall agreement between the responses was significant (P < 0.001) but not high enough to be predictive (R2 value = 0.384). Intra-horse coefficients of variation (CV) ranged from 0 to 68.7%, and averaged 23%. Mares and geldings were similar in their repeatabilities. Horses in the bottom half of the sensitivity rankings had a greater (P = 0.03) average intra-horse CV (28.7 ± 4.6%) than horses in the top half (16.7 ± 2.2%). In the third experiment (single switch-back design), glucose responses to a fixed dose of insulin were compared after an overnight (about 12 hours) versus a 24-hour period of feed deprivation in geldings previously determined to be insulin sensitive (n = 4) versus insensitive (n = 4). The longer period of feed deprivation decreased (P = 0.06) the percentage decrease in blood glucose concentrations, indicating a lesser sensitivity relative to the 12-hour period of deprivation. Insulin sensitivity also affected (P = 0.0003) the glucose response, with sensitive geldings exhibiting the greater response. It was concluded that the response to a single dose of insulin is often a good predictor of a horse's insulin sensitivity, but that the lack of repeatability in some horses could lead to errors in diagnosis. The decrease in glucose response seen after 24 hours of feed deprivation is likely due to the elevation of fatty acid concentrations in the blood.

Different antimicrobials are added in the manufacturing of dairy products such as flavored yogurts and processed cheese. Potassium Metabisulfite (PM) and Potassium Nitrite (PN) have been reported to have antimicrobial effect on pathogenic microorganisms such as Clostridium botulinum and Listeria monocytogenes. Yogurt is known for its health benefits, due to the presence of cultured bacteria. PM and PN are not commonly used in the dairy industry hence it would be interesting to study their influence in yogurt culture bacteria. The objectives of this study were: 1. to elucidate the influence of PM and PN at various concentrations, on the growth of yogurt culture and 2. to determine the possible acquisition of resistance after prior exposure to low doses of these antimicrobials. For the first objective different concentrations of PM and PN (100, 1,000, 10,000, 100,000 and 1,000,000ppm) were separately added to broth previously inoculated with Lactobacillus bulgaricus LB-12 and Streptococcus thermophilus ST-M5. Control samples did not receive any antimicrobial. Growth was determined by plating at 0, 24, 48 and 72 hours of incubation. For the second objective, treatments consisted of separately exposing cultures to 100 and 1,000ppm of both antimicrobials and after 24, 48 and 72 hours, transferring them into 10,000 and 100,000ppm, of both antimicrobials. Growth was measured at 0, 24, 48 and 72 hours of incubation. Data were analyzed using Proc Mixed and Repeated Measures model of the Statistical Analysis System SAS®. Differences of Least Square Means where used to determine significant differences. Neither PM nor PN had an antimicrobial effect on yogurt culture Lactobacillus bulgaricus LB-12 or Streptococcus thermophilus ST-M5. Both antimicrobials at 1,000,000ppm significantly increased counts of Streptococcus thermophilus ST-M5 6 log CFU/mL compared to control. Prior exposure of Streptococcus thermophilus ST-M5 to both antimicrobials at 100 and 1,000ppm for 72 hours showed resistance to 10,000 and 100,000ppm of both PM and PN with a significant increase of 6 log CFU/mL compared to control. Commercial applications of this study would be to incorporate PM and PN in yogurt manufacture for inhibition of spoilage and pathogenic bacteria to ensure good preservation of the product and improved shelf life.

The first objective of the two studies presented herein evaluated on farm sources of variation and correlated effects contributing to BRD incidence in a population of crossbred steers sent to the feedlot from 2010-2013. Analyses revealed that incidence of BRD was lowly positively correlated to birth weight (BW) and lowly negatively correlated to weaning weight (WW), hip height (HH), sire breed, site, and birth year. These results indicate that the traits analyzed herein are not precursors for BRD in the current population. However, since little is still known about the correlation between genetic predisposition to BRD and animal performance, further studies should be conducted in the future. The second study presented herein evaluated single nucleotide polymorphisms (SNP) located on previously described QTL regions of Bos Taurus Autosome 6 and Bos Taurus Autosome 20 for potential associations with growth traits, carcass traits, and incidence of BRD in crossbred steers. Growth traits analyzed included birth weight (BW), weaning weight (WW), and hip height (HH). Carcass traits evaluated included hot carcass weight (HCW), yield grade (YG), marbling score (MS), ribeye area (REA), and back fat thickness (BF). Along with growth and carcass traits, incidence of BRD was also evaluated in the current population. Genotyping analyses identified fourteen unique SNP located on BTA 6 and eleven unique SNP located on BTA 20 that were significantly (P < 0.05) associated with the aforementioned traits. However, no markers on either BTA 6 or BTA 20 were identified as significantly associated with BF. These results indicate that there may be a higher genetic predisposition to BRD than previously thought. However, before their incorporation into MAS programs, additional SNP located on BTA 6 and BTA 20 should be genotyped, along with other QTL regions spanning the genome. Additionally, a larger population of crossbred steers should be utilized to further validate the results herein.

The first objective of the current study was to evaluate genetic trends from 10 years of the American Brahman Breeders Association Carcass Evaluation Program from 2004 to 2013. Changes of performance in growth, carcass composition, and carcass quality traits were evaluated. Overall means were calculated to report the total average for each trait along with an average rate of change per year. Growth traits evaluated included feedlot entrance weight (INWT), harvest weight (HRVWT), and average daily gain (ADG). Carcass composition and quality traits evaluated included hot carcass weight (HCW), rib eye area (REA), marbling score (MARB), dressing percent (DP), quality grade (QG), yield grade (YG), and Warner-Bratzler shear force score (WBS). Trends indicated that over the 10 year period of improved sire selection, Brahman cattle began entering the feedlot lighter, exited heavier, and improved average daily gain. Furthermore, all carcass composition and quality traits showed overall improvement with the exception of shear force scores. Further investigation of shear force score showed WBS had in fact been experiencing a favorable downward trend since 2009. The second objective of this study was to evaluate SNP located on six candidate genes and their potential association with growth, carcass composition, and carcass quality traits in a population of Brahman and Brahman-influenced steers that participated in the ABBA carcass evaluation program. Traits analyzed included birth weight (BW), weaning weight (WW), hip height (HH), days on feed (DOF), and the previously mentioned feedlot and carcass traits INWT, HRVWT, ADG, HCW, REA, MARB, DP, QG, YG, and WBS. Single nucleotide polymorphisms (SNP) were chosen for analysis within six candidate genes including Thyroglobulin (TG, Adiponectin (ADIPOQ), Calpastatin (CAST), Calpain-3 (CAPN3), Insulin like growth factor-1 (IGF1), and Growth Hormone gene (GH1). Analysis revealed representation of all six candidate genes in the 41 SNP found to have 58 significant associations (p<.05) with growth and feedlot traits BW, WW, HH, INWT, HRVWT, DOF, and ADG. Furthermore, all six candidate genes were represented in the 32 SNP found to have 49 significant associations with carcass composition and quality traits HCW, REA, YG, MARB, QG, and WBS. No markers showed association with DP.

During the early existence of the science of genetics, the area of single gene effects was the more active area of interest. Throughout the initial development of this science, studies of qualitative traits provided the basis on which the later principles were founded. [...]