Two calf feeding trends are emerging in the dairy industry in the United States. Large herds often find it economical to feed pasteurized waste milk; while smaller herds are embracing technological advancements by utilizing automated calf milk feeders. Housing of calves varies depending on feeding mechanism. Calves fed using autofeeders are grouped together but large herds often find it more labor efficient to house calves individually in elevated wooden crates or polyethylene hutches. Two studies were conducted. The objective of the first field study was to evaluate the influence of diet and housing type on growth and morbidity in 84 Holstein heifer calves in a 2 by 2 factorial experimental design. Calves were housed in either polyethylene hutches or elevated wooden crates with slatted floors. Diets consisted of pasteurized waste milk or the same waste milk supplemented to provide approximately 454 g of milk replacer solids containing 25% protein and 10% fat (LOL Balancer). Calves were randomly placed in 1 of 4 treatment groups 48 h after birth and monitored until weaning (~60 d of age). Body weights and hip heights were measured at time of enrollment and weaning. Milk samples of pasteurized waste milk were obtained five times weekly to measure standard bacteriological plate count, fat, protein and total solids content. All calves were fed 3.3 L of liquid diet via bottle at 0730 and 1530 h. Calves were monitored daily for respiratory and digestive illness and treated according to established protocols. Pasteurized waste milk contained 332,171 ° 733,487 cfu/ mL, 3.51 ° 0.59% fat, 3.13 ° 0.30% protein, and 11.64 ° 1.05% total solids. Housing (P = 0.02) and diet (P = 0.01) affected weight gain, but there was no interaction. Least squares average daily gain for crate and hutches were 0.52 ° 0.024 and 0.59 ° 0.024 kg/d. Least squares average daily gain for waste milk and balancer diets were 0.52 ° 0.024 and 0.60 ° 0.024 kg/d, respectively. Housing or diet did not affect hip height growth/d (0.196 ° 0.007 cm). Health of the calves was not affected by diet or housing. Supplementing waste milk with balancer or housing calves in hutches resulted in higher weight gain. The objective of the second study was to evaluate management, and sanitation and consistency of liquid delivered to calves via automated feeders. Ten herds in Virginia and North Carolina with sophisticated (Förster-Technik, Germany) and basic (Biotic Industries Inc., TN, USA) machines completed a 60-question survey concerning calf and autofeeder management. Duplicate milk replacer samples were obtained to measure sanitation, dry matter, and temperature of milk in the autofeeder at the time of the survey. Six dairies from the original 10 were visited monthly for 3 mo for continued evaluation of sanitation, dry matter, and temperature of milk replacer from the autofeeder. Seven herds utilizing basic machines had a mean SPC of 6,925,000 ° 7,371,000 cfu/ml. The mean dry matter and temperature readings were 12.0 ° 2.1 Brix and 38.8 ° 6.7 °C, respectively. Three dairies that used sophisticated autofeeders had a mean SPC of 1,339,000 ° 2,203,000 cfu/ml. Mean dry matter and temperature readings were 10.37 ° 1.68 Brix and 38.6 ° 6.76°C, respectively. Dairies were also categorized based on management strategies. Producers that purchased autofeeders to manipulate feeding rates, refocus labor to sanitation, and care and well-being of calves, or for technological advancements were successful at rearing calves via autofeeders. Dairy producers who purchased an autofeeder to explore feeding options were not as successful because proper time and management was not dedicated to care of calves or to maintenance of the autofeeder. / Master of Science

Exposure to antibiotics has the potential to increase the incidence and proliferation of antibiotic resistance genes (ARG) in the gut and fecal microbiome. Non-saleable, antibiotic-containing milk from cows treated with antibiotics (waste milk) is commonly fed to dairy calves but the effects of ingestion of antibiotics at an early age on the gut microbiome and the development of ARG in the naive gut are not well understood. Pirlimycin, a lincosamide antibiotic acting against Gram positive bacteria through inhibiting protein synthesis by binding to the 50S ribosome, is commonly used as mastitis therapy. Lincosamides are also considered highly important in human medicine, often used against Staphylococcus aureus and Clostridium difficile infections. Emerging microbial resistance to pirlimycin is of concern for both animal and human health. The objective of this study was to determine the effect of early lincosamide antibiotic exposure on the abundance of ARG in feces of milk-fed calves. Eight female Holstein calves were blocked by age, paired by block, and randomly assigned to pasteurized whole milk (control; n = 4) or milk containing 0.2 mg/L of pirlimycin (treatment; n = 4). Calves were enrolled after receiving two colostrum feedings and were fed 5.68 L of pasteurized whole milk, treatment, or control, divided into two daily feedings, from d 1 to d 50 of age. After weaning calves were fed non-medicated starter grain ad libitum. Fecal samples were collected weekly until 85 d of age and freeze-dried. DNA was extracted using QiaAmp® Fast DNA Stool Mini Kit and qPCR was used to quantify the absolute abundance (gene copies/g of wet feces) and relative abundance (gene copies/copies of 16S rRNA genes) of erm(B), tet(O), tet(W) and 16S rRNA genes. Data was analyzed using PROC GLIMMIX in SAS. Abundance of 16S rRNA genes, tet(O) and tet(W) were not different between control and pirlimycin-fed calves nor were the relative abundance of tet(O) (mean = 0.050 tet(O) copies/16S rRNA genes) or tet(W) (0.561 tet(W) copies/16S rRNA genes). While abundance of erm(B) was higher in pirlimycin-fed calves compared to control calves (6.46 and 6.04 log gene copies/g wet feces; P = 0.04) the relative abundance of erm(B) (0.273 gene copies/16S rRNA genes) in feces of calves was not influenced by treatment. There was an effect of day (P < 0.10) for absolute abundance of tet(O), tet(W), and erm(B) indicating that the levels change with time as the fecal microbiome develops. This study suggests that feeding pirlimycin-containing non-saleable milk to growing calves may increase environmental loading of erm(B), which codes for resistance to highly important macrolide and lincosamide antibiotics. Additional research is needed on effects of feeding waste milk to calves on other fecal ARG and on the post-excretion and post-application fate of these genes. / Master of Science

The objective of this study was to determine amount and composition of waste milk (WM) generated by 13 dairy farms and to measure effectiveness of on-farm pasteurizers. Waste milk was sampled bi-weekly from three farms located in North Carolina (NC) for 28 weeks and twice from ten farms in California (CA) in June 2005 and Jan. 2006. Amount of waste milk generated ranged from 2.48 – 9.84 L/calf/d. Standard plate count (SPC) of waste milk before pasteurization averaged 17 million cfu/ml on NC farms and 1.6 million cfu/ml on CA farms. Pasteurizers failed to deactivate alkaline phosphatase in 16%, and <5% of the time in NC and CA. California WM had lower post pasteurized SPC (13,000 cfu/ml) than NC farms (430,000 cfu/ml). A feeding trial was conducted to evaluate supplementing WM with 28% protein: 20% fat milk replacer (28:20) when WM is insufficient relative to calf demands. Treatment (TRT) 1 calves received M for 28d and then 28:20 until weaning at 56d. Treatment 2 calves received 28:20 for 28d and then milk until weaning. Treatment 3 calves received 28:20 for the entire period Four periods of time were evaluated; the total period, first four weeks (P1), transition period (TP), in which calves were switching diets, and until weaning (P2). Treatment 1 ADG was higher during TP as compared to TRT 2. Results demonstrated that similar growth rates through 8 weeks of age was achieved with either combination of M and 28:20 or only 28:20 fed on an isocaloric basis. / Master of Science