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The goal of this research was to evaluate the effects of calf starter fermentation on rumen pH, metabolic adaptation of ruminal epithelia and growth of calves during the weaning transition. In study 1, calf starter consumption increased short chain fatty acid concentration in the rumen and changed expression of genes involved in ketogenesis and intracellular pH regulation but did not affect rumen pH. In study 2, decreasing dietary starch content did not increase rumen pH. However, feeding a calf starter that had the highest in situ dry matter disappearance lowered rumen pH without adversely affecting feed intake and growth of calves. These findings suggest that rumen epithelium can metabolically adapt to increased fermentation in the rumen at molecular level, and that sub-acute rumen acidosis may not adversely affect feed intake and productivity of dairy calves during the weaning transition. / Animal Science

The objective was to summarize management practices, identify factors associated with bacterial counts, and describe the variation in total solids concentrations of milk or milk replacer in automated feeders. Six dairy calf operations in Virginia and 4 in Minnesota employing 1 to 2 sophisticated automated calf feeders were visited biweekly for 26 to 28 wk. An initial management survey was conducted for each farm. Observations on facilities, calf weights and heights, blood samples to estimate serum total proteins, treatment records, digital feeding behavior records, and milk or milk replacer (MMR) samples were collected at each visit. Additional milk replacer (MR) samples were collected for 4 wk pre- and post-circuit cleaning. Samples of MMR were plated on Aerobic Plate Count (APC) and Coliform Count (CCP) Petrifilms. Total solids concentration was estimated for MR samples by refractometry. Feeding plans varied widely between farms. Estimates of calf growth were near industry standards, but the proportion of calves receiving treatment was elevated. Least squares mean APC and CCP were 5.26 and 3.01 log10 cfu/ml for Virginia and 3.80 and 0.61 log10 cfu/ml for Minnesota. Circuit cleaning (CC) caused 13 and 16% log reduction in APC and CCP. However, more frequent CC/wk increased bacteria. Mixer/heat exchanger cleanings decreased bacteria during biweekly farm visits. Chlorine bleach reduced bacteria. Use of silicone feeder hoses increased bacteria. A quadratic effect of MMR liters delivered/d was observed; liters delivered > 147 L decreased APC. Automated feeders delivered 12.26% of MR samples > 2% over and 25.71% > 2% under target solids concentration. / Master of Science

The objective of this study was to evaluate the effects of heat stress and varying levels of milk replacer on dairy calf performance. Holstein bull calves ≤ 2 d of age were randomly assigned housing, outside under a covered area, heat stress (HS), or inside a controlled environment, non-heat stress (NHS), to test for heat stress effects on growth. Calves were also assigned to one of three feeding strategies: increasing amounts of milk replacer from 1.1% body weight (BW) to 1.5% BW (INC), constant at 1.1% BW (CON), or decreasing from 1.6% BW to 1.2% BW (DEC), adjusted weekly, commencing on day 9 of feeding and ending on day 40. Milk replacer amounts were adjusted twice weekly after weighing. Calves had ad libitum access to commercial starter feed and water. Starter intake, water intake, and fecal score (1 to 4) were recorded daily. Respiration rates and rectal temperatures were recorded twice daily at 0600h and 1800h. Average daily gain was greater (P < 0.01) for NHS (0.79 ± 0.03 kg/d) compared to HS (0.66 ± 0.03 kg/d) The NHS calves consumed more starter (P < 0.01) than HS (1.77 vs 1.16 ± 0.06 kg/d. Water consumption averaged 3923 ± 105 mL/d for HS which was greater (P < 0.01) than NHS (2338 ± 105 mL/d). No significant differences were observed among the feeding treatment groups for weight gain (P = 0.73). Milk replacer levels had a significant impact (P < 0.01) on the amount of calf starter consumed with CON consuming the most (1.64 ± 0.07 kg/d), followed by INC (1.44 ± 0.07) and DEC consuming the least (1.34 ± 0.07 kg/d). Water intake was also significantly impacted by milk replacer levels (P < 0.01). Calves in the DEC group consumed the least amount of starter, and consumed more water (3657 ± 129 mL/d) than both INC calves (3119 ± 129 mL/d) and CON calves (2614 ± 129 mL/d). Overall, housing has an impact on growth in neonatal dairy calves; however, milk replacer levels did not impact growth of the calves.

The objective of the study was to investigate the effect of increased volumes of milk feeding as well as the effect different group sizes may have on the growth and health of Jersey calves. One hundred and twenty 3-day old heifer calves were randomly assigned to one of four treatment groups (30 calves each) and calves in groups one and two were assigned into four subgroups (15 calves each). Two groups received unrestricted volumes of milk (HMV), while two groups received restricted volumes of milk (RMV) during the preweaning period. The calves were weaned after 6 weeks. Feed intake, growth rates, health and cross-sucking behaviour of calves were monitored until all the calves in the trial reached at least 60 days of age. The effects of milk volume and group size on growth rates and the risks of diseases were evaluated using multiple linear- and logistic-regression models. During the milk-fed stage, the HMV calves drank 72% more milk than calves fed conventionally. Probably as a result of the much higher intake of milk, the HMV calves gained 154 g/d more weight than the RMV calves before weaning (P < 0.001), resulting in a 6.3 kg weight advantage on d 42. Birth weight of the HMV calves showed a strong linear relationship with milk intake (Pearson’s r = 0.696, P < 0.001) and preweaning ADG (Pearson’s r = 0.426, P < 0.001). Calves that were provided with more milk consumed less calf starter, reflecting effective substitution of milk with concentrate. However, after the calves were weaned, the difference in starter intakes disappeared. This resulted in no treatment differences in weight gains over the postweaning period, and on d 60 the HMV calves maintained an advantage in mean (± SD) body weight (67.6 ± 7.9 kg vs. 60.8 ± 6.6 kg for the HMV vs. RMV calves). With the exception of keratoconjunctivitis, the incidence of disease in milk-fed calves was low and did not differ between HMV and RMV treatment groups. Days of treatment for keratoconjunctivitis (birth to d 42) was significantly higher (P < 0.05) for calves in the large HMV group compared with calves in other groups. Smaller groups showed a higher incidence of diarrhoea during the preweaning period (OR = 3.23; P < 0.01). Over the whole trial period, the gain-to-feed ratio of HMV calves was 9.6% better than calves receiving restricted milk volumes. However, the cost per kg body mass gain was 12% higher for HMV calves. Cross-sucking observations showed that the incidence in the preweaning period differed greatly between the groups (1.7% vs. 75.5% for HMV vs. RMV groups; P < 0.001). During the last 10 days of the trial, this difference decreased, but was still significant (10.0% vs. 19.1% for HMV vs. RMV groups; P < 0.001). The conclusion was that the feeding of high volumes of milk to dairy calves will have a significant positive effect on growth rates, without compromising their health or the intake of solid food after weaning. Additionally it allows calves to be housed in groups with less problems of cross-sucking. Copyright / Dissertation (MSc)--University of Pretoria, 2008. / Production Animal Studies / unrestricted

Mortality and decreased weight gain resulting from infection and disease in dairy calves is a problem within the dairy industry. Colostrum is the sole source of maternal immunity for the calf, having a substantial impact on health and survival. To date, colostrum quality is determined by concentration of antibodies. Colostrum also contains proteins and cells, which may enhance immune development in the neonate. Our goals were to determine the impact of colostral immune cells on (1) immune status during the first month of life and (2) immune development over time. To determine the impact of adoptively transferred colostral immune cells, calves were fed either whole colostrum (WC) or cell-free colostrum (CFC) at birth. During the first month of life, calves fed CFC had decreased numbers of CD4+ T cells when compared to WC-fed calves. However, CFC-fed calves had a greater percentage of monocytes during the first month of life. To determine the influence of colostral immune cells on immune development, cellular blood parameters were measured in response to two series of vaccinations (A and B). After vaccination series A, CFC-fed calves had decreased numbers of B cells when compared to WC-fed calves. After vaccination series B, CFC-fed calves had decreased levels of interleukin-2 gene expression and numbers of CD4+ and gamma delta T cells when compared to WC-fed calves. This study demonstrates that colostral immune cells impact immune status and development in dairy calves. / Master of Science

This study investigated the microbial colonization and maternal influences on the neonatal calf gut microbiome. Microbiome samples were collected from dams (n = 6) and calves (n = 6) using sterile flocked swabs. The vaginal, oral, and fecal bacterial communities were examined from the dam and the fecal community of calves was examined from birth to 60 d of age. Microbial communities varied by anatomical location and age of the calf. Metagenomic analysis 16s ribosomal DNA revealed ten phyla associated with microbiomes of the dam and the same ten phyla associated with calf feces at various time points: Bacteroidetes, Firmicutes, Proteobacteria, Actinobacteria, Cyanobacteria, Verrucomicrobia, Spirochaetes, Tenericutes, Fibrobacteres, and Lentisphaerae. Overall, the calf meconium and fecal microbiome is influenced by a combination of the maternal vagina, oral, and fecal microbiomes. Further studies will be needed to identify the transference mechanisms of maternal microbes to offspring and the associated host-microbial interactions. / Master of Science in Life Sciences / This study investigated the microbial colonization and maternal influences on the neonatal calf gut microbiome. Microbiome samples were collected from dams (n = 6) and calves (n = 6) using sterile flocked swabs. The vaginal, oral, and fecal bacterial communities were examined from the dam and the fecal community of calves was examined from birth to 60 d of age. Microbial communities varied by anatomical location and age of the calf. Metagenomic analysis 16s ribosomal DNA revealed ten phyla associated with microbiomes of the dam and the same ten phyla associated with calf feces at various time points: Bacteroidetes, Firmicutes, Proteobacteria, Actinobacteria, Cyanobacteria, Verrucomicrobia, Spirochaetes, Tenericutes, Fibrobacteres, and Lentisphaerae. Overall, the calf meconium and fecal microbiome is influenced by a combination of the maternal vagina, oral, and fecal microbiomes. Further studies will be needed to identify the transference mechanisms of maternal microbes to offspring and the associated host-microbial interactions.

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Calves infected with Babesia bovis or Babesia bigemina between 3 and 9 months of age can develop immunity without showing overt clinical signs. This transient immunity is not dependent on maternal immunity. After 9 months of age, they are fully susceptible to challenge. Dairy calves between 2 and 3 months of age were vaccinated with B. bigemina and B. bovis live frozen vaccines (Onderstepoort Biological Products®). Two months after vaccination, 90% of calves were serologically positive on IFA test to B. bigemina, and 70% were serologically positive to B. bovis. At this age, only 17% of the control group had seroconverted to B. bigemina and none of the calves had seroconverted to B. bovis. All experimental calves maintained positive serological status to both B. bovis</i. and B. bigemina for at least 5 months after vaccination. It is sound practice to vaccinate dairy calves against babesiosis at 2–3 months of age. Endemic stability is achieved before the period of natural resistance wanes. Copyright / Dissertation (MSc)--University of Pretoria, 2011. / Veterinary Tropical Diseases / unrestricted

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