Effects of age and plane of nutrition on immune responsiveness of neonatal dairy calves

The neonatal calf has a heightened susceptibility to infectious disease. Traditional calf-rearing programs limit nutrient intake from milk or milk replacer during the first few weeks of life to promote dry-feed intake and early weaning. Dramatic improvements in growth performance achieved by feeding increased amounts of milk replacer with more protein is hypothesized to be associated with enhanced immune function and an increased resistance of the calf to infectious disease. Objectives of this dissertation were to characterize more extensively immune responses of the neonatal calf and to determine if intensified nutrition enhances immune function of milk replacer-fed calves. T-cell subsets from 1-wk-old calves showed decreased proliferative activity, a delayed increase in CD25 expression, and no demonstrable increase in CD44 expression or decrease in CD62L expression when compared with the mitogen-induced responsiveness of cells from steers. Mitogen-induced proliferation and expression of activation antigens by T cells from 8-wk-old, standard-fed calves, however, were similar to responses of cells from steers, indicating that T cell function during the neonatal period matures rapidly. Intensified nutrition during the neonatal period was associated with alterations in the responsiveness of T cell subsets to mitogenic stimulation, characterized by decreased proliferation, decreased expression of activation antigens (i.e., CD25 and CD44), decreased interferon-gamma secretion, and increased nitric oxide production. These results suggest that animal maturity and neonatal nutrition influence functional activities of T lymphocyte subsets essential in the development of cell-mediated immunity. Feeding a milk replacer (30% crude protein/20% fat) at different rates to achieve no growth, low growth, and high growth did not affect antigen-specific recall responses of cells from vaccinated calves. These results suggest protein-energy malnutrition in the absence of weight loss does not affect adaptive immune responses of calves. Cells from high-growth rate calves had increased nitric oxide production and decreased viability. These alterations in cell function may have deleterious effects on resistance to infectious disease

The use of vitamin D3 and its metabolites to improve beef tenderness

Our previous work has shown that feeding 5 million international units (IU) of vitamin D3 to beef steers can produce strip loin and top round steaks with greater tenderness. Our current experiment was designed to determine whether feeding two metabolites of vitamin D3, 25-hydroxyvitamin D3, and 1,25-dihydroxyvitamin D3, improves tenderness of strip loin, top round, and top blade steaks more effectively than does supplemental vitamin D3 without leaving a substantial amount of residual vitamin D3 and its metabolites in muscle. Thirty-three continental crossbred steers were allotted randomly to one of four treatment groups. The first group was fed a placebo, the second group received 5 million IU of vitamin D3, the third group received one dose of 125 mg of 25-hydroxyvitamin D3, and the fourth group received one dose of 500 [Mu]g of 1,25-dihydroxyvitamin D3. Blood samples were collected before treatment and at time of slaughter. Steaks from three different muscles were collected from each animal and aged for 8, 14, and 21 days. All steaks were assayed for tenderness by Warner-Bratzler shear force determination and by Western blot analysis. Concentrations of vitamin D3 in plasma were higher in vitamin D3-treated cattle (p\u3c0.0001). Concentrations of plasma 25-hydroxyvitaniin D3 were increased in 25-hydroxyvitamin D3-treated cattle but were not as high as those in vitamin D3-treated cattle (p\u3c0.0001). 1,25- Dihydroxyvitamin D3 concentrations were higher in 1,25-dihydroxyvitamin D3-treated animals when compared with all treatments (p\u3c0.0001). Supplementing steers with vitamin D3 increased the concentration of vitamin D3 and 25-hydroxyvitamin D3 in the meat of all muscles sampled (p\u3c0.0001). Supplementing steers with 25-hydroxyvitamin D3 increased the concentration of 25-hydroxyvitamin D3 in meat, but to an amount less than half that of cattle treated with vitamin D3. Warner-Bratzler shear force analysis showed that feeding 1,25-dihydroxyvitamin D3 did not significantly lower shear force values, but supplemental vitamin D3 and 25-hydroxyvitamin D3 produced steaks with lower shear force values (p\u3c0.06). Analysis of Western blots showed that longissimus lumborum and semimembranous steaks from cattle fed supplemental vitamin D3 and 25-hydroxyvitamin D3 (but not steaks from cattle fed 1,25-dihydroxyvitamin D3), had greater proteolysis of troponin T to a 30-kDa component

Plane of Nutrition Affects Plasma Ghrelin Concentrations in Neonatal Calves

Investigating different planes of nutrition on appetiterelated hormones could provide knowledge into the role of these hormones on growth performance in neonatal calves. The objective of the current study was to investigate the effects of feeding rates on ghrelin in plasma from preruminant calves. Treatments (n = 8 per treatment) were designed to achieve three targeted daily rates of gain (No Growth = 0.0 kg, Low Growth = 0.55 kg, or High Growth = 1.2 kg) in live weight over a 7-wk period. All calves were fed a 30% crude protein, 20% fat, all-milk protein milk replacer reconstituted to 14% dry matter. Daily growth rates for No, Low, and High Growth calves were different (P\u3c 0.001) throughout the experimental period and averaged 0.11 ± 0.02 kg, 0.58 ± 0.02 and 1.16 ± 0.04 kg, respectively. Fasting ghrelin active concentration was higher (P \u3c 0.0001) in the No Growth calves over the 7-wk period in comparison to the Low and High growth calves. Circulating concentrations of ghrelin in neonates fed different planes are similar to responses of adult humans to feed intake. These results indicate an inverse relationship of ghrelin active concentration with respect to plane of nutrition and growth rate in neonates

High-Growth Rate Fails to Enhance Adaptive Immune Responses in Neonatal Calves and Decreases Immune Cell Viability

The objective of the current study was to investigate the effects of different feeding rates achieving three targeted growth rates (No Growth, Low Growth, and High Growth) on adaptive immune responses of neonatal calves vaccinated with Mycobacterium bovis bacillus Calmette-Guerin (BCG) and ovalbumin (OVA) 3 wks after initiation of dietary treatments. The daily growth rates for No-, Low-, and High-growth calves were different throughout the experimental period and averaged 0.11 ± 0.02 kg, 0.58 ± .02, and 1.16 ± 0.04 kg, respectively. Adaptive immune responses generally were not affected by growth rate. Ovalbumin-specific IgG1 and IgG2 concentrations after vaccination were not affected by growth rate. Interferon (IFN)-γ and nitric oxide (NO) secretion by PPD-stimulated mononuclear leukocytes (MNL) also were not affected by growth rate. Antigen (i.e., PPD)-elicited delayed-type hypersensitivity in No-growth calves was greater than Lowgrowth but similar to High-growth calves. Viability of MNL, CD4+, CD8+, and γδTCR+ cells in stimulated and non-stimulated cultures from High-growth calves was substantially lower compared with No- and Low-growth calves. These results suggest protein-energy malnutrition (PEM) in the absence of weight loss does not affect negatively adaptive immune responses of calves and that increasing growth rate or plane of nutrition above maintenance requirements does not benefit adaptive immune responses. High rates of growth, however, may affect negatively immune cell viability, with potentially deleterious effects on the calf’s resistance to infectious disease

Effects of Intensified Nutrition on Immune Cell Populations in Milk Replacer-Fed Neonatal Calves

Results from the present study confirm the growthpromoting benefits of feeding an intensified milk replacer to dairy calves. Effects of the elevated plane of nutrition on immune variables examined in the present study were minimal. The number of circulating leukocytes and the composition of the PBMC population as well as this population’s general responsiveness and capacity to secrete IgM were not affected by diet. Relative to responses of calves fed the traditional MR, calves fed the intensified MR demonstrated reduced IFN-γ responses and elevated NO responses during the latter stages of the study. Aberrant NO production, however, can result in undesirable host tissue destruction

Antigen-Specific B Cell Responses of Vaccinated, Neonatal Calves

The immune response of newborn calves to early vaccination is often variable and frequently characterized by marginal or nonexistent antibody responses. The B cell subpopulation of immune cells is pivotal in the production of antibody and has not been characterized completely in the newborn calf. Results from this research describe the composition and antigen-specific responses of B cell populations in preruminant calves vaccinated at an early age. Although preliminary, these data indicate that the responsiveness of B cell population in young calves is dependent on the nature of the vaccine and less on animal maturity. This research provides important new information regarding the immune responsiveness of the neonatal calf to vaccination

The use of vitamin D3 and its metabolites to improve beef tenderness

Three experiments were conducted to determine whether feeding 25-hydroxyvitamin D3 (25-OH D3) or 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) improves the tenderness of longissimus dorsi (LD), semimembranosus (SM), and infraspinatus (IF) muscles similar to supplemental vitamin D3 without leaving residual vitamin D3 and its metabolites in muscle. In the first two experiments, 24 crossbred steers were used to determine the effects of different oral amounts of 1,25-(OH)2 D3 (Exp. 1; n = 12) and 25-OH D3 (Exp. 2; n = 12) on plasma Ca2+concentrations. In the third experiment, crossbred steers were allotted randomly to one of four treatments: 1) control placebo (n = 7); 2) 5 × 106IU of vitamin D3/d (n = 9) for 9 d and harvested 2 d after last treatment; 3) single, 125-mg dose of 25-OH D3 (n = 8) 4 d before harvest; or 4) single, 500-μg dose of 1,25-(OH)2 D3 (n = 9) 3 d before harvest. The LD and SM steaks from each animal were aged for 8, 14, or 21 d, whereas steaks from the IF were aged for 14 or 21 d. All steaks were analyzed for tenderness by Warner-Bratzler shear force and for troponin-T degradation by Western blot analysis. Supplementing steers with vitamin D3 increased (P \u3c 0.01) the concentration of vitamin D3 and 25-OH D3 in all muscles sampled. Feeding steers 25-OH D3 increased (P \u3c 0.05) the concentration of 25-OH D3 in meat, but to an amount less than half that of cattle treated with vitamin D3. Supplemental 1,25-(OH)2 D3 did not affect (P \u3c 0.10) shear force values; however, there was a trend (P \u3c 0.10) for supplemental vitamin D3 and 25-OH D3 to produce LD steaks with lower shear values after 8 and 14 d of aging, and lower (P \u3c 0.10) shear force values for the SM aged for 21 d. Analysis of Western blots indicated that LD steaks from cattle supplemented with vitamin D3 and 25-OH D3 had greater (P \u3c 0.05) troponin-T degradation. Antemortem supplementation of 25-OH D3 seems to increase postmortem proteolysis and tenderness in the LD and SM without depositing large concentrations of residual vitamin D3 and its metabolite 25-OH D3

Use of Vitamin D3 and its Metabolites to Improve Beef Tenderness

Our previous work has shown that feeding 5 million international units (IU) of vitamin D3 to beef steers can produce tender strip loin and top round steaks. Our current experiment was designed to determine whether feeding two metabolites of vitamin D3, 25- hydroxyvitamin D3, and 1,25-dihysroxyvitamin D3, produces tender strip loin, top round, and top blade steaks more effectively than does supplemental vitamin D3 without leaving a substantial amount of residual vitamin D3 in muscle. Thirty-three continental crossbred steers were randomly allotted to one of four treatment groups. The first group was fed a placebo. The second group received 5 million IU of vitamin D3 each day for nine days and was slaughtered two days later. The third group received one dose of 125 mg of 25-hydroxyvitamin D3 four days before harvest, and the fourth group received one dose of 500 mg of 1,25- dihydroxyvitamin D3 three days before harvest. Blood samples were collected before treatment and at the time of slaughter for subsequent analysis of calcium, vitamin D3, 25-hydroxyvitamin D3, and 1,25-dihydroxyvitamin D3 concentrations in plasma. Steaks from the longissimus lumborum (strip loin) and semimembranous (top round) muscles were collected from each animal and aged for 8, 14, and 21 days, and steaks from the infraspinatus were collected and aged for 14 and 21 days. All steaks were analyzed for tenderness by Warner-Bratzler shear force determination. Concentrations of vitamin D3 in plasma were higher in vitamin D3- treated cattle (P \u3c 0.0001). Concentrations of plasma 25-hydroxyvitamin D3 were increased in 25- hydroxyvitamin D3-treated cattle, but not as high as vitamin D3-treated cattle (P \u3c 0.0001). 1,25- Dihydroxyvitamin D3 concentrations were higher in 1,25-dihydroxyvitamin D3-treated animals compared with all treatments (P \u3c 0.0001). Supplementing steers with vitamin D3 increased the concentration of vitamin D3 and 25-hydroxyvitamin D3 in the meat of all muscles sampled (P \u3c 0.0001). Supplementing steers with 25-hydroxyvitamin D3 increased the concentration of 25-hydroxyvitamin D3 in meat, but to an amount less than half that of cattle treated with vitamin D3. Warner-Bratzler shear force analysis showed that feeding 1,25- dihydroxyvitamin D3 did not significantly lower shear force values, but supplemental vitamin D3 and 25-hydroxyvitamin D3 produced longissimus lumborum and semimembranous steaks with lower shear force values (P \u3c 0.06). Analysis of Western blots showed that longissimus lumborum and semimembranous steaks from cattle fed supplemental vitamin D3 and 25-hydroxyvitamin D3 (but not steaks from cattle fed 1,25- dihydroxyvitamin D3), had greater proteolysis of troponin T to a 30 kDa component

Effects of Environmental Cold on the Preruminant Calf

This study examined effects of sustained environmental cold on growth and health of dairy calves. Functional measures of energy metabolism, fat-soluble vitamin and mineral status, and immune competency were also evaluated. Newborn calves were assigned to warm or cold environments for 7wk. Cold environment temperature were maintained as close to 2°C as possible. Frequent wetting of the environment and calves augmented effects of the cold. The warm environment was maintained as close to 15°C as possible and humidity was not manipulated. Preventative medications or vaccinations were not administered. All calves were fed a non-medicated MR (20% CP and 20% fat fed at .45 kg/d) and non-medicated starter ad libitum. Cold environment averaged 12 o C lower than warm environment during the study period. Humidity averaged 10% higher in the cold environment. Respiratory health of the warm environment calves was moderately better than that of cold environment calves. Scour scores were unaffected by cold exposure. Growth rate was unaffected by environmental temperature; however, cold environment calves consumed more starter from wk 5 to 7. Blood glucose concentrations were lower and NEFA concentrations were higher in cold environment calves, indicative of a state of mild negative energy balance. Serum cytokine and fat-soluble vitamin concentrations, and antibody responses to vaccination were not impacted by sustained exposure to cold

Nutritional Modulation of the Proliferation and Activation of Blood Lymphocyte Subsets from Milk Replacer-Fed Calves

Feeding greater quantities of protein and energy to neonatal calves was associated with a reduction in proliferative responses of T lymphocyte subsets to in vitro polyclonal stimulation. Feeding an intensified diet was also associated with altered in vitro expression of activation molecules, CD25, CD44, and CD62L. These data suggest that plane of nutrition during the neonatal period influences lymphocyte-activities essential for the development of a normal immune response