Immunological effects of pre-weaning plane of nutrition and yeast fermentation products on respiratory disease in dairy calves

Respiratory disease continues to be responsible for the majority of morbidity and mortality in cattle. Explanations for this are many; however some influences may include early-life nutrition, stress and other immune-compromising factors. In addition, routine antibiotic usage is being increasingly scrutinized. For this reason, both improved management practices and alternative therapies are significant. Early-life nutrition can influence productivity later in life; therefore, potential improvement of disease resistance during the pre-weaning period may be possible. Natural immune-enhancing products are also proving to be beneficial. Yeast products, specifically Saccharomyces cerevisiae and its derivatives have been shown to enhance immune variables. Bovine respiratory disease complex (BRDC) includes viral and bacterial pathogens; two specific pathogens include BHV-1 and M. haemolytica. A sensible disease model includes both a viral and bacterial component to emulate a BRDC infection. Limited data are available in combined viral-bacterial challenges; therefore, multiple doses of M. haemolytica were utilized. This challenge model aimed to induce morbidity but not induce mortality. In the first study, the objectives were to determine if pre-weaning plane of milk replacer nutrition influenced health and performance of high-risk Holstein bull calves. Calves were fed either a high (HPN; 830g DM/d of milk replacer during the first 10 d and 1080g from 11d until weaning) or a low plane of milk replacer nutrition (LPN; 445g DM/d of milk replacer until weaning) through weaning. Calves fed the HPN performed better than LPN calves in the first 25 d both in ADG and G:F as well as having greater final body weights. However, calves on the HPN had greater incidence of bloat and scouring but there was no difference in antibiotic treatment frequency. The results of this study suggest risk for gastrointestinal issues is greater in HPN calves, but performance is improved. In the second study, the effect of plane of milk replacer nutrition and M. haemolytica (MH) dose were studied in Holstein calves during a viral-bacterial respiratory challenge. Calves were challenged with 1.5 x 108 PFU/mL/nostril of bovine herpesvirus-1 (BHV-1) and with either 106, 107, or 108 CFU of MH 3 d later. Four LPN calves either died or were euthanized soon after the 144 h observation period, while all HPN calves survived the entire observation period. Calves previously fed a LPN had greater plasma haptoglobin and neutrophil concentrations as well as greater rectal temperature during the BHV-1 challenge. Haptoglobin and neutrophil concentrations as well as inflammatory cytokines were greatest in calves receiving the highest MH dose at various time points following the MH challenge. The BHV-1 neutralizing antibody titer dilution concentrations were similar between treatments immediately before the BHV-1 challenge; however, 9 d after the challenge the HPN calves had greater antibody titers compared to LPN calves. These data demonstrate that greater doses of MH increase the acute inflammatory response and prolong inflammation and that calves previously fed a LPN responded more severely to the combined viral-bacterial respiratory challenge.
The second study also investigated metabolic responses to a combined viral-bacterial respiratory challenge. Calves previously fed a HPN were heavier than LPN calves; however no difference in ADG or starter intake per kg BW0.75. Serum glucose concentrations were greater throughout the challenge in HPN calves. Following the MH challenge, LPN calves had numerically greater serum NEFA and serum urea nitrogen concentrations. Further, calves receiving 108 MH had the greatest NEFA concentrations. Calves fed a LPN during pre-weaning appeared respond more severely by evidence of reduced glucose concentrations and increased NEFA concentrations suggesting intensified immune cell energy requirements and a more severe infection. Calves fed a LPN during pre-weaning may experience greater disease during a respiratory challenge. In the third study, the effects of a Saccharomyces cerevisiae fermentation product, NutriTek (Diamond V, Cedar Rapids, IA), on leukocyte functionality and ex vivo cytokine production during a dexamethasone (DEX) challenge was studied. Holstein steers were supplemented with 0, 20, 40, or 60 g/head/d of NutriTek. Dexamethasone was administered via jugular catheter at 0.1 mg/kg BW at 0, 6, and 12 h. Total leukocytes counts and neutrophil concentrations increased with NutriTek dose. NutriTek did not affect neutrophil L-selectin concentration. Phagocytosis and oxidative burst function recovered better in neutrophils and monocytes with increasing NutriTek dose. Overall, NutriTek supplementation influenced peripheral neutrophil concentrations and may have increased recovery of neutrophil and monocyte function. In the fourth study the effects of a Saccharomyces cerevisiae fermentation product, NutriTek (Diamond V, Cedar Rapids, IA), fed to Holstein steers during a viral-bacterial respiratory challenge was investigated. Holstein steers were supplemented with 0, 20, 40, or 60 g/head/d of NutriTek. All calves were challenged with 1.5x108 PFU/mL/nostril of bovine herpesvirus-1 and with 106 CFU of M. haemolytica (MH) intratracheally 3 d later. NutriTek did not affect rectal temperature or total leukocytes counts and peripheral neutrophils. However, there was evidence for acute effects of NutriTek as lymphocyte concentrations were different among treatments. Inflammatory markers, including serum haptoglobin and ex vivo TNF-α production were not affected. These results indicate that NutriTek may influence some acute leukocyte responses during a viral-bacterial respiratory challenge, but did not have strong influences on measures of inflammation or disease. Overall, these data support there are differences in inflammatory and metabolic responses in calves fed different planes of nutrition during respiratory disease. Calves fed greater planes of nutrition may benefit during disease. Further, Saccharomyces cerevisiae fermentation product, NutriTek (Diamond V, Cedar Rapids, IA) may influence some leukocyte populations and function. However, these data cannot conclude significant immunological effects from this product.