Serum Amyloid A and the Acute Phase Response in Bovine Pneumonic Pasteurellosis

The acute phase response is a cascade of events which occurs immediately after an injury or infection. It is a non-specific, non-immune defence mechanism which consists of a local and a systemic response that vary from species to species. The aim of the work described here was to increase our understanding of the systemic acute phase response (APR) in cattle. An established experimental model for bovine pneumonic pasteurellosis in which calves were inoculated intra-tracheally with P. haemolytica A1 or with lipopolysaccharide (LPS) extracted from the organism was used in these studies of the APR. Serum amyloid A (SAA), a major acute phase protein in cattle was monitored in an indirect enzyme-linked immunosorbent assay developed using a commercially available rabbit anti-human SAA antibody. The assay was standardized using a pool of acute phase bovine serum which was quantified with purified bovine SAA (b-SAA) prepared by hydrophobic interaction chromatography and gel filtration. This allowed b-SAA concentrations in serum to be estimated in SI units with the detection limit of the assay being 3mug ml-1. The APR induced with P. haemolytica was characterised within 24 hours by the clinical signs of fever, anorexia, tachypnoea and a dull demeanour and was associated with a marked neutrophilic leukocytosis, hypoferraemia and hypozincaemia. During the same period the endocrine system was affected with an elevation of cortisol and a reduction of thyroxine being detected. The acute phase protein response was manifested by an increase in both SAA and haptoglobin (Hp) concentrations within 24 hours of inoculation and the concentration of both proteins reached a peak at 48 hours post inoculation. However, in studies comparing the effect of different isolates of P. haemolytica, on the acute phase protein response only the SAA levels correlated with the pathogenicity of the infectious organism. Frequent sampling during the initial phase of the APR indicated an earlier rise in SAA compared to Hp. In addition, a rise in fibrinogen was found at 24 hours, but there were no clear increases in ceruloplasmin or copper concentrations. Most results from a comprehensive biochemical analysis of sera from infected animals were within the normal range, but plasma concentration of bilirubin was increased and glutamate dehydrogenase activity was decreased. Animals treated with P. haemolytica LPS intra-venously demonstrated an APR which was comparable to that observed when the whole organism was challenged intra-tracheally. In studies to determine the role of bovine cytokines in the infection, both P. haemolytica and LPS elicited a tumour necrosis factor (TNFalpha) response which peaked 2 hours after challenge and returned to non- detectable levels after a further 4 hours. Unsuccessful attempts were made to measure the plasma concentration of Interleukin 1 and Interleukin 6. It is concluded that the APR in bovine pneumonic pasteurellosis is characterised by clinical changes and a wide array of pathophysiological alterations which include leukocytosis, mineral redistribution, endocrine and metabolic changes, and an acute phase protein response. The APR varied with the isolate of P. haemolytica and appears to correlate with the pathogenicity of the organism. Furthermore, the marked response in TNFalpha concentrations implicates this cytokine as a major mediator of the APR in cattle

Grazing Behaviour of Dairy Cows When Grazing Forage Rape in a Pasture-Based Automatic Milking System

Forage rape (Brassica napus L.) is a high producing, high nutritive value forage that has been successfully introduced as a grazable forage in conventional, intensified pasture-based dairy systems to fill autumn-winter feed gaps (Garcia et al. 2008). However, incorporation of forage rape as a grazing forage option for automatic milking systems (AMS), in which cows enter and exit grazing areas voluntarily, has not been investigated yet. We conducted an observational study to investigate the suitability of using forage rape in AMS and gain understanding of cow’s foraging behaviour when grazing this forage. The outcomes of this piece of work will help to determine management guidelines regarding incorporation of the crop into voluntary cow traffic systems

Increasing Feed Conversion Efficiency in Automatic Milking Systems: The Impact of Grain-Based Concentrate Allocation and Kikuyu (\u3cem\u3ePennisetum clandestinum\u3c/em\u3e) Pasture State on Milk Production

Pasture is typically offered to dairy cows in three allocations in pasture-based automatic milking systems (AMS). However, due to voluntary cow movement and distribution of milkings, some dairy cows access fresh pasture and other cows access depleted (stale) pasture. The first cows moving to an allocation of fresh pasture are offered ad-libitum, high quality pasture as opposed to cows arriving to the same allocation during the middle or end of the day accessing poorer quality, high fibre (neutral detergent fibre, NDF) pasture. In addition, grain-based concentrate (GBC) is allocated independently to this pasture state. The ability to increase feed conversion efficiency and AMS herd milk production by targetedGBC supplementation to cows accessing differing pasture states is unknown. Therefore, the aim of the current experiment was to determine the impact of pasture state and GBC allocation on dairy cow milk production

Increasing Feed Conversion Efficiency in Automatic Milking Systems: The Impact of Grain-Based Concentrate Allocation and Kikuyu (\u3cem\u3ePennisetum clandestinum\u3c/em\u3e) Pasture State on Kikuyu Pasture Digestibility

Automatic milking system (AMS) farms, rely upon voluntary cow traffic (the voluntary movement of cattle around a farm) for milk harvesting and feed consumption. Dairy cows on a pasture-based AMS farm typically move from depleted to fresh allocations of pasture in small groups, or individually, at differing times. The first cows moving to an allocation of fresh pasture get access to rapidly fermentable, ad libitum, high quality pasture in contrast to those cows accessing the same allocation towards the end of the access period. At the same time, grain-based concentrate (GBC) is allocated independent of the pasture state that cows access. Inclusion of a high level of GBC in the diet with high or low nutritive value forage, or variable states of forage, may create dramatic variations in rumen fluid pH, which may induce subacute ruminal acidosis (Bramley 2004), reduce feed conversion efficiency and negatively impact animal health. The aim of the current study was to determine the impact of pasture state and GBC allocation on the digestibility of kikuyu pasture