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Limited internal (unpublished) research has shown that GHRH does have positive clinical outcomes in beef cattle and additional research is needed to demonstrate the benefits observed in other species. The VGX Animal Health growth hormone releasing hormone (GHRH) plasmid has demonstrated efficacy in pre-clinical trials in cattle. A single treatment in the third trimester of pregnancy was given to 32 of 52 heifers, while 20 heifers remained as controls. Body condition scores of treated animals significantly better than controls (3.55 vs. 3.35, respectively, at 60-80 days in milk (DIM), P < 0.0001). Involuntary culling of treated animals was reduced by 40%. Mortality of heifers was significantly decreased (3% vs. 20% in controls, P < 0.003), while calves from treated heifers were 25% less likely to die at birth (18.8% vs. 25%), and from birth-to-260 days (0% vs. 20%). Overall calf mortality was reduced by 47%, P < 0.02. Calves from treated heifers were heavier at 260 days post-natal (P < 0.05). Milk production was increased by 10 to 22% (27.45 ± 0.89 kg/d vs. 23.2 ± 1 kg/d) in GHRH-treated animals compared to non-treated controls up to 300 DIM. The immune enhancing effects were also studied. At 18 days post treatment, the GHRH-treated animals had increased numbers of CD2+ αß T-cells (P <0.004), CD25+CD4+ cells (P <0.0007), and CD4+CD45R+ cells (P < 0.016) compared to controls. These increases were maintained long term after treatment and correlated with plasmid expression. At 300 days post treatment CD45R+/ CD45RO- naive lymphocytes were significantly increased in frequency (P < 0.05). Natural killer lymphocytes (CD3-CD2+) were also increased. Based on this study in dairy cattle and the results obtained in our swine studies we predict that we will see similar results in our planned beef cattle studies. |
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