Publications (122) View all
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Article: Nitrogen pollution by dairy cows and its mitigation by dietary manipulation
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ABSTRACT: One of the major contributions to atmospheric pollution comes from nitrogen (N) derived from cattle and especially dairy cows. Although most estimates of ammonia volitilization are based on total N excretion, it has been repeatedly shown that urinary N is a much more important source of pollution than faecal N, specially under grazing conditions. A model was developed to predict the amount and form of N excreted under different production systems. Analysis of N pollution was based on data collected from Holstein/Friesian cows fed 30 different diet types consisting of 10 grass silages and 6 concentrates. While there was a strong correlation between N intake and N output in general, urinary N was exponentially correlated with N intake and the model predicted about 80% loss of N in urine for levels of N consumption above 500 g N/d. On the other hand, outputs of faecal and milk N increased by less than 20% per unit increase in N intake. Model predictions also agreed well with published data and provided reasonable estimates of the form in which N was excreted. Concentrate composition with respect to energy type and its degradation and protein degradability and silage type had significant effects on the amount and form of N excreted. It is concluded that N pollution may be ameliorated by using grass grown with moderate fertiliser application, and maize-based energy supplements, formulated to provide low degradable protein and with N intakes of less than 400 g/d for average yielding cows.Nutrient Cycling in Agroecosystems 04/2012; 60(1):275-285. · 1.79 Impact Factor -
Article: Adding straw to a total mixed ration and the method of straw inclusion affects production and eating behaviour of lactating dairy cows
Advances in Animal Biosciences. 03/2010; 1(01):95 - 95. -
Article: Gaining from Improved Dairy Cow Nutrition: Economic, environmental and animal health benefits
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ABSTRACT: A majority of UK dairy herds have the potential to increase profitability by improving the ration of their cows. This paper reports that gains averaging around £100 per cow have been made within one year of adopting the Keenan Hi-Fibre ration by 239 UK herds in 2006 and 2007. Larger gains have been made by herds in France. The key performance indicator underlying these gains is Feed Conversion Efficiency, whereby the same, or even a smaller amount of Dry Matter Intake generates higher yields per cow. Importantly, the gains are associated with large improvements in animal health and reductions in greenhouse gases per litre of milk produced.Agricultural Economics Society, 83rd Annual Conference, March 30-April 1, 2009, Dublin, Ireland. 01/2009; -
Article: The impact of controlled nutrition during the dry period on dairy cow health, fertility and performance.
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ABSTRACT: Average dairy herd fertility is declining, with more serves per successful conception, extended calving intervals and increased culling due to failure to rebreed, all adding significant costs to milk production. Genetics, management and nutrition have all contributed to this decline in fertility; the paper focuses primarily on nutritional issues. The extent of body condition loss after calving and its possible impact on fertility is considered, with evidence that this phenomenon is common in many herds irrespective of average milk yields. Body tissue mobilisation after calving increases the flux of non-esterified fatty acids to the liver and pathways of fatty acid metabolism are considered. Particular attention is given to the effects of high plasma non-esterified fatty acid levels on fat accumulation in liver cells and possible impacts on nitrogen and glucose metabolism. Current nutritional practices with early lactation cows which aim to stimulate milk yield and peak milk production but have been shown to exacerbate body condition loss, are reviewed. The paper also considers cow health issues during the peri-parturient period and how these may affect milk yield and fertility. It is concluded that current feeding practices for dry cows, with the provision of increasing amounts of the lactation ration during the Close-up period to accustom the rumen microbes and offset the expected reduction in feed intake as pregnancy reaches term, have largely failed to overcome peri-parturient health problems, excessive body condition loss after calving or declining fertility. From an examination of the energy and protein requirements of dry cows, it is suggested that current Close-up feeding practices can lead to luxury intakes of nutrients that can increase fat deposition in the viscera and the liver. Under such conditions, metabolism of nutrients by the cow may be compromised. In contrast, limited feeding throughout the whole dry period has been shown to prevent many of the problems which can affect peri-parturient cows. A new feeding strategy based on a low energy: high fibre ration (9 MJ metabolisable energy and 130 g crude protein/kg ration dry matter) containing high levels of chopped straw and offered ad libitum as a total mixed ration throughout the whole dry period is proposed. The performance of 32 dairy farms in France where this strategy has been adopted for at least 3 years is provided, with positive outcomes now being obtained by UK and Irish dairy farmers. Independent US research evidence has confirmed some of these benefits whilst limited data on cow fertility is presented. It is hypothesised that luxury feeding during the dry period can cause cows to become insulin resistant leading to an increased risk of type II diabetes. Such cows are likely to have poorer fertility whilst possible mechanisms which increase the risk of peri-parturient health problems are discussed. Further research to understand the mechanisms of these effects is required and is currently ongoing. However the magnitude of the effects noted on an increasing number of dairy farms suggests this approach to feeding the dry cow is capable of bringing real benefits to many dairy herds in terms of fewer health problems, reduced body condition loss and improved fertility.Animal Reproduction Science 01/2007; 96(3-4):212-26. · 1.75 Impact Factor -
Article: The effect of drying and processing red clover on the digestion of the energy and nitrogen moieties in the alimentary tract of sheep
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ABSTRACT: The effect of artificial dehydration and processing of red clover on nutrient digestion and absorption has been studied with sheep. A total of three diets were fed, each at an intake of 900 g DM d-1; comprising frozen (to represent fresh control), wafered and pelleted red clover.Dehydration caused small depressions in energy and N digestibility. Grinding and pelleting had no further effect, although both treatments reduced the amount of energy digestion occurring in the rumen, frozen 63, dried 60, pelleted 48 MJ per 100 MJ digestible energy. Digestion of energy in the caecum and colon was increased on both dried diets, and in the small intestine on the pelleted diet.Almost 40% of the extra duodenal energy on the pelleted diet was due to increased cellulose flow, with only 79% of digestible cellulose being digested in the rumen compared with 96% on the other two diets. There was an associated decrease in ruminal volatile fatty acid production of approx. 20%. Approximately half of the extra energy was due to an elevated flow of protein on the pelleted diet, but this increase was not reflected in amino acid absorption due to a reduced efficiency with the dried diets (frozen 72%, dried diets 54%).The results demonstrate that dehydration and processing of red clover can markedly influence nutrient digestion and supply and thus offer attractive means of improving the nutritive value.Grass and Forage Science 04/2006; 36(3):211 - 219. · 1.10 Impact Factor
