Relationship of Dietary Nonprotein Nitrogen to Urea Kinetics in Dairy Cows

Mugerwa, J.S.; Conrad, H.R.

doi:10.1093/jn/101.10.1331

Cited by 37 publications

(11 citation statements)

References 18 publications

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“…The NDFN predicted for weaned, growing cattle was 6.51 g/kg of DMI. This value corresponds closely to those reported from some experiments (Mugerwa and Conrad, 1971;Stallcup et al, 1975); however, it is higher than most, which averaged 4.7 g/kg of DMI in a review by Swanson (1977). In contrast to the constant level of FN excretion observed in milk-fed calves, more FN was excreted at higher levels of NI in weaned cattle (P < 0.001).…”

Section: N Digestionsupporting

confidence: 89%

Analysis of Nitrogen Utilization and Excretion in Growing Dairy Cattle

Zanton

Heinrichs

2008

Journal of Dairy Science

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Literature data on utilization of dietary N were analyzed by using meta-analytic procedures for growing milk-fed dairy calves and weaned dairy heifers. The objective was to statistically assess N utilization and excretion in growing dairy cattle when dietary N was altered in otherwise balanced rations at various stages of growth. Studies meeting the selection criteria included data from 16 published papers encompassing 94 distinct observations made on 217 animals. Of these, 6 studied calves were fed milk or milk protein-based milk replacer [milk-fed; 30 to 81 kg of body weight (BW)] with 37 different dietary treatments, and 10 experiments studied heifers receiving diets based on forage, concentrates, or a combination of forage and concentrates (weaned; 56 to 472 kg of BW) with 57 different dietary treatments. Mixed model and fixed effect regression analyses were used to evaluate responses to additional dietary N. True digestibility of dietary N was 100.4% for milk-fed calves and 96.4% for weaned heifers, with corresponding basal fecal N excretion values of 3.05 and 6.51 g of N/kg of dry matter intake. Urinary N (g of N/kg of BW(0.75)) was consistently greater for milk-fed calves, but the response to increasing N intake was parallel to the response for weaned heifers. Whether using a mixed model approach or a fixed effect approach to account for metabolizable energy intake, BW, and dry matter intake, milk-fed calves retained more N per kilogram of BW(0.75) than weaned heifers. However, marginal efficiency of N utilization responded as a continuous function of BW, as opposed to a bimodal response associated with diet type. Gross N efficiency (GNE) responded quadratically to N intake and was greater for milk-fed calves than for weaned heifers. Linear and quadratic coefficients of this function did not differ between diet types, indicating that the response in gross N efficiency to additional N intake was not different between diet groups; rather, the absolute level obtainable differed. Dietary CP concentrations of 18.9% for milk-fed calves and 14.2% for weaned heifers were found to maximize GNE; 22.5% MJ of crude protein/MJ of ME was found to maximize GNE for both groups. Equations are discussed relative to the requirements to replace basal N losses and efficiency of N utilization.

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Section: N Digestionsupporting

confidence: 89%

Analysis of Nitrogen Utilization and Excretion in Growing Dairy Cattle

Zanton

Heinrichs

2008

Journal of Dairy Science

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“…Figure 4 shows that a similar relation can also be found for the hormone insulin. Mugerwa and Conrad, 1971); +,mature sheep (Cocimano and Leng, 1967;Ford and Milligan, 1970 Leng, 1965). 'Secretion rate' has been put in parentheses because the rate measured (by isotope dilution) is actually the rate of entry into the 'peripheral pool' of insulin.…”

Section: Reviewmentioning

confidence: 99%

The effect of feeding pattern and sampling procedure on blood parameters

Lindsay

1978

BSAP Occas. Publ.

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I am not sure what the organisers had in mind when they selected the title for this talk. To me it suggests that two components may contribute to the concentration of a metabolite - one determined by the flow of nutrients, derived either exogenously or endogenously, while a second is derived from what I propose to call ‘transitory phenomena’, that is, produced from some fleeting or transitory response - stress, human/animal interaction or a response to feeding as distinct from food. Presumably it is the first component which we would hope to relate in some way to animal production, and I propose to begin by seeing to what extent we find a close relation between flow and concentration for several blood constituents. I have used the term ‘flux’ to encompass conveniently what has variously been called ‘entry rate’, ‘turnover rate’ and ‘irreversible’ loss. These terms are not synonymous, but for the present discussion the distinctions are not important.

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“…Renal capacity may be overloaded when the entry rate of urea is very high. In the study of Mugerwa and Conrad (1971), the renal urea excretion leveled off at an NPN intake of 175 g/d. It was concluded from the excretion curve that the ability of the kidney to concentrate urea reached a physiological limit.…”

Section: Introductionmentioning

confidence: 99%

Effect of Rumen-Degradable Protein Balance and Forage Type on Bulk Milk Urea Concentration and Emission of Ammonia from Dairy Cow Houses

Duinkerken

André

Smits

et al. 2005

Journal of Dairy Science

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As the Dutch government and dairy farming sector have given priority to reducing ammonia emission, the effect of diet on the ammonia emission from dairy cow barns was studied. In addition, the usefulness of milk urea content as an indicator of emission reduction was evaluated. An experiment was carried out with a herd of 55 to 57 Holstein-Friesian dairy cows housed in a naturally ventilated barn with cubicles and a slatted floor. The experiment was designed as a 3 x 3 factorial trial and repeated 3 times. During the experiment, cows were confined to the barn (no grazing) and were fed ensiled forages and additional concentrates. The default forage was grass silage. The nutritional experimental factors were: (1) rumen-degradable protein balance of the ration for lactating cows with 3 levels (0, 500, and 1000 g/cow per d), and (2) proportion of corn silage in the forage ration for lactating cows with 3 levels (0, 50, and 100%) of forage dry matter intake. Several series of dynamic regression models were fitted. One of these models explained emission of ammonia by the nutritional factors and the temperature; another model explained ammonia emission by the bulk milk urea content and the temperature. The ammonia emission from the barn increased when levels of rumen-degradable protein balance increased. Furthermore, at a given level of rumen-degradable protein balance, the emission of ammonia correlated positively with the corn silage content in the forage ration. However, this correlation was not causal, but was the result of interaction between corn silage proportion and intake of ileal digestible protein. The bulk milk urea content and the temperature correlated strongly with the ammonia emission from the barn; the selected model accounted for 76% of the variance in emission. It was concluded that the emission of ammonia from naturally ventilated dairy cow barns was strongly influenced by diet. The emission can be reduced approximately 50% by reducing the rumen-degradable protein balance of the ration from 1000 to 0 g/cow per d. The milk urea content is a good indicator of emission reduction.

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Relationship of Dietary Nonprotein Nitrogen to Urea Kinetics in Dairy Cows

Cited by 37 publications

References 18 publications

Analysis of Nitrogen Utilization and Excretion in Growing Dairy Cattle

Analysis of Nitrogen Utilization and Excretion in Growing Dairy Cattle

The effect of feeding pattern and sampling procedure on blood parameters

Effect of Rumen-Degradable Protein Balance and Forage Type on Bulk Milk Urea Concentration and Emission of Ammonia from Dairy Cow Houses

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