Pathways to improving the N efficiency of grazing bovines

Hoekstra, Nyncke J.; Schulte, Rogier P.O.; Struik, P.C.; Lantinga, E.A.

doi:10.1016/j.eja.2006.12.002

Cited by 67 publications

(67 citation statements)

References 87 publications

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“…The RUP content in fresh pasture is generally low and with values ranging between 11.7, 8 and 3% CP for a permanent pasture with 27% CP, adjusted for rumen passage rate of 8, 5 and 2% h -1 , respectively (Anrique et al, 2008). Also RUP increases slightly with longer grazing intervals (Hoekstra et al, 2007).…”

Section: Pasture As a Source Of Nitrogenmentioning

confidence: 99%

“…Pastures undergoing intensive N fertilization have reached CP levels higher than 300 g kg -1 DM with NPN concentrations from 240 to 420 g kg -1 total N (Goswami and Willcox, 1969), thus increasing the risk of negative effects on the animal and the environment and achieving a low NUE (Cosgrove et al, 1999;Bendall, 2001;Bolan and Kemp, 2003;. The low NUE obtained under grazing conditions is basically due to the high dietary N intake, coupled with a high concentration of soluble protein and an imbalance and asynchrony between protein and energy supplies to the rumen (Nolan and Dobos, 2005;Hoekstra et al, 2007;, and represents a loss of N and energy potentially available for productive purposes .…”

Section: Pasture As a Source Of Nitrogenmentioning

confidence: 99%

“…An example of this situation is the low conversion of dietary N into milk N, ranging between 13 and 31% in grazing systems and 40 to 45% under confinement systems with balanced rations (Delagarde et al, 1997;Verité and Delaby, 2000). A low N use efficiency (NUE) is basically due to the incapacity of animals to build significant amounts of protein reserves, being necessary to adjust protein supply according to protein requirements (Hoekstra et al, 2007). Energy is the main limiting nutrient for productivity under grazing conditions, while amino acids supply usually exceeds animal requirements (Kolver et al, 1998).…”

mentioning

confidence: 99%

“…Due to the negative effects related to low NUE, it is necessary and challenging to develop strategies that allow increasing NUE in dairy systems. Under confinement conditions there are several approaches to optimize the proportion of dietary N converted into milk N (Verité and Delaby, 2000;Castillo et al, 2001;Hristov and Jouany, 2005;Flachowsky and Lebzien, 2006;Hoekstra et al, 2007), unfortunately there is still uncertainty about the pathways that may improve NUE under grazing dairy systems.…”

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confidence: 99%

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Nutritional Strategies to Improve Nitrogen use Efficiency by Grazing Dairy Cows

Keim

Anrique

2011

Chilean J. Agric. Res.

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Grazing dairy cows are characterized by converting a low proportion of dietary N into milk N. This low N use efficiency (NUE) is mainly due to an excessive supply of crude protein (CP) of pasture with regard to animal requirements. Excess N in the diet has negative effects for the animal; it alters the organoleptic characteristics of milk and pollutes the environment through N excretions. The aim of this review was to analyze the available information on nutritional strategies to improve NUE by grazing dairy cows, such as diluting the dietary N through supplementation, synchronizing ruminal carbohydrate (CHO), and N fermentation rates, and using pastures with a high water soluble carbohydrates (WSC) content. There is a beneficial effect of carbohydrate supplementation on NUE, with an increase in milk yield (MY) of 0.83 ± 0.34 kg milk kg -1 supplement and a reduction of ammonia N (NH 3 -N) in the rumen. A better synchrony between CHO and rumen N does not improve MY and NUE. However, a positive effect on NUE was identified as a result of increasing the WSC/CP ratio. The use of cultivars with high WSC content increases the dry matter intake (DMI), MY, and milk N production, with no consistent effect on NUE.

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Section: Pasture As a Source Of Nitrogenmentioning

confidence: 99%

Section: Pasture As a Source Of Nitrogenmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Nutritional Strategies to Improve Nitrogen use Efficiency by Grazing Dairy Cows

Keim

Anrique

2011

Chilean J. Agric. Res.

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“…Omitting this population resulted in a signiWcant correlation (r = 0.939, n = 7, P = 0.002). It is not unusual for WSC content to be increased at lower N fertiliser rates and vice versa (Hoekstra et al 2007). However, in the large plot Weld experiment, low N application also increased the magnitude of the divergence observed between the pairs of populations.…”

Section: Discussionmentioning

confidence: 99%

Testing water-soluble carbohydrate QTL effects in perennial ryegrass (Lolium perenne L.) by marker selection

Turner¹,

Farrell²,

Humphreys³

et al. 2010

Theor Appl Genet

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Water-soluble carbohydrates (WSC) are an important factor determining the nutritional value of grass forage and development of genetic markers for selection of WSC traits in perennial ryegrass would beneWt future breeding programmes. Quantitative trait loci (QTLs) for WSC have been published for an F 2 ryegrass mapping family. Markers showing signiWcant associations with these QTLs were used to design narrow-based populations with homozygosity for target QTLs. Founders were selected from within the mapping family. The divergent populations produced were analysed for WSC content in the glasshouse and the Weld. There was evidence of complex interactions between WSC content and other factors and traits, including the scale of assessment, time/degree of sward establishment and other forage quality parameters. DiVerences between the divergent pairs of the various populations were small. However, diVerences observed between the founder selection groups were maintained and the roles of the QTL regions in regulating forage WSC content were conWrmed. In general, the individual divergent populations exploited only a limited extent of the large phenotypic variation available within the mapping family. However, this study sets the scene for exploring the opportunities for markerassisted breeding strategies for complex traits in obligate out-breeding species, and the challenges of doing this are discussed. Abbreviations

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