@conference {3672,
	title = {Genetics of alternative definitions of feed efficiency in grazing lactating dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {76},
	year = {2016},
	month = {07/2016},
	pages = {38-42},
	address = {Adelaide},
	abstract = {There has been anecdotal evidence of increasing liver abscessation on bull-beef farms across New Zealand from meat processors
for more than a decade, but to date, no quantitative data has been published in the field. This study objective was to establish the
incidence of liver abscessation in pasture- based beef bulls, the seasonality and breed differences, the impact on carcass weight,
and to compare this with published data from feedlot cattle internationally. The study used a database of 137675 bulls slaughtered
in the South Island between 2000-2005. The database included breed, farm location, carcass weight, liver abscess presence and
abscess grading score (absent, mild, moderate, severe). The annual incidence of liver abscessation calculated was a mean of 9.5\%.
This recorded value is greater than other observed incidences from pasture-based systems and reduced compared with those observed
in non-medicated feedlot systems internationally. There were significant variations in all measured parameters across years,
and a clear and significant seasonal variation was observed. Incidence of liver abscessation peaked across November- December
(11.3 and 11\% respectively) and then declined as the slaughter season progressed. The typical NZ beef industry approach to rearing
bulls for slaughter makes it likely that age at slaughter is a key influence on the seasonal incidence rate, with most cattle born in
spring and slaughtered after 18 months, suggesting the late spring and summer peak in incidence is due to bulls older than two
years. The percentages of abscesses graded were: severe (66.4\%), moderate (12.8\%), and mild (20.7\%). Friesian and dairy crossbreed
bulls had an incidence approximately twofold greater than that females beef breeds (10.3\% and 4.7\% respectively). There
was a significant difference in the mean carcass weights of bulls graded, with those moderate with abscessation having a mean
heavier carcass weight than those graded severe, minor and no abscess.},
	issn = {1176-5283},
	author = {Hurley AM and Lopez-Villalobos N and McParland S and Lewis E and Kennedy E and O{\textquoteright}Donovan M and Burke JL and Berry DP}
}
@conference {3672,
	title = {Phenotypic correlations among alternative definitions of feed efficiency in grazing lactating dairy cows across parities and lactation stages},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {75},
	year = {2015},
	month = {07/2015},
	pages = {34-38},
	address = {Dunedin},
	abstract = { The objective of this study was to estimate correlations among alternative measures of energy conversion efficiency and energy
balance (EB) across parities and lactation stages in grazing lactating dairy cows. Individual measurements of net energy intake
(NEI) (n=8,183) from pasture and concentrate from 2,693 lactations on 1,412 cows were available. Residual energy production
(REP) was defined as net energy of lactation (NEL) minus predicted energy requirements; energy conversion efficiency (ECE)
was defined as NEL divided by NEI; and EB was defined as the difference between NEI and energy required for both maintenance
and lactation. Residual energy intake (REI) was defined as NEI minus predicted energy requirements. A strong correlation existed
between REI and EB (0.88; P<0.05) for parity three or greater early lactation, weakening in parity one (0.70; P<0.05). These
differences in correlations between REI and EB for animals across parities in early lactation, indicated primiparous animals were
using body energy for milk production and growth; nevertheless, these strong correlations suggested negative REI animals (i.e.,
more efficient) are also in more-negative EB. Our findings suggest REI could be a valuable tool for future genetic improvement,},
	issn = {1176-5283},
	author = {Hurley AM and Lopez-Villalobos N and McParland S and Lewis E and Kennedy E and O{\textquoteright}Donovan M and Burke JL and Berry DP}
}
@conference {42051,
	title = {Genetics of residual energy intake in Irish grazing dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {68},
	year = {2008},
	month = {Jan},
	pages = {88-91},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Brisbane, Australia},
	abstract = {The objective of this study was to investigate the genetics of residual net energy intake (RNEI) in grazing Holstein-Friesian cows. RNEI was defined as net energy intake minus predicted net energy requirements using the unit{\'e} fourrag{\`e}re lait (UFL) system. Net energy intake from grass and concentrate was estimated up to four times per lactation on 1,111 lactations from 463 cows on an experimental farm in Southern Ireland. Grass dry matter intake was estimated using the n-alkane technique. Lactation curves for milk, fat, protein, lactose and live weight were modelled with splines using weekly measures. A random regression was used to estimate residual, additive genetic and permanent environmental variances for RNEI and breeding values at Day 60 for each cow. Heritability for RNEI across lactation varied from 0.05 at 30 days in milk to 0.38 at 296 days in milk. Genetic parameters for RNEI obtained in this study are in agreement with those obtained under indoor conditions. Comparative performance between cows of low and high RNEI breeding value at Day 60 agrees with results obtained in beef cattle selected for high or low residual feed intake showing similar productivity but higher feed conversion efficiency in cows selected for low residual feed intake.},
	issn = {1176-5283},
	author = {Lopez-Villalobos N and Berry DP and Horan B and Buckley F and Kennedy J and O{\textquoteright}Donovan M and Shalloo L and Dillon P}
}
