@article {3672,
	title = {Effect of genetic merit for milk urea on milk production and efficiency of crude protein utilization of grazing cows with contrasting supplement inclusion},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {79},
	year = {2019},
	month = {07/2019},
	pages = {112-117},
	address = {Palmerston North},
	abstract = {Milk urea (MU) has been proposed as a predictor of nitrogen excreted through urine into the environment. The objective of this study was to evaluate milk production performance and efficiency of crude protein utilization (ECPU) of cows with low and high MU breeding values (MUBV) in grazing conditions with two levels of dietary supplementation inclusion. From July 2016 to May 2017, 257 cows were milked once daily with low supplementation (LS; 366 kg/cow/lactation) and 210 cows were milked twice daily with high supplementation (HS; 2,091 kg/cow/lactation). Cows within each herd were ranked as low, intermediate, or high for MUBV. The dataset consisted of 2,318 records of milk production collected from monthly herd-tests of both herds; and 853 additional milk samples obtained at early, mid and late lactation to measure MU. The ECPU was calculated as the proportion of protein yield (PY) with respect to crude protein intake (CPI); with CPI derived from feed intake estimates based on energy requirements. Cows with HS had superior milk yield (MY) and milk solids yield (MSY) [MSY= PY + fat yield (FY)] (P<0.001). Feed intake was less in LS (P<0.001) but CPI was superior compared to HS. The ECPU was better in HS (P<0.001) because of higher PY (P<0.001) along with lower CPI (P<0.001). Levels of MU were superior for LS because of higher CPI. Cows with low-MUBV had significantly lower MU along with less total daily excretion of MU during the lactation (P<0.001). Irrespective of supplementary feed level, cows with low-MUBV had less MY (P<0.001). Low-MUBV did not result in improved ECPU for either supplementary feed level: under LS, ECPU was inferior in cows of low-MUBV (P<0.001), and this was explained by reduced PY (P<0.001).},
	issn = {1176-5283},
	author = {CorreaLuna M and Donaghy DJ and Kemp PD and Schutz MM and Lopez-villalobos N}
}
@article {3672,
	title = {Estimation of heritabilities for milk urea and efficiency of crude protein utilization by day of lactation in a New Zealand dairy cow herd},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {79},
	year = {2019},
	month = {07/2019},
	pages = {183-187},
	address = {Palmerston North},
	abstract = {The objective of this study was to estimate the heritability (h2) of milk urea (MU) and the efficiency of crude protein utilization (ECPU) in grazing dairy cows. Data consisted of 1,866 herd-test records for MU and ECPU from 380 cows. Genetic parameters for traits were estimated using a random regression test-day model (RRM). Herd-test date and parity had a significant effect on MU and ECPU suggesting that improvement of the traits can be made through management practices. Estimates of daily h2 ranged from 0.25 to 0.49 for MU and 0.02 to 0.41 for ECPU. The highest h2 estimates for both traits were found during late lactation. Genetic improvement of MU and ECPU should consider the genetic potential to change the lactation curves of these traits and their correlation with other productive and reproductive traits. },
	issn = {1176-5283},
	author = {Ariyarathne HBPC and CorreaLuna M and Blair HT and Garrick DJ and Lopez-villalobos N}
}
@article {3672,
	title = {BRIEF COMMUNICATION: Differential expression of lactoferrin and insulin-like growth factor-1 genes in milk from cows milked once and twice a day},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {78},
	year = {2018},
	month = {07/2018},
	pages = {109-110},
	address = {Lincoln},
	abstract = {Dairy farming in New Zealand has traditionally utilized a twice a day (TAD) milking system, but milking once a day (OAD) for the
entire lactation is also practiced by a significant proportion of dairy farmers. This study reports on the differential gene expression
in milk from OAD and TAD cows. Three predominant dairy breed group of New Zealand, Holstein-Friesian (F), Jersey (J) and F{\texttimes}J
crossbred (F{\texttimes}J) were included in samples collected from both milking regimens. RNA was extracted from milk from 45 OAD and
42 TAD dairy cows during early lactation, and used to determine lactoferrin (LF) and insulin-like growth factor-1 (IGF-1) gene
expression using qPCR. Compared to TAD cows, cows milked OAD had higher expression of the LF gene (1.38 vs 1.30 folds,
P=0.08) and the IGF-1 gene (1.65 vs 1.48 folds, P=0.09). These results suggest that milking frequency affects the expression of
milk composition genes at early lactation.},
	issn = {1176-5283},
	author = {Gedye K and Notcovich S and CorreaLuna M and Ariyarathne P and Heiser A and Lopez-villalobos N}
}
@article {3672,
	title = {Genetic parameters for milk urea concentration and milk traits in New Zealand grazing dairy cattle},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {78},
	year = {2018},
	month = {07/2018},
	pages = {56-61},
	address = {Lincoln},
	abstract = {The aim of this study was to estimate genetic parameters for milk urea (MU), yields of milk (MY), fat (FY), crude protein (CPY)
and lactose (LY), concentrations of fat (FP), crude protein (CPP) and lactose (LP) and efficiency of crude protein utilisation
(ECPU) in grazing dairy cows. Data consisted of 1284 herd-test records of milk traits and MU from 468 mixed-breed cows
in two herds. Univariate and bivariate repeatability animal models were used to estimate heritabilities (h2) and genetic (rG) and
phenotypic (rP) correlations among the traits. Estimates of h2 for MU and ECPU were 0.24 and 0.11, whereas h2 estimates for
MY, FY, CPY and LY ranged from 0.10 to 0.20. Estimates of h2 for FP, CPP and LP were 0.37, 0.59 and 0.19, respectively. The
estimates of rP for MU with other traits were near zero. The rG of MU with MY (0.38), and of MU with LY (0.31) were positive and
significant (P<0.01) whereas the rG of MU with FP (-0.80), CPP (-0.66) and LP (-0.76) were negative and significant (P<0.01). The
rG between MU and ECPU was -0.09. These estimates of genetic parameters can be used to predict genetic responses to selection
for reduction of MU.},
	issn = {1176-5283},
	author = {Lopez-villalobos N and CorreaLuna M and Burke JL and Sneddon NW and Schultz MM and Donaghy DJ and Kemp PD}
}
@article {3672,
	title = {Phenotypic correlations of milk urea and the efficiency of crude protein utilization with milk yield traits and cow performance in two contrasting dairy systems in New Zealand},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {78},
	year = {2018},
	month = {07/2018},
	pages = {76-81},
	address = {Lincoln},
	abstract = {The objectives of the present study were to investigate phenotypic correlations of milk urea (MU) and efficiency of crude protein
utilization (ECPU) with milk production and cow parameters in two contrasting herds. Between July 2016 and May 2017, 210
cows were milked twice daily with high supplementary feed inclusion (HS) and 258 cows were milked once daily with low
supplementary feed inclusion (LS). In early, mid and late lactation, milk samples were collected to measure MU. At every herdtest
date, ECPU was calculated as protein yield (PY) divided by crude protein intake (CPI); this last variable derived from intake
estimations of metabolizable energy requirements. Positive correlations between milk yield (MY) and both dry matter intake
(DMI) and CPI were observed in LS and HS. The ECPU only correlated positively with MY traits in LS, and there was no
correlation of CPI with MU in either herd. A moderate negative correlation of ECPU with live weight (LW) was observed in both
herds, but it was stronger in LS. By suppressing MY due to the reduced milking frequency of cows fed LS, these cows gained LW,
had higher body condition score and CPI, and lower PY, reducing the ECPU. No correlation between ECPU and MU was detected.},
	issn = {1176-5283},
	author = {CorreaLuna M and Lopez-villalobos N and AlmeidaJr GA and Donaghy DJ and Kemp PD}
}
@conference {3672,
	title = {BRIEF COMMUNICATION: Efficiency of crude protein utilization and milk urea nitrogen content in Friesian, Jersey and crossbred cows milked once daily},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {77},
	year = {2017},
	month = {06/2017},
	pages = {91-92},
	address = {Rotorua},
	abstract = {For the last two decades, the New Zealand dairy industry has intensified its milk production through the inclusion of feed supplements and the increasing use of nitrogen (N) fertilizer (Di \& Cameron 2000). Increasing N losses from these systems, mainly from urine (Li et al. 2012), can negatively impact the environment. Cow N utilization efficiency can play a role in mitigating this negative effect (Woodward et al. 2011)...},
	issn = {1176-5283},
	author = {CorreaLuna M and Lopez-Villalobos N and Donaghy DJ and Kemp PD and AlmeidaJr GA}
}
