@article {3672,
	title = {Effect of farm system and milk urea phenotype on milk yield and milk composition of dairy cows in Canterbury},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {81},
	year = {2021},
	month = {01/2022},
	pages = {196-200},
	address = {Online},
	abstract = {To investigate the effect of farm system, and cow selection for milk urea nitrogen (MUN), on milk yield and milk composition,
a farmlet study was carried out between October 2018 and May 2019 in Lincoln, Canterbury. A farm system with a low stocking
rate and low N fertiliser input (LSR, 2.9 cows/ha) sown with a conventional ryegrass clover and plantain diverse pastures was
compared with a farm system with a moderate stocking rate and moderate N fertiliser (MSR, 3.9 cows/ha) using conventional
ryegrass and white clover pastures and supplementing 3 kg DM/cow/d as crushed barley grain. Each farmlet had total herd size of
40 mixed-age HF x J spring-calving dairy cows which included six cows selected solely for a high MUN or a low MUN. There was
no effect of farm system on milk fat, protein or lactose content but MUN was lower in LSR compared with MSR. Milk production
was also lower for LSR (466 vs 429{\textpm}12.4 kg MS/cow/ha, P<0.05), owing to poorer quality diet in mid lactation. Cows selected
for low MUN tended to produce less milk compared with high MUN cows (4478 vs 3987{\textpm}174 kg/cow, P<0.10) though this was
partially offset by increased protein content in milk of low MUN cows. Farm system and animal selection for MUN have a greater
impact on milk yield than on milk composition.

Keywords: Plantago lanceolata; somatic cell count; multi-species pastures;},
	issn = {1176-5283},
	author = {Bryant RH and O{\textquoteright}Conner PO and Robic Y and Curtis J and Handcock RC and Al-marashdeh O}
}
@article {3672,
	title = {Genetic parameters for urination traits and their relationships with production traits of dairy cattle grazing temperate ryegrass and white-clover pastures},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {81},
	year = {2021},
	month = {01/2022},
	pages = {153-158},
	address = {Online},
	abstract = {The objective of this study was to quantify genetic parameters of daily urination traits; urinary nitrogen (UN), urination volume (Uvol), urination number (Unum), average UN concentration (UNconc) and volume per urination event (VolEvent) including their genetic correlations with milk urea nitrogen concentration (MUN) and other production traits in New Zealand dairy cattle. Heritability estimates for urination traits measured on four consecutive days ranged from 0.17 to 0.35. Repeatability estimates ranged from 0.31 to 0.58, indicating that reliable prediction of urination measures would benefit from repeated measurement over a number of days. The heritability estimate for MUN was 0.29, similar to reports in the literature, whilst the estimate of repeatability (0.73) was greater than previously published values. Estimates of the genetic correlations between MUN and urination traits ranged from -0.39 to 0.41, however, due to the small number of animals in the current study, the confidence intervals were wide. The low genetic correlations may result from variation in voluntary feed intake from cow to cow that is a feature of pasture-based grazing systems. The results suggest that urination traits may be changed through selection. The low estimates of genetic correlations between MUN and urination traits suggest that MUN may not be a useful estimator of individual UN excretion in pasture-fed dairy cattle.


Keywords: urine traits; milk urea},
	issn = {1176-5283},
	author = {Handcock RC and Box LA and Glassey C and Garrick DJ}
}
@article {3672,
	title = {Growth and milk production of dairy heifers born to two-year-old or mixed-age dams},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {79},
	year = {2019},
	month = {07/2019},
	pages = {135-139},
	address = {Palmerston North},
	abstract = {Keeping replacement heifers that were the progeny of primiparous cows mated by artificial insemination, enhances rates of genetic gain. Heifers that were the progeny of primiparous cows were lighter at birth and grew at a slower rate to first calving compared with heifers born to multiparous dams. Heifers that were heavier before first calving produced more milk than did lighter heifers. This study aimed to determine if there were liveweight (LWT) or milk-production disadvantages for heifers born from primiparous compared with multiparous dams. Data comprised of LWT records from 189,936 New Zealand dairy heifers. Dams were allocated to four groups according to their age: two (2yo; n=13,717), three (3yo; n=39,258), four to eight (4-8yo; n=120,859) and nine years old or greater (>=9yo; n=16,102). Heifers born to 2yo dams were lighter (P<0.01) from three to 21 months of age than heifers born to 3yo and 4-8yo dams. The progeny of 2yo and 3yo dams produced similar milksolids yields during their first lactation (304.9{\textpm}1.6 and 304.1{\textpm}1.5 kg, respectively), but more (P<0.01) than that of 4-8yo dams (302.4{\textpm}1.5) and >=9yo dams (P<0.001; 297.8{\textpm}1.6 kg). Heifers born to 2yo dams were lighter but produced more milk than heifers from older dams.},
	issn = {1176-5283},
	author = {Handcock RC and Lopez-villalobos N and Back PJ and Hickson RE and McNaughton LR}
}
@conference {3672,
	title = {Growth curves of New Zealand Holstein-Friesian, Jersey and Holstein-Friesian-Jersey crossbred heifers},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {77},
	year = {2017},
	month = {06/2017},
	pages = {64-68},
	address = {Rotorua},
	abstract = {There are differences in the proportion of target live weight (LWT) achieved between the main breeds of dairy heifers in New Zealand, suggesting a potential difference in growth pattern. The objectives of this study were to model growth curves of dairy heifers through random regression of Legendre polynomials, and to compare growth curves of the main breeds. Data comprised of 1,653,214 LWT records obtained from 189,936 dairy heifers in 1,547 herds. The fourth-order Legendre polynomial was the best at predicting LWT, with a relative prediction error (RPE) of less than 4\% for the whole dataset and for Holstein-Friesian, Jersey and Holstein-Friesian-Jersey crossbred (F{\texttimes}J) heifers. The regression coefficients of the growth curve differed among breeds for the intercept (α0; P<0.001), linear effect (α1; P<0.001), quadratic effect (α2; P<0.001), cubic effect (α3; P<0.001) and quartic effect (α4; P<0.001). At all ages Holstein-Friesian heifers were heavier than F{\texttimes}J which were heavier than Jersey heifers (P<0.001). The percentage difference among the breeds varied throughout the growth curve, indicating that the main breeds of dairy heifers in New Zealand exhibited different growth patterns that were non-linear. The different growth patterns for each breed should be considered when formulating target LWTs and growth rates.},
	issn = {1176-5283},
	author = {Handcock RC and Lopez-Villalobos N and McNaughton LR and Edwards GR and Hickson RE}
}
@conference {3672,
	title = {More dairy heifers are achieving liveweight targets},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {76},
	year = {2016},
	month = {07/2016},
	pages = {3-7},
	address = {Adelaide},
	abstract = {Dairy heifers should reach industry liveweight targets that are set to ensure heifers achieve good reproductive performance and
milk production. The aim of this study was to determine if more dairy heifers born between the 2011-12 and 2014-15 dairy seasons
(current) in New Zealand are achieving liveweight targets since a study on heifers born between the 2006-07 and 2010-11 dairy
seasons (historic). In all age groups the mean live weight of current heifers was heavier than that of historic heifers. There were
also a greater percentage of the current heifers at or above their target live weight compared with the historic heifers (P<0.001),
suggesting that the rearing of dairy heifers has improved. The greatest improvement was seen at 15 months of age (mating) when
25\% of historic heifers were at or above target compared with 56\% of current heifers. Despite the improvement, 44\% of current
heifers were below target at mating and 65\% were below target pre-calving (22 months of age). At 22 months of age, current
heifers were on average nearly 42 kg below target live weight. By failing to achieve targets near calving, farmers are not capturing
potential milk production benefits.},
	issn = {1176-5283},
	author = {Handcock RC and Lopdell TJ and McNaughton LR}
}
@conference {3672,
	title = {The use of herb mix and lucerne to increase growth rates of dairy heifers},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {75},
	year = {2015},
	month = {07/2015},
	pages = {132-135},
	address = {Dunedin},
	abstract = { Approximately 53\% of 6-month-old dairy heifers in New Zealand do not meet liveweight targets, partially due to inadequate growth rates in their first summer. The aim of this experiment was to determine the effect of feeding forage crops on the growth
rate of dairy heifers over this critical period. Sixty six-month-old dairy heifers grazed one of three treatments: pasture, lucerne
or a mixed-herb crop for a 63-day period. Both lucerne- and crop-fed heifers had similar (P>0.05) average daily liveweight gain
(0.80 {\textpm} 0.02 and 0.75 {\textpm} 0.02 kg/day, respectively) and were greater (P<0.05) than those of pasture-fed heifers (0.53 {\textpm} 0.02 kg/
day). Lucerne-fed heifers had a greater (P<0.05) increase in body length (18.4 {\textpm} 1.3 cm) than heifers fed pasture (14.7 {\textpm} 1.2 cm).
Heifers fed lucerne had higher (P<0.05) concentrations of urea in plasma (4.9 {\textpm} 0.1 mmol/L) compared with heifers fed crop (4.1
{\textpm} 0.1 mmol/L), which had greater (P<0.05) concentrations of urea in plasma than heifers fed pasture (2.5 {\textpm} 0.1 mmol/L). Feeding a
mixed-herb crop or lucerne during the summer period resulted in higher growth rates of dairy heifer calves compared with feeding
them pasture.},
	issn = {1176-5283},
	author = {Handcock RC and Hickson RE and Back PJ}
}
