@article {3672,
	title = {Ultrasound and histopathological studies of mastitis in hill-country ewes},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {82},
	year = {2022},
	month = {01/2022},
	pages = {57-63},
	address = {Online},
	abstract = {<p>To determine the prevalence of mastitis in hill-country ewes, 1824 mixed-age Romney ewes in one flock were examined after weaning. Ninety-one (5\%) had clinical mastitis and, of these, 18 (1\%) had hard udder. Defects detected by ultrasound scanning (later confirmed by gross and histopathological examination) included abscesses and fluid accumulations in gland cisterns. Four months after weaning (2-3 months after diagnosis with mastitis) udders of 57 of the 91 culled mastitic ewes, randomly selected, were examined. Teat and gland parenchyma from 50 of these were later assessed histopathologically. Common findings were abscesses involving gland parenchyma and teats, pus in teat cisterns, mucosal polyps associated with lymphocytic inflammation in teat cisterns leading to stenosis or atresia, and mild-to-moderate lymphocytic inflammation in the gland interstitium. Results indicate that a significant proportion of ewes with severe and/or permanent mastitis damage such as hard udder can be identified by palpation and ultrasound soon after weaning, but some signs, notably hard udder, had disappeared by the time of post-mortem 2-3 months later.</p>
},
	issn = {1176-5283},
	author = {Peterson SW and Collett MG and Kennedy EBG and Molenaar AJ and Nieper B}
}
@article {3672,
	title = {Effect of concurrent pregnancy on the persistency of lactation in dairy cows milked once a day},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {81},
	year = {2021},
	month = {01/2022},
	pages = {99-105},
	address = {Online},
	abstract = {Persistency of lactation is a trait of economic importance in any dairy production system. The objective was to investigate the effect of concurrent pregnancy on the persistency of lactation in a commercial herd of dairy cows milked once a day. The data set included 1962 monthly herd-test records (total 8-9 tests per cow) of milk, fat, protein and lactose yield from 219 pregnant cows and 23 non-pregnant cows of different breeds and lactation number. The records were used to model lactation curves for pregnant and non-pregnant cows using random regression with a linear model (Wilmink function). This was not an experiment initially designed to examine the effects of pregnancy on persistency of lactation in dairy cows. Rather, in the course of normal farm operations, some cows became pregnant during lactation and others did not. Pregnancy did not affect the persistency of lactation of cows milked OAD. After conception, there was no difference in total yields between the two groups, but there was a trend that pregnant cows produced lower yields of fat (P=0.0519) and lactose (P=0.0884). This difference between our results and those of previous studies was probably because our cows were only milked once a day or because the data set was not suitable for testing the hypothesis. Further study is required to investigate persistence of lactation in pregnant and non-pregnant cows milked OAD.

Keywords: pregnancy; lactation persistency; cows milked once a day},
	issn = {1176-5283},
	author = {Fu Y and Peterson SW and Lopez-villalobos N}
}
@article {3672,
	title = {The effects of out-of-season breeding on plasma prolactin concentrations, wool production and lamb birth weight},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {81},
	year = {2021},
	month = {01/2022},
	pages = {129-135},
	address = {Online},
	abstract = {Performance of autumn- and spring-lambing ewes was compared in a year-long trial. Ewes were shorn in November and mated to lamb in May or August. Midside wool samples and plasma were collected at seven-week intervals to determine wool-growth rate, fleece characteristics, and prolactin concentrations. Autumn lambs were lighter (P<0.001) at birth and weaning (3.92{\textpm}0.1; 15.6{\textpm}0.7 kg) than spring lambs (5.27{\textpm}0.1; 25.3{\textpm}0.7 kg). Plasma prolactin concentrations were high (150 ng/ml) at mating (Dec) of autumn-lambing ewes, but low (50 ng/ml) at mating (March) of spring-lambing ewes. Both groups exhibited periparturient prolactin surges, but in autumn-lambing ewes this created high plasma prolactin concentrations during early pregnancy when plasma prolactin is usually very low. In autumn-lambing ewes, clean fleece weights (3.75{\textpm}0.11 kg), midside wool growth over 345 d (374{\textpm}12 mg/cm2) and fibre diameter (39.8{\textpm}0.5 mm) were significantly higher (P<0.05) than those of spring-lambing ewes (3.26{\textpm}0.12 kg; 331{\textpm}14 mg/cm2; 38.2{\textpm}0.5 mm respectively) whilst bulk and colour did not differ. Bulk was higher (P<0.05) in single-bearing ewes (21.1{\textpm}0.4 cm3/g) than in twin-bearing ewes (19.2{\textpm}0.7 cm3/g). It is postulated that elevated plasma prolactin concentrations (at key times) are related to seasonal differences in birth and fleece weights. Autumn lambing is beneficial for wool growth but detrimental for lamb birth weight and growth.


Keywords: out-of-season lambing; sheep; prolactin; wool growth; birth weight},
	issn = {1176-5283},
	author = {Peterson SW and Burnham DL and Morris ST}
}
@article {3672,
	title = {Effects of maternal bromocriptine and melatonin treatments during early gestation on fetal lamb growth},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {79},
	year = {2019},
	month = {07/2019},
	pages = {74-79},
	address = {Palmerston North},
	abstract = {Lower birth weights of autumn-born than of spring-born lambs may be due to a seasonal impairment of placental development, established by d84 of gestation, and perhaps mediated by high summer prolactin concentrations. This study attempted to determine whether reducing circulating summer prolactin concentrations in ewes during early gestation, using bromocriptine and melatonin, would improve placental and fetal growth and birth weights of autumn-born lambs. Pregnant mixed-age Romney ewes were randomly allocated to three treatment groups, balanced for age, live weight (LW) and source flocks, on d15 after mating. Ewes in the Bromocriptine group (n=20, LW 58.3{\textpm}6.7 kg) were injected with 50 mg Parlodel{\textregistered}LA, the Melatonin group (n=20, LW 58.6{\textpm}6.6 kg) each received one 18-mg Regulin{\textregistered} implant, while the Control group (n=21, LW 58.5{\textpm}5.8 kg) was injected with saline solution (0.9\% NaCl). At d139 of gestation, ewes were randomly allocated to a {\textquoteleft}Slaughter group{\textquoteright} sacrificed at d140-2 (n=30 LW 61.2{\textpm}5.6 kg) and a {\textquoteleft}Live-birth group{\textquoteright} (n=31, LW 60.0{\textpm}7.1 kg). Maternal plasma prolactin concentrations were significantly reduced by both bromocriptine (Control vs. Bromocriptine): 48.3{\textpm}9.2 vs. 0.7{\textpm}9.9 ng/ml (P<0.001) at d20 of gestation, and 82.6{\textpm}8.5 vs. 4.5{\textpm}9.1 ng/ml (P<0.001) at d40 of gestation, and melatonin treatments (Control vs. Melatonin): 82.6{\textpm}8.5 vs. 18.4{\textpm}9.5 ng/ml (P<0.001) at d40 of gestation, and 16.8{\textpm}3.7 vs. 2.9{\textpm}4.2 ng/ml (P<0.05) at d60 of gestation. Fetal plasma prolactin concentrations were not affected by treatments (Control vs. Bromocriptine vs. Melatonin): 32.4{\textpm}18.3 vs. 32.4{\textpm}19.1 vs. 59.8{\textpm}16.4 ng/ml. At d140 of gestation, there were no treatment effects (adjusted for sex and litter size) on fetal weight, crown-rump length, placental parameters, and maternal and fetal organ weights, except thymus reduced 20\% (P<0.05) by melatonin treatment. Birth weights and subsequent growth rates were similar among groups. Despite treatments reducing plasma prolactin concentrations there was no affect on placental or fetal growth, indicating that high prolactin concentrations early in pregnancy are not responsible for low birth weight in ewes lambing in May.},
	issn = {1176-5283},
	author = {Peterson SW and Wigati S and Jenkinson CMC}
}
@article {3672,
	title = {BRIEF COMMUNICATION: Impact of maternal plane of nutrition, ewe weight and twinning on fetal mammary gland development in sheep},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {78},
	year = {2018},
	month = {07/2018},
	pages = {183-185},
	address = {Lincoln},
	abstract = {This study evaluated the effects of maternal nutrition, weight and gestation rank on fetal mammary gland development. Light
(L) and heavy (H) single- and twin-bearing ewes were fed ad libitum (A) or maintenance (M) nutritional regimens from day
21 to day 140 of gestation and euthanised for tissue collection. Plane of maternal nutrition or maternal weight did not affect
histomorphometry of fetal mammary glands. Singleton fetuses had 43\% greater total duct area (P<0.05), 62\% greater secretory cell
area and 32\% fewer ducts (P<0.05) but similar total lumen area, cell size and total cell number than twins. These results indicate
that twinning reduces area of mammary ducts and secretory cell area while maternal weight and plane of nutrition from day 21
have little impact on mammary morphology at day 140 of gestation.},
	issn = {1176-5283},
	author = {McCoard SA and Adiletta AM and Jenkinson CMC and Peterson SW and Kenyon PR and Blair HT}
}
@article {3672,
	title = {The impact of different management systems on behaviour and milk production of dairy ewes in different stages of lactation; a case study},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {78},
	year = {2018},
	month = {07/2018},
	pages = {116-121},
	address = {Lincoln},
	abstract = {Comparisons of New Zealand dairy sheep farm systems are currently lacking. The aim of this preliminary study was to evaluate
the effects of different management systems on the behaviour and milk production of East Friesian cross-bred sheep at different
stages of lactation. Two study groups were evaluated. In study group 1, a mob of 479 mixed-age, mid-lactation ewes were housed
24 h/day, and a separate mob of 473 mixed-age, mid-lactation ewes were managed in a hybrid system (housed between morning
and afternoon milkings; grazed lucerne overnight). Both received a total mixed ration (TMR) indoors. In study group 2, a mob of
604 mixed-age, late-lactation ewes grazed pasture 24 h/day, and a separate mob of 452 mixed-age late-lactation ewes were in a
hybrid system, grazing pasture overnight. For both study groups, individual milk yield, walking distance, lying time, live weight
(LW), and body condition score (BCS) were recorded. All sheep gained BCS and LW except fully grazed late-lactation ewes. For
study group 1, fully housed ewes in mid-lactation lay down less during the day, but more overnight compared to those in the hybrid
system, likely due to the latter grazing overnight. Lying bout times were similar between groups, while milk yield was 29\% less
in housed ewes compared to the hybrid ewes. For study group 2, grazing ewes in late-lactation lay down more, had longer lying
bouts, and walked further daily than those in the hybrid system, but both late-lactation treatment groups had similar milk yields.
In summary, the hybrid management system seems to improve milk yield in mid-lactation compared to the fully housed system,
whereas there was no difference between the hybrid and fully grazed systems in late-lactation. Lying behaviour and walking
distances (group 2 only) differed among different systems, however, it is unclear what this means in terms of animal welfare, and
warrants further investigation.},
	issn = {1176-5283},
	author = {Bliss AE and Chylinski C and Luo D and Sch{\"u}tz KE and Lowe K and Peterson SW and Stevens D and MacDonald T and McCoard SA}
}
@conference {3672,
	title = {BRIEF COMMUNICATION: An investigation of mastitis in a hill-country sheep flock},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {77},
	year = {2017},
	month = {06/2017},
	pages = {114-116},
	address = {Rotorua},
	abstract = {The prevalence of mastitis in New Zealand ewes has not been studied for over 40 years. Quinlivan (1968a,b) examined 19427 Romney ewes in the lower North Island and detected mastitis in 0.6-1.7\%. Clarke (1972) surveyed 118249 ewes in the lower South Island and found the incidence of mastitis was 0.6-0.7\%. Skyrme (1970) reported the occurrence of {\textquotedblleft}hard udders{\textquotedblright} and implicated them in lamb deaths. Perhaps because of such reports of low incidence, little research into sheep mastitis has been done in New Zealand...},
	issn = {1176-5283},
	author = {Peterson SW and Nieper B and Collett MG and Grinberg A}
}
@conference {3672,
	title = {The effects of early access to meal on the behaviour of artificially reared dairy lambs},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {77},
	year = {2017},
	month = {06/2017},
	pages = {18-22},
	address = {Rotorua},
	abstract = {he New Zealand sheep dairy industry is growing (Peterson \& Prichard 2015). Several large commercial sheep dairy farms remove lambs from their dams within the first four days of life. In some systems, lambs have access to milk replacer (MR) ad libitum and a grain-based solid feed (Bimczok et al. 2005). Compared to young ruminants fed a milk-only diet, early access to solid feed stimulates rumen development (Baldwin et al. 2004) and earlier onset of rumination (Khan et al. 2016) to allow early weaning off MR (Bimczok et al. 2005). Earlier rumen development through access to meal may also encourage earlier grazing of pasture and greater rumination, thereby supporting early weaning. The potential to replace meal with early pasture access as the sole solid feed source to support early weaning has not been evaluated...},
	issn = {1176-5283},
	author = {Nieper BA and Khan MA and Ganesh S and Knol FW and Peterson SW and Stafford KJ and Stevens DR and McCoard SA}
}
@conference {3672,
	title = {How does feeding meal affect growth of artificially reared East Friesian-cross dairy lambs?},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {77},
	year = {2017},
	month = {06/2017},
	pages = {13-17},
	address = {Rotorua},
	abstract = {Artificial rearing is routinely used in large-scale dairy sheep farms. One approach is to offer milk replacer (MR) and meal ad libi-tum to lambs. Our aim was to evaluate growth performance of female lambs in the first 12 weeks of rearing with (M) and without (NM) grain-based meal access (n=30/group) during four feeding periods. In period 1 (wk 0-3) lambs were offered MR and meal ad libitum, and in period 2 (wk 4-5) were transitioned outdoors onto pasture with continued access to MR and meal. Lambs were weaned off MR in period 3 (wk 6-10), and meal in period 4 (wk 10-12). The NM lambs received identical management but meal was excluded. A treatment-by-time interaction was found whereby NM lambs had lower average daily gain (ADG) (P<0.05) in periods 1 (376{\textpm}6 vs. 414{\textpm}8 g/day) and 3 (146{\textpm}7 vs. 241{\textpm}7 g/day), no difference in period 2 (P>0.05), and higher ADG in period 4 (157{\textpm}18 vs. -55{\textpm}18 g/day, P<0.05) than M lambs. There was no difference (P>0.05) in live weight by week 12, and all lambs survived. These results indicate when lambs fed MR ad libitum are offered unrestricted access to good-quality pasture before weaning, meal may not be required to achieve a similar live weight at 12 weeks.},
	issn = {1176-5283},
	author = {Jensen AC and Khan MA and Knol FW and Peterson SW and Morel PCH and McKenzie C and Stevens DR and McCoard SA}
}
@conference {3672,
	title = {Prototype genetic evaluation in a New Zealand dairy sheep flock},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {77},
	year = {2017},
	month = {06/2017},
	pages = {121-124},
	address = {Rotorua},
	abstract = {Dairy sheep milking is an emerging industry in New Zealand, but at present there is no national breeding scheme. A prototype model for the genetic evaluation of dairy sheep was developed. Data were obtained from a flock of 123 crossbred ewes, over 479 monthly flock tests during the season 2015/16.  Breeding values were estimated for lactation yields of milk, fat, protein and lac-tose, and for live weight, somatic cell score, first let-down time and yield, and number of lambs born, from a multiple-trait animal model. Heritabilities and phenotypic and genetic correlations required for the model were obtained from the literature, and pheno-typic standard deviations were obtained from the data set. This prototype model to obtain estimated breeding values of animals in this flock can be extended to other dairy sheep farmers, to create selection schemes at industry level and start a systematic breeding program for the emerging New Zealand dairy sheep industry.},
	issn = {1176-5283},
	author = {Scholtens MR and Peterson SW and Gunson K and Gunson A and Lopez-Villalobos N}
}
@conference {3672,
	title = {BRIEF COMMUNICATION: Does Viagra protect fetal lambs against maternal pregnancy toxaemia?},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {76},
	year = {2016},
	month = {07/2016},
	pages = {172-174},
	address = {Adelaide},
	abstract = {Poor fetal growth is commonly caused by placental
insufficiency. In sheep, multiple fetuses have relatively small
placentae with fewer cotyledons than singletons, limiting
blood flow to the placenta, especially in late gestation
when fetal growth rate is highest. Factors that reduce fetal
growth, such as maternal genotype, nutrition, age, parity,
fetal number, or environmental temperature, typically
reduce placental size and are associated with lower rates
of fetal oxygen and nutrient uptakes and placental blood
flow (Reynolds \& Redmer 2001). Further, circumstances
that influence placental vascular development have a
dramatic impact on fetal growth and development, and
affect neonatal survival and growth (Borowicz et al. 2007;
Satterfield et al, 2010).
Sildenafil citrate (SC, trade names Viagra or Avigra)
increases vasodilatation of uteroplacental vessels (Wareing
et al. 2005) and may represent a novel therapy to improve
fetal lamb growth. Sildenafil citrate has successfully
increased birth weight in rodent models and singleton bearing
ewes (Satterfield et al. 2010; Miller at al. 2009).
There is no published information regarding the use of SC
in multiple-bearing ewes. The objective of this trial was to
determine if SC administration to triplet-bearing ewes in
late gestation could increase lamb birth weight. In addition,
the influence of SC on the incidence of pregnancy toxaemia
is also reported here.},
	issn = {1176-5283},
	author = {Peterson SW and Pain SJ and McCoard SA and Oliver M and Baker PN and Kenyon PR and Blair HT}
}
@conference {3672,
	title = {The sheep dairy industry in New Zealand: a review},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {75},
	year = {2015},
	month = {07/2015},
	pages = {119-126},
	address = {Dunedin},
	abstract = { },
	issn = {1176-5283},
	author = {Peterson SW and Prichard C}
}
@conference {3728,
	title = {BRIEF COMMUNICATION: Developmental programming in sheep due to early pregnancy nutrition alters milk yields of adult female offspring but not of grand-offspring},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {74},
	year = {2014},
	month = {06/2014},
	pages = {212-214},
	address = {Napier},
	abstract = {Two long-term studies by our group have shown that nutrition of the pregnant dam altered the growth and development of the ewe offspring, and their subsequent lactational performance (van der Linden et al. 2009; Paten et al. 2013a). These effects were attributed to developmental programming possibly via epigenetic changes. Epigenetic regulation, such as histone modifications and chromatin condensation, has been implicated in the short- and long-term control of transcription in mammary epithelial cells (Kress et al. 2010)...},
	issn = {1176-5283},
	author = {Peterson SW and Pain SJ and Jenkinson CMC and Kenyon PR and Blair HT}
}
@conference {3678,
	title = {BRIEF COMMUNICATION: Inter-generational effects on male offspring born to ewes whose dams were offered varying feeding levels in pregnancy},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {74},
	year = {2014},
	month = {06/2014},
	pages = {199-201},
	address = {Napier},
	abstract = {There is a growing body of evidence to indicate that pregnancy nutrition can affect the productive performance of the offspring in sheep (Kenyon \& Blair 2014). Recently we demonstrated that pastoral-based feeding of the ewe (G0) can affect the milk production of the ewe offspring (G1) and the growth and live weight of the grand-offspring (G2) to weaning (van der Linden et al. 2009; Paten et al. 2013). An effect of feeding on grand-offspring is termed an inter-generational effect, and while these effects have been reported in species such as mice and rats, their occurrence in the sheep literature is rare.
There is some evidence to suggest feeding of the ewe in pregnancy can alter the growth and carcass characteristics of her offspring (see review Greenwood et al. 2010) but there is no data available on potential inter-generational effects. The aim of the present study was to determine if feeding of the ewe (G0) in either early- or mid- to late-pregnancy could alter the live weight and slaughter characteristics of male grand (G2) offspring...},
	issn = {1176-5283},
	author = {Burnham DL and Kenyon PR and Pain SJ and Hickson RE and Peterson SW and Blair HT}
}
@conference {75873,
	title = {BRIEF COMMUNICATION: The effects of dam nutrition during pregnancy on the postnatal growth and puberty attainment of ewe progeny},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {71},
	year = {2011},
	month = {Jan},
	pages = {56-58},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Invercargill},
	abstract = {In New Zealand{\textquoteright}s pastoral sheep-production systems, feed can become limiting during winter, when breeding ewes are pregnant. Ewes are often restrictively fed during early-gestation (Kenyon \& Webby, 2007) to enable greater levels of nutrition in late-gestation. Many studies have demonstrated that dam nutrition during various stages of pregnancy can program the...},
	issn = {1176-5283},
	author = {Paten AM and Asmad K and Loureiro MFP and Kenyon PR and Pain SJ and Peterson SW and Pomroy WE and Scott I and Blair HT}
}
@conference {69503,
	title = {Preliminary investigation of milk production in Angus heifers exposed to different nutrition in utero},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {70},
	year = {2010},
	month = {Jun},
	pages = {194-198},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {Milk yield (MY) and composition were measured on one day in Weeks 7, 9 and 11 in 17 offspring of Angus cows fed for high (1.2 kg/d; HB) or medium (0.5 kg/d; MB) liveweight gain (LWG) for 10 days before insemination and medium (0.5 kg/d; MA) or low (0.01 kg/d; LA) LWG during gestation. Mean MYs in the progeny were; Week 7: 5790 {\textpm} 420 g/d, Week 9: 7418 {\textpm} 447 g/d, Week 11: 6244 {\textpm} 392 g/d. Better feeding before mating had little effect on MY or milk crude protein (CP\%) in the progeny but tended to reduce the milkfat\% (Week 9; HB (n = 8) 3.50 {\textpm} 0.17\% versus MB (n = 8) 3.74 {\textpm} 0.22\%) (P <0.19), casein (Week 11; HB 2.59 {\textpm} 0.03\% versus MB 2.68 {\textpm} 0.04\%) (P = 0.11) and lactose (Week 11; HB 5.18 {\textpm} 0.13\% versus MB 5.42 {\textpm} 0.05\%) (P = 0.075). Better feeding of the dam after artificial insemination did not significantly increase MY of the progeny (Week 9; MA (n = 9) 7972 {\textpm} 378 g/d versus LA (n = 8) 6794 {\textpm} 826 g/d) (P = 0.23), or milkfat\%, decreased CP (Week 9; MA 3.22 {\textpm} 0.07\% versus LA 3.41 {\textpm} 0.08\%) (P <0.09) and casein\% (at Weeks 7 and 9 identical values of MA 2.52 {\textpm} 0.06\% versus LA 2.69 {\textpm} 0.07\%), but increased lactose\% after the peak of lactation (Week 11 MA 5.42 {\textpm} 0.06\% versus LA 5.15 {\textpm} 0.14\%) (P <0.08). Feeding before and after conception may affect the nutrition of the grand generation},
	issn = {1176-5283},
	author = {Peterson SW and Jenkinson CMC and Hickson RE and Morris ST and Blair HT and Kenyon PR}
}
@conference {41965,
	title = {The effects of ewe size and nutrition during pregnancy on growth and onset of puberty in female progeny},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {126-129},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {In 2005, {\textquoteleft}heavy{\textquoteright} and {\textquoteleft}light{\textquoteright} Romney ewes were selected, synchronized and artificially inseminated. Half of the ewes in each weight group were fed ad libitumand the other half were restricted to maintenance from days 21-140 of pregnancy, resulting in fourgroups: {\textquoteleft}heavy{\textquoteright}-maintenance (HM), {\textquoteleft}heavy{\textquoteright}-ad libitum(HA), {\textquoteleft}light{\textquoteright}-maintenance (LM) and {\textquoteleft}light{\textquoteright}-ad libitum(LA). The aim of the present study was to investigate the effects of ewe size and nutrition during pregnancy on growth and onset of puberty in female progeny. Lamb birth weights were recorded. After weaning, the progeny were managed as one flock and weighed monthly. Crayon-harnessed teaser rams were joined with the lambs to investigate the onset of puberty. Maternal nutrition during pregnancy affected live weight of lambs from 22 days of age till weaning (100 days of age) (P<0.05). During the first 22 days of life, the growth rate of lambs born to LM was lower (P<0.05) compared with the other groups (215 {\textpm} 8.2, 261 {\textpm} 8.0, 250 {\textpm} 7.9, 275 {\textpm} 7.3 grams/day, for lambs born to LM, LA, HM and HA ewes respectively). From weaning until one year of age lambs born to LM dams were lighter than lambs born to HM dams (P<0.05). No differences in the age of onset of puberty were found among the four groups. Singletons reached puberty earlier than twins (P<0.01). At 13 months of age, no long-term effect of maternal nutrition on the live weight of resulting ewe offspring was found, although dam size had a significant effect on live weight and growth rate. However, neither dam nutrition nor size had any effect on the age of onset of puberty.},
	issn = {1176-5283},
	author = {van der Linden DS and Kenyon PR and Jenkinson CMC and Peterson SW and Lopez-Villalobos N and Blair HT}
}
@conference {41942,
	title = {Do ewes with twin and triplet lambs produce different yields of milk and does the grazing behaviour of their lambs differ?},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {444-449},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {This trial was designed to determine if ewes with triplets produce more milk than those with twins, and, if not, do triplet lambs compensate by extra grazing. Milk yield (MY) of ewes with twin (n=13) and triplet (n=8) lambs, grazing pasture in spring was measured four, seven and ten weeks postpartum. Ewes and lambs were separated in the morning and MY was measured by the oxytocin method. MY did not differ in ewes with triplets (2525 {\textpm} 243 g/d) from that in ewes with twins (2204 {\textpm} 149 g/d) at week four, week seven (1847 {\textpm} 238 versus 1684 {\textpm} 111 g/d), or at week ten (1448 {\textpm} 139 versus 1264 {\textpm} 85 g/d). NIRS analyses showed no significant consistent difference in fat (triplet: twin 7.7: 7.5 {\textpm} 0.4\%), protein (4.4: 4.3 {\textpm} 0.2\%), lactose (4.71: 4.72 {\textpm} 0.03\%) and total solids (17.48: 17.36 {\textpm} 0.35\%) composition of milk from ewes with triplet or twin lambs (data are means of all samples). Mammary gland dimension B, the distance across the gland next to the teats, was better correlated (R2 0.31, P<0.05) with MY than other dimensions tested. Behaviour observations (whether the lamb was grazing or suckling) were made weekly 3-9 weeks postpartum. The time spent grazing by triplets (39.4 {\textpm} 1.94 \% on lactation day 29) was significantly greater (P<0.05) than the time spent grazing by twins (37.7 {\textpm} 1.94\% on lactation day 29) on three observation days and, overall, triplet lambs spent more time grazing than twin lambs. Birth weight of twin lambs (4.39 {\textpm} 0.14 kg) was not significantly greater than that of triplets (4.00 {\textpm} 0.20 kg), but they grew significantly faster (P<0.05) from week four till week ten, gaining 17.0 kg compared to 14.9 kg for triplets. Triplets suffer a relative lack of available milk nutrients compared to twins and are not able to completely compensate for this by increasing grazing time. },
	issn = {1176-5283},
	author = {Peterson SW and Kenyon PR and Morris ST}
}
@conference {41691,
	title = {Milk production in Romney ewes lambing out of season},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {450-455},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {Milk yield (MY) of groups of Romney ewes lambing at 3 times of the year: January (n=9), March (n=14) and June (n=13)) was measured on alternate days in the first week postpartum and at weekly intervals for nine weeks. Twin-bearing ewes produced significantly more milk than single-bearing ewes during the first week and during the whole of lactation (63 days) (P<0.05), except in the January-lambing group, in which ewes with single lambs produced more milk then those with twins during the first week. The shape of the lactation curve for ewes with singles or twins differed significantly (P<0.01) between lambing groups, reflecting that single- and twin-bearing ewes responded differently in January, but the number of twinbearing ewes was small (n=4) in that month. MY differed significantly (P<0.01) among groups lambing in January (single MY {\textpm} SEM: twins MY {\textpm} SEM) (1605 {\textpm} 57: 1402 {\textpm} 71 g/d), March (1425 {\textpm} 38; 1802 {\textpm} 46) and June (1520 {\textpm} 43: 1951 {\textpm} 54). Despite having the lowest (P<0.05) mean pre-lambing live weight (62 {\textpm} 3 kg), ewes lambing in June produced the highest overall mean MY (1735 {\textpm} 48 g/d), whilst ewes lambing in March and January had mean pre-weaning live weights of 70 {\textpm} 2 kg (in both groups) and produced 1613 {\textpm} 42 g/d and 1504 {\textpm} 64 g/d respectively. The June{\textendash}lambing ewes gained weight (1.38 {\textpm} 1.19 kg) and condition score (0.39 {\textpm} 0.16 /d) whilst weight loss was significant (P<0.05) in the March (-9.82 {\textpm} 1.15 kg) and January (-7.78 {\textpm} 1.44 kg) groups between pre-lambing and weaning, as was change in condition score (March: -0.49 {\textpm} 0.16; January: -0.63 {\textpm} 0.19). Lamb birth weights did not differ between seasons but ADG (g/d  {\textpm} SEM) was highest (P<0.01) in June (0.262 {\textpm} 0.008), followed by March (0.238 {\textpm} 0.008) and January (0.202 {\textpm} 0.009). },
	issn = {1176-5283},
	author = {Peterson SW and Morel PCH and Kenyon PR and Morris ST}
}
@conference {41562,
	title = {Milk production in East Friesian-cross ewes lambing year round},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {173-177},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Milk production of groups of East Friesian cross ewes lambing at intervals of 73 days (i.e., five times per year: August (n = 21), November (n = 29), January (n = 13), March (n = 14) and June (n = 14)) was measured on alternate days in the first week post partum and at weekly intervals for nine weeks. Ewes with single and twin lambs were enrolled if they safely delivered the appropriate number of lambs indicated by previous scanning. Ewes and lambs were separated in the morning and ewes milked by machine following i.v. oxytocin (1 i.u.) and stripped by hand until empty. Ewes returned to pasture whilst lambs were housed and bottle-fed. At afternoon milking (after a precisely measured interval of about 6 h) milk yields were recorded. From that yield and the time interval, daily milk yields were calculated. Data were analysed using a mixed linear model for repeated measures. Twin-bearing ewes produced significantly more milk than single-bearing ewes (P < 0.001). Lactogenesis differed significantly (P < 0.001) between the lambing groups. Over the whole lactation, milk yield differed significantly (P < 0.001) between different lambing groups. Milk yields were highest following June lambing (2223 {\textpm} 35 g/day), followed by November (2107 {\textpm} 24 g/d), August (1932 {\textpm} 36 g/day), January (1826 {\textpm} 31 g/day) and March (1742 {\textpm} 30 g/day). A significant lambing group by rearing rank interaction (P < 0.001) indicated that single- and twin-bearing ewes responded differently to seasonal differences; ewes with twins increased milk yield proportionately more than ewes with singles in June, November and January.
KEYWORDS: milk yields; sheep; STAR system. },
	issn = {1176-5283},
	author = {Peterson SW and Kenyon PR and Morris ST and Lopez-Villalobos N and Morel PCH}
}
@conference {41224,
	title = {Effects of chromium picolinate on milk production and plasma insulin concentration in dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {60},
	year = {2000},
	month = {Jan},
	pages = {307-310},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {Chromium picolinate (CrPic) is a biologically active molecule in which chromium is chelated to an isomer of niacin. It is claimed to reduce plasma cholesterol levels in humans, pigs and hens and to have beneficial effects on muscle and fat composition of humans, pigs and lambs. The metabolic responses recorded in lambs were similar to those observed in cows of high genetic merit for milk production, suggesting that CrPic may increase milk yields by altering aspects of glucose and insulin metabolism. The trial reported in this paper is work investigated the effect of supplementation with CrPic on milk yields and plasma insulin concentration in multiparous Friesian dairy cows grazing pasture. Preliminary measurements of milk yield and composition were made during a pre-treatment period of 1 week in 59 mixed-age dairy cows before separation into four treatment groups balanced for previous milksolids yield, live weight and condition. Beginning at peak lactation, groups received 0, 5, 20, or 100 mg CrPic/day administered once daily by oral drenching. Milk yields were measured and samples taken at weekly intervals for compositional analyses (fat, protein and lactose \%). Blood samples were taken from the jugular at weekly intervals for insulin analysis. Chromium Picolinate had no effect on milk yield or composition. Plasma insulin concentrations did not differ between treatment groups. },
	issn = {1176-5283},
	author = {Peterson SW}
}
@conference {40937,
	title = {Control of Reproductive Success in Rabbits Using Bromocriptine.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {57},
	year = {1997},
	month = {Jan},
	pages = {222-224},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Feral rabbits impose a substantial environmental and economic cost in this country, causing pasture devastation over large areas of land, accelerating erosion and decreasing vegetation cover. Existing or potential methods of control have a high ethical cost, and there is a need to identify new methods of control. Manipulation of lactation, to enhance mortality and inhibit growth and development of the young, is a possible alternative strategy. Prolactin (PRL) is known to be important for establishment and maintenance of lactation in rabbits, and PRL secretion may be inhibited by administration of ergot alkaloids such as bromocriptine (CB154). These substances are orally active and so could potentially be used in baits. In order to determine whether CB154 could be used in baits, it is first necessary to establish the lowest effective dose. The objective of this study was to examine the relationships between dose of CB154 (initially administered systemically) and the growth and survival of kits. Sixteen pregnant New Zealand White does were divided into four treatment groups receiving different doses (mg/kg live weight/d) of CB154 ("low"(L), 0.2; "medium"(M), 0.4; "high"(H), 0.8; and control (C), 0). From day 3 of lactation, does were injected once daily with CB154 or excipient. Treatment continued until day 14 or until the death of all the kits, whichever came first. There were significant treatment effects on the proportion of kit deaths on all measurement days. By day 17, kit mortalities were: C, 20\%; L 42\%; M, 64\%; H, 71\%;) (P<0.05). The weight gain of the surviving kits from day 3 to 8 did not differ significantly between treatment groups, but kit weight gain day from days 8 to 13 showed a significant treatment effect (P<0.01) (control, 83.7{\textpm}11.4g; low, 18.7{\textpm}11.4g; medium, 33.5{\textpm}17.2g; high -0.8{\textpm}14.9g). Results are discussed in relation to the possible use of bromocriptine as a bait to control reproductive success, and to the fact that these rabbits were much less sensitive to bromocriptine than previously published studies would suggest. },
	issn = {1176-5283},
	author = {Cottam YH and Peterson SW and McCutcheon SN}
}
@conference {40839,
	title = {Seasonal effects on fetal growth in sheep},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {297-300},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Previous studies have shown that autumn-born lambs are lighter (by  0.4 to 1.0 kg) at birth than spring-born lambs, an effect which is associated  with impaired placental development in ewes mated to lamb in the autumn.  As previous studies have focused on near-term fetal weights and birth  weights, the objective of this study was to determine the pattern of growth  throughout gestation in lambs destined to be born in the autumn or spring,  and to examine associated changes in placental development. Mature N.Z.  Romney ewes were randomly assigned to groups mated in December (n=23)  or March (n=28) and managed on pasture in both seasons for similar live- weight profiles from mating to day 140 of gestation. Ewes were slaughtered  at day 56, 84, 112 or 140 of gestation, and measures of fetal and placental  weight were determined. Fetal weights (kg) of December- versus March- mated ewes were: d56 (0.040 },
	issn = {1176-5283},
	author = {McCoard SA and Peterson SW and Jenkinson CMC and Campbell JW and McCutcheon SN}
}
@conference {40578,
	title = {The effect of peripartum administration of ovine prolactin on lactogenesis in autumn-lambing ewes.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {115-118},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Two routes of oPRL supplementation were used to elevate peripheral or  
local concentrations of PRL in autumn-lambing ewes which, based on previous  
results, were expected to have low plasma PRL concentrations and milk yields  
relative to spring-lambing ewes.  Administration of 10 mg oPRL directly into  
the gland or subcutaneous injection of 0.5 mg/kg oPRL did not increase the  
milk yields, or change the composition of milk, compared to controls.  These  
results suggest that the circulating and intramammary concentrations of PRL in  
autumn-lambing ewes are not limiting lactogenesis.  However, because the  
plasma prolactin concentration in the ewes was unexpectedly high, it was not  
possible to reach firm conclusions regarding possible effects of supplementary  
oPRL in ewes with naturally low plasma PRL concentrations.  Nevertheless,  
the results indicate that raising the intramammary concentration of PRL around  
the time of parturition, in ewes with circulating PRL concentrations  
characteristic of normal spring-lambing ewes, does not enhance lactogenesis. 
 },
	issn = {1176-5283},
	author = {Peterson SW and MacKenzie DDS and McCutcheon SN and Lapwood KR}
}
@conference {40605,
	title = {The effects of season on placental development and fetal growth in sheep},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {227-230},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Autumn-born lambs have been reported to have lower birth weights  
than spring-born lambs by 0.4 to 1.0 kg, but the physiological basis of this  
difference is unknown.  This study examined the effects of season on fetal  
growth and placental development independent of the confounding effects of  
maternal nutrition.  Romney ewes (aged 5 and 6 years) were randomly  
allocated to groups mated in December (n=13) or March (n=13 with a similar  
live weight at mating (55.6{\textpm}1.8 vs 55.7{\textpm}1.9 kg, mean{\textpm}SE, P>0.10) and  
managed for a similar live weight at day 140 of gestation (62.5{\textpm}1.8 vs 62.9{\textpm}1.9  
kg, P>0.10).  At day 140 of gestation, measures of fetal growth and placental  
development, adjusted for litter size, were (December- vs March-mated):  
individual fetal weight (4.15{\textpm}0.16 vs 5.07{\textpm}0.16 kg, P<0.001); total fetal weight  
per ewe (6.42{\textpm}0.18 vs 7.14{\textpm}0.22 kg, P<0.01); caruncle number (114.5{\textpm}4.1 vs  
121.0{\textpm}4.2, P>0.10); placentome number (89.4{\textpm}4.2 vs 106.9{\textpm}4.3, P<0.01);  
caruncle occupancy, i.e. number of placentomes/number of caruncles  
(0.79{\textpm}0.03 vs 0.88{\textpm}0.03, P<0.05); and total placentome weight (564.7{\textpm}34.0 vs  
679.0{\textpm}34.9 g, P<0.05).  These results suggest that seasonal differences in birth  
weight of lambs are mediated not by differences in maternal nutrition but rather  
by a direct seasonal effect on placental size (specifically the formation of  
placentomes and hence total placental weight). 
 },
	issn = {1176-5283},
	author = {Jenkinson CMC and Peterson SW and MacKenzie DDS and McCutcheon SN}
}
@conference {40269,
	title = {Milk production and plasma prolactin levels in spring- and autumn-lambing ewes},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {50},
	year = {1990},
	month = {Jan},
	pages = {483-485},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Methane and nitrous oxide produced by farmed ruminants may cause  over one third of the potential greenhouse warming which can be  attributed to New Zealand. This is a result of high populations of  domestic ruminants (mainly sheep and cattle), and the large warming  potential of methane and nitrous oxide. New Zealand{\textquoteright}s total greenhouse  gas production is an insignificant component of the global total, but  this fact cannot be used as a reason to ignore New Zealand{\textquoteright}s  contribution. International negotiations have commenced with the aim of  producing a treaty to limit global greenhouse gas production by  ruminants in New Zealand, and identifies areas needing further research.  It concludes that; (1) the accuracy of estimate of greenhouse gas  emissions from agriculture needs to be improved; (2) technology to  reduce greenhouse gas emissions from ruminants should be developed for,  and applied to, New Zealand farming systems; and (3) that equitable  methods of implementing limitation policies need to be investigated.  },
	issn = {1176-5283},
	author = {Peterson SW and MacKenzie DDS and McCutcheon SN}
}
@conference {40156,
	title = {Liver catalase in Southdown sheep selected for high and low backfat depth},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {49},
	year = {1989},
	month = {Jan},
	pages = {143-146},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Four pairs of shorn Cashmere-type goats, fed at 1.5 x maintenance, were exposed to air temperatures between 5},
	issn = {1176-5283},
	author = {Peterson SW and Purchas RW}
}
@conference {39917,
	title = {The breath-test for sheep: a possible means of identifying lean genotypes},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {44},
	year = {1984},
	month = {Jan},
	pages = {205-208},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The effect of Ralgro on growth and carcass composition was examined in 3 lamb trials, in young and 15-month old bulls and in spayed and entire heifers. There was no consistent growth response to Ralgro in any of the trials, except for the spayed heifers. Increased meat percentage from Ralgro was found only in young bulls. Aggressive bull behaviour was controlled by Ralgro only in young bulls from April-July at approximately 8 to 11 months of age.},
	issn = {1176-5283},
	author = {Peterson SW}
}
