@article {3672,
	title = {INVITED PAPER: Has progress been made in increasing the eco-efficiency of livestock systems?},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {79},
	year = {2019},
	month = {07/2019},
	pages = {43-55},
	address = {Palmerston North},
	abstract = {Current challenges for New Zealand livestock farming systems include soil erosion, water quality, greenhouse gases (GHG), and indigenous biodiversity. Industry data were used to quantify changes in emissions of the major livestock sectors from 1990, by examining inputs (e.g., livestock numbers, fertiliser) and outputs (e.g., GHG, nitrate leaching (N), saleable products) using Overseer. Productivity gains were significant for extensive sheep and beef farms, from 107 (meat + wool) kg/ha in 1990 up to 167 kg/ha in 2012. Gains were modest for intensive sheep and beef farms in this period (from 219 up to 238 kg/ha). Extensive sheep and beef increased from 3370 to 3997 kg/ha of GHG and N leached from 12 to 14 kg/ha. Intensive sheep and beef farm systems showed negligible change in N leached, while GHG emissions rose from 4167 to 4470 kg CO2-e/ha. North Island dairy farms increased from 672 to 1000 kg milk solids/ha, from 11341 to over 12000 kg CO2-e/ha of GHG and N leached increased from 44 up to 50 kg/ha. All farm systems delivered more product in proportion to GHG and N per hectare per year. Potential scenarios for the sheep and beef sector into the future were investigated, by examining the influence of ongoing increases in reproduction of ewes, lamb growth, hogget lambing and moving away from breeding cows and older cattle could have on future productivity gains and environmental impact. With the area in pasture likely to continue to decline in extensive livestock systems as outstanding environmental issues are addressed, the potential exists to offset > 20\% of livestock GHG emissions. Intensive systems have fewer opportunities to make production and eco-efficiency gains, with less scope to reduce their impact. },
	issn = {1176-5283},
	author = {Mackay AD and Scobie DR and Rhodes TR and Devantier B}
}
@conference {41979,
	title = {Ultrasonic measurement of backfat and muscling in sheep selected for parasite-related traits},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {198-203},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {This paper reports on backfat depth and muscling comparisons of sheep selected for nematode parasiterelated traits. Results are from two AgResearch projects, the first located at Kaitoke Farm (Upper Hutt), in which experimental Romney lines wereselectively bred for susceptibility (S) or resistance (R) to nematode infection (high or low faecal egg count), or for resilience to nematode challenge whilst maintaining acceptable growth with minimal anthelmintic treatment (RL line); these lines grazed alongside an unselected control line (C). The second project was located at Ballantrae (Northern Wairarapa), in which Romney breeding lines were selected for resilience, with two replicate farmlets under {\textquoteright}Conventional{\textquoteright} parasite management (with anthelmintic treatment), and with two further replicate farmlets under {\textquoteright}Low-Chemical{\textquoteright} management. The four replicate lines at Ballantrae were serviced by rams of equivalent genetics, from elite RL-line sires bred at Kaitoke or Ballantrae. Ultrasonic backfat depth and eye muscle dimensions (length, depth and area) of ewe lambs from each project were assessed at 8-9 months of age (234 C-, S-, R- and RLline lambs born in 2003 at Kaitoke, and 154 resilient lambs born in 2004 at Ballantrae). Adjustments were made for significant fixed effects including covariate adjustment for live weight. No significant differences were found among the R, C and RL lines for either trait, but the S line had 5-10\% smaller eye-muscle dimensions (P < 0.05) than the other lines following an extended period of natural nematode challenge with minimal drench treatment. The two replicate lines under Low-Chemical management were 3.8 {\textpm} 0.6 kg (11.8\%) lighter in May than the replicates under Conventional management (P < 0.001). After adjustment for live weight, lambs in the Conventional treatments had 15\% larger eye-muscle areas (P < 0.001) but not backfat depths than those in the Low-Chemical treatments. Results suggest that muscle dimensions of the Sline lambs were more affected than those of their R-line counterparts by parasite infection, whilst the C-, R- and RL-line lambs did not differ significantly. At Ballantrae, even at equivalent live weights, the two Conventional replicates had more muscling but not fat depth than the two Low-Chemical replicates.},
	issn = {1176-5283},
	author = {Wheeler M and Morris CA and Bisset SA and Vlassoff A and Mackay AD and West CJ and Devantier BP}
}
@conference {41525,
	title = {Resilience to nematode parasite challenge in industry and AgResearch selection flocks},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {300-303},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {A large-scale industry project on the resilience of lambs to nematode parasite challenge was undertaken in 2001/02 and 2002/03, to evaluate the feasibility of recording standardised age at first drench (StAge) and postweaning weight gain under nematode challenge, and to estimate genetic differences among flocks. The project involved 15 Romney flocks from two ram breeding groups, with some flocks having been part of an earlier AgResearch study of the genetics of resilience traits. This provided the opportunity to assess any correlated changes in resilience over time (where direct selection over that time period in the industry flocks had been applied to productivity traits, but not to resilience), and to compare the industry performance with AgResearch Resilient-selected and Control lines. The overall estimates of heritability for StAge and weight gain (2 time periods: Gain1 and Gain2) were 0.14 {\textpm} 0.014, 0.30 {\textpm} 0.015 and 0.15 {\textpm} 0.007, respectively. Genetic correlations between StAge and either Gain1 or Gain2 were 0.30 {\textpm} 0.06 and 0.41 {\textpm} 0.06, respectively. Genetic differences for all traits between the two industry groups were small and not significant. The genetic differences of the current industry-group means (all 15 flocks) above the AgResearch Control line were small (0.8 days, 0.5 kg and 0.9 kg, respectively). In comparison, the genetic differences of the AgResearch Resilient-selected line over the Control line after eight years of selection were 19 days, 0.7 kg and 1.4 kg (11, 8.3 and 9.6\% of the industry means). The results confirm that while selection for increased resilience is feasible (although very time-consuming) under commercial conditions, a ram breeder would need to consider an index approach which combined production and resilience traits, to make best use of his animal resources. },
	issn = {1176-5283},
	author = {Morris CA and Amyes NC and Bisset SA and Mackay AD}
}
@conference {41501,
	title = {Understanding shepherding within lambing, and organic farming systems through acknowledging cultural, community and individual influences},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {183-187},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {The way we farm depends on the species farmed, the environment, and on our beliefs, prejudices and expectations. A model was developed to consider cultural influences, community ethics, and individual goals to help understand shepherding and organic farming. Assisting sheep at lambing is reinforced by cultural expectations of what shepherds should do. Different management strategies are used depending on the sheep, their environment, and the costs and practicalities of supervision. Finally, the weight given to different factors may depend on the motivation of individuals in deciding to "live with the flock" or find better ways of managing lambing. Reflecting the different goals of agriculture, individuals were motivated to convert to organic farming by economic returns, the environment, chemical use, food safety and quality, animal health and welfare, and a desire to maintain rural communities. The safety of chemicals, food quality, and the environment are central to understanding the value of organics to the community. Finally, organic farming is informed by stories of {\textquotedblleft}being at one with nature{\textquotedblright} An understanding of the different beliefs that inform us of the way farming is, or should be, may result in a greater shared understanding of complex issues, and more equitable farming practices. },
	issn = {1176-5283},
	author = {Fisher MW and Small BH and Mackay AD and Kenny GJ and Jerebine BC and Parminter TG}
}
@conference {41320,
	title = {Moving towards low-chemical farming with sheep and cattle: potential of a breeding approach},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {81-85},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {On livestock farms in New Zealand, some farmers are changing their sheep, beef cattle or dairy cattle enterprises towards specialisation in low-chemical or organic systems. A vital part of the animal{\textquoteright}s ability to perform under these systems is having the disease resistance genes available (or some other means to cope), as well as having the production and quality traits. In practice, animals are likely to be under a number of disease challenges at any one time, so breeders must concentrate their genetic selection practices on the most important health problems. Other (non genetic) means may also be critical in helping to protect the animal. This paper reviews the New Zealand evidence for genetic differences in resistance to various important diseases or metabolic stresses in sheep and cattle, and shows that genetic selection could be applied successfully if required. The paper also discusses some of the challenges in realising the goal of low chemical farming, such as finding a source of rams, bulls or semen. The diseases/stresses that are covered are: in sheep, nematode parasites, dags, fly strike, facial eczema (FE) and ryegrass staggers (RGS); in dairy cattle, mastitis, bloat, FE, RGS, nematode parasites and hypomagnesaemia; in beef cattle, RGS, nematode parasites and hypomagnesaemia. Some breed differences are mentioned, but at present the main New Zealand evidence of genetic variation is derived from heritability estimates. In sheep, average heritability estimates are: nematode parasites in lambs, 0.23 (repeatability 0.30); dags, 0.20 (repeatability 0.4); fly strike, 0.26 (Australian data); FE, 0.45; and RGS, up to 0.17, depending on the challenge level (repeatability 0.28). Corresponding heritability estimates in cattle are: clinical mastitis 0.06 (or somatic cell count 0.09); bloat 0.19 (repeatability 0.45); FE 0.56; RGS no published estimate; nematode parasites in calves 0.32; hypomagnesaemia 0.15. The simple mean of heritability estimates for 10 traits in sheep and/or cattle was 0.26 (0.28 excluding the outlier, mastitis, at 0.06), suggesting that responses should be achieved if directional selection is applied after performance or progeny testing. Knowing the genetic correlations among these disease traits is also important, because of the multiple disease challenges likely, but few of these correlations have yet been documented. Opportunities for ranking sires using the principles of Group Breeding Schemes or Sire Reference Schemes are discussed. },
	issn = {1176-5283},
	author = {Morris CA and Mackay AD}
}
@conference {41260,
	title = {Genetic studies of resilience of Romney sheep to nematode challenge in New Zealand},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {92-95},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {"Resilience" in sheep can be defined as the ability to withstand nematode challenge, and to maintain acceptable health and productivity, with minimal reliance on anthelmintic treatment. One heritable component trait is Total Drench Requirement (TDR), which is measured in lambs managed on a regime of "drench-on-demand" (where Trichostrongylus and Ostertagia are the predominant nematode genera in New Zealand sheep). A breeding experiment was established in 1994, selecting for increased resilience in Romney lambs. Currently, breeding ewes in the experiment are subdivided between Ballantrae, where four genetically equivalent sub-groups graze separate farmlets year-round, under Non-Chemical versus Conventional management (AgResearch{\textquoteright}s Low-Chemical Farming Systems Programme), and Wallaceville, where an Elite Resilient line was re-established in 1999 alongside the Control Faecal Egg Count (FEC) line. Selection responses up to 1999/00 in the Elite Resilient-line lambs (relative to the Control line) included a 27\% greater post-weaning weight gain (GAIN: Dec. to Apr.), a 0.48 unit reduction in dags, and a 45\% reduction in TDR (Dec. to Apr.). A favourable genetic correlation (-0.54) was recorded between TDR and GAIN in lambs, whilst that between TDR and log FEC was -0.17 (not significant). Mean autumn weights in lambs at Ballantrae were 5.8 kg (18\%) lower in the Non-Chemical than Conventional treatment groups (P<0.01). Through intense genetic selection, 51\% of Elite-line ram lambs are now resilient enough for low-chemical or organic production systems. },
	issn = {1176-5283},
	author = {Morris CA and Bisset SA and Vlassoff A and Mackay AD and Betteridge K and Alderton MJ and West CJ and Devantier BP}
}
