Post-slaughter alimentary tract measures were collected from eight-month-old ram lambs during routine culling of sheep divergently selected for methane yield. Measures from 142 and 132 lambs from the high and low methane lines respectively were collected over five years. Low CH4 animals had lighter reticulo-rumen full, empty and contents weights (P<0.05), but tended to have longer rumen papillae (P=0.06). Preliminary heritability estimates for reticulo-rumen components and papillae traits were significantly different from zero, ranging from 0.09 to 0.25. Results validate earlier findings that differences in the anatomical characteristics of the alimentary tract are associated with methane emissions and suggest that there is a significant host genetic component, warranting further investigation.

Global agreements in place to reduce methane emissions in livestock are a potential threat to food security. Successful but independent breeding strategies for improved production and lower methane are in place. The unanswered questions are whether these strategies can be combined and how they impact one another, physically and economically. The New Zealand economy is largely dependent on pastoral agriculture from grazing ruminants. The sheep industry produces ∼20 million lamb carcasses for export each year primarily from grass. Methane emitted from the fermentation of forage by grazing ruminants accounts for one-third of all New Zealand’s greenhouse gas emissions. Here, we use sheep selection lines bred for divergent methane production and large numbers of their relatives to determine the genetic and phenotypic correlations between enteric methane emissions, carcass yield, and meat quality. The primary objectives were to determine whether previously shown physiological differences between methane selection lines (differing by ∼12% in methane) result in a negative impact on meat production and quality by measuring close relatives. The results show no negative effects of breeding for lowered methane on meat and carcass quality. Gross methane emissions were highly correlated with liveweight and measures of carcass weight and negatively correlated with dressing-out percentage and fat yield (GR). Trends were similar but not significant for methane yield (g CH4/kg DMI). Preliminary evidence, to date, shows that breeding for low methane may result in animals with higher lean yields that are economically favorable even before carbon costs and environmental benefits are taken into account. These benefits were seen in animals measured for methane on fixed intakes and require validation on intakes that are allowed to vary.

A catch phrase within animal genetics is that there is as much variation within a breed as there is between breeds. The New Zealand Perendale Progeny Test has been conducted on North and South Island sites since 2010 with the aim of investigating genetic variability for carcass traits. A total of 51 sires, from 27 studs have been assessed, with sires selected from the top 20% of the Perendale across-flock Dual Purpose Index SIL evaluation. Within each year/site lambs generated were born within a week (ewes naturally synchronised pre-mating), and slaughtered on the same day. A total of 2318 male progeny have been generated and slaughtered through Alliance with traits measured including weight traits, carcass dimensions, VIAscan® traits, carcass pH, carcass fat colour and, in some years, colour stability of chilled aged loins, subjective marbling score and meat tenderness. Genetic parameters were estimated with ASREML; carcass weight was fitted as a co-variate for carcass traits (excluding carcass weight). The heritability estimates for all traits were moderate to high, with the lowest of 0.22 ± 0.07 for VIAscan® GR, and the highest, for pH, of 0.44 ± 0.09, with the majority between 0.22 and 0.43. The high estimate for slaughter plant measured pH was supported by the 0.59 ± 0.17 estimate for pH measured in the laboratory on those samples which were measured for colour stability. The phenotypic correlations between traits were generally well estimated with small standard errors for the majority of trait combinations. The genetic correlations were not as well estimated with standard errors greater than 0.10 for most traits combinations, but despite the large standard errors some were still significant, and in general agreement with values the literature. The progeny test has therefore demonstrated significant genetic variability for the range of carcass traits assessed in this study within the Perendale breed.

The objective of this study was to determine the genetic parameters of methane (CH4) emissions and their genetic correlations with key production traits. The trial measured the CH4 emissions, at 5-min intervals, from 1225 sheep placed in respiration chambers for 2 days, with repeat measurements 2 weeks later for another 2 days. They were fed in the chambers, based on live weight, a pelleted lucerne ration at 2.0 times estimated maintenance requirements. Methane outputs were calculated for g CH4/day and g CH4/kg dry matter intake (DMI) for each of the 4 days. Single trait models were used to obtain estimates of heritability and repeatability. Heritability of g CH4/day was 0.29 ± 0.05, and for g CH4/kg DMI 0.13 ± 0.03. Repeatability between measurements 14 days apart were 0.55 ± 0.02 and 0.26 ± 0.02, for the two traits. The genetic and phenotypic correlations of CH4 outputs with various production traits (weaning weight, live weight at 8 months of age, dag score, muscle depth and fleece weight at 12 months of age) measured in the first year of life, were estimated using bivariate models. With the exception of fleece weight, correlations were weak and not significantly different from zero for the g CH4/kg DMI trait. For fleece weight the phenotypic and genetic correlation estimates were −0.08 ± 0.03 and −0.32 ± 0.11 suggesting a low economically favourable relationship. These results indicate that there is genetic variation between animals for CH4 emission traits even after adjustment for feed intake and that these traits are repeatable. Current work includes the establishment of selection lines from these animals to investigate the physiological, microbial and anatomical changes, coupled with investigations into shorter and alternative CH4 emission measurement and breeding value estimation techniques; including genomic selection.

This paper investigates genetic control of redness for 8 week chill aged lamb. Heritability of CIE a* values (Commission Internationale de l’ Eclairage, 1976, a measure of redness) has been estimated from 18,913 carcasses of crossbred lambs born 2003-2010. Colour was recorded at 24, 48, 96 and 168 hours post display wrapping. Heritability estimates for the combined dataset were 0.55±0.03, 0.57±0.03, 0.58±0.03 and 0.29±0.03 respectively for the 4 time points, indicating that the colour of chill aged lamb loins is under moderate genetic control.

Arapawa sheep are a feral breed found on Arapawa Island in the Marlborough Sounds, New Zealand. Their origin is not documented, but it is thought to be one of the oldest feral flocks in New Zealand dating back to approximately mid 1800s (Orwin et al., 1984). There are numerous theories of how Arapawa sheep came to be on the island and what breed they originated from. The most commonly recognised origin is that the sheep have derived from an Australian Merino flock that was introduced and farmed on the island in 1867. Another suggestion is that Arapawa sheep are descendants from mixed breed European sheep that were brought to the island to be farmed by whalers who originally occupied the island in the 1820s. Perhaps the most curious theory is that the sheep were dropped off on the island by Spanish galleons in the 1500s (New Zealand Rare Breeds Conservation Society, 2002). Phenotypically, Arapawa sheep are unique from other domestic sheep in New Zealand as described by Orwin et al. (1984). Arapawa sheep have predominantly black skin and wool colouration, typically with a white crown which can extend down the face and throat, with a white area on the distal part of the tail. However, totally white individuals also exist. Ewes are generally polled with some growing small scurs. Males characteristically have large curled horns with approximately 10% being polled. Arapawa sheep are small bodied with long legs. On average males weigh 51 kgs and females 38 kg in the wild. Fleece weight tends to be low at approximately 2 kg per annum with shedding occurring in some animals. The wool is highly crimped with a mean fibre diameter of approximately 22 μm (Orwin, et al.,1984). As a feral breed they are reputedly very resistant to footrot, flystrike and parasites (Litherland et al., 1992). Ewes can ovulate throughout the year, lambs and are born small with a hairy coat similar to that of a Merino (Schinckel., 1954), which is later shed. New Zealand has significant barriers to importation of new breeds. It is therefore of interest to determine the origin of these sheep. Potentially they may be a reservoir of unique gene variants for mainstream farmed animals. They also act as an excellent documented reversion to a feral existence because their island location has restricted ongoing gene transfer from domesticated sheep. This isolation allows investigation of genes that have been naturally selected during this process, provided matching animals of a related domesticated control breed are available. Finally, as with all feral breeds the true level of inbreeding is unknown. This is important in long term conservation strategies. The current work attempts to identify their origin and current inbreeding level and is part of a longer term project to identify what genetic selection has occurred during the reversion to a feral existence.

Arapawa sheep are a feral breed found on Arapawa Island in the Marlborough Sounds, New Zealand. Their origin is not documented, but it is thought to be one of the oldest feral flocks in New Zealand dating back to approximately mid 1800s (Orwin et al., 1984). There are numerous theories of how Arapawa sheep came to be on the island and what breed they originated from. The most commonly recognised origin is that the sheep have derived from an Australian Merino flock that was introduced and farmed on the island in 1867. Another suggestion is that Arapawa sheep are descendants from mixed breed European sheep that were brought to the island to be farmed by whalers who originally occupied the island in the 1820s. Perhaps the most curious theory is that the sheep were dropped off on the island by Spanish galleons in the 1500s (New Zealand Rare Breeds Conservation Society, 2002). Phenotypically, Arapawa sheep are unique from other domestic sheep in New Zealand as described by Orwin et al. (1984). Arapawa sheep have predominantly black skin and wool colouration, typically with a white crown which can extend down the face and throat, with a white area on the distal part of the tail. However, totally white individuals also exist. Ewes are generally polled with some growing small scurs. Males characteristically have large curled horns with approximately 10% being polled. Arapawa sheep are small bodied with long legs. On average males weigh 51 kgs and females 38 kg in the wild. Fleece weight tends to be low at approximately 2 kg per annum with shedding occurring in some animals. The wool is highly crimped with a mean fibre diameter of approximately 22 μm (Orwin, et al.,1984). As a feral breed they are reputedly very resistant to footrot, flystrike and parasites (Litherland et al., 1992). Ewes can ovulate throughout the year, lambs and are born small with a hairy coat similar to that of a Merino (Schinckel., 1954), which is later shed. New Zealand has significant barriers to importation of new breeds. It is therefore of interest to determine the origin of these sheep. Potentially they may be a reservoir of unique gene variants for mainstream farmed animals. They also act as an excellent documented reversion to a feral existence because their island location has restricted ongoing gene transfer from domesticated sheep. This isolation allows investigation of genes that have been naturally selected during this process, provided matching animals of a related domesticated control breed are available. Finally, as with all feral breeds the true level of inbreeding is unknown. This is important in long term conservation strategies. The current work attempts to identify their origin and current inbreeding level and is part of a longer term project to identify what genetic selection has occurred during the reversion to a feral existence.