Pollott, G E; Karlsson, L J E; Eady, S; Greeff, J C
Fecal egg count (FEC) has been widely used as an indicator of host resistance to gastrointestinal parasites in sheep and has been shown to be a heritable trait. Two other possible indicators of parasites, dag score (DS; accumulated fecal material) and fecal consistency score (FCS), were investigated in this study, along with BW. All four traits were studied to see how heritability and genetic correlations varied with age from weaning (4 mo) to hogget age (approximately 400 d). More than 1,100 lambs, the offspring of 37 rams, were recorded eight times between weaning (3 to 5 mo of age) and hogget age (13 to 18 mo of age) on two farms. Sire models were fitted to the data from each trait at each recording and in a repeatability model involving the whole data set. Overall, the heritabilities were 0.28+/-0.072 (FEC), 0.11+/-0.036 (DS), 0.12+/-0.036 (FCS), and 0.23+/-0.070 (BW). By fitting random regression models to the time-series data, it was possible to see how these heritability values varied as the lambs aged, from weaning to hogget age. The heritability of FEC rose from 0.2 at weaning to 0.65 at 400 d. Dag score had a higher heritability (0.25) in the middle of the age range and a low value at weaning (<0.1) and hogget age (0.16). The heritability of FCS was low, with a value of 0.2 at weaning reducing to 0.05 as the animals aged. Body weight had zero heritability at weaning, which rose to greater than 0.6 at hogget age. Most traits had low genetic correlations between them, the only exception being that between FCS and DS (0.63). Most genetic correlations varied little over the age range with the exception of FEC and BW, which fell from 0 at weaning to -0.63 at hogget age. Whereas FCS and DS may be good indicators of scouring, they are very different from FEC as an indicator of host resistance to gastrointestinal parasites.
Greeff, J C; Safari, E; Fogarty, N M; Hopkins, D L; Brien, F D; Atkins, K D; Mortimer, S I; van der Werf, J H J
Genetic parameters for carcass and meat quality traits of about 18-month-old Merino rams (n = 5870), the progeny of 543 sires from three research resource flocks, were estimated. The estimates of heritability for hot carcass weight (HCW) and the various fat and muscle dimension measurements were moderate and ranged from 0.20 to 0.37. The brightness of meat (colour L*, 0.18 +/- 0.03 standard error) and meat pH (0.22 +/- 0.03) also had moderate estimates of heritability, although meat relative redness (colour a*, 0.10 +/- 0.03) and relative yellowness (colour b*, 0.10 +/- 0.03) were lower. Heritability estimates for live weights were moderate and ranged from 0.29 to 0.41 with significant permanent maternal environmental effects (0.13 to 0.10). The heritability estimates for the hogget wool traits were moderate to high and ranged from 0.27 to 0.60. The ultrasound measurements of fat depth (FATUS) and eye muscle depth (EMDUS) on live animals were highly genetically correlated with the corresponding carcass measurements (0.69 +/- 0.09 FATC and 0.77 +/- 0.07 EMD). Carcass tissue depth (FATGR) had moderate to low genetic correlations with carcass muscle measurements [0.18 +/- 0.10 EMD and 0.05 +/- 0.10 eye muscle area (EMA)], while those with FATC were negative. The genetic correlation between EMD and eye muscle width (EMW) was 0.41 +/- 0.08, while EMA was highly correlated with EMD (0.89 +/- 0.0) and EMW (0.78 +/- 0.04). The genetic correlations for muscle colour with muscle measurements were moderately negative, while those with fat measurements were close to zero. Meat pH was positively correlated with muscle measurements (0.14 to 0.17) and negatively correlated with fat measurements (-0.06 to -0.18). EMDUS also showed a similar pattern of correlations to EMD with meat quality indicator traits, although FATUS had positive correlations with these traits which were generally smaller than their standard error. The genetic correlations among the meat colour traits were
Kennedy, C; Buckley, D J; Kerry, J P
Longissmus dorsi loins were removed from Suffolk cross-breed lambs (4-9 months) and hoggets (15-20 months). The effect of package gas composition was investigated by packaging loins with gas mixtures containing 80:20:0, 60:20:20 and 60:40:0/O(2):CO(2):N(2) with a 2:1 headspace to meat volume ratio. The most effective gas mixture for prolonging shelf-life was used to study the effect of different headspace to meat volume ratios. Loins were packaged with a headspace to meat volume ratio of 2:1, 1.5:1 or 1:1. All modified atmosphere (MA) packs were held under refrigerated display conditions (4 °C, 616 lx) for 12 days. Loins were assessed for microbial, oxidative and colour stability and headspace composition every 3 days. The 80:20:0/O(2):CO(2):N(2) gas composition and the 2:1 headspace to meat volume ratio was the most effective packaging combination at maintaining and prolonging the attractive red colour of MA packaged lamb and hogget meat. 80:20:0/O(2):CO(2):N(2) resulted in significantly (p<0.01) higher Hunter a values in lamb. The 2:1 ratio gave higher visual assessment values in lamb and higher Hunter `a' values for hogget meat throughout the trial. The 2:1 ratio was the most effective at decreasing Pseudomonas and increasing the numbers of lactic acid bacteria in the total microbial load in both lamb and hogget meat. Lipid oxidation in lamb and hogget meat occurred at a slower comparative rate than discolouration or microbial growth and was not the major determinant of shelf-life. The 2:1 headspace to meat volume ratio was most effective at maintaining the initial gas mix in both lamb and hogget MA packs.
Smith, K C; Brown, P J; Barr, F J
Congenital abnormalities of the reproductive tract of male sheep were surveyed at three abattoirs in the south west of England during the period June 2000-January 2004. A total of 7307 rams were examined [6521 lambs (prepubescent) and hoggets (aged from their first autumn after birth until first shorn) and 786 adult rams mature rams that had been exposed to ewes]. A total of 156 congenital lesions were detected, 87 of which occurred in lambs. Testicular hypoplasia was the most common lesion occurring in 69 lambs as well as eight hoggets ('microtestes' were recognized in nine other animals in which the testis was disproportionately smaller than the epididymis). The second most common lesion found was notched scrotum occurring in 34 animals (27 young rams and seven adults). Some cases of notched scrotum were accompanied by hypospadias which was seen in a total of seven lambs and eight hoggets. Other lesions, detected in five or less animals (less than approximately 0.05% of the animals examined), included cryptorchidism and various abnormalities of the epididymis (segmental aplasia of the epididymis, blind efferent ducts and epididymal cyst) and congenital scrotal hernia. The overall prevalence of congenital lesions of 2.21% emphasizes the importance of undertaking breeding soundness examinations of young rams before they are put with the flock.
Paganoni, B; Rose, G; Macleay, C; Jones, C; Brown, D J; Kearney, G; Ferguson, M; Thompson, A N
The Australian sheep industry aims to increase the efficiency of sheep production by decreasing the amount of feed eaten by sheep. Also, feed intake is related to methane production, and more efficient (low residual feed intake) animals eat less than expected. So we tested the hypothesis that more efficient sheep produce less methane by investigating the genetic correlations between feed intake, residual feed intake, methane, carbon dioxide, and oxygen. Feed intake, methane, oxygen, and carbon dioxide were measured on Merino ewes at postweaning (1,866 at 223 d old), hogget (1,010 sheep at 607 d old), and adult ages (444 sheep at 1,080 d old). Sheep were fed a high-energy grower pellet ad libitum for 35 d. Individual feed intake was measured using automated feeders. Methane was measured using portable accumulation chambers up to 3 times during this feed intake period. Heritabilities and phenotypic and genotypic correlations between traits were estimated using ASReml. Oxygen (range 0.10 to 0.20) and carbon dioxide (range 0.08 to 0.28) were generally more heritable than methane (range 0.11 to 0.14). Selecting to decrease feed intake or residual feed intake will decrease methane (genetic correlation  range 0.76 to 0.90) and carbon dioxide ( range 0.65 to 0.96). Selecting to decrease intake ( range 0.64 to 0.78) and methane ( range 0.81 to 0.86) in sheep at postweaning age would also decrease intake and methane in hoggets and adults. Furthermore, selecting for lower residual feed intake ( = 0.75) and carbon dioxide ( = 0.90) in hoggets would also decrease these traits in adults. Similarly, selecting for higher oxygen ( = 0.69) in hoggets would also increase this trait in adults. Given these results, the hypothesis that making sheep more feed efficient will decrease their methane production can be accepted. In addition, carbon dioxide is a good indicator trait for feed intake because it has the highest heritability of the gas traits measured; is cheaper, faster, and
Thompson, G M; Jess, S; Gordon, A W; Murchie, A K
Sticky traps were mounted on heifers and sheep to assess Culicoides spp. (Diptera: Ceratopogonidae) host preference. Initially, four coloured 200-cm(2) sticky traps (white, clear, yellow and blue) were attached to the backs of each of ten Friesian heifers that were released into open pasture for 24 h, repeated on six occasions. More Obsoletus group Culicoides were caught on the white and clear traps than on the yellow and blue. Trap position on the right or left flank also affected midge catch, probably due to heifer orientation in the field. Next, six Friesian heifers and six Charollais hoggets each had one clear and one white sticky strap attached to their backs for one 24-h period per week, repeated for 24 weeks. Overall, Obsoletus group Culicoides comprised 91.8% (n = 5, 955) of the midge catch but there was no evidence of host preference, either discounting or including host live weight in the analyses. However, Pulicaris group Culicoides did demonstrate a significant host preference for sheep, providing that the analysis was adjusted for live weight. On heifers, the Pulicaris group comprised 7.5% of biting midges caught, whereas on hoggets, it comprised 12.7%.
Wang, Peng-Yu; Guanque, Zha-Xi; Qi, Quan-Qing; De, Mao; Zhang, Wen-Guang; Li, Jin-Quan
The maternal genetic effects on estimating genetic parameters for growth traits and wool traits of Qinghai fine-wool sheep were investigated.The genetic parameters for production traits of Qinghai fine-wool sheep were estimated by average information restricted maximum likelihood (AIREML) with different animal models, and the differences between different animal models were tested by likelihood ratio test. Fixed effects, direct genetic effects, and residual effects were included all models; and random effects were individual permanence environmental effects, maternal genetic effects, and maternal permanence environmental effects. The six models differ in the way of considering random effects: in model 1 individual permanence environmental effects, maternal genetic effects, and maternal permanence environmental effects were not contained; in model 2 maternal permanence environmental effects were included; in model 3 maternal genetic effects were included; in model 4 both maternal genetic effects and maternal permanence environmental effects were include; in model 5 both individual permanence environmental effects and maternal genetic effects were contained;in model 6 all random effects were contained. The direct heritabilities were 0.1896~0.3781, 0.2537~0.2890, 0.2244~0.3225, 0.2205~0.3983, 0.1218~0.1490, 0.0983~0.4802, and 0.1170~0.1311 for birth weight, weaning weight, yearling weight, hogget weight,greasy fleece weight, fiber diameter, and staple length,respectively. Compared with model 1, model 3 was-significant(P<0.01) for birth weight and weaning weight, other models were not significant (P>0.05)for Yearling weight, Hogget weight; and paralleled with model 6, both model 4 and model 5 were significant(P<0.01) for fiber diameter,model 4 was significant(P<0.05) for staple length, and other models were not significant(P>0.05) for greasy fleece weight by likelihood ratio test.The maternal effects were important determinants of estimated the genetic parameters for
Safari, E; Fogarty, N M; Gilmour, A R; Atkins, K D; Mortimer, S I; Swan, A A; Brien, F D; Greeff, J C; van der Werf, J H J
Data from seven research resource flocks across Australia were combined to provide accurate estimates of genetic correlations among production traits in Merino sheep. The flocks represented contemporary Australian Merino fine, medium and broad wool strains over the past 30 years. Over 110,000 records were available for analysis for each of the major wool traits, and 50,000 records for reproduction and growth traits with over 2700 sires and 25,000 dams. Individual models developed from the single trait analyses were extended to the various combinations of two-trait models to obtain genetic correlations among six wool traits [clean fleece weight (CFW), greasy fleece weight, fibre diameter (FD), yield, coefficient of variation of fibre diameter and standard deviation of fibre diameter], four growth traits [birth weight, weaning weight, yearling weight (YWT), and hogget weight] and four reproduction traits [fertility, litter size, lambs born per ewe joined, lambs weaned per ewe joined (LW/EJ)]. This study has provided for the first time a comprehensive matrix of genetic correlations among these 14 wool, growth and reproduction traits. The large size of the data set has also provided estimates with very low standard errors. A moderate positive genetic correlation was observed between CFW and FD (0.29 +/- 0.02). YWT was positively correlated with CFW (0.23 +/- 0.04), FD (0.17 +/- 0.04) and LWEJ (0.58 +/- 0.06), while LW/EJ was negatively correlated with CFW (-0.26 +/- 0.05) and positively correlated with FD (0.06 +/- 0.04) and LS (0.68 +/- 0.04). These genetic correlations, together with the estimates of heritability and other parameters provide the basis for more accurate prediction of outcomes in complex sheep-breeding programmes designed to improve several traits.
Reinecke, R K
The acquisition and intensity of infection with gastrointestinal nematodes and with Oestrus ovis are compared over 2 years in sheep grazed intensively (26-36 sheep ha-1) or non-intensively (12 sheep ha-1) in the winter rainfall Overberg region of South Africa. Sheep grazing intensively on grass/legume pastures, spray irrigated in summer, acquired massive mixed infections of Trichostrongylus, Haemonchus and Teladorsagia. Infections were fatal for sucking lambs. Lambs from ewes grazed non-intensively on dry land lucerne in winter became infected with Nematodirus and then with Teladorsagia and Trichostrongylus spp.; resistance to Nematodirus was apparent after 12 weeks; spontaneous cure of Teladorsagia began in hoggets grazing on safe wheat stubble pasture; but Trichostrongylus survived in the sheep. Helminth-induced host mortality was not observed on the non-intensive farm. The efficacy of various methods of control was examined in the intensively managed sheep. Removal from pasture, mixed grazing (cattle before sheep) and an albendazole slow release bolus all significantly (P < 0.05) reduced levels of infection in animals so treated, compared with control sheep which were treated periodically with anthelmintics as standard farm management practice. Removal of sheep from the pasture for 30 days in the summer seemed to have beneficial effects. Treatment of sheep weekly with albendazole increased levels of infection in the sheep over controls. The status of vaccination is described and the potential of intergenic competition in grazing management and perhaps vaccination is discussed. Resistance of nematodes to anthelmintics was relatively wide-spread. In both intensive and non-intensive systems. Oestrus ovis larvae were present in flock sheep for 10-12 months per year. Imagines failed to develop from 27 April-9 August and it was concluded that larvae had to overwinter in sheep to survive. Recommendations for integrated control are made for both intensive and non
Smith, K C; Long, S E; Parkinson, T J
A survey of abnormalities of the reproductive tract of female sheep was undertaken at two abattoirs in the south west of England over a period of 12 months. During the survey, 9970 reproductive tracts from cull ewes and 23,536 tracts from nulliparous sheep (prime lambs and hoggets) were examined. A total of 655 (6.57 per cent) ewes and 459 (1.95 per cent) nulliparous sheep had abnormalities of the reproductive tract. Of these, congenital abnormalities of the paramesonephric ducts accounted for 2.4 per cent of the ewes and 7.4 per cent of the nulliparous sheep, congenital abnormalities of the ovaries accounted for 2.6 per cent of the ewes and 7.4 per cent of the nulliparous sheep and cystic structures that were considered to have been of congenital origin accounted for 27.2 per cent of the ewes and 52.7 per cent of the nulliparous sheep. The most common lesion was paraovarian cysts (26.6 per cent of ewes and 39.0 per cent of nulliparous sheep), but few of these appeared to have affected the sheep's reproductive function. Several specific conditions were recorded, including some described for the first time in sheep. Uterus unicornis occurred in 20 sheep and other forms of segmental aplasia of parts of the paramesonephric ducts occurred in a further 13 animals. Uterus didelphys occurred in six sheep, and 11 animals were intersex. Intersex sheep had vestigial structures that were derived from the paramesonephric ducts, hypoplastic or masculinised gonads and some had masculinised external genitalia. Ovarian hypoplasia occurred in 34 sheep, and in a further 12 mainly nulliparous animals, the ovaries were fused. Sixty nulliparous animals and two ewes had hydatids of Morgagni.
di Virgilio, Agustina; Morales, Juan Manuel
Background. A large proportion of natural grasslands around the world is exposed to overgrazing resulting in land degradation and biodiversity loss. Although there is an increasing effort in the promotion of sustainable livestock management, rangeland degradation still occurs because animals' foraging behaviour is highly selective at different spatial scales. The assessment of the ecological mechanisms modulating the spatial distribution of grazing and how to control it has critical implications for long term conservation of resources and the sustainability of livestock production. Considering the relevance of social interactions on animals' space use patterns, our aim was to explore the potential effects of including animals' social context into management strategies using domestic sheep grazing in rangelands as case study. Methods. We used GPS data from 19 Merino sheep (approximately 10% of the flock) grazing on three different paddocks (with sizes from 80 to 1000 Ha) during a year, to estimate resource selection functions of sheep grazing in flocks of different levels of heterogeneity. We assessed the effects of sheep class (i.e., ewes, wethers, and hoggets), age, body condition and time since release on habitat selection patterns. Results. We found that social rank was reflected on sheep habitat use, where dominant individuals (i.e., reproductive females) used more intensively the most preferred areas and low-ranked (i.e., yearlings) used less preferred areas. Our results showed that when sheep grazed on more heterogeneous flocks, grazing patterns were more evenly distributed at all the paddocks considered in this study. On the other hand, when high-ranked individuals were removed from the flock, low-ranked sheep shifted their selection patterns by increasing the use of the most preferred areas and strongly avoided to use less preferred sites (i.e., a highly selective grazing behaviour). Discussion. Although homogenization and segregation of flocks by classes
Colvin, A F; Walkden-Brown, S W; Knox, M R; Scott, J M
While rotational grazing methods have an accepted role in the management of gastrointestinal nematodosis (GIN) of small ruminants in humid tropical regions, their efficacy and application in cool temperate regions is more controversial. This study evaluated GIN over 2 years in three classes of fine wool Merino sheep (lambs, hoggets and ewes) under three different sheep management systems in a cool tableland environment near Armidale NSW Australia (950m altitude, 30 degrees 31'S, 151 degrees 39'E). The management systems were High input (HI) with high fertiliser inputs, a target of 100% sown pasture, high stocking rate (13.4 dry sheep equivalents/ha) and relatively long grazing periods; Typical (TYP) New England management system with moderate fertiliser inputs and stocking rate (9.3DSE/ha) and relatively long grazing periods; and Intensive rotational grazing (IRG) with moderate fertiliser inputs and stocking rate (8.8DSE/ha) but very short (mean 5 days) grazing periods and long (mean 103 days) rest periods. Twenty sheep of each class in each management treatment were sampled monthly for faecal worm egg counts (WEC, followed by larval differentiation), and body weights with a blood sample taken for haematology every second month. The proportion of sheep with WEC above zero did not differ between management systems but the magnitude of WEC did, with sheep under IRG displaying lower mean WEC than those on the other treatments (IRG: 326, HI: 594, TYP: 536, eggs/g P<0.0001). This was despite a significantly longer mean interval between anthelmintic treatments (IRG: 144 days, HI: 77 days, TYP: 78 days, P<0.0001). The IRG management system also influenced the composition of the infections with sheep on this treatment having a significantly lower proportion of Haemonchus contortus in their faecal cultures (IRG: 59.7%, HI: 79.4%, TYP: 80.9%, P<0.05) and a significantly higher proportion of Trichostrongylus spp. Sheep on the IRG treatment also had a significantly higher
Morales, Juan Manuel
Background. A large proportion of natural grasslands around the world is exposed to overgrazing resulting in land degradation and biodiversity loss. Although there is an increasing effort in the promotion of sustainable livestock management, rangeland degradation still occurs because animals’ foraging behaviour is highly selective at different spatial scales. The assessment of the ecological mechanisms modulating the spatial distribution of grazing and how to control it has critical implications for long term conservation of resources and the sustainability of livestock production. Considering the relevance of social interactions on animals’ space use patterns, our aim was to explore the potential effects of including animals’ social context into management strategies using domestic sheep grazing in rangelands as case study. Methods. We used GPS data from 19 Merino sheep (approximately 10% of the flock) grazing on three different paddocks (with sizes from 80 to 1000 Ha) during a year, to estimate resource selection functions of sheep grazing in flocks of different levels of heterogeneity. We assessed the effects of sheep class (i.e., ewes, wethers, and hoggets), age, body condition and time since release on habitat selection patterns. Results. We found that social rank was reflected on sheep habitat use, where dominant individuals (i.e., reproductive females) used more intensively the most preferred areas and low-ranked (i.e., yearlings) used less preferred areas. Our results showed that when sheep grazed on more heterogeneous flocks, grazing patterns were more evenly distributed at all the paddocks considered in this study. On the other hand, when high-ranked individuals were removed from the flock, low-ranked sheep shifted their selection patterns by increasing the use of the most preferred areas and strongly avoided to use less preferred sites (i.e., a highly selective grazing behaviour). Discussion. Although homogenization and segregation of flocks by
Methane emissions changed nonlinearly with graded substitution of alfalfa silage with corn silage and corn grain in the diet of sheep and relation with rumen fermentation characteristics in vivo and in vitro.
Jonker, A; Lowe, K; Kittelmann, S; Janssen, P H; Ledgard, S; Pacheco, D
Feeding grain and corn silage have been proposed as practices to reduce enteric methane (CH) emissions per unit of intake from ruminants, but the inclusion level required in the diet is normally not specified. The objectives of the current study were to determine the CH emission factor (g/kg DMI) of sheep fed alfalfa silage substituted with increasing levels of corn silage or corn grain at a fixed DMI level (2% of BW) and determine its relationship with rumen fermentation characteristics and microbial community composition and with in vitro fermentation characteristics of the same diets incubated using a standard laboratory method. Romney ewe hoggets (approximately 14 mo old; = 64) were randomly allocated to 8 dietary treatments, which included chaffed alfalfa silage alone or substituted with either 25, 50, 75 or 100% corn silage or 25, 50 or 65% rolled corn grain on a DM basis. After acclimatization to the diet, DMI and CH emissions were measured from individual sheep for 2 consecutive days in open-circuit respiration chambers and a rumen sample was collected at 3 h after feeding. The same diets were also incubated in an automated in vitro gas production system for 48 h using rumen liquid of fistulated nonlactating dairy cows grazing pasture. Increasing the substitution of alfalfa silage with corn silage or corn grain in the diet of sheep resulted in a quadratic response ( < 0.01) in CH emissions per unit of DMI (CH/DMI) with either supplement. For both supplements, CH/DMI increased in mixtures of up to 50% supplement inclusion and then decreased with greater supplement inclusion, especially with corn grain inclusion, but the level did not fall below that for 100% alfalfa silage. The ratio of acetate + butyrate to propionate + valerate and the propionate proportion alone in rumen liquid were the strongest single predictors for CH/DMI in the overall data set and explained 37.1 and 32.5%, respectively, of the variation in CH/DMI. Methanogens of (21.1% of total