Variation between Merino ewes in pasture intake 1. Between flock differences and some environmental sources of variation

Lee, G.J.; Atkins, KD; Mortimer, SI

doi:10.1016/0301-6226(94)00057-e

Cited by 12 publications

(7 citation statements)

References 29 publications

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“…However, wool production from dams with male or female lambs did not differ, so we rejected our second hypothesis. A substantial increase in feed intake, and subsequent live weight, after mid-pregnancy, has been interpreted as reflecting the positive relationship between feed intake and the increase in accumulated mass of the feto-placental unit(s) [27,28,29], with the effect being most evident in ewes bearing multiple fetuses ([30], present study). However, it is important to remember that the accelerated accumulation of resources, and the redistribution towards feto-placental unit(s) is not a passive process (the “sink” concept), but a controlled process that has evolved to ensure metabolic support for fetal growth and development [31,32].…”

Section: Discussionmentioning

confidence: 82%

Pregnancy and Litter Size, But Not Lamb Sex, Affect Feed Intake and Wool Production by Merino-Type Ewes

Cordero

Meza-Herrera

García

et al. 2019

Animals

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Two experiments (Australia and Mexico) tested whether feed intake (FI) and wool production (WP) are affected by pregnancy (PRG), litter size (LZ), or lamb sex (LS) in Merino-type ewes. In Experiment-1, ewes were either not pregnant (NPR; n = 6), or carrying 1 (PR1; n = 7) or 3 (PR3; n = 11) fetuses, were studied in individual pens. NPR ewes had lower (p < 0.02) FI throughout PRG and lactation (LAC), except around lambing (p < 0.001). Following lambing, FI increased in PRG ewes (p < 0.001) to double the values in NPR ewes. PRG reduced WP (p < 0.001); in PR3, WP was lower than for both PR1 and NPR (p < 0.001). WP decreased during LAC and was lower in ewes rearing lambs than in NPR ewes (p < 0.001). Experiment-2 used 48 pregnant ewes (28 bearing singles and 20 bearing twins). Dam and lamb live weights (LW) and body condition (BC) were recorded from birth to weaning at 60 d, and dam fleece weight (DFW) was measured at weaning (12 months growth). WP was higher in ewes bearing and rearing single lambs than in ewes bearing twins (p < 0.001). DFW was positively (p < 0.01) related to LZ, dam LW, and BC, but not to changes in dam LW during LAC, or to lamb weight at birth or weaning, or LW gain, or LS. In conclusion, FI was affected during PRG and by LZ during LAC, whereas WP was influenced by LZ, but not LS, only during pregnancy.

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Section: Discussionmentioning

confidence: 82%

Pregnancy and Litter Size, But Not Lamb Sex, Affect Feed Intake and Wool Production by Merino-Type Ewes

Cordero

Meza-Herrera

García

et al. 2019

Animals

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“…Most of the differences were associated with trial liveweight, which was a highly significant covariate within and between lines. Lee et al (1995a) also reported a positive relationship in ewes between DOMI and liveweight. Their within-flock estimates ranged from 0.0100 to 0.0144 kg DOMI per kg liveweight.…”

Section: Food Intakementioning

confidence: 89%

“…Food intake has been recorded in one small trial with New Zealand Romney lines (McClelland et al 1986) and in Australian Merino selection lines (Lee et al 1995a). The present experiment provided the opportunity to study correlated FEC responses in five selection lines and their controls, from three selection experiments which were all managed at the same site.…”

Section: Introductionmentioning

confidence: 99%

Faecal egg count and food intake comparisons of Romney single‐trait selection and control lines

Morris

Clarke

Watson

et al. 1996

New Zealand Journal of Agricultural Research

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Two sets of correlated responses were studied in five Romney selection lines and their controls. The lines were from one experiment selecting for yearling body weight or yearling fleece weight since 1967, from a second experiment selecting for weaning weight or yearling fleece weight since 1973, and from a third experiment selecting for yearling body weight since 1973. Overall, the five selection lines were evaluated whilst being run together with controls at a single site. The responses were faecal egg count (FEC) after weaning, using lamb crops born in 1990-93, and food intake using 1993-born 7-month-old ram lambs. Four or five new sires were used per line per year, with 1471 and 232 animals being recorded for FEC and food intake respectively. The three body weight lines were each 20-22% heavier than their respective controls in March (6 months of age) and May. Average FEC over this time period was significantly greater by 63% in one of these three lines whereas there was no difference from the control in the other two body weight lines. The two fleece weight lines were 10-11% heavier in March-May, with 34-35% heavier yearling fleece weights, than their respective controls, whereas average FEC was significantly greater (by 35 and 46%) in both selection lines. Significant correlated increases in estimated food intake were recorded in all three body weight lines and in one of the two fleece weight lines, and these increases were proportional to the liveweight response. The implications of the correlated responses and their variability are discussed.

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“…Bailey et al (1996) investigated grazing behavior as a way of understanding grazing patterns of large herbivores. Lee et al (1995) and Fogarty et al (2006) investigated pasture intake of grazing Merino ewes by means of fecal markers. However, these methods are unlikely to be used as a selection criterion in practical breeding.…”

Section: Introductionmentioning

confidence: 99%

Adaptability of pregnant Merino ewes to the cold desert climate in Nevada1

Rauw

Thain

Teglas

et al. 2010

Journal of Animal Science

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Grazing ability is difficult to record in animals under free-ranging conditions without sophisticated methods. Alternatively, grazing ability may be indirectly inferred from changes in BW and production characteristics during the grazing period. The present study investigated the effect of grazing on resource-limited rangelands on BW, wool characteristics, and offspring weaning weights in nine hundred five 5/8, 7/8, and fullblood Merino ewes of 2 to 7 yr of age during a grazing period of approximately 2.5 mo (between January and March). A total of 469 ewes gave birth to a single lamb, 248 to twin lambs, and 188 did not give birth. Body weights were measured and wool samples taken before and after the ewes were allowed to graze freely on the rangelands; absolute change in BW and change in BW as a percentage of initial BW were estimated. On average, grazing on resource-poor rangelands resulted in BW loss, a reduction in fiber diameter and its CV, and increased staple length. Animals with finer wool at the start of the grazing period lost phenotypically (r = -0.07, P < 0.05) and genetically (r = -0.23, P < 0.05) less BW during the grazing period and had a greater probability to carry 1 lamb (or 2) to term (P < 0.05). Animals that lost less BW produced more greasy fleece (r = 0.09, P < 0.01). Body weight change did not significantly influence offspring weaning weights. Change in BW was moderately heritable at h(2) = 0.29; fiber diameter was strongly heritable at h(2) = 0.51. Animals with the least inclusion of Merino genetics lost more BW (P < 0.01) during the grazing period and had a more uniform fiber diameter (P < 0.05) but shorter staples (P < 0.05) and less fleece (P < 0.0001) than animals with a greater level of Merino genetics. Our results indicate that animals with finer wool appeared to be better adapted to the cold Nevada desert. Thus, selection for finer wool may positively influence adaptability to resource-limited cold climate conditions; alternatively, BW change may be selected for directly. Because nutritional deficiencies during pregnancy can have adverse consequences for the offspring, indirect selection for grazing ability would foremost result in healthier ewes that can produce lambs and wool without compromising their welfare.

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Variation between Merino ewes in pasture intake 1. Between flock differences and some environmental sources of variation

Cited by 12 publications

References 29 publications

Pregnancy and Litter Size, But Not Lamb Sex, Affect Feed Intake and Wool Production by Merino-Type Ewes

Pregnancy and Litter Size, But Not Lamb Sex, Affect Feed Intake and Wool Production by Merino-Type Ewes

Faecal egg count and food intake comparisons of Romney single‐trait selection and control lines

Adaptability of pregnant Merino ewes to the cold desert climate in Nevada1

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