Evaluation of sheep genetic resources in North America: Lamb productivity of purebred, crossbred and synthetic populations

Shrestha, J. N. B.; Boylan, W. J.; Rempel, W. E.

doi:10.4141/cjas07049

Cited by 6 publications

(4 citation statements)

References 14 publications

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“…Furthermore, there is a theoretical decrease in the genetic potential for commercial performance due to the lower level of heterozygosity maintained in the composite population than that of a specific breed cross or rotational crossbreeding involving the same number of breeds. Some of the composite populations based on F or Ro inheritance that have demonstrated considerable potential for commercial sheep production are the Finngalway and Finn-Dorset in Ireland (Hanrahan 1977), the ABRO damline in the United Kingdom (Smith et al 1979), Polypay in the United States (Hulet et al, 1984), and the INRA 401 in France (Tchamitchian et al 1986). The present study confirms that the Arcott breeds and synthetic populations derived from complementary combinations of fecund-type and established breeds have productivity comparable to or exceeding their parental breeds as well as the Su and F breeds demonstrating considerable potential for commercial lamb production.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of sheep genetic resources in North America: Ewe productivity of purebred, crossbred and synthetic populations

Shrestha¹,

Boylan²,

Rempel³

2008

Can. J. Anim. Sci.

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Evaluation of sheep genetic resources in North America: Ewe productivity of purebred, crossbred and synthetic populations. Can. J. Anim. Sci. 88: 399Á408. Ewe productivity from divergent genetic types of established purebreds e.g., Dorset (D), Lincoln (L), Rambouillet (Ra), Suffolk (Su) and Targhee (T); fecund-type breeds e.g., Finnsheep (F) and Romanov (Ro) breeds, and their reciprocal crosses; the Outaouais (O) and Rideau (R) Arcott breeds and their reciprocal crosses; and Synthetic I (½ F, ½ L), Synthetic II (½ D, ½ Ra) and Synthetic III (¼ F, ¼ L, ¼ D, ¼ Ra) populations were evaluated. Prolificacy, fecundity, ewe weight, grease fleece weight, wool grade, lamb survival and total lamb weights at birth, 30 d and 140 d per ewe lambing were considered jointly as a measure of ewe productivity. In general, fecund-type breed cross and Arcott breed cross were highest in productivity, the fecund-type breed, Arcott breed and synthetic populations were intermediate, in contrast the established breeds was lowest. Regardless of significantly heavier ewe and grease fleece weights, and superior wool grade of the established breeds, their poor performance can be attributed to lower prolificacy, fecundity and total lamb weights (P B0.05). Within established breeds, the D, L, Ra and T breeds were comparable in productivity to the Su breed, but lower than the F breed (PB0.05). The Ro breed surpassed the F breed because of significantly higher prolificacy and fecundity, and heavier ewe weight and total lamb weights, while grease fleece weight and wool grade were inconsistent. The F and Ro breeds were comparable to the Su breed despite significantly higher prolificacy and fecundity, in contrast to lighter ewe and grease fleece weights, lower wool grade, lamb survival, similar total lamb weights. Although the R breed produced significantly heavier grease fleece weight and total lamb weights than the O breed, both breeds were similar to the Su breed despite their significantly higher prolificacy and fecundity, in contrast to similar ewe weight, wool grade, lamb survival and total lamb weights, and lighter grease fleece weight. The O and R breeds were more productive than the F breed as a result of significantly heavier ewe weight, superior wool grade, higher lamb survival and heavier total lamb weights, despite their similar prolificacy, fecundity and grease fleece weight. Synthetic I and Synthetic III with Finnsheep lineage surpassed Synthetic II in productivity as a result of significantly higher prolificacy and fecundity, and heavier total lamb weights, despite similar ewe and grease fleece weights and inconsistent wool grade and lamb survival. At the same time, Synthetic I and Synthetic III were not only similar to the Su breed, but surpassed the F breed, whereas Synthetic II was similar to the Su breed and lower than the F breed. Finally, systematic crossbreeding and composite population of complementary fecund-type and established breeds achieved increased productivity from additive genetic variation and heterosis. . Pour mes...

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Section: Discussionmentioning

confidence: 99%

Evaluation of sheep genetic resources in North America: Ewe productivity of purebred, crossbred and synthetic populations

Shrestha¹,

Boylan²,

Rempel³

2008

Can. J. Anim. Sci.

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“…The fecund-type breeds, F and Ro, introduced into North America in the latter part of the 20th century, are grouped separately. Details and description of the feeding, management and breeding protocol of sheep has been published (Shrestha et al 2008a, b). Care and handling of the sheep conform to the guidelines established by the American Association for Accreditation of Laboratory Animal Care (National Research Council, Institute for Laboratory Animal Resources 1996), which are similar to those of the Canadian Council on Animal Care (1993).…”

Section: Methodsmentioning

confidence: 99%

Evaluation of sheep genetic resources in North America: Milk production and composition of purebred, crossbred and synthetic populations

Shrestha¹,

Boylan²,

Rempel³

2008

Can. J. Anim. Sci.

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Evaluation of sheep genetic resources in North America: Milk production and composition of purebred, crossbred and synthetic populations. Can. J. Anim. Sci. 88: 569Á576. Purebreds, crossbreds and synthetic populations of sheep in North America of divergent genetic types produced 47Á103 litres of milk for 121Á144 d, consistent with ''non dairy-type'' breeds; however, this was substantially less than the 200Á330 kg of milk per lactation characteristic of ''dairy'' type breeds in Europe and the Middle East countries. Among established breeds, the Suffolk (Su) breed produced significantly more total and daily milk yield, respectively, for a longer lactation (79 litres and 589 mL for 139 d), followed by the Rambouillet (Ra), Targhee (T) and Dorset (D) breeds (60Á62 litres and 422Á542 mL for 120Á132 d), while the Lincoln (L) breed produced significantly less (48 litres and 285 mL for 128 d). Among fecund-type breeds and their crosses, Finnsheep (F) and Romanov (Ro) breeds produced significantly less (50Á55 litres and 425Á463 mL, for 122Á129 d), while Ro )F produced significantly more milk (91 litres and 744 mL for 126 d), followed by F )Ro (60 litres and 505 mL for 128 d). Among other crossbreds, F)Ra produced significantly more milk (66 litres and 434 mL for America exhibited diversity that was substantial for milk yield, but negligible for lactation length, as well as fat, protein, lactose and solid-not-fat content. Lack of inherent potential for milk production continues to be a serious constraint towards development of commercial dairy sheep industry. In the absence of ''dairy-type'' breeds, superior milk production in the Rideau Arcott breed (with East Friesian lineage) and their crosses demonstrates considerable promise for further improvement, thus increasing the efficiency of sheep production.

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“…Chilota lambs are normally slaughtered at 150-180 days old, as occurs with other introduced breeds, because they reach their maximum weight at this age (Shrestha et al, 1982(Shrestha et al, , 2007Stanford et al, 1996;Hammel & Laforest, 1999;Teixeira et al, 2004).…”

Section: Resultsmentioning

confidence: 99%

Development of the Morphostructure and Meat Value in Chilota Lambs

et al. 2012

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SUMMARY:Chilota sheep are typical of the Chiloé archipelago in southern Chile. The objectives of this study were: 1) To describe the development of the morphostructure of Chilota lambs in their first months of life using some variables that determine lamb meat value (zoometric traits and body weight) and 2) To determine the optimum slaughter age. Measurements were taken from 12 male single-born lambs. Body weight, Withers height; Perimeter of thorax, Chest depth, Shoulder point width and Body length were measured in each animal. The first measurements were taken at 7 days old, and the rest at 37, 67, 97, 127, 157 and 187 days old. The body weight variables and zoometric traits developed allometrically throughout the growth phase. The correlation coefficient between all the traits was very high, varying between 0.91 and 0.98. The zoometric variable that best predicted body weight was Perimeter of thorax (r2=0.93), which was fully developed in 90% of the animals at 97 days old. Maximum growth was recorded in all the studied variables during the first control month, days 7-37, but then it decreased gradually. This decrease was moderate until day 127, becoming very low from then on until end of the study. The optimum age for slaughtering fattened lambs is approximately four months, as from day 127 the daily growth rate slows down considerably, to 61.81 g/day, in comparison with the previous stage, which is 220.00 g/day. Therefore, the maintenance of lambs after four months is not productively efficient.

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Evaluation of sheep genetic resources in North America: Lamb productivity of purebred, crossbred and synthetic populations

Cited by 6 publications

References 14 publications

Evaluation of sheep genetic resources in North America: Ewe productivity of purebred, crossbred and synthetic populations

Evaluation of sheep genetic resources in North America: Ewe productivity of purebred, crossbred and synthetic populations

Evaluation of sheep genetic resources in North America: Milk production and composition of purebred, crossbred and synthetic populations

Development of the Morphostructure and Meat Value in Chilota Lambs

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