F1 Lambs Research Articles

Examination of Fattening and Slaughtering Performance of Hungarian Merino, Ile de France F1 and Suffolk F1 Lambs

In our examination, we evaluated Hungarian Merino (ram n=30, ewe n=30), Ile de France F1 (ram n=10, ewe n=10) and Suffolk F1 (ram n=10, ewe n=10) lambs. The best fattening performance was shown by the Ile de France F1 lambs (361 g/day). After the fattening period, Hungarian Merino, Ile de France F1 and Suffolk F1 genotypes lambs were slaughtered with a live weight of 30-34 kg. Carcasses were evaluated for dressing percentage, weight of valuable carcass cuts, percentage of valuable meat, bone to meat ratio, as well as meat conformation and fat cover (S/EUROP grading).The slaughter performance proved to be the best for the Suffolk F1 concerned dressing percentage (51,7%), percentage valuable carcass cuts (81,9%). The best percentage valuable meat presented (79,4%) the Ile de France F1 lambs. The best meat conformation and fat covered were in the Suffolk F1 lambs; Hungarian Merinos showed less favourable results.Presently, the results derived from Hungarian practice that Hungarian Merino lambs are not eligible for fattening to great live body weight (30 kg). Therefore, it is necessary to revise the Hungarian Merino lambs with meat sheep breeds.

Evaluation of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds of sheep: IV. Survival, growth, and carcass traits of F1 lambs1,2

The objectives of this study were to estimate effects of sire breed (Dorset, Finnsheep, Romanov, Texel, and Montadale), and dam breed (Composite III and Northwestern whiteface) on survival, growth, carcass, and composition traits of F1 lambs. Effects of mating season (August, October, and December) were estimated for survival and growth traits. Data were collected on 4,320 F1 lambs sired by 102 purebred rams over 3 yr. Birth weight was recorded on all lambs, and subsequent BW were adjusted to 56 (weaning), 70, and 140 d of age (n = 3,713, 3,654, and 3,579 observations, respectively). Survival of dam-reared progeny (n = 4,065) to weaning was recorded. Each year, wethers from October matings were slaughtered in three groups at 25, 29, and 33 wk of age to obtain carcass data (n = 546). In addition to standard carcass traits, resistive impedance measurements were recorded on the warm carcass to predict lean mass. Dam breed (P = 0.37) did not influence lamb survival to weaning, but sire breed (P < 0.05) was important. Romanov-sired lambs excelled in survival rate to weaning (94.1%), followed by Finn-sheep (93.0%), Texel (90.7%), Dorset (90.0%), and Montadale (89.1%) sired progeny. Lower (P < 0.01) postweaning growth rate was observed for Texel (267 g/d) and Finnsheep (272 g/d) sired progeny than for Dorset (285 g/d), Montadale (282 g/d), and Romanov (278 g/d) sired progeny. Sire breed and dam breed were generally significant for most carcass traits. Breed differences in distribution of carcass fat and carcass shape were detected; however, carcass composition was similar for all sire breeds when compared at a constant carcass weight. When evaluated at a constant 12th-rib fat depth, carcasses of lambs from Finnsheep, Romanov, and Texel sires produced 1 to 1.5 kg less (P < 0.001) predicted lean mass per lamb than carcasses of lambs from Dorset and Montadale sires. These experimental results provide information about the direct breed effects for survival, growth, and carcass traits of these breeds and their potential use in crossbreeding systems.

Experimental infection of Black Belly and INRA 401 straight and crossbred sheep with trichostrongyle nematode parasites

Compared to INRA 401 lambs reared in France, Black Belly (BB) lambs reared in Guadeloupe (F.W.I.) were highly resistant to both primary and secondary experimental infection with Haemonchus contortus. To investigate this huge inter-breed difference, a nucleus flock of BB was constituted, and experiments were conducted to: (i) confirm this difference in lambs born in France, (ii) check whether it was similar for Trichostrongylus colubriformis and Teladorsagia circumcincta, and (iii) find out whether this difference was age-related. Forty BB lambs, 84 F1 lambs (BB sires×INRA 401 ewes) and 88 INRA 401 lambs born in two cohorts were used in an experimental design involving three host breeds, both genders and two age-groups (3.5- and 7-month-old when first infected). The limited availability of BB lambs made the study incomplete. Infection consisted of the administration of two doses of 10 000 infective larvae of one of the nematode species, separated by an anthelmintic treatment and an interval of 1 week before the second dose was administered. Fecal egg counts (FECs) were done on Days 28 and 35 after each infection; ewe lambs of the INRA 401 and F1 breeds were necropsied, the worm burden was established, the length of the female worms measured and the eggs in utero counted. For H. contortus and T. colubriformis, the FEC was lower in the BB than in the INRA 401 lambs, and the FEC found for the F1 lambs was intermediate. For T. circumcincta, only data for the F1 and INRA 401 lambs were available, and the FECs for these breeds were the same. In all three breeds, the FEC determined after the second dose was significantly lower than that found after the first dose in the ewe lambs, but not in the ram lambs. Infecting the lambs when they were 7- instead of 3.5-month-old significantly lowered egg excretion of both parasites in the F1 ( P<0.0001), but not the INRA 401 lambs. Worm numbers in the F1 and in the INRA 401 ewe lambs confirmed the FEC data, many F1 lambs being free of T. colubriformis. The H. contortus female worms were shorter and had fewer eggs in utero in the F1 than in the INRA 401 lambs. A higher proportion of T. circumcincta was at the fourth larval stage in the F1 lambs. In conclusion, the BB breed is much more resistant than INRA 401 to H. contortus, with the F1 lambs being more like the BBs after the second dose. This difference was also found for T. colubriformis and, to a lesser extent, for T. circumcincta.

Características de reprodução e de crescimento de ovinos mestiços Santa Inês, no Ceará

O efeito do ambiente e do genótipo foi estudado em dez fazendas particulares no Estado do Ceará, em 480 ovelhas Crioulas, 48 carneiros Santa Inês e 1474 cordeiros F1. As características estudadas foram taxas de acasalamento, fertilidade ao parto, prolificidade e desmame, bem como os pesos ao nascer, 56, 84 e 112 dias de idade e os ganhos diários de peso do nascimento aos 56, dos 56 aos 84 e do nascimento aos 112 dias de idade. Houve efeito significativo da raça sobre as taxas de acasalamento, fertilidade e desmame, sendo que as ovelhas F1 produziram menos cordeiros que as Crioulas. Houve efeito significativo da idade das ovelhas e da fazenda sobre todas as características estudadas, exceto o efeito da idade da ovelha sobre a taxa de desmame. Os pesos e os ganhos de peso na fase de crescimento, de modo geral, foram influenciados pelo ano de nascimento, tipo de nascimento, fazenda e reprodutor dentro de fazenda. As estimativas de herdabilidades para os pesos variam de 0,36 a 0,53, mostrando que existe grande possibilidade para se melhorar a taxa de ganho de peso dos cordeiros cruzados por meio de seleção.

Heterosis retained in different generations of inter se mating between D’man and Sardi sheep

Heterosis retained in different generations of <i>inter se</i> mating between D’man and Sardi sheep

Desempenho e características da carcaça de cordeiros de três grupos genéticos abatidos ao mesmo estágio de maturidade

O presente estudo teve como objetivo comparar o desempenho e características de carcaça de cordeiros de três grupos genéticos abatidos ao mesmo estágio de maturidade, em condições de confinamento. Foram utilizados 23 cordeiros, sendo sete da raça Ideal (I), oito ½ Texel + ½ Ideal (F1) e oito ¾ Texel + ¼ Ideal (F2), machos com idade entre três a quatro meses. O abate foi realizado assim que cada cordeiro atingiu 65% do peso à maturidade das ovelhas do seu grupo genético, que correspondeu a 27,5kg para o Ideal, 30,9kg para os cruzas F1 e 31,7kg para os cruzas F2. Não foi observada diferença significativa (P&gt;0,05) entre os três grupos genéticos para os seguintes parâmetros: consumo de matéria seca (gramas/unidade de tamanho metabólico ekg/100kg PV), conversão alimentar, número de dias em confinamento, índice de quebra ao resfriamento e rendimento de carcaça. Os cordeiros Ideal apresentaram menor ganho médio diário e peso vivo ao abate (P&lt;0,05) do que os cordeiros cruzas (F1 e F2), no entanto, estes não diferiram entre si (P&gt;0,05). Os cordeiros cruzas F2 apresentaram maiores pesos de carcaça quente e fria (P&lt;0,05) do que os cordeiros Ideal e cruzas F1, no entanto, estes não diferiram entre si (P&gt;0,05). Quanto ao consumo de matéria seca (gramas/animal/dia), os cordeiros cruzas F2 apresentaram maior consumo (P&lt;0,05) do que os cordeiros Ideal; no entanto, os cordeiros cruzas (F1 e F2) e Ideal e cruzas F1 não diferiram entre si (P&gt;0,05).

Evaluation of the ovine callipyge locus: III. genotypic effects on meat quality traits.

A resource flock of 362 F2 lambs provided phenotypic and genotypic data to estimate effects of callipyge (CLPG) genotypes (NN, NC, CN, and CC) on meat quality traits. The mutant allele is represented as C, the normal allele(s) as N, and the paternal allele of a genotype is given first. Lambs of each genotype born in 1994 and 1995 were serially slaughtered in six groups at 3-wk intervals starting at 23 wk of age. Warner-Bratzler shear force and subjective evaluation of marbling were collected during both years from longissimus. Calpastatin activity was measured on longissimus from the 1994 group, and ELISA quantification of calpastatin protein was obtained from the 1995 group. Significant additive and paternal polar overdominance effects on meat quality traits were detected. This is in contrast to previous research that detected only polar overdominance effects on slaughter and carcass traits in this population. The magnitude of genotypic effects on shear force differed significantly between years; however, additive (P < .01), paternal polar overdominance (P < .001), and maternal dominance (P < .01) effects adjusted for variation in carcass weight were detected within each year. Shear force data adjusted to the mean slaughter age or carcass weight indicated that the means and variances of CN and CC genotypes were greater than values of NC and NN. Shear force values were greatest for CN and were intermediate for CC. The difference in shear force (adjusted for variation in slaughter age) between homozygous genotypes (additive effect) was supported by calpastatin activity data with 2-df F-tests of 3.66 (P < .05) and 11.84 (P < .001) at d 0 and 7 postmortem, respectively. Corresponding values for the paternal polar overdominance effects on calpastatin activity were 53.80 (P < .001) and 87.43 (P < .001). Calpastatin ELISA data (d 0, adjusted for slaughter age) exhibited a paternal polar overdominance effect exclusively with a 2-df F-test of 57.63 (P < .001). Additive and paternal polar overdominance effects on marbling adjusted for slaughter age had F-tests of 6.41 (P < .01) and 93.29 (P < .001), respectively. Consequences of increased longissimus shear force must be addressed if the advantages of CN lambs for dressing percentage and carcass composition are to be realized. Further research is needed to establish whether selection targeted at changing the background genome can mitigate the negative effects of the C allele on meat tenderness.

Nematode burdens and cellular responses in the abomasal mucosa and blood of Florida Native, Rambouillet and crossbreed lambs

This experiment was carried out to compare the worm burden and cellular responses in the abomasal mucosa and blood of Florida Native and Rambouillet lambs and also in animals produced by crosses of these two breeds (generations F1 and F2). Animals were exposed to infection by gastrointestinal nematodes on three different occasions. The first infection was natural, occurring while they were suckling lambs. After weaning, they were kept indoors for 53 days and then were allowed to graze a contaminated pasture for 50 days for a second natural infection. The third infection was an artificial challenge with 6000 Haemonchus contortus infective larvae. The highest mean fecal egg counts (FEC) values were found in Rambouillet lambs followed in decreasing order by F1, F2 and Florida Native lambs. Throughout the trial, most of the high mean packed cell volumes and plasma protein levels were recorded in the F2 lambs; in contrast, most of the low values were found in the Rambouillet lambs. During the natural infection period, the highest percentages of larvae in the fecal cultures of the lambs were Haemonchus. However, high percentages of Trichostrongylus larvae were found particularly in Florida Native lambs. The mean number of blood eosinophils increased after the artificial challenge, reached a peak 21 days after infection and then declined. The highest and lowest blood eosinophil means were recorded in F2 and Florida Native lambs, respectively. The H. contortus burden was significantly higher in Rambouillet and in F1 lambs than in Florida Native and F2 lambs ( p < 0.05), while no significant differences were recorded among eosinophil, mast cell and globule leucocyte counts in the abomasal mucosa ( p > 0.05). The highest correlation coefficient recorded at the end of this study was between FEC and worm burden ( r = 0.7). These two parameters showed a moderate negative correlation with PCV, plasma protein and mast cell counts in the abomasal mucosa. The results obtained in this study indicate that crossbreeding Florida Native and Rambouillet sheep can be a rapid way to combine and improve the characteristics of these two breeds. The parasitological results were promising, however, more studies will be necessary to verify the impact of crossbreeding in other traits.

Evaluation of the ovine callipyge locus: I. Relative chromosomal position and gene action.

Genotypic and phenotypic data were collected to estimate chromosomal position of the callipyge (CLPG) gene and to test gene action. Nine Dorset rams of extreme muscling phenotype and 114 Romanov ewes composed the grandparent generation of a resource flock of 362 F2 lambs segregating at the CLPG locus. The parent generation consisted of eight F1 sires and 138 F1 dams. The F2 lambs were serially slaughtered in six groups at 3-wk intervals starting at 23 wk of age to allow comparisons at different end points. A linkage group of 25 marker loci (mean of 708 informative meioses per marker) spanning 87.2 cM was developed and improved the previous known coverage and precision of marker order and interval distance from available maps of ovine chromosome 18. Probabilities of each CLPG genotype were calculated at 1-cM intervals (0 to 107 cM). Statistical models included effects of year, sex, sire, regressions on genotypic probabilities, and genotype-specific linear and quadratic regressions on appropriate covariates. Orthogonal contrasts of CLPG genotypic effects evaluated additive, maternal dominance, and paternally derived polar overdominance models of gene action. The most parsimonious model did not include the additive and maternal dominance genetic contrasts. From analyses of four key traits, a consensus for position of CLPG was obtained at 86 cM relative to the most centromeric marker. An F-test with 3 df representing polar overdominance was maximum at position 86 cM (F = 407.4; P < .00001) with leg score as the dependent variable. These results are consistent with assignment of the CLPG locus to the telomeric region of chromosome 18 and support the polar overdominance model of gene action proposed by Cockett et al. (1996). Furthermore, recombinant individuals with definitive phenotypes confined the position of CLPG to a 3.9-cM interval, facilitating positional cloning experiments.

Evaluation of the ovine callipyge locus: II. Genotypic effects on growth, slaughter, and carcass traits.

A resource flock of 362 F2 lambs provided phenotypic and genotypic data to estimate effects of callipyge (CLPG) genotypes on growth, slaughter, and carcass traits. Lambs were serially slaughtered in six groups at 3-wk intervals starting at 23 wk of age to allow comparisons at different end points. Probabilities of CLPG genotypes were calculated at a position 86 cM from the most centromeric marker of chromosome 18. A contrast of CLPG genotypic effects, based on the paternal polar overdominance model, was used to evaluate callipyge and normal phenotypes. Relationships of traits with slaughter age, carcass weight, or 12th-rib fat depth for callipyge and normal phenotypic groups were estimated by regression. Callipyge and normal lambs did not differ for growth traits measured from birth to slaughter. Callipyge lambs produced 55.9% of live weight as chilled carcass weight compared with 51.7% for normal lambs at the same mean live weight of 48.32 kg. Lighter pelt, kidney-pelvic fat, and liver weights contributed to this advantage of callipyge lambs for dressing percentage (P < .001). Estimated accretion rates of carcass protein at the mean slaughter age were 12.5 and 10.2 g/d for callipyge and normal carcasses, respectively. Corresponding values for carcass fat were 35.2 and 42.1 g/d. Compositional differences in favor of callipyge carcasses were detected at constant values of slaughter age, carcass weight, and 12th-rib fat depth. Callipyge carcasses had 2.56 kg greater fat-free lean and 1.39 kg less fat than normal carcasses at the same mean age of 214.9 d (P < .001). The majority of these differences were established before the initial group was slaughtered and were maintained as age increased. Callipyge carcasses consisted of 24.3% fat and 71.3% fat-free lean, compared with 31.5 and 64.0% for normal carcasses at 25.6 kg of carcass weight. When evaluated at .49 cm of 12th-rib fat depth, callipyge lambs were 15.4 d older and produced 4.1 kg heavier carcasses with 4.3% less fat (P < .001). Effects of CLPG genotypic groups on carcass composition were greater than virtually all reported breed substitution effects. Use of the CLPG mutant allele in structured mating systems can dramatically increase production of lean lamb.

Environmental and maternal effects on early postnatal growth of lambs of different genotypes

Two important North European sheep breeds (the purebred Flemish Milksheep (M) and Suffolk (S) breed) were double reciprocally crossed to develop a highly fertile ewe genotype (SM × MS or F2, called the K.U. Lovenaar), which was finally crossed with Texel sires to improve carcass and slaughter characteristics of the final slaughter lamb genotype: F3 or T × F2. Birth weight, birth date, litter size, number of suckling lambs, age of ewe and sex of lambs had a significant influence on early postnatal growth rate ( P < 0.001). The significantly positive influence of birth weight on earliest postnatal growth rate diminished with increasing age of lambs. Age of ewes affected increases of lamb weights by having an important effect on birth weight. Lambs of 1-year-old ewes were characterized by a significantly lower birth weight and postnatal growth rate compared with lambs of multipareous ewes. A negative effect of litter size was observed on birth weight and on early postnatal growth results until 10 kg. Ram lambs had a higher birth weight and realized better growth until 16 kg, compared with results of ewe lambs. Significant effects of date of birth were also observed. Without correction for significant effects, variation in postnatal growth rate was about 30%. Growth rate of final slaughter lamb genotypes F3, T(MS) and T(F2fix) were significantly different. F3 and T(MS) lambs realized a significantly lower growth rate at 16 kg than T(F2fix) lambs (respectively, 324, 302 and 359 g day −1). However, the number of days needed to reach 16 kg was significantly higher for T(F2fix) lambs due to the low growth performance from 6 to 10 kg. F2 lambs had the highest growth rate of 370 g day −1, while F2fix lambs realized the lowest postnatal growth: 283 g day −1. Variation in postnatal growth rates decreased after correction for the significant effects. Early postnatal growth performance of slaughter lamb genotypes T(MS), F3 and T(F2fix) were comparable (about 320 g day −1 at 16 kg), but were still significantly lower than the excellent growth rate of F2 lambs (404 g day −1). They did not differ in growth data from MS and F2fix lambs. For selection on early postnatal growth one has to take into account maternal and environmental influences.

Inheritance of birthweight and growth traits in crosses between the Booroola Merino and Assaf sheep breeds

Data on birthweight, pre and post weaning growth rates and 150 day weight of 1058 Assaf (As), Booroola Merino (B) × As (F1), F1 × As ( 3 4 As ), As × F1 ( 3 4 As′ ), As × 3 4 As ( 7 8 As ) and B × F1 ( 3 4 B ) lambs were analyzed. Genotype, sex of lamb, genotype by sex interaction, crop, type of birth and sire within genotype had significantly ( P< 0.05) affected the different traits. Assaf lambs had the highest and 3 4 B lambs had the lowest birthweights. A negative relationship was found between the birthweight and the proportion of the Booroola blood in the lamb and its mother. As, F1, 3 4 As, 3 4 As′ and 7/8As ram lambs did not differ significantly ( P> 0.05) in their post weaning growth rate and in their 150 day weight. Similar situation was found among ewe lambs except for F1 ewe lambs which were significantly ( P< 0.05) smaller than Assaf ewe lambs at 150 days indicating sex linked effect on growth in the Booroola-Assaf crosses. The Assaf transmitted effects were positive and significant ( P< 0.05) for birthweight, post weaning growth and 150 day weight, and the Assaf maternal effect was positive and significant ( P< 0.001) for birthweight. Significant ( P< 0.001) heterosis was found for post weaning growth rate. Sex linked and recombination effects were significant ( P< 0.01) for pre weaning growth.

The effect of breed type and inbreeding on characteristics of the fleece and skin of 12-week-old lambs

ABSTRACTSheep of three pure breeds, the Scottish Blackface, South Country Cheviot and Welsh Mountain, and the crosses among these breeds, were inbred mostly by younger-parent offspring matings for three generations. Observations on lambs at 12 weeks of age were weight of fleece per unit area of skin, mean and variance of fibre length, both primary and secondary follicle density, and fibre diameter. The observations were analysed for the effects of inbreeding of the lamb and its dam, breed type, parity, and the sex and birth type of the lamb. Variation in the traits was also analysed for their relationship to lamb's live weight.Secondary follicle density and the density ratio (Ns/Np) decreased with inbreeding of the lamb. Primary follicle density increased whilst secondary fibre diameter and mean fibre length decreased with inbreeding of the dam. The effects of inbreeding on the density ratio and on secondary fibre diameter were correlated with inbreeding effects on the lamb's 12-week live weight. For other traits inbreeding did not have a clear-cut effect. Heterosis observed in F2 lambs was in general greater than that previously recorded for F1. For mean fibre length and mean fibre diameter the comparison of the crossbred deviations from mid-parent of the F2 and inbred lambs suggested epistatic interactions were involved. The effect of inbreeding crossbreds and inbreeding purebreds was different for secondary follicle density and primary fibre diameter, the two traits most clearly exhibiting heterosis in the F2. Lambs from first parity ewes had finer primary fibres and lighter fleece samples than had lambs from later parities.

Genetic and Environmental Effects on Postweaning Growth and Carcass Merit of Crossbred Lambs

Postweaning average daily gain (ADG), carcass weight per day of age (CWDA), dressing percent (DP), quality grade (QG), yield grade (YG), fat thickness (FT), percent kidney fat (KF) and leg conformation score (LS) were analyzed within subgroups on 320 F1 lambs from 2 years and 366 three-breed-cross lambs from three groups in 2 years. The F1 lambs were from Suffolk or Columbia-type range ewes mated to North Country Cheviot, Dorset, Finn-sheep or Romney rams. Three-breed crossbred lambs were progeny of F1 ewes of those same crosses mated to Hampshire rams. There was a tendency for higher CWDA from Cheviot and Dorset than from Finnsheep and Romney crossbreds, while Suffolk crosses had higher ADG and CWDA than Columbia crosses. Differences among both sire and dam breeds for DP and QG were small and not consistent. Suffolk crossbreds were superior to Columbia crossbreds for YG. There was a tendency for greatest FT from Romney crosses, while Suffolk crosses generally had less FT than Columbia crosses. Higher KF was found in Finnsheep F1 lambs than in other crosses, but differences between Suffolk and Columbia crosses were small. Among sire breeds, Finnsheep crossbreds had lowest LS. Suffolk crosses had higher LS than Columbia crosses. Sire × dam breed interactions were small and not significant. Effects of environmental variables (age of dam, type of birth and rearing, sex, management environment and regression on age or carcass weight) were also evaluated.

Performance of Romney and crossbred sheep on east coast hill country

Abstract A total of 1250 Romney ewes was divided into 5 flocks each of 250 sheep. Two flocks were used to breed Perendales by crossing the Romney ewes with either Cheviot or Perendale rams. Two more flocks were used to produce Border-Leicester × Romney sheep (Border-Romneys), by crossing the Romney ewes with either Border-Leicester or Coopworth rams. The fifth flock was kept as straightbred Romneys. The five flocks were run together from 1969 to 1972 under hill country conditions typical of that of the east coast of the North Island. Lamb birth, weaning, and fleece weights were recorded, as well as reproductive performance of the ewes expressed as barrenness, multiple birth rate, lamb survival, lamb weaning percentage, and weight of lamb weaned. Breed differences were small in all traits recorded and failed to reach significance. The most important breed differences were in weaning weight of F1 lambs where all breeds exceeded the Romney. Also, this trait was the only one in which the Cheviot and Border-Le...

Observations on Merino × Herdwick hybrid sheep with special reference to the fleece

1. Observations, mainly concerning the fleece and pigmentation, were made on about 80 F1 Merino × Herdwick sheep. Of these, nine were used for intensive fleece studies, and skin samples were obtained from six.2. Pigmentation in all the F1 lambs was greatly reduced as compared with the Herdwick breed, the majority being entirely white on the main fleece area, with varying amounts of black and brown speckling on the face, legs and neck. A few were entirely white, like the Merino. The shade of colour of the Herdwick dam did not affect the amount of pigment on her half-Merino offspring.3. The fibre type array most frequently encountered was one not previously described, which has been named Incline. Fine Plateau arrays were also frequent, especially on the mid-side and britch positions. Other arrays which occurred were Coarse Plain, Fine Plain, Ravine, and Coarse Plateau.4. The hogg fleece weights averaged approximately 4·5 lb. for females and 5 lb. for males, which is about double the average weight of Herdwick hogg fleeces. In general appearance they showed some superficial resemblance to Romney and Corriedale fleeces, but there was much variation between individuals. None closely resembled either parental fleece type, but the Merino influence was much more manifest than the Herdwick. Kemp, if present, was usually long and fine, resembling hair.5. Growth of the experimental animals was normal. In an endeavour to assess conformation, measurements were taken on a few sheep, and compared with similar measurements on Herdwick and Swaledale.6. The follicle population showed characteristics of both parental breeds, and varied greatly between individuals. The highest S/P ratio was 9·0, with a follicle density of 3000 per sq.cm. In comparison with the British breeds previously studied, autumn and winter fibre shedding was delayed and reduced in the crossbreds.7. Thetotal number offibresper tattooed square remained stable after sample 2 (about 2 months old). There was no significant difference between sheep or between samples in percentage of coarse, medium and fine fibres, but there was a highly significant difference between positions S (shoulder), A (last rib), B (britch) and D (rump). Mean fibre density was approximately 3000 per sq.cm., and mean fibre quality proportions (by number) in the A position was coarse 10%, medium 24% and fine 66%.8. Nearly 85% of the total clean weight of wool produced was grown in the late spring and summer months. The total wool grown was divided into three qualities and the proportion of the total weight derived from each quality was coarse 23·69%, medium 41·21%, and fine 35·10%. The distinction between the three qualities was often quite doubtful and never as clear as in the Herdwick breed. There were significant differences in proportions of coarse, medium and fine wool, between regions, between seasons and between sheep.9. In the discussion, which concludes the series of studies of fleece and follicle population, the following topics are treated: error of estimate of proportions in work of this kind; time of development of post-natal secondary follicle, and theories of the possible influence of primary follicles on the development of secondary follicles; post-natal growth in size of follicles in Merino and other breeds; autumn moult; recapitulation in follicles during regrowth after fibre shedding; significance of fibre type arrays; origin of the Longwool breeds; protective birth-coats; pigmentation; ‘lift’ in British wools; and the possibilities of establishing a breed with the Merino type of fleece on British hill and mountain farming areas.