Lamb productivity of various purebreds and crossbreds were evaluated at the Centre for Food and Animal Research (formerly Animal Research Centre). Breeds included one newly developed synthetic sire and two dam strains of sheep (Arcott breeds) selected for growth and reproduction, and the Suffolk and Finnsheep. Crossbreds consisted of single crosses between the two dam strains, and three-breed cross lambs sired by either the synthetic sire strain or Suffolk breed. In a controlled environment, ewes lambed at 4-month intervals in 8-month breeding cycles while lambs were raised artificially from birth on milk replacer and high-energy diets formulated to meet nutrient requirements according to stage of production. In a semi-intensive management system, ewes lambed in 12-month breeding cycles while lambs were raised with their dams, similar to the management prevailing in a number of farm flocks across Canada. Research results demonstrated considerable promise for increased growth and reproductive performance in the newly developed synthetic strains and their crosses. Concurrently, at the University of Manitoba, one synthetic dam strain and the Suffolk breed, their crosses, and three-breed cross lambs sired by either the synthetic sire strain or the Hampshire breed were evaluated. This occur-red under conditions of semi-intensive management in 8-month breeding cycles following accelerated lambing procedures widely accepted by the Canadian sheep industry where the lambs are raised with their dam. Furthermore, studies at the University of Minnesota demonstrated potential genetic merit for milking ability in the two dam strains and their crosses when these were compared to North American sheep breeds. There was agreement that sheep breeders across Canada were to be given an opportunity to benefit from the release of the Arcott breeds. In 1989, the three synthetic strains were registered as new Canadian sheep breeds (one sire strain, the Canadian Arcott, and two dam strains, the Outaouais and Rideau Arcotts) and subsequently released. Since then, these sheep have been adapting to a wide variety of management and environmental conditions in Canada to the benefit of the sheep industry. The Canadian Arcott has demonstrated genetic merit as a meat-type terminal sire breed. The Rideau Arcott, a fecund-type dam breed with superior milking ability, has been well accepted by breeders and is presently the second highest for number of sheep registered in Canada. In contrast, the Outaouais Arcott, a fecund-type dam breed, has not achieved popularity. (C) 2003 Elsevier B.V. All rights reserved.

In the 1970s a multi-disciplinary research program was initiated at the Centre for Food and Animal Research (formerly Animal Research Institute) by introducing newly developed technologies in quantitative genetics, reproductive physiology, nutrition and housing, which had not previously been applied to the management of sheep production. The East Friesian, Finnish Landrace and Ile de France breeds from continental Europe with inherent potential for increasing productivity were imported and assembled with established breeds in North America to develop multi-breed synthetic populations. In 1972, the genetic base of the newly formed populations were closed to any further introduction of new breeding animals. Thereafter, these populations were selected for growth and reproductive performance to develop one specialized synthetic sire and two dam strains. Correspondingly, the Suffolk and Finnish Landrace breeds were maintained as random bred populations to monitor genetic response in the selected sire and dam strains, respectively. The three newly developed strains housed indoors year-round in a controlled environment were divided into two flocks. Concurrently, the use of artificial lighting regimens and exogenous hormones to synchronize estrus in ewes followed by exposure to rams in January, May and September, at the end of a period of short days initiated lambings in February, June and October, at 4-month intervals in 8-month breeding cycles. Growing lambs were raised from birth artificially on milk replacer and high energy diets, to allow maximum expression of their genetic potential, while adult sheep were fed diets to meet nutrient requirements according to stage of production. Genetic parameters estimated for growth and reproduction from the sheep raised in a controlled environment were in the favourable direction. Annual genetic response over 20 years of selection for early growth traits was approximately 1% of the mean realized. As well, there was a reduction in lamb mortality and an increase in fecundity. The morphological characteristics and production performance of the sire and dam strains have been described and compared with the reference breeds, Suffolk and Finnish Landrace. The newly developed synthetic sire strain (Canadian Arcott) demonstrated potential merit for use as a meat-type terminal breed, while the two synthetic dam strains (Outaouais and Rideau Arcotts) had outstanding productivity for use as fecund-type dam breeds.

Lamb productivity of various purebreds and crossbreds were evaluated at the Centre for Food and Animal Research (formerly Animal Research Centre). Breeds included one newly developed synthetic sire and two dam strains of sheep (Arcott breeds) selected for growth and reproduction, and the Suffolk and Finnsheep. Crossbreds consisted of single crosses between the two dam strains, and three-breed cross lambs sired by either the synthetic sire strain or Suffolk breed. In a controlled environment, ewes lambed at 4-month intervals in 8-month breeding cycles while lambs were raised artificially from birth on milk replacer and high-energy diets formulated to meet nutrient requirements according to stage of production. In a semi-intensive management system, ewes lambed in 12-month breeding cycles while lambs were raised with their dams, similar to the management prevailing in a number of farm flocks across Canada. Research results demonstrated considerable promise for increased growth and reproductive performance in the newly developed synthetic strains and their crosses. Concurrently, at the University of Manitoba, one synthetic dam strain and the Suffolk breed, their crosses, and three-breed cross lambs sired by either the synthetic sire strain or the Hampshire breed were evaluated. This occurred under conditions of semi-intensive management in 8-month breeding cycles following accelerated lambing procedures widely accepted by the Canadian sheep industry where the lambs are raised with their dam. Furthermore, studies at the University of Minnesota demonstrated potential genetic merit for milking ability in the two dam strains and their crosses when these were compared to North American sheep breeds. There was agreement that sheep breeders across Canada were to be given an opportunity to benefit from the release of the Arcott breeds. In 1989, the three synthetic strains were registered as new Canadian sheep breeds (one sire strain, the Canadian Arcott, and two dam strains, the Outaouais and Rideau Arcotts) and subsequently released. Since then, these sheep have been adapting to a wide variety of management and environmental conditions in Canada to the benefit of the sheep industry. The Canadian Arcott has demonstrated genetic merit as a meat-type terminal sire breed. The Rideau Arcott, a fecund-type dam breed with superior milking ability, has been well accepted by breeders and is presently the second highest for number of sheep registered in Canada. In contrast, the Outaouais Arcott, a fecund-type dam breed, has not achieved popularity.

Mixed model methodology based on a multi-trait animal model was used to estimate genetic trends for lamb weights in three synthetic Arcott (Canadian Outaouais and Rideau) breeds and two random bred control (Suffolk and Finnish Landrace) breeds. Selection in the Canadian Arcott was primarily on lamb weight at 91 d with a lesser emphasis on litter size. Outaouais and Rideau Arcotts were selected primarily for litter size with a lesser emphasis on lamb weight at 91 d. All lambs were housed indoors year-round in a controlled environment under conditions of artificial rearing and 8-mo breeding cycles. Genetic improvement over 20 yr based on predicted breeding values for lamb weights at birth, 21, 70 and 91 d of age were 0.3, 0.9, 2.1 and 2.8 kg, respectively in the Canadian, 0.2, 0.6, 1.2 and 1.5 kg in the Outaouais, and 0.3, 0.5, 0.9 and 1.4 kg in the Rideau breeds. Corresponding values for the unselected Suffolk were 0.3, 0.4, 0.4 and 0.5 kg, respectively, and for the Finnsheep were 0.2, 0.2, 0.3 and 0.5 kg. Alternative methods of estimating genetic trends using control populations were based on deviation of the predicted mean year-season phenotype in the selected breeds from that in the corresponding random bred control breeds (Suffolk for Canadian, and Finnsheep for Outaouais and Rideau) and also as a deviation from the year-season estimate in the corresponding random bred control breeds. Genetic trends estimated from the alternative methods, which took into account the contribution of drift, were larger than those based on predicted breeding values. These values were reflected in the realized heritabilities estimated from regression of cumulative selection differential on the genetic trends. In the Arcott breeds, annual genetic trend for lamb weights varied according to breed and the estimation procedure which amounted to 0.25–0.81% of the mean. It is evident selection offers one of the most practical means for rapid and permanent improvement of early lamb growth in multi-breed synthetic populations under conditions of artificial rearing, 8-mo breeding cycle and a controlled environment. Key words: Sheep breeds, genetic trends, multi-trait animal model and growth traits

This study is based on analyses of genetic and non-genetic differences in survival and body weights of 2250 lambs, and ewe productivity based on 1151 ewe records. Lambs were derived from the Arcott breeds (Outaouais and Rideau; two synthetic dam strains developed at the Animal Research Centre, Ottawa, Canada), their two-breed crosses, the Finnish Landrace (unselected control), and specific three-breed crosses sired by the Canadian Arcott (a synthetic sire strain also developed at ARC) and the Suffolk breed. Year of birth, sex of lamb, age of dam or ewe, type of birth and rearing had important influences. Fertility, prolificacy, fecundity, gestation length and total lamb weights per ewe lambing were similar among the Outaouais and Rideau ewes, whereas Rideau ewes weighed more at breeding than the Outaouais ewes. The reproductive performance of Finnish Landrace ewes was similar to that of Outaouais and Rideau ewes. In contrast, Finnsheep lambs had significantly lower body weights at birth, 56 days and 91 days than those of Outaouais and Rideau lambs. Finnsheep ewes were lighter at breeding and produced less total lamb weight per ewe lambing. Crossbred ewes from inter-mating of the Outaouais and Rideau breeds were similar to their purebred contemporaries in prolificacy and total lamb weight per ewe lambing (at 56 and 91 d of age). Purebred ewes of the Rideau breed were more fertile than their crosses but did not differ in fecundity. There appeared to be an overall trend in favor of specific three-breed crosses compared to the Outaouais and Rideau breeds, and their crosses. Growth performance was similar in specific three-breed cross lambs derived from rams of the Canadian and Suffolk breeds mated to Outaouais and Rideau cross ewes. The results demonstrate improved productivity of the newly developed Arcott breeds and their crosses, in terms of outstanding reproductive ability and rapid growth.

Abstract Body weights of 6066 lambs and ewe productivity based on 3579 records in an 8-mo breeding cycle were analysed. Lambs were from three synthetic Arcott breeds (Canadian, Outaouais and Rideau; one synthetic sire strain and two synthetic dam strains), their two dam strain crosses, the Suffolk and Finnish Landrace (two unselected control) breeds, and specific three-breed crosses sired by the Canadian and Suffolk breeds. Important influences of year-month of birth, sex of lamb, age of dam or ewe, type of birth were observed in a controlled environment (housed indoors year-round on expanded metal mesh floors in windowless barns with light controlled by time clocks). Canadian ewes were more fertile and fecund than Suffolk ewes, but similar in gestation length and weight at breeding. Body weights of Suffolk lambs at 21 d and 91 d of age were significantly lower than those of Canadian lambs. Although Rideau ewes weighed more at breeding than Outaouais ewes, fertility, prolificacy, fecundity, total lamb weights at 21 d and 91 d of age per ewe lambing and lamb survival were similar. Reproductive performance of Finnsheep ewes was similar to Outaouais and Rideau ewes (P>0.05). In contrast, Finnsheep lambs had significantly lower body weights than Outaouais and Rideau lambs. Ewe weight at breeding and total lamb weight per ewe lambing were lighter in Finnsheep ewes than Outaouais or Rideau ewes. Although not significant, purebred Outaouais and Rideau ewes excelled in growth and reproductive performance compared to their crossbred contemporaries. Growth performance of specific three-breed cross lambs from rams of the Canadian and Suffolk breeds mated to Outaouais and Rideau cross ewes were similar. Although not significant, there was an overall advantage in favour of specific three-breed crosses compared to the Outaouais and Rideau breeds, and their crosses. Specific three-breed cross lambs were similar to purebred Canadian lambs in body weight. Results demonstrated that the Arcott breeds and their crosses had outstanding reproductive ability and rapid growth rate in a controlled environment with artificial rearing of all lambs and 8-mo breeding cycles.

Two experiments were performed in order to determine the best method for evaluation of weight-gaining ability of lambs. Lambs on unrestricted access to feed and water (full fed) gained 2–3% of live weight on the following day while lambs deprived of feed and water (fasted) overnight gained 0–3%. However, full fed lambs lost 5–10% of live weight when fasted overnight, or gained 7–10% if full fed at night. In 38 to 43% of the lambs fasted overnight, weights measured at successive weigh days were identical, a higher proportion than in lambs subjected to other treatments. Estimates of intra-class correlations between weights on successive days in lambs fasted overnight prior to weighing, or full fed until weighing, ranged from −8 to 0%. Corresponding estimates for lambs fasted overnight followed by full feeding, or vice versa, were highly variable, due to differences in weight of gastro-intestinal and urinary tract (‘fill’) contents and ranged from 8 to 60%. There appears to be no justification for weighing on successive days when a single accurate weighing equals the average weight. It was concluded that overnight withdrawal of feed and water before weighing reduced significantly the variation in body weight associated with retention of feed and water, facilitating a more precise assessment of lamb's growth potential.

Age at puberty, fertility and litter size of ewe lambs of synthetic sire and dam strains raised under different photoregimens were determined. The lambs were bred during January, May or September at 30 to 32 weeks of age. Irrespective of birth date, the lambs were reared under continuous light from birth to 5 weeks of age. From 5 to 20 weeks of age, they were kept under 16 hours of light dairy (16L:8D; Treatment A), 8 hours of light daily (8L:16D; Treatment B), or a split photoperiod of 8 hours total light daily (7L:9D:1L:7D; Treatment C). Subsequently, all lambs were exposed to 9 hours of light daily until after breeding. Lambs were exposed to rams for two estrous periods after treatment with fluorogestone acetate-impregnated intravaginal sponges and pregnant mares' serum gonadotropin (PMSG) to induce synchronized estrus. Although the age at puberty (174 days) was similar among treatments, the incidence of puberty prior to progestagen sponge treatment was higher (approximately 50%) for lambs reared under Treatments A and C than under Treatment B. Fertility and litter size of lambs were not influenced by the previous photoperiod history or by sexual maturity, i.e., puberal or prepuberal, at the start of the sponge treatment. However, strain, age and weight of lambs at breeding influenced significantly the reproductive outcome.

This study was based on analysis of records of gestation length, prolificacy, multiple birth, body weight and total birth weight for 7,083 ewes of the Arcotts (Canadian, Outaouais and Rideau; three synthetic strains developed at the Animal Research Centre, Ottawa, Canada), Suffolk and Finnish Landrace (Finnsheep) breeds. Sheep were housed indoors, in a controlled environment. Ewes divided into two flocks with equal contribution of genetic material were bred in January, May and September months at the end of a period of short days, to lamb alternately at 4-month intervals under an 8-month breeding cycle. Breed, prolificacy, year and breeding season has significant effects on gestation length of the ewe. The Canadian Arcott and Suffolk ewes, both meat-type sire breeds, had gestation lengths of 147 and 146 days, respectively, compared to 145 days for Outaouais and Rideau Arcott ewes and 144 days for Finnsheep ewes, all fecund-type dam breeds. There was a progressive reduction of gestation length within breed as prolificacy increased from ewes bearing single to quintuplet lambs. Though significant, the magnitude of the breeding season effects was negligible. Sex of lamb, age and body weight of the ewe had no influence on gestation length (P>0.05). Heritability based on paternal half-sib estimates for both gestation length and prolificacy was 0.18. The estimates of genetic and phenotypic correlations between gestation length and prolificacy were 0.09 and 0.06, respectively. Although the frequency of multiple birth is highly variable, its heritability estimate of 0.04 and its positive genetic correlation with gestation length of 0.43, indicates multiple birth would not be a useful selection criterion for reducing gestation length. Selection for prolificacy, despite its 40–43% variability, would have little effect on gestation length because of the poor correlation between the two traits. Therefore, to reduce a 21-week gestation length by one week, despite the 2% variability in gestation length, direct selection for shorter gestation appears to be the best option. It is doubtful that there would be any economic advantage in reducing gestation length by selection in view of the limited reduction achievable.

A total of five data sets obtained from four separate sheep flocks were used to evaluate the effects of subclinical maedi-visna virus infection (as determined by serological procedures) on productivity in ewes. In general, infection with maedi-visna virus had a detrimental effect on productivity. Infection resulted in a reduction in conception rates, with the odds of an infected ewe conceiving being only approximately 0.67 times those of a non-infected ewe. For ewes which did conceive, there was no detrimental effect of infection on the number of lambs born. The birth weights of lambs born to middle-aged (3–4 years) infected ewes were 3–6% lower than the weights of lambs born to non-infected ewes of the same age. There was very little apparent effect of infection in younger (1–2 years) and older (5 + years) ewes: some factors which may have biased these results are discussed. Lamb weights at 25–50 days of age appeared to be reduced by maedi-visna infection in the ewe but the results were not statistically significant.

Six hundred sixteen ewes of six strains were inoculated twice with ovalbumin in Freunds' incomplete adjuvant. To quantify the humoral immune response to the foreign antigen, blood samples were collected from all ewes 1 wk post-second injection. Blood samples were also collected between 4 and 40 h of age from their 709 lambs, to examine genetic differences in ability of lambs to acquire maternal anti-ovalbumin antibodies. Titers of anti-ovalbumin antibodies were determined using kinetic enzyme-linked immunosorbent assay (ELISA) techniques. Strain did not affect ewe immune response, but sire within strain was highly significant. In pregnant ewes, anti-ovalbumin antibody titers in 12- and 30-mo-old ewes were higher than those in 21-mo-old ewes. Number of lambs in utero did not significantly affect ewe immune response. Heritabilities of anti-ovalbumin titer from a paternal half-sib analysis were .27 +/- .17 for all ewes and .57 +/- .25 for only the pregnant ewes. The effect of strain of lamb on lamb anti-ovalbumin titer approached significance, and sire within strain was highly significant. Lamb anti-ovalbumin antibody concentration increased as time from birth to blood sampling increased to 18 h but declined thereafter. The size of the litter in which a lamb was born had a highly significant effect on the lamb's acquired immunity, with titer decreasing as litter size increased. The heritability estimate for lamb anti-ovalbumin antibody concentration from a paternal half-sib analysis was .38 +/- .11; it was .28 +/- .15 from the sire variance component of a full-sib analysis. When lamb titer was considered a maternal trait (lambs nested within their maternal grandsires within strains), the maternal grandsire variance component was negative. The average anti-ovalbumin antibody concentration of lambs that died between blood sample collection and 120 d of age was less than the average antibody concentration of lambs that survived (P less than .01).

Two artificial rearing experiments were conducted to evaluate both preweaning and postweaning performance of artificially reared lambs, ad libitum fed a milk replacer having one-third of the milk protein replaced by soyflour protein (S) compared with those fed MR with all the protein provided by milk products (M). From weaning at 21 d of age to 91 d of age all the lambs were fed the same high-concentrate diet. In the first experiment there were no significant differences in lamb weights, daily gains, postweaning feed conversion or lamb survival. In the second experiment there were lower (P < 0.05) postweaning daily gains, lower (P < 0.05) 91-d weights and higher (P < 0.05) postweaning feed conversion (2.69 vs. 2.52 kg feed kg−1 gain) for S lambs compared with M lambs, although there were no significant differences due to MR treatment for weaning weights, preweaning daily gains or lamb survival. In both experiments the S lambs consumed slightly more MR than M lambs. Using prices prevailing at the time of the study the lower ingredient cost of the soyflour resulted in a saving in MR cost of $1.45 per lamb weaned. In the second experiment, the lower MR cost would have been partially offset by the approximately 1 kg extra liveweight per lamb at 91 d of age. It was concluded that soyflour could contribute one-third of the total protein in MR for ad libitum fed, artificially reared lambs with little, if any, reduction in lamb performance. However, savings in feed costs resulting from the cheaper ingredient cost might be partially offset by lower postweaning lamb gains. Key words: Lambs, artificial rearing, milk replacer, soy protein

Genetic and phenotypic relationships among carcass traits were calculated for 654 ram lambs from 210 sires of three synthetic strains developed at the Animal Research Centre. Lambs were housed indoors in a controlled environment on expanded metal floors and reared artificially with milk replacer and solid diets. Paternal half-sib estimates of heritability at 36-kg body weight and 116 of age were moderate to high ranging from 0.38 to 0.67 for shoulder and leg (trimmed and lean), total trimmed retail cuts, total lean, chilled carcass weight and lean weight per day (P < 0.01). Estimates of phenotypic and genetic correlations between the above traits showed a significantly favorable relationship indicating their usefulness as criteria in selection for meatiness. Heritability estimates for front, back and total in rough retail cuts, trimmed loin cuts, lean in rack and loin, kidney fat weight and dressing percentage ranged from −0.19 to 0.27 (P > 0.05). Estimates involving loin, rack, front, back, total retail cuts, kidney fat wt, dressing percentage and chilled carcass weight per day showed lower and nonsignificant relationships with total trimmed retail cuts or total lean. Key words: Sheep, heritability, genetic and phenotypic correlations, lamb carcass traits

This study involved body weights of 6078 lambs from 525 sires of two synthetic dam strains developed at the Animal Research Centre with 50% Finnish Landrace background. Breeding was practiced in flocks A and B for lambing at 4-mo intervals under an 8-mo breeding cycle. Lambs were housed indoors in a controlled environment on expanded metal floors in windowless barns, reared artificially with milk replacer and solid diet from birth to weaning at 21 days of age. Thereafter, all lambs were fed solid diet to 70 days of age. Paternal half-sib estimates of heritability for lamb weights at birth, weaning, 49 and 70 days of age were 0.25–0.26. Heritability estimates in the two synthetic dam strains were in close agreement (P > 0.05). Genetic and phenotypic parameter estimates did not demonstrate any significant linear trends across lambing periods. The moderate levels of heritability estimates for lambs reared artificially under a controlled environment suggest that genetic response to selection could be enhanced by selecting lambs independent of potential maternal effects and competition among litter mates for a fixed quantity of milk. Estimates of genetic and phenotypic correlations among various lamb weights ranged from 0.60 to 1.00, and from 0.51 to 0.93, respectively. Lamb weights having closer proximity in time showed higher correlations. Moderate to high genetic correlations between body weight of lambs at different ages indicated that selection for weight at one age should cause no adverse effects on body weight at other ages. Key words: Sheep, artificial rearing, lamb weights, heritability, genetic and phenotypic correlations

Three hundred and sixty-four artificially reared lambs were weaned at 21 days of age, assigned to four treatments and raised in a controlled environment. The 2 × 2 factorial experiment involved two diets containing 0.53% calcium (Ca) and 0.70% phosphorus (P) or 1.43% Ca and 0.50% P, respectively, with half of the lambs on each diet receiving two intramuscular injections (IMD) of vitamin D3 (250 000 IU at weaning and 500 000 IU at 70 days of age). The diets with the high Ca:P ratio produced higher rates of gain. Those lambs receiving IMD had slower growth rates compared to those receiving only dietary vitamin D. In all treatments, serum Ca levels were within normal ranges while serum P levels were higher than normal. Treatment differences in serum Ca were similar, though less consistent, to those observed for growth, whereas only inconsistent treatment differences occurred for P or alkaline phosphatase activity (AP). Although a few positive correlations were noted among serum parameters per se irrespective of treatment, they were without a general pattern. There were, however, positive correlations between growth rates and both serum AP and serum Ca activities, particularly at later stages of growth. The results indicated that a dietary Ca:P ratio of 2.9 was conducive to satisfactory growth, that high levels of vitamin D via injection were not beneficial and that measuring serum Ca, P and AP as indices of nutritional status is of little use as a practical management tool. Key words: Calcium, phosphorus, alkaline phosphatase, vitamin D, lambs

In two artificial rearing experiments lambs were fed, ad libitum, either cold (4.4–7 °C) or warm (27–31 °C) milk replacer with 0.10% formalin (37%, wt/wt, formaldehyde) added to the reconstituted milk replacer. From weaning at 21 days of age to 91 days of age all lambs were fed the same high-concentrate diet (corn grain, soybean meal, 8% ground hay plus minerals and vitamins; approx. 17% crude protein, as-fed). In the second experiment half the lambs from each milk replacer treatment were fed alfalfa hay free-choice postweaning in addition to the high-concentrate diet. Equal survival rates and absence of abomasal bloat on both milk replacer treatments showed that the addition of 0.10% formalin allows warm milk replacer to be safely fed ad libitum to lambs. Both intakes and gains were higher for lambs fed warm milk replacer than for cold. In the first experiment apparent compensatory postweaning growth nullified the weight advantage at weaning for lambs fed warm milk replacer, whereas in the second experiment the weight advantage at weaning was not overcome by the apparent compensatory growth. Feeding hay free-choice postweaning (amounted to 12.5% of the overall diet), in addition to the high-concentrate diet, improved lamb gains and slightly increased feed dry matter required per kilogram of gain, as would be expected as a result of the lower energy content of the overall diet. The results indicate that the addition of 0.10% formalin allows warm milk replacer to be safely fed ad libitum to lambs; that performance, including postweaning carryover effects will be equal to, or greater than that achieved with cold milk replacer; and that free-choice hay in addition to a high-concentrate diet postweaning has a beneficial effect on lamb performance. Key words: Lambs, artificial rearing, warm vs. cold milk replacer

Operator effects and instrument accuracy in using the Scanopreg ultrasonic pregnancy detector in sheep bred at synchronized estrus were studied in three experiments. In the first study, four operators tested the same 101 ewes at 60 and 80 days after breeding. The only significant difference among the four operators was that one operator consistently underestimated pregnancy. Operators did not differ in their diagnoses between days 60 and 80. In the second study, there were no differences between two operators who tested 239 ewes 90 days after breeding. In the third study, one operator tested 318 ewes 60, 70 and 90 days after breeding. The accuracy of diagnosis of pregnancy was at least 90% on each day tested; the corresponding diagnoses of nonpregnancy were 52, 76 and 79% correct. Some ewes that were initially diagnosed as nonpregnant were correctly recognized as pregnant when tested later than day 60. Most of the missed pregnancies were in ewes carrying a single lamb. A second Scanopreg test on day 90 of ewes not diagnosed pregnant on day 60 or 70 identified additional ewes as pregnant. Paired tests (days 70 and 90) recognized 99% of the ewes that eventually lambed.

During an outbreak of chronic copper poisoning, fecal and urinary copper excretion were measured following treatment with molybdenum and sulfur supplementation of the feed (0.1 g ammonium molybdate plus 1 g sodium sulfate/sheep/day) or oral penicillamine (50 mg/kg bodyweight/day) using rams in metabolism cages. Serum glutamic-oxaloacetic transaminase activities and liver levels of molybdenum and copper in sheep that died were also monitored. Within four days of starting molybdenum and sulfur supplementation a highly significant increase in fecal copper excretion was evident and the increase persisted throughout the monitoring period (five weeks - general treatment of the flock continued for another three weeks). There was no effect of the molybdenum and sulfur supplementation on urinary excretion of copper. The molybdenum and sulfur supplementation was very effective, resulting in a rapid marked decrease in mortality. Oral penicillamine treatment induced cupruresis but did not affect fecal copper excretion. The results indicated that, while the cost of penicillamine may be a limiting factor for general treatment of a flock, it may be the drug of choice for the therapy of valuable breeding animals because cupruresis may be accurately and individually controlled. Serum glutamicoxaloacetic transaminase activities were a valuable aid in diagnosing chronic copper toxicosis as well as for monitoring recovery. High initial liver copper levels were gradually reduced following molybdenum and sulfur treatment. However, at the end of the study the liver copper levels of dead sheep varied within wide limits and there were still some sheep with high liver copper levels.

Heart girth (HG), body length (BL), leg length (LL), metacarpal circumference (MC), withers height (WH) and hook width (HW) of 233 growing rams of three synthetic strains, Suffolk and Finnsheep breeds were measured at 6, 8 and 10 mo of age. Thereafter, subsequent measurements were taken at 11–13 mo, 18–21 mo and 23–25 mo of age. Breed, birth period (hysterectomy derived birth date), age of ram and body weight (BW) had important effects (P < 0.05) on linear body measurements, whereas age of dam did not (P > 0.05). Significant effects of litter size on HG and BL were observed at 6 and 8 mo of age, respectively. All linear body measurements increased from 6 to 21 mo of age, whereas BL, WH and HW continued to increase to 25 mo. Rams of Strain 1, developed as a synthetic sire strain, with a large proportion of Suffolk background were generally similar to the Suffolk rams in all body measurements except for HG which was significantly larger than in Suffolk rams. The Finnsheep rams had smaller HG, BL, MC and HW than the synthetic strains and Suffolk rams, whereas LL and WH of the Finnsheep and Suffolk rams were similar. Rams of Strains 2 and 3, developed as synthetic dam strains with 50 percent Finnsheep background, were similar in body measurements. The synthetic dam strains did not differ from Strain 1 and/or Suffolk with respect to HG, BL, WH and HW. However, Suffolk rams had larger MC and shorter LL compared to those of the Strain 2 and 3 rams. Birth period had a significant effect on HG, BL, LL and MC, but no consistent trend with age of ram was apparent. Linear body measurements were positively correlated with each other and with body weight; however, the relationship varied as rams progressed in age. The importance of breed, birth date, age of ram and body weight on body measurements and the requirements for appropriate adjustments is emphasized. Key words: Sheep, body measurements, breed, birth date, age of ram