Age at puberty, fertility and litter size of ewe lambs reared under different photoregimens.

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.

Inheritance of active and acquired immunity traits in sheep.

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).

Copper poisoning in a flock of sheep. Copper excretion patterns after treatment with molybdenum and sulfur or penicillamine.

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.

Improved diagnostic accuracy by repetitive ultrasonic pregnancy testing in sheep.

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.

Bent-limb syndrome in lambs raised in total confinement.

A bent-limb syndrome in lambs raised in total confinement was characterized by curvature of the forelimbs. Radiographic findings included flaring of the affected long bone and thinning of the growth plate. The main histologic change was endochondral dysplasia of the long bone. In feed samples, all trace minerals analyzed were within recommended concentrations except iron, which was much higher (400 ppm dry matter) than the normal requirement of lambs (70 ppm). All mineral concentrations in serum were normal except those of inorganic phosphorus and iron, which were higher. Results of soft tissue and bone mineral analyses were normal. Altering the ratio of calcium and phosphorus did not affect the incidence of disease, but intramuscular administration of massive doses of vitamin D3 and reducing the amount of dietary iron had a prophylactic effect. The increase in serum phosphorus was probably related to the dietary excess of iron, which probably decreased vitamin D metabolite formation in the kidney, which in turn could be prevented by massive doses of vitamin D3.