The effect of dietary protein on the pathogenesis of acute ovine haemonchosis

Two experiments were conducted to examine the ifluence of dietary proteins on parasite establishment and pathogenesis in Finn Dorset/Dorset Horn lambs infected with Haemonchus contortus. The lambs were introduced to high (169 g) or low (88 g crude protein (CP) kg⁻¹ dry matter (DM)) protein diets at 3 months of age and infected 1 month later with 350 larvae kg⁻¹ body weight (BW). Blood and faecal smaples were collected for analysis and body weights recorded weekly. In the first experiments some of the infected lambs were killed 6 weeks after infection and the remainder 5 weeks later. In the second experimental all the infected lambs were killed 4 weeks after infection.

The results showed that lambs on a low protein diet were less able to withstand the pathogenic effects of infection with 350 H. contortus larvae kg⁻¹ BW than lambs given the higher protein diet. Thus mortality was greater in the low protein group and adverse clinical signs, such as inappetance, weight loss and oedema were osbserved more frequently. This group also had a more severe anaemia, hypoproteinaemia and hypoalbuminnaemia than the high protein group. In contrast, faecal egg counts, total daily faecal egg output and worm burdens were similar in all groups of infected lambs, indicating that the diets did not influence parasite establishment.     

MAINTENANCE OF THE BLOOD LEVEL OF PENICILLIN AFTER INTRAMUSCULAR INJECTION

Blood concentrations of penicillin were maintained at measurable levels for as long as seven or eight hours following single intramuscular injections of penicillin in the dog and in patients by means of vehicles containing 6 per cent. to 20 per cent. ossein gelatin and a long-acting vasoconstrictor drug. Intramuscular administration of penicillin can thus be carried on with three instead of eight injections per day with less variation in the extremes of penicillin blood levels.     

Influence of dietary protein on the pathophysiology of haemonchosis in lambs given continuous infections

Mixed-sex groups of three-month-old Finn Dorset and Dorset Horn lambs were given complete diets containing either high or low protein. A trickle infection with Haemonchus contortus of 200 larvae, given three times a week, began one month later for a 17 week period. Erythrokinetic, metabolic, digestibility and balance studies were conducted with the male lambs during weeks 12 to 14 of the infection. Clinical signs of haemonchosis became evident only in the low protein diet group. The infection was characterised by severe macrocytic anaemia, hypoproteinaemia, hypoalbuminaemia, reduced survival, high egg counts and a significantly greater worm burden. In the high protein diet group many lambs developed resistance to further infection in contrast to the low protein group in which no resistance developed. Live-weight gain was not affected by infection in the high protein diet group but decreased in the lambs given the low protein diet compared with uninfected controls. However, infection did not appear adversely to affect the digestive efficiency, nitrogen retention or iron absorption in either dietary group although loss of appetite occurred in the low protein group. Examination of a sample joint from the carcases showed infection was associated with a marked reduction in muscle mass in lambs given the low protein diet relative to the control animals.     

Bovine ostertagiasis: a changing epidemiological pattern?

An unusual epidemiological pattern in bovine ostertagiasis is described in which clinical ostertagiasis occurred in calves grazed on a silage aftermath from late July. The calves were treated with the anthelmintic levamisole prior to grazing the aftermath and the latter had not been grazed since the previous autumn. Analysis of the herbage larval counts suggests that delayed emergence of overwintered Ostertagia ostertagi L3 from the soil was the most likely source of the infection.     

A preliminary study on the suitability of Cervidil to induce cervical dilation for artificial insemination in ewes

The aim of this study was to evaluate the efficacy of Cervidil^®, a prostaglandin E₂ (PgE₂)-releasing vaginal insert used for induction of cervical ripening and labour in women, to enhance the ease of transcervical artificial insemination (TCAI) in anestrous ewes (June). It was hypothesized that the use of Cervidil^® prior to AI would cause dilation of the cervix, and thus alleviate the difficulty associated with traversing the cervix for semen deposition in sheep. Cervidil^® was inserted 12 h before insemination in six Rideau-Arcott ewes; six ewes served as untreated controls.Semen was deposited into the uterus of all six treated ewes but TCAI was possible only in four of the six control ewes. It can be concluded that Cervidil^® facilitated transcervical semen deposition in anestrous ewes. The treatment with Cervidil^® has the promise of a technique to improve transcervical AI and to enable non-invasive embryo transfer procedures in sheep.     

Influence of dietary protein on the pathophysiology of ovine haemonchosis in Finn Dorset and Scottish Blackface lambs given a single moderate infection

Two experiments were conducted to examine the influence of dietary protein on the pathophysiology of Haemonchus contortus in lambs of two breeds, namely Finn Dorset and Scottish Blackface. Erythrokinetic and metabolic studies using 51Cr-red cells, 59Fe-transferrin and 125I-albumin, and digestive efficiency and nitrogen balance measurements were conducted between four and six weeks after infection. Identical radioisotopic and nutritional studies were also conducted on pair-fed control lambs of both breeds. The results demonstrated that in normal control animals, there were no significant effects of diet or breed on any of the erythrokinetic, metabolic or nutritional parameters, with the possible exception of red cell survival which was considerably longer in the Finn Dorset lambs. However, in the infected animals diet and breed did influence those parameters. The severest effects were seen in the infected Finn Dorset lambs given the low protein diet. These animals had the highest level of abomasal blood loss and this was associated with low red cell volumes and high levels of both albumin catabolism and plasma iron turnover. These animals were also in negative nitrogen balance which was partly accounted for by a significantly greater urinary nitrogen loss compared with their pair-fed controls and partly due to the poorer digestibility of the crude protein fraction of the diet. In contrast, although the infected Scottish Blackface lambs had high levels of blood loss and associated pathophysiological changes, these did not differ between dietary treatments and were similar to the changes in the infected Finn Dorset lambs given the high protein diet.