RJ Kilgour’s research while affiliated with Centre for Eye Research Australia and other places

Relationships of ram serving capacity (a measure of serving frequency in pen tests), testis diameter, liveweight, breed and age with flock fertility were studied in 40 rams joined individually for 7 days at high ewe:ram ratios. Rams were either Border Leicester, BLI (a high prolificacy line derived from the Border Leicester and Merino and since released as the Glen Vale breed) or BLI x Border Leicester, and aged either 1.5 or 2.5 years. Joinings were over 2 periods, 2-9 April or 16-23 April. Breed, age, period and interaction effects were also examined. On average (± s.e.), the number of ewes with mating marks in 7 days increased by 2.03 ± 0.52 ( P < 0.001) per serve per hour of serving capacity and by 0.40 ± 0.18 ( P < 0.05) per kg liveweight. Relationships with pregnancy rate in marked ewes differed between classes of rams. Larger testes were of most benefit when rams were of high serving capacity ( P < 0.0 1 ) or low liveweight (P<0.01). Only serving capacity was related to number of ewes pregnant, the number increasing by an average (± s.e.) of 1.73 ± 0.57 ewes per serve per hour (P<0.01). This suggests that a ram's capacity for more frequent service was more important to fertility than was extra testicular tissue. BLI x Border Leicester, BLI, and 2.5-year-old Border Leicester rams impregnated 30-40% more ewes than did 1.5-year-old Border Leicester rams. We estimate that the 1.5-year-old Border Leicester rams could be satisfactorily joined to about 46 ewes and the other rams to about 60 ewes.

Sexual activity, serving capacity, mean number of mounts per serve and mean testis diameter were measured in 286 Border Leicester, BLI (a 'high fertility' sheep related to the Border Leicester) and BLI x Border Leicester rams at 1.5, 2.5 or 3.5 years of age. Rams were allowed two 20-minute introductory periods with spayed oestrous ewes, and then were given two 1-h pen mating tests during which their serving capacity (the mean number of serves in the two tests) and mounts per serve were counted. Rams which commenced mounting in introductory or 1-h tests were classed as sexually active. Among 1-5 and 2.5-year-old rams, 68.9 and 65.4%, respectively, were sexually active, while all 3.5-year-old rams were active. Mean testis diameters for inactive rams were smaller (P<0.05) than for active rams in both 1.5- and 2.5-year-old rams. There were breed type differences in activity, serving capacity and mean testis diameter at 1.5 years of age, but not at other ages. BLIs were less active at 1.5 years than other types, but BLIs and Border Leicesters did not differ in either their serving capacity or testis diameter. BLI x Border Leicesters generally had greater (P<0.05) serving capacities and testis diameters than other types, suggesting possible advantages for these rams at early joinings. Sire effects for serving capacity were not significant, but were significant (P<0.05) for mounts per serve, and for testis diameter at 1.5 years old. Activity status was highly repeatable (0.83) between 1.5 and 2.5 years and testis diameter was moderately repeatable (0.41). Repeatabilities for serving capacity and mounts per serve, in active rams, were not significant. Correlations between serving capacity and testis diameter were not significant for active rams, while serving capacity and mounts per serve were generally negatively related. Mean testis diameter was significantly (P<0.05) correlated with liveweight at 1.5 years but not at other ages. Liveweight at 2.5 years was positively (P<0.05) related to mounts per serve and negatively (P<0.05) related to serving capacity.

The mating performances of 15 rams which were initially sexually inactive were examined by allowing them constant exposure to three oestrous ewes per day. Two rams did not mount or serve any ewes in 17 days of exposure. When the 13 remaining rams began to raddle ewes their mating performance was compared with that of active rams. Active and inactive rams raddled and inseminated similar numbers of oestrous ewes, suggesting that inactive rams are adequate performers at loads of three oestrous ewes per day once they commence mating. Over a total of 12 h direct observation, however, inactive rams performed significantly fewer mounts and serves than active rams.

Two experiments were carried out to measure the mating behaviour of rams in pens. In the first, rams were tested for 1 or 3 h in a large number of tests, and records were taken of the number of mounts per test, serves per test, the ratio of mounts to serves, and the various time intervals between sexual activities. The number of serves per test was the most highly repeatable measure (0.66 ¦. 0.16 (¦ s.e.) for tests of 1 h and 0.66 ¦ 0.18 for tests of 3 h). Up to two introductory tests were required to allow rams to overcome apprehension and then to demonstrate their true serving behaviour. Tests of 20 min did not always detect differences between rams in serving behaviour. In the second experiment, the above results were validated on a large number of rams. It was further shown that the heritability of the number of serves per test was 0.33 ¦ 0.62. The frequency distribution of serves per test was shown to be skewed to the right.

Young Merino ewes on five commercial properties in northern New South Wales were supplemented with selenium and their production was compared with untreated flock mates. They were studied from weaning till first lambing at about two years of age. Treatments of 5 mg selenium were given orally every six weeks for approximately 12 months. Copper treatments were also included to test for a possible concurrent deficiency or interaction with selenium. There were significant responses to selenium in liveweight in four of the five flocks and in wool production in two of the flocks at both shearings. Reproductive performance at first mating was also significantly better in two flocks. There were no beneficial effects of copper treatment nor were there any significant interactions with selenium treatment in any aspect of production measured.

Responses in fertility after selenium supplementation of breeding ewes in northern New South Wales were examined. The treatment (5 mg selenium) was given orally as sodium selenite three weeks before joining, and responses were measured in terms of the proportion of ewes lambing. A total of 14 experiments was conducted on eight commercial properties over three years. In some flocks the effect of selenium supplementation on wool production and liveweight was also assessed. All sites were in areas of likely selenium deficiency. Selenium supplementation significantly increased the proportion of ewes lambing in 5 sf the 14 flocks studied but responses were quite variable between properties and years. The effect of supplementation on greasy wool production was small, but significant in two of the seven flocks measured. The treatment did not affect liveweight.

The effects of feral pigs on the lambing performance of Merinos was studied at Nyngan, New South Wales. Ewes lambed in two paddocks; one with feral pigs and one with no pigs in autumn and spring in 1978 and 1979. Ewes were pregnancy tested before lambing, and after lambing, classified as dry, lactating or lambed-and-lost. Lambs were mustered weekly in three lambings. Pig movement in three lambings was controlled by electric fences. There were effects (P < 0.05) of feral pigs, years, seasons, and pigs x years on the percentage of ewes lactating, of those lambing. Feral pigs lowered the number of lambs per 100 ewes by 37.9 and 31.9 in autumn and spring 1978, respectively. In 1979 pig predation was an insignificant cause of lamb loss.

Serving capacity was measured in nine Merino rams during two pen-mating tests each of 2 hours duration. Two groups each of four rams were subsequently formed; a high serving capacity group (group H) of mean serving capacity 11.50 ± 0.50 (SEM) in two hours, and a low serving capacity group (group L) of mean serving capacity 3.50 ± 0.62. Each group was then mated to separate flocks of approximately 200 ewes each, for 6 weeks. Group H rams raddled significantly more ewes during the first 16 days of mating and inseminated a significantly greater proportion of the raddled ewes than did group L rams. Estimates of fertilization rates and embryo loss were similar for both groups. The proportion of ewes lambing as a result of the 6 weeks mating was similar in both groups (95.3% in group H and 93.5% in group L).

The serving activity of seven rams in one 20-minute pen mating test followed by two one-hour pen mating tests was recorded. The mating performance of each ram during a single-sire flock mating was subsequently monitored. Mean number of services in the two one-hour pen tests gave the best prediction of the number of ewes inseminated during flock mating (r = 0.88, P < 0.01). The number of services in the 20-minute test gave a poor prediction of the number of ewes inseminated (r = 0.30). The total number of services during the first 20-minutes of the two one-hour tests (2x20-minute tally), the number of services during the 20-minute test and the first 20 minutes of the first one-hour test (2 x 20-minute tally) and the number of services during the 20-minute test and the first 20 minutes of the two one-hour tests (3x20-minute tally) were only moderately correlated with number of ewes inseminated (r = 0.67, r = 0.47 and r = 0.64, respectively). These results explain why other workers, using combinations of 20-minute tests, have failed to demonstrate a relationship between pen mating tests and flock fertility. The results further show that a measure of the serving activity of rams in pens can be used to identify rams that are capable of mating large numbers of ewes, and that the development of a commercially applicable test is worthwhile.