ALBERT

Description: 〈div data-abstract-type="normal"〉〈p〉The importance of spring grass in the diet of early lactation dairy cows has been widely acknowledged. Numerous studies completed on a plot/paddock basis have identified methods of increasing herbage availability in spring, but little focus was placed on how this impacts animal production. The aim of the current study was to investigate the impact of opening farm cover (OFC; grass availability on farm at turnout in spring; 1036 (high), 748 (medium) and 544 (low) kg DM/ha) and spring rotation length (fast – 56 days and normal – 63 days) on animal performance in early lactation and herbage production and quality. Spring rotation length had little effect on animal performance, herbage variables or sward composition. High OFC increased pre-grazing herbage mass, allowing for increased daily herbage allowance (DHA) compared to medium and low OFC. There was a reduced proportion of leaf in the sward of the high OFC compared to the low OFC, resulting in lower organic matter digestibility. Despite the reduction in sward quality observed as a consequence of achieving high OFC in spring, the greater DHA available to animals increased milk production (+1.4 kg milk/cow/day). Additionally, animals grazing a medium or low OFC had a greater requirement for silage supplementation in spring (+1.3 kg DM/cow/day). The benefits of the higher DHA highlighted in the current study suggest that autumn grazing management must be adapted to increase herbage availability in spring. However, the benefits observed in milk production did not persist beyond the first grazing rotation.〈/p〉〈/div〉

Description: SummaryMature cyclic ewes were treated intravaginally with sponges impregnated with 30 mg SC-9880 (G. D. Searle) or intramuscularly with 100 μg Cloprostenol (I.C.I. 80, 996) and examined subsequently for oestrus, ovulation and fertilization. At 70 h after the end of treatment, 90% of ewes treated with SC-9880 and 45% of those treated with Cloprostenol had ovulated. Of ewes yielding eggs at 100 h a significantly higher proportion of SC-9880 treated sheep showed evidence of fertilization (69% v. 7%).

Description: It has been shown (Gordon, 1975) that certain progestagens administered intravaginally can be highly effective in the control of oestrus, ovulation and fertility in ewes. Prostaglandin (PGF2α) when infused into the uterine vein ipsilateral to the ovary containing the corpus luteum has been shown to result in luetolysis and a return to oestrus in a high proportion of ewes (Hearnshaw, Restall & Gleeson, 1973). Synthetic analogues of PGF2α have also been shown to have a marked luteolytic effect in ewes (Baird & Scaramuzzi, 1975). Variable fertility has been reported following the use of prostaglandin or its analogue for oestrous synchronization (Jennings, 1975; Haresign, 1976; Fairnie, Cumming & Martin, 1976; Lightfoot, Croker & Marshall, 1976; Trounson, Willadsen & Moor, 1976). Low fertilization has been reported after the use of a prostaglandin analogue and artificial insemination at a predetermined time in ewes (Boland, Gordon & Kelleher, 1978). The purpose of the present experiment was to extend these observations, using a ram in natural service after employing a double prostaglandin injection regime or an intravaginal progestagen treatment for the control of oestrus in cyclic sheep.

Description: With the development of effective methods of oestrus synchronization (Gordon, 1975), it is now possible to breed ewes at most times of the year. Encouraging conception rates have been reported following insemination (Colas & Brice, 1970; Colas et al. 1973; Gordon, 1975). A major disadvantage with the technique is the need to inseminate ewes twice at 10–14 h intervals. Because of the anatomy of the ovine cervix, it is not possible to deposit semen in the uterus as in the bovine. The present experiment was designed to compare a single or double insemination with natural service. Two types of inseminating gun were employed in an effort to deposit semen deep in the cervical folds.

Description: Quantitative information concerning preejaculation sexual preparation of bulls was published some years ago by Collins, Bratton & Henderson (1951), who concluded that about 40% more motile sperm could be obtained by imposing one false mount before ejaculation. It had been suggested that one false mount in bulls is essentially as efficient as two such attempts in terms of sperm output (Branton, D'Arensbourg & Johnston, 1952). More recently Hafs, Knisely & Desjardins (1962) have shown that bulls given a planned 5 min sexual preparation yielded 30% more sperm than those given no preparation. Similarly 10 min preparation resulted in a 12% increase in sperm output when compared with a 5 min preparation. These authors also showed that zero, one, two or three false mounts significantly affected motile sperm output.

Description: The importance of spring grass in the diet of early lactation dairy cows has been widely acknowledged. Numerous studies completed on a plot/paddock basis have identified methods of increasing herbage availability in spring, but little focus was placed on how this impacts animal production. The aim of the current study was to investigate the impact of opening farm cover (OFC; grass availability on farm at turnout in spring; 1036 (high), 748 (medium) and 544 (low) kg DM/ha) and spring rotation length (fast – 56 days and normal – 63 days) on animal performance in early lactation and herbage production and quality. Spring rotation length had little effect on animal performance, herbage variables or sward composition. High OFC increased pre-grazing herbage mass, allowing for increased daily herbage allowance (DHA) compared to medium and low OFC. There was a reduced proportion of leaf in the sward of the high OFC compared to the low OFC, resulting in lower organic matter digestibility. Despite the reduction in sward quality observed as a consequence of achieving high OFC in spring, the greater DHA available to animals increased milk production (+1.4 kg milk/cow/day). Additionally, animals grazing a medium or low OFC had a greater requirement for silage supplementation in spring (+1.3 kg DM/cow/day). The benefits of the higher DHA highlighted in the current study suggest that autumn grazing management must be adapted to increase herbage availability in spring. However, the benefits observed in milk production did not persist beyond the first grazing rotation.

Description: In exploiting to the full the possible advantages of a synchronized oestrus in ewes, the mating management of the ram requires special attention. Previous recommendations (Gordon, 1963) on ram management stated that progestagen-PMSG synchronized ewes should be run with rams at a ram to ewe ratio of 1:10 in the days following treatment. Preliminary work from this laboratory has shown that delaying the introduction of rams until 48 h following sponge withdrawal could improve conception rates significantly (Joyce, 1972). The purpose of the present experiment was to investigate further the effect of time of ram introduction on ewe fertility following oestrous synchronization.

Description: SUMMARYA detailed survey was undertaken to assess the rate of production and current management practices on Irish sheep farms and quantify their associations with flock size and ewe breed type. A total of 39 questions relating to the farm production system and farm management practices were devised, including: producer age, location, farm size, livestock numbers and type, in addition to flock management data such as flock breeding policy, lamb finishing strategy, flock health, lambing date, winter housing and feeding practices. A total of 717 sheep producers were surveyed across 45 different discussion groups. The surveyed respondents were sub-divided into four groups depending on flock size (very small, small, medium and large) and into three groups depending on ewe breed type (maternal, terminal and hill). The average survey respondent was 48 years old, with a flock size of 150 breeding ewes on a farm size of 58 ha. The average stocking rates were 6·55 and 3·14 ewes/ha and weaning rates were 1·44 and 1·02 lambs per ewe joined to the ram for the lowland and hill flocks, respectively. Relative to very small flocks (190 ewes) had higher stocking rates (6·98v.5·66 ewes/ha) and ewe to ram ratios (40v.30), and tended to lamb later in the year. The rate of technology adoption such as faecal egg sampling and pregnancy scanning was greater on larger flocks compared with smaller flocks. Flocks with maternal ewe breeds had higher scanning and weaning rates, and drafted a greater proportion of lambs off grass compared with flocks with terminal and hill ewe breeds. Flocks with maternal and terminal ewe breed types were more likely to winter house ewes, lamb indoors, test silage quality and have a handling unit compared with flocks with hill-type ewe breeds. Results from the present study provide a bank of knowledge on current Irish sheep industry performance and show that flock size and ewe breed type have a significant impact on key flock performance variables.