The effect of the maturity and prior breeding activity of rams and body condition score of ewe hoggets on the reproductive performance of ewe hoggets

Abstract

AIM: To determine the effect of age and prior use of mature rams at a given ram-to-ewe ratio, and the effect of body condition on breeding performance and pregnancy rate of ewe hoggets.

METHODS: Ewe hoggets (n=733) aged 7–8 months were weighed and their body condition scored, then randomly assigned to one of three treatment groups (Day 0) and joined with either four two-tooth rams (20 months of age) not used previously (n=244; Two-tooth), four mixed-aged mature rams that had not been used earlier in the season (n=244; Mature-fresh), or four mixed-aged mature rams that had been used with mature ewes immediately prior to joining with hoggets (n=245; Mature-used). The breeding period was 34 days. Ewe hoggets were identified as having been marked during the first 17 days only, during both 17-day periods, during the second 17 days only, or not marked. Hoggets were re-weighed on Day 34, and pregnancy status determined using ultrasound on Day 92. The breeding soundness of the rams was assessed on Days ?34 and ?1.

RESULTS: Semen samples obtained from the rams did not differ significantly in any of the parameters measured (p>0.05). Ewe hoggets joined with Mature-fresh rams were less likely (p<0.05) to be marked in the second 17 days of breeding only than those joined with either Two-tooth or Mature-used rams. No other breeding parameters were affected by breeding group (p>0.05). Hoggets marked in the first 17 days only were heavier (p<0.05) at Day 0 than those marked in the second 17 days only or not marked. Hoggets diagnosed as twin-bearing were heavier (p<0.05) than non-pregnant or single-bearing hoggets. Those hoggets marked in the first 17 days only had a greater (p<0.05) body condition score (BCS) than those marked in the second 17 days only or not marked at all. These differences were no longer apparent after correction for liveweight (LW).Correction for LW at Day 0 or change in LW during the breeding period did not affect the results for breeding performance.

CONCLUSIONS: Under the conditions of this study, two-tooth rams and mature rams that had been used previously were just as suitable as mature rams that had not been used previously for breeding with ewe hoggets. Further studies are warranted to verify this result. The re-use of rams without reducing breeding performance would reduce breeding costs and may make breeding hoggets a more viable option for farmers. The BCS of ewe hoggets affected breeding performance, and can thus be used to identify those animals most suitable for breeding.     

The Cause of Black Blotch Disease of the Raspberry

Summary

Actively growing, single-stemmed plants of three black currant cultivars, each with 15 – 16 nodes, were exposed to photoperiods of 10, 14, 15, 16, 17, 18, 20, and 24 h at 18°C for 8 weeks for determination of the critical photoperiods for growth cessation and floral initiation. In all three cultivars, growth cessation was induced by short day (SD) conditions, with a critical photoperiod of 16 h, and the response was advanced by decreasing the photoperiod. The critical photoperiod for 50% flowering was 16 h in the cultivars ‘Öjebyn’ and ‘Ben Tron’, and 17 h in ‘Kristin’. Unexpectedly, however, not all plants flowered after exposure to a 10 h photoperiod, and the number of flowers per plant increased several-fold as the photoperiod was increased from 10 h to 15 h in all cultivars. Apparently, this unexpected result was due to the fact that all plants had only 15 – 16 nodes at the start of the experiments, which is marginal for “ripeness to flower” in black currant. While growth cessation was almost immediate in a 10 h photoperiod, causing only a few additional leaves to be formed during the experiment, the slower response to longer photoperiods apparently enabled the plants to reach the critical size at an earlier stage of the treatment period. However, although plants with 15 – 16 nodes were only marginally responsive to SD induction, buds situated as far down the shoot as the fifth or sixth node were competent to flower. It is therefore suggested that the inability of small black currant plants to flower resides in limitations of the leaves to respond to SD and to produce a florigenic signal, while their buds are fully competent to respond to such a signal.     

Improvement of mineral nutrient content of tomato through selection of cultivars and soil fertility

Depleted soil fertility and high-yielding cultivars have been associated with low nutrient contents in vegetables. This study explored if elemental nutrient concentrations in tomato (Lycopersicon esculentum Mill.) can be increased through selection of cultivars and nutritional regimes. Cultivars with different phenotypes of heirloom and modern origins were studied in field experiments in two years. Chemical fertilizer (10-10-10), compost, and an organic fertility regime of soybean meal, bone meal, and potassium sulfate were assessed for their effects on growth and composition of fruits of the cultivars. Differences in nutrient concentrations between modern or heirloom cultivars or among fertility treatments were small or non-significant. Differences among individual cultivars for each element were large with some cultivars having nearly twice the concentrations of nutrients of others and with considerable uniformity in cultivar rankings among the elements. This work suggests that cultivars can be selected for production of nutrient-dense tomatoes.     

Modulation of diversity by grazing and mowing in native tallgrass prairie

Species diversity has declined in ecosystems worldwide as a result of habitat fragmentation, eutrophication, and land-use change. If such decline is to be halted ecological mechanisms that restore or maintain biodiversity are needed. Two long-term field experiments were performed in native grassland to assess the effects of fire, nitrogen addition, and grazing or mowing on plant species diversity. In one experiment, richness declined on burned and fertilized treatments, whereas mowing maintained diversity under these conditions. In the second experiment, loss of species diversity due to frequent burning was reversed by bison, a keystone herbivore in North American grasslands. Thus, mowing or the reestablishment of grazing in anthropogenically stressed grasslands enhanced biodiversity.     

Gas-phase ionic reactions: dynamics and mechanism of nucleophilic displacements

Nucleophilic displacement reactions (the SN2 reaction) of ions in the gas phase are a prototypical reaction system that allows a study of dynamics, mechanisms, and structure-energy relations. This article reviews aspects of the kinetics (especially the applicability of statistical reaction rate theory), the relation of structure and reactivity, and the effects of small numbers of solvent molecules on the reaction and compares the behavior of the ionic reaction in the gas phase with that in solution.     

Cambrian burgess shale animals replicated in clay minerals

Although the evolutionary importance of the Burgess Shale is universally acknowledged, there is disagreement on the mode of preservation of the fossils after burial. Elemental mapping demonstrates that the relative abundance of elements varies between different anatomical features of the specimens. These differences reflect the compositions of the minerals that replicated the decaying organism, which were controlled by contrasts in tissue chemistry. Delicate morphological details are replicated in the elemental maps, showing that authigenic mineralization was fundamental to preserving these fossils, even though some organic remains are also present.     

Some intestinal parasites of Arctic fox, Banks Island, N. W. T.

Small intestinal parasitology of 50 trapped Arctic fox taken on Banks Island, The Northwest Territories, showed a prevalence of Taenia crassiceps (78%), Toxascaris leonina (60%), Echinococcus multilocularis (2%) and Coccidia (2%). Attention is drawn to the absence of Toxocara sp. and of Uncinaria sp.