Time of feeding and predictability of dry matter and water intake of grasscutters fed on grass and supplements containing varying levels of dietary fiber.

The study evaluated the feeding behavior of growing male grasscutters (Thryonomys swinderianus) fed freshly cut Panicum maximum, supplemented with pelletized concentrates containing varying levels of dietary fiber. In a two-stage 4 × 4 Latin square arrangement, the relationships between water and dry matter intakes as influenced by dietary characteristics were investigated by offering supplements either at 09:00 h (morning) during the first stage or at 17:00 h (evening) during the second. Each test period lasted for 14 days with a 1-week rest period between changeovers. Time of feeding significantly (P < 0.05) affected total dry matter intake (DMI) and intake of the supplements, with the total DMI increasing by 21% when the diets were offered in the evening relative to when offered in the morning. Regression analyses showed significant (P < 0.05) correlations between dry matter (DM) and water intakes against some dietary characteristics. The current study has shown that crude fiber (CF) inclusion of up to 14% in pelletized supplements for growing grasscutters consuming a basal diet with CF up to 31% may not affect feed and water intake, as well as acceptability of the feed. However, feeding such supplements in the evening could stimulate higher feed intake. Also, dietary DM better predicted DMI compared to the other dietary characteristics.

Embryonic resorption, litter size and sex ratio in the grasscutter, Thryonomys swinderianus.

This study was conducted using 210 whole uteri collected from hunters' kills from July 2006 to March 2007 at Esiam and Sokode in the Ekumfi and Ho Districts respectively; and data on 148 dams from eight farms in the Greater Accra Region of Ghana from January to December 2007. The objective of the study was to investigate the effects of embryonic resorption, litter size and parity on sex ratio in the grasscutter. Embryonic resorption rate, which occurred at all stages of pregnancy, ranged between 41.3% and 47.2%, and was not biased towards male or female offspring. The rate of resorption also had no effect on sex ratio (r=-0.011, P=0.396). The study also showed that litter size in the grasscutter could be improved if embryo resorption is controlled. Primiparous dams had offspring with a sex ratio of 0.43+/-0.020 which was not significantly different from dams of parities 3 (0.47+/-0.040) and > or =4 (0.53+/-0.053). Parity 2 dams, however, had a significantly higher proportion of males (0.54+/-0.024). There was a tendency towards a decreasing proportion of males as litter size increased but the overall sex ratio observed in the farmed grasscutter (0.48) did not deviate significantly from the theoretical sex ratio of 0.50.

On the use of the perineal stain as an index of sexual maturity and breeding condition in the male greater cane rat, Thryonomys swinderianus, Temminck.

The efficacy of the perineal stain as an index for sexual maturity and breeding condition in the male greater cane rat, Thryonomys swinderianus, Temminck, was investigated in 34 animals collected from hunters' kills in the Ekumfi District of Ghana, between April and June 1989. The results indicated that, although the presence of the perineal stain was conclusive proof of sexual maturity in an individual, it was not efficacious as an index for sexual maturity for biological work in these animals (p > 0.05) because it excluded some that, although sexual mature, did not exhibit the trait, particularly young adults. However, the perineal stain may be useful as a management tool for identifying sexually mature captive greater cane rats. About 7 out of every 10 caught each month were found to be in breeding condition.

Patterns of parturition and mortality in weaned greater cane rats (Thryonomys swinderianus, Temminck).

The patterns of parturition and mortality were studied in a colony of weaned captive greater cane rats, Thryonomys swinderianus, Temminck, from January to December 2000 at the Grasscutter Domestication Centre, Pokoase Research Station, Animal Research Institute, Ghana. The most important finding from the study was that it is practical to wean greater cane rats at 4 weeks of age with proper post-weaning management. Mortality ranged between 0 and 3.9% with an average of 1.4% for animals weaned at 4 weeks. Among the factors contributing to mortality in the weaned greater cane rats may be the number of animals per unit space. The mortality in this study was a marked improvement compared to that of 11% reported elsewhere for animals weaned at 6 weeks. The animals were, however, smaller at weaning compared to those in reports from elsewhere, probably owing to poor lactation by the mothers. Peak parturition occurred in October with captive breeding having no influence on the parturition pattern.

Efficacy of sex determination in the greater cane rat, Thryonomys swinderianus, Temminck.

The efficacy of the two most common techniques used for determining the sex of the greater cane rat, Thryonomys swinderianus, Temminck, was tested using 10 young and 8 adult animals with two technicians at the Animal Research Institute's Grasscutter Domestication Centre, Pokoase, Ghana. The techniques compared were the use of the head shape and/or head size and the use of the ano-genital distance. The use of the ano-genital distance for sex determination was validated in a colony of greater cane rats at various stages of development, i.e. from the day of birth to three or more years of age. The ano-genital distance was then used as the standard against which the use of the head shape and/or head size technique was tested. The results indicated that the use of the ano-genital distance for sex determination in the greater cane rat was error-free, even with little experience on the part of the practitioner. The ano-genital distance was more than twice as long in the males than in the females at all ages (p < 0.001). However, the use of the head shape and/or head size for sex determination was found to be associated with some degree of error in both sexes. The use of the ano-genital distance can therefore be recommended as an efficacious technique for sex determination in the greater cane rat.

The efficacy of the vaginal plug formation after mating for pregnancy diagnosis, and embyonic resorption in utero in the greater cane rat (Thryonomys swinderianus, Temminck).

The efficacy of the detection of vaginal plug formation after mating for pregnancy diagnosis, and the degree of embryonic resorption were studied in 67 wild greater cane rats (Thryonomys swinderianus) at Esiam in the Ekumfi District, Ghana, over a period of 3 months. Vaginal plug formation was first observed on day 59 of gestation, and could be used for pregnancy diagnosis on or after that date. However, the vaginal orifice subsequently opened a couple of times prior to day 105 of gestation and further checks for pregnancy after day 59 of gestation are suggested. Animals with unplugged vaginas 105 days after mating could, however, be considered as not pregnant. The mean (+/- SE) number of implantation sites and litter size in the greater cane rat were 7.2 +/- 0.18 and 3.4 +/- 0.29, respectively, the embryonic resorption rate being 42.7 +/- 6.66%. The significant positive correlation between the number of implanted embryos and the bled-out carcase weight suggests a positive role of maternal nutrition in increasing the litter size in the greater cane rat. The incidence of post-partum oestrus during the study period was 42.1%, which suggests that the greater cane rat can be re-bred immediately after parturition.

Reproduction and mortality in a colony of captive greater cane rats, Thryonomys swinderianus, Temminck.

The reproductive performance and mortalities in a colony of captive greater cane rats, Thryonomys swinderianus, were monitored from 1992 to 1998 at the Grasscutter Domestication Centre, Achimota, Ghana. The animals were kept in cages and exposed to constant lighting from a 100 W electric light bulb during the night. The diet consisted mainly of freshly cut Panicum maximum (guinea grass) fed ad libitum, with occasional supplements of cassava and cane sugar. The results indicate that the mean litter size and litter weight were 2.9 +/- 0.51 and 439.4 +/- 81.23 g, respectively. These figures are low compared to those reported elsewhere. However, the mean birth weight was 151.2 +/- 11.08 g, higher by 12% than previously reported values. It is considered that poor nutrition, excessive exposure to light and stress were responsible for the relatively poor reproductive performance reported in these animals. The main causes of death were traumatic injuries (32%) and pulmonary congestion (16%).

Smallholder farming of the greater cane rat, Thryonomys swinderianus, Temminck, in southern Ghana: a baseline survey of management practices.

Baseline management practices and productivity of captive greater cane rats were studied between February and July 1992 using questionnaires with 33 practising and former farmers in 16 villages in three regions in southern Ghana. The colony sizes were relatively small, ranging between 1 and 96, with nearly a 100% farmer drop-out rate. The mean litter size of the greater cane rats in this study was 4.8+/-0.13, with the young being weaned at 8.8 weeks old. Although nearly all the farmers interviewed (90.9%) had long-term commercial intentions, a number of problems militating against their objectives were encountered. These included lack of technical support on proper management practices for efficient production, housing design, dry season feeding, sex determination and the acquisition of foundation stock. In conclusion, these studies have shown the generally poor state of the greater cane rat industry in Ghana, which requires research into almost all aspects of the productivity of this animal under captive breeding.