Effect of Modifying Ovarian Feedback on the Reproductive Performance of Highlands Half-Bred Ewes
Total Page:16
File Type:pdf, Size:1020Kb
Proceedings.book Page 662 Monday, September 17, 2001 11:30 AM Effect of Modifying Ovarian Feedback on the Reproductive Performance of Highlands Half-Bred Ewes Paul N. Manua* Abstract An experiment was conducted at Tambul Research Station, Western Highlands Province, PNG, to determine the response of highlands half-bred ewes to the steroid hormone Androject, injected eight and four weeks before the onset of mating. The aim was to determine the potential use of this method for increasing lamb production in the national and provincial sheep farms producing lambs for distribution to farmers. Ewes that received Androject showed a fecundity of 1.42 per ewe compared to 1.18 per ewe for the control group. The number of lambs weaned per 100 ewes in the treated and the untreated groups were 119 and 97 respectively. It appears that under the prevailing feeding and management conditions at Tambul Research Station, the use of a steroid immunising vaccine such as Androject may result in a significant increase in the fecundity of ewes. THE production of lambs by the national and the pro- output of lambs from the farm breeding centres, vincial sheep farms is inadequate to meet demand through modification of ovarian feedback using the from farmers. Production of lambs can be increased vaccine Androject. from available breeding ewes by increasing the repro- ductive rate of these animals but a major factor lim- iting reproductive rate is low ovulation rate (Hanrahan Materials and Methods 1980). Nutritional, photoperiodic, genetic or pharma- cological means can be used to manipulate ovulation The study was conducted at the Tambul Research rates (Cummins et al. 1984). Station in the Western Highlands Province of PNG. Recent advances in veterinary science make it pos- Tambul is at an elevation of 2300 metres above sea sible to increase the ovulation rate in sheep using a level. The original flock of 192 highlands half-bred vaccine. The vaccine modifies ovarian feedback on the ewes with a lambing rate of 115% in the previous year pituitary, neutralising the hormone that suppresses was divided randomly into two groups. The first multiple ovulation in ewes. As a result, the number of group was injected subcutaneously in the neck with multiple births increases. 2 millilitres of a commercial preparation of the vac- cine, eight and four weeks before the introduction of This paper discusses an attempt to enhance the the rams. The second group did not receive any reproductive rate of the breeding ewes, and hence the vaccine (controls). Both groups were fed and managed in the same ways. The breeding ewes were * Food Security, Erap Branch, Department of Agriculture grazed rotationally and mineral supplements were and Livestock, PO Box 1984, Lae 411, Morobe provided at all times. Breeding rams were withdrawn Province, PNG. after nine weeks of mating. During lambing, lambs 662 Proceedings.book Page 663 Monday, September 17, 2001 11:30 AM were identified, ear-tagged, weighed and recorded treated group, with 142 lambs born per 100 treated along with the dam number. All lambs were docked at ewes lambing, compared to 118 lambs born in the three weeks of age and weaned at three months of age. control group. Weaning weights were recorded. Influences of sex and lamb number on lamb Results and Discussion survival at weaning The influences of sex and birth type on lamb sur- Reproductive performance vival at weaning are presented in Tables 2 and 3 respectively. The lactating ewes were not able to find The effect of Androject on the reproductive per- high quality feed for adequate lactation and this formance of highlands half-bred ewes is presented in resulted in some ewes losing their lambs. The ratio of Table 1. Although the group that received Androject females to males at birth was 1:1.25 in the treated showed slightly higher fertility, the difference was not group and 1:1.11 in the control group. At weaning the statistically significant (P < 0.05). The group that sex ratio of the surviving lambs was 1:1.59 received Androject produced more lambs than the (female:male) in the treated group and 1:1.16 in the group that did not receive the hormone, with the control group. lambing rate (number of lambs born per ewe available The mortality in the treated group was 9.5% in the for mating) increased by 30% in the treated group. treated group compared to 4.1% in the control group. Fecundity was significantly (P < 0.05) higher in the All of the lambs that died in the treated group and three Table 1. Effect of Androject on the reproductive performance of highlands half-bred ewes. Group Number of Number of Number of Fertility (%) Fecundity (%) Lambing rate ewes at mating ewes lambing lambs born (%) Control 96 82 97 85.4 118.3 101.0 Treated 96 89 126 92.7 141.6 131.3 Table 2. Influence of sex on lamb survival in treated and control groups. Lambs Control Treated Male Female Total Male Female Total No. born 51 46 97 70 56 126 No. weaned 50 43 93 70 44 114 % survival 98.0 93.5 95.9 100 78.6 90.5 Table 3. Influence of lamb number on lamb survival in the control and treated groups. Lambs Control Treated Single Twin Triplets Single Twin Triplets No. born 68 26 3 56 58 12 No. weaned 66 24 3 56 51 7 % survival 97.1 92.3 100 100 87.9 58.3 663 Proceedings.book Page 664 Monday, September 17, 2001 11:30 AM of the four that died in the control group were females. number of lambs weaned. Ways to improve postnatal The survival rate in the treated group was influenced care of lambs from treated ewes should be investi- by the birth number, with losses considerably higher gated, to increase lamb survival rate. among the triplets, where ewes sometimes lost interest in mothering their newborn lambs. Acknowledgments I thank the New Zealand Government for providing Conclusion Androject and Mr Wasina for logistical assistance. The lamb numbers weaned per 100 ewes mated in the treated and the control groups were 119 and 97 respec- References tively. This shows that use of the steroid immunising Cummins, G., et al. 1984. The influence of hormones on agent Androject can significantly increase lambing reproduction in Merino ewes. Australian Journal of rates of highlands half-bred ewes, through an increase Agricultural Research, 30, 1133–1141. in fecundity. However, there is no indication that Hanrahan, J. 1980. Hormonal effect on the productivity of injection with Androject would result in any signifi- purebred Finnsheep in Finland and abroad. Livestock cant changes in fertility, female:male ratio, and Production Science, 4, 355–377. 664 Proceedings.book Page 665 Monday, September 17, 2001 11:30 AM Inland Fish Farming Kine Mufuape,* Mokra Simon* and Kunia Chiaka* Abstract Aquaculture is thought to be a good way to provide a more regular supply of protein to the PNG highlands. The Highlands Aquaculture Development Centre was set up in 1996 to provide technical advice, training and a supply of fingerlings to provinces and people who are interested in fish farming. The success of the project is indicated by increased attendance at training courses and increased purchases of fingerlings by fish farmers. PROTEIN intake in the highlands region is irregular. few fish farmers in East Sepik or Sandaun (West Most protein is taken as pork or lamb flaps or chicken Sepik) provinces (2%), the island provinces (1.5%) or at death ceremonies or Christmas functions. Aquacul- Oro (Northern) Province (1%). Lowland provinces ture is being introduced to remedy this dietary incon- like Madang and Morobe provinces are progressing sistency. Wild fish catches are likely to drop in the well with fish farming. future, so aquaculture will be increasingly important The Highlands Aquaculture Development Centre for PNG as its population increases. Aquaculture is (HAQDEC) was set up in 1996 to contribute to food more likely than fishing to deliver ownership of the security in the region by providing technical advice environment, a predictable supply of fish, quality con- and fingerlings to provinces and farmers who are trol, and the potential for genetic improvement. It is interested in fish farming. Its main functions are to also environmentally friendly. As well as producing produce fingerlings, conduct training and carry out much-needed protein, it can lead to greater employ- research. To help HAQDEC perform these tasks, the ment, human resource development and economic Japan International Cooperation Agency centre at diversification and increased export income. Condi- Aiyura has provided technical input to make sure the tions in PNG are apposite for aquaculture: the climate, region has sufficient institutional capacity, equipment, water and soil conditions are favourable; there are suit- infrastructure and trained personnel. The centre now able available species; there is sufficient labour, infra- has the facilities, equipment and staff to implement the structure and access to markets; and the country is project objectives. politically stable. Altogether, there are more than 5000 backyard fish farmers in the highlands. Our records and observations Fingerling Production suggest that most fish farmers are based in Eastern Highlands Province (32%), Simbu Province (25%) Figure 1 shows the number of fingerlings distributed and Morobe Province (20%). About 12% are based in from HAQDEC from 1992 to 1999. In 1992–94, pro- Western, Southern Highlands and Enga provinces and duction ranged from 13,288 to 64,147 fingerlings. about 6.5% in Madang Province. There are relatively After the aquaculture method was improved in April 1994, production increased steadily in most years; it * Highlands Aquaculture Development Centre, PO Box 280, increased from 180,007 in 1996 to 258,731 in 1999.