2.8 References

Bailey, R.W., 1 967. Quantitative studies of ruminant digestion H. Loss of ingested plant carbohydrates from the reticulo-rumen. New Zealand Journal of Agricultural Research. 1 0, 1 5-32.

B arry, T.N, McNabb, W.e., 1 999. The implications of condensed tannins on the nutritive value of temperate forages fed to ruminants. British Journal of Nutrition. 8 1 , 263-272.

Drew, K.R, Fennessy, P.F., 1 980. Supplementary Feeding. Occasional Publication No. 7. New Zealand Society of Animal Production, Mosgiel, New Zealand. AgResearch Invermay. pp. 1 57- 1 84 .

Jackson, F . S . , McNabb, W . e . , B arry, T.N., Foo, Y L . , Peters, J . S . , 1 996. The condensed tannin content of a range of subtropical and temperate forages and the reactivity of condensed tannin with Ribulose- l , 5-his-phosphate carboxylase (Rubisco) protein. Journal of the Science of Food Agriculture. 72, 483-492. J efferies, B. C., 1 96 1 . Body condition scoring and its use in management. Tasmanian

Journal of Agriculture. 32, 1 9-2 1

Kemp, P.D., Mackay, A.D, Matheson, L.A., Timmins, M.E., 200 1 . The forage value of poplars and willows. Proceedings of the New Zealand Grassland. Association. 63, 1 1 5- 1 1 9.

Knight, T.W., Oldham, e.M., Lindsay, D.R., 1 975. Studies in ovine infertility in Agricultural Regions in Western Australia: the influence of a supplement of lupins (Lllpinlls angllstijolillS cv. Uniwhite) at joining on the reproductive performance of ewes. Australian Journal of Agricultural Research. 26, 5 67- 575.

Littell, Re., Henry, P.R, Ammerman, c.B., 1 998 . Statistical analysis of repeated measures data using SAS procedures. Journal of Animal Science. 76, 1 2 1 6-

1 23 1 .

Meier, B . , Julkunen-Tiitto, R , Tahvanainen, 1., Sticher, 0., 1 988. Comparative high­ performance liquid and gas-liquid chromatographic determination of phenolic glucosides in Salicaceae species. Journal of Chromatography. 442, 1 75-1 86. Min, B . R , McNabb, W.e., Barry, T.N., Kemp, P.D., Waghorn, G.c., McDonald, M.F.,

1 999. The effect of condensed tannins in Lotus corniculatus upon reproductive efficiency and wool production in sheep during late summer and autumn.

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Min, B.R., Femandez, J.M., Barry, T.N., McNabb, W . e . , Kemp, P.D., 200 1 . The effect of condensed tannins in Lotus corniculatus upon reproductive efficiency and wool production in ewes during autumn. Animal Feed Science and

Technology. 92, 1 85-202.

Moore, KM., B arry, T.N., Cameron, P.N., Lopez-Villalobos, N. Cameron, D J . , 2003 . Willow (Salix sp.) as a supplement for grazing cattle under drought conditions. Animal Feed Science and Technology. 1 04, 1 - 1 1 .

Rattray, P.V., Jagusch, K T. , Smith, IF., Winn, G.W., Maclean, K . S . , 1 980. Flushing responses from heavy and light ewes. Proceedings of the New Z ealand Society of Animal Production. 40, 34-3 7.

Rattray, P.Y., Jagusch, K T. , Smith, IF., Winn, G.W., Maclean, K. S . , 1 98 1 . Effects of genotype, liveweight, pasture type and feeding level on ovulation responses in ewes. Proceedings of the New Zealand Society of Animal Production. 4 1 , 1 74-

1 82.

Robertson, l B . , Van S oest, PJ., 1 98 1 . The detergent system of analysis and its application to human foods. In: lames W.P. T. & Theander, O. (Eds.), The analysis of dietary fibre in food. Marcel Dekker, New York, Chapter 8. pp. 1 23- 1 5 8 .

Roughan, P. G., Holland, R . , 1 977. Predicting in vi Iro digestibilities o f herb ages by exhaustive enzymic hydrolysis of cell walls. Journal of the Science of Food Agriculture. 28, 1 057- 1 064.

Salinger, l, 2000. The genesis of a new ark : Integrating preparedness for increasing climate variability and change. Managing the Impacts of Climate Variability: The Noah Paradigm. Proceedings of the New Zealand Institute of Agricultural Science and the New Zealand Society for Horticultural Science Annual

Convention 2000. pp. 3 1 -3 7.

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Smith, JF. Jagusch, K.T., Farquhar, P.A., 1 98 3 . The effect of the duration and timing of flushing on the ovulation rate of ewes. Proceedings of the New Z ealand Society of Animal Production. 43, 1 3- 1 6.

TerriIl, T.H., Rowan, A.M., Douglas, G.B . , Barry, T.N., 1 992. Determination of extractable and bound condensed tannin concentrations in forage plants, protein concentrate meals and cereal grains. Journal of the Science of Food and

Agriculture. 58, 32 1 -329.

Thompson, L.H., Goode, L., Harvey, RW., Myers, RM., Linnerud, A.c., 1 973 . Effects of dietary urea on reproduction in ruminants. Journal of Animal Science. 3 7, 2, 399-405 .

Towers, N.R, 1 997. Pasture as a source of Fusarium toxins in New Zealand. 1 9th Mycotoxin Workshop, Munich. Institut fur Hygiene und Technologie der Lebensmittel tierischen Ursprungs Tierarztliche FakuItat, Ludwig-Maximilians­ Universitat Miinchen. pp 1 5- 1 9.

Van S oest, PJ., Robertson lB . , Lewis, B .A., 1 99 1 . Symposium: carbohydrate

methodology, metabolism, and nutritional implications in dairy cattle. Methods of dietary fib er, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74, 35 83-3 597 . Waiters, RJ.K., Evans, E . M . , 1 979. Evaluation of a sward sampling technique for

estimating herbage intake by grazing sheep. Grass and Forage Science. 34, 3 7- 44.

Ward, c., 1 999. MAP clarifies fanngate drought cost estimates. Media Release, 5 February 1 999. Ministry of Agriculture and Fisheries. http ://www.mafgovt.nz Wilkinson, A. G. , 1 999. Poplars and willows for soil erosion control in New Zealand.

CHAPTER 3

2002 GRAZING EXPERIMENT

Effects of willow

(Salix spp.)

(Populus spp.)

supplementation o n the reproductive performance of ewes grazin g low quality drought pasture during m ating

CHAPTER 3 3. 1 Abstract

An 87-day grazing experiment, in the late summer/autumn of 2 002 near M asterton (New Zealand), compared the effects of willow (Salix) versus poplar (populus) supplementation ( 1 . 3 kg fresh/ewe/day), during mating, on reproductive performance and wool production in ewes grazing low quality drought pasture. A rotational grazing system with 285 mixed age Romney ewes ( 5 5 . 2 kg ± 0.54 kg) was used, with 95 ewes per treatment (control, willow supplemented and poplar supplemented). All ewes were offered an allowance of low quality pasture sufficient to provide a potential desired intake of 0. 70 kg dry matter (DM)/d. Pasture offered contained 62% dead matter, with pre- and post-grazing masses of 94 1 kg and 456 kg DMJha. Pasture consumed was typical of drought pasture; 5 7 1 g neutral detergent fibre (NDF)lkg DM, 0. 540 organic matter digestibility (OMO). Both the willow and poplar diets selected were higher in OMD and metabolisable energy (ME) and had a higher ratio of readily fermentable carbohydrate (CHO) to structural CHO, than the pasture diet selected. Willow contained significantly higher concentrations of condensed tannin (CT; 5 2 glkg vs. 1 9 g/kg; P<O. 001 ) and total phenolic glycosides (34 glkg vs. 1 7 g/kg; P<O. 00 1 ) than poplar. The concentration of total phenolic glycosides increased curvilinearly over time with peak values between 5 1 and 6 1 days, corresponding to the mating period. Reproductive rate was low in the control ewes ( 1 3 3 lambs born / 1 00 ewes mated), with willow supplementation reducing live weight loss (-86 g/ day vs. - 1 03 gI day) and

increasing ewe reproductive rate by 1 5%, 1 7%, 21 % and 20% units at ultrasound scanning, lambing, docking and weaning, respectively, through an increase in the proportion of muItiple pregnancies (fecundity). Poplar supplementation had no significant affect on reproductive rate, probably due to contamination with poplar leaf rust (Melampsora larici-populina), which may produce an unknown oestrogenic substance. There were no treatment effects on wool production and only small treatment effects on the LW of single- and twin-born lambs at birth and weaning. Willow tree trimmings are a beneficial supplement for increasing the reproductive rate of ewes grazing drought pasture during the pre-mating and mating periods and they may be superior to poplar tree trimmings, due to higher concentrations of both CT and phenolic glycosides. Willow supplementation increased the intakes of DM and ME, but this did not explain all of the increase in reproductive rate. The increased

CHAPTER 3

concentration of total N, CT, phenolic glycosides and water-soluble CRO in the diet of supplemented ewes would be likely to increase amino acid absorption and this may explain the remainder of the increase in ewe reproductive rate from willow

supplementation.

Keywords: Drought feeding; Poplar (PoplllllS sp.) supplementation; Reproduction; Condensed tannin; Phenolic glycoside; Willow (Salix sp. ) supplementation

3.2 Introduction

In New Zealand, the East Coast regions of Gisbome, Rawke' s Bay, Wairarapa, Marlborough, Canterbury, and North Otago experience intensely hot, dry conditions during the summer and early autumn, with severe droughts occurring every 7- 1 0 years. The loss in livestock productivity on pastoral farms, due to drought, lead to large losses in farm revenue; Ward ( 1 999) estimated that the farm gate cost of the 1 997 and 1 998 droughts totalled $NZ 800 million.

Drought in the summer/autumn severely affects sheep production systems due to low pasture growth and quality, thus limiting the feed available for grazing ewes during the pre-mating and mating periods. Feeding ewes at a level below maintenance results in loss of live weight CL W) and body condition score (BC S) and, during mating, severely reduces ovulation rate and subsequent lambing percentage (Rattray et al. 1 980, 1 98 1 ,

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However, there are no reports on the potential benefits of supplementing ewes with willow tree trimmings and no direct comparisons of the feeding benefits of willow versus poplar supplementation.

The objective of this study was to compare the effects of willow versus poplar

supplementation, during mating, on reproductive performance and wool production in ewes grazing low quality drought pasture.

3.3 M aterials and M ethods

3.3.1 Experimental Design

A grazing trial involving 285 mixed age Romney ewes was conducted at Massey University' s Riverside Farm, near Masterton, New Zealand, on the North I sland East Coast. Willow and poplar supplementation occurred over 87 days from 2 1 J anuary 2002 (late summer) to 1 7 April (autumn) 2002. The experiment involved ewes grazing simulated drought pasture, of low quality and mass/ha, with poplar and willow limbs and leaves offered daily as supplementary feed. The ewes were randomly allocated to 3 groups, each of 95; willow supplementation, poplar supplementation and control. The willow and poplar treatment groups were offered 1 . 3 kg/ewe/day (fresh) of willow or poplar as a supplement to the low quality pasture. The control group was offered no tree trimmings. All ewes were offered a pasture allowance sufficient to provide a potential desired intake of 0.70 kg dry matter (DM)/d. The supplementation period included two 3-week cycles of mating.

3.3.2 Ani mals

On 1 7 January 2002, Romney ewes of similar age, size and LW were randomly assigned to the three treatment groups and individually tagged, scored for body condition (Jefferies 1 96 1 ) and weighed to ensure that the initial average LW of each group was consistent. All ewes were vaccinated with, S alvexin ™ +B (Schering-Plough Animal Health Ltd., Upper Hutt, Wellington, New Zealand), before the experiment to prevent salmonella infection and Ewegaurd™ (Fort Dodge New Zealand Ltd.,

CHAPTER 3