W. J. Parker

Effect of herbage type and level of intake on the release of chromic oxide from intraruminal controlled release capsules in sheep

Abstract Controlled release capsules (CRC) provide for the continuous uniform release of chromic oxide (Cr2O3) into the rumen and so offer an improved means of estimating feed intake in grazing animals. Two experiments were conducted with sheep to measure the effect of herbage type and level of herbage intake on the pattern of Cr2O3 release from CRC. In Experiment 1, differences in CRC plunger travel within and between rumen-fistulated sheep, fed lucerne chaff indoors over 42 days at an allowance equivalent to 1.1 maintenance (M), were not significant. The relationship between plunger travel and time was almost perfectly linear (P < 0.001), but a slight reduction in the rate of plunger displacement became more pronounced while the animals were at grazing between Day 43 and Day 100. Chromium (Cr) release from Day 3 to Day 42 averaged 62 ± 1 (mean ± SE) mg Cr/day. In Experiment 2, rumen-fistulated and intact wethers, housed indoors, were offered ryegrass, white clover, ryegrass-white clover mixed, or meadow...

Early venison production from red deer ( Cervus elaphus ) as affected by grazing perennial or annual ryegrass pastures, pasture surface height and immunization against melatonin

Two grazing experiments in New Zealand, using newly weaned red deer stags, assessed methods of maximizing growth over winter and spring, with the objective of attaining a slaughter weight of 92 kg liveweight (> 50 kg carcass) at the end of spring, by 12 months of age. Perennial ryegrass/white clover pastures, and the same direct-drilled with an annual ryegrass, were grazed at two surface heights (5 cm and 10 cm; Experiment 1; 1988) or at similar pasture mass (Experiment 2; 1989). Balanced groups of stags grazing each forage were immunized against melatonin, commencing at 3 months of age (Expt 1) or at birth (Expt 2). Moata annual ryegrass comprised 19–46% of the feed on offer in Expt 1 and 65–82% in Expt 2. Perennial ryegrass comprised 79–89% of control pastures and white clover generally comprised In Expt 1, rates of body growth during winter were greater for stags grazing at 10 cm than at 5 cm pasture height, with no effect due to the inclusion of annual ryegrass. During spring, growth rates were similar for stags grazing 10 cm pastures and the 5 cm pasture containing annual ryegrass, but were lower on 5 cm pasture based on perennial ryegrass. Inclusion of annual ryegrass slightly increased winter rates of herbage dry matter accumulation, animal carrying capacity and the proportion of stags attaining target slaughter weight. In Expt 2, annual ryegrass pastures were of higher organic matter digestibility than perennial pastures during winter, and supported greater rates of liveweight gain (LWG) and voluntary feed intake (VFI) than the perennial ryegrass. During spring, LWG increased in both groups of stags although the difference between the two groups ceased to be significant. More of the animals grazing annual ryegrass pastures attained target slaughter weight than those grazing perennial pasture. Rumen acetate: propionate ratio, measured in fistulated stags, was similar for both groups of animals. Relative to perennial ryegrass, pastures containing high proportions of annual ryegrass resulted in similar animal carrying capacity during winter but substantially lower carrying capacity in spring. Antibodies binding melatonin were detected in 75% of immunized animals, with higher and more persistent titres being obtained using Freunds than using Dextran adjuvant and titre being much higher in stags immunized at birth than at 3 months of age. This was associated with a small and variable increase in plasma prolactin concentration, but had no effect upon plasma concentrations of LH or testosterone or upon LWG. It was concluded that the small increase in deer production attributable to annual ryegrass was mainly due to higher VFI, and that grazing perennial ryegrass/white clover pastures at 10 cm surface height resulted in higher levels of deer production than grazing at 5 cm surface height. These studies emphasise the feasibility of early venison production from grazed pastures in New Zealand, and show that the young deer were growing close to their genetic potential under this system.

Effects of pre‐lamb shearing on feed intake and associated productivity of May‐ and August‐lambing ewes

Abstract The effects of pre‐lamb shearing on feed intake and wool/lamb production of May (autumn)‐ and August (spring)‐lambing ewes were examined. Mixed age Border Leicester x Romney ewes mated to lamb in May or August (60 ewes/ lambing policy) were divided at random into two groups (balanced for pregnancy status and liveweight). One group was shorn on Day 118 of pregnancy (P118) and the second group left unshorn. Measurement of pasture intake was carried out over three periods before lambing (P113–117, P119–130, and P141–144) and three periods after lambing (L (lactation day) 8–11, L21–25, and L29–33) using intraruminal chromic oxide controlled release capsules. Intake of ewes was not affected by shearing treatment during pregnancy or lactation except during P141–144 when organic matter intake was significantly greater for shorn ewes than for unshorn ewes (1739 ±58 versus 1526 ± 59 g/day, P < 0.05). Ewe liveweights and condition scores were similar for both shearing treatments during pregnancy and lactat...

Pasture management to minimise the detrimental effects of pre‐lamb shearing

Abstract The purpose of this study was to examine whether the performance of pre‐lamb shorn sheep is influenced by pasture allowance in the immediate post‐shearing period and whether the relationship between performance and pasture allowance differs according to whether the ewes are shorn by standard comb or cover comb. The trial was replicated across two years to allow for climatic variations between years. Fifty‐four ewes were used in each year in a 3 × 3 × 2 factorial design with three shearing treatments (standard comb, cover comb, and unshorn), three sward surface height (SSH) treatments (nominal 3, 5, and 7 cm), and two pregnancy status treatments (single and twin). Rectal temperatures of standard comb or cover comb ewes were significantly lower (P < 0.05) than those of unshorn ewes on day 2 following shearing (S2), and on S4, S8, and S20. Pasture allowance, however, did not affect rectal temperatures of shorn ewes. There was an interaction (P < 0.05) between shearing treatment and SSH. Thus, livewe...

Resistance to cold stress in sheep shorn by cover comb or standard comb

The cover comb has been developed in New Zealand as a means of increasing residual fleece depth after shearing and so increasing the resistance of shorn sheep to cold stress. The effects of shearing by cover comb and standard comb were studied over 2 days pre-shearing and 10 days post-shearing in eight pairs of non-pregnant, non-lactating 2-year-old ewes. Animals were housed and given a maintenance level of chaffed lucerne hay. One member of each pair was shorn with a cover comb, the other with a standard comb. Each pair was exposed to ‘cold plus wind’ (7°C ambient temperature, 7 km/h air movement) followed by ‘cold plus wind plus rain’ (10°C ambient temperature, 7km/h air movement, wetting at a rate equivalent to 25 mm/h rain from overhead sprinklers) in a calorimetry chamber on days S –3, S –2, SO (day of shearing), S2, S6 and S10. Heat production immediately after shearing (SO) was proportionately 0·22 greater in ewes shorn by the standard comb under conditions of ‘cold plus wind’ and 0·38 greater under conditions of ‘cold plus wind plus rain’ than in their cover comb-shorn cohorts. Circulating concentrations of non-esterifiedfatty acids were substantially elevated on the day of shearing and 2 days thereafter in ewes shorn by the standard comb, indicating increased rates of body fat mobilization to support heat production in these ewes compared with those shorn by the cover comb. This was reflected in a 1·4 kg weight loss in the standard comb-shorn ewes compared with a 0·4 kg live-weight gain in the cover comb-shorn group over the 10 days of the experiment. It was concluded that use of a cover comb will significantly reduce the risk of death from hypothermia in sheep shorn during winter and spring, and should facilitate an increase in the productivity of animals by allowing a greater proportion of food energy to be used for productive purposes.

Evaluation of Border Leicester × Romney (BR), Poll Dorset × BR, and Suffolk × BR ewes for out-of-season lambing

Abstract Three different year groups of Border Leicester × Romney (BR), Poll Dorset × BR (PBR), and Suffolk × BR (SBR) ewes were evaluated for yearling liveweight and greasy fleece weight, and for their 2– and 3–year-old lambing performance under both June– and August-lambing policies. Mating of the June-lambing ewes was induced using progesterone treatment and high ram:ewe ratios. Suffolk × BR hoggets were significantly (P < 0.01) heavier than PBR and BR ewe hoggets in May, October, and January (at about 16 months of age). Border Leicester × Romney hoggets produced significantly (P < 0.01) more greasy wool at the yearling shearing than PBR or SBR hoggets. Lambing policy did not influence the proportion of ewes lambing but there were more (P < 0.05) multiple births in August-lambing ewes. Birth weights and weaning weights of June-born lambs were lower (P < 0.001) than those of their August-born counterparts. Weight of lamb weaned per ewe joined was 22.1 kg for June-lambing ewes and 24.3 kg for August-lamb...

Wool production and feed intake in unmated and mated Border Leicester × Romney crossbred ewes shorn in July or November

Abstract Information about the relative feed intake and productivity of unmated and mated ewes, of subsequent different pregnancy and rearing status, is required to design management systems for all-wool and breeding sheep policies. Liveweight change, midside and total wool growth, and lamb performance were measured from mid pregnancy until just before the following mating on 90 ewes. Thirty unmated ewes were studied over the same period. Half of the ewes were shorn in July and the remainder in November. Intakes of unmated, single-, and twin-bearing ewes (n = 12/status group balanced for shearing policy and age), under ad libitum pasture conditions, were not significantly different during late pregnancy, but lactating ewes consumed more pasture than unmated ewes during Weeks 5 (P < 0.05), 8 (P < 0.001), and 10 (P < 0.001) after parturition. Pre-lamb shorn ewes had higher herbage intake during Week 5 (2.56 versus 2.20 kg OM/day; P < 0.05) and Week 10 (2.63 versus 2.42 kg OM/day; P < 0.1) of lactation. Wool...

Effect of sward surface height on herbage intake and performance of lactating ewes lambed in winter and continuously stocked on pasture

Thirty-six 4-year-old Border Leicester × Romney (BR), Poll Dorset × BR (PBR) and Suffolk × BR (SBR) ewes balanced for litter size were assigned, 6 days after the mid-point of lambing (29 June 1989), to one of three sward surface height (SSH) treatments replicated twice (six ewes/1 ha paddock). The mean SSH during the 54 days of the trial were 2·6, 4·4 and 7·8 cm. Herbage organic matter intake (OMI) was measured using intraruminal chromium controlled release capsules during weeks 3, 4, 7 and 8 of lactation. Ewe OMI was not influenced by SSH during week 3 of lactation. During weeks 4 and 7 of lactation, ewe OMI increased with SSH up to a SSH of 7·8 cm. In week 8 of lactation there was no significant difference in OMI between ewes grazing the 4·4 or 7·8 cm SSH treatments, suggesting maximum intake at this stage of lactation is reached at 4·4 cm SSH. A maximum OMI of 2·6±0·1 and 3·0±0·1 kg OM/ewe per day ( P P

Herbage intake, ingestive behaviour, and growth performance in unbred and once-bred Hereford × Friesian heifers

Abstract The once-bred heifer beef production system involves mating heifers at 15 months of age to calve as 2-year-olds. This study compared the performance of once-bred Hereford × Friesian heifers mated to Limousin or Charolais sires and the herbage intake of once-bred and never-bred heifers during periods corresponding to late pregnancy and early lactation in the former group. Heifers carrying Limousin-sired (LS) calves had gestation lengths slightly longer than those carrying Charolais-sired (CS) calves (290.4 versus 286.6, pooled SE (PSE) = 1.2 days, P < 0.10), but there was no effect of calf sex on gestation length. The average birth weight of calves was 40 ± 1 kg, there being no difference between female and male, or LS and CS, calves. Dystocia caused mortality rates of 19% in calves and 9% in heifer dams. Female calves had 9 kg lower weaning weights at 142 days of age than male calves, whereas the CS calves had greater weaning weights than LS calves (218.3 versus 204.9 kg, PSE = 3.6 kg, P < 0.01)....

Effects of iodine supplementation on the productivity of Romney ewes in the Wairarapa region of New Zealand

Abstract The objective of this study was to examine the effects of iodine supplementation of ewes on their plasma thyroid hormone concentrations and production of ewes and their lambs. The study was conducted in the Wairarapa, a region where apparent subclinical iodine eficiency has been reported. Two groups of 200 Romney ewes, one of which was injected with iodised oil (Lipiodol}®) 3 weeks before mating, were monitored for 1 year from mating. Thyroxine concentrations were significantly (P < 0.0 1) elevated in the iodine-supplemented ewes 113 days after treatment. Supplemented ewes were heavier at mating (P < 0.05) but did not differ significantly from controls in lambing performance, lamb growth rate, or ewe fleece production. Lipiodol® was shown to be an effective means of supplementing ewes with iodine, but untreated ewes apparently obtained adequate levels of iodine from plant and soil material ingested. High soil intakes associated with intensive winter rotational grazing are likely to have been resp...