Animal Science, Volume 62 - Issue 3 - June 1996
- This volume was published under a former title. See this journal's title history.
Research Article
Farm animal cognition
- C. J. Nicol
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- 02 September 2010, pp. 375-391
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Although there may be task-specific differences in performance between wild and domestic animals, there is no evidence for any generally reduced cognitive capacity in domestic animals. It is not possible to compare intelligence between species or breeds without recognizing the contribution of differences in attention and motivation, and domestic animals often perform better on learning tasks than wild animals because they are less fearful. Considerable flexibility and complexity in behaviour can arise from context-specific decisions that may not require learning. Examples include alarm calling and maternal behaviour in chickens. However, the majority of intelligent behaviour shown by farm animals is dominated by learned associations, sometimes in response to remarkably subtle cues. Seemingly straightforward learning abilities may result in surprising emergent properties. An understanding of these properties may enable us to investigate how farm animals interact socially, and whether they form concepts. Other abilities, such as imitation and the re-organization of spatial information, do not appear to depend on associative learning. The study offarm animal cognition tells us little about the issue of animal consciousness but, none the less, plays an important role in the animal welfare debate. The types of cognitive abilities animals have provide clues as to the types of situations in which (given the benefit of the doubt) they might suffer.
Customized selection indices for dairy bulls in Australia
- P. J. Bowman, P. M. Visscher, M. E. Goddard
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- 02 September 2010, pp. 393-403
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Customized sire selection indices were developed for Australian dairy bulls in order to promote more objective use of estimated breeding values in commercial breeding programmes. It was assumed that the breeding goal for commercial dairy farmers is the profitability of a bull's progeny. Seven characteristics of the progeny were identified as having a major impact on profitability and were included in the breeding objective: milk, fat and protein yield, survival, body weight, milking speed and temperament. Traits in the selection indices used to predict profit were milk, fat and protein yield, survival, milking speed, temperament, size, overall type and fore teat placement. Size was included because of its correlation with body weight, and overall type and front teat placement because of their correlation with survival. To avoid double counting the benefits of milk production traits, temperament and milking speed, the survival trait in the objective was defined as survival independent of voluntary culling for these traits. Customization of the breeding objective was achieved by adjusting the economic weights for traits in the objective to take account of important characteristics of farmers' herds, the milk payment system under which they operate and make allowance for their own value judgements. An assessment of the impact of customization suggested that, even though there is a wide range in the economic weights that are applicable in different areas of Australia, there would be little loss of efficiency in using a single national index. However, customization is still believed to be desirable given that it is likely that a substantial proportion offarmers will be reluctant to use a national index, especially in those states which have quotas and focus on the liquid milk market. The algorithms described in the paper have been incorporated into a user-friendly microcomputer program called $electabull which is now commercially available to farmers.
The effects of wilting of grass prior to ensiling on the response to bacterial inoculation. 1. Silage fermentation and nutrient utilization over three harvests
- T. Yan, D. C. Patterson, F. J. Gordon, M. G. Porter
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- 02 September 2010, pp. 405-417
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Four silages were prepared from perennial ryegrass swards at each of first (primary growth), second (first regrowth) and third (second regrowth) harvests during the 1993 growing season. At each harvest the four silages included two unwilted (without and with inoculant at 2·4 l/t) and two wilted (without and with inoculant at 24 l/t). The four silages within a single harvest, were offered as the total diet at maintenance levels to 12 wether sheep for 3 weeks to determine nutrient apparent digestibilities. They were also given to 12 lactating dairy coivs together with a concentrate supplement, in a three-period change-over study with experimental periods of 8-weeks duration, to examine dry matter (DM) apparent digestibility and utilization of nitrogen (N) and energy in the diets.
Inoculation tended to improve silage fermentation with on average lower pH and ammonia-N/total-N across the three harvests, while wilting of grass prior to ensiling significantly increased silage pH fP < 0·001) and ammonia-N/total-N (P < 0·001). Neither inoculation nor wilting had any significant effect on mean nutrient apparent digestibilities, assessed through sheep, across the three harvests. However, at the second harvest inoculation significantly reduced apparent digestibilities of DM (P < 0·001) and N (P < 0·001). At this harvest, wilting also significantly decreased apparent digestibilities of DM (P<0·05) and N (P <0·01), but significantly increased apparent digestibilities of DM (P < 0·05), energy (P < 0·001) and N (F < 0·05) at the third harvest. When the silages were offered as mixed diets to dairy cattle, neither inoculation nor wilting had significant effects on digestibilities of DM, N and energy at any of the three harvests, except for wilting which significantly decreased DM apparent digestibilities (P < 0·05) at the second harvest. However, the mean apparent digestibilities of DM (P < 0·01), N (P < 0·05) and energy (P < 0·01) across the three harvests were significantly lower following wilting, and N apparent digestibility (P < 0·05) was significantly higher following inoculation. The calorimetric data indicated that inoculaton had no significant effects on either methane energy output or heat production. Wilting also had no significant effect on methane energy output, but significantly increased daily heat production (P<0·05) at the first harvest. The efficiencies of metabolizable energy utilization for lactation (k1) were similar between the four silages at each of the first and second harvests, with the average being 0·50. The results of the present study indicated that inoculation tended to improve silage fermentation and significantly increased mean N apparent digestibility of mixed diets across the three harvests, while wilting significantly reduced mean DM, N and energy apparent digestibilities of mixed diets. Neither inoculation nor wilting had significant effects on Rvalue.
The effects of wilting of grass prior to ensiling on the response to bacterial inoculation. 2. Intake and performance by dairy cattle over three harvests
- D. C. Patterson, T. Yan, F. J. Gordon
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- 02 September 2010, pp. 419-429
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Four silages (unwilted with and without inoculant, and wilted with and without inoculant) were prepared from perennial ryegrass swards at each of three harvests over the growing season. The four silages from each of the first (primary growth), second (first regrowth) and third (second regrowth) harvests were offered ad libitum to 48 dairy cows during periods 2, 1 and 3 respectively, in a two (control and additive) × two (unwilted and wilted) × three (harvest (period)) change-over design experiment with 8-week experimental periods. The animals also received a concentrate supplement at 7·0, 6·1 and 5·2 kg dry matter (DM) per day in the first, second and third periods respectively. The supplement was based on barley, molasses and soya-bean meal.
There were significant interactions between inoculation and wilting across the three harvests on silage DM intake (F<0-01), milk yield (P<0·05), and outputs of fat (P<0·01) and protein (P<0·05). Inoculation had no significant effects on silage intake and milk production across the unwilted and wilted silages. However, within the unwilted silages, inoculation significantly increased silage DM intake by 0·46 kg/day (P < 0·05) and fat yield by 0·032 kg/day (P<0·05). In contrast, within the wilted silages inoculation significantly reduced fat yield by 0·030 kg/day (P < 0·05). Wilting of grass prior to ensiling significantly increased silage DM intake by 0·73 kg/day (P <0·001), milk yield by 0·42 kg/day (P<0·05), fat yield by 0·053 kg/day (P < 0·001) and protein yield by 0·047 kg/day (P < 0·001) across the inoculant-treated and untreated silages. The effects however were mainly derived from the untreated silages as within the inoculant-treated materials the differences in silage intake and milk yield were not significant between unwilted and wilted treatments. The results of the current experiment indicate that wilting with no additive significantly improved silage intake and milk production, but otherwise the improvement was reduced with wilting following inoculation. Inoculation significantly increased silage intake and fat yield when used with the unwilted grass, but it significantly reduced fat yield when used with the wilted grass.
Systems of mating to reduce inbreeding in selected populations
- A. Caballero, E. Santiago, M. A. Toro
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- 02 September 2010, pp. 431-442
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Stochastic simulation is used to compare different systems of mating to reduce rates of inbreeding in selection programmes with phenotypic or animal model best linear unbiased prediction (BLUP) evaluation. Compensatory mating (the mating between individuals from the largest selected families to individuals from the smallest) turns out to be proportionately about 0-30 more effective than minimum coancestry matings for situations with low rates of inbreeding, such as phenotypic selection or high population size, although the advantage is less apparent if common environmental effects are important. A modification of this system of mating is proposed which can be applied for overlapping generations, and this is shown to reduce rates of inbreeding proportionately by about 0-50 more than for discrete generations. Under high inbreeding, however, such as for BLUP selection and small population size, minimum coancestry matings, or even avoidance of sib matings are more effective. A procedure combining compensatory and minimum coancestry matings is also simulated and gives the largest reductions in the rate of inbreeding. The effects of these and other systems of mating on the rate of inbreeding are shown to occur through a reduction in the cumulative effect of selection and a deviation from Hardy-Weinberg proportions.
Effect of bovine follicular fluid treatment and progesterone priming on luteal function in GnRH-treated seasonally anoestrous ewes
- G. F. Basiouni, M. Khalid, W. Haresign
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- 02 September 2010, pp. 443-450
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The main objective of the present experiment was to investigate whether progesterone priming eliminates defective luteal function in seasonally anoestrous ewes induced to ovulate with pulsatile GnRH treatment by synchronizing the early stages of follicle development. This was achieved by suppressing and synchronizing the early stages of follicle development with bovine follicular fluid (bFF) and then investigating whether this was sufficient to eliminate defective luteal function following the induction of ovulation with GnRH. Ewes in group 1 (no. = 10) were injected s.c. with 2 ml bFF at 8-h intervals for a period of 3 days before the start of GnRH treatment. Animals in group 2 (no. = 10), ivhich served as positive controls, were given a single i.m. injection of 20 mg progesterone 3 days before the start of GnRH treatment, while those in group 3 (no. = 10), which served as negative controls, were injected with corn oil alone at this time. Ewes in all the three groups were induced to ovulate by administration of 2-hourly injections of GnRH (250 ng per injection) for 54 h. Frequent blood samples for LH, FSH, and oestradiol were collected around the time of both progesterone/bFF injections and GnRH treatment, as well as daily thereafter to monitor luteal function.
The bFF injections given to animals in group 1 resulted in a significant (P<0·001) suppression of FSH concentrations, followed by a rebound rise in concentrations after the cessation of treatment. GnRH treatment significantly (P < 0·05) increased both mean LH pulse amplitude and overall mean LH concentrations in all the three groups, while LH pulse frequency was increased only in non-bFF-treated ewes. Plasma oestradiol concentrations 24 h after the start of GnRH treatment were significantly (P < 0·05) higher in groups 2 and 3 compared with group 1. These differences in the patterns of oestradiol concentrations over time were associated with a significant (P <0·05) delay in the onset of the pre-ovulatory LH surge in ewes treated witli bFF (group 1). However, there was no difference in either the duration or the height of pre-ovulatory LH surge between the three treatment groups. Ewes in all three treatment groups ovulated in response to GnRH treatment. However, both laparoscopic examination and plasma progesterone concentrations revealed that the incidence of normal luteal function was significantly (P < 0·05) higher in group 2 (10/10) compared with groups 1 (2/10) and 3 (4/10), with no difference between groups 1 and 3. Overall, these results suggest that progesterone priming does not eliminate defective luteal function through synchronizing early stages offollicle development.
Selection of Merino sheep for resistance to Haemonchus contortus: genetic variation
- R. R. Woolaston, L. R. Piper
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- 02 September 2010, pp. 451-460
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An animal model was used to estimate heritabilities of faecal egg count (FEC) and packed cell volume decline (PCVD) in lines of Merinos selected for divergent levels of resistance to Haemonchus contortus. The estimated heritability of FEC was 0·23 (s.e. 0·03) and of PCVD was 0·21 (s.e. 0·03). A cube root transformation was found to be effective in normalizing FEC data and reducing the range of within selection line-birth year variances from 118-fold to 10-fold. Transforming FEC data increased the heritability estimate to 0·29 (s.e. 0·03) and reduced selection bias due to heterogeneity of variance, but the further step of pre-adjusting the transformed data to a common variance had only a trivial effect. Heritability estimates for FEC in years with high means and variances were similar, as were estimates for transformed FEC. The estimated genetic correlations between measurements in years with high and low means and variabilities were 0·77 to 0·91.
PCVD and pre-adjusted transformed FEC had a phenotypic correlation of 0·48. Estimates for the genetic correlation ranged from 0·76 in the decreased resistance line to 1·00 in the increased resistance line and 0·87 with pooled data. Other effects on resistance included birth type and dam age, with twins and progeny of maiden dams being more resistant than their cohorts. Sex effects were unimportant for FEC but males had higher PCVD than females in most, but not all, years. Younger animals had higher FEC and PCVD than older animals. Maternal genetic effects were found to be unimportant, as were the effects of low levels of inbreeding.
Effect of space allowance during transport on the behavioural and physiological responses of lambs during and after transport
- M. S. Cockram, J. E. Kent, P. J. Goddard, N. K. Waran, I. M. McGilp, R. E. Jackson, G. M. Muwanga, S. Prytherch
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- 02 September 2010, pp. 461-477
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There is limited information on the behavioural and physiological responses of sheep to the components of road transport. Behavioural observations and physiological measurements of ‘stress’, injury and dehydration were made on weaned lambs (35 kg) before, during and after either stationary confinement or transport for 22 h at four space allowances (0·22, 0·27, 0·31 and 0·41 m2 per sheep). Two groups were not loaded (a control group with access to food and water, and a group with no food and no water for 12 h). During the confinement and transport period, the proportion of scans spent lying and the proportion of scans spent ruminating was significantly less than that before treatment (P < 0·01). After 3 h of transport, the proportion of scans spent lying was significantly less at the 0·22 m2 per sheep space allowance than at the other space allowances. The proportion of scans spent lying down was only significantly greater during confinement compared with transport at the 0·22 m2 per sheep space allowance and during the first 6 h at the 0·31 m2 per sheep space allowance. During transport, the heart rate and plasma cortisol concentration were greater than during stationary confinement (P < 0·05), indicating that some aspect of the journey was acting as a stressor. During transport the frequency of losses of balance and the frequency of slips was less at the 0·22 m2 per sheep space allowance than at the 0·27 and 0·41 m2 per sheep space allowances. However, there was no effect of space allowance on either plasma cortisol concentration or biochemical measures of injury. The median frequency of potentially traumatic events during transport was <5 per h and there was little evidence to suggest that increasing space allowance increased the risk of traumatic injury. During the first 12 h after treatment, the proportion of scans spent eating was greater and the proportion of scans spent lying were less than those spent before treatment (P < 0·001). Post-treatment, water intake and packed cell volume were greater in transported sheep than in control sheep (P < 0·05). However, there was no significant effect of 12 h without water on total plasma protein concentration and plasma vasopressin concentration (P > 0·05). Under the conditions of this study, sheep with a live weight of 35 kg can be transported for 12 h at space allowances of between 0·22 and 0·41 m2 per sheep without showing major physiological changes indicative of injury and dehydration. However, the sheep appeared to be hungry after 12 h without food and showed a cortisol and heart rate response to transport, indicating that some aspect of transport was acting as a stressor. A space allowance of 0·22 m2 per sheep cannot be recommended for 35 kg sheep as there is insufficient space for most of the sheep to lie down during transport. Whereas a space allowance of at least 0·27 m2 per sheep does allow most sheep sufficient space to lie down.
Growth, fertility, prolificacy and fleece weight of Romanov, Finnsheep and Booroola purebreds and their first cross and backcross with the DLS breed
- M. H. Fahmy
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- 02 September 2010, pp. 479-487
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Records ivere collected on Romanov (R), Finnsheep (F), and Booroola Merino (B); first cross; and backcrosses of these breeds with a new synthetic breed of Dorset, Leicester and Suffolk (DLS). The data covered the period from the birth of ewes to weaning of their progeny. The heaviest lambs at birth were the B backcross and R first and backcrosses (4·1 to 4·0 kg) and the lightest were pure R (3·0 kg). The fastest pre-weaning average daily gain was that ofR crosses. R purebreds were more fertile (109%, P < 0·01) than F (81%) and B (62%). They were also more prolific at birth and at weaning (2·44, 2·13) than F (2·04, 1·71, P < 0·01) and B (2·36, 2·09, P > 0·05) purebreds, respectively. Similarly, first-cross R ewes were more prolific than first-crosses of F and B (1·99 v. 2·86 and 1·70), also backcross R ewes were more prolific than backcrosses ofF and B (1·63 v. 1·45 and 1·42, P > 0·05), respectively. R first-cross ewes had heavier litters (6·31 and 26·1 kg) than B (5·17 and 20·3 kg, P>0·01) and F (5·52 and 24·4 kg) at birth and at day 50. The lambs born to DLS ewes were the heaviest at birth and at day 50 compared with those from prolific ewes. Fleece weight in B and its crosses was significantly higher than in R. Crosses showed generally positive heterotic effect in weights, prolificacy and wool production compared with pure breeds. In two data sets, additive direct effect ofR was higher than that ofF at birth (by 0·11 and 0·10 kg) and at day 50 (by 0·57 and 0 kg) but was similar at day 100 and day 365. The additive direct effect of both R and F was non-significantly different to that of B at birth in both data sets, but in only one data set was it higher (P < 0·001) at day 50 (by 2·29 and 1·72 kg), at day 100 (by 5·24 and 5·30 kg) and at day 365 (by 8·7 and 8·4 kg, respectively). Maternal direct effects ofR was higher (P < 0·05) than F in lamb weights at day 1 and 50, and higher than B in lamb weight at day 50. Individual heterosis between both R and F and DLS were -3·7 and -3·6% in weight at birth, 1·46 and 2·09% in weight at day 50 respectively. The corresponding maternal heterosis were, -2·9, -5·2, 1·46 and -0·02%.
Variation in ovulation rate and litter size of Cambridge sheep
- I. Ap Dewi, J. B. Owen, A. El-Sheikh, R. F. E. Axford, M. Beigi-Nassiri
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- 02 September 2010, pp. 489-495
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Ovulation rate (OR) and litter size (LS) were recorded in a flock of Cambridge sheep from 1984 to 1994 and from 1976 to 1994 respectively. There were 1516 and 2480 OR and LS records with means of 3·2 and 2·5 respectively. There was considerable variation in results between years ranging from 2·2 to 3·2 for LS and from 2·8 to 4·2 for OR. Ewe lamb OR was affected by year of recording, some years having higher OR than others. Rearing type (single, twin or triplet) also affected ewe lamb OR, twins having lower OR than both singles and triplets. Ewe lamb OR decreased with later date of birth reflecting a lower age at OR counting. Ewe lamb LS was affected by year of recording and there was also an interaction between date of birth and year indicating that OR decreased with later date of birth in some years but not in others. OR of adult ewes was affected by year of recording which also interacted with age (2, 3 and 4). Generally, OR increased with age but this trend was not observed in all years. LS of adult ewes was significantly affected by year and increased with ewe age (2, 3 and 4). Heritability and repeatability were determined for ewe lamb OR and LS and adult ewe OR and LS in univariate and two-trait analyses using DFREML. Heritabilities of ewe lamb OR (0·18 to 0·21) and LS (0·05 to 0·08) were lower than corresponding adult ewe values for OR (0·19 to 0·34) and LS (0·19 to 0·22). Ewe OR had a lower repeatability (0·43 to 0·55) than LS (0·30 to 0·80). High genetic correlations (>0·9) were obtained for combinations of ewe lamb OR, ewe lamb LS, adult ewe OR and adult ewe LS. The importance of analysing ewe lamb and ewe records separately is discussed as is the value of ewe lamb OR as a selection criterion.
Responses in wool and live weight when different sources of dietary protein are given to pregnant and lactating ewes
- D. G. Masters, C. A. Stewart, G. Mata, N. R. Adams
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- 02 September 2010, pp. 497-506
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Wool growth, staple strength and fibre diameter are reduced during pregnancy and lactation. This may be due to the increased requirement for protein for foetal growth, udder development and milk production causing a lack of amino acids for wool. Responses in wool production, ewe live weight, lamb birth weight and growth, plasma amino acids and levels of cortisol, insulin and growth hormone were measured when different sources of protein were offered. Either lupin seed (L), fish meal (F) or formaldehyde-treated egg white (E) were included in an oaten hay-based diet offered during the final 3 weeks of pregnancy and first 3 weeks of lactation. Provision of diets containing E or F resulted in significant (P < 0·001) increases in wool growth and trends towards increased staple strength (4 to 6 N/ktex) and clean fleece weights (0·17 to 0·38 kg) compared with the sheep given L. Feeding the E diet increased the concentration of cystine in plasma and sulphur in wool in late pregnancy. Feeding the F diet increased the concentrations of arginine, histidine, lysine and threonine in plasma in early lactation. Ewes given E had higher circulating insulin and increased insulin resistance, compared with sheep given L, on 2 of the 4 days of sampling during pregnancy and lactation during the treatment period. There were no treatment effects on lamb birth weight or growth but ewes given the E diet were significantly (P < 0·05, 3·3 kg) heavier than the ewes given L after 3 weeks of lactation. The results indicate that a lack of protein available for absorption in the small intestine causes reduced wool growth during late pregnancy and early lactation. Wool growth is more sensitive to a reduced protein supply than foetal growth, maternal weight or milk production.
Breeding season and ovulation rate in ewes treated with long days in spring followed by a melatonin implant and exposure to a ram
- T. Sweeney, D. O'Callaghan
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- 02 September 2010, pp. 507-512
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While the onset of the breeding season in ewes can be advanced up to 7 weeks following exposure to long days (44 days) before lambing, a melatonin implant from lambing and exposure to a ram from the summer solstice, this advance is reduced by the absence of a ram. The aim of this experiment was to determine if earlier exposure to the ram and/or exposure to more long days before lambing would further advance the onset of the breeding season. A further aim was to compare the ovulation rate and duration of the breeding season between ewes with a normal and advanced onset of the breeding season due to this treatment regime. Pregnant ewes lambing in mid March were allocated to treatments as follows: (1) controls, maintained on natural photoperiod; (2) 44 LD + mel, exposed to 44 long days (18L: 6D; LD) before lambing followed by a 700-mg melatonin implant after lambing; (3) 90 LD + mel, as in treatment 2, but exposed to 90 LD before lambing; (4) 90 LD + mel + ram, as in treatment 3, including continuous exposure to a vasectomized ram from 10 April. Reproductive state was assessed from serum progesterone concentrations in blood collected at 3- to 4-day intervals from 10 April and ovulation rate was determined during the luteal phase of the first five oestrous cycles in control ewes and ewes exposed to 90 LD + mel + ram. Ewes exposed to 90 LD + mel + ram commenced the breeding season 10 weeks earlier (median date 25 July, range 28 days; P < 0·001) than controls (median date 8 October, range 68 days). Overall, the onset of the breeding season was not advanced in ewes given 44 or 90 LD + mel in the absence of a ram, but a biphasic response was evident, with 40 to 50% of ewes beginning the breeding season at the same time as ewes on 90 LD + mel + ram. Ovulation rate was similar between control ewes and ewes exposed to 90 LD + mel + ram (P > 0·05). The duration of the breeding season was longer in ewes exposed to 90 LD + mel + ram (210 (s.e. 15) days; P < 0·002) than in control ewes (158 (s.e. 10) days), with no difference in date of the end of the breeding season (P > 0·05). Exposure of ewes to 90 LD before lambing in March, followed by a melatonin implant and exposure to the ram from 10 April advanced the onset and extended the duration of the breeding season without an overall effect on ovulation rate. The ram is an important component of this signal sequence.
Effects of methylthiouracil treatment on the growth and moult of cashmere fibre in goats
- S. M. Rhind, S. R. McMillen
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- 02 September 2010, pp. 513-520
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The effect of long-term treatment of goats with methylthiouracil on the timing, amount and quality of secondary fibre (cashmere) growth and timing of cashmere moult in goats was investigated. From early June, groups of 10 Icelandic × Scottish feral goats were dosed orally each day, for a 15-month period, with 5 mg methylthiouracil per kg live weight in 30 ml water (treated; T) or with water only (control; C). Treatment with methylthiouracil resulted in a significant reduction (P < 0·05) in the proportion of active secondary hair follicles present during March. This was associated with a delayed onset of moult of cashmere in T compared with C goats at both the head (11 March v. 23 February; s.e. 3·33 days; P< 0·05) and mid side (27 March v. 26 February; s.e. 3·58 days; P < 0·001). There was no effect on the time of onset (C, 19 July; T, 19 July; s.e. 5·84 days) or cessation of cashmere fibre growth (C, 9 December; T, 8 December; s.e. 1·69 days) or the mean growth rate (C, 0·473 mm/day; T, 0·451 mm/day; s.e. 0·025) and fibre diameter (C, 16·9 μm; T, 15·4 jim; s.e. 0·266). Wlien present in the fleece, the mean weight and proportion of cashmere was higher in C than in T goats (P < 0·05). It is concluded that methylthiouracil treatment altered secondary follicle activity and the time of onset of the moult of cashmere and that these changes may be a result of reduced triiodothyronine production from thyroxine and associated secondary changes in profiles of insulin and IGF-1.
The influence of terminal sire genotype, sex, slaughter weight, feeding regime and slaughter-house on growth performance and carcass and meat quality in pigs and on the organoleptic properties of fresh pork
- M. Ellis, A. J. Webb, P. J. Avery, I. Brown
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- 02 September 2010, pp. 521-530
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A total of 897 pigs were used in a study to investigate the relative effects of terminal sire genotype (lines Av.Bv. C), sex (castrate v. gilt), slaughter weight (80 v. 100 v. 220 kg), feeding regimen (ad libitum v. restricted, 0·82 ad libitum intake) and slaughter-house (HI v. H2 v. H3) on growth performance, carcass and meat quality characteristics and the eating quality offresh pig meat. Sire line A was a pure Duroc population, and B and C were European-type experimental lines where C contained Pietrain and B did not. In total, 26 sires from line A, 42 sires from line B, and 21 sires from line C were mated to females from the same crossbred dam line and progeny were reared under standard conditions to slaughter. Following slaughter and carcass evaluation, samples of longissimus dorsi were investigated for a range of meat quality and organoleptic characteristics. Line A produced fatter carcasses (C fat depths = 15·6 v. 24·0 v. 14·0 mm for lines A, B, and C, respectively, average s.e. 0·39) with higher killing-out proportions (g/kg) (790 v. 779 v. 786 respectively, average s.e. 1·4) and higher visible marbling, less tissue separation, firmer backfat, and juicier (3·81 v. 3·67 v. 3·72 respectively, average s.e. 0·044: on a scale 1 (extremely dry) to 8 (extremely juicy)) and more acceptable meat (4·54 v. 4·37 v. 4·42 respectively average s.e. 0·037: on a scale 1 (dislike extremely) to 8 (like extremely)) with a lower shear force (5·35 v. 5·78 v. 5·67 kg respectively, average s.e. 0·078) than lines B and C which were similar in most respects. Increases in slaughter weight were associated with a reduction in growth rate (785 v. 769 v. 725 glday for 80, 100 and 120 kg slaughter weight respectively, average s.e. 8·5), increases in backfat (Cfat = 13·3 v. 24·2 v. 26·3 mm respectively, average s.e. 0·34) and longissimus muscle area (34·6 v. 40·7 v. 44·6 cm2 respectively, average s.e. 0·59) and a deterioration in tenderness (4·72 v. 4·40 v. 3·95 respectively, average s.e. 0·062: on a scale 1 (extremely tough) to 8 (extremely tender) and overall acceptability (4·65 v. 4·44 v. 4·25 respectively, average s.e. 0·045) and an increase in shear force (5·37 v. 5·58 v. 5·87 kg respectively, average s.e. 0·085). Slaughter-house had a significant impact on pork odour scores but not on other organoleptic properties. Pigs reared under ad libitum feeding grew faster (840 v. 678 g/day respectively, average s.e. 3·7), were fatter (Cfat = 15·8 v. 23·2 mm respectively, s.e. 0·28), had lower carcass yields (780 v. 790 g/kg respectively, average s.e. 1) and produced more tender, juicier meat than those reared under restricted feeding. Differences between castrated males and gilts in growth and carcass trait were in line with other studies and there were no significant differences between the sexes for eating quality. There were relatively few significant interactions (P < 0·05) for eating quality traits and most of these involved slaughter-house and were for pork odour intensity, which are of limited practical significance. This suggests that the effects of sire genotype, slaughter weight and feeding regimen on eating quality identified in this study are likely to be additive.
Genetic and phenotypic relationships between performance test and reproduction traits in Large White pigs
- J. C. Kerr, N. D. Cameron
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- 02 September 2010, pp. 531-540
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Genetic and phenotypic relationships between performance test and reproduction traits were estimated, after five generations of divergent selection for components of efficient lean growth, in a population of Large Wltite pigs. On ad-libitum feeding, a total of 4334 pigs were performance tested, of which 884 selected gilts had measurements of reproduction traits. On a restricted feeding regime, 1558 pigs were tested, which included 336 selected gilts with reproduction records. For pigs given food ad libitum, genetic correlations between litter weights at birth and weaning with daily food intake (0·48 and 0·42, s.e. 0·16) and with growth rate on test (0·65 and 0·52) were positive, but correlations with backfat depths were not significantly different from zero. For pigs given food at a restricted level, litter birth weight was positively genetically correlated with growth rate (0·50, s.e. 0·18) and negatively correlated with backfat depths (-0·48, s.e. 0·16). Phenotypic and environmental correlations between performance test and reproduction traits were all less than 0·10 in magnitude, for pigs tested on either feeding regime. The variation in backfat depth enabled detection of a non-linear relationship between predicted breeding values for litter weight at birth with predicted breeding values for average backfat depth of farrowing gilts performance tested on ad-libitum feeding, but not for gilts tested on restricted feeding. The positive genetic correlations between growth rate and daily food intake with litter traits suggested that selection strategies which change growth and daily food intake may result in relatively greater genetic changes in piglet growth rate than in litter size.
Joint effect of 21 marker loci and effect of realized inbreeding on growth in pigs
- K. Christensen, M. Fredholm, A. K. Winterø, J. N. Jørgensen, S. Andersen
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- 02 September 2010, pp. 541-546
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Four litters produced by father-daughter matings (back crosses) resulting in 35 animals with a theoretical inbreeding coefficient of 25% were typed with 21 independent informative markers. The differences between the two founder animals were estimated, based on the marker information, and it was found that the founder boar had higher genetic potential for proportion of lean meat and lower genetic potential for groivth than the founder sow. The proportion of the genome of each offspring which was identical by descent was investigated. On the basis of these markers the realized inbreeding was found to vary between 7 and 47%. The linear decrease in weight at days 1, 26 and 136, average daily gain and proportion of lean meat regressed on the realized inbreeding were estimated to 0·6 kg, 2·4 kg, 18 kg, 95 g/day and 15 g/kg, respectively. For weight at day 88 a corresponding linear increase of 11 kg was observed. The joint effect of founder differences and realized inbreeding were as expected negative and statistically significant for all growth traits.
Behavioural and hormonal responses of pigs during transport: effect of mixing and duration of journey
- R. H. Bradshaw, R. F. Parrott, J. A. Goode, D. M. Lloyd, R. G. Rodway, D. M. Broom
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- 02 September 2010, pp. 547-554
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Two experiments investigated the welfare of pigs during transport. In experiment 1, 12 groups offour 90-kg pigs were transported to slaughter in a commercial livestock lorry for 1·5 h. Half the animals were transported in their social groups (unmixed condition) and half were transported with groups of previously unfamiliar pigs mixed together (mixed condition). Behaviour was recorded, a general activity index scored and saliva samples taken at different stages of the journey for analysis ofcortisol. Pigs spent most of their time standing in both conditions. The journey was very rough (as revealed by characterization with an accelerometer) and in the unmixed condition the pigs appeared to stand to reduce travel sickness. In contrast, in the mixed condition, this preference for standing seemed to be due to fighting which stressed and exhausted the animals (the general activity index was three times the unmixed condition). Levels of salivary cortisol were higher in the mixed condition at the beginning, middle and end of the journey. In experiment 2, six 35-kg pigs, prepared in advance with jugular vein catheters, were loaded onto a commercial livestock lorry (09.30 h) where they were individually penned. The vehicle remained stationary with the engine off and blood samples were taken at 30-min intervals during the next 8 h (control). Two days later this procedure was repeated while the vehicle was driven for 8 h (on main roads and motorways). Plasma concentrations of cortisol and beta-endorphin increased markedly in both conditions immediately after loading. Cortisol levels were greater (relative to control) at the beginning, in the middle and at the end of the journey. Concentrations of beta-endorphin did not differ between control and experimental conditions except during the final 180 min of the journey when the control levels were higher.
Expression of insulin-like growth factor-1 (IGF-1) and growth hormone-receptor (GHR) mRNA in liver, skeletal muscle and adipose tissue of different breeds of pig
- J. M. Brameld, J. L. Atkinson, T. J. Budd, J. C. Saunders, J. M. Pell, A. M. Salter, R. S. Gilmour, P. J. Buttery
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- 02 September 2010, pp. 555-559
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The work described was carried out to study the expression of insulin-like growth factor 1 (IGF-1) and growth hormone-receptor (GHR) mRNA in liver, skeletal muscle and adipose tissue from three breeds of pig with varying growth characteristics. The three breeds studied were the Large Wlrite, noted for its lean tissue; the Duroc, characterized by its high intramuscular fat content; and the Meishan × Landrace (0·5 Meishan), noted for its fat, poorly conformed carcass and slower growth rate. The probes used were designed to monitor promoter usage for IGF-1 expression and also expression of the extra-cellular domain of the GHR. Eighteen gilts, six of each breed, were given a barley/wheat diet (158 g crude protein, 10·7 g lysine and 13·9 MJ energy per kg), to appetite, for 1 to 2 weeks until they reached about 85 kg. Samples of liver, longissimu s dorsi (LD) muscle and three adipose tissue depots (subcutaneous (SC), perirenal (PR) and omental (OM)) were collected immediately after slaughter and frozen in liquid nitrogen (total time of sample collection to plunging of sample into liquid nitrogen was <3 min), prior to extraction of total RNA and ribonuclease protection assays. Individual serum samples collected at exsanguination were frozen prior to IGF-1 radioimmunoassay. There were no breed differences in the serum IGF-1 concentrations (range 49 to 134 μg/l), or in expression of the GHR gene or either class of IGF-1 transcript in the liver. However, there was a significant difference between the breeds in expression of IGF-1 mRNA in the LD muscle (P < 0·001), the order being Duroc > Wliite > Meishan, with only class 1 transcripts of IGF-1 being found. GHR expression in LD muscle was lower in White than in the other tivo breeds (P = 0·022). There was a significant difference between the breeds in expression of IGF-1 mRNA (only class 1 transcripts present) in the adipose tissue (P = 0-006), the order being Wliite · Duroc · Meishan, and also a significant depot difference, with expression being highest in the SC depot (P < 0·001). There were no differences between the breeds or depots in expression of GHR mRNA in adipose tissue. The observed differences in muscle and adipose tissue IGF-1 expression may relate to the overall growth of the animal.
The influence of feeding regimen and lactation length on growth, carcass characteristics and meat quality of once-bred gilts
- M. Ellis, V. R. Fowler, M. F. Franklin, J. D. Wood, M. A. Varley
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- 02 September 2010, pp. 561-571
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A study was made to investigate the influence of pregnancy feeding level (ad libitum (AL) and restricted (R); 2·0 kg food per day) and lactation length on growth, carcass, meat quality and processing characteristics of pregnant gilts (P) slaughtered after weaning on day 0 (P·0), day 10 (P·10) or day 35 (P·35) after farrowing. Non-pregnant (NP) control gilts were slaughtered at live weights of approximately 95 kg (NP-L), 135 kg (NP-M), and 160 kg (NP-H). P gilts were mated at an average age of 172 days and an average live weight of 97 kg. Pregnancy per se reduced live weight and lean growth rates compared with NP-H animals which were slaughtered at a similar age to the once-bred animals. Weight loss during lactation tended to increase with lactation length and was higher for gilts given food ad libitum during pregnancy compared with restricted animals. The weight of closely trimmed lean in the carcass was similar for the P·0, P·10 and P·35 groups (59·5 v. 62·2 v. 58·8 kg respectively; average s.e. 2·42) and all once-bred gilt groups virtually doubled trimmed lean yields during pregnancy and lactation. Curing yields were similar for P and NP gilts. As lactation length increased, the fat content of the longissimus dorsi and of the overlying subcutaneous fat layers tended to decrease and the moisture content of these two tissues increased. The major impact offeeding level was on fat levels which were significantly higher for AL animals. Trimmed lean yields were also higher for AL gilts suggesting that lean growth rates were not being maximized on the R feeding regime. Subjective muscle colour scores indicated that the longissmus dorsi from P gilts was darker than from NP-L animals and muscle colour tended to become darker with increasing lactation length. There were few significant differences between treatment groups for eating quality. Meat from once-bred gilts was generally judged to be tougher than that from NP-L animals and toughness generally increased with lactation length. This study confirms the potential of the once-bred gilt as an efficient producer of pig meat but raises issues regarding meat quality that require further research.
The effects of dietary protein and energy levels of diets offered during lactation on the lactational and subsequent reproductive performance of first-litter sows
- S. M. Tritton, R. H. King, R. G. Campbell, A. C. Edwards, P. E. Hughes
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- 02 September 2010, pp. 573-579
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A total of 315 first parity sows were used in two experiments to establish the lactational and subsequent reproductive performance of first-litter sows in response to varying levels of dietary amino acids and digestible energy (DE) offered during lactation. In the first experiment, sows were offered five diets ranging in lysine content from 6·2 to 15·1 g/kg. In the second experiment sows were offered five diets with a similar lysine: DE ratio (0·88 to 0·85 g/MJ) but ranging in DE content from 12·6 to 15·1 MJ/kg. Voluntary food intake during lactation was unaffected by lysine or DE content of the diets. Piglet pre-weaning growth was similarly unaffected by dietary DE content but responded in a curvilinear manner with increasing dietary lysine. Sow body-weight loss during lactation was unaffected by dietary lysine but declined with increasing DE content up to 13·8 MJ/kg. Backfat loss was lowest for sows offered the lowest lysine diet and tended to reach a plateau at a dietary level of 10·6 g lysine per kg. In response to dietary DE content, backfat loss tended to be highest for sows offered the diet of lowest DE content and declined with increasing DE content up to 15·1 MJ DE per kg. The subsequent weaning to remating interval was unaffected by dietary DE content. Subsequent litter size was similarly unaffected by dietary DE content but was significantly higher for sows offered the two higher, compared with the two lower, lysine diets (10·7 v. 9·6 born alive, s.e.d. 0·5, P < 0·05). The results suggest that current amino acid recommendations for lactating first-litter sows are inappropriate and may be constraining both milk production and subsequent reproductive performance.