Carcass Weight Gain Research Articles

Composição corporal e exigências nutricionais de macrominerais para novilhas em crescimento das raças Guzerá e Holandesa

Foram utilizadas 22 novilhas, 11 da raça Holandesas e 11 da Guzerá, com peso vivo (PV) inicial de 189kg. Após o abate inicial de seis animais de cada raça, outros dois grupos, cinco animais de cada raça, passaram a receber dieta à base de feno de Tifton 85 (Cynodon spp.), milho, farelo de soja e mistura mineral, para ganho diário de 1kg de peso vivo (PV). O abate final ocorreu após ganho de peso de 100kg. Durante os dois abates, todos os tecidos foram pesados e amostrados, retirando-se como amostra representativa da carcaça entre a nona e a décima primeira costela para determinação dos conteúdos corporais de Ca, P, Mg, Na e K. Determinaram-se a composição corporal e as exigências nutricionais desses minerais para ganho de 1kg de PV. Houve decréscimo na concentração dos cinco macrominerais no peso de corpo vazio e no peso ganho com a elevação do PV. Não houve diferença entre as raças quanto às exigências nutricionais dos macrominerais. As exigências dietéticas totais de Ca, P, Mg, Na e K para animais de 200kg de PV foram de 11,57; 5,97; 0,36; 1,30 e 0,86g/dia, respectivamente.

Desempenho produtivo e eficiência bioeconômica de bovinos Nelore e Caracu selecionados para peso aos 378 dias de idade recebendo alimentação à vontade ou restrita

Avaliou-se o desempenho de 56 bovinos machos não-castrados de três grupos genéticos, com idade média de 18 meses, submetidos à alimentação à vontade ou restrita, em confinamento. Doze animais foram abatidos no início do experimento e os demais (16 Nelore selecionados, 12 Nelore não-selecionados e 16 Caracu selecionados com peso vivo médio inicial de 404, 345 e 434 kg, respectivamente) foram distribuídos em delineamento inteiramente casualizado, em esquema fatorial 2 x 3, composto por dois níveis de alimentação (restrito = consumo de 65 g de MS/kgPV0,75 por dia e ad libitum = fornecimento do alimento duas vezes ao dia) e três grupos genéticos. O volumoso utilizado foi a silagem de milho e o concentrado foi constituído de milho moído, farelo de algodão, uréia, monensina e mistura mineral, com relação volumoso:concentrado 50:50. O abate foi realizado quando cada animal atingiu 4 mm gordura subcutânea à altura da 12ª costela, avaliada por ultra-som. Os grupos genéticos apresentaram ganhos médios diários de peso vivo e pesos de corpo vazio e de carcaça semelhantes, não havendo interação grupo genético × nível de alimentação. Os ganhos de peso vivo e os pesos de corpo vazio e de carcaça foram maiores nos animais alimentados ad libitum. Somente os consumos de matéria seca em kg/dia sofreram influência tanto do nível de alimentação quanto do grupo genético. Os animais Caracu apresentaram os maiores consumos, seguidos pelos Nelore selecionados. Os Nelores não-selecionados apresentaram melhor eficiência bionutricional e menor custo de produção da arroba que os demais grupos genéticos.

Effect of Duration of Zilpaterol Hydrochloride Treatment on Carcass Characteristics and Weight Gain in Grazing Pelibuey Lambs

Salinas-Chavira, J., Domínguez-Muñoz, M., Díaz-Martínez, R., Cruz-Bautista, P., Montaño-Gómez, M.F. and Arzola-Alvarez, C. 2006. Effect of duration of zilpaterol hydrochloride treatment on carcass characteristics and weight gain in grazing Pelibuey lambs. J. Appl. Anim. Res., 29: 25–28. The effect of zilpaterol hydrochloride (ZH) supplementation on carcass characteristics and weight gain were studied in grazing Pelibuey lambs. Thirty-six intact male Pelibuey sheep, (21.42±3.32 kg) were kept in three paddocks with Angleton grass (Dichantium aristatum) and were fed a supplement (sorghum, soybean meal, urea, molasses, tallow and minerals) containing 21.76% crude protein and 2.77 Meal I kg ME during 60 days feeding trial. Three paddocks formed the corresponding experimental groups: T1 (control), with no ZH in the supplement; T2 received 10 ppm ZH in supplement during the last 20 days of the trial and T3 received ZH during the last 30 days. The backfat was thinner (P<0.05) in both ZH groups than in the control group, measuring 0.28, 0.24 and 0.24 cm in T1, T2 and T3, respectively. The Longissimus dorsi measured 6.53, 6.24 and 5.84 cm2, respectively, and did not differ among dietary treatments. The average daily gain was also similar (P>0.05) among all experimental groups. It may be concluded that supplementation of zilpaterol hydrochloride during different intervals reduced the backfat cover in grazing Pelibuey sheep fed on supplemental concentrate.

Exigências líquidas de proteína e energia para ganho de peso de novilhos Nelore alimentados com dietas contendo grão de milho úmido e gordura protegida

Neste trabalho, as exigências líquidas de energia e proteína líquidas para ganho de peso foram estimadas pela técnica de abate comparativo utilizando-se 56 novilhos Nelore com peso médio inicial de 432 kg. A análise da composição da 9ª-10ª-11ª costelas foi utilizada para estimativa da composição do corpo vazio. Oito novilhos foram abatidos no início do período experimental, para o cálculo da composição corporal inicial, e os demais, alimentados durante 70 dias com dietas contendo 60% de concentrado na MS, composto de grão de milho seco ou úmido, com ou sem gordura protegida da biohidrogenação ruminal. O peso médio dos animais ao abate foi 528 kg. Apenas o ganho de peso de carcaça quente foi maior nos tratamentos com gordura. Não houve diferença na composição do corpo vazio, nas taxas de deposição e na composição do ganho de peso vazio. As exigências de energia e proteína foram de 2,97 Mcal e 0,171 kg por kg de ganho de peso corporal vazio (GPVz), respectivamente, e o ganho de gordura foi de 0,215 kg por kg de GPVz. A utilização do grão de milho úmido e de 4% de gordura protegida na alimentação de novilhos Nelore não alterou a composição corporal e as exigências de energia e proteína.

Genetic Parameters and Responses in Growth and Body Composition Traits of Pigs Measured under Group Housing and Ad libitum Feeding from Lines Selected for Growth Rate on a Fixed Ration

The main objective of this study is to examine genetic changes in growth rate and carcass composition traits in group housed, ad libitum fed pigs, from lines of Large White divergently selected over four years for high and low post-weaning daily gain on a fixed but restricted ration. Genetic parameters for production and carcass traits were also estimated by using average information-restricted maximum likelihood applied to a multivariate individual animal model. All analyses were carried out on 1,728 records of group housed ad libitum fed pigs, and include a full pedigree of 5,324 animals. Estimates of heritability (standard errors in parentheses) were 0.11 (0.04) for lifetime daily liveweight gain (LDG), 0.13 (0.04) for daily carcass weight gain (CDG) and 0.28 (0.06) for carcass backfat (CFT). Genetic correlations between LDG and CDG were highly positive and between LDG and CFT negative, suggesting that selection for lifetime daily gain under commercial conditions of group housing with ad libitum feeding would result in favourable improvement in carcass traits. CFT showed negative genetic correlations with CDG. Correlated genetic responses evaluated as estimated breeding values (EBVs) were obtained from a multivariate animal model-best linear unbiased prediction analysis. After four years of divergent selection for 6 week post-weaning growth rate on restricted feeding, pigs performance tested on ad libitum feeding in groups exhibited changes in EBVs of 6.77 and -9.93 (g/d) for LDG, 4.25 and -7.08 (g/d) for CDG, and -1.42 and 1.55 (mm) for CFT, in the high and low lines, respectively. It is concluded that selection for growth rate on restricted feeding would significantly improve genetic performance and carcass composition of their descendants when group housed and ad libitum fed as is a common commercial practice.

Use of Lotus corniculatus containing condensed tannins to increase summer lamb growth under commercial dryland farming conditions with minimal anthelmintic drench input

A 95-day rotational grazing experiment was conducted in the summer of 2002/2003 under dryland farming conditions to compare effects of grazing Lotus corniculatus L. (Birdsfoot trefoil; cv. Grasslands Goldie) and perennial ryegrass ( Lolium perenne)/white clover ( Trifolium repens) pasture on body growth and dynamics of nematode parasite infection in Suffolk × Romney weaned lambs fed ad libitum. Half of the lambs ( n = 30), grazing either L. corniculatus or pasture received oral anthelmintic at the start and at monthly intervals (i.e., regular-drenched groups), whilst the remaining 30 lambs in each treatment only received oral anthelmintic when mean faecal nematode egg counts (FECs) exceeded 1000 eggs/g wet faeces (i.e., trigger-drenched groups). This only occurred on day 58 for both groups. Trigger and regular-drenched lambs grazed separate areas. Total condensed tannin (CT) concentration in the diet selected was 31–40 g CT/kg DM for L. corniculatus, with only trace amounts in pasture. In vitro organic matter (OM) digestibility (OMD), digestible OM in dry matter (DOMD), and metabolisable energy (ME) concentration were higher for L. corniculatus versus pasture and declined less under drought conditions versus grass-based pasture. Regular-drenched lambs grazing L. corniculatus had higher liveweight gain (LWG; 298 g/day) and carcass weight gain (133 g/day) than all other groups, whilst trigger-drenched lambs grazing L. corniculatus had higher LWG (228 g/day) and carcass gain (99 g/day) versus regular-drenched (200; 66 g/day) and trigger-drenched (187; 63 g/day) lambs grazing pasture. Carcass fatness was lower for trigger-drenched lambs versus regular-drenched lambs, when fed either L. corniculatus or pasture. Dag score was consistently lower for regular-drenched lambs grazing L. corniculatus versus pasture; trigger-drenched lambs showed similar effects up to day 48, with no differences between the groups thereafter. Regular anthelmintic treatment maintained FECs at low values, while parasitised grazed lambs on L. corniculatus tended to have higher FECs than pasture fed lambs. Relative to trigger-drenched lambs that grazed pasture, grazing L. corniculatus reduced worm burdens at slaughter of Haemochus contortus, Teladosargia spp., Nematodirus spp. and Cooperia spp., but higher burdens of Trichostrongylus spp., Chabertia ovina, Oesophagostonum spp. and Trichuris ovis ocurred in L. corniculatus fed lambs. Grazing Lotus corniculatus L. (Birdsfoot trefoil; cv. Grasslands Goldie) under dryland farming conditions can increase growth of weaned lambs, whilst reducing reliance on anthelmintic drenches to control parasites. These effects are possibly due to increased metabolisable protein supply, from the protein binding action of CT, enabling the lambs to grow faster when carrying a parasite burden, and to L. corniculatus better maintaining its high ME value under drought conditions. Mechanisms for the action of CT are discussed.

Genetic parameters and responses of performance and body composition traits in pigs selected for high and low growth rate on a fixed ration over a set time

Two lines of Large White pigs of common genetic origin were divergently selected over four years for high and low growth rate during a 6 week post-weaning test period in which all pigs were fed the same total amount of food (80% of estimated ad libitum intake). Genetic parameters and direct and correlated responses in performance and carcass traits were estimated on 2884 pigs with pedigrees comprising a total of 5324 animals, with restricted maximum likelihood and best linear unbiased prediction methods applied to a multi-trait animal model. Estimates of heritability (± SE) were 0.19 ± 0.04 for lifetime daily gain (LDG), 0.16 ± 0.03 for test daily gain (TDG), 0.25 ± 0.04 for ultrasound P2 backfat (UBF) and 0.16 ± 0.03 for food conversion ratio during test (TFC), and 0.15 ± 0.04 for daily carcass weight gain (CDG), 0.43 ± 0.06 for carcass backfat (CFT) and 0.40 ± 0.06 for carcass lean percentage (LEAN). Common litter effects for TDG, UBF and TFC were less than 5% and for LDG, 17% of total phenotypic variance. Genetic correlations between performance and carcass traits were moderately to highly favourable. After four years of divergent selection for growth rate, the selection responses in estimated breeding value (EBV) for TDG were 40.14 and -41.11 g (SED 2.95) for the high and low growth lines, respectively. The regressions of EBV on year of birth, indicate that the annual genetic trend for TDG, was 8.73 g/yr in the high and -8.48 g/yr in the low lines (P < 0.001). Correlated genetic responses in the high and low lines respectively were 5.28 g and -12.40 g (SED 2.09) in LDG, -0.35 mm and 0.56 mm (SED 0.009) in UBF, -0.145 units and 0.185 units (SED 0.012) in TFC, 3.17 g and -10.97 g (SED 1.53) in CDG, -1.13 mm and 1.01 mm (SED 0.155) in CFT and 1.24% and -1.27% (SED 0.150) in LEAN. It was concluded that selection for increased post-weaning daily gain on a ration of fixed amount reduces the age at slaughter and the level of backfat and increases the efficiency of food utilisation, weight and leanness of pig carcasses.

Genetic parameters and responses of performance and body composition traits in pigs selected for high and low growth rate on a fixed ration over a set time

Two lines of Large White pigs of common genetic origin were divergently selected over four years for high and low growth rate during a 6 week post-weaning test period in which all pigs were fed the same total amount of food (80% of estimated ad libitum intake). Genetic parameters and direct and correlated responses in performance and carcass traits were estimated on 2884 pigs with pedigrees comprising a total of 5324 animals, with restricted maximum likelihood and best linear unbiased prediction methods applied to a multi-trait animal model. Estimates of heritability (± SE) were 0.19 ± 0.04 for lifetime daily gain (LDG), 0.16 ± 0.03 for test daily gain (TDG), 0.25 ± 0.04 for ultrasound P2 backfat (UBF) and 0.16 ± 0.03 for food conversion ratio during test (TFC), and 0.15 ± 0.04 for daily carcass weight gain (CDG), 0.43 ± 0.06 for carcass backfat (CFT) and 0.40 ± 0.06 for carcass lean percentage (LEAN). Common litter effects for TDG, UBF and TFC were less than 5% and for LDG, 17% of total phenotypic variance. Genetic correlations between performance and carcass traits were moderately to highly favourable. After four years of divergent selection for growth rate, the selection responses in estimated breeding value (EBV) for TDG were 40.14 and -41.11 g (SED 2.95) for the high and low growth lines, respectively. The regressions of EBV on year of birth, indicate that the annual genetic trend for TDG, was 8.73 g/yr in the high and -8.48 g/yr in the low lines (P < 0.001). Correlated genetic responses in the high and low lines respectively were 5.28 g and -12.40 g (SED 2.09) in LDG, -0.35 mm and 0.56 mm (SED 0.009) in UBF, -0.145 units and 0.185 units (SED 0.012) in TFC, 3.17 g and -10.97 g (SED 1.53) in CDG, -1.13 mm and 1.01 mm (SED 0.155) in CFT and 1.24% and -1.27% (SED 0.150) in LEAN. It was concluded that selection for increased post-weaning daily gain on a ration of fixed amount reduces the age at slaughter and the level of backfat and increases the efficiency of food utilisation, weight and leanness of pig carcasses.

Residual Pathogenic Effects of Infectious Bursal Disease Vaccines Containing Intermediate and Hot Strains of the Virus in Broiler Chickens

The detrimental outcomes of intermediate and hot infectious bursal disease virus (IBDV) vaccine strains in broiler chickens were the objective of this study. Carcass weight gain, bursal enlargement and hemorrhage in the muscles were the parameters considered to monitor these effects. Two hundred, day-old broiler chicks were divided into eight groups namely A, B, C, D, E, F, G and H. Chicks in groups A, B and C were vaccinated with intermediate, hot and both vaccine strains of the virus respectively whereas group D left without vaccination as control in closed pens. Chicks in groups E, F, G and H were treated similarly but in open pens. In both systems of rearing, the highest effects of the vaccines on chicks performance was observed for those vaccinated with the hot strain of IBDV, followed by intermediate strain vaccinated chickens and least effect on those vaccinated with the intermediate and boostered with the hot one. The results obtained also showed that chickens reared in closed pens put slightly higher (p<0.05) body weight, low levels of bursal enlargement and relatively low hemorrhage in the muscles as compared to those reared in open pens. As a conclusion and recommendation, it was advised to vaccinate chickens with intermediate strains of IBD at 2 weeks old and booster them with the hot one at 3 weeks in closed systems.

Effect of live weight gain of steers during winter grazing: II. Visceral organ mass, cellularity, and oxygen consumption.

Two experiments were conducted to examine the effect of BW gain during winter grazing on mass, cellularity, and oxygen consumption of splanchnic tissues before and after the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range supplemented with 0.91 kg/d of a 41% CP supplement (NR). At the end of winter grazing, four steers were selected randomly from each treatment for initial slaughter to measure organ mass, cellularity, and oxygen consumption. All remaining steers were placed into a feedlot and fed to the same backfat end point (1.27 cm). Six steers were selected randomly from each treatment for final organ mass, cellularity, and oxygen consumption. Initial empty BW (EBW) was greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both Exp. 1 and 2 (355 > 263 > 207 +/- 6.5 kg and 337 > 274 > 205 +/- 8.7 kg, respectively). For both experiments, the initial total gastrointestinal tract (GIT; g/kg of EBW) proportional weight was greater (P < 0.05) in NR steers than in LGW, and LGW steers had greater (P < 0.05) initial GIT proportional weight than HGW steers. Proportional weight of total splanchnic tissues (TST; g/kg of EBW) did not differ (P < 0.19) among treatments. Initial duodenal RNA concentration and RNA:protein were greater (P < 0.02) in LGW than in HGW steers, and NR steers were intermediate. Initial in vitro liver O2 consumption was greater (P < 0.09) in HGW and LGW than in NR steers (34.5 > 16.9 mL/min), whereas initial small intestinal oxygen consumption was greater (P < 0.01) in LGW than in HGW and NR steers (12.1 > 5.2 mL/min). Ruminal papillae oxygen consumption did not differ (P < 0.55) among treatments. The rate of decrease of GIT (g x g EBW(-1) x d(-1)) during finishing was greater in NR than in HGW and LGW steers in both Exp. 1 and 2, but mesenteric fat (g x g EBW(-1) x d(-1)) increased for NR steers, resulting in a similar (P < 0.75) increase in TST across the finishing period for all treatments. Similar rates of increase in TST across the finishing phase corresponded with similar rates of live and carcass weight gain among treatments. Our data support the hypothesis that increased visceral organ mass increases maintenance energy requirements of growing cattle.

High production dairy-beef cattle grazing systems: a review of research in the Manawatu

During a span of 20 years, eight farmlet-scale experiments conducted in the Manawatu used a simple system of grazing management to maximise pasture growth and utilisation. Farmlets of 1.6 ha were stocked annually with 12 Friesian bulls (7.4 wintered/ ha) from early November at 3 months-of-age (70-80 kg liveweight (LW)) until slaughter during December - March at 16 - 19 months (350 - 420 kg LW). The grazing management system involved seasonal adjustment in pasture spelling intervals, and an increase in grazing pressure in spring by addition of 3-month-old weaner bulls followed by the progressive removal of 'finished' animals during summer. With this control over feed supply and demand and the inherent capacity of growing bulls to cope with changes in feed availability, old permanent pasture producing approximately 13 t dry matter/ha/yr was conver ted to approximately 1000 kg/ha/yr of net carcass weight gain. Using loafing pads in winter to reduce treading damage on wet soils and increase pasture utilisation and growth, increased annual LW gain (LWG)/ha by 2%. Controlling the intensity of defoliation in summer through timely removal of bulls for slaughter increased average daily gain (ADG) during autumn and winter, but annual LWG/ha by only 1%. Pastures renewed with improved cultivars and species produced more forage in summer (red clover), autumn (prairie grass) and winter, identified as per iods of feed deficit for old permanent pastures. Strategic inputs of nitrogen (N) fertiliser (100 kg N/ha/yr) in autumn or in spring on old permanent pasture, in conjunction with irrigation (approximately 250 mm/ season) during November - March, and in combination with cool season active grasses, all increased annual meat output by up to 12% above that possible from old permanent pasture, by extending the duration of stocking in summer, increasing ADG, or a combination of both. While these gains are important, the studies highlighted the very high levels of output sustained from year-round all-grass grazing systems based on principles for maximising pasture growth and utilisation. Those high yields remain a benchmark in terms of the biological efficiency of growing and converting pasture to animal product, although the economic optimum was at a lower stocking rate and level of output. Keywords: dairy beef, grazing systems, liveweight gain, pasture utilisation

The eating quality of meat of steers fed grass and/or concentrates

The objective was to determine, relative to animals expressing their full potential for carcass growth, the impact on meat quality of increasing carcass growth of grazing steers by supplementing with concentrates or by increasing grass supply. Sixty-six continental (Limousin and Charolais) crossbred steers (567 kg) were assigned to one of six diets: (1) 18 kg grass dry matter (DM); (2) 18 kg grass DM grass and 2.5 kg concentrate; (3) 18 kg grass DM and 5 kg concentrate; (4) 6 kg grass DM and 5 kg concentrate; (5) 12 kg grass DM and 2.5 kg concentrate; or (6) concentrates daily. Animals were slaughtered after an average of 95 days. Samples of the M. longissmus dorsi (LD) were collected at the 8–9th rib interface and subjected to sensory analysis and to other assessments of quality following 2, 7, or 14 days aging. Carcass weight gain averaged 360, 631, 727, 617, 551 and 809 g/day for treatments 1 to 6, respectively. There was no difference between diets for colour, Warner–Bratzler shear force (WBSF) or any sensory attribute of the LD. WBSF was negatively correlated with ( P<0.05) carcass growth rate (−0.31) but only a small proportion of the variation in meat quality between animals could be attributed to diet pre-slaughter or carcass fatness. It is concluded that high carcass growth can be achieved on a grass-based diet without a deleterious effect on meat quality.

Effect of sward surface height on herbage intake and performance of finishing beef cattle

This study examined the effects of contrasting sward surface height (SSH) on the herbage intake, ingestive behaviour, and performance of steers grazing perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pastures in New Zealand during summer, and the influence of this initial treatment contrast on subsequent cattle performance under common grazing conditions during early autumn. Twenty‐four Angus‐cross steers, 26 months old and with an initial liveweight of 522 ± 7.6 kg, were continuously stocked on swards maintained at SSH of 5 and 10 cm (L versus H) from 18 November 1996. Six steers from each treatment were slaughtered on 4 March and the remaining animals were grazed for another 5 weeks on common pastures until the final slaughter on 8 April 1997. Herbage intake (estimated by the n‐alkane technique) and liveweight gain over the SSH contrast period, and carcass weight at first slaughter, were higher for steers grazed at 10 cm than for those grazed at 5 cm (7.5 ± 0.21 versus 5.0 ± 0.18 and 7.8 ± 0.38 versus 5.0 ± 0.33 kg DM d−1 from two intake estimates, P < 0.05 for each comparison; 1.10 ± 0.23 versus 0.32 ± 0.21 kg d−1, P < 0.01; and 332 ± 10.6 versus 287 ± 7.5 kg, P < 0.05, respectively). SSH did not affect carcass or meat quality characteristics. Liveweight and carcass weight gain per hectare were 71 % and 43% greater (318 versus 186 kg and 166 versus 116 kg over 105 days) for steers grazing at 10 cm despite the lower stocking rate (2.86 versus 5.80 steers ha−1) maintained by the tall swards. Significant differences in carcass weight were still evident at the end of the compensatory period between the steer groups originally on treatments H and L (335 ± 9.4 versus 297 ± 9.4 kg, P < 0.05). These results suggest that maintaining a sward height of 10 cm offers advantages in terms of individual animal output and output per hectare compared with grazing at 5 cm, and that compensatory growth does not seem to be an important phenomenon in heavy (over 500 kg liveweight) finishing steers.

Growth Hormone Promotes Somatic and Skeletal Muscle Growth Recovery in Rats Following Chronic Protein-Energy Malnutrition

The efficacy of recombinant human growth hormone (GH) and/or a diet enriched in protein and energy to improve growth recovery following prolonged malnutrition was examined in male rats food-restricted from birth until 120 d of age. At d 121, restricted rats were randomly assigned to recovery groups receiving either a control or enriched diet with or without daily subcutaneous injections of GH. Rats were killed after 16 or 47 d of recovery. At d 16, GH treatment stimulated liver, heart, plantaris, soleus, carcass and body weight gain and inhibited fat gain when compared to recovery controls. Rats receiving GH also exhibited the highest serum insulin-like growth factor-I (IGF-I) concentrations and total muscle protein. At d 47, GH effects on body and muscle recovery were minimal, and differences among recovery groups in serum IGF-I concentration and total muscle protein were no longer present. Consumption of an enriched diet increased fat pad and liver mass, but did not promote muscle recovery. There were no differences among treatment groups in skeletal muscle IGF-I mRNA levels at d 16 or 47. In summary, GH had positive effects on somatic and skeletal muscle growth early in the recovery process, possibly via endocrine IGF-I-stimulated protein accretion. In contrast, the enriched diet promoted fat deposition with no impact on skeletal muscle growth recovery.

The effect of feed restriction prior to slaughter on performance and meat quality of pigs

Feed restriction prior to slaughter may reduce live and carcass weight gain (Murray and Jones, 1994) and meat quality (Warriss, 1982) but can reduce carcass contamination and the amount of waste to be disposed of at the slaughter house (Eikelenbloom et al., 1991). Most literature studies are however based on a single feed restriction while group housed pigs may be slaughtered over a period of time and can therefore be subjected to several periods of feed restriction. This study was conducted to examine the effects of feed restriction prior to slaughter on the production performance and meat quality of group housed finishing pigs.There were three experimental treatments (1) control - ad libitum access up to point of transport, feeders closed off for 12 hours (Treatment 2) and feeders closed off for 20 hours (Treatment 3) prior to transport to the slaughter house. All pigs had unrestricted access to water. Four hundred and eighty six, 35 kg crossbred pigs, housed in groups of 18, were randomly allocated to 9 replicates of the three treatments. Pigs were slaughtered when a target live weight of 102 kg was reached. Production performance was recorded on a weekly basis when the first pig in any treatment approached 95 kg live weight until all pigs were slaughtered.

Responses in the growth of body components of finishing lambs to additional metabolizable energy supplied from either grass silage or concentrates

AbstractTwo experiments involving 213 finishing lambs were carried out to examine the responses in growth rate and carcass composition to the addition ofmetabolizable energy (ME) to a mixed diet in theform ofeither grass silage concentrate. In the second experiment the performance of lambs offered silage only was also compared at equal intake with the performance of lambs given mixed diets. On average the silages contained 224 g dry matter (DM) per kg; 148 g crude protein (CP) per kg DM; 86 g ammonia-nitrogen per kg total nitrogen and 723 g digestible organic matter per kg DM. Concentrates were based on barley and soya-bean meal and contained 181 g CP per DM. Responses in carcass weight gain when additional ME was added to mixed silagelconcentrate diets in theform ofgrass silage and concentrates were 9·2 and 10·2 (s.e. 0·90) gIM] respectively in experiment 1 and 9·8 and 10-(s.e. 0·33) g/MJ respectively in experiment 2, and responses in energy retention in experiment 2 were 0·34 and 0-(s.e. 0·012) MJ/M] respectively. However carcass gain and energy retention sustained by a silage only diet were only 0·67 and 0·70 respectively of those sustained by a high-concentrate diet at the same ME intake. The diet did not significantly affect body or carcass composition.

Comparative studies of herbage intake and performance of lambs grazing Yorkshire fog (Holcus lanatus) and perennial ryegrass (Lolium perenne) pastures in winter

A comparative trial was carried out to assess the grazing behaviour, and performance of lambs grazing Yorkshire fog (Holcus lanatus cv. Massey Basyn)/white clover (Trifolium repens cv. Grasslands Tahora) and perennial ryegrass (Lolium perenne cv. Grasslands Nui)/white clover pastures and to evaluate the effects of low concentrations of condensed tannins (CT) in the grasses on body and wool growth under continuous stocking management in winter. Thirty‐six spring‐born female lambs of mean initial live weight 29 ± 2.3 kg were allocated to balanced groups in sets of six, with three replicates of the two pasture treatments. Individual paddocks were grazed continuously for 7 weeks from 30 May to 15 July. Half of the lambs were drenched with 10 g polyethylene glycol (PEG: molecular weight 4000) twice daily at 0830 and 1700 hrs and the remaining lambs were drenched with water as a control. Yorkshire fog swards had greater herbage mass and bulk density, lower proportions of live leaf and white clover, and a higher proportion of dead material than perennial ryegrass swards. Ryegrass had a consistently superior organic matter digestibility (80 vs 77 ± 0.3%, P < 0.05) and higher total CT content than Yorkshire fog (2.1 vs 1.8 + 0.07 g/kg DM, P < 0.05). Lambs had higher herbage digestible organic matter intake (888 vs 716 ± 24.8 g/day, P < 0.05) and carcass weight gain (89 vs 70 ±2.7 g/day, P < 0.05) on ryegrass than on Yorkshire fog. PEG administration did not significantly influence liveweight or carcass gain, but improved the rate of wool growth in lambs on ryegrass and decreased it in lambs on Yorkshire fog (Species x PEG interaction, P < 0.01). It is concluded that the better performance of lambs grazing the perennial ryegrass pastures reflected greater herbage intake and diet digestibility. Concentrations of CT in both pastures were too low to materially affect animal performance.

Comparative studies of herbage intake and performance of lambs grazing Yorkshire fog (Holcus lanatus) and tall fescue (Festuca arundinacea) pastures under rotational management in summer

Grazing experiments were conducted on Yorkshire fog (Holcus lanatus cv. Massey Basyri)/white clover (Trifolium repens cv. Grasslands Tahora) and tall fescue (Festuca arundinacea cv. Grasslands Roa)/white clover pastures in late spring‐summer (Nov‐Jan, Experiment 1) and summer‐early autumn (Jan‐Mar, Experiment 2) to assess behaviour and performance of lambs and to evaluate the effects of low concentrations of condensed tannins (CT) in the grasses on lamb performance. In each experiment, 48 lambs were allocated to three groups, balanced for previous grazing experience and sex, in sets of 16. One group was slaughtered at the start of the experiment to measure carcass weight; the other two groups of lambs rotationally grazed paddocks within each pasture. Half of the lambs within each pasture were drenched with 10 g polyethylene glycol (PEG; mol. weight 3350) twice daily at 0830 and 1630 hrs and the remaining lambs were drenched with water as a control. There were similar sward surface height, herbage mass, and bulk density on both swards. Yorkshire fog had a higher proportion of sown grass and lower proportions of other grasses and white clover than tall fescue. There was slightly higher total N (3.37 vs 3.30 ± 0.013%, P< 0.05) on tall fescue than on Yorkshire fog in summer, but no significant difference in organic matter digestibility (OMD) for the diets from the two pastures. The diet from Yorkshire fog had higher CT concentrations overall. Herbage organic matter (OM) intake was not significantly different between the two pastures overall, but was significantly reduced by PEG administration in Experiment 2 (P < 0.01 ). Previous grazing experience had no significant effects on lamb performance. Lambs had greater carcass weight (14.7 vs 13.9 ± 0.2 kg, P < 0.05) and faster carcass weight gain (32 vs 20 ± 3.1 g/day, P < 0.05) on Yorkshire fog than on tall fescue in Experiment 1, but not in Experiment 2, and faster rate of clean wool growth on Yorkshire fog than tall fescue in Experiment 2 (123 vs 112 ± 2.8 mg/ 100 cm2 per day, P < 0.05). It is concluded that Yorkshire fog cv. Massey Basyn offers potentially greater nutrient intake and weaned lamb performance than tall fescue cv. Grasslands Roa in summer pastures. The limited content of condensed tannins in the Yorkshire fog pasture had no measurable effects on lamb performance, and it is suggested that particularly low concentrations of CT measured in tall fescue may have been an artefact of the analytical process.

Grass silage as a basic feed for store lambs. 2. Effect of harvesting system and chop length of grass silage on silage intake and performance of store lambs

AbstractA perennial ryegrass sward was cut at a leafy stage of growth and harvested with different harvesters to produce silages differing in chop length to evaluate the effect of silage chop length on silage intake and on the performance of store Iambs when silage was fed as the sole diet. The silage was harvested in late May either as long silage (L), single‐chopped (S). double‐chopped (D). long precision‐chopped (LP) or medium precision‐chopped (MP) silage with (he appropriate machinery. The silages were treated with formic acid at 2.5 1 t−1. were well preserved (pH 3.7–3.8) and were of high dry‐matter digestibility [749–810 g DMD kg−1 dry‐matter (DM)]. The silages were fed ad libitum as the sole diet to Suffolk crossbred store lambs over a period of 11 weeks.Silage intake and lamb performance progressively increased as silage chop length declined from 32.4 cm (L) to 6.8 cm (MP). Silage intakes were 572, 661, 750, 893 and 1129 (± 21) g DM d−1 for silages L, S, D, LP and MP respectively. The corresponding daily liveweight gains were ‐3, 40, 53, 85 and 151 (± 7.6) g d−l. Similar increases in empty body weight gain and carcass weight gain were obtained as silage chop length declined.Rumen retention time (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake in the week before slaughter, was much shorter for silages LP and MP compared with silages L or S. Silage intake was negatively related to RRT(b= ‐24.5 ± 6.1 gDM h−l RRT).The results of this study showed that high intakes of grass silage and liveweight gains were achieved when grass was cut at a leafy stage of growth and harvested with a precision‐chop harvester set to produce a moderate chop length (7 cm). The feeding of long or flail‐chopped silages resulted in lower intakes and lower liveweight gains.

Effect of condensed tannins upon the performance of lambs grazing Lotus corniculatus and lucerne (Medicago sativa)

SUMMARYA grazing experiment, conducted for 22 weeks in 1992/93 at Aorangi Research Station, AgResearch Grasslands, Manawatu, New Zealand, compared the productivity of weaned lambs grazing Lotus corniculatus (birdsfoot trefoil) and lucerne (Medicago sativa). Effects of condensed tannins (CT) in lotus were evaluated by studying the responses of lambs to twice daily oral supplementation with polyethylene glycol (PEG). A rotational grazing system with restricted feed allowance was used. Measurements were made of pre- and post-grazing herbage mass, the composition of the feed on offer and diet selected, voluntary feed intake (VFI), liveweight gain (LWG), carcass growth, wool growth and the concentration of metabolites in rumen fluid. For both lotus and lucerne swards, the diet selected was mainly leaf. Lotus contained 34 g total CT/kg dry matter in the diet selected, whilst there were essentially no CT in lucerne. Compared to lambs grazing lucerne, lambs grazing lotus had slightly lower VFI, and higher LWG, carcass weight gain, carcass dressing-out percentage and wool growth. PEG supplementation had no effect on these measurements or upon the composition of rumen fluid in lambs grazing lucerne. However, in lambs grazing lotus, PEG supplementation reduced wool growth (10·9 ν. 12·1 g/day), slightly reduced LWG (188 ν. 203 g/day), increased rumen ammonia concentration, and increased the molar proportions of /.so-butyric, isovaleric and n-valeric acids and protozoa numbers in rumen fluid. PEG supplementation did not affect carcass gain, carcass fatness or the molar proportion of rumen acetic, propionic or n-butyric acids in lambs grazing lotus. It was concluded that the principal effect of CT in growing lambs grazing lotus was to increase wool growth without affecting VFI, thereby increasing the efficiency of wool production, that the greater rate of carcass gain of lambs grazing lotus than those grazing lucerne was mainly caused by factors other than CT and that CT did not affect the rumen fermentation of carbohydrate to major volatile fatty acids.