Ryegrass Pasture Research Articles

Non-ryegrass pastures - the science and farmer practice

A review of recently published science demonstrates that relatively simple non-perennial ryegrass mixtures have performed well in environments as diverse as under deer grazing in Dunedin and the Manawatu, under sheep grazing in dryland mid-Canterbury, and under both irrigated and dryland dairy cow grazing in the Waikato and Northland. Animal productivity has been lifted by up to 30% in milk solids and 50% in deer liveweight gain in non-perennial ryegrass mixtures compared to perennial ryegrass-based pastures. In some cases, the ryegrass pasture has produced similar or more dry matter, yet animal performance has been greater on the non-perennial ryegrass pastures. In other cases, dry matter productivity from complex nonryegrass mixtures has been around 30% higher than from perennial ryegrass pastures. Interviews with farmers from South Canterbury to Northland have all reported positive experiences with non-ryegrass pastures and most have said they will not be planting perennial ryegrass-based pastures again.

Desenvolvimento de bezerros de corte desmamados aos 80 ou 152 dias até os 15-16 meses de idade

Avaliou-se o desenvolvimento de bezerros de corte submetidos a duas idades de desmame: precoce, em média com 80 dias de idade; convencional, em média com 152 dias de idade. Foram utilizados 105 bezerros Braford, nascidos nos anos de 2004 e 2005. Após o desmame, os bezerros foram mantidos em pastagens cultivadas de milheto (Pennisetum americanum) no primeiro e segundo verão e, no inverno/primavera, de aveia e azevém (Avena strigosa Schreb + Lolium multiflorum Lam). Foram avaliados os pesos corporais, ganhos de pesos médios diários e condição corporal. Houve interação significativa entre idade de desmame e ano para o ganho médio diário, tanto no desmame precoce como no desmame convencional, na pastagem de aveia e na de azevém. No período entre as duas idades de desmame, o ganho médio diário no desmame precoce foi maior em 2004 que em 2005 (0,499 vs 0,468 kg, respectivamente) e no desmame precoce ocorreu maior ganho médio diário em 2005 (0,493 vs 0,631 kg, respectivamente). Na pastagem de aveia e azevém, o ganho médio diário dos animais do desmame precoce em 2004 (0,666 kg) foi menor que em 2005 (0,760 kg), no entanto, não houve diferença entre os anos no caso dos animais do desmame convencional (0,720 e 0,723 kg, respectivamente). Durante os segundos verões, não houve diferença no ganho médio diário dos animais entre os desmames precoce e convencional. O peso dos animais do desmame precoce (158,2 kg) foi superior ao daqueles do desmame convencional (147,7 kg) no início da pastagem de inverno, porém, não diferiu no final. Ao final do verão, quando os novilhos atingiram 15-16 meses de idade, o peso corporal foi similar entre os desmames precoce (340,1 kg e 4,14 pontos) e convencional (332,8 kg e 4,15 pontos). A condição corporal final em 2004 foi maior (4,34) que em 2005 (3,96 pontos). Bezerros desmamados aos 80 dias de idade e alimentados adequadamente têm desempenho semelhante aos desmamados aos 152 dias de idade, atingindo desenvolvimento e acabamento adequados de abate para mercados específicos aos 15-16 meses de idade.

Fluctuations in the concentration of ergovaline and lolitrem B produced by the wild-type endophyte (Neotyphodium lolii) in perennial ryegrass (Lolium perenne) pasture

Mammalian toxins produced by the wild-type endophyte, Neotyphodium lolii, in perennial ryegrass (PRG) pasture cause production losses and animal health and welfare problems in livestock. Managing this risk is limited by the lack of information on fluctuations in the concentration of toxin in Australian pasture. We investigated how the toxin concentrations may be related to recent observations of weather. Swards sown from common seedlots of two cultivars of wild endophyte-infected PRG, grazed short by sheep, were sampled at 2–4 weekly intervals from spring to autumn at two sites in Victoria. The highest concentration of ergovaline and lolitrem B was observed at Hamilton, the site with the longer-growing season. The concentration of ergovaline peaked in early summer, coinciding with seed development, and declined through summer, before increasing with the commencement of autumn growth. The concentration of lolitrem B remained low in summer, then rose in autumn. Variation between the two cultivars in the concentration of toxins was small and rarely significant. The concentration of ergovaline declined as the mean daily maximum temperature over the preceding 1–5 days increased. Similarly, for lolitrem B, the concentration declined over the temperature range 12−20°C, from 1.3 to 0.3 mg/kg. At Hamilton, where solar radiation and soil temperature were recorded, both were superior to maximum temperature for predicting lolitrem B. Serial sampling of PRG from old naturalised pasture on seven farms across south-eastern Australia found two seasonal peaks for both alkaloids in most pastures. The concentration of ergovaline reached or exceeded tolerance levels for livestock in 23 of 43 samples, compared with 5 of 43 for lolitrem B. Ergovaline concentrations initially peaked (at 1.0–1.6 mg/kg) when mature reproductive material was present (coinciding with peduncle elongation and seed development). In pastures with low grazing pressure, i.e. where growth was allowed to continue through summer, ergovaline concentration was relatively low (<0.7 mg/kg) but in a hard-grazed pasture (sward height 3 cm), the ergovaline concentration was greater (up to 1.1 mg/kg). Concentration of lolitrem B also peaked in December, except on pasture where growth continued through summer. High concentrations of lolitrem B associated with neurotoxic signs in sheep (viz. 2.4–3.9 mg/kg) were observed only in mid-summer and autumn, and only if conditions favoured growth or where close grazing by sheep left the crown as the dominant source of herbage.

Feed conversion efficiency and marginal milk production responses of pasture-fed dairy cows offered supplementary grain during an extended lactation

A study was conducted to quantify the feed conversion efficiency (FCE) and marginal milk responses of pasture-fed cows offered supplementary grain during an extended lactation of 670 days. The experiment used three groups of 10 Holstein cows in four experimental periods of 4 weeks, beginning when cows were ~60, 240, 420 and 530 days in milk (DIM). In each experimental period, cows were individually fed diets of either freshly cut perennial ryegrass pasture supplemented with triticale (60 and 420 DIM), or pasture silage and lucerne hay supplemented with wheat (240 and 530 DIM). On each occasion, one of the three groups was offered additional grain at 0.0, 2.5 or 5.0 kg DM/cow.day. Milk production was measured daily and concentrations of milk fat and protein weekly. These data were used to calculate FCE and marginal responses of milk, energy-corrected milk and milk solids (fat + protein). Results showed FCE was highest at 60 DIM and lowest at 530 DIM. Increased DM intake because of increased grain intake led to increased FCE at 240 and 530 DIM when the energy concentration of forage was lowest. Marginal milk responses were not different at any stage of lactation. For milk solids and energy-corrected milk, responses at 240 DIM were the same as at 530 DIM, but greater than at 60 DIM and 420 DIM. This study provides the first Australian data about FCE and marginal milk production responses to grain supplementation of pasture-fed cows undergoing an extended lactation. The results should provide farmers with confidence that good responses to grain can be achieved even in the latter part of a 22-month lactation.

Rumen‐Undegradable Protein Supplementation Effects on Early Weaned Calves Grazing Annual Ryegrass

Early weaned beef calves (Bos spp.) can be raised on cool‐season pastures in Florida but more information on protein supplementation is necessary to optimize the performance of those calves. The objective of this study was to evaluate the effects of three levels of rumen‐undegradable protein (RUP) supplementation on performance of early weaned calves grazing annual ryegrass (Lolium multiflorum Lam.) pastures. The study was conducted in Ona, FL in 2007 and 2008. Treatments were 1.5 g kg−1 body weight (BW) supplementation of three levels of supplemental RUP, soybean meal (SBM, 350 g kg−1 RUP), Soyplus (SP, 600 g kg−1 RUP, modified expeller soybean meal, West Central, Ralston, IA), or a 50:50 mixture of soybean meal‐Soyplus (SBMSP, 475 g kg−1 RUP). Pasture size was 0.3 ha and four early weaned calves were assigned to each pasture. There was a linear increase in herbage mass (HM, from 1.9–2.1 Mg ha−1) and herbage allowance (HA, from 1.1–1.4 kg dry matter [DM] kg−1 live weight, LW) with increasing levels of RUP. Increased RUP supplementation decreased forage dry matter intake (FDMI) and total dry matter intake (TDMI) in 2008 but there was no effect in 2007. There was no difference in average daily gain (ADG, 0.76 kg d−1) among treatments. Increasing the levels of RUP supplementation has potential to increase stocking rates of early weaned calves grazing annual ryegrass pastures.

Short communication: Feeding station behavior of grazing dairy cows in response to restriction of time at pasture

The short-term behavioral adaptation of cattle to time restrictions at pasture is poorly understood. This research explored the FS behavior of dairy cows during the first grazing session of the day (0800–1200h) in response to daily restriction of time at pasture. Six groups of 8 multiparous Holstein–Friesian cows (470±47kg, 35±9days in milk) were strip-grazed on a perennial ryegrass (Lolium perenne L.) pasture for either 4h after each milking (2×4), one period of 8h between milkings (1×8), or 24h excluding milking times (control, CTL). Daily herbage allowance was 0.07kg DM/kg live weight/day for all treatments. Cows were not fed supplements. Six cows per group were equipped with IceTag 3D motion sensors and GPS collars to measure the total distance walked, and the number of FS per min, and to allow calculation of the step length while eating. Bite rate (bites/min) and eating time (min) were determined for these cows. Bites per FS, velocity of walking while eating (m/min), total number of FS, total distance walked while eating (m), and area explored while eating (area of FS×total number of FS) were calculated. The velocity of walking while eating and the number of FS per min were also determined at 4 fixed times during such a grazing session. No difference in the number of FS per min and bites per FS was found between treatments, although cows in 1×8 had the greatest velocity of walking while eating for the first 200min of the grazing session. Eating step length, velocity of walking while eating, total number of FS, distance walked while eating and area explored while eating were the greatest for cows in 1×8. Cows in CTL showed the lowest values for the total number of FS. The results of this experiment demonstrated that dairy cows reacted to restrictions of time at pasture mainly by changing locomotion behavior (step length, velocity of walking while eating, and distance walked while eating), which led to considerable changes in the area explored while eating. This study of foraging behavior contributes to the understanding of eating and locomotion behavior of dairy cows in response to restrictions of time at pasture.

Argentine stem weevil (Listronotus bonariensis, Coleoptera: Curculionidae) population dynamics in Canterbury, New Zealand dryland pasture

The Argentine stem weevil (Listronotus bonariensis) was an economically important pest in New Zealand pastures until the release of the parasitoid Microctonus hyperodae. This contribution uses historical data to investigate the regulation of the pest populations prior to, and somewhat during, the establishment of this parasitoid in dryland Canterbury, New Zealand. Thus, a significant goal of this study is to provide an L. bonariensis population dynamics baseline for any future work that aims to analyse the full effects of M. hyperodae on the weevil, now that equilibrium with the weevil host has been reached.The population dynamics of L. bonariensis, based on a life-table approach, were investigated using data collected regularly for eight years from populations in Canterbury, New Zealand. The key factor affecting end-of-season L. bonariensis density was found to be variation in second generation fourth instar prepupal and pupal mortality. This may have been caused by arrested development and ongoing mortality resulting from the onset of cooler autumnal conditions.A compensatory response was found in recruitment to the second summer weevil generation, whereby the realised fecundity of the emergent first summer generation of weevils was found to be negatively related to the density of adult weevils per ryegrass tiller. This is the first time that this has been found via long-term population analysis of L. bonariensis, although indications of this have been found elsewhere in caging, pot and small plot experiments.In this study, the effect of the parasitoid biocontrol agent Microctonus hyperodae on L. bonariensis population dynamics was unclear, as the analysis covered a period when the parasitoid Microctonus hyperodae was introduced and still establishing. It does, however, raise important questions for future analysis in terms of the interaction between parasitism and unrealised fecundity.The results in this contribution also highlighted regional differences. Overwintering mortality of adult weevils in Canterbury was constant between years, whilst earlier studies in the North Island Waikato region indicated this mortality was density dependent. In addition, the availability of tillers in endophyte-free ryegrass pastures in Canterbury had no influence on egg and early-instar larval survival, which contrasts with the finding from endophytic Waikato pastures.

Recria de bezerras de corte em pastagem de azevém sob frequências de suplementação

Foi avaliado, em pastagem de azevém (Lolium multiflorum Lam), o desempenho de bezerras de corte em diferentes frequências de suplementação: pastagem exclusiva de azevém, recebendo suplemento sete ou cinco dias por semana (de segunda à sexta-feira). A quantidade semanal de suplemento (17% PB; 71% NDT) foi similar para as novilhas suplementadas diariamente e suplementadas cinco dias por semana. O método de pastejo foi contínuo, com taxa de lotação variável em delineamento inteiramente casualizado com três tratamentos e duas repetições de área. O fornecimento de suplemento aos animais em pastejo, independentemente da frequência, aumenta a taxa de lotação. O ganho médio diário, o escore de condição corporal e o ganho de peso por área foram similares para as estratégias de suplementação. A redução na frequência de suplementação não exerce efeito negativo no desempenho de terneiras de corte e pode ser uma opção no manejo alimentar do rebanho.

A high dose of monensin does not reduce methane emissions of dairy cows offered pasture supplemented with grain

The primary objective of our research was to determine the effect of a high dose of monensin supplementation on enteric CH4 emissions of dairy cows offered a ryegrass pasture diet supplemented with grain. An additional objective was to evaluate effects on milk production and rumen function, because a commensurate improvement in milk production could lead to adoption of monensin as a profitable strategy for methane abatement. Two experiments were conducted (grazing and respiratory chambers) and in both experiments monensin (471mg/d) was topdressed on 4kg (dry matter)/d of rolled barley grain offered in a feed trough twice daily at milking times. In the grazing experiment, 50 Holstein-Friesian cows were assigned randomly to 1 of 2 groups (control or monensin). Cows grazed together as a single herd on a predominantly ryegrass sward and received monensin over a 12-wk period, during which time measurements of milk production and body weight change were made. The SF6 tracer technique was used to estimate methane production of 30 of the 50 cows (15 control cows and 15 monensin cows) for 3 consecutive days in wk 3, 5, 8, and 12 of treatment. Samples of rumen fluid were collected per fistula from 8 of the 50 cows (4 per diet) on 2 consecutive days in wk 3, 5, 8, and 12 of treatment and analyzed for volatile fatty acids and ammonia-N. In the metabolic chamber experiment, 10 pairs of lactating dairy cows (control and monensin) were used to determine the effects of monensin on methane emissions, dry matter intake, milk production, and body weight change over a 10-wk period. Methane emissions were measured by placing cows in respiration chambers for 2 d at wk 5 and 10 of treatment. Cows received fresh ryegrass pasture harvested daily. Monensin did not affect methane production in either the grazing experiment (g/d, g/kg of milk) or the chamber experiment (g/d, g/kg of dry matter intake, g/kg of milk). In both experiments, milk production did not increase with addition of monensin to the diet. Monensin had no effect on body weight changes in either experiment. Monensin did not affect volatile fatty acids or ammonia-N in rumen fluid, but the acetate to propionate ratio tended to decrease. Monensin did not improve milk production of grazing dairy cows and no effect on enteric methane emissions was observed, indicating that monensin cannot be promoted as a viable mitigation strategy for dairy cows grazing ryegrass pasture supplemented with grain.

Desenvolvimento de bezerras de corte após a desmama sob níveis de concentrado

Foi avaliado o desenvolvimento de bezerras de corte recebendo diferentes níveis diários de suplemento concentrado: 0,0; 0,3; 0,6 e 0,9% do peso corporal em pastagem de aveia preta (Avena strigosa Schreb.) e azevém (Lolium multiflorum Lam.). O delineamento experimental foi o inteiramente casualizado, com quatro tratamentos e duas repetições de área. As bezerras tiveram condições similares de disponibilidade de pasto (massa de forragem e oferta de lâminas verdes) em todos os tratamentos. Aumentos na quantidade fornecida de suplemento interferiram positivamente no ganho médio diário, na carga animal, no ganho de peso por área e na eficiência de transformação da forragem. Bezerras suplementadas apresentaram maior peso corporal e maior escore de condição corporal aos 13 meses de idade em relação às não suplementadas. Em aveia preta e azevém, fornecer até 0,9% do peso corporal dos animais em suplementação concentrada é uma alternativa para serem obtidas novilhas mais pesadas e com melhor escore de condição corporal.

Intervalo hídrico ótimo de um latossolo vermelho distroférrico sob plantio direto em sistema de integração lavoura-pecuária

O intervalo hídrico ótimo (IHO) é considerado um moderno indicador da qualidade física do solo para o crescimento e desenvolvimento das plantas. O objetivo deste estudo foi determinar o IHO para avaliar a qualidade física de um Latossolo Vermelho distroférrico sob plantio direto em sistema de integração lavoura-pecuária. A área de estudo é constituída de um sistema de integração lavoura-pecuária com cultivo de soja no verão e aveia (Avena strigosa Schreb) + azevém (Lolium multiflorum Lam) no inverno, manejado com diferentes alturas de pastejo: 7, 14, 21 e 28 cm de altura e testemunha sem pastejo. Foram retiradas amostras indeformadas nas camadas de 0-7,5 e 7,5-15 cm, nas quais foram determinadas a densidade do solo (Ds), as curvas de retenção de água e de resistência do solo à penetração e estimado o IHO. A densidade do solo crítica (Dsc) foi tomada como aquela em que o IHO = 0. Independentemente dos tratamentos, foi constatado que com o aumento da densidade do solo são necessários maiores teores de água para que a resistência do solo à penetração não seja maior que 2,5 MPa, bem como menores teores de água, para que a aeração do solo não se torne limitante. Nos tratamentos com 21 e 28 cm de altura de pastejo, verificou-se maior amplitude do IHO em relação à testemunha, sugerindo que a integração lavoura-pecuária cria um ambiente físico positivo no solo, desde que se mantenha uma carga animal adequada para evitar o sobrepastejo das áreas. No tratamento com 7 cm, a degradação física do solo é muita elevada na camada superficial e certamente predispõe as culturas a estresses de resistência sob secamento do solo e de aeração com elevados teores de água sob períodos prolongados. Verificou-se redução progressiva da proporção de amostras com valores de Ds > Dsc do tratamento com 7 cm para a testemunha, indicando que o pisoteio excessivo dos animais resulta numa perda da qualidade física do solo na camada de 0-7,5 cm do tratamento com 7 cm. Para manter qualidade física do solo adequada sob pastejo de aveia e azevém no inverno, na camada de 0-7,5 cm, a altura de pastejo deve ser mantida acima de 21 cm da superfície do solo.

Característica produtiva e estrutural de pastos mistos de aveia e azevém manejados em quatro alturas sob lotação contínua

Monitoraram-se variáveis relacionadas à produção e à estrutura de pastos de aveia-preta (Avena strigosa, Schreb) e azevém (Lolium multiflorum, Lam) manejados em quatro alturas (10, 20, 30 e 40 cm), em pastejo contínuo com lotação variável (put and take). Utilizaram-se novilhos de corte mestiços de aproximadamente 10 meses de idade com peso médio inicial de 190 kg, em delineamento de blocos completos casualizados com três repetições. Investigou-se o tipo de distribuição das frequências de altura em seis datas, bem como o potencial de predição da massa seca de forragem por meio da altura do pasto. A massa de forragem aumentou de forma linear de acordo com a altura do pasto: cada 1 cm de aumento na altura acima de 10 cm correspondeu a um acréscimo de cerca de 107 kg de MS/ha na massa de forragem. Não houve efeito da altura do pasto na taxa de acúmulo (55,8 kg de MS/ha.dia) nem na produção total de matéria seca (8.210 kg de MS/ha). A distribuição das frequências ajustou ao modelo normal em apenas uma das 96 séries analisadas. A distribuição tipo Gamma foi a que mais frequentemente se ajustou aos dados de altura do pasto, porém, uma vez iniciado o pastejo, a heterogeneidade no pasto foi tão alta que a distribuição das alturas não se ajustou a nenhum dos modelos estudados. É possível estimar a massa seca de forragem existente no pasto por meio de sua altura média, assim, sugere-se estabelecer alturas variáveis ao longo do ciclo de pastejo, com o intuito de se administrar a heterogeneidade causada pelo animal.

Surto de polioencefalomalacia por ingestão excessiva de enxofre na dieta em bezerros no Rio Grande do Sul

Neste trabalho descreve-se surto de polioencefalomalacia em bovinos decorrente da ingestão de dieta com excessiva concentração de enxofre em uma propriedade no Rio Grande do Sul. O lote era composto por 30 bezerros, mantidos em um piquete com azevém (Lolium multiflorum) e suplementados com ração e sal mineral. Seis bezerros morreram e dois deles foram necropsiados; amostras de tecido hepático para dosagem de chumbo e fragmentos do sistema nervoso central para histopatológico foram colhidos. Um dos bezerros foi examinado antes da morte e sinais neurológicos encefálicos foram constatados. Foi estabelecido o teor de enxofre nos componentes da dieta e água, a produção de sulfeto de hidrogênio ruminal em cinco bovinos do mesmo lote e realizada PCR de um bloco de parafina para detecção de DNA do herpevirus bovino tipo 5. O consumo total de enxofre foi de 0,38% da matéria seca fornecida aos animais e as dosagens de sulfeto de hidrogênio ruminal em animais do mesmo lote variaram de 1.000 a 2.500ppm. Os achados histopatológicos indicaram necrose laminar do córtex cerebral. Não foi detectado chumbo na amostra de tecido hepático e não foi identificado DNA do herpesvirus bovino tipo 5 no encéfalo. O quadro clínico de síndrome cerebrocortical associado aos elevados valores do sulfeto de hidrogênio ruminal, alta ingestão de enxofre na dieta e os achados histopatológicos permitem estabelecer o excesso de enxofre como causador da polioencefalomalacia.

Produção de cordeiros em pastejo contínuo de azevém anual submetido à adubação nitrogenada

Neste trabalho, avaliou-se o efeito da adubação nitrogenada do pasto de azevém (Lolium multiflorum Lam.) sobre a produção de cordeiros de corte mantidos em pastejo contínuo. O pasto foi implantado em plantio direto, em área de integração lavoura-pecuária. A adubação de fundação foi realizada com 60kg P2O5 ha-1 e 60kg K²O ha-1. Os tratamentos corresponderam às doses 0; 75; 150 e 225kg de N ha-1, na forma de ureia (45% de N), em cobertura, 35 dias após o plantio. O período de avaliação foi de 84 dias. A oferta de forragem foi influenciada de forma quadrática pelas doses de N, com menor disponibilidade para 182,75kg de N ha-1; no entanto, a oferta de lâminas foliares não foi influenciada pelas doses de N (3,8kg de massa de forragem de folhas/100kg de PV), nem o ganho de peso médio diário, com média 0,133kg de PV an-1 dia-1. Para carga animal e ganho de peso por área as doses de N proporcionaram aumento de 3,0kg de PV ha-1 e 1,1kg de PV ha-1, respectivamente por kg de N aplicado. A adubação nitrogenada proporcionou aumentos na carga animal, o que resulta no aumento de kg de carne produzidos nesse sistema.

Composição tecidual da carcaça e perfil de ácidos graxos da carne de cordeiros terminados a pasto ou em confinamento

Objetivou-se avaliar a composição tecidual do lombo e do pernil e o perfil de ácidos graxos da carne de cordeiros em quatro sistemas de terminação: 1) cordeiros desmamados com média de 40 dias e mantidos em pasto de azevém até o abate; 2) cordeiros com suas mães na mesma pastagem até o abate; 3) idem ao 2), porém com suplementação diária a 1% do PV em creep feeding; 4) cordeiros desmamados aos 40 dias e confinados, recebendo silagem de milho e concentrado ad libitum. O delineamento experimental foi inteiramente casualizado com quatro sistemas de terminação e três repetições. Os cordeiros foram abatidos com 32 kg de peso vivo. Os lombos e pernis direitos foram utilizados para determinação da composição tecidual e os lombos esquerdos, para análise do perfil de ácidos graxos. No lombo esquerdo foram mensurados: comprimento e profundidade máxima do músculo; espessura mínima e máxima de gordura de cobertura e área de olho-de-lombo. Os cordeiros desmamados terminados a pasto apresentaram menor deposição de gordura na carcaça e índice de musculosidade do pernil. O desenvolvimento muscular e a deposição de gordura nos cordeiros terminados ao pé da mãe, com ou sem suplementação, foram semelhantes aos observados nos cordeiros desmamados e terminados em confinamento. Cordeiros em creep feeding apresentaram mais ácidos graxos na carne que cordeiros desmamados a pasto. Os sistemas de terminação influenciam a composição tecidual, mas não afetam o perfil de ácidos graxos da carne para consumo humano.

A comparison between Holstein-Friesian and Jersey dairy cows and their F1 hybrid on milk fatty acid composition under grazing conditions

The objective of this study was to investigate the effect of 2 breeds, Holstein and Jersey, and their F1 hybrid (Jersey × Holstein) on milk fatty acid (FA) concentrations under grazing conditions, especially conjugated linoleic acid (CLA) and n-3 polyunsaturated fatty acids because of their importance to human health. Eighty-one cows (27 per breed grouping) were allocated a predominantly perennial ryegrass pasture. Samples were collected over 2 periods (June and July). Breed affected dry matter intake and milk production and composition. Holstein cows had the highest dry matter intake (18.4±0.40kg of DM/d) and milk production (21.1±0.53kg of DM/d). Holstein and Jersey × Holstein cows had similar 4% fat corrected milk, fat yield, and protein yield; with the exception of fat yield, these were all higher than for Jersey cows. Milk fat concentration was highest for Jersey cows and lowest for Holstein cows, with the hybrid cows intermediate. Total FA and linolenic acid intake (1.09±0.023 and 0.58±0.012 kg/d, respectively) were highest for Holstein cows. In terms of milk FA, Holstein cows had higher contents of C14:1, cis-9 C18:1 and linoleic acid. In turn, Jersey and Jersey × Holstein cows had higher content of C16:0. Milk concentrations of neither the cis-9,trans-11 isomer of CLA nor its precursor, vaccenic acid, were affected by breed. Nevertheless, large variation between individual animals within breed grouping was observed for CLA and estimated Δ9-desaturase activity. There was some evidence for a negative heterotic effect on milk concentration of CLA, with the F1 hybrid cows having lower concentrations compared with the mid parent average. Plasma FA profile did not accurately reflect differences in milk FA composition. In conclusion, there was little evidence for either breed or beneficial heterotic effects on milk FA content with human health-promoting potential, though significant within-breed, interanimal variation was observed.

Desempenho de cordeiras em pastagens de azevém e de milheto sob suplementação

Avaliou-se o desempenho de cordeiras em pastagens de azevém (Lolium multiflorum Lam.) e de milheto (Pennisetum americanum L. Leeke) como alimento exclusivo ou com suplementação diária com ração comercial na proporção de 0,5; 1,0 e 1,5% do peso corporal (PC). O método de pastejo utilizado foi o de lotação contínua com taxa de lotação variável. As cordeiras em pastagem de azevém com suplementação nos níveis de 0,5 e 1,5% do PC apresentaram maior ganho médio diário. Independentemente do nível, a suplementação em pastagem de azevém promoveu o maior ganho de peso por área. Na pastagem de milheto, o ganho médio diário, o ganho de peso por área e o escore de condição corporal foram maiores nas cordeiras sob suplementação. A estrutura de pastagens de azevém e de milheto não é influenciada pela oferta de suplemento aos animais. A utilização da pastagem de azevém nos períodos pré e pós-desmama, associada à suplementação nos níveis de 0,5 a 1,5% do peso vivo em pastagem de milheto, permite que cordeiras apresentem peso e escore de condição corporal adequados para o acasalamento aos 9 meses de idade.

Effects of increasing days of exposure to prepartum diets on the concentration of certain blood metabolites in dairy cows

To evaluate the effect of the number of days exposure to a prepartum transition diet on mineral, energy and protein metabolism in dairy cows. A prospective cohort study. The prepartum transition diet consisted of ryegrass pasture, cereal hay, grain, grain by-product, protein meals, BioChlor, rumen modifiers, minerals and vitamins and contained 13.9% crude protein, 10.0 MJ metabolisable energy/kg and a dietary cation anion difference of -35 meq/kg dry matter. Forty cows were bled bi-weekly from their introduction to the prepartum transition diet until day 35 of lactation. Blood samples were submitted for estimation of a range of metabolites. Cubic smoothed splines were fitted to scatterplots of metabolite concentration as a function of day relative to calving and the area under the curve (AUC) was calculated. Linear regression modelling determined the effect of days exposed, age, body condition score (BSC) and calving day on AUC. Results The prepartum AUC of blood phosphorus and beta-hydroxybutyrate increased and the AUC of blood calcium and cholesterol decreased with increasing days exposed to the diet. The postpartum AUC of beta-hydroxybutyrate and non-esterified fatty acids decreased with increasing days exposed but increased with days exposed x age and days exposed x BCS, respectively. The AUC of other metabolites did not vary significantly with number of days exposed. Conclusions Increasing exposure to the prepartum diet significantly altered the AUC of blood metabolites associated with mineral, energy and protein metabolism in ways consistent with improvements in production and reproduction previously reported and the result suggests links between energy, protein and skeletal metabolism.

Componentes do processo de pastejo de cordeiros em azevém sob diferentes intensidades e métodos

The aim of this study was to evaluate the components of lamb grazing process in ryegrass pastures (Lolium multiflorum Lam.). The treatments were two grazing intensities: moderate and low (forage suply: 2.5 and 5-fold the animal intake potential, respectively) in rotational and continuous stocking. The experimental design was a randomized complete block arranged in a factorial with three replicates (2 intensities x 2 methods x 3 replicates). There was no interaction among grazing intensities and methods, and its effects were analyzed separately. There was no difference of herbage allowance between grazing methods (p= 0.3393), and so, the basic conditions to compare all treatments were reached. Herbage mass during the experiment were: 3159 and 2327 kg of DM/ha for rotational and continuous stocking; and 1971 and 3514 kg of DM/ha for moderate and low grazing intensities, respectively. There was no significant differences for number of meals (M), meal duration (MD), inter meals intervals (IMI), duration of intervals (DI), grazing time (GT), ruminating time (RT) and idling time (IT) (p>0.1) for grazing methods. There was no statistical difference for RT, M, MD and IMI (p>0.1) regarding grazing intensities. DI, GT, IT, bite rate (BR) and time for feeding station (TFS) were affected by grazing intensity (p<0.1). Grazing methods affected just BR and TFS (p<0.1) due to the higher herbage mass under rotational stocking. The use of correct grazing intensities for the animals, more than the choice between grazing methods, is capital to built sustainable grazing environments aiming the production of high quality lambs.

Effects of increasing days of exposure to prepartum transition diets on reproduction and health in dairy cows

To evaluate the effect of the number of days exposure to a prepartum transition diet on reproduction and health in dairy cows. A prospective cohort study. We enrolled 1008 dairy cows from three herds to examine the effects on reproduction and health of increased days exposure to prepartum transition diets that included ryegrass pasture, ryegrass silage, cereal hay, grain, by-products, oilseed meals, BioChlor, rumen modifiers, minerals and vitamins. Diets provided 9.9 MJ metabolisable energy per kg dry matter (DM), a metabolisable protein balance of 286 g/day and a dietary cation anion difference of -150 meq/kg DM. Statistical models controlled for herd, calving day, age and gestation period. In two of the three herds increased days exposure to prepartum transition diets increased the hazards of submission for breeding, conception and clinical mastitis, and decreased the hazard of cow removal. The odds of pregnancy by 6 and 21 weeks after the mating start date tended to increase with increasing days of exposure to prepartum transition diets. Increasing exposure to a prepartum transition diet improved the calving to conception interval, tended to improve the odds of pregnancy and reduced the risk of culling of cattle, but increased the hazard of clinical mastitis.