Nutritional management to optimize fertility of dairy cows in pasture-based systems

Abstract

The efficiency of milk production in pasture-based systems is heavily influenced by calving pattern, necessitating excellent reproductive performance in a short-breeding season. Where grazed pasture is the major component of the diet, cows are underfed relative to their intake potential. The cow responds by reducing milk output, but fertility is generally better than high intake confinement systems that achieve greater milk production per cow. A number of studies have identified body condition score (BCS) measurements that are related to likelihood of both submission and conception. Blood metabolites and metabolic hormones linked to fertility outcomes are now well characterized. In general, fertility variables have favourable associations with circulating concentrations of glucose, insulin and IGF-1 and unfavourable associations with non-esterified fatty acids, β-hydroxybutyrate and endogenous growth hormone. Nutritional strategies to impact these metabolic indicators have been utilized, but effects on herd fertility are inconsistent. Simply supplementing cows with additional energy in the form of standard concentrates does not appear to have a pronounced effect on fertility. Energy from additional concentrates fed during lactation is preferentially partitioned towards extra milk production rather than BCS repletion. The higher the genetic merit for milk production, the greater the partitioning of additional nutrients to the mammary gland. This review outlines the unique nutritional challenges of pasture-based systems, the role of specific metabolic hormones and metabolites in regulating reproductive function, and nutritional strategies to improve herd fertility.Keywords: Nutrition, fertility, dairy cow, pasture ImplicationsAchieving the appropriate body condition score (BCS) at parturition and minimizing BCS loss are the overarching goals of nutritional management in pasture-based system. A large number of systems studies have demonstrated that simply adding more concentrate will not result in improved fertility. Future research needs to identify specific micro-and macro-nutrients that can stimulate components of the reproductive axis. IntroductionThe effects of inadequate nutrition in cattle include delayed puberty Archbold et al., 2012), prolonged postpartum anovulation (Rhodes et al., 2003), reduced body condition score (BCS) , and poor submission and conception rates (Buckley et al., 2003). Dairy production systems based on grazed pasture are primarily located in countries where environmental conditions support long growing seasons. The nutritional management of dairy cows in pasture-based systems is most heavily influenced by the stocking rate on the farm (McCarthy et al., 2011). As stocking rate increases, an individual cow is less likely to be able to reach her dry matter intake (DMI) potential, simply as a consequence of more cows trying to graze a finite amount of available grass. The cow responds by reducing milk yield, but the total milk produced on the farm increases because more cows are being milk...

Forty research issues for the redesign of animal production systems in the 21st century

“…In dairy cows, simply adding more concentrate or reducing stocking rate will not result in improved fertility. Future research needs to identify specific micro-and macro-nutrients that can stimulate reproduction (Butler, 2014). In addition, the use of exogenous hormones has meant that adaptive traits such as estrus expression have been neglected in industrial farming systems.…”

Avances sobre nutrición y fertilidad en ganado lechero: Revisión

“…En este escenario, el manejo nutricional de las vacas a pastoreo se va a ver influenciado principalmente por la carga animal. El desafío es lograr la carga animal óptima que logre la mayor producción por vaca y por hectárea, sin afectar los procesos reproductivos, la salud y el bienestar de las vacas (11,12) . La evaluación de los sistemas productivos se debe basar más en los sólidos (kilogramos) que los litros de leche producidos (litros o kilogramos), ya que la adición de agua a la leche tiene un costo adicional.…”

“…Por ejemplo, una vaca que produce 500 kg de grasa en un volumen de 5,000 kg de leche, va a ser más eficiente que una vaca que produce la misma cantidad de grasa en 7,500 kg de leche. Esto es debido a que la segunda vaca requiere sintetizar 120 kg adicionales de lactosa (2,500 kg de leche x 48 g de lactosa) (12) . Debido a que la disponibilidad y el valor nutritivo de la pradera varía a través del año, el manejo reproductivo de la vaca lechera se deberá acomodar a las características de crecimiento y calidad de la pradera a través del año (13) .…”

“…Para lograr el objetivo planteado se debe lograr que: (i) todas las vacas hayan parido antes de iniciarse la época de servicio; (ii) ≥70 % de las vacas estén ciclando al inicio del servicio; (iii) ≥90 % de las vacas deberían entrar en un programa de IA a tiempo fijo (IATF) en los primeros 21 días del periodo de servicio; (iv) la TP para las primeras seis semanas debería ser ≥70 % y para las 12 semanas de ≥90 %; (v) la duración del servicio ≤12 semanas. Bajo este escenario, claramente las vacas deben recuperar prontamente su ciclicidad postparto y tener una alta probabilidad de establecer y mantener la preñez después de la monta o IA (12,15) .…”

Editorial: International Cow Fertility Conference ‘New Science – New Practices’ in Westport, Ireland, in 2014

“…In particular, pronounced NEB during the first 10 days to 2 weeks appears to be critical for later reproductive success. Butler (2014) outlines the unique nutritional challenges faced by pasture-based systems of milk production, particularly the challenge of achieving grass dry matter intakes to meet the combined demands of maintenance and genetic milk production. The roles of specific metabolic hormones and metabolites in regulating reproductive function and nutritional strategies to improve herd fertility are discussed.…”