Effects of body condition, food intake and temporary calf separation on the duration of the post-partum anoestrous period and associated LH, FSH and prolactin concentrations in beef cows

Abstract

An experiment was conducted to examine factors affecting the length of the post-partum anoestrous period and associated effects on LH, FSH and prolactin. Forty-six cows (24 Hereford × Friesian and 22 Blue-Grey) ranging in body condition score at calving from 1·50 to 2·75 were used. They were individually fed chopped barley straw and concentrate at either 50 (low) or 91 (high) MJ metabolizable energy per day from calving. At 34 days post partum half the cows were separated from their calves for 48 h. The duration of the post-partum anoestrous period was estimated from progesterone concentrations in thrice weekly blood samples. Blood samples were collected every 20 min for 10 h periods immediately prior to calf separation, during the last 10 h of calf separation and 1 week later. All samples were analysed for LH, and every third sample was analysed for FSH and prolactin.There were no significant effects of genotype, feeding level or calf separation on the length of the post-partum anoestrous period. There was a negative association between body condition score at calving and the length of the anoestrous period, with each unit increase in body condition score reducing the anoestrous period by 43 (s.e. 20) days. There was some evidence that feeding level affected the number of thin cows (body condition score ≤2·25 at calving) which were still acyclic at the end of the experiment, but not the number of fat cows (body condition score ≥2·5 at calving).FSH levels were not affected by any of the factors examined. Prolactin concentrations were higher in fatter cows, in cows on the higher level of feeding and in Blue-Grey cows. Prolactin concentrations decreased during the period of calf separation. Genotype and feeding level had no effect on LH concentration or LH pulse frequency. LH pulse frequency was increased (P < 0·05) during the period of calf separation, but there was no effect 1 week later. There was a significant positive relationship between LH puise frequency and body condition score at calving in two of the three sampling periods.It is suggested that the effect of body condition on the duration of the post-partum anoestrous period i s mediated through effects on LH pulse frequency.

Pre- and post-calving forage systems and reproductive performance of primiparous cows

“…Wright et al (1987) attribute a 43-day reduction in postcalving anoestrus for each point of increase in body condition score at calving.…”

Management factors associated to the duration of postpartum anoestrus interval in Brown Swiss and Pirenaica beef cows

“…El acceso libre del ternero a la madre se relacionó con reactivaciones ováricas medias y sobre todo largas, a pesar de que tanto antes como después del parto los animales tendieron a presentar ganancias de peso, como han observado otros autores (San Juan et al, 1994;Stagg et al, 1998). La mayoría de los trabajos realizados al respecto coinciden en señalar un aumento en la liberación pulsátil de LH después del destete del ternero (Whisnant et al, 1985;Rund et al, 1989), o de la restricción del acceso del ternero a la madre (Stagg et al, 1998;Diskin et al, 1999;Sanz et al, 2000), o de la separación del ternero durante 48 horas (Wright et al, 1987). Este trabajo corrobora que la restricción del acceso del ternero a la madre es una técnica sencilla y económi-ca, que facilitará que los animales reinicien la actividad reproductiva de forma temprana.…”

“…Se consideró que la actividad ovárica se iniciaba cuando se detectó la primera elevación de los valores reales de progesterona por encima de 0,5 ng/ml durante al menos dos días, o 1 ng/ml en un sólo día, concentraciones que reflejaban la existencia de actividad luteal y/o placentaria (Thimonier, 1978). En las vacas que no presentaron reactivación ovárica durante el periodo controlado se consideró como duración del APP el intervalo entre el parto y la última muestra de sangre recogida (Wright et al, 1987), coincidiendo con la duración de la lactación (140 y 170 días, para los partos de otoño y primavera, respectivamente).…”

“…Estas reservas corporales influyen de manera importante en la duración del anestro postparto (APP), tanto a través de los niveles de alimentación recibidos antes (Wiltbank et al, 1962;Ducrot et al, 1994) y después del parto (Rutter y Randel, 1984;Perry et al, 1991), como a través de sus interacciones . Los niveles bajos de energía y las pérdidas de estado corporal actuarían sobre la actividad reproductiva reduciendo la frecuencia de pulsos de LH (Wright et al, 1987).…”

Post-partum Anoestrus in Bali cattle under low-input animal production systems in Eastern Indonesia

“…A PPA period less than 85-100 days is required if cows are to have the opportunity to produce a calf each year (Peters & Lamming 1986;Wright et al 1987 Nutrition is the key limitation to reproduction as differences in nutritional status of animals across the various sites involved with this study were observed as reflected in the differences in BCS. The main feed types used by farmers are rice straw, native grass, elephant grass, Sesbania, Gliricidia and peanut straw.…”