Reducing post-partum anoestrous interval in first-calf Bos indicus crossbred beef heifers. III. Effect of nutrition on responses to weaning and associated variation in metabolic hormone levels

Abstract

Interactions between effects of undernutrition and weaning on the duration of post-partum anoestrus and associated variation in milk yield, suckling behaviour, and metabolic hormone levels in Droughtmaster [Bos indicus x Bos taurus (518, 3/8)] first-calf cows were studied in 2 successive years. Low body condition score at calving (3.5f 0.1, scale 1-9) was associated with prolonged post-partum anoestrous intervals in suckled cows, but provided cows were maintaining liveweight, ovarian cyclicity resumed within 50 days if calves were weaned 70 days post-partum. This response to weaning was totally inhibited in cows that calved in low body condition that lost liveweight post-partum (Year 1). In contrast, marked levels of post-partum liveweight loss (23%) did not affect resumption of ovarian cyclicity in response to weaning (at 50 days post-parturn), or time to conception, among cows that calved with high body condition scores (5.8 � 0.2, Year 2). Reduced milk yields and calf weight gains among underfed cows were associated with higher suckling frequencies and durations ( P < 0.05). Acyclic interval after weaning was negatively related to body condition score at weaning (P < 0.01), and positively related to preweaning suckling intensity (P < 0.01). The time taken to resume ovarian cyclicity after weaning increased by a factor of 1.2 for every half unit decrease in body condition score at weaning, and by a factor of 1.3 for every 30-min increase in time suckled per day prior to weaning. Within level of nutrition, higher frequencies and durations of suckling were associated with higher plasma prolactin levels. Plasma IGF-1 levels were consistently depressed in underfed cows, whereas plasma insulin and GH levels were less affected by nutritional treatments. Effects of undernutrition in suckled cows appear to operate at least partly through interactions with milk yield and suckling intensity. Management of post-partum anoestrus in Bos indicus cows should focus on the conservation of cow body condition and on the strategic use of early weaning.

Risk factors affecting the reproductive outcome of beef breeding herds in North Australia

“…As BCS measured at the branding/weaning muster increased, the expected occurrence of non-pregnancy progressively declined with diminishing reductions predicted between BCS categories. These findings are consistent with numerous other studies where curvilinear or linear relationships between improvement in body condition and positive responses in fertility have been demonstrated (Rae et al 1993;Jolly et al 1996;Dixon 1998;Wettemann et al 2003;Schatz and Hearnden 2008). In the present study, relative to the odds of non-pregnancy at BCS 3 measured at the branding/weaning muster, the odds of non-pregnancy were 2.3 times greater at BCS 2.5 and 4.1 times greater at BCS ≤2.0 and are very similar to those reported by Waldner and García Guerra (2013) who using a multivariable model that included other risk factors including cow age, cow breed type, exposure to a single bull, duration of bull exposure during the breeding season, and month of pregnancy testing reported odds ratios of 1.3-1.8 at BCS 2.5 and 3.5-4.2 at BCS 2.0 when referenced to BCS 3.0 measured at the pregnancy diagnosis muster.…”

“…Curvilinear and linear relationships between improvement in body condition or liveweight and positive responses in fertility have been demonstrated by numerous research studies (Rae et al 1993;Jolly et al 1996;Dixon 1998;Wettemann et al 2003;Schatz and Hearnden 2008). However an identified limitation of the literature, for northern Australia beef cattle particularly, was that few studies have quantified the effect of BCS on reproductive performance after accounting for other known factors associated with reproductive performance.…”

Relationship of blood metabolites with reproductive cyclicity in dairy cows

“…When cows are weaned, even if temporarily, glucose availability increases along with serum IGF-1 and a return to reproductive cyclicity (Randel, 1990;Jolly et al, 1996). Lowest serum glucose level (35.74 ± 1.57 mg/dl) and increased triglyceride level (19.17 ± 0.84 mg/dl) were observed in anestrous cows which is in strong agreement to Sathish and Sharma (1991) who noticed a lower blood glucose in non fertile animals which is an indication of subnormal energy status of cows.…”

Effect of a feed supplementation during the mid-lactating period on body condition, milk yield, metabolic profile and pregnancy rate of grazing dual-purpose cows in the Mexican humid tropic

“…In the present study, BCS of the cows was low. Cows with low BCS are very common among grazing crossbred cattle raised in tropical regions, since they receive no FS (Jolly et al 1996, Montiel 2001. The absence of changes in BCS before and after the FS period might suggest that dietary energy shortages were not great.…”