Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

16 t h International Congress on Animal Reproduction
Workshop Abstracts 13
other reports, a high percentage of cows suffered from delayed
ovarian function: only 60.9% of the cows ovulated within the first 42
days pp. Survival analysis pointed out that resumption of cyclicity
tended to be later in cows with higher NEFA concentrations during
the dry period as well as lactation, albeit not statistically significant.
Pancreatic function was not related to the resumption of cyclicity.
However, insulin sensitivity was not taken in account; we are
currently doing research about this.
Conclusions Our study demonstrates a decrease of pancreatic
function during NEB and a negative association between NEFA and
pancreatic function, suggesting a noxious effect of NEFA on the β-
cell. Although a significant effect of pancreatic function on fertility
was not found, the low pancreatic response is likely to contribute to
fertility and health disorders, based on the effects of insulin found in
larger studies.
Although NEB is inevitable in high yielding dairy cows, management
has a big impact on cow welfare. In this workshop, we aim to provide
food for thought and discussion: what can the farmer do to improve
the cow’s energy status and hence combine high yield with acceptable
fertility and health
WS07-2
Opportunities to influence postpartum ovarian activity by
nutrition in the modern high yielding dairy cow
Webb, R*, Sinclair, KD; Fouladi-Nashta, AA; Mann, GE; Garnsworthy, PC
The University of Nottingham, School of Biosciences, Sutton Bonington
Campus, Loughborough, Leicestershire, LE12 5RD; UK
Reduced fertility in high yielding dairy cows has major implications
for the economics and sustainability of individual and national dairy
herds. The interaction between genetics and nutrition can impact on
ovarian function, resulting in altered follicle growth and oocyte
quality, with subsequent negative effects on early embryo
development and foetal loss. Indeed nutrition influences ovarian
function when diet is inadequate, excessive or imbalanced. Dietary
induced changes are also modulated by body condition and excess
body fatness reduces food intake in post-natal dairy cows, leading to
mobilisation of body fat, metabolic imbalances and impaired fertility.
Dietary regimes have been used to alter peripheral metabolic
hormones such that increased plasma insulin concentration stimulated
earlier resumption of oestrous cycles postpartum. However, overfeeding
of fat animals can result in hyperinsulinemia and impaired
embryo development, which is exacerbated over time. In contrast,
fatty acids were shown to improve oocyte quality resulting in higher
blastocyst production. (There are also a lot of papers showing that
some fatty acids have a significant negative effect on oocyte
maturation and embryo development! So, please specify which fatty
acids are meant!)
The nutritional requirements for optimum milk production may be
different from the requirements for fertility. Hence the challenge has
been to devise nutritional strategies that can maintain milk production
and quality without compromising ovarian function and fertility. In a
major series of studies, it was demonstrated that the optimum strategy
for fertility in high-yielding dairy cows was initially to feed a diet that
stimulated follicular development and then to feed a diet that
improved the post-fertilisation developmental competence of oocytes.
Using this strategy, pregnancy rate was enhanced significantly even
with high milk yields. Pregnancy rate was related negatively to milk
yield and mobilisation of body fat, and positively to the UK Fertility
Index, demonstrating that nutrition can overcome physiological and
genetic influences on fertility.
In conclusion, an improved understanding of this multi-factorial
process has enabled nutrition to be matched to genotype, with a
positive impact on follicular growth, oestrous activity, oocyte quality,
blastocyst development and pregnancy rate. These results also
demonstrated how quickly diet can have its effect and that these
effects are cumulative over time and closely integrated with body
condition.
Supported by Defra, RERAD, Provimi, BOCM Pauls, ABNA
WS07-3
Genetic aspects of postpartal ovarian resumption in dairy
cows
Flint, APF
Nottingham University, UK
There is an unfavourable genetic correlation between milk yield and
fertility, which has caused a decline in fertility in dairy cattle over the
past 20 years, as a result of selection principally on yield. This loss of
fertility has been evident in unfavourable trends in traditional
measures of fertility such as calving interval, days open and nonreturn
rate. Recognition of these trends has raised appreciation of the
need to take measures to reverse them, resulting in the introduction of
fertility indexes in a number of countries.
Development of fertility indexes has however been hindered by the
low heritability and poor recording of traditional fertility traits. For
example the heritability (h 2 ) of frequently used traits such as calving
interval, non-return rate, days in milk to first service and number of
inseminations per conception is generally less than 0.05. This
adversely affects the accuracy and timeliness of index calculation.
The low heritability of these traits reflects the extent to which they are
affected by management practice. Attention has therefore been paid to
fertility traits which depend less on management, and more on the
physiology of the cow itself. One such trait is time to first ovulation
postpartum, determined by measuring milk progesterone
concentrations. This trait, measured in days, has h 2 in the range 0.16 –
0.23, and is genetically correlated with calving interval and body
condition score.
To include milk progesterone data in fertility index calculation would
require the measurement of progesterone in large numbers of milk
samples, which would be expensive and time consuming.
Investigations have therefore been made of the practicality of
measuring progesterone in milk samples obtained monthly at milk
recording visits. This is readily carried out where the infrastructure
exists to collect the samples, but is expensive and requires large
number of daughters per bull to obtain usable data.
Measurement of time to first oestrus postpartum from milk
progesterone profiles therefore provides a route to genetic
improvement in fertility. However molecular genomics methodologies
becoming available in the near future potentially offer a more cost
effective and timely approach to selection through prepubertal
identification of beneficial alleles in sires.
Workshop 08 - Reproductive Physiology and
Management of Reproduction in Farmed Cervidae
Moderator: Debra Berg (New Zealand)
WS08-1
Constraints to optimal reproductive productivity of
farmed red deer in New Zealand
Asher, G
Agricultural Systems, AgResearch, New Zealand
Optimal reproductive efficiency of red deer (Cervus elaphus) in
pastoral settings in NZ is often constrained by maladaption to the farm
environment. Three principle sources of reproductive wastage are, (1)
the conflict between seasonal physiology and nutrition, (2) suboptimal
calving environments, and (3) genetic/nutritional interactions
influencing timing of hind puberty. While seasonal breeding confers
benefit to the species within its natural range, there is misalignment
within more temperate zones between the high nutritional demands of
lactation in summer and the peak of pasture production in spring. This
can lead to reduced calf growth and depressed dam weights. Emphasis
has been placed on altering the timing of births to better align animal
and pasture productivity. While early studies to advance calving
focussed on artificial manipulation of mating dates (eg. melatonin
treatments) the new paradigm involves genetic selection for earlybreeding
phenotypes (eg. Eastern European red deer : C.e.