Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias
Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias
Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
16 t h International Congress on Animal <strong>Reproduction</strong><br />
Workshop Abstracts 13<br />
other reports, a high percentage of cows suffered from <strong>de</strong>layed<br />
ovarian function: only 60.9% of the cows ovulated with<strong>in</strong> the first 42<br />
days pp. Survival analysis po<strong>in</strong>ted out that resumption of cyclicity<br />
ten<strong>de</strong>d to be later <strong>in</strong> cows with higher NEFA concentrations dur<strong>in</strong>g<br />
the dry period as well as lactation, albeit not statistically significant.<br />
Pancreatic function was not related to the resumption of cyclicity.<br />
However, <strong>in</strong>sul<strong>in</strong> sensitivity was not taken <strong>in</strong> account; we are<br />
currently do<strong>in</strong>g research about this.<br />
Conclusions Our study <strong>de</strong>monstrates a <strong>de</strong>crease of pancreatic<br />
function dur<strong>in</strong>g NEB and a negative association between NEFA and<br />
pancreatic function, suggest<strong>in</strong>g a noxious effect of NEFA on the β-<br />
cell. Although a significant effect of pancreatic function on fertility<br />
was not found, the low pancreatic response is likely to contribute to<br />
fertility and health disor<strong>de</strong>rs, based on the effects of <strong>in</strong>sul<strong>in</strong> found <strong>in</strong><br />
larger studies.<br />
Although NEB is <strong>in</strong>evitable <strong>in</strong> high yield<strong>in</strong>g dairy cows, management<br />
has a big impact on cow welfare. In this workshop, we aim to provi<strong>de</strong><br />
food for thought and discussion: what can the farmer do to improve<br />
the cow’s energy status and hence comb<strong>in</strong>e high yield with acceptable<br />
fertility and health<br />
WS07-2<br />
Opportunities to <strong>in</strong>fluence postpartum ovarian activity by<br />
nutrition <strong>in</strong> the mo<strong>de</strong>rn high yield<strong>in</strong>g dairy cow<br />
Webb, R*, S<strong>in</strong>clair, KD; Fouladi-Nashta, AA; Mann, GE; Garnsworthy, PC<br />
The University of Nott<strong>in</strong>gham, School of Biosciences, Sutton Bon<strong>in</strong>gton<br />
Campus, Loughborough, Leicestershire, LE12 5RD; UK<br />
Reduced fertility <strong>in</strong> high yield<strong>in</strong>g dairy cows has major implications<br />
for the economics and susta<strong>in</strong>ability of <strong>in</strong>dividual and national dairy<br />
herds. The <strong>in</strong>teraction between genetics and nutrition can impact on<br />
ovarian function, result<strong>in</strong>g <strong>in</strong> altered follicle growth and oocyte<br />
quality, with subsequent negative effects on early embryo<br />
<strong>de</strong>velopment and foetal loss. In<strong>de</strong>ed nutrition <strong>in</strong>fluences ovarian<br />
function when diet is <strong>in</strong>a<strong>de</strong>quate, excessive or imbalanced. Dietary<br />
<strong>in</strong>duced changes are also modulated by body condition and excess<br />
body fatness reduces food <strong>in</strong>take <strong>in</strong> post-natal dairy cows, lead<strong>in</strong>g to<br />
mobilisation of body fat, metabolic imbalances and impaired fertility.<br />
Dietary regimes have been used to alter peripheral metabolic<br />
hormones such that <strong>in</strong>creased plasma <strong>in</strong>sul<strong>in</strong> concentration stimulated<br />
earlier resumption of oestrous cycles postpartum. However, overfeed<strong>in</strong>g<br />
of fat animals can result <strong>in</strong> hyper<strong>in</strong>sul<strong>in</strong>emia and impaired<br />
embryo <strong>de</strong>velopment, which is exacerbated over time. In contrast,<br />
fatty acids were shown to improve oocyte quality result<strong>in</strong>g <strong>in</strong> higher<br />
blastocyst production. (There are also a lot of papers show<strong>in</strong>g that<br />
some fatty acids have a significant negative effect on oocyte<br />
maturation and embryo <strong>de</strong>velopment! So, please specify which fatty<br />
acids are meant!)<br />
The nutritional requirements for optimum milk production may be<br />
different from the requirements for fertility. Hence the challenge has<br />
been to <strong>de</strong>vise nutritional strategies that can ma<strong>in</strong>ta<strong>in</strong> milk production<br />
and quality without compromis<strong>in</strong>g ovarian function and fertility. In a<br />
major series of studies, it was <strong>de</strong>monstrated that the optimum strategy<br />
for fertility <strong>in</strong> high-yield<strong>in</strong>g dairy cows was <strong>in</strong>itially to feed a diet that<br />
stimulated follicular <strong>de</strong>velopment and then to feed a diet that<br />
improved the post-fertilisation <strong>de</strong>velopmental competence of oocytes.<br />
Us<strong>in</strong>g this strategy, pregnancy rate was enhanced significantly even<br />
with high milk yields. Pregnancy rate was related negatively to milk<br />
yield and mobilisation of body fat, and positively to the UK Fertility<br />
In<strong>de</strong>x, <strong>de</strong>monstrat<strong>in</strong>g that nutrition can overcome physiological and<br />
genetic <strong>in</strong>fluences on fertility.<br />
In conclusion, an improved un<strong>de</strong>rstand<strong>in</strong>g of this multi-factorial<br />
process has enabled nutrition to be matched to genotype, with a<br />
positive impact on follicular growth, oestrous activity, oocyte quality,<br />
blastocyst <strong>de</strong>velopment and pregnancy rate. These results also<br />
<strong>de</strong>monstrated how quickly diet can have its effect and that these<br />
effects are cumulative over time and closely <strong>in</strong>tegrated with body<br />
condition.<br />
Supported by Defra, RERAD, Provimi, BOCM Pauls, ABNA<br />
WS07-3<br />
Genetic aspects of postpartal ovarian resumption <strong>in</strong> dairy<br />
cows<br />
Fl<strong>in</strong>t, APF<br />
Nott<strong>in</strong>gham University, UK<br />
There is an unfavourable genetic correlation between milk yield and<br />
fertility, which has caused a <strong>de</strong>cl<strong>in</strong>e <strong>in</strong> fertility <strong>in</strong> dairy cattle over the<br />
past 20 years, as a result of selection pr<strong>in</strong>cipally on yield. This loss of<br />
fertility has been evi<strong>de</strong>nt <strong>in</strong> unfavourable trends <strong>in</strong> traditional<br />
measures of fertility such as calv<strong>in</strong>g <strong>in</strong>terval, days open and nonreturn<br />
rate. Recognition of these trends has raised appreciation of the<br />
need to take measures to reverse them, result<strong>in</strong>g <strong>in</strong> the <strong>in</strong>troduction of<br />
fertility <strong>in</strong><strong>de</strong>xes <strong>in</strong> a number of countries.<br />
Development of fertility <strong>in</strong><strong>de</strong>xes has however been h<strong>in</strong><strong>de</strong>red by the<br />
low heritability and poor record<strong>in</strong>g of traditional fertility traits. For<br />
example the heritability (h 2 ) of frequently used traits such as calv<strong>in</strong>g<br />
<strong>in</strong>terval, non-return rate, days <strong>in</strong> milk to first service and number of<br />
<strong>in</strong>sem<strong>in</strong>ations per conception is generally less than 0.05. This<br />
adversely affects the accuracy and timel<strong>in</strong>ess of <strong>in</strong><strong>de</strong>x calculation.<br />
The low heritability of these traits reflects the extent to which they are<br />
affected by management practice. Attention has therefore been paid to<br />
fertility traits which <strong>de</strong>pend less on management, and more on the<br />
physiology of the cow itself. One such trait is time to first ovulation<br />
postpartum, <strong>de</strong>term<strong>in</strong>ed by measur<strong>in</strong>g milk progesterone<br />
concentrations. This trait, measured <strong>in</strong> days, has h 2 <strong>in</strong> the range 0.16 –<br />
0.23, and is genetically correlated with calv<strong>in</strong>g <strong>in</strong>terval and body<br />
condition score.<br />
To <strong>in</strong>clu<strong>de</strong> milk progesterone data <strong>in</strong> fertility <strong>in</strong><strong>de</strong>x calculation would<br />
require the measurement of progesterone <strong>in</strong> large numbers of milk<br />
samples, which would be expensive and time consum<strong>in</strong>g.<br />
Investigations have therefore been ma<strong>de</strong> of the practicality of<br />
measur<strong>in</strong>g progesterone <strong>in</strong> milk samples obta<strong>in</strong>ed monthly at milk<br />
record<strong>in</strong>g visits. This is readily carried out where the <strong>in</strong>frastructure<br />
exists to collect the samples, but is expensive and requires large<br />
number of daughters per bull to obta<strong>in</strong> usable data.<br />
Measurement of time to first oestrus postpartum from milk<br />
progesterone profiles therefore provi<strong>de</strong>s a route to genetic<br />
improvement <strong>in</strong> fertility. However molecular genomics methodologies<br />
becom<strong>in</strong>g available <strong>in</strong> the near future potentially offer a more cost<br />
effective and timely approach to selection through prepubertal<br />
i<strong>de</strong>ntification of beneficial alleles <strong>in</strong> sires.<br />
Workshop 08 - Reproductive Physiology and<br />
Management of <strong>Reproduction</strong> <strong>in</strong> Farmed Cervidae<br />
Mo<strong>de</strong>rator: Debra Berg (New Zealand)<br />
WS08-1<br />
Constra<strong>in</strong>ts to optimal reproductive productivity of<br />
farmed red <strong>de</strong>er <strong>in</strong> New Zealand<br />
Asher, G<br />
Agricultural Systems, AgResearch, New Zealand<br />
Optimal reproductive efficiency of red <strong>de</strong>er (Cervus elaphus) <strong>in</strong><br />
pastoral sett<strong>in</strong>gs <strong>in</strong> NZ is often constra<strong>in</strong>ed by maladaption to the farm<br />
environment. Three pr<strong>in</strong>ciple sources of reproductive wastage are, (1)<br />
the conflict between seasonal physiology and nutrition, (2) suboptimal<br />
calv<strong>in</strong>g environments, and (3) genetic/nutritional <strong>in</strong>teractions<br />
<strong>in</strong>fluenc<strong>in</strong>g tim<strong>in</strong>g of h<strong>in</strong>d puberty. While seasonal breed<strong>in</strong>g confers<br />
benefit to the species with<strong>in</strong> its natural range, there is misalignment<br />
with<strong>in</strong> more temperate zones between the high nutritional <strong>de</strong>mands of<br />
lactation <strong>in</strong> summer and the peak of pasture production <strong>in</strong> spr<strong>in</strong>g. This<br />
can lead to reduced calf growth and <strong>de</strong>pressed dam weights. Emphasis<br />
has been placed on alter<strong>in</strong>g the tim<strong>in</strong>g of births to better align animal<br />
and pasture productivity. While early studies to advance calv<strong>in</strong>g<br />
focussed on artificial manipulation of mat<strong>in</strong>g dates (eg. melaton<strong>in</strong><br />
treatments) the new paradigm <strong>in</strong>volves genetic selection for earlybreed<strong>in</strong>g<br />
phenotypes (eg. Eastern European red <strong>de</strong>er : C.e.