cast ewe deaths, grazing and late pregnancy

A place to exchange ideas, stories, and to solve problems related to breeding the flock and delivering lambs.
Richard Ehrhardt
Old Hand
Posts: 214
Joined: Thu Aug 30, 2007 10:08 am
Location: Eaton Rapids , MI
Contact:

cast ewe deaths, grazing and late pregnancy

Postby Richard Ehrhardt » Mon May 18, 2009 12:51 pm

I am curious what thoughts exist on the factors that seem to rather suddenly predispose ewes to becoming cast during late pregnancy resulting in fairly quick death. Also, if anyone has some preventative solutions to add, I would appreciate it.

I seem to lose a few ewes each year while lambing on grass. I have only lost one sheep ever to bloat otherwise. The typical case is a late pregnant ewe carrying 2 or more commonly 3+ lambs in good condition. The incidence of cast ewes appears in clusters as I can find 4 on one day and none for 2 or 3 days (all may survive if I catch them early or I may lose one or two). I find these clustered events to occur in late morning/early afternoon when the sun appears and resutls in warming after clouldy, cool, or wet weather. There is no safe pasture, I get the same incidence on straight grass or nearly straight clover. This problem occurs even in ewes highly adapated to lush grass as they can be grazing lush pasture for a month and suddenly I find a cluster of events on a day that is warming after a cool spell.

I wonder if the nutrient profile of forage is changing changing rapidly as the day warms and that this might be a major part of the problem. Perhaps the protein and energy fractions that create bloat conditions are especially high during these warming periods and the ewe eats then rests after grazing this forage and gas builds up too rapidly for eructation to dissipate it, causing the ewe to rotate on her back thus further compounding the problem. This condition in a ewe with a huge pregnant uterus creates intense intra-abdominal pressure that keeps the ewe from breathing.

I seldom lose non preg or early to mid preg ewes that are cast, just ewes during late pregnancy. As you may have guessed I just found one of these clustered events. I am working from home today and checked the ewes at 10 am and everything was fine. It was cool and overcast . Whe I went back out at 1 pm it was warm and breezy and I found 4 ewes cast. Three were fine but one died.

Lana Rowley
Old Hand
Posts: 1339
Joined: Fri Mar 24, 2006 12:50 pm
Location: Oregon
Contact:

Re: cast ewe deaths, grazing and late pregnancy

Postby Lana Rowley » Mon May 18, 2009 8:57 pm

We are having the same issue Richard..hope somebody has some ideas.


Lana

kris
Old Hand
Posts: 268
Joined: Thu Apr 09, 2009 11:43 am
Location: Vancouver Island, BC Canada

Re: cast ewe deaths, grazing and late pregnancy

Postby kris » Mon May 18, 2009 9:07 pm

Richard,

A ewe becoming 'cast' is a new term for me. What does it mean?

Kris

Darroll Grant
Old Hand
Posts: 3074
Joined: Thu Nov 01, 2007 11:58 am
Location: western Oregon
Contact:

Re: cast ewe deaths, grazing and late pregnancy

Postby Darroll Grant » Mon May 18, 2009 9:48 pm

Richard,
Are the survivors repeat offenders? Do their offspring exhibit the same problem?

I have watched ewes lay down and roll over on their back to wiggle, scratch and then roll back and get up. I wonder if some roll with too much gut preventing them from getting right side up.

Some years back I started to note the survivors. It seems many were repeats. We culled and have had about 1% a year.

Note from an aussie mate today that the flock was lambing so he had to make a round every couple of days to check out the new lambs (minimal care). He also related that he was harrowing a paddock to get the dips out so fewer sheep got cast. At this time he had 350 ewe lambs sold before they were born.
Darroll Grant
western Oregon

K Bar K Farm
Old Hand
Posts: 758
Joined: Fri Jun 30, 2006 10:15 am
Location: central Pennsylvania, USA
Contact:

Re: cast ewe deaths, grazing and late pregnancy

Postby K Bar K Farm » Tue May 19, 2009 5:42 am

Hi Richard,

I have had similar situations, and it seems to occur after prolonged periods of cool wet weather.

During cool wet weather the energy content is decreased in the forages, while the CP is high. The imbalance between protein and fermentable carbohydrate in pasture varies. The imbalance is greatest:

* after prolonged cloudy weather
* early in the day.

Also, this rapid growth pattern in the grasses could be setting sheep up for grass tetany (and possibly secondary milk fever?), which in mild cases of either, as you know, would impair muscle function, and possibly cause them to get cast.

Were these pastures fertilized? This can decrease NSC as well.

Have you checked the ewes for external parasites? it's possible they are trying to scratch their backs (rolling in the pasture like a horse) and a heavily pregnant ewe might get cast. What about flies?

Richard, are these ewes receiving any supplement (I'm assuming not)? I've read some places where feeding a bit of grain in the morning can help level out the CP:NSC imbalance (if that truly is the issue).

If I get a chance, I'll do some more digging in the literature, as I know there's information there, but have some other impending deadlines to attend to first.

Kathy
Kathy Soder
K Bar K Farm
Production-oriented, Performance-tested© Polled Dorsets
First to import Poll Dorset genetics from England in 50 years!
Central Pennsylvania

Justin-PA

Re: cast ewe deaths, grazing and late pregnancy

Postby Justin-PA » Tue May 19, 2009 7:50 am

kris wrote:Richard,

A ewe becoming 'cast' is a new term for me. What does it mean?

Kris


The ewe gets stuck on her back and can't get up. I have a ewe (that we named "stupid") that has done this chronically in mid to late pregnancy. She will either be dog food or go to the sale barn come late fall (still haven't decided, but too busy right now to worry about it).

Richard Ehrhardt
Old Hand
Posts: 214
Joined: Thu Aug 30, 2007 10:08 am
Location: Eaton Rapids , MI
Contact:

Re: cast ewe deaths, grazing and late pregnancy

Postby Richard Ehrhardt » Tue May 19, 2009 10:22 am

Hi,

Thanks for the helpful comments. The term "cast" in sheep refers to the situation in which a sheep literally gets stuck on its back and cannot turn over.

It is too bad that some of the rest of you also have this problem but on the other hand, it is reassuring to know that this is not an isolated problem.

Over the years, I have noted that some ewes tend to get cast easily and this can be under nearly any condition but the situation I am describing in late pregnancy is much less of a habitual problem. It seems that ewes that have never been cast before in their life can suddenly be found dead on their back.

I did think at one time that this condition could be related to the need of ewes to scratch their backs. So, I began giving all ewes a treatment of pyrethrin before turnout. It decreased itching some but did not change the incidence of cast ewes.

Kathy, I appreciate the insight you offered on the parallels between this condition and the conditions that trigger grass tetany and associated hypocalcemia. Indeed, I treated a ewe today for mild symptoms of this complex and she is already starting to respond. I am not sure if the two conditions (cast ewes and grass tetany) are linked but they are certainly associated as they occur under very similar conditions. I wonder if one could find a block that contains a surfactant for bloat prevention as well as supplemental Mg++? You can find mg supplements for cattle but they sometimes also contains lots of copper. Perhaps a mg/detergent block could work? One could offer it to ewes during late pregnancy and early lactation on grass. It would be nice to find a prevention for this problem as it kills some terrific sheep.

I had not realized that the ratio of soluble or rapidly fermentable protein and energy fractions of fresh grass could vary so much during a day. I have noted that there are silage making recommendations that are based on this concept. I imagine it is mostly energy that varies in terms of soluble CHO as the photosynthetic rate of the plant is probably quite high as the day warms under conditions of adequate moisture following a spell of relative dormancy.

K Bar K Farm
Old Hand
Posts: 758
Joined: Fri Jun 30, 2006 10:15 am
Location: central Pennsylvania, USA
Contact:

Re: cast ewe deaths, grazing and late pregnancy

Postby K Bar K Farm » Tue May 19, 2009 10:38 am

Richard Ehrhardt wrote: I have noted that there are silage making recommendations that are based on this concept. I imagine it is mostly energy that varies in terms of soluble CHO as the photosynthetic rate of the plant is probably quite high as the day warms under conditions of adequate moisture following a spell of relative dormancy.


Hank Mayland (ARS, Kimberly ID) did a lot of work on pm vs. am cut forage and preference of animals. They definitely preferred the pm cut forage, due to increased sugar.

The total protein content of the plant doesn't change much during the day, but the % protein can change due to several factors.....including the increasing sugar during the day diluting the % CP.

My former post doc conducted an interesting research project on this topic, looking at how the toughness (how tough it is to shear the plant) and other nutrients (including CP and water soluble carbohydrates) varied throughout the day.

Below is the citation and abstract:

Gregorini, P., K.J. Soder, M.A. Sanderson, and G.R. Ziegler. Toughness, particle size and chemical composition of meadow fescue (Festuca pratensis Hud.) herbage as affected by time of day. Animal Feed Sci. and Technol. 151:330-336. 2009.

Abstract:While herbage chemical composition varies diurnally, it is not known if this variation affects herbage biomechanical properties. The objective of this study was to evaluate changes in herbage toughness and particle size in relation to diurnal fluctuations of herbage chemical composition. Vegetative (tillers with 3 fully expanded leaves) micro-swards of Festuca pratensis Hud. were sampled at four times of the day: 06:50 (sunrise), 11:10, 15:30 and 19:25 h. Cut herbage was analysed for dry matter (DM), crude protein (CP), total non-structural carbohydrates (TNC), neutral and acid detergent fibre (NDF, ADF), in vitro true digestibility (IVTD), toughness and particle size. The experiment was repeated on two consecutive days. Diurnal variation of temperature, relative humidity and photosynthetic radiation were recorded every 5 min with an automated weather station. To characterize the relationship between dependent variables, Pearson correlations were performed. From 06:50 to 19:25, DM, TNC and the proportion of small particles (< 1 mm) increased (P < 0.05), CP, NDF, ADF, toughness and proportion of large particles (> 4.75 mm) decreased (P < 0.05) while IVTD remained constant (P > 0.05). Toughness was negatively correlated (P < 0.05) with DM and TNC concentrations, and positively correlated (P < 0.05) with percentages of NDF and mainly ADF. The proportion of small particles was positively correlated (P < 0.05) with DM and TNC concentrations, and negatively correlated (P < 0.05) with percentages of NDF, ADF and toughness. These results suggest an effect of time of day on herbage toughness and particle size as a function of increases in DM concentration and reductions of NDF and ADF concentrations due to an increase in TNC. Diurnal fluctuations in chemical composition of herbage not only result in differential nutrient supply to grazing ruminants during the day, but also in temporal fluctuations in herbage biomechanical features.

Kathy
Kathy Soder
K Bar K Farm
Production-oriented, Performance-tested© Polled Dorsets
First to import Poll Dorset genetics from England in 50 years!
Central Pennsylvania

Lana Rowley
Old Hand
Posts: 1339
Joined: Fri Mar 24, 2006 12:50 pm
Location: Oregon
Contact:

Re: cast ewe deaths, grazing and late pregnancy

Postby Lana Rowley » Tue May 19, 2009 11:51 am

We never had a cast ewe tell me moved here. The only sheep to cast have been the Coops.

Lana


Return to “Breeding and lambing”

Who is online

Users browsing this forum: Baidu [Spider] and 1 guest