diff --git a/src/main/java/no/bioforsk/vips/model/roughagenutritionmodel/RoughageNutritionModelImpl.java b/src/main/java/no/bioforsk/vips/model/roughagenutritionmodel/RoughageNutritionModelImpl.java
index c2730bcf3be34e983396daed7412f86fb0fe4190..8f18501b13e0707fdd3b00cbf39ceed5ce1fe93b 100755
--- a/src/main/java/no/bioforsk/vips/model/roughagenutritionmodel/RoughageNutritionModelImpl.java
+++ b/src/main/java/no/bioforsk/vips/model/roughagenutritionmodel/RoughageNutritionModelImpl.java
@@ -36,6 +36,7 @@ import java.util.logging.Logger;
 import java.util.stream.Collectors;
 import no.nibio.vips.entity.WeatherObservation;
 import no.nibio.vips.model.ModelExcecutionException;
+import no.nibio.vips.util.WeatherUtil;
 
 // Using Commons math and Nelder-Mead for parameter optimization
 import org.apache.commons.math.ConvergenceException;
@@ -736,6 +737,24 @@ public class RoughageNutritionModelImpl implements CostFunction {
         //System.out.println("m=" + m);
         return m;
     }
+    
+    /**
+     * @return
+     * @throws ModelExcecutionException 
+     */
+    private Date getForsteApril() throws ModelExcecutionException
+    {
+        // Calculating start and end date of weather data retrieval
+        // Start is April 1st
+        Calendar cal = Calendar.getInstance(timeZone);
+        cal.setTime(this.getVekstStart());
+        cal.set(Calendar.MONTH, Calendar.APRIL);
+        cal.set(Calendar.DATE, 1);
+
+        WeatherUtil wUtil = new WeatherUtil();
+        return wUtil.normalizeToExactDate(cal.getTime(), timeZone);
+
+    }
 
     /**
      * Løper gjennom eksisterende klimadatasett og beregner utvikling
@@ -751,6 +770,7 @@ public class RoughageNutritionModelImpl implements CostFunction {
         }
 
         boolean first = true;
+        boolean firstTemperaturSum = true;
         Date forrigeDato = null;
         List<WeatherObservation> tempCopy = new ArrayList<>(this.luftTemperaturVerdier);
         for (Iterator<WeatherObservation> tempI = tempCopy.iterator(); tempI.hasNext();) {
@@ -758,10 +778,15 @@ public class RoughageNutritionModelImpl implements CostFunction {
             temperatur = tempI.next();
 
             //Setter Ts1
-            if (first) {
-                this.AIBakgrunnsdataMatrise.setParamDoubleValueForDate(temperatur.getTimeMeasured(), AIDataMatrix.TS1, temperatur.getValue());
-            } else {
-                this.AIBakgrunnsdataMatrise.setParamDoubleValueForDate(temperatur.getTimeMeasured(), AIDataMatrix.TS1, temperatur.getValue() + this.AIBakgrunnsdataMatrise.getParamDoubleValueForDate(forrigeDato, AIDataMatrix.TS1));
+            // At første april (og ikke f.eks. vekststart) er grense her, er pr. 2023-09 til vurdering av Anne Kjersti Bakken
+            if (temperatur.getTimeMeasured().compareTo(this.getForsteApril()) >= 0)
+            {
+                if (firstTemperaturSum) {
+                    this.AIBakgrunnsdataMatrise.setParamDoubleValueForDate(temperatur.getTimeMeasured(), AIDataMatrix.TS1, temperatur.getValue());
+                    firstTemperaturSum = false;
+                } else {
+                    this.AIBakgrunnsdataMatrise.setParamDoubleValueForDate(temperatur.getTimeMeasured(), AIDataMatrix.TS1, temperatur.getValue() + this.AIBakgrunnsdataMatrise.getParamDoubleValueForDate(forrigeDato, AIDataMatrix.TS1));
+                }
             }
 
             // Beregner DVR