Lactation pattern in Scottish Blackface and East Friesland × Scottish Blackface cross-bred ewes

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Abstract
Summary: Milk yield of 2-year-old Scottish Blackface and of East Friesland × Scottish Blackface ewes rearing single or twin lambs was estimated by the oxytocin method on 1 day each week up to the 14th week of lactation. Both groups of ewes had been reared from birth under good nutritional conditions. They were housed in individual pens from mid-pregnancy and offered a liberal ration of a pelleted concentrate food until parturition. Similar food was offered ad libitum during lactation.The cross-bred ewes rearing singles or twins produced significantly more milk in the first 12 weeks (181 and 258 kg respectively) than did pure Blackface ewes in the same period (144 and 208 kg respectively). The pattern of lactation differed between breeds. Cross-bred ewes attained higher maximum yields between the second and sixth weeks (2·37 and 3·32 kg/day, respectively, for single- and twin-suckled ewes) than did the Blackface ewes (1·97 and 2·88 kg/day). The yield from the cross-breds was sustained at a higher level throughout lactation. In the third 4-week period cross-bred ewes rearing single and twin lambs produced 116 and 92%, respectively, of their yield in the first 4 weeks whilst Blackface ewes produced 87 and 65%, respectively.In the sixth week of lactation the milk produced by the two breed groups was similar in quality (mean value of solids-not-fat 11·04% and fat 5·48%) but by the 11th week the fat percentage of milk produced by Blackface ewes had increased significantly to 7·34% whereas that of the cross-breds had remained almost unchanged.Single-suckled ewes gained weight throughout lactation but twin-suckled ewes remained relatively constant. Lambs reared as singles by cross-bred or Blackface ewes reached a mean live weight of 36·2 and 35·0 kg at 102 days of age, respectively, compared with 33·6 and 30·1 kg for twin lambs. Food intake of all ewes increased until the fifth or sixth week of lactation.