Intensifying ewe productivity

Robinson, John J.

doi:10.1017/s030822960000043x

Cited by 25 publications

(10 citation statements)

References 21 publications

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“…However, because these data are confounded by possible differences in both location and individual ram effects, these studies should be replicated under more precisely controlled conditions to determine the cause of this effect. Application of light control to intensify lamb production has already received some attention (Robinson, 1974;Vesely, 1975Vesely, , 1978. Caution regarding the interpretation of estrus induction and conception by specific light treatments to ewes at various times of the year or from one year to the next, however, should be taken.…”

Section: Discussionmentioning

confidence: 99%

Relationship of Daylength and Prolactin to Resumption of Reproductive Activity in Anestrous Ewes

Schanbacher¹

1980

Journal of Animal Science

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SummaryConcentrations of prolactin were measured in serum from three groups of Rambouillet ewes for 8 weeks to determine whether changes in prolactin concentrations were important during the transition from anestrus to seasonal breeding. Group I (control ewes) was maintained under conditions of natural daylength;group II (short-day ewes) was exposed abruptly on the longest day of the year to artificially shortened daylengths (8 hr light and 16 hr darkness); group III (CB 154 ewes) was maintained similar to control ewes except each ewe received twice daily im injections of 2-bromo,a-ergocryptine (CB 154). A fertile ram was kept with each group of ewes. Average serum prolactin remained above 200 ng/ml in control ewes throughout the 8-week study; however, short-day ewes had reduced (P<.05) serum prolactin and CB 154 ewes had low to nondetectable serum prolactin. Despite these differences, average interval to first estrus for the three groups of ewes was similar (control ewes, 25.2 + 3.0; short-day ewes, 23.5 + 2.9; CB 154 ewes, 26.4 + 4.3 days). Short-day and CB 154 treatments did have an apparent effect on interval to conception. Of those ewes that lambed, short daylengths advanced (P<.O1) the average date of conception by 7.7 days in relation to that of controls, whereas CB 154 treatment delayed ! The technical assistance of Ms. Becky Chmelka and Ms. Donna Taubenheim and cooperation of the Nebraska Agr. Exp. Sta., Univ. of Nebraska, Lincoln, is gr2atefully acknowledged.

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Section: Discussionmentioning

confidence: 99%

Relationship of Daylength and Prolactin to Resumption of Reproductive Activity in Anestrous Ewes

Schanbacher¹

1980

Journal of Animal Science

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“…Such an approach has already been taken on a small scale by scientists in Great Britain (Robinson, 1974). The sheep must be under the influence of a continuous light control representing a regime of long (16 h) and short days (8 h) arranged in a 225-day instead of a 365-day period.…”

Section: Resultsmentioning

confidence: 99%

Application of light control to shorten the production cycle in two breeds of sheep

Vesely¹

1978

Anim. Sci.

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An average of 60 Rambouillet and 60 Suffolk ewes was maintained under an intensive management system to lamb about every 7 months. Decreased daylength was used for oestrus induction in normally anoestrous periods. The experiment lasted 3-7 years, during which time six lamb crops were produced, three of them as a result of outof-season mating. Ewes of each breed were subdivided into three experimental groups and each breed-group was maintained under one of three different light treatments before and during out-ofseason mating. Imposed Treatment 1 consisted of a pre-mating period under natural daylight followed by a mating period of short daylength (8 h/day). Ewes under imposed Treatments 2 and 3 were exposed to 16 h of light during the pre-mating period and to 8 h of daylight during the mating period. This did not affect conception significantly in the Rambouillet but it did in the Suffolk. Different intensities and wavelengths of light during the long daylight period (16 h/day) were used in Treatments 2 and 3 but did not cause different responses. In Rambouillet ewes the first mating (out-of-season) gave 73 % conception. It was followed by two in-season matings with 72 and 85 % conceptions. The last three matings (out-of-season, in-season, outof-season) resulted in 57, 42, and 58 % conceptions. In the Suffolk ewes, the conceptions were 30, 88, 77, 3, 77, and 10% in the same order as those for Rambouillet. The average production of Rambouillets on the three treatments was 166 lambs per 100 ewes per year (165, 177, 157) whereas Suffolks produced 132 lambs (120, 143, 135). Control Rambouillet and Suffolk ewes maintained under natural daylight year-round produced 139 and 117 lambs.

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“…Such estimates do not take into consideration the possible reduction in foetal growth due to undernutrition. On the basis of expected lamb birth weights for wellnourished ewes of the breed (Robinson, 1974), no reduction in foetal growth was apparent for singles and at maximum, the growth rate of multiples for the period of undernutrition was unlikely to be depressed by more than 30%. This being so, the daily loss of nitrogen from the maternal body probably approached 6 g/day, a value equivalent to approximately 80% of the urinary nitrogen excretion of fasting non-pregnant sheep (Blaxter, 1962).…”

Section: Discussionmentioning

confidence: 96%

The effect of a reduction in food intake during late pregnancy on nitrogen metabolism in ewes

Guada¹,

Robinson²,

Fraser³

1976

J. Agric. Sci.

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Twelve Finnish Landrace x Dorset Horn ewes with a mean litter size of 1-92 and a mean body weight of 75 + 3 kg were individually penned from 80 days of gestation to parturition and offered a diet with a metabolizable energy (ME) and crude protein content in the dry matter of 9-7 MJ/kg and 11-4% respectively. At 120 days of gestation daily ME intake was abruptly reduced from a mean of 0-48 to 0-25 MJ/kg TF 0 ' 75 for a period of 10 days.The observed increase in the plasma concentration of urea due to the reduction in food intake was better correlated with lamb birth weight (r -0-87) than was the increase in plasma free fatty acid concentration (r = 0-53) or the decrease in plasma glucose concentration (r = 0-76). Mean daily nitrogen balance decreased from a mean of 5-6 g before food restriction to -1-8 g after food restriction. Although the effect was not significant, single bearing ewes excreted more total and urea nitrogen in the urine than multiple bearing ewes before food restriction. During food restriction the trend was reversed. The change in urea nitrogen excretion (Y, g/day) that resulted from the reduction in food intake was correlated (r = 0-73, P < 0-01) with lamb birth weight {X, kg); the relationship was Y = 0-54( + 0-16)X-3-48. It was estimated that the daily loss of nitrogen from the maternal body during the period of food restriction was approximately 80 % of published values for the urinary nitrogen excretion of fasting non-pregnant sheep. _, occurring, degrees of undemutrition recorded under ±JN J. ±tOJJ U O J. 1USS field c o n d i t i o n s (Rugged 19 7 ! ) .A lower excretion of urinary nitrogen in pregnant The present experiment was made to test the compared with non-pregnant ewes (Graham, 1964) effects on nitrogen metabolism in ewes of reducing and a progressive reduction in urinary urea nitro-the energy intake in late pregnancy from approxigen excretion between 90 days of gestation and mately 1-3 to 0-7 times their maternal maintenance parturition (Robinson, Scott & Fraser, 1973) are requirements. A brief account of part of the work characteristic effects of pregnancy on nitrogen has been reported earlier (Guada & Robinson, metabolism in ewes given adequate amounts of 1974). dietary energy and protein. In contrast the effects EXPERIMENTAL PROCEDURE of undernutntion on nitrogen metabolism during late pregnancy in ewes are less well denned, even Diet. A single diet was used. It consisted of 50 % though varying degrees of inappetance during late hay ground through a 2-5-cm screen, 40 % rolled pregnancy, particularly in over-fat polytocous ewes barley, 5 % soya-bean meal, 5 % molasses, plus (Reid, 1968; J. J. Robinson, unpublished data), (per kg of feed) 22 g steamed bone flour, 7-5 g salt have been noted. Graham (1968) studied the short-and 1-5 g of a trace mineral and vitamin suppleterm effects on nitrogen metabolism in late preg-ment. Each g of the latter contained 150 mg nancy of an abrupt reduction in energy intake to ZnSO 4 .7H 2 O; 80 mg MnSO 4 .7H 2 O; 200 mg KIO 3 ; 25% of estimated req...

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Intensifying ewe productivity

Cited by 25 publications

References 21 publications

Relationship of Daylength and Prolactin to Resumption of Reproductive Activity in Anestrous Ewes

Relationship of Daylength and Prolactin to Resumption of Reproductive Activity in Anestrous Ewes

Application of light control to shorten the production cycle in two breeds of sheep

The effect of a reduction in food intake during late pregnancy on nitrogen metabolism in ewes

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