Castrated Male Lambs Research Articles

Growth rate and carcase composition of Border Leicester x Scottish Blackface, East Frlesland x Blackface and East Friesland x North Country Cheviot Lambs

The East Friesland breed, developed as a dairy sheep, has a potentially useful role as a sire of first-cross breeding ewes from hill breeds of sheep. Advantages have been shown in terms of reproductive and lactation performance (Doney et al, 1983, Gunn, 1986) but the carcase conformation may reduce the acceptability of first-cross castrated male (wether) lambs. The characteristics of lambs derived from dairy-type breeds may be suitable for the heavy, lean carcase market (Butler-Hogg et al, 1985). The present study was undertaken as a pilot investigation of the potential growth rate and carcase composition of wether lambs over a range of live weights. East Friesland X Blackface (EFB) wethers were compared with a similar group of Border Leicester X Blackface (BLB) and a smaller group of East Friesland X North Country Cheviot (EFC) wethers.

The use of dosed and herbage n-alkanes as markers for the determination of herbage intake

SUMMARYThe recovery in the faeces of the n-alkanes of herbage (odd-chain, C27–C35) and of dosed artificial alkanes (even-chain, C28 and C32) was studied in twelve 4-month-old castrated male lambs. The lambs received three levels of cut, fresh perennial ryegrass or a mixed diet of perennial ryegrass (0·70) and a barley-based concentrate (0·30) (500–900 g D.M./day). C28 and C32 n-alkanes (130 mg each), absorbed onto shredded paper, were given once daily for 17 days to test whether the recoveries of herbage and dosed alkanes were similar to enable their use as markers for determining the herbage intake of grazing sheep. Stearic and palmitic acids (130 mg each) were given with the dosed alkanes to half of the animals with the objective of facilitating emulsification of the dosed alkanes within the digestive tract.With the exception of C27 n-alkane, the faecal recoveries of all alkanes were unaffected by diet, feeding level or emulsifying agent. Faecal recovery of odd- chain herbage n-alkanes increased with increasing C-chain length. The recovery of the dosed C28 n-alkane was slightly greater than the recoveries of both C27, and C29 n-alkanes of herbage. The recoveries of the dosed C32 n-alkane and the herbage C33-alkane were the same.The mean herbage intake estimated using C33 and C32 n-alkanes was identical to the actual herbage intake. Other alkane pairs gave slight underestimates of herbage intake ranging from 3·5% for the C28–C29 pair to 7·6% for the C27–C28 pair. No cyclical pattern of n-alkane excretion throughout the day was observed. Examination of daily variations in faecal alkane concentrations indicated that the start of alkane dosing should precede the sampling of faeces by at least 6 days.These results suggest that accurate estimation of herbage intake in grazing sheep is possible from the simultaneous use of dosed C32 and herbage C33 n-alkanes as markers.The method may be particularly useful in enabling unbiased estimates of herbage intake to be made in animals receiving supplementary feed.

A comparison of alternative methods for predicting the carcass composition of crossbred lambs of different breeds and crosses

Carcass data for a total of 2808 lambs from three breed trials were used to evaluate a series of linear measurements, visual scores and the proportions of tissues in joints as predictors of carcass composition. The trials involved crossbred lambs out of different dam types by sires of the main British meat breeds and by Ile de France, Oldenburg and Texel sires. Each trial was carried out over a number of years and involved approximately equal numbers of female and castrated male lambs. Potential predictors were examined in terms of the precision of prediction and in terms of the robustness of prediction equations to differences in sire breed and sex. The overall standard deviation (s.d.) of carcass lean percentage averaged over trials was 4·3. Combinations of simple measurements, including visual fat scores, percentage perinephric and retroperitoneal fat in carcass and M. longissimus dimensions achieved a residual s.d. of 2·5 for carcass lean percentage. The application of an overall prediction equation to individual sire breed means resulted in considerable bias (predicted-actual lean percentage): the mean square deviation was 0·75. In comparison, the sex differences were relatively unimportant. The precision of sample joints was examined in relation to their cost of dissection. The best end neck and shoulder joints offered a high level in relation to cost: typical residual s.d. were 1·5 for carcass lean percentage. Joints and combination of joints with high predictive precision tended to have equations that were robust to differences between sire breeds.

The effect of mechanical treatment of silage on intake and production of sheep

ABSTRACTOver a period of 3 years, silages subjected to various mechanical treatments by the use of conventional silage harvesters were offered ad libitum to pregnant ewes and to castrated male lambs and the effects on intake and productivity were measured. The intake of silage made from grass harvested with a precision-chop harvester was substantially greater than the intake of silage made with other types of harvester (especially, a flail harvester), causing a lower degree of comminution.Mean daily silage dry-matter intake of ewes was 0·99 kg and 1·28 kg in mid-pregnancy, and 0·85 kg and 1·10 kg in late pregnancy with flail-harvested and precision-chop silages respectively. Silage was supplemented with various levels of concentrate in late pregnancy and an increasing level of concentrates did not reduce silage intake. In early lactation, when 800 g concentrate was given daily, ewes consumed 1·00 kg flail-harvested silage and 1·39 kg precision-chop silage. Compared with flail-harvested silage, precision-chop silage increased ewe body weight immediately post lambing by 5·1 kg, lamb birth weight by 0·27 kg and lamb growth rate by 58 g/day. Increases in intake of precision-chop silages by hoggets were on average greater, though more variable, than by ewes and were reflected in increased carcass weight.The reason for the increased intake of the finely-chopped silage was examined. It would appear that the major factor is the physical size of particle involved though there was some evidence that improved fermentation resulting from finer chopping may have been partly responsible for increased intake.

The effect of daylength on the growth of lambs 4. Daylength extension to 20h under practical conditions

ABSTRACT1. Four experiments were performed to study the effects on the growth of lambs of extending natural daylength to 20 h with dim artificial light, under management conditions similar to those on commercial farms.2. Thirty-six female lambs aged 6 months were given a concentrate ration at a restricted level in groups of nine; there was significantly faster live-weight gain in the two groups that received extra light but no effect on carcass weight or linear measurements.3. Forty-eight castrated male lambs were fed either ad libitum or at a restricted level on a concentrate diet; half were given additional light. Feeding ad libitum gave faster growth than restricted feeding but there were no significant effects of daylength.4. One hundred and fourteen lambs of mixed sex were offered silage ad libitum plus one of three concentrate supplements at an average of 0·25 kg per head per day. Half were exposed to 20·h daylength from mid-October until slaughter in mid-January. There were no effects of light treatment on growth or carcass weights.5. The fourth experiment was a repeat of the third and again there were no effects of extended daylength.6. It is concluded that this method of controlling daylength is not appropriate for commercial use.

The effect of plane of nutrition on the body composition of two breeds of wearier sheep fed a high protein diet

SUMMARYCorriedale and Dorset Horn castrate male (wether) lambs reared at pasture were weaned at 19 kg live weight (LW), brought indoors and fed a high protein diet such that half of each group grew at ca. 200 g/day and the other half at ca. 100 g/day. Animals were slaughtered at 25 and 30 kg LW and chemical composition (protein, fat, energy, water and ash) of the body determined. The relationship between each body component and shorn empty-body weight was examined by regression analysis.Within levels of feeding the results were similar in the two breeds. When comparisons were made between feeding levels, the slower-growing animals contained more fat, energy and ash than the faster-growing group, less water, but similar amounts of protein at any given empty-body weight.

Effects of cranial cervical ganglionectomy and castration of male lambs. III. Hormonal responses following administration to gonadotrophin releasing hormone (GnRH)

Entire and castrate male lambs, which were cranial cervical ganglionectomized (GX) or untreated, were utilized in a study of responses to intravenous GnRH; 24 animals were treated at both 101 and 277 days of age. GX caused a reduction in basal LH concentrations of both wethers and rams at the first sampling, but increased pre-injection levels of this hormone in 277 day old wethers. Basal LH levels of castrates were substantially higher than those of entires, but GX had no significant influence on pretreatment testosterone secretion in rams. GnRH treatment elevated plasma LH levels in all animals, while in entires increases in testosterone concentrations also occurred. Castration significantly increased peak LH levels together with total LH output. At neither age were the LH or testosterone reponses influenced significantly by GX, nor was the interaction of castration and GX significant for LH response data. The major effect of age at GnRH treatment was that markedly higher testosterone responses were recorded from the older rams.

A note on the effect of autumn shearing on performance of fattening lambs

ABSTRACTForty-eight castrate male and female Suffolk cross Mule lambs were used in a 2 × 2 factorial experiment to investigate the effect of autumn shearing and sex on growth performance over 46 days before slaughter. Lambs were penned individually outdoors and given pelleted lucerne ad libitum.Shearing increased average food intake by 0·072 (P<0·05), live-weight gain by 0·149 (P<0·01) and carcass weight by 0·058 (P<0·05). It is concluded that shearing is financially worthwhile in climatic conditions such as the present experiment.

The effect of daylength on the growth of lambs. 1. Comparisons of sex, level of feeding, shearing and breed of sire

ABSTRACTTwo experiments were carried out with crossbred lambs which had been weaned in July when 16 weeks old. From early September they were kept in a light-proof building with 12 h artificial light per day for 3 weeks and then half were exposed to 16 h and half to 8 h light per day for a further 16 weeks.Experiment 1 included 72 lambs (48 castrated males and 24 females) and half in each daylength were fed on a concentrated ration ad libitum; the other half were restricted to 70 g/kg live weight0·75 per day. Half of each group were shorn. Lambs kept in 16 h light per day grew significantly faster than those in short daylength at both levels of feeding. Food conversion ratio was best in the 16 h restricted sheep. Unshorn lambs had heavier carcasses than shorn lambs. Long daylength stimulated general growth of the animal without markedly affecting carcass composition, irrespective of level of feeding, whereas ad libitum feeding resulted in much fatter carcasses than did restricted feeding. Gut fill was significantly greater in long-daylength sheep.Experiment 2 included 24 individually penned castrated male lambs, 12 of which were sired by Suffolk rams and 12 by Oxford rams; all were fed at the restricted level. Long daylength significantly stimulated weight gain, especially in the Oxford-cross lambs, but the increase in carcass weight was not significant in this experiment due to the large effect on gut fill.It was concluded that long daylength stimulated growth and gut fill by some central control mechanism and not merely by encouraging more eating.

Influence of prostaglandins and thyrotropin releasing hormone (TRH) on hormone secretion and growth in wether lambs

A series of experiments were conducted in ewes and whether (castrate male) lambs to evaluate the influence of prostaglandins on secretion of anabolic hormones and to determine if repeated injections of prostaglandin (PG) F2alpha would chronically influence the secretion of these hormones and perhaps growth rate as well. A single intravenous injection of PGA1 and PGB1 (100 microgram/kg) exerted no significant (P greater than .10) influence on plasma concentrations of prolactin (PRL), growth hormone (GH) or thyrotropin (TSH) in ewes. PGA1, but not PGB1, stimulated an increase in the plasma concentration of insulin. Infusion of PGF2alpha for 5.5 hr into ewes resulted in increased (P less than .05) plasma concentrations of both GH and ARL while TSH and insulin were not significantly influenced. Prostaglandin F2alpha, when injected subcutaneously into wether lambs (10 mg twice weekly) stimulated (P less than .05) plasma GH concentrations after the first injection, but not after 3 weeks of treatment. Changes in plasma PRL or TSH were not observed consistently in the lambs treated chronically with PGF2alpha or TRH. Prostaglandin F2alpha, in the present studies, and PGE1 in previously reported studies (1-3), has been demonstrated to be stimulatory to the secretion of PRL and GH. In contrast, PGA1 and PGB1, which lack an 11-hydroxyl group, failed to influence the secretion of either PRL or GH. It would, therefore, appear that the 11-hydroxyl group is a structural requirement for prostaglandins to influence the secretion of these two hormones in sheep. Treatment with thyrotropin releasing hormone (TRH), alone or in combination with PGF 2alpha, significantly (P less than .05) increased growth rate (average daily gains) while PGF2alpha did not, despite the fact that both compounds exerted similar effects on plasma GH.

PLASMA LIPOPROTEINS OF LAMBS AND SHEEP

The major plasma lipoproteins of the adult sheep were high density lipoprotein (76%) having alpha-mobility on electrophoresis and low density lipoprotein (20%) having beta-mobility. Chylomicrons and very low density lipoproteins were minor constituents (less than 5%). The postabsorptive hyperlipidaemia in suckling lambs is mainly a result of increased concentration of low density and high density lipoproteins although the relative contribution of very low density lipoproteins was increased to 7-15% of the total lipoproteins. The hyperlipiaemia was markedly greater in an intact male lamb than in female or castrated male lambs. In suckling lambs a new lipoprotein (density 1-090 g/ml) appeared in the high density lipoprotein fraction but disappeared before weaning.

Long- and short-term effects on intake of pelleting a roughage for sheep

SUMMARY1. Four groups of eight castrated male lambs, weighing initially about 37 kg, were fed ad libitum for 18 weeks on: C, chopped dried grass throughout; P, pelleted grass throughout; C/P (or P/C), the two forms alternated every 3 weeks; or C + P, both forms on offer.2. Daily dry-matter intake (g/kg W0·75) was 58·2 for treatment C and 814 for treatment P; thus the long-term difference in intake was 40%. However, in the alternated sheep, dry-matter intake was 53·6 g/kg W0·75 for chopped grass and 86·5 g for pelleted; this short-term difference (61%) was significantly greater than the long-term difference. Dry-matter intake for treatment C+P was 84·9 g/kg W0·75; after the first week, chopped grass comprised only 10% of this. Dry-matter digestibility coefficients (%) were: C, 740; P, 61·4 and C+P, 62·0.3. The sheep were killed in week 19 and the dimensions of digestive organs and their contents were adjusted to an animal of 50 kg empty body weight. The weight of the reticulo-rumen was greater for C (1·30 kg) than for P (0·94) or C+ P (1·05), C/P and P/C being inter-mediate (1·15). The water-filled volume of the rumen was proportional to weight, except that C/P (alternated sheep finishing on pelleted grass) had low volumes. Reticulo-rumen fill was greater for C (7·28 kg) than for P (3·97) or C+ P (4·53), P/C (5·90) and C/P (4·34) being intermediate. There were no other significant differences in organs or contents.4. Gains in empty-body weight (g/day) were: C, 112; P, 181; C/P and P/C, 126; C + P, 195.

An investigation of the anabolic effects of androstenedione in young ruminants

SUMMARYThree experiments were carried out to investigate the anabolic effects of androstenedione administered at various levels to female and castrated male lambs in one experiment and to entire and castrated male calves in two other experiments. Significant increases in growth were not effected in normally fed animals but a sex × dose level interaction was detected in female lambs. Under normal husbandry conditions androstenedione appears to have little application in meat production.

A note on the effect of diethylstilboestrol on the performance of lambs

Two trials were undertaken to test the effect of different levels of diethylstilboestrol (DES) on the performance of Egyptian castrated male (wether), male (uncastrated) and female lambs. Ninety crossbred lambs in groups of 10, comprising 30 wethers, 30 male and 30 female lambs were used.

Sterility and Impaired Fecundity in Farm Animals

Herbage intake and production performance of animals are likely to vary between different levels of time grazing pasture because of related changes in foraging behaviour. The effect of restricting pasture access on ingesting behaviour and performance of growing lambs is poorly understood. Thirty-two castrated male Ujumuqin lambs were randomly assigned to the following four treatments: (i) 2-h access to pasture (2H), (ii) 4-h access to pasture (4H), (iii) 8-h access to pasture (8H), and (iv) 12-h access to pasture (12H; control). The lambs began to access pasture at 6:00 h and were removed at 8:00 h, 10:00 h, 14:00 h and 18:00 h for 2H, 4H, 8H and 12H treatments, respectively. All lambs off the pasture were housed and separately fed supplements of concentrate and grass hay. The results showed that ingestive behaviour of lambs was significantly affected by restricting access to pasture. When time at pasture reduced from 12 to 2 h, the proportion of time grazing pasture increased (P<0.001), as did the pasture intake rate (P<0.001), but the proportion of time resting and standing and walking distance decreased (P<0.001). Significant linear relationship was found between supplement and pasture intakes. On average, total feed intake and metabolisable energy intake were unaffected by restricting pasture access, but in July weight gain of lambs clearly increased with less time at pasture. Grazing lambs with supplementation have a good ability to adapt to the restricted grazing schedules through varying their ingestive behaviour. Overall, the results indicate shorter grazing times and higher supplementation in July, with longer grazing times and lower supplementation through August and September is the most efficient to maintain higher lamb growth rates.