Effect of Nutrient Restriction and Realimentation on Growth and Metabolic Responses of Shorn Suffolk,Gulf Coast Native,and Crossbred Lambs

Growth and plasma hormone and metabolite levels were used to compare the effects of nutrient restriction and realimentation on six Suffolk (S), six Gulf Coast Native, (G) and seven S×G crossbred lambs. Shorn lambs were individually fed a 10% CP diet consisting of 20% cottonseed hulls, 74% ground corn, 1% soybean meal, 3% fish meal, 1.1% oyster shell flour, 0.5% urea, and 0.4% trace mineral salt and vitamin A, D, and E mixture. Lambs were fed at 110% of maintenance, 200% of maintenance, or had ad libitum access to feed during periods 1, 2, and 3, respectively. Each period was 28 d in length. Breed did not affect (P>0.25) weight change during nutrient restriction or realimentation. All lambs lost weight during the first period. The calculated NE_m of weight loss and 10% feed intake above maintenance suggests an 88% increase in maintenance energy requirement at 11.6 ± 0.9°C average temperature. Similar shorn G lambs maintained weight even though fed at 200% of maintenance, suggesting a 99% increase in NE_m. Plasma cortisol was lower (P<0.05) and thyroxine higher (P<0.05) in S than G or S×G lambs. Plasma cortisol levels were stable from d 14 through 42 declining to d 70 and increasing on d 84. Plasma thyroxine, urea N, and NEFA concentrations followed a similar pattern. There were differences between breed in plasma hormone levels but not plasma metabolite or weight change. Maintenance energy requirement of shorn lambs was increased.     

Growth and carcass characteristics and serum growth hormone, prolactin and insulin profiles in Debouillet lambs treated with ovine growth hormone and(or) zeranol

Sixteen Debouillet wether lambs (approximately 3 mo old) were placed indoors in 1.5- x 3-m pens (14 h light:10 h dark) 28 d after weaning. Lambs received no implant or a 12-mg zeranol implant on d-2 (eight lambs/group). Two days later (d 0), animals received either 0 or 2.5 mg ovine growth hormone (oGH, eight lambs/group) s.c. on alternate days for 42 d. Animals had ad libitum access to water, salt, mineral and a pelleted alfalfa diet (16% CP). After 42 d, lambs were slaughtered to evaluate carcass traits, organ weights and femur characteristics. Zeranol by oGH interactions were not detected (P greater than .20). Zeranol increased (P less than .05) BW, improved (P less than .05) feed:gain during the first 20 d and increased (P less than .10) feed intake during the last 22 d of the 42-d trial compared with controls. Carcass characteristics were not altered (P greater than .10) by 12 mg zeranol. Serum insulin and prolactin were elevated (P less than .05), but serum GH was not influenced by zeranol compared with controls. Exogenous oGH decreased feed intake (P less than .10) and improved feed:gain (P less than .05) during the initial 20 d compared with controls, but did not influence (P greater than .20) these variables during the last 22 d of the study. Carcass traits were not influenced (P greater than .10) by oGH. Exogenous ovine GH dramatically elevated (P less than .05) serum GH, but did not affect serum insulin or prolactin (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)     

Different roughage:concentrate ratios with and without liquid residue of cassava for lambs

This aim of this study was to evaluate the intake and apparent digestibility of nutrients, ingestive behavior, blood parameters, and performance of lambs fed two roughage:concentrate (R:C) ratios, with or without liquid residue of cassava (LRC). Forty lambs (19.5?±?1.45 kg body weight) were distributed in a completely randomized 2?×?2 factorial design. The intake of dry matter (1311 g/day) and total digestible nutrients (755 g/day), and the intake (172 g/day) and digestibility (552 g/kg) of crude protein were higher for lambs fed R:C of 40:60. The R:C ratio of 80:20 promoted a higher intake (585 g/day) and digestibility (461 g/kg) of neutral detergent fiber. There was an intake of LRC of 1.37 L/day for lambs fed R:C of 80:20 and 0.42 L/day for lambs fed R:C of 40:60. The lambs fed R:C of 80:20 spent more time in feeding (326 m/day) and rumination (530 m/day). The metabolic profile and performance of lambs were not affected by LRC inclusion. The body weight gain (220 g/day) was higher in lambs fed R:C of 40:60. A roughage:concentrate ratio of 40:60 is recommended for lambs because it resulted in the best performance, regardless of supplementation with liquid residue of cassava.     

Changes in plasma gonadotrophins, 17β-oestradiol,progesterone, prolactin,thyroxine and triiodothyronine concentrations in female Japanese quail (Coturnix coturnix japonica) of a heavy body weight line during photo-induced ovarian growth and regression

1. Simultaneous changes of the width of the cloacal opening and plasma luteinising hormone (LH), follicle stimulating hormone (FSH), 17β-oestradiol, progesterone, prolactin, thyroxine (T₄) and triiodothyronine (T₃) during photo-induced ovarian growth and regression were measured in commercially bred Japanese quail from a heavy body weight line.

2. Somatically mature female Japanese quail were transferred from short days (light:dark 8L:16D) at 10°C to long days (16L:8D) at 20°C, and sexually mature female Japanese quail were transferred from long to short days. All variables were measured at transfer and every five days thereafter (except for a measurement at 12 instead of 10?d) for 35?d.

3. Transfer from short to long days caused significant increases in LH, FSH, 17β-oestradiol, ovary weights and oviduct weights after five days, and in the cloacal opening after 12?d. T₃ decreased after five days, whereas no significant changes were observed in T₄ concentrations. Progesterone and prolactin both decreased after 25 long days.

4. The transfer of quail from long to short days caused significant decreases in LH, FSH, 17β-oestradiol, progesterone, prolactin, ovary and oviduct weights after 12?d and an increase in T₃. There was no significant change in T₄ concentrations. The cloacal opening decreased after 25 short days.

5. These results are the first to show simultaneous changes in gonadotrophins, sex steroids, thyroid hormones and prolactin during photo-induced gonadal growth and regression in female Japanese quail.     

Effects of compensatory growth on some body component weights and on carcass and noncarcass composition of growing lambs.

A trial was conducted in 1983 and repeated in 1984 to measure effects of restricted feed intake and realimentation on weights of organs and on carcass and noncarcass composition. A total of one hundred six weaned lambs from two breeds (Timahdit and D'man) and a breed cross (Ile de France x D'man) were used in both years. Lambs were allotted to one of six feed intake regimens: HH (ad libitum access to feed from 21 to 30 kg); HM (ad libitum access to feed from 21 to 26 kg then 70% ad libitum to 30 kg); MH (70% ad libitum from 21 to 26 kg then ad libitum to 30 kg); MM (70% ad libitum from 21 to 30 kg); LH (restricted to lose weight from 21 to 17 kg then ad libitum to 30 kg); and LM (restricted to lose weight from 21 to 17 kg then 70% ad libitum to 30 kg). Weights of visceral organs and mesenteric and kidney fat showed dramatic responses to alteration of feed allowances. After recovery from 20% live weight loss, weight of liver equaled or exceeded that of both the ad libitum and 70% refed lambs. Mesenteric and kidney fat did not. Refeeding was accompanied by an increase in water (P less than .05) and a decrease in fat (P less than .01) of both carcass and noncarcass components. These results indicate that weight loss of lambs incurred during feed shortage was largely in internal organ weights, and that these lambs can recover these losses during realimentation and undergo compensatory growth with better feed efficiency and lean carcasses.     

Effects of feeding ergovaline on lamb performance in a heat stress environment

Lambs exposed to a heat-stressed environment (33 degrees C, 50% relative humidity) were used in three experiments to determine whether ergovaline (EV) is the primary toxin involved in fescue toxicosis. The first study evaluated the effects of feeding diets containing increasing levels of endophyte-infected tall fescue seed (E+) and decreasing levels of endophyte-free tall fescue seed (E-). The second and third study evaluated the response to a diet that contained synthetic EV added to an E- diet and the response to a diet containing endophyte-infected ryegrass seed (R+) with an elevated concentration of EV. In Exp. 1, lambs were fed diets of: 1) 10% E- and 0% E+, 2) 5% E- and 5% E+, or 3) 0% E- and 10% E+. Increasing the percentage of E+ in the diet resulted in a linear decrease (P < 0.01) in feed intake (as-fed basis), skin temperature, thermocirculation index (TCI), and serum prolactin. Body weight gain also decreased (P < 0.06). Respiratory rate and core body temperature were not affected by the 5 or 10% E+ diets. In Exp. 2, lambs were fed diets that contained: 1) 10% E-, 2) 10% E- with synthetic EV added at a level equivalent to the 10% E+ diet, or 3) 10% E+. Feed intake (as-fed basis), body weight gain, and skin temperature did not differ for lambs fed the E- and EV diets. The EV diet elicited a decrease (P < 0.05) in TCI and prolactin compared with the E- diet. The TCI for lambs fed EV did not differ (P > 0.10) from the E+ lambs; however, serum prolactin was lower (P < 0.05) for lambs on the E+ diet than for those fed EV. Core body temperature was not affected (P > 0.10) by feeding EV or E+ fescue seed in Exp. 2. In Exp. 3, lambs were fed diets that contained: 1) 10% E-, 2) 3.24% R+ and 6.76% E-, which added an equivalent amount of EV to E+ diets but reduced concentrations of other ergot alkaloids, or 3) 10% E+. Lambs fed the E+ diet and maintained at 33 degrees C had lowered feed intake (as-fed basis), skin temperature, and TCI compared with lambs fed the E- or R+ diets (P < 0.05). Lambs fed the E+ diet had increased rectal temperatures and lowered serum prolactin compared with lambs on the R+ diet (P < 0.05). Lambs on the R+ diet had a greater rectal temperature and lower serum prolactin than lambs on the E- diet (P < 0.05). These results suggest that EV is a fescue toxin; however, other alkaloids might work synergistically with EV, causing the full expression of fescue toxicosis.     

Immune, growth and carcass responses of ram lambs to active immunization against desulfated cholecystokinin (CCK-8)

This study explored feed intake and carcass responses to active immunization against desulfated cholecystokinin-octapeptide (CCK-8) in ram lambs. Antibody titers 8 wk following primary immunization and booster immunizations given at 4 and 6 wk averaged greater than 1:1,000. Titers increased to greater than 1:10,000 by 16 wk following a final booster immunization at 11 wk. The antibodies developed against desulfated CCK-8 exhibited 29% and 13% cross-reactivities for sulfated CCK-8 and gastrin-17, respectively. Immunization against desulfated CCK-8 had no effect on feed intake, ADG, carcass weight or carcass quality grade. Backfat thickness and carcass yield grade were reduced (P less than .05) by immunization. Organ weights at slaughter, including those of the pancreas and small intestines, were not affected by CCK-8 immunization, with the exception of the lungs, which were 16% lighter (P less than .01) in immunized lambs. In conclusion, active immunization against desulfated CCK-8 resulted in development of high antibody titers against desulfated and sulfated CCK-8. Immunization against CCK-8 decreased fat content of the carcass but failed to affect feed intake, carcass weight or ADG.     

Effects of rearing system on meat quality,fatty acid and amino acid profiles of Hu lambs

To determine the effects of early rearing system on meat quality traits, fatty acid and amino acid profiles of meat, 48 Hu lambs were selected and randomly divided into four treatments: control lambs were ewe‐reared from birth to 60 days of age (ER), while treatment lambs were segregated from their dams at 10, 20 and 30 days of age, then artificially reared with milk replacer until 60 days of age (EW10, EW20 and EW30, respectively). All lambs had no access to the milk replacer or their dams from 61 to 90 days. Creep feed was supplied ad libitum to all lambs from 15 to 90 days of age. Artificially reared lambs (EW10, EW20 and EW30) had higher (p < .05) creep feed intake, average daily gain, slaughter weight, hot carcass weight, meat ether extract content, bright meat color (lightness and yellowness) than ewe‐reared lambs. The content of unsaturated fatty acids and monounsaturated fatty acids in EW10 and EW20 were greater (p < .05) than that in ER, whereas the proportions of saturated fatty acids in EW10 and EW20 were lower than that in ER (p < .05). The percentages of C18:0, C18:2, C18:3 and the ratio of polyunsaturated fatty acids and saturated fatty acids of artificially reared lambs were greater than ewe‐reared lambs (p < .05). The meat proportions of leucine, alanine and proline were higher (p < .05) in artificially reared lambs than ewe‐reared ones. Finally, the artificially reared system increased meat production and changed the fatty acid and amino acid profiles of meat, and it would be appropriate to rear Hu lambs artificially from 10 days with milk replacer.     

Effects of ambient temperature on growth performance and carcass traits of male growing White Pekin ducks

ABSTRACT

1. An experiment was conducted to investigate the effects of ambient temperature on growth performance and carcass traits in male growing Pekin ducks from 14 to 42 d of age in order to establish their optimal temperature requirements.

2. A total of 216 14 d old male White Pekin ducks were allocated randomly to six environmentally controlled chambers with ambient temperature set at 20°C, 22°C, 24°C, 26°C, 28°C, and 30°C from 14 to 42 d of age, respectively.

3. As ambient temperature increased from 20°C to 30°C, the body weight and weight gain decreased linearly or quadratically (P < 0.05) and was accompanied by linearly decreasing feed intake (P < 0.05). According to broken-line regression, the upper critical level of ambient temperature during the growing period for body weight, weight gain, and feed conversion ratio were 27.4°C, 27.4°C, and 26.0°C, respectively.

4. The weight of breast meat, leg meat, and abdominal fat decreased linearly or quadratically as ambient temperature increased and declined to a minimum when the temperature increased to 30°C (P < 0.05). The percentage of breast meat and abdominal fat showed a linear or quadratic decreasing response to increasing temperature, but leg meat percentage increased as temperature increased and reached maximum at 30°C (P < 0.05). According to broken-line regression, the upper critical ambient temperatures during the growing period for breast meat weight and percentage were 25.5°C and 25.6°C, respectively.

5. It was concluded that both growth performance and breast meat of growing ducks were sensitive to increasing ambient temperature and this should be kept below the upper critical temperature during the growing period in order to optimise growth performance and carcass traits at market age.     

Effect of altering nutrient density (concentrate to roughage ratio) and restricting energy intake on rate, efficiency and composition of growing lambs

Two hundred ninety-eight Rambouillet ewe and wether lambs approximately 9 mo old from Texas were allotted to pens (29 to 30 lambs/pen). Two replicate pens were fed each of five diets. Two methods of restricting energy intake were evaluated: altering nutrient density (55% vs 72.5% vs 90% concentrate levels) and restricting intake of the 90% concentrate pelleted diet (92.5% or 85% ad libitum intake). Daily gains were highest with the 72.5% concentrate level and feed efficiency was poorest with the 55% concentrate diet fed ad libitum. Altering nutrient density did not reduce energy intake because lambs compensated by increasing feed intake at the lower nutrient densities. Actual feed intake was 89.5% of ad libitum for the 92.5% of ad libitum intake level and 84% of ad libitum at the 85% of ad libitum intake level due to refusal to consume some fines from the 90% concentrate diet. Feed refusal was greatest for lambs with ad libitum access to feed. Average daily gain was depressed by 8% at the 85% intake level. However, feed efficiency was improved (P less than .01) by 20% when intake was restricted to 92.5% of the ad libitum intake level. Differences in carcass traits were small, but consistent; carcass fat content was reduced slightly by restricting feed intake at constant slaughter weight.     

Potassium and lasalocid effects on performance and digestion in lambs

Two trials were conducted to evaluate effects of dietary potassium (K) concentration and lasalocid (L) in lamb finishing diets. Treatments were arranged in a 2 X 2 factorial and consisted of a 65% concentrate diet with 1.1% K (C), .9% K + 21.3 mg L/kg (CL), 2.1% K (P) and 2.5% K + 20 mg L/kg (PL). In trial 1, 64 fine-wool lambs (initial wt 35.3 kg) were randomly assigned to the four treatments (two pens of four wethers and four ewes/treatment) for a 56-d feeding trial. Average daily gain was not affected by K, but was increased (P less than .10) by L (.23 vs .26 kg/d). Lasalocid tended (P less than .20) to improve feed:gain ratio (5.6 vs 6.3). A K X L interaction (P less than .06) was noted for feed intake, with values of 1.37, 1.45, 1.49 and 1.51 kg X head-1 X d-1 for the C, CL, P and PL groups, respectively. In trial 2, 16 wether lambs (four/treatment fed at 2% of body weight) were used in a site and extent of digestion and nitrogen (N) balance trial, using the same four diets as in trial 1. Site of digestion was estimated from abomasal samples taken at slaughter, with indigestible acid detergent fiber as a marker. Total tract organic matter digestibility was increased (P less than .05) with added K (80.1 vs 76.4%) and L (80 vs 76.4%). Ruminal starch digestibility was not affected by added K, but was decreased (P less than .10) by added L (71.8 vs 88.2%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Dependence of the lactation duration and efficiency on the season of lambing in relation to the prolactin and melatonin secretion in ewes

Changes in day length and the related secretion of melatonin and prolactin are of particular significance in sheep, as they determine reproductive processes, the last stage of which is lactation. The aim of the present study was to examine the dependence of the lactation duration and efficiency on the season of lambing (January—Group I/June—Group II) in relation to the hormonal status of milking ewes (Polish Longwool). The possibility of artificial extension of the milking period in late-lambing ewes by application of prolonged day length, 16 h of light–8 h of darkness (16L:8D), was introduced additionally (Group III). Measurements of plasma levels of prolactin and melatonin were used as parameters of season-dependent hormonal regulation of milk production in this seasonally breeding species. Although during the first 28 days of lactation sheep of all groups produced similar amounts of milk (based on the weight gains of the lambs), our results clearly showed that during the period of machine milking (from weaning at 56 day to the dry period) the level of milk production in Group I was almost twice that noted in Group II. Thus, the highest milk yield was obtained from sheep during the period when the days became longer, i.e. from March to May, which was accompanied by an increase in prolactin secretion. In both groups, melatonin secretion was found to increase while milk performance parameters and prolactin secretion decreased during the shortening photoperiod. The sustained decreases in milk production and prolactin secretion were also observed during the autumn months in sheep from Group III, despite the low level of melatonin. The present study showed that time of lambing and related photoperiod length could significantly affect the milk production of sheep that have a clear season of sexual activity. Maintenance of June-lambing sheep under the 16L:8D regime failed to extend the high prolactin level and lactation considerably into the autumn months. The spontaneous decrease in prolactin secretion observed under the long artificial photoperiod indicated for a development of refractoriness, which could also limit the lactation period.     

Feeding behavior and performance of lambs are influenced by flavor diversity

This study determined whether early experiences of sheep with the same feed, but presented in multiple or single flavors, would influence intake, the profile of hormones involved in feed intake regulation, and the subsequent acceptability of novel feeds. Thirty-five 2-mo-old lambs were randomly assigned to 5 treatments (7 lambs/treatment). Lambs in 1 treatment (the diversity treatment) were simultaneously fed an unflavored plain ration of alfalfa (control) and barley (75:25; as-fed basis) and the same ration mixed (0.2%) with 1 of 3 flavors: 1) sweet, 2) umami, or 3) bitter. The other 4 treatments (monotonous diets) received only 1 of the 4 rations. All animals were fed their respective rations from 0800 to 1600 h for 60 d. On d 55, intake was recorded every 30 min for 8 h. On d 58, blood samples from lambs were collected at 1 h prefeeding and at 30, 60, 210, 300, and 540 min postfeeding. Preference tests were conducted by simultaneously offering novel feeds: 1) high-energy feed, 2) high-protein feed, 3) beet pulp mixed with phytochemicals, or 4) low-quality feed. Lambs in the diversity treatment consumed more feed than did lambs in the other treatments (P < 0.001). Lambs in the diversity treatment consumed equivalent amounts of plain and umami feeds, with a greater amount (P < 0.001) of the umami feed being consumed than the bitter and sweet feeds. Lambs in the diversity treatment tended to grow faster than did lambs in the other treatments (P=0.06). On d 55, lambs in the diversity treatment showed decreased (P < 0.05) feed intake compared with lambs in the other treatments during the 2 peaks of food consumption (30 and 270 min from feeding) and showed a trend for the least plasma concentrations of ghrelin (P=0.06). In contrast, lambs in the diversity treatment consumed more feed than did lambs exposed to monotonous flavors at 60, 90, 120, and 180 min from feeding (P < 0.05). Lambs in the diversity treatment also showed the least concentrations of cholecystokinin and glucagon-like peptide 1 (P < 0.001). There were trends for the greatest concentrations of leptin (P=0.14) and IGF-1 (P=0.16) in the diversity treatment, and for the least concentration of leptin in the bitter treatment (P=0.14). Previous experience with flavored feeds affected the preference of lambs for high-energy and low-quality feeds, and for beet pulp mixed with phytochemicals (treatment × feed × day effect; P < 0.05). Thus, exposure to diverse flavors has the potential to increase feed intake and induce a more even consumption of feed across time by reducing peaks and nadirs of intake compared with exposure to monotonous rations. Flavor diversity may also influence the initial acceptability of and preference for novel feeds.     

Growth performance and physiological parameters of conventional and specified pathogen‐free rats fed autoclaved diets with different protein sources

The effects of feeding autoclaved commercial SSNIFF (SN) diet and diets containing soya bean (S) and casein (C) to growing conventional (CON) and specified pathogen‐free (SPF) rats were determined. Diets S, C and SN, autoclaved at 121 °C during 20 min (T1), at 134 °C during 10 min (T2) and non‐autoclaved (T0), were fed during four weeks, each to 8 CON males and 8 females of mean initial body weight 56 g, kept individually. Diets S, C and SN, autoclaved at T1, were fed during two months, each to 20 SPF males and 20 females of mean initial body weight 58 g, kept in group of 5 animals per cage. In CON rats, autoclaving did not affect feed intake and weight gain, decreased thyroid and stomach weight, increased caecal tissue and digesta weight, and concentrations of isobutyric, isovaleric and valeric acid in caecal digesta. Among biochemical blood parameters, autoclaving decreased only total protein concentration and aspartate aminotransferase activity. Feeding C diet resulted in lower feed intake and weight gain in CON and SPF males. Diet affected organ weights and the greatest differences were found in rats on SN diet for weights of stomach, caecum and female reproductive organs. Diet affected concentration of all short‐chain fatty acids, pH and weight of caecal digesta, the most important being the greatest butyric acid concentration on SN diet and isoacids on C diet. It is concluded that autoclaving of both soya‐containing and soya‐free diets does not affect negatively animal performance and physiology.     

The influence of photoperiod on body weight gain, body composition, nutrient intake and hormone secretion

Increasing daily light exposure from 8 to 16 h increases average daily body weight gains of sheep and Holstein cattle but reduces gains of white-tailed doe fawns. Some of these effects on average daily gain in sheep are the result of increased gut fill and pelt weight. Increasing daily exposure to light increases feed intake when sheep or cattle are fed ad libitum. However, increased feed intake is not a prerequisite for the anabolic effects of long duration exposures to light because increased growth occurs in the animals given 16 h light:8 h dark (16L:8D) even when feed intake is restricted. The anabolic effects of increased duration photoperiods in sheep are independent of the gonads, whereas in cattle they are dependent on the gonads. Consistent increases in average daily gains of cattle in response to longer duration photoperiods have not always been achieved. The lack of consistency may be associated with sexual maturity or rate of fattening of the animal. For example, the stimulatory effects of 16L:8D photoperiods on live weight gain are not readily manifested in immature prepubertal heifers, but occur primarily during the peripubertal period. Short days are conducive to deposition of fat, which may account for the stimulatory effects of short days on live weight gain of white-tailed doe fawns and excessively fattened Holsteins. In contrast, long duration photoperiods stimulate protein accretion in cattle. The hormonal signals that mediate the anabolic effects of increasing exposure to light are not associated with change in insulin, thyroxine or growth hormone concentrations in the blood. Glucocorticoid concentrations in serum decrease with longer duration photoperiods which is consistent with an anabolic effect. Increasing daily light exposure to 16 h/d hastens the increase in concentrations of progesterone and testosterone in sera of peripubertal heifers and prepubertal bulls, respectively. Thus, change in secretion of reproductive hormones in the peripubertal period of cattle may be associated with the anabolic effects previously described and is consistent with gonad dependency. Prolactin concentrations in serum increase in sheep and cattle as duration of light exposure increases. But, there is no irrefutable proof that prolactin is responsible for the increased rates of gain or change in carcass composition associated with longer exposures to light. Thus, the hormonal mechanisms involved in photoperiod-induced alterations in growth remain to be established.     

Effect of age and body weight at photostimulation on the sexual maturation of broiler breeder pullets transferred from 8L:16D to 16L:8D

1. In two trials, broiler breeders were grown to a mean body weight of 2.0 to 2.2 kg at 20 weeks on 8L:16D and transferred to 16L:8D at various ages between 69 and 175 d of age at mean body weights varying between 1.0 and 2.7 kg. Other groups were grown to have a mean 20-week body weight 0.87, 1.15, 1.25 or 1.37 of the normal birds and photostimulated simultaneously with the normal weight birds. Controls were held on 8L:16D in each weight group. In a third trial, broiler breeders were transferred from 8L:16D to 16L:8D at 45 (ad libitum fed), 75 or 90 d (mild feed control), when the mean body weight of each group had reached 2.1 kg. Controls weighing 2.0 kg at 20 weeks were held on 8L:16D or 16L:8D. 2. In trial 1, photostimulating normal weight birds at 69, 76, 83 or 97 d delayed maturity and widened the spread of individual maturities, whilst transferring to 16L:8D at 111 or 125 d advanced maturity. Increasing the mean 20-week body weight to 2.8 kg advanced maturity in birds transferred to 16L:8D at 97, 111 or 125 d. Birds photostimulated at 69, 76 and 83 d matured at a similar age to controls held on 8L:16D. 3. In trial 2, transferring normal weight birds to 16L:8D at 91, 112, 133, 147, 161 or 175 d advanced maturity. Reducing the 20-week mean body weight to 1.91 kg delayed maturity in birds photostimulated at 91 or 112 d, but advanced it in birds photostimulated at 112, 133, 147, 161 or 175 d. Sexual maturity was similar for birds with a 20-week mean body weight of 2.54 or 2.74 kg, with advances for all groups photostimulated between 91 and 175 d. 4. In trial 3, birds maintained on 16L:8D matured later than birds held on 8L:16D, but maturity was advanced when birds were transferred to 16L:8D at 45, 75 or 90 d at a common body weight of 2.1 kg.     

Effects of apple pomace‐mixed silage on growth performance and meat quality in finishing pigs

We measured the growth performance and meat quality of 10 crossbred (Yorkshire × Duroc × Landrace) neutered male pigs to evaluate the effects of apple pomace‐mixed silage (APMS). The pigs were divided into two groups and were respectively fed the control feed and the AMPS ad libitum during the experiment. No difference was found in the finished body weight, average daily gain, carcass weight, back fat thickness or dressing ratio between the control and the AMPS treatments, but average dairy feed intake (dry matter) was significantly lower and feed efficiency was significantly higher using the APMS treatment (P < 0.05). With regard to meat quality, the APMS increased the moisture content but decreased the water holding capacity (P < 0.05) compared with the control treatment. Furthermore, the APMS affected the fatty acid composition of the back fat by increasing linoleic acid (C18:2n6), linolenic acid (C18:3) and arachidic acid (C20:0) levels, while decreasing palmitic acid (C16:0), palmitoleic acid (C16:1) and heptadecenoic acid (C17:1) levels, compared with the control treatment. These results indicate that feeding fermented apple pomace to finishing pigs increases the feed efficiency and affects the meat quality and fatty acid composition of back fat.     

Effect of dietary energy level on the performance of individually housed early-weaned piglets in relation to environmental temperature

An experiment involving 72 individually housed piglets was conducted to determine the interactive effects of environmental temperature and dietary energy level on the performance of early-weaned piglets maintained for six weeks in environmental temperature of 28, 22 or 16°C. Two diets were formulated to supply 3.1 (low energy diet) and 3.6 (high energy diet) Mcal digestible energy per kg of feed.The high-energy diet had greater (P < 0.01) energy and nitrogen digestibility than the low-energy diet. Digestibilities were similar in piglets exposed to 22 and 28°C and higher (P < 0.05) than in those housed at 16°C. Exposure to a low temperature (16°C) increased feed intake by 8% (P < 0.05) and feed to gain ratio by 11% (P < 0.01), whereas exposure to a warm environment (28°C) decreased feed intake by 25% (P < 0.01) and growth rate by 28% (P < 0.01) compared with piglets housed at thermal neutrality (22°C). The effect of dietary energy level on the rate of weight gain, DE intake and DE to gain ratio was dependent upon environmental temperature in which piglets were maintained. Compared with the high-energy diet, the low-energy diet depressed DE intake by 9.2% (P < 0.05) and rate of weight gain by 14.1% (P < 0.01) and increased DE to gain ratio by 5.5% (P < 0.05) in piglets housed in the warm environment. Under cold conditions both low and high energy diets resulted in similar DE intake, rate of weight gain and DE to gain ratio.     

Level of nutrition and visceral organ protein synthetic capacity and nucleic acid content in sheep.

Thirty-two crossbred wether lambs were assigned to a feed intake level of either ad libitum (ADLIB) for maximum rate of growth or restricted to maintain body weight (MAINT) throughout a 21-d period. At 7-d intervals (d 0.7, 14, and 21), four lambs per treatment were slaughtered to obtain measurements of visceral organ protein synthetic capacity and tissue composition. Protein synthetic capacity was assessed by in vitro [14C]valine incorporation and tissue RNA, DNA, and protein contents. Concentrations of protein and RNA were not significantly affected in most tissues measured. However, for liver, duodenal, and jejunal tissue, DNA concentrations in ADLIB lambs were lower (P less than .05) than in MAINT lambs. Ratios of protein:DNA in most organs were higher (P less than .05) in ADLIB than in MAINT lambs. During the 21-d period, liver and small intestinal protein and RNA mass were higher (P less than .10) in ADLIB than in MAINT lambs, and DNA mass was unaffected. Also during the 21-d period, the average total mass of ruminal protein, RNA, and DNA in ADLIB lambs was higher (P less than .05) than in MAINT lambs. Estimates of valine incorporation and ratios of RNA:protein seemed to reflect protein synthetic capacity of the visceral tissues measured; however, the effect of level of feed intake on these measurements was equivocal. These data suggest that the level of feed intake affected visceral organ mass through changes in cellular hypertrophy.     

Daily rhythm of cortisol, and evidence for a photo-inducible phase for prolactin secretion in nonpregnant mares housed under non-interrupted and skeleton photoperiods

Studies were conducted in anestrous mares to characterize daily rhythms of cortisol in non-interrupted [ambient and 16 h light (L): 8 h dark (D)] and skeleton (10L:4D:2L:8D, 10L:6D:2L:6D and 10L:8D:2L:4D) photoperiods, and to determine if there exists a photosensitive phase for the secretion of prolactin. Neither peak or nadir concentrations of cortisol, nor the time of peak or nadir concentrations differed among photoperiod treatments. Highest concentrations (66 +/- 4.4 ng/ml, mean +/- SE) occurred between 0700 and 0900, whereas lowest concentrations (31 +/- 3.6 ng/ml) were found from 1900 to 2300. Mean daily concentrations of serum prolactin were significantly higher in mares housed under the 16L:8D and the 10L:8D:2L:4D photoperiods as compared with the remaining photoperiod treatments, and were lowest in the ambient photoperiod treatment. The mean daily concentration of prolactin in February among photoperiod treatments was inversely related to the number of days (from December 1) to first seasonal ovulation (r = -.92, P = .027). The results were interpreted to: 1) suggest that mares in the 10L:8D:2L:4D skeleton photoperiod do not phase-shift to interpret the 2-h light pulse as the beginning of their subjective day; and 2) provide further evidence that the photo-inducible phase for both prolactin secretion and the stimulation of seasonal reproductive activity occurs 8 to 10 h following the onset of the dark period (scotophase).