The effect of two different weaning procedures on the growth of pasture-reared Thoroughbred foals in New Zealand

AIM: To identify if there was a significant difference in the average daily liveweight gain (ADG) between Thoroughbred foals weaned using two weaning protocols commonly used in New Zealand.

METHODS: Sixteen Thoroughbred foals were blocked for sex and age, randomly allocated into progressive (187, SD 33 days; three colts, five fillies) or abrupt (182, SD 28 days; four colts, four fillies) weaning groups, and weighed every second day for 2 weeks either side of weaning, then fortnightly from birth to 480 (SD 31) days old. ADG was calculated to examine the short-term (10 days before weaning, 5 and 10 days post weaning) and long-term (0–6 and 6–16 months of age) effect of the two weaning treatments.

RESULTS: ADG was 1.10 (SD 0.091) kg/day before weaning (0–6 months of age) and 0.59 (SD 0.06) kg/day from weaning to 480 (SD 31) days old. At the start of weaning, liveweights of the progressive and abrupt weaning groups were 276.5 (SD 40.3) kg and 257 (SD 15) kg, respectively (p=0.23). For the 5-day period during weaning, irrespective of treatment, there was a significant decrease in ADG of –0.29 (SD 0.49) kg/day and –0.15 (SD 0.30) kg/day for progressive and abrupt weaning, respectively. There was no significant difference in ADG between weaning methods at any measurement period (short or long term) during and after weaning. However, there was large variation between foals in ADG in the 10 days after the weaning process, which may indicate variation in individual foals' responses to being weaned, rather than the weaning treatment.

CONCLUSIONS: Weaning, irrespective of method, was associated with a decrease in ADG in the first week after weaning. The method of weaning had no effect on post-weaning ADG either short term, 10 days after weaning, or long term up to 480 days of age. Practically, it may be more important to consider maturity and liveweight as criteria for weaning foals rather than age alone.     

Effects of implanting ram and wether lambs with zeranol at birth and weaning on palatability and muscle collagen characteristics.

Thirty-five zeranol-implanted (I) and nonimplanted (NI) ram and wether lambs representing four treatments (implanted rams [IR], nonimplanted rams [NIR], implanted wethers [IW], and nonimplanted wethers [NIW]) were evaluated for meat palatability and muscle collagen characteristics. Rib (longissimus muscle, LM) chops from I lambs were juicier (P less than .05) than rib chops from NI lambs. Chops from IR lambs had more (P less than .05) detectable connective tissue and lower myofibrillar and overall tenderness scores than chops from NIR, IW, or NIW lambs. Warner-Bratzler shear (WBS) values tended to be higher (P = .06) for LM chops from rams than for those from wethers, but WBS values for Biceps femoris (BF) chops were similar (P greater than .05) for rams and wethers. Implanting did not affect (P greater than .05) WBS values. Rams had more (P less than .05) LM heat-labile (soluble, SC), nonheat-labile (insoluble, IC), and total collagen (TC) and a higher (P less than .05) percentage of SC (SC/TC) than did wethers. Soluble collagen, TC, and percentage of SC for the BF were higher (P less than .05) and IC tended (P = .09) to be higher in chops from rams than in those from wethers. Implanting did not affect (P greater than .05) collagen amount or solubility. Serum nonprotein hydroxyproline (NPHP) was higher (P less than .05) in rams than in wethers throughout the feeding period and tended (P = .05) to be higher at slaughter. Implanting did not affect (P greater than .05) serum NPHP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of vitamin A supplementation in young lambs on performance, serum lipid, and longissimus muscle lipid composition

Forty crossbred wethers (BW = 28.7 kg) were used to evaluate the effects on LM lipid composition of diets containing high and low levels of vitamin A. Four treatments arranged as a 2 x 2 factorial with a completely random design were investigated: backgrounding (BG) and finishing (FN) with no supplemental vitamin A (LL); BG with no supplemental vitamin A and FN with high vitamin A (6,600 IU/kg of diet, as fed) supplementation (LH); BG with high vitamin A supplementation and FN with no vitamin A supplementation (HL); and BG and FN with high vitamin A (HH) supplementation. Diets included cracked corn (62.4%), soybean meal (16.0%), cottonseed hull pellets (14.8%), and supplement (7%), and contained <100 IU of vitamin A/kg (as fed) from carotenes before vitamin A was added. During the BG period (d 1 to 56), feed intake was restricted to achieve 0.22 kg of ADG. During the FN period (d 57 to 112), lambs consumed the same diet ad libitum. Lambs were weighed every 14 d, and blood was sampled every 28 d to evaluate changes in serum fatty acids and vitamin A levels. Lambs were slaughtered after 112 d. Lipid composition was determined for liver and LM. There were no treatment differences (P > 0.05) in feed intake, ADG, or final BW. Carcass weights were not affected by vitamin A treatment (P > 0.20), although backfat thickness tended to be different between HL and LL lambs (0.80 vs. 0.64 cm, respectively; P = 0.08). Carcasses from the HH group had greater (P < 0.05) marbling scores than those from the LL group (514 vs. 459) and had 25.8% more extractable intramuscular lipids (3.88 vs. 3.08% for HH and LL, respectively; P < 0.05); the LH and HL treatments were intermediate. Interestingly, the LL group had the greatest increase in serum fatty acids throughout the experimental period (change of 127 vs. 41 microg/g for LL and HH, respectively; P < 0.01). The degree of saturation of fatty acids was not affected by treatment (P = 0.18) in the serum but was affected in the longissimus thoracis fat. Oleic acid increased and linoleic acid decreased in the longissimus thoracis of HH-treated lambs (P < 0.02). These data suggest that increases in total intramuscular lipids may be achieved with high levels of vitamin A supplementation for 112 d in young lambs.     

Variation in the immune status of two Australian pig breeds

Objective To investigate the variation in immune competence of two Australian pig breeds.
Design A panel of immune tests were used to assess breed and sire differences in weaner piglets of Large White and Duroc breeds.
Procedure All piglets were immunised against porcine leptospirosis. Blood samples were taken for studies on lymphocyte phenotypes, mitogenic responses of blood cells and serological analysis.
Results Significantly larger blood leucocyte numbers were found in Large White piglets compared with Duroc piglets after vaccinations. No significant difference in concanavalin A induced blood cell proliferation was found between these two breeds before or after vaccinations. Some significant breed variation in blood lymphocyte phenotypes was found. While the age-related changes of lymphocyte phenotypes were similar for the two breeds, the Large White breed had significantly larger numbers of CD2+ and CD4+ cells than the Duroc breed after the two vaccinations. There were also significant sire effects on CD8+ cells within the Large White breed after the first vaccination. No significant breed difference was detectable in serum IgG concentrations but sire differences within each breed before the primary vaccination were found. The serum antibody response to vaccination against leptospirosis was generally small, and showed no variations due to either breed or sire. No gender effects were found during the entire study.
Conclusion The study demonstrated significant differences in some important immune components of the pig breeds studied. This may in turn indicate the variation in their immune competence or disease resistance. However, further investigation into the heritability and correlation with specific immune responses is required.     

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 4. Morphometric,microscopic and biomechanical properties of the digital tendons of the forelimb

AIM: To determine the weight, volume, density and cross-sectional area (CSA) of the digital flexor tendons, common digital extensor tendon (CDET) and suspensory ligament (SL) of the forelimb of young Thoroughbred horses in early training, and to assess the response to a training programme of known parameters of superficial digital flexor tendon (SDFT) tissue at mid-metacarpal level.

METHODS: The tendons of seven 2-year-old Thoroughbred horses in training were inspected, transected into segments of known length, and compared with those from seven untrained horses matched for age, sex and breed. The weight, volume, density and CSA of each segment, and the crimp angle, histological features, and biomechanical ultimate stress and stiffness of tendon samples from the mid-metacarpal region of the SDFT were determined.

RESULTS: There was no macroscopic evidence of swelling or discolouration in any of the tendon segments or cut surfaces. The volumes of SDFT and CDET segments of horses in the trained group were significantly greater than those in the untrained group (p=0.036 and p=0.039, respectively). A greater increase in volume than weight resulted in a lower density in the SDFT but not CDET in trained compared with untrained horses (p=0.038). CSA of these two tendons was significantly greater in the trained group (p=0.002 and 0.036, respectively), the percentage increase being greater in the CDET than the SDFT. The number of tenocytes at four sites in the mid-metacarpal SDFT region was less in trained than untrained horses (p=0.025). There was no histological evidence of inflammation, and no difference in crimp angle between groups. There was no significant between-group difference in stiffness or ultimate stress of tendon strips.

CONCLUSIONS: Volume and CSA of the SDFT and CDET were larger in trained than untrained horses. The SDFT was less dense in the trained group. Because no evidence of tendonitis was detected and training appeared to have no significant effect on crimp angle or biomechanical properties of tendon strips, the size and density changes were presumed to be adaptive and induced by the training.

CLINICAL RELEVANCE: Although evident in this in vitro study, the detection of adaptive from initial pathological increase in size of the SDFT is likely to be difficult in vivo.     

The effect on creatinine kinase activity of freezing plasma from healthy foals

Abstract

AIM: To assess the stability of creatine kinase (CK) activity in plasma collected from healthy foals and frozen at ?20°C for up to 12 weeks.

METHODS: Samples of venous blood drawn from 25 foals were analysed for CK activity soon after collection, and again after 1 and 12 weeks of freezing at ?20°C.

RESULTS: CK activity decreased (p<0.001) between Week 0 and Week 1 and between Week 0 and Week 12.

CONCLUSIONS AND CLINICAL RELEVANCE: Decreases in CK activity were statistically significant but clinically insignificant.