Weaning Live Weight Research Articles

Milk consumption and behavior of calves in automated calf feeders as early indicators of weaning liveweight

Modern intensive dairy farming relies on data to aid and prioritize management decisions made on farm. Decisions made early in an animal's life can have lasting effects on welfare, productivity, longevity, and profitability. Precision technology such as automated calf feeders (ACF) allow the customization of feeding programs, but despite this, weaning weights (WWT) vary substantially between calves. This observational study used a 3-yr dataset comprising 1,440 female Holstein Friesian calves at a single intensive commercial dairy farm (Dairy Australia feeding system 5; indoor, total mixed ration) using ACF to (1) determine the variability in WWT (as a proxy of animal performance) of calves within this system; (2) identify the contributing factors responsible for the variation in WWT; and (3) identify potential early management intervention points that could be indicative of the performance of calves at weaning within the system. Calves entered the ACF at 10 d of age with 12 calves per ACF; calves were weighed at birth and weaning using weigh scales. We discovered a large range of calf WWT (41–118 kg/head) at ~60 d of age despite the application of strict uniform management protocols. Our results from modeling showed that WWT was significantly and positively associated with birth weight (BWT), with low BWT calves (<36 kg) achieving an average of 70 kg weight at weaning. In contrast, heavier BWT (>36 kg) calves achieved an average of 82 kg at weaning. Based on calf feeder data, cumulative milk consumption and cumulative unrewarded visits to the feeder, as well as BWT, were identified as indicators of greater WWT as all these were highly significant terms in the model for WWT. Results suggest that quantifying consumption and number of visitations to the ACF at d 5 may allow farmers to identify, with time to intervene, calves underperforming within the feeder or system, therefore increasing their potential for growth. Additionally, this demonstrated that greater milk consumption (>30 kg) and interaction with the feeder up to d 5 in the feeder is more likely to yield a WWT >75 kg, identifying a potential point for management intervention for calves below consumption and interaction thresholds (e.g., by developing alarm systems based on consumption or visitation number).

Five-year old diversified pasture delivers greater lamb liveweight gain than a standard perennial ryegrass-white clover pasture

This study investigated liveweight gain of lambs grazing five-year-old pasture of either Italian ryegrass, red clover and plantain (Diversified) or perennial ryegrass and white clover (Standard). Coopworth lambs were born to either diversified or standard pasture and reared there until weaning in December (early summer). Liveweight gain (LWG) from tailing to weaning was 23% higher in lambs on diversified pasture (0.335 kg LWG/lamb/day) compared to those on standard pasture (0.272 kg LWG/lamb/day). From summer to autumn (December to May), liveweight, pasture mass, botanical composition and nutritive quality was measured as weaned lambs progressed through rotationally grazed paddocks of either diversified or standard pasture. Similar lamb liveweight gain betweenpasture types was observed over summer and autumn, with both groups averaging 0.187 kg LWG/lamb/day. From December to May, dry matter intakes (DMI) and feed conversion efficiencies (FCE) were similar between lambs grazing on either diversified or standardpasture. Average final lamb liveweight off diversified pasture was 4.2 kg higher than off standard pasture. The higher pre-weaning liveweight gain and subsequent greater weaning liveweight off diversified pasture was maintained throughout the summer and autumn.

Productive performance of lambs born in different seasons of the year.

The seasonality in lamb supply challenges the development of sheep production. Increasing the duration of the breeding season, aimed at distributing births throughout the year, enables a constant supply of lambs. However, the birth season can influence their productive performance. The objective was to evaluate the effect of birth season on birth live weight (BW), daily live weight gain from birth to weaning (DWGBW), weaning live weight (WW), and daily live weight gain from weaning to 150 days (DWGW-150) slaughter age, as well as the influence of ewe age and body condition score (BCS), sex of the lamb, and type of pregnancy (single or twin) on these productive indices. The study analyzed production data comprising ten breeding seasons (from 2015 to 2019), 643 matings, and 531 lambs, using binary logistic regression, ANOVA, Tukey's, and t tests. Lambs born in summer exhibited lower productive performance, as evidenced by lower DWGBW (0.22 ± 0.08 kg), WW (18.88 ± 7.82 kg), and DWGW-150 (0.13 ± 0.07 kg). Ewes with prepartum BCS between 3 and 4 gave birth to heavier lambs. After birth, lambs from ewes with BCS between 3 and 4 had a higher DWGBW, while lambs from ewes with postpartum BCS of 1.5 and 2 had a lower WW. Ewes aged 2 to 8 years gave birth to heavier lambs, and ewes aged ≥8 years weaned lambs at a lower weight. After weaning, the weight gain was similar among all age groups. Male lambs had higher DWGBW and WW than female lambs. Lambs from twin pregnancies had lower BW (3.95 ± 1.27 kg), lower DWGBW (0.21 ± 0.08 kg), and lower WW (17.59 ± 8.18 kg). The average lamb mortality rate between lambing and weaning was 12.5%, ranging from 9.8% to 13.9%, with no significant variations between birth seasons. Lambs born in spring and summer needed more anthelmintic treatments than those born in autumn and winter. The production of lambs outside the traditional season is possible; however, the productive performance of lambs born in the summer is lower than that in the other seasons of the year.

Genetic variances and covariances of live weight traits in Charolais cattle by multi-trait analysis.

Live weight traits are economically important for beef cattle production systems. Genetic analysis of live weight traits frequently presents a problem due to animal records, in that matter, not all the animals have complete records as many young animals leave the herd because of sale, transfer to another herd, or culling reasons. Therefore, the use of multi-trait genetic analysis might be of assistance to help overcome any possible loss of information for those animals with incomplete records. In this study, genetic variances and covariances were obtained to estimate genetic parameters for birth (BW), weaning (WW), and yearling (YW) live weights in a registered Charolais beef cattle population using a multivariate model, where a considerable reduction of data from birth weight to year weight was observed. Direct and maternal heritabilities for BW, WW, and YW were 0.50, 0.30, and 0.28, and 0.31, 0.25, and 0.14, respectively. Direct and maternal genetic correlations were negative in all live weight traits. Genetic correlations among direct BW with direct WW and YW were low, while genetic correlations among maternal traits were medium or high (r>0.39). Comparison between univariate and multi-trait models with substantial reduction of information revealed important differences, implying that multi-trait analysis is better for the structure of data allowing a better fitting of genetic effects by covariance among evaluated traits. Results support multi-trait analysis implementation for genetic evaluations for live weight traits of Charolais cattle.

Effects of pre-weaning probiotic treatments on growth performance and biochemical blood parameters of Holstein calves

The present study was conducted to assess the effects of pre-weaning probiotic treatments on growth performance of male Holstein calves. For experimental treatments, 20 male calves were divided into 2 groups as of control and treatment group. Control group calves were supplied with fresh milk daily in two meals without any growth promoting supplement. Together with fresh milk supply, treatment group calves were supplied with additional 2 g probiotics to their morning meal. Throughout 56-day milk-feeding period, live weights (LW) and feed consumptions (FC) of the calves were determined. As compared to the control group, probiotic-supplemented calves had 5.25% higher weaning live weight and 11.4% higher daily live weight gain (P less than 0.05). Probiotic-supplemented calves consumed 2% more feed than the control calves (P&gt;0.05) and had 9.52% better feed conversion ratio than the control group calves (P less than 0.05). Probiotic supplementation did not affect blood biochemical parameters significantly (P less than 0.05), except ALT, triglyceride and iron levels (P less than 0.05). It was concluded that probiotic supplementation during milk-feeding period improved growth performance of experimental Holstein calves.

Relationships between prenatal ewe traits, milk production, and preweaning performance of twin lambs.

There is limited information on factors affecting twin lamb growth before weaning, which limits the options available to farmers to actively manage lamb growth. Data from 2 multiyear experiments involving 402 twin-bearing Romney ewes were used to evaluate the effects of prenatal ewe traits (live weight at mating and set stocking and BCS at mating and set stocking) and combined twin lamb birth weight on ewe milk production and lamb growth from birth to weaning as well as the proportion of variation in twin lamb growth that could be explained by these variables. Additionally, the effect of accumulated ewe milk yield over a 42-d period (MY; Days 0 to 42) and accumulated milk components (protein, fat, and lactose) on twin lamb growth were investigated. The effects of prenatal variables on MY, birth weight, and combined twin lamb live weight gain from Day 0 to 42 (LWG) were inconsistent across the 2 experiments. In addition, prenatal ewe traits ( < 0.05) explained less than 30% of the variation in MY and lamb growth from birth to weaning in both experiments. Combined twin lamb birth weight was positively ( < 0.001) correlated with MY ( = 0.34 and = 0.43 in Exp. 1 and 2, respectively). Combined twin lamb LWG was dependent on ewe MY ( = 0.43 for Exp. 1 and = 0.30 for Exp. 2). Lactose, fat, and milk CP yields explained 47 and 42% of the variation in lamb LWG in Exp. 1 and 2, respectively. Lactose and milk CP yield positively affected ( < 0.05) LWG in Exp. 1 and 2, respectively. Fat yield had a positive relationship with LWG in Exp. 1 and a negative relationship with LWG in Exp. 2. In conclusion, the measured prenatal ewe traits had a minimal effect on milk yield and twin lamb growth to weaning. Milk yield and composition explained the greatest proportion of variation in LWG. This suggests that farmers should select ewes with higher milk yields to maximize twin lamb growth to weaning. However, less than 50% of the variation in LWG and weaning live weight was explained by the measured ewe and lamb parameters. Therefore, further studies are required to determine additional ewe or lamb variables that control variation in twin lamb growth.

Heritability of muscle score and genetic and phenotypic relationships with weight, fatness and eye muscle area in beef cattle

To assess the potential for genetic improvement to help meet the increasing demand for high-yielding beef carcasses, the heritability of muscle score (MS) plus genetic and phenotypic correlations with weight and fatness traits were estimated on 1856 yearlings and 2596 weaners born from 1992 to 2012 in a predominantly Angus herd divergently selected for High/Low MS. In 2005, after noting that some cattle were positive for the 821_del11 myostatin mutation that causes muscle hypertrophy, procedures were modified to create a third group (HighHet) of High animals with one copy of this major gene. This allowed the additive genetic effects of MS to be assessed, and also the effect of the 821_del11 mutation. MS traits were found to be highly heritable (h2 = 56–63%), with an extremely high estimated genetic correlation of 99% between weaning and yearling MS. Estimated genetic correlations of MS with rib eye muscle area (EMA) in weaners and yearlings adjusted for either age or weight were 53–56%. Genetic correlations of MS with other traits were relatively low: liveweight (yearlings 5%, weaners 20%), rump fat (yearlings –7%, weaners 11%), rib fat (yearlings –17%, weaners –3%). Apart from weaning liveweight, the estimated genetic correlations were not significantly different from zero. MS had smaller estimated genetic correlations with fatness and weight traits than EMA adjusted for age. For yearlings and weaners born from 2010 to 2012, large significant differences were evident in MS of High and Low calves (4.5-point difference for yearlings; 3.4 points for weaners, on a 15-point scale) and significant differences in EMA (yearlings 2.5, weaners 1.5 cm2). In addition, the 821_del11 mutation reduced fatness, increased MS by 1.5–1.9 points and increased EMA by 2.8–3.6 cm2. With high heritability, low correlations with weight and fatness in weaners/yearlings, plus other research (Cafe et al. 2012, 2014a) showing no detrimental effect on maternal productivity or meat quality, but improvements in dressing percent, retail meat yield, meat : bone ratio and feedlot feed efficiency, the development of an estimated breeding value for MS could help improve the efficiency and profitability of beef production.

Effect of concentrate supplementation at pasture and inclusion of condensed tannins (Quebracho) in concentrates on lamb performance and faecal egg and worm counts

Two studies were undertaken to evaluate the effect of concentrate supplementation at pasture and inclusion of Quebracho on the performance and faecal egg counts of lambs grazing a perennial ryegrass sward from six weeks of age until 5 months of age or slaughter. In experiment 1, from six weeks of age until weaning, lambs were offered no concentrate (NC), low protein (130 g metabolisable protein (MP)/kg dry matter (DM)) concentrate (LP) or high protein (160 g MP/kg DM) concentrate (HP). From weaning until slaughter, lambs were offered 500 g/day of LP or HP concentrate containing either zero Quebracho (T0) or 80 g Quebracho/kg fresh (T80). Prior to weaning, lambs offered LP or HP concentrate had significantly greater weaning live weights (LW), liveweight gains (LWG) from birth to weaning and reduced age at slaughtered compared to those offered NC ( P < 0.001). Protein level had no effect on lamb performance. Lambs offered NC in the pre-weaning period had higher LWG from weaning to the end of the study relative to lambs offered LP and HP concentrate. In the post-weaning period, protein content of the concentrate had no significant effect on age at the end of the study, LWG from birth to the end of the study or carcass characteristics. There was a significant interaction between protein content and level of tannin inclusion on LWG from weaning to the end of the study. Lambs offered LP/T0 concentrate had lower LWG than those offered LP/T80, HP/T0 or HP/T80 concentrates ( P < 0.01). Pre and post-weaning treatment had no significant effect on Strongyle faecal egg counts or total worm counts in the abomasum or small intestine. In experiment 2, from six weeks of age until slaughter, lambs were offered no concentrate (NC), concentrates containing zero Quebracho (LP/T0), concentrate plus 80 g Quebracho/kg fresh (LP/T80) and concentrate plus 100 g Quebracho/kg fresh (LP/T100). The concentrate contained 130 g MP/kg DM. Relative to NC treatment, concentrate supplementation increased lamb LWG from birth to weaning and from birth to the end of the study and reduced age at slaughter ( P < 0.01). Increasing level of tannin inclusion had no significant effect on lamb performance, faecal egg counts or total worm counts in the abomasum and small intestine. Overall in the study faecal egg counts were low and worm counts taken from slaughtered animals were less than 3000 worms per animal. The results of this work indicate that supplementing lambs with concentrates at pasture improved animal performance, but concentrate supplementation and inclusion of Quebracho had no effect on faecal egg counts.

The effects of lactose inclusion and seaweed extract on performance, nutrient digestibility and microbial populations in newly weaned piglets

A 2 × 2 factorial experiment was conducted to investigate the interactions between 2 different lactose levels (150 g/kg vs 250 g/kg) and the addition of seaweed extract (2.8 g/kg, containing laminarin and fucoidan) derived from Laminaria spp. on growth performance, nutrient digestibility and faecal microbial population in the weanling pig. Two hundred and forty piglets were selected after weaning (24 days of age, 7.6 kg (s.d 0.9 kg) live weight) and blocked on the basis of live weight and within each block assigned to one of four dietary treatments. Piglets offered diets supplemented with seaweed extract had a higher average daily gain (ADG) (0.322 vs 0.281 kg, s.e. ± 0.009) (P < 0.01) and gain to feed ratio (0.669 vs 0.611 kg/kg, s.e. ± 0.019) (P < 0.05) during the entire experimental period (days 0–25) compared with piglets offered un-supplemented seaweed extract diets. Piglets offered high lactose diets had a higher ADG (0.319 vs 0.283 kg, s.e. ± 0.009) (P < 0.05) and average daily feed intake between days 0 and 25 (0.480 vs 0.447 kg, s.e. ± 0.011) (P < 0.05) compared with piglets offered the low lactose diets. The inclusion of seaweed extract increased (P < 0.001) the apparent digestibility of nitrogen (N Dig) and gross energy (GE Dig) and decreased (P < 0.05) faecal E. coli populations compared with un-supplemented seaweed extract diets. Piglets offered the high lactose diets had increased GE dig (P < 0.001), N dig (P < 0.05) and decreased (P < 0.05) faecal E. coli populations compared with piglets offered low lactose diets. In conclusion, the inclusion of either a high dietary concentration of lactose or a laminarin–fucoidan extract increased daily gain and gain to feed ratio of post weaned piglets through an increase in nutrient digestibility and decreased E. coli populations in the gut.

Inbreeding depression in Leccese sheep

Three closed flocks of Leccese sheep reared in southern Italy were used to study the effects of inbreeding on productive and reproductive performances. All the animals were grouped into three classes according to the inbreeding coefficients obtained by their pedigree: the first class included non-inbred animals ( F = 0%); and the second and third classes included inbred animals (0 < F < 10% and F ≥ 10%, respectively). Birth and weaning (40 ± 3 days) live weights of 531 ewe lambs born throughout 2003–2005 were recorded and were investigated throughout 2004–2006 for their fertility, prolificacy and fecundity amounting 1282 observations. Live weights at birth (BW) of lambs in first class ( F = 0) and in second class were statistically not different from each other but these were heavier ( P < 0.01) than those included in third class ( F ≥ 10). The same pattern was observed in live weights at weaning (WW) but the relative values were statistically different only for P < 0.05. Likewise all reproductive traits investigated showed strong decreases related to the increasing inbreeding rate.

Forward creep grazing of lambs to increase liveweight gain and post‐weaning resistance to endoparasites

An experiment was conducted in New Zealand to assess the effect of creep grazing of lambs on their liveweight and resistance to endoparasites. Comparisons included creep versus non‐creep grazing at two herbage allowances and regular an‐thelmintic drenching. Treatments commenced with 6‐week‐old twin reared lambs, and ceased when they were weaned at 13 weeks, with the exception of the drench treatment which continued post‐weaning. Pastures used contained sheep endoparasites. At 8 weeks post‐weaning one lamb from each twin set was slaughtered, remaining lambs were then drenched, and 8 and 9 days later were orally dosed with 180 Trichostrongylus colubriformis L3/kg liveweight each day (averaging 12 650/lamb). Three weeks later these lambs were also slaughtered. Measurements included liveweight, faecal worm egg count (FEC) and adult endoparasite numbers. Neither herbage allowance nor creep grazing affected FEC or adult endoparasite numbers. Fortnightly drenching of creep grazed lambs on the high allowance had no effect on weaning liveweight, but it improved live‐weights post‐weaning. Neither creep grazing, pre‐weaning herbage allowance, nor drenching, affected lamb resistance to endoparasites. Creep grazing and the higher allowance both increased weaning liveweights. The response to creep grazing was highest at the lower allowance, increasing weaning liveweights by 4 kg. Pre‐weaning treatment had no effect on post‐weaning growth rate.

Porcas lactantes alimentadas com dietas contendo silagem de grãos úmidos de milho e ácidos orgânicos

Um experimento foi realizado para avaliar o desempenho de porcas lactantes e suas leitegadas alimentadas com dietas contendo silagem de grãos úmidos de milho com ou sem ácidos orgânicos. Foram utilizadas 15 porcas híbridas em um delineamento de blocos ao acaso com três tratamentos (dieta controle, dieta com adição de 0,5% de ácido benzóico e dieta com adição de 0,5% de ácido fumárico) com cinco repetições cada. As dietas elaboradas com silagem de grãos úmidos de milho com ácido benzóico ou ácido fumárico não alteraram (P&gt;0,05) a espessura de toucinho e o consumo médio diário de ração. O ganho médio diário (0,22kg) e o peso vivo médio ao desmame (6,2kg) dos leitões não diferiram (P&gt;0,05) entre os tratamentos. A adição dos ácidos fumárico e benzóico nas dietas elaboradas com silagem de grãos úmidos de milho não altera os desempenhos de porcas lactantes e de suas leitegadas.

Effects of available nutrition and sire breeding values for growth and muscling on the development of crossbred lambs. 1: Growth and carcass characteristics

The growth and development of 387 crossbred lamb progeny from 9 Poll Dorset sires representing muscle (M), control (C), and growth (G) sire-types was studied. Sires were selected on the basis of their LAMBPLAN estimated breeding values (EBVs) for post-weaning growth (PWWT) and depth of loin muscle (PEMD). Lambs were provided with either LOW or HIGH levels of available grazing nutrition from 10 days of age onwards. Liveweight gain (LWG) throughout the study was less on LOW nutrition than on HIGH nutrition, leading to a 9.5 kg lower weaning liveweight (LW) and a 14.9 kg lower final LW in LOW lambs. After adjustment for final LW, HIGH lambs had significantly greater fat depth at the C-site (approximately 40 mm from the midline over the 12th rib) and tissue depth at the GR site (110 mm from the midline over the 12th rib) than did LOW lambs. This effect was consistent across sire-types. Depth of fat at the C-site was positively associated with the EBV of the sire for fat depth. The improvement in pre-weaning LWG, weaning weight, and final weight of lambs resulting from use of sires with a greater PWWT EBV was dependent upon the level of nutrition. This interaction was identified as different slopes (coefficients) for the regression between PWWT and trait for the 2 nutrition levels, indicating that the expression of the sire’s genetic potential for growth at these times was significantly moderated by nutrition. The additional depth of lamb loin muscle resulting from use of sires of higher PEMD EBV was consistent across both LOW and HIGH nutrition treatments, with 1 mm of PEMD leading to a 0.6-mm increase in loin depth. Other consequences of sires having a high genetic capacity for loin muscle depth were reduced carcass C-fat depth with increasing sire PEMD and a tendency for conformation score to improve with the PEMD of the sire. The wool-growth response to improved nutrition was less in M lambs than in lambs of other sire-types, suggesting a difference in priority for protein partitioning between muscle and wool in lambs differing in genetic propensity for muscle growth.

Acasalamento entre ovelhas deslanadas e reprodutores especializados para corte: desempenho produtivo até a desmama

O presente experimento foi realizado para avaliar o desempenho produtivo de ovelhas deslanadas do Nordeste do Brasil acasaladas com machos de raças especializadas para corte. Dados de 305 parições oriundas de 134 matrizes dentro de três períodos de monta foram usados para determinar as taxas de desmame e sobrevivência das crias, o peso vivo ao desmame e o peso vivo total desmamado por ovelha acasalada. As fêmeas foram acasaladas, em sistema de rodízio de uso dos machos das raças Santa Inês, Hampshire-Down, Ile-de-France, Suffolk e Texel. O peso das crias ao desmame não diferiu entre genótipos. A taxa de desmame foi mais baixa para crias de Suffolk e de Texel, ao passo que crias de Hampshire-Down e Ile-de-France tiveram as taxas de sobrevivência mais baixas. Houve efeito compensatório entre os pesos ao nascer e ao desmame e as taxas de sobrevivência e desmame, de modo que o peso total de cordeiro desmamado não diferiu entre genótipos, à exceção para o grupo F1 de Hampshire-Down, devido à baixa taxa de sobrevivência dos cordeiros (71,4%), se comparado com as crias de Ile-de-France. Os acasalamentos ocorridos durante a estação chuvosa foram responsáveis pela menor produtividade das ovelhas. O desempenho das crias Santa Inês comparou-se ao das raças especializadas para o corte, podendo ser indicada como raça parental em programas de cruzamento com ovelhas deslanadas do Nordeste do Brasil.

Genetic parameters for Australian maternal and dual-purpose meatsheep breeds. III. Liveweight, fat depth and wool production in Coopworth sheep

Heritability was estimated for weaning liveweight of 7030 Coopworth sheep from 10 flocks representing 92 sires by derivative-free restricted maximum likelihood procedures using an animal model. Similar analyses were used for yearling liveweight and greasy fleece weight with over 4000 animals, fat depth on 2184 animals and fibre diameter on 966 animals. The fixed effects of flock-year-management group, sex, birth type, rearing type and age were significant for most traits. Estimates of heritability were 0.45 � 0 - 07 for weaning liveweight, 0.38 � 0.07 for yearling liveweight, 0 28 � 0.05 for greasy fleece weight, 0.18 � 0 08 for fibre diameter and 0.13 � 0.04 for ultrasonic fat depth at the C site. The genetic correlations of liveweights with greasy fleece weight were positive, but close to zero with fibre diameter. The genetic correlation between greasy fleece weight and fibre diameter was 0.422 � 0.25. Fat depth was highly genetically correlated with liveweights at weaning (0.53 � 0.22) and yearling (0.64 � 0- 20) ages, was highly negatively correlated with fibre diameter (-0.55 � 0.28) and had a small positive genetic correlation with greasy fleece weight (0.15 � 0.34).

Genetic parameters for Australian maternal and dual-purpose meatsheep breeds. II. Liveweight, wool and reproduction in Corriedale sheep

Performance of sheep from a large Corriedale stud flock was assessed. Weaning and yearling liveweights, greasy and clean fleece weights, clean fleece yield and average fibre diameter records on approximately 3000 animals representing 64 sires were analysed. Also scrotal circumference of 1009 rams representing 27 sires were analysed. Some 3740 reproduction records over 11 years, for 980 ewes representing 114 sires, were also analysed. Heritability estimates were 0 34 �0.07 for weaning liveweight, 0.132 � 0.04 for yearling liveweight, 0.32 � 0.07 for greasy and 0.29 � 0.07 for clean fleece weights, 0.534 � 0 10 for clean fleece yield, 0-56 � 0 10 for yearling and 0 62 � 0 - 14 for hogget fibre diameters and 0.l5 � 0.11 for scrotal circumference. The genetic correlations between liveweight and fleece weight ranged from 0.13 to 0.34, and those for liveweight and fibre diameter were close to zero. The genetic correlations of scrotal circumference with liveweight and wool traits were positive and moderate. Reproductive performance in the flock was high, with fertility 92% and litter size 1.62, resulting in 148% lambs born and 130% lambs tagged alive of ewes joined. Estimated heritabilities for reproduction traits were 0-03 � 0.02 for lambs born and for lambs tagged, and the component traits, fertility 0 01 � 0 -02, litter size 0.04 � 0.03 and neonatal lamb survival was zero. Lambing date had a heritability of 0.06 � 0.03. Estimates of repeatability ranged from 0-04 � 0-01 for fertility to 0.07% 0.02 for lambs tagged and lambing date. Predicted heritabilities for the average of 3.8 records per ewe generally agreed with those estimated for average ewe lifetime performance, which ranged from 0.02 � 0.08 for fertility to 0.12 � 0.09 for lambs tagged and 0.l3 � 0.09 for lambing date.

Progeny test of ram lambs selected for low ultrasonic backfat thickness or high post-weaning growth rate

Ram lambs were selected from a total of 1206 lambs in 8 industry Coopworth ram breeding flocks. Eight rams were selected randomly (one from each flock), 8 were selected on the basis of a low live weight-adjusted ultrasonic backfat thickness (lean) and 8 for a high post-weaning growth rate (PW gain). Rams from a Coopworth line specially selected and bred for low ultrasonic backfat (lean selection) were also included in the progeny test in which the rams were single sire mated to 1.5 year old Coopworth ewes. Birth and weaning weights were recorded for a total of 474 female and 371 male progeny. The males (progeny of 31 sires) were slaughtered between January and April at an average hot carcass weight (HCW) of 12.56 kg and carcass growth and carcass fatness parameters recorded. The carcass composition data were analysed using the allometric equation by covariance on HCW. The adjusted mean values of carcass water content were significantly higher for the progeny of the lean selection rams (7.58 kg) than forthe other 3 sire classes (7.49, 7.46 and 7.41 for the lean, PW gain and controls respectively) indicating that they were leaner. Other indicators of carcass fatness also revealed marked differences between the sire classes. There were also marked effects of slaughter date with lambs slaughtered earlier being leaner (after adjustment for HCW) than lambs slaughtered later in the season. The results indicate that selection of sires on the basis of ultrasonic backfat thickness or post weaning live weight gain can be expected to result in the production of leaner lamb carcasses.

Genetic variation in testicular diameter in a random-breeding Merino flock

This paper reports estimates of genetic parameters for testicular diameter (TDM) from a random-breeding Merino flock maintained at Trangie, N.S.W. Over a period of 4 years, TDM was measured, generally monthly, on 800 rams from four Merino strains and 14 lines within these strains between weaning (4 or 5 months) and 12 months of age. In 2 of the 4 years TDM was again measured at age 19 months. The between-year source of variation was a highly significant component for all measures of TDM except at 4 and 19 months of age. Differences between strains were significant at some ages with changes of ranking occurring was rams approached 12 months of age. Lambs born as twins and triplets had significantly smaller testes up to 9 months of age while date of birth (6–7 week lambing period) had a significant effect up to and including 19 months of age. Rams born later had smaller testes. Paternal half-sib estimates of heritability of TDM between 6 and 12 months of age were all high, ranging between 0.49 ± 0.14 and 0.69 ± 0.14. AT 4, 5 and 19 months of age lower estimates were obtained (0.45 ± 0.19, 0.28 ± 0.13 and 0.22 ± 0.17, respectively). Genetic correlations between these monthly measures of TDM were generally high (> 0.75) except for those involving TDM at 4 months of age. Although the genetic relationship between weaning liveweight and TDM at 5 months of age was high (0.84 ± 0.18), weaning liveweight was lowly correlated with TDM at other ages (0.11–0.26). Correlations between 12-month liveweight and TDM at other ages were higher (0.51–0.74). AT 12 months of age liveweight and TDM were also highly correlated ( 0.80 ± 0.15).

The influences of nutrition and management on the growth of red deer calves from weaning to 16 months of age

ABSTRACTThe effects of date of weaning, weaning live weight, autumn grazing management and level and pattern of winter nutrition in relation to summer grazing on the live-weight gain of farmed red deer calves to 16 months of age were tested in three experiments.In experiment 1, the effect of two weaning live weights (37 and 46 kg) in September and two levels of autumn and winter nutrition were examined with 48 calves. In October, live-weight gains were positively related to sward height and herbage mass. The calves lost live weight in November. Compensatory live-weight gains of 28 g/day occurred at summer pasture after the low level of winter nutrition. Weaning live weight had a major influence on live weight at 16 months of age.In experiment 2, the effects of maintenance, ad libitum and intermediate treatments were compared using 50 calves given a complete diet in winter. The intermediate treatment consisted of a maintenance followed by an ad libitum level of feeding. Compensatory live-weight gains of 49 g/day occurred at pasture with the intermediate treatment achieving complete live-weight compensation at 16 months of age.In experiment 3, the effect of two weaning dates (19 September and 14 November) on live-weight gain of calves and on the date of subsequent calving of hinds were compared with 34 lactating hinds. There was no difference in live-weight gain of calves between weaning dates but the subsequent calving date was delayed by 8 days from those hinds weaning in November.A management system is advocated with weaning in September, housing in November after grazing sown swards greater than 6 cm, a pattern of a low followed by a high level of nutrition in winter and the summer grazing of sown swards maintained at 4 to 6 cm.

The effects of milk feeding on the pre- and post-weaning growth of calves, and on stomach development at weaning

SummaryThe pre-weaning and post-weaning gain, oaroass production and stomach development of oalves fed four levels of whole milk (8%, 10%, 12% and 14% of live weight daily) was studied in two experiments. Calves had access to pasture at all times and were weaned at 12 weeks. Pre-weaning gain, weaning live weight, and carcass weight at weaning all increased as the quantity of milk increased. At the 14% level, male calves reached heavier weaning live weights and produced heavier carcasses than females. Reticulo-rumen weight, when expressed as a percentage of total stomach weight, was significantly reduced with increased milk feeding. Calves reared on the higher quantities of milk gained more slowly after weaning, this being attributed to their poorer reticulo-rumen development at weaning.