Determining and predicting feed intake in crossbred sheep from weaning until maturity

Access to simple, accurate feed intake models would facilitate decision-making in feedlots as feed costs are a major part of operational expenditure. This study aimed to develop genotype-specific feed intake models for South African feedlot lambs. Four ram and four ewe lambs each of eight genotypes were raised under ideal growth conditions from weaning until 1 year of age. Feed intake and growth were monitored throughout this period. The intake data were then used to fit various models to predict daily feed intake, intake as percentage of body weight, cumulative intake and feed conversion ratio. No satisfactory univariate models could be found for the prediction of daily or percentage intake, but a good fit was found for cumulative intake data (R2 >0.80, P <0.01). The slope parameters of these linear models show a strong correlation (72%) with feed conversion and can therefore also serve as proxies for feed conversion. A model was also developed that can predict feed conversion ratio with a moderate accuracy (R2 =0.5, P <0.05) at a given body weight. The cumulative intake model was deemed accurate and simple enough for practical use.

Multiple-trait and structural equation modelling approaches to infer genetic relationships between tail length and weight traits in Merinoland sheep

Tail docking is routinely conducted in long-tailed sheep breeds to prevent flystrike infections, but it is not in agreement with legal guidelines and animal welfare issues. Selection on short tails is a sustainable alternative in this regard, but side effects on other breeding goal traits are unclear. In consequence, the present study aimed to estimate genetic parameters for tail length (TL) at birth, birth weight (BW), weaning weight (WW) and postweaning weight (PWW) at the slaughtering date considering single-trait (STM), multiple-trait (MTM) and structural equation models (SEM) with different random effects, and accordingly, different covariance structures. The SEM considered time-lagged recursive relationships among response variables in three different pathways. The first path pertained to the effect of TL on WW and of WW on PWW. The second path reflected the effect of BW on WW and of WW on PWW. The third path was the recursive effect of TL on PWW. The phenotypic data consisted of 2803 records for TL, 13,042 records for BW, 1556 records for WW and 3986 records for PWW from Merinoland lambs. Lambs were born in the period from 1995 to 2021 and kept at the university Gießen research station, Germany, with their naturally long tails. Genetic statistical model evaluation based on Bayesian and Akaike's information criteria suggested models simultaneously considering direct genetic, maternal genetic and maternal permanent environmental effects and respective covariances. For statistical models including the same random effects and covariance structures, SEM were superior over MTM. The direct heritability for TL from the best-fitting STM was 0.60 ± 0.08, indicating the potential for genetic reduction of tail length within a few generations. For growth traits, the direct heritabilities ranged from 0.16 ± 0.03 for BW to 0.31 ± 0.09 for PWW. The maternal heritabilities were 0.03 ± 0.03 for TL, 0.12 ± 0.02 for BW, 0.04 ± 0.03 for WW and 0.07 ± 0.03 for PWW, reflecting small, but the non-significant influence of uterine characteristics on the tail development. The direct genetic correlations between TL and all weight traits were positive and very similar to MTM and SEM but reflected antagonistic genetic relationships from a breeding perspective. Oppositely, the structural equation coefficients reflecting trait associations phenotypically were negative (favourable) for the time-lagged effects of TL on WW and on PWW. As an explanation, lambs with long and woolly tails have an increased risk for contamination with dirt and dust causing infections, which in turn impairs the body weight development. In conclusion, breeding on short tails should consider trait-associated environmental risk factors, for example, disease susceptibility, which can be mimicked via SEM approaches.

Pre-weaning performance and commercial growth curve in Dorper, Katahdin, and Romanov crossed lambs in a highland zone from central Mexico

The aim was to evaluate the pre-weaning productive performance and growth curve of Dorper*Katahdin (DPr; n = 46), Kathadin*Kathadin (KTn; n = 204) and Romanov*Kathadin (RMv; n = 40) of commercial crossed lambs from central Mexico. We considered 1450 data from 290 crossbred lambs. The variables contemplated in this study were cross (CR), lambing type (LT), sex, birth weight (BW), weaning weight (WW), test days (TD), and daily weight gain (DWG). Correlation analysis and adjustment of growth curve were performed. Differences in CR and sex were found only in BW (p < 0.05). No differences in DWG, WW, and TD (p > 0.05) by CR and sex were found. Single lambing had the highest (p < 0.05) BW, WW, and DWG. Phenotypic correlations differ among crosses. Lambs crossed with DPr presented the highest values in parameters a and b and the lowest in c. The productive behavior of DPr, KTn, and RMv cross with KTn lambs in central Mexico is similar in the pre-weaning period; however, the growth curve and parameters that characterize it suggest that DPr lambs show a tendency to enhance productive behavior in this period.

Growth performance and carcass traits of purebred and crossbred fattening lambs from Ghezel ram with Grey Shirazi ewe

In this investigation, performance, feed efficiency, and carcass traits of 48 weaned crossbred Grey Shirazi × Ghezel and purbred Grey Shirazi fattening lambs (mean live weight (LW), 28.5 ± 0.5 kg and age, 115 ± 5 days) were evaluated. Lambs were divided into 4 groups contain the GM group (12 purebred male lambs of Grey Shirazi ewe × Grey Shirazi ram), the GF group (12 purebred female lambs of Grey Shirazi ewe × Grey Shirazi ram), the CM group (12 crossbred male lambs of Grey Shirazi ewe × Ghezel ram), and the CF group (12 crossbred female lambs of Grey Shirazi ewe × Ghezel ram). The dry matter intakes (DMIs), average daily gain (ADG), and carcass traits in the lambs were determined. The DMI was greater in CF lambs compared to GF lambs (P < 0.001). Feed conversion ratio (FCR) was higher in male lambs comparing to female lambs (P = 0.001). The final body weight (FBW), ADG, live weight at the slaughtering, and hot carcass weight (HCW) were lower in GF lambs compared to another lambs (P < 0.0005, P = 0.002, and P = 0.0007, respectively). Cold carcass weight (CCW) in CM lambs was higher than in other groups. The Longissimus lumborum (LL) area was higher in crossbreed male lambs (P = 0.001). Crossbreeding improved grow performance (FBW and ADG) in male and female lambs. Carcass trait was improved by crossbreeding especially in male lambs. Sex effect on growth performance and carcass traits was noticeable and male lambs had superior growth.

Analysis of multivariate relations among birth weight, survivability traits, growth performance, and some important factors in Suffolk lambs

Abstract. The aim of this study was to describe the relationships among lambs' birth weight, survivability traits, growth performance, and selected factors in Suffolk lambs kept under a specified extensive management system. Data were collected regarding 1012 Suffolk lambs born during a 3-year period (2012–2014) in one flock. Statistical analyses were conducted using the SAS and CANOCO program software. Birth weight was found to be an important factor influencing survivability and growth performance traits. Lambs with too low a birth weight (< 2.9 kg) had the worst results of practically all the survivability and growth performance traits. A significantly lower percentage of live-born lambs (5.2 to 6.1 %; P < 0.05) was also observed amongst overweight lambs at birth (> 6.0 kg) compared to lambs with a birth weight of 4–5.9 kg. Generally, the highest results of growth performance traits were detected in groups of lambs with a birth weight of 5.0–5.9 and 6.0–9.0 kg. Therefore, the optimal birth weight of Suffolk lambs was in the range of 5.0 to 5.9 kg in the evaluated flock management system. Litter size was found to be the dominant factor influencing birth weight, survivability, and growth performance traits, such that singles tended to have the highest birth weight and growth performance traits, while higher survivability traits were found in twins. The results of multivariate relations also clearly indicated that the selection of lambs should be focused on twins with regard to the monitoring of mature ewes' live weight at mating, which helped to improve the lambs' survivability traits, in particular. The monitoring of ewes' mature live weight at mating should also serve as a tool for flock management to shorten the lambing period in the flock and to improve the birth weight and growth performance traits of lambs. The mature ewe body condition score at mating should be monitored to ensure that lambs are adequately meaty and fatty. This study confirmed the importance of keeping records of birth weight and suggested practical implications of some important factors when improving flock profitability.