Jean-Luc Gourdine

Adaptation to hot climate and strategies to alleviate heat stress in livestock production

Despite many challenges faced by animal producers, including environmental problems, diseases, economic pressure, and feed availability, it is still predicted that animal production in developing countries will continue to sustain the future growth of the worlds meat production. In these areas, livestock performance is generally lower than those obtained in Western Europe and North America. Although many factors can be involved, climatic factors are among the first and crucial limiting factors of the development of animal production in warm regions. In addition, global warming will further accentuate heat stress-related problems. The objective of this paper was to review the effective strategies to alleviate heat stress in the context of tropical livestock production systems. These strategies can be classified into three groups: those increasing feed intake or decreasing metabolic heat production, those enhancing heat-loss capacities, and those involving genetic selection for heat tolerance. Under heat stress, improved production should be possible through modifications of diet composition that either promotes a higher intake or compensates the low feed consumption. In addition, altering feeding management such as a change in feeding time and/or frequency, are efficient tools to avoid excessive heat load and improve survival rate, especially in poultry. Methods to enhance heat exchange between the environment and the animal and those changing the environment to prevent or limit heat stress can be used to improve performance under hot climatic conditions. Although differences in thermal tolerance exist between livestock species (ruminants > monogastrics), there are also large differences between breeds of a species and within each breed. Consequently, the opportunity may exist to improve thermal tolerance of the animals using genetic tools. However, further research is required to quantify the genetic antagonism between adaptation and production traits to evaluate the potential selection response. With the development of molecular biotechnologies, new opportunities are available to characterize gene expression and identify key cellular responses to heat stress. These new tools will enable scientists to improve the accuracy and the efficiency of selection for heat tolerance. Epigenetic regulation of gene expression and thermal imprinting of the genome could also be an efficient method to improve thermal tolerance. Such techniques (e.g. perinatal heat acclimation) are currently being experimented in chicken.

A meta-analysis of the effects of high ambient temperature on growth performance of growing-finishing pigs

High ambient temperature (T) is one of the most important climatic factors influencing pig performance. Increased T occurs sporadically during summer heat waves in temperate climates and year round in tropical climates. Results of published experiments assessing the effects of high T on pig performance are surprisingly variable. Thus, a meta-analysis was performed to aggregate our knowledge and attempt to explain differences in the results across studies on the effect of increased T on ADFI and ADG in growing-finishing pigs. Data for ADFI and ADG were extracted from 86 and 80 trials, respectively, from articles published in scientific journals indexed in PubMed, Science Direct, and from proceedings of scientific meetings through November 2009. Data on ADFI and ADG were analyzed using a linear mixed model that included the linear and the quadratic effects of T and BW, and their interactions as continuous, fixed effects variables, and the trial as a random effect factor (i.e., block). In addition, the effects of housing type (2 levels: individual and group housing) and the year of publication (3 levels: 1970 to 1989, 1990 to 1999, and 2000 to 2009) on the intercept and the linear regression term for T (i.e., the slope) were also tested. Results showed that high T had a curvilinear effect on ADFI and ADG and that this effect was more pronounced in heavier pigs. Across T, ADFI was less when pigs were group-housed. The intercept and the regression coefficient (slope) for T were significantly affected by the year of publication. The effect of increased T was greater in more contemporary works, suggesting that modern genotypes could be more sensitive to heat stress than older genotypes of lesser growth potential. In conclusion, pig performance decreases at an accelerating rate as T is increased. The large between-study variability on the effects of high T on pig performance is partially explained by differences in pig BW and to a lesser extent by the year the study was published.

Effect of temperature on thermal acclimation in growing pigs estimated using a nonlinear function

Ninety-six Large White growing barrows were used to determine the effect of temperature on thermoregulatory responses during acclimation to increased ambient temperature. Pigs were exposed to 24°C for 10 d and thereafter to a constant temperature of 24, 28, 32, or 36°C for 20 d. The study was conducted in a climate-controlled room at the INRA experimental facilities in Guadeloupe, French West Indies. Relative humidity was kept constant at 80% throughout the experimental period. Rectal temperature, cutaneous temperature, and respiratory rate were measured [breaths per minute (bpm)] 3 times daily (0700, 1200, and 1800 h) every 2 or 3 d during the experiment. The thermal circulation index (TCI) was determined from rectal, cutaneous, and ambient temperature measurements. Changes in rectal temperature, respiratory rate, TCI, and ADFI over the duration of exposure to hot temperatures were modeled using nonlinear responses curves. Within 1 h of exposure to increased temperature, rectal temperature and respiratory rate increased by 0.46°C/d and +29.3 bpm/d, respectively, and ADFI and TCI decreased linearly by 44.7 g•d(-2)•kg(-0.60) and 1.32°C/d, respectively until a first breakpoint time (td(1)). This point marked the end of the short-term heat acclimation phase and the beginning of the long-term heat acclimation period. The td(1) value for ADFI was greater at 28°C than at 32 and 36°C (2.33 vs. 0.31 and 0.26 d, respectively, P < 0.05), whereas td(1) for the TCI increase was greater at 36°C than at 28 and 32°C (1.02 vs. 0.78 and 0.67 d, respectively; P < 0.05). For rectal temperature and respiratory rate responses, td(1) was not influenced by temperature (P > 0.05) and averaged 1.1 and 0.89 d, respectively. For respiratory rate and rectal temperature, the long-term heat acclimation period was divided in 2 phases, with a rapid decline for both variables followed by a slight decrease (P < 0.05). These 2 phases were separated by a second threshold day (td(2)). For rectal temperature, td(2) increased significantly with temperature (1.60 vs. 5.16 d from 28 to 36°C; P < 0.05). After td(2), the decline in rectal temperature during the exposure to thermal challenge was not influenced by temperature, suggesting that the magnitude of heat stress would affect thermoregulatory responses only at the beginning of the long-term heat acclimation period. The inclusion of random effects in the nonlinear model showed that whatever the temperature considered, interindividual variability of thermoregulatory responses would exist.

Effect of temperature level on thermal acclimation in Large White growing pigs.

The effect of temperature level (24°C, 28°C, 32°C or 36°C) on performance and thermoregulatory response in growing pigs during acclimation to high ambient temperature was studied on a total of 96 Large White barrows. Pigs were exposed to 24°C for 10 days (days -10 to -1, P0) and thereafter to a constant temperature of 24°C, 28°C, 32°C or 36°C for 20 days. Pigs were housed in individual metal slatted pens, allowing a separate collection of faeces and urine and given ad libitum access to feed. Rectal (RT) and cutaneous (CT) temperatures and respiration rate (RR) were measured three times daily (0700, 1200 and 1800 h) every 2 to 3 days during the experiment. From day 1 to 20, the effect of temperature on average daily feed intake (ADFI) and BW gain (average daily gain, ADG) was curvilinear. The decrease of ADFI averaged 90 g/day per °C between 24°C and 32°C and 128 g/day per °C between 32°C and 36°C. The corresponding values for ADG were 50 and 72 g/day per °C, respectively. The 20 days exposure to the experimental temperature was divided in two sub-periods (P1 and P2, from day 1 to 10 and from day 11 to 20, respectively). ADFI was not affected by duration of high-temperature exposure (i.e. P2 v. P1). The ADG was not influenced by the duration of exposure at 24°C and 28°C groups. However, ADG was higher at P2 than at P1 and this effect was temperature dependent (+130 and +458 g/day at 32°C and 36°C, respectively). In P2 at 36°C, dry matter digestibility significantly increased (+2.1%, P < 0.01); however, there was no effect of either duration or temperature on the digestibility of dry matter at group 24°C and 32°C. RT, CT and RR were measured three times daily (0700, 1200 and 1800 h) every 2 to 3 days during the experiment. Between 28°C and 36°C, RT and CT were lower during P2 than during P1 (-0.20°C and -0.23°C; P < 0.05), whereas RR response was not affected by the duration of exposure whatever the temperature level. In conclusion, this study suggests that the effect of elevated temperatures on performance and thermoregulatory responses is dependent on the magnitude and the duration of heat stress.

Effects of dietary protein level and amino acid supplementation on performance of mixed-parity lactating sows in a tropical humid climate

Eighty-six mixed-parity Large White sows were used to determine the effect of diets with reduced CP content or supplemented with essential AA on 28-d lactation performance under humid tropical climatic conditions. This experiment was conducted in Guadeloupe (West French Indies, latitude 16 degrees N, longitude 61 degrees W) between February 2007 and January 2008. Two seasons were distinguished a posteriori from climatic measurement variables continuously recorded in the farrowing room. The average minimum and maximum ambient temperatures and average daily relative humidity for the warm season were 20.5 and 28.2 degrees C, and 93.8%, respectively. The corresponding values for the hot season were 22.7 and 29.4 degrees C, and 93.7%, respectively. The dietary experimental treatments were a normal protein diet (NP), a low protein diet (LP), and a NP diet (NP+) supplemented with essential AA. The NP and LP diets supplied the same levels of standardized digestible Lys (i.e., 0.80 g/MJ of NE), and the NP+ diet supplied 0.95 g/MJ of NE. No interaction between season and diet composition was noted on any response variable evaluated. The ADFI was decreased (P < 0.05) in the hot season (i.e., 3.69 vs. 4.72 kg) and therefore decreased by 500 g per degrees C increase of ambient temperature under high relative humidity conditions. The ADFI tended to be greater with the LP and NP+ diets when compared with the NP treatment (i.e., +10%, P = 0.08). Litter BW gain and mean BW of piglets at weaning were greater (P < 0.05) during the warm season than during the hot season (2.3 vs. 1.8 kg/d and 7.5 vs. 7.1 kg, respectively). Milk production and composition were not affected by dietary treatments but were affected by season (8.1 vs. 6.8 kg/d, for warm and hot seasons, respectively; P < 0.01). The sows fed LP and NP+ diets tended to have decreased backfat thickness losses (3.3 and 3.8 mm, respectively; P > 0.08). In conclusion, the hot season in humid tropical climates, which combines high levels of temperature and humidity, has a pronounced negative impact on performance of lactating sows. Diets with low CP content or supplemented with essential AA can attenuate the effects of hot and humid season by increasing ADFI in lactating sows.

Economic values of body weight, reproduction and parasite resistance traits for a Creole goat breeding goal

A specific breeding goal definition was developed for Creole goats in Guadeloupe. This local breed is used for meat production. To ensure a balanced selection outcome, the breeding objective included two production traits, live weight (BW11) and dressing percentage (DP) at 11 months (the mating or selling age), one reproduction trait, fertility (FER), and two traits to assess animal response to parasite infection: packed cell volume (PCV), a resilience trait, and faecal worm eggs count (FEC), a resistance trait. A deterministic bio-economic model was developed to calculate the economic values based on the description of the profit of a Guadeloupean goat farm. The farm income came from the sale of animals for meat or as reproducers. The main costs were feeding and treatments against gastro-intestinal parasites. The economic values were 7.69€ per kg for BW11, 1.38€ per % for FER, 3.53€ per % for DP and 3 × 10(-4)€ per % for PCV. The economic value for FEC was derived by comparing the expected profit and average FEC in a normal situation and in an extreme situation where parasites had developed resistance to anthelmintics. This method yielded a maximum weighting for FEC, which was -18.85€ per log(eggs per gram). Alternative scenarios were tested to assess the robustness of the economic values to variations in the economic and environmental context. The economic values of PCV and DP were the most stable. Issues involved in paving the way for selective breeding on resistance or resilience to parasites are discussed.

Genetic parameters for thermoregulation and production traits in lactating sows reared in tropical climate.

The objective of this study was to estimate the genetic parameters for thermoregulation traits and the relationships with performance of Large White lactating sows reared in a tropical humid climate. The thermoregulation traits were rectal temperature (RT), cutaneous temperature (CT) and respiratory rate (RR) during lactation measured in the afternoon (1200 h) and in the morning (0700 h). The production traits were sows average daily feed intake (ADFI), litter BW gain (LBWg) and sows proportion of BW change between farrowing and weaning (BWc). Complete data included 931 lactating performance on 329 Large White sows from the INRA experimental unit in Guadeloupe (French West Indies). Random regression models using linear spline functions were used for longitudinal data (RT, CT, RR and daily feed intake). Results showed that when ignoring values at the beginning and the end of lactation, the traits studied can be treated as the same trait throughout days of lactation, with fairly constant heritability and variance. However, largest heritabilities and genetic variances were estimated in mid-lactation. Heritability estimates on average performance during lactation were low to moderate for thermoregulation traits (0.35±0.09 for RT, 0.34±0.12 for CT and 0.39±0.13 for RR). Heritability estimates for production traits were 0.26±0.08 for ADFI, 0.20±0.07 for BWc and 0.31±0.09 for LBWg. Significant genetic correlations between thermoregulation traits and production traits were only obtained for ADFI and RR (0.35±0.12). From this study it can be concluded that thermoregulation traits are heritable, indicating that there are genetic differences in heat stress tolerance in lactating Large White sows.

Selection for residual feed intake in growing pigs: effects on sow performance in a tropical climate.

The aim of the study was to evaluate the consequences of a divergent selection for residual feed intake (RFI) during growth in a temperate environment (TEMP) on sow performance in a tropical environment (TROP). Sows came from a selection experiment conducted at INRA in which 2 lines were selected for larger (RFI(+)) or smaller (RFI(─)) feed intake than predicted from performance. In the first analysis, a subsample of data obtained in TROP conditions (49 lactations) was compared to those obtained in TEMP on their sibs mated with the same boars (54 lactations). In the second analysis, data obtained in the TROP environment (82 lactations) were analyzed for testing the effect of season (warm vs. hot) and line on sow performance. Except for the lactation length, the interaction between line and climatic environment was not significant for the others traits (P > 0.05). The ADFI expressed per kilogram of litter BW gain tended to be higher in the RFI(+) line bred in the TROP environment (P = 0.080), together with piglet BW at weaning, which tended to be lower (P = 0.080). The ADFI was lower in TROP than in TEMP (4.56 vs. 5.86 kg/d; P = 0.003), with negative consequence on litter BW gain and maternal BW loss. The RFI(-) sows tended to eat less feed than RFI(+) sows during lactation (4.55 vs. 5.86 kg/d; P = 0.099). Litter BW at weaning was higher in the RFI(─) line. The RFI(─) sows ate significantly less feed to produce 1 kg of litter than the RFI(+) sows and tended to lose a larger amount of BW during lactation than the RFI(+) sows (2.40 vs. 3.02 kg/kg and -0.66 vs. -0.39 kg/d, respectively, P < 0.10). Whatever the line, ADFI was reduced by about 21% in the hot season (P < 0.05). Litter BW gain was depressed (P < 0.05) in the hot season (1.72 vs. 2.08 kg/d in the warm season; P = 0.023). Lactation maternal BW loss tended to increase in the hot season (1.10 vs. 0.71 kg/d in the warm season; P = 0.016), but back fat loss remained constant (P = 0.295). In the TROP environment, the amount of feed required to produce 1 kg of litter was not influenced by the line in the warm season (2.53 kg/kg on average; P = 0.99), but it tended to be lower in the RFI(─) line when compared to the RFI(+) line in the hot season (2.06 vs. 3.45 kg/kg; P = 0.050). This higher apparent efficiency in RFI(─) sows was mainly related to greater maternal body reserve mobilization (i.e., BW and back fat losses). In conclusion, selection for low RFI during growth in a TEMP environment did not impair sow and litter performance in tropical conditions.

Assessing the risk status of livestock breeds: a multi-indicator method applied to 178 French local breeds belonging to ten species

espanolLa clasificacion de las razas animales segun su nivel de peligro en cuanto a su desaparicion es un elemento de base para un sistema nacional de alerta y de monitoreo de los recursos geneticos. Un enfoque multicriterio ha sido desarrollado para establecer el nivel de peligro de una poblacion animal domestica. En total, se mantuvieron seis criterios: (i) el numero total de hembras reproductoras, (ii) la evolucion de este numero en los cincos ultimos anos, o las cincos generaciones, segun la especie; (iii) la proporcion de cruzamientos; (iv) el tamano efectivo de la poblacion, (v) la organizacion de los criadores y el apoyo tecnico; (vi) el contexto socio-economico. Con el proposito de facilitar la combinacion de estos criterios de tipo diferente, los valores observados fueron convertidos en una escala de 0 (ausencia de amenaza) a 5 (amenaza maxima), la correspondencia entre valores observados y notas siendo especifica por cada criterio. Para cada raza, las notas estan presentadas de forma grafica y una nota de sintesis esta calculada como la media de las seis notas. Este metodo ha sido aplicado a 178 razas locales francesas perteneciendo a diez diferentes especies: ganado, ovino, caprino, cerdo, caballo, asno, gallina, pavo, oca, pato comun. Asi se demostro que la mayoria de las razas locales francesas se pueden considerar como en peligro: todas las razas locales de equido y de cerdo, casi la totalidad de las razas locales de aves de corral, alrededor de 80% de las razas locales de ganado o caprinos y la mitad de razas locales de ovinos. Se discute el interes de este metodo para la definicion de estrategias de conservacion et la elaboracion de politicas publicas. EnglishBreed risk status assessment methods are key components of country-based early warning and response systems. In this study, a multiindicator method was developed to assess the risk status of livestock populations. Six indicators were used: (i) the current number of breeding females; (ii) the change in the number of breeding females over the last 5 years or generations (depending on the species); (iii) percentage of cross-breeding; (iv) effective population size; (v) breeders organization and technical support; and (vi) socio-economic context. To make these indicators comparable, observed values were converted into scores on a six-point scale (from 0 = no threat to 5 = maximum threat); a specific conversion method was used for each indicator. For each breed, the different scores were analysed graphically and an overall score was calculated by averaging the six separate indicator scores. This approach was applied to 178 French local breeds, belonging to ten different species: horse, donkey, goat, pig, chicken, turkey, goose and Pekin duck. A large percentage of local breeds were found to be at risk to be lost for farming, although the results were species dependent. All local equine and pig breeds, as well as almost all local poultry breeds appeared to be endangered. About 80 percent of local goat and cattle breeds, and half local sheep breeds were also found to be at risk. The usefulness of this method with regards to conservation strategies and public policy is discussed francaisLa classification des races animales selon leur statut vis-a-vis d’un risque de disparition est un element-clef d’un systeme national d’alerte et de suivi des ressources genetiques. Une approche multi-indicateurs a ete developpee pour etablir le degre de menace d’une population animale domestique. Au total, six indicateurs ont ete retenus : (i) le nombre total de femelles reproductrices, (ii) l’evolution de ce nombre dans les cinq dernieres annees, ou generations, selon l’espece ; (iii) la proportion de croisement ; (iv) la taille efficace de la population ; (v) l’organisation des eleveurs et l’appui technique ; (vi) le contexte socio-economique. Afin de faciliter la combinaison de ces indicateurs de nature differente, les valeurs observees sont converties sur une echelle de 0 (absence de menace) a 5 (menace maximale), la correspondance entre valeurs observees et notes etant specifique de chaque indicateur. Pour chaque race, les notes sont representees de facon graphique et une note de synthese est attribuee en calculant la simple moyenne des six notes. Cette methode a ete appliquee a 178 races locales francaises appartenant a dix especes differentes : cheval, âne, bovins, ovins, caprins, porc, poule, dinde, oie, canard commun. Il a ete ainsi montre que la plupart des races locales francaises peuvent etre considerees comme menacees : toutes les races locales d’equides et de porc, la quasi-totalite des races locales de volailles, environ 80% des races locales bovines ou caprines, et la moitie des races locales ovines. L’interet de cette methode pour la definition de strategies de conservation et l’elaboration de politiques publiques est discute.

Genotype by environment interaction on growth and carcass traits in beef cattle in the tropics

A wide variety of beef cattle production systems may be found in the tropics, which could be classified as pasture based systems, mixed farming systems, and industrial systems, following the classification by Seré and Steinfeld (1995). In tropical regions, pasture based systems and mixed faming systems are mainly practiced, with different levels of intensification in management. In that context, one major goal for cattle breeders is to match the type of animal they use to the management conditions they apply. In this study, our objective was to investigate the genotype 3 environment interaction (GEI) that may affect growth traits (live weight, average daily gain, yearling weight) and carcass traits (slaughter weight, hot carcass weight, muscular tissue weight, adipose tissue weight and digestive tract weight) expressed across two contrasted systems.