The energy requirements of Holstein-Friesian heifers during rearing and pregnancy under the tropical conditions of Cuba. 1. Determination of dry matter and energy assimilation and of the live weight development and energy expenditure

In an individual feeding experiment with 48 Holstein-Friesian heifers divided into 3 groups, the effect of various energy levels on live weight development and energy expenditure in the age bracket of 97 days (78 kg live weight) to conception (350 kg LW) and from conception to calving (500 kg LW) was investigated. Rations with differing concentrate--roughage ratios were used. The differentiation of energy intake per day between groups 1 and 2 and group 3 amounted to 7.5% in the 1st development period and to 20% between group 1 and groups 2 and 3 in the 2nd development period. There were significant differences in the live weight gain of 95 g/animal and day in the first development period (up to conception) and of 81 g/animal and day in the second period of development (from conception to calving). Under the tropical climatic conditions the energy expenditure in these studies was approximately 10% under the energy expenditure recommended by the NRC (1978). While there was a clear reciprocal relation between energy expenditure and live weight gain in the first period of development, this relation was less distinct in the second period of development.     

Effect of season and breed group on the follicular population and cyclicity of heifers under tropical conditions

The aim was to determine the effect of season and breed group on follicular population, and presence and size of CL of heifers under tropical conditions. The seasons were hot-dry (March–June), hot-humid (July–October), and fresh-humid (November–February). Thirty Zebu (Brahman) and 38 F1 (Simmental?×?Brahman) heifers were used. Five evaluations were made in each season, at intervals of 7 days, to assess ovarian activity by ultrasound. Follicles were classified as small (≤4 mm), middle (4.1–8 mm), and large (≥8.1 mm) sizes, and also the size of CL, when present, was measured. Data were analyzed using analysis of variance and logistic regression procedures. Mean number of small follicles was 11.6?±?2.3 with no effect of season, breed group, or their interaction (P?>?0.05). Mean number of middle follicles was influenced by season and breed group; the highest average was found in the fresh-humid season (4.0?±?0.2) and in F1 heifers (3.6?±?0.2; P?<?0.05). The highest mean number of large follicles was in the hot-humid season (1.4?±?0.1; P?<?0.05). The highest maximum follicle diameter (MFD) mean was registered in the hot-humid season (1.3 mm; P?<?0.05) and the lowest proportion of heifers with CL occurred in fresh-humid season (33.3%; P?<?0.05). No effect of season, breed group, and interaction on the maximum diameter of the CL was found. In conclusion, season was a very important source of variation. Heifers in the hot-humid season had the largest follicles and MFD, and better cyclicity.

     

Growth studies of Holstein-Friesian bulls under different conditions of feeding intensity. 5. Derivation of energy requirement values

From two long-term individual feeding experiments with groups of differentiated feeding intensity, energy requirement values were derived which take into consideration live weight development and which are in accordance with the measurements of nutrient and energy retention. The suggested energy requirement values show big differences between the intensity levels. It follows from this that energy expenditure from a low to a high feeding intensity first decreases and then, at a very high performance, increases again.     

The effect of pregnancy on visceral growth and energy use in beef heifers

Beef heifers (24 mo; 378 +/- 32 kg of BW; 22 pregnant, PR; 17 nonpregnant, NP) were grouped in common pens and fed corn silage- and hay-based diets formulated to provide an ADG of 0.45 kg in NP heifers. Both PR and NP heifers were slaughtered on d 40, 120, 200, and 270 of the study. Intestinal and hepatic tissues were analyzed for protein, DNA, RNA (mg/g of fresh tissue), and in vitro oxygen use. Jejunal samples were analyzed for cellular proliferation via immunohistochemical analysis. For ileum, DNA, which provides an estimate of cell number per unit of tissue, revealed an interaction (P = 0.06) between pregnancy and slaughter day; both PR and NP decreased with time, but NP increased on d 270 (P = 0.09). Cell number in the ileum was reduced at d 200 and 270 in the PR heifers (P < 0.09). Liver protein concentration was less (P = 0.07) in PR than in NP heifers (NP = 291.1 vs. PR = 210.5 +/- 33.9 mg/g). Hepatic protein:DNA ratio was not affected (P > 0.10) by pregnancy or day. Energy use (kcal/d) of duodenum and jejunum, calculated from in vitro oxygen consumption, increased linearly (P < 0.02) with time for both PR and NP. Pregnant and NP ileal energy use increased linearly (P < 0.01), but ileal energy use by PR was less throughout gestation (P = 0.07) than ileal energy use by NP. Cellular proliferation in the crypt region of the jejunum was decreased on d 120 and 200 (P < 0.02). These data indicate that the small intestine and liver of PR heifers may conserve energy expenditure compared with NP heifers. Energy conservation can partially be explained by differences in growth and cell proliferation and by energy use of the liver and small intestine.     

Reliability of estrous detection in Holstein heifers using a radiotelemetric pedometer located on the neck or legs under different rearing conditions

To evaluate the efficiency and accuracy of estrous detection using a new pedometry system that can measure the hourly activity of cattle, pedometers were attached to the neck and the hind legs of 15 Holstein heifers. Heifers were reared in pasture for grazing, an open paddock, or in a tie-stall barn (an additional pedometer was attached to a front leg of each of these heifers). The most recent 24 h-total number of steps was compared for each 1 h-interval with the mean value of the preceding days during the reference period (RP). The neck pedometer detected all 10 instances of estrous activity (100%) for the grazing heifers at 1.3 times the thresholds value for a 5-day RP but with only 32% accuracy. The hind leg pedometer, however, obtained 100% efficiency and 83% accuracy at 1.4 times the threshold value for a 7-day RP. The efficiencies and accuracies in detecting 12 instances of estrous activity under the paddock condition were 92 and 65% (neck, 1.3-fold, 7-day RP) and 92 and 100% (hind leg, 1.6- or 1.7-fold, 7-day RP), respectively. Under the tie stall condition, the neck pedometers detected 92% of 23 instances of estrous activity with 34% accuracy (1.2-fold, 3-day RP), and the efficiencies and accuracies of the leg pedometers were 78 and 78% (hind leg, 1.4-fold, 4- or 6-day RP) and 87 and 83% (front leg, 1.4-fold, 7-day RP), respectively. Prediction of ovulation time was more precisely with the leg pedometers than with those under the tie stall conditions. Our preliminary results indicate that this new pedometer system has practical value for estrous detection in heifers under different rearing conditions, which affect the criteria required for detection. Furthermore, they also indicate that a leg pedometer can reliably detect estrus and that a neck pedometer may only be capable of detecting estrus under paddock rearing conditions.     

Susceptibility of hair sheep ewes to nematode parasitism during pregnancy and lactation in a selective anthelmintic treatment scheme under tropical conditions

The objective was to determine the influence of year, season and age of hair sheep ewes on their susceptibility to gastrointestinal nematodes during pregnancy and lactation and to record the number of treatments within a selective anthelmintic (AH) treatment programme. A trial was performed with 46 grazing ewes kept in hot humid tropical conditions. Data included: average daily weight gain (ADG, kg), packed cell volume (PCV, %) and nematode eggs per gram of faeces (EPG) obtained during 2 years (2009 and 2011–2012). Ewes reaching 1000 EPG were treated with AH. Irrespective of year, season and age, ewes were more susceptible to GIN during lactation (higher EPG, lower PCV and net weight loss) and less susceptible during gestation (lower EPG, higher PCV and net weight gain). As a result, 24.4% of the ewes were left untreated during lactation, while 63.0% of the ewes needed no AH treatment during pregnancy. Even under the hot humid tropical conditions of the farm, the individual EPG helped to maintain a considerable proportion of animals without an AH treatments within the flock.     

The energy requirement of heifers. 4. Comparison of the digestibility and rumen physiologic parameters in heifers and full-grown sheep

In 159 comparative studies with fully grown sheep and heifers of the digestibility and of rumen physiologic values at a variation of the feed ration in the crude fibre content between 112 and 318 g, in the crude protein content between 94 and 194 g and in the content of nitrogen free extractive between 484 and 641 g/kg DM is provided that the digestibility of energy in heifers was, on average, 4 digestibility units lower than in sheep. The corresponding values for the digestibility of crude protein and crude fibre are 12 and 3.5 digestibility units. Due to the lower methane energy excretion of the heifers the difference at the level of metabolizable energy is reduced to 1.5% of the gross energy. The level of the differences in digestibility is influenced by the development of the young cattle and the composition of the rations. In young cattle of the live weight range between 100 and 150 kg the digestibility of the energy is 6-8 units lower than in sheep. A higher crude fibre content in the ration diminishes the difference in the digestibility of energy and the nutrients between the two animal species.     

Effect of varying dietary energy levels during the last trimester of pregnancy on subsequent first lactation performance in Sahiwal heifers

The aim of the study was to determine optimum dietary energy level during the last trimester of pregnancy for Sahiwal heifers in subtropical Pakistan. Sixteen Sahiwal heifers, 5–6 months pregnant, were assigned to four dietary treatments with four heifers on each treatment. Isonitrogenous (CP = 14.1%) diets having varying energy, namely, ME 88%, ME 100% (Control), ME 112% and ME 124% of NRC recommended level for pregnant heifers, were fed until calving. All were fed a similar diet after calving. Precalving weight gain was highest (P < 0.05) in heifers fed ME 112 and 124% (486 ± 13 and 497 ± 5 g/day, respectively) followed by ME 100% (444 ± 7 g/day), and the lowest weight gain was recorded for ME 88% (397 ± 8 g/day). A similar trend was observed for feed efficiency. Body condition score at calving in groups ME 124% and ME 112% was higher than ME 88% and ME 100%. Nutrient digestibility, birth weight of calves and milk composition except fat content were not influenced by energy levels. The highest daily milk yield was observed in heifers fed ME 100% followed by ME 112, 124, and 88%. We conclude that the NRC recommendation is applicable to the subtropical region.     

The evaluation of non-specific immune status of heifers in field conditions during the periparturient period

During the periparturient period, some impairment of immune defences were observed. Reference values for the different non-specific immune parameters in cows are not generally available, thus limiting the application of these parameters in dairy practice. This paper reports the data on the measurements of different parameters in the blood, and explores the possible influence of the herd on the non-specific immune status of the cow. Five herds located in Northern Italy were selected and overall 39 heifers were enrolled in the trial. Blood samples were taken 14 and 7 days before the expected date of calving, then at 7, 14, 21, 28, 45, 60, and 75 days after calving. The parameters assessed were N-acetyl-beta-glucosaminidase (NAGase), lysozyme, nitric oxide, superoxide dismutase, haptoglobin, respiratory burst, and serum protein profile. After calving, a significant decrease of respiratory burst and nitric oxide concentration were observed in comparison with the pre-calving values but not with the post-calving samplings. Total proteins, beta- and gamma-globulins showed a progressive and significant increase in concentration after calving, in comparison with pre-calving values. The results of the study confirmed that a decrease of immune functions can be observed in commercial dairy herds in the first four weeks after calving. The amplitude of this phenomenon is not common to all animals and all herds, suggesting the possibility to reduce the impairment by improved management and genetic selection.     

The effects of metabolizable energy intake on body fat depots of adult Pelibuey ewes fed roughage diets under tropical conditions

The objective of this work was to evaluate the effect of metabolizable energy intake (MEI) on changes in fat depots of adult Pelibuey ewes fed roughage diets under tropical conditions. Eighteen 3-year-old Pelibuey ewes with similar body weight (BW) of 37.6 ± 4.0 kg and body condition score (BCS) of 2.5 ± 0.20 were randomly assigned to three groups of six ewes each in a completely randomized design. Ewes were housed in metabolic crates and fed three levels of MEI: low (L), medium (M), and high (H) for 65 days to achieve different BW and BCS. At the end of the experiment, the ewes were slaughtered. Data recorded at slaughter were: weights of viscera and carcass. Internal fat (IF, internal adipose tissue) was dissected, weighed, and grouped as pelvic (around kidneys and pelvic region), omental, and mesenteric regions. Carcass was split at the dorsal midline in two equal halves, weighed, and chilled at 6°C during 24 h. After refrigeration, the left half of the carcass was completely dissected into subcutaneous and intermuscular fat (carcass fat). Dissected carcass fat (CF) of the left carcass was adjusted as whole carcass. At low levels of MEI, proportion of IF and CF was approximately 50%; however, as the MEI was increased, the proportion of IF was increased up to 57% and 60% for M and H, respectively. Omental and pelvic fat depots were those which increased in a larger proportion with respect to the mesenteric fat depot. Regression equations between the weight of each body fat depot and BW had a coefficient of determination (r ²) that ranged between 0.37 for mesenteric fat and 0.87 for CF. The regression with BCS had a r ² that ranged between 0.57 for mesenteric and 0.71 for TBF. BW was the best predictor for TBF, CF, omental fat, and pelvic fat; whereas, BCS was better than BW in predicting IF and mesenteric fat. Inclusion of both BW and BCS in multiple regressions improved the prediction for all fat depots, except for pelvic fat, which was best estimated by BCS alone. The greater slope of the regression for the pelvic fat depot equation, relative to TBF (1.40), EBW (4.02), and BCS (2.36), suggested that pelvic fat has a greater capacity to accumulate and mobilize fat. These results indicated that adult Pelibuey ewes seem to store a considerable proportion of absorbed energy in the IF depots rather than in the carcass.     

Effect of management factors and blood metabolites during the rearing period on growth in dairy heifers on UK farms

Growth rates during rearing affect the age and body weight (BW) of replacement heifers at first calving. Diet and disease can affect growth via altered metabolic hormone concentrations, but are difficult to monitor accurately on commercial farms. This study investigated the effect of management and metabolic indices (IGF-I, insulin, glucose and urea) on the growth rate of 509 Holstein-Friesian heifers on 19 UK dairy farms. Size (BW, heart girth, height and crown-rump length) was measured at approximately 1, 6 and 15 months. The mean daily weight gain up to 6 months for all calves was 0.77 kg/day, with extreme variability both between cohorts of calves (range 0.49–1.02 kg/day) and between individual calves within farms (range 0.45–1.13 kg/day). Growth was enhanced by supplemental colostrum, by milk replacer as opposed to whole milk and by ad libitum milk feeding and was reduced by gradual weaning and dehorning after weaning. Larger group size slowed growth before weaning (>6 calves) but increased it post-weaning (>20 calves). These management differences were reflected in altered plasma IGF-I concentrations, which were positively associated with growth throughout the rearing period. Larger calves at 1 month had a greater weight gain up to 6 months. Sub-optimum growth of some heifers within each cohort was established at an early age and resulted in animals reaching the start of breeding at an inadequate size (BW range 209–498 kg at 15 months). This could be alleviated by altered management strategies and improved monitoring of growing heifers.     

The energy and protein concentration of broiler rations in Cuba. 3. Male broilers in the summer

A total of 1,900 male broilers of the variety White Plymouth Rock was tested with 4 energy concentrations (10.5, 11.5, 12.6 and 13.6 MJ metabolizable energy/kg) and 4 protein concentrations (15.0, 17.5, 20.0 and 22.5% CP) in their first 56 days of life in 16 test groups. The animals were kept in cages and were directly exposed to the natural Cuban summer temperatures from their 15th day of life onwards. As every test group was run with 6 repetitions, the results could be variance analytically calculated. In a comparison of the behaviour of the male animals in winter and in summer it can be stated that the animals took in between 3.4 and 25% more feed in winter than in summer. In general, a lower body protein and body fat amount could be found in all test groups in summer compared to that in winter. Feed expenditure and the utilization of energy and protein were not as good as in winter. It could be shown that both maximum live weight and live weight gain can be achieved in the 2nd fattening period in the Cuban summer if rations containing 12.6 MJ metabolizable energy and 20% CP are fed in a one-phase feeding system.     

Nutrient dependence of energy conservation requirements in rats. 4. The influence of protein levels of food on energy conservation requirements of rats during growth and after conclusion of the intensive growth phase

Albino rats bred in the institute (Wistar line) divided into 3 groups of 9 animals each received, beginning at the age of 4 weeks, feed mixtures with 10, 40 and 70% protein in the rations over a period of 24 weeks divided into 14 subperiods of study. The feed mixture changed cyclically for the groups of animals after each sub-period. Every period was divided into a growth period (8 days) with the rats kept in metabolism cages and a period of feeding on maintenance level (4 days) with the rats kept in respiration chambers. In both periods the temperature was kept constant at 30 degrees C. On 3 days of feeding on the maintenance level the metabolism parameters of energy, C and N metabolism were measured and energy maintenance requirement was ascertained. Both the energy maintenance requirement of the growing rats (up to 200 g live weight) and that of the nearly fully grown and fully grown rats resp. (greater than 200 g live weight) significantly depended on the nutrient composition of the feed mixtures supplied. It increased with the increasing protein and simultaneously decreasing carbohydrate quotas in the feed. On an average of the studies the rats had, in the sequence of 10, 40 and 70% protein content, an energy maintenance requirement of 383 +/- 31 (n = 105), 415 +/- 31 (n = 106) and 459 +/- 36 kJ metabolizable energy/kg LW0.75.d (n = 102). Energy maintenance requirement behaved relatively like 100:108:120. Based on the fact that energy maintenance requirement may be considered the requirement of ATP, relative expectancy values for energy maintenance requirement can be calculated with the energetic efficiency of the ATP synthesis (kJ metabolizable energy/Mol ATP gain) in nutrient catabolism from the relation of the experimentally ascertained nutrient metabolism at a variant supply of protein of 100:110:118. The hypothesis that the efficiency of ATP synthesis in the catabolism of the main nutrients supplying energy can be considered a relative measure of the dependence of the energy maintenance requirement on nutrient composition has been confirmed in this experiment. Different findings in earlier experiments raise the question if those findings were influenced by adaptation effects. An experimental solution of this question is considered important.     

Influence of different supplements and sugarcane (Saccharum officinarum L.) cultivars on intake, digestible variables and methane production of dairy heifers under tropical conditions

The sulphur hexafluoride (SF(6)) gas tracer method was used to measure methane (CH(4)) production of crossbred (3/4 Holstein x Zebu) dairy heifers fed two types of sugarcane (Saccharum officinarum L.; cultivar IAC-862480 (CC1) or cultivar IAC-873184 (CC2)) and supplemented with urea or concentrate. The study was performed at Embrapa Southeast Cattle, S?o Carlos, SP, Brazil, using a completely randomised design. Differences between treatments were significant for digestibility of dry matter, organic matter and energy. When animals were supplemented with urea differences between sugarcane cultivars did occur for NDF consumption, but not for daily methane production. This suggest that variation in chemical composition of sugarcane did not affect bovine ruminal CH(4) emissions. Concentrate inclusion in animal diet increased digestible organic matter intake, improving the nutrient intake by animals, but did not reduce CH(4) production expressed as a percentage of gross energy intake.     

The protein and energy requirements of ducklings in the tropics

1. Protein and energy requirements of local and imported commercial strains of ducklings were determined under tropical conditions.

2. The results indicate a requirement for a diet with 240 g crude protein/kg, 9 g methionine plus cystine/kg and 12.97 MJ metabolisable energy/kg for maximum growth and food efficiency up to 8 weeks of age.

3. Though the imported commercial‐strain ducklings grew faster and utilised food more efficiently than the local strain, the general pattern of response indicated that optimum concentrations of nutrients were similar in the two strains.

4. The indicated nutrient contents are different from the recommended concentrations for ducklings in the temperate environment.